0-106/2007Ident. No. 822-103

Operating Instructions

Cable Testing and Diagnostic with theSystem PHG 70 TD PD / PHG 80 TD PD

BAUR Prüf- und Messtechnik GmbHRaiffeisenstrasse 8, A-6832 Sulz / Austria

Tel +43 / 55 22 / 49 41-0Fax +43 / 55 22 / 49 41-3

e-mail: headoffice@baur.atinternet: http://www.baur.at

0-2

0-3

For fast finding of important information the corresponding textpassages are marked with symbols (symbols not stated here areself-explaining).

More and special information concerning the respective subject areavailable from BAUR.

Important unit information!In any case, read carefully!

Important information text.

Observeinfo signs!

☞

Guide to this Operating Instruction

Copyright

© BAUR Prüf- und Messtechnik GmbH,A-6832 Sulz / AustriaAll rights reserved.No part of this publication may be reproduced, transmitted, storedin a data processing system or translated into another languagewithout the written permission of BAUR / Sulz, Austria.

In the interest of our customers we reserve the rights formodifications due to technical progress. Illustrations, descriptionsand delivery content are therefore not binding.

© Copyright by BAUR

This manual contains all information necessary for the correcthandling and use of the cable test and diagnostic systemPHG. Before using the system PHG, please read carefully thesoftware help and this Operating Instruction.

Preface

If you have any questions, please contact directly

BAUR Prüf- und Messtechnik GmbH, Raiffeisenstrasse 8A-6832 Sulz / Austria

or refer to your nearest BAUR representative.

Please read now andavoid damage and injury later!

- The cable test and diagnostic system PHG is built inaccordance with today's state of engineering and is safe tooperate. Individual components and the finished unit areinspected continually by our qualified staff within theframework of our Quality Assurance Provisions. Each unit issubjected to thorough testing prior to shipment.

Subject to modification!

Safety Precautions

Guide to this Operating Instruction, Copyright, Preface

0-4

Safety Precautions, Warranty

- It is imperative to every person who is involved with theinstallation, start-up, operation and maintenance to have readand understood the complete Operating Instruction.

- It is the responsibility of the customer to ensure that onlyauthorized persons may be allowed to use the systemPHG. Operators must notify immediately any changes to the unitthat detract from this safety.

- The cable test and diagnostic system PHG is only for theuse of testing and aging assessment of power cables andother electrical equipments. Any other or additional use isdeemed to be in contravention of the intended use. Themanufacturer shall not be liable for damage resulting from anysuch use. In such a case the risk shall be borne solely by theuser.

The user- is qualified and properly instructed and has the necessary

experience.- knows the relevant standards, accident prevention rules and

operating conditions.- is able to carry out the necessary operations and is aware of

the possible dangers involved.- must immediately inform his superior about any conditions of

the unit that could affect safety.

Before switching ON read the Section 2-5 ”Connect Ground”carefully. For the operation of the PHG the local security rulesand accident prevention regulations have tobe applied.

Safety Precautions, Continued

Only authorized personnel!

Use the PHG - Systemunit as directed!

At the customer's written request we undertake to repair orreplace at our discretion and as quickly as possible all parts thatbecome faulty or useless as the demonstrable result of poormaterial, faulty design or defective execution.We bear the costs for repairs and replaced parts, exclusivetransportation of the goods, packing and insurance.

The 12 months warranty time starts with delivery.We shall bear the costs of any faulty parts requiring replacement,but not the costs of transport to us and back to the customer, northe costs of packing and insurance! We shall not be liable for anydamage resulting from normal wear and tear, improper handling,non-observance of Operating Instructions and safety regulations.We shall also refuse to accept any liability if the customer carriesout repairs or changes to the unit himself or has others carry outthem!The warranty does not cover damage in transit, batteries, fuses andany readjustments in accordance with the Operating Instruction!We draw attention in addition to the "General Terms of Sales andDelivery" of

Warranty

12 months warranty time

BAUR Prüf- und Messtechnik GmbH, Raiffeisenstrasse 8A-6832 Sulz / Austria

0-5

Contents

Contents

1. System Information ........................................................................ 1-1

Overview ..................................................................................... 1-1

System overview......................................................................... 1-2

PHG connections ........................................................................ 1-3

Technical data ............................................................................. 1-4

Servicing / Maintenance .............................................................. 1-6

Operating elements on SCU ....................................................... 1-7

Connection set..............................................................................1-8

2. Cable Testing .................................................................................. 2-1

Overview ..................................................................................... 2-1

Testing cables using the PHG unit .............................................. 2-2

Programmable voltage waveforms.............................................. 2-3

Prepare Test Object .................................................................... 2-4

Earth connection ......................................................................... 2-5

Connecting High Voltage Test ..................................................... 2-6

Proceed High Voltage Test .......................................................... 2-7

Switching OFF of the system ...................................................... 2-8

Software ..................................................................................... 2-9

0-6

Contents, Continued

Contents, Continued

3. Dissipation factor measurement.................................................. .3-1

Overview ..................................................................................... 3-1

The ageing mechanisms of plastic insulated cables ................... 3-2

Dissipation factor measurement at 0,1 Hz .................................. 3-4

The dissipation factor measurement principle ............................. 3-5

How to carry out the dissipation factor measurement ................. 3-6

Assessment of the dissipation factor measurement values ......... 3-9

Limits and criterions for homopolymeric PE and XLPE cables .... 3-9

Prepare the Diagnostic Measurement ....................................... 3-10

Earth connection ....................................................................... 3-11

Connecting High Voltage Leads ................................................ 3-12

Perform a Diagnostic Test ......................................................... 3-14

Switching OFF of the system .................................................... 3-15

Software.................................................................................. 3-17S

4. Partial discharge measurement .................................................... 4-1

Design and Function ................................................................... 4-2

Principle of PD-location .............................................................. 4-5

Specific features of different types of cables ............................... 4-7

Connections ................................................................................ 4-9

Software ................................................................................... 4-11

- Program start-up ................................................................ 4-11

- Basic settings .................................................................... 4-13

- Set-up ................................................................................ 4-14

- Functions ........................................................................... 4-18

- Menu options ..................................................................... 4-26

References ............................................................................... 4-29

1-1

Topic Page

System overview 1-2

PHG connections 1-3

Technical data 1-4

Servicing / Maintenance 1-6

Operating elements on SCU 1-7Connection Set 1-8

This chapter describes following topics:

1. System InformationOverview

System Information

In this chapter you will find all relevant information for the systemPHG. More literature references you will find in the chapter 3-29 oron request.

Please read also the SOFTWARE HELP functions!

Start PHG Software and choose "Help" function.

1-2

Pos. Designation

Display

BAUR IPC

Safety Control Unit SCU

PC keyboard

PHG power unit

Cable drum rack KTG

Discharge Unit DU

Partial discharge

Legend

View"Version B"

System overview

System-overview

6

81

2

3

4

5

7

7

6

5

4

3

2

1

8

1-3

Pos. Designation

Protection ground connection

Fibre optic link connection forPHG 70 TD / PHG 80 TD-synchronization (option)

Fibre optic link connection RS232/1(generator control system)

Fibre optic link connection RS232/2(tan δ - measurement)

Connection to the DU

Connection for security circuit

Mains connection PHG 70 TD / PHG 80 TD

Connection for protective earthing (VSE)

Connection for CC1

Connection for IRG / CC1

PHG connections

PHG connections

10

11

12

12

13

14

15

16

17

18

10 11 12 13 14 15 16

191817

1-4

230 V (50/60 Hz),(200 ... 264 V) 230 V (50/60 Hz), (200...264 V)115 V (50/60 Hz), (100 ... 140 V) 115 V (50/60 Hz), (100...140 V)

sinewave 38 kVrms 0.1 Hz sinewave 57 kVrms 0.1 Hzsquarewave: 54 kV 0.1 Hz squarewave: 80 kV 0.1 HzDC: +/- 70 kV DC: +/- 80 kV

70 kV 10 mA 80 kV 1.8 mA50 kV 60 mA 50 kV 60 mA20 kV 90 mA 20 kV 90 mA

20 μF 20 μF- 1.1 μF3 μF 3 μF8 μF 8 μF

Sinewave, squarewave with defined slew-rate; DC-, DC+

0.01 Hz ... 1 Hz

RS 232 with fibre optic link

not condensing

working: 0° C ... +45° C, storage: - 20° C ... +60° C

English, German, French, Spanish, other languages on request

19", 14 U (483x623x775 mm)

approx. 160 kg

depending on version 250 - 400 kg

Technical Data

Power supplyOption

Nominal voltage

Max. output current DC

Maximum capacitive loadAt sinewave 0,1 Hz, 57kVrmsAt sinewave 0,1 Hz, 36kVrmsAt sinewave 0,1 Hz, 18kVrms

Voltage waveforms

Ffrequency

Serial interface

Relative humidity

Max. ambient temperature

Selectable languages

Power unit Dimensions

Weight

Weight of complete System

PHG 70 PHG 80Test System

Technical Data

1-5

Technical Data, Continued

Technical Data, Continued

Voltage range

Load range

Measuring range

Resolution

Accurancy

Industrial PC

Display

1 - 38 kVrms 1 - 57kVrms

>10 nF (500 pF, option) >10 nF (500 pF, option)

0.1 x 10-3 to 1000 x10-3 0.1 x 10-3 to 1000 x10-3

1 x 10-5 1 x 10-5

+ 1 % from measuring value + 1x10-4

BAUR IPC, MS Windows BAUR IPC, MS Windows

12.1 " TFT 12.1 " TFT

PHG 70 TD PHG 80 TDDissipation factormeasurement TD

1 - 38 kVrms 1 - 57 kVrms

7000 m at 87,5 m/us 10 - 7000 m

50 - 120 m/μs 50 - 120 m/μs

10 ns (100 Msamples) 10 ns (100 Msamples)

1 % of the cable length 1 % of the cable length

0,1 pC; 0,1 m 0,1 pC; 0,1 m

Graphics user interface Graphics user interface

BAUR IPC, MS Windows BAUR IPC, MS Windows

15.1"TFT 15.1"TFT

Voltage range

Range of cable length

Propagation rate

Sample rate

Accuracy of localisation

Resolution

Software

Industrial PC

Display

PGH 70 PD PGH 80 PD

Partial discharge level measurement with source localisation PD

1-6

Servicing / Maintenance

Servicing / Maintenance

All Service and maintenance operations must be done withthe PHG 70 TD / PHG 80 TD switched OFF and power supplydisconnected.Before any maintenance or servicing please comply with all safetyrules (see page 0-3).

Cleaning attention:Dirty sealing or terminations, shrinking tubes of high voltageconnecting leads, HV plugs must be carefully cleaned with thedelivered isopropanol impregnated cleaning towels to be releasedfrom humidity and dust.

1-7

Pos. Designation

Power supply switch with integrated fuse(up to 16 A load)

Pushbutton "READY TO SWITCH ON"

Pushbutton "HIGH VOLTAGE OFF"

green indicator lamp

red indicator lamp

"EMERGENCY OFF", lockable

Operating elements on SCU Safety Control Unit

16

Legend

17

18

19

21

20

Front panelSCU Safety Control Unit

1619

2021

17 18

Operating elements on SCU Safety Control Unit

1-8

The connection of the systems high voltage to the DUT variesstrongly, depending on the terminals of the DUT and the localreality. Especially for the diagnosis methods the reduction of partialdischarges at the connection is recommended. Following theattached Connection Set of the system and the variations for theconnection are described. The noted maximum voltage at everyvariation is the measured voltage without influence of partialdischarges to the diagnosis. Naturally this figure depends on thecondition in the field and therefore can only be a decision guidance.

Connection Set

Connection Set

The components

Plug MC 10

Terminal end for Plug MC 10

Spacer for mushrooms

Clamp connector

Mushroom connectors

Jack of HV-cable

Terminal of HV-cable (old system)

1-9

Connection Set

Variation A: up to approx. 35 kV rms

1-10

Variation B: up to approx. 35 kV rms

Connection Set

1-11

Variation C: up to approx. 35 kV rms

Connection Set

1-12

Variation D: up to approx. 35 kV rms

Connection Set

1-13

Variation of the mushroom connectors

Connection Set

1-14

Notes

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○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

2-1

Topic Page

Testing cables 2-2

Programmable voltage waveforms 2-3

Prepare Test Object 2-4

Earth connection 2-5

Connecting High Voltage Leads 2-6

Proceed High Voltage Test 2-7

Switching OFF of the system 2-8

Software 2-9

In this chapter you will find all relevant cable test information for thePHG System. More literature references and internationalstandards you will find in the chapter 4-29 or on request.

Please read also the SOFTWARE HELP functions!

Start PHG Software and choose "Help" function.

2. Cable Testing

Overview

Cable Testing

This chapter describes following topics:

PHG: Programmable H.V. GeneratorVLF: Very Low FrequencyPE/XLPE-cable: cable with synthetic insulation

of polyethylen (PE) or crosslinked polyethylen (XLPE)VSE: Virtual Protection Ground

Abbreviations

2-2

ApplicationTesting of cables

Replacement of oil-paper- and mass-impregnated cables withpolymeric cables makes it necessary to adopt a alternative cabletest method. The DC voltage test, which for some decades now hasbeen used to test paper insulated mass impregnated cables, hasproved itself unsuitable for testing polymeric cables.

On the one hand, serious defects are seldom detected. On theother, the DC voltage test can lead to long-term space charges onwater-tree damaged plastic insulated cables as a result of theprescribed high testing level during the testing period. When normalservice alternating voltage is then applied this can lead to a localexcess of PD-inception voltage, thereby initiating "electrical trees".This causes irreversible damage to the insulation, and a totalbreakdown then becomes a matter of time. Numerous cases ofdamage to plastic insulated cables following DC voltage testsconfirm this. For this reason, a new method of testing plasticinsulated cables has already been in use for some years now.

In practice, the voltage test with very low frequency (VLF), which isalso suitable for paper insulated mass impregnated cables, hasreplaced the DC voltage test. Besides, cable diagnostic has gainedwide acceptance. In the standards procedure, the 0.1 Hz testmethod was included in the European Standard and HarmonizationDocument CENELEC HD 620 S1 for plastic insulated cables andHD 621 S1 for paper insulated (PILC) cables, alternative to the DCvoltage test.

The pressure test with the PHG results in a go/no go determination:- Cable withstand/not withstand the voltage load during the testing

time.

Testing cables

Testing cables

Cable assessment

Test Requirements Test method

1. Voltage test on insulation (1, 2)1.1 a. c. test voltage 45 to 65 Hz

- test voltage (r.m.s.) 2 U0- test duration 60 min no breakdownalternatively:

1.2 a. c. test voltage 0,1 Hz- test voltage (r.m.s.) 3 U0- test duration 60 min no breakdown

2. Voltage test on sheath (3) no breakdownPE sheath: d. c. voltage 5 kVPVC sheath: d. c. voltage 3 kV

1) The test voltages and test durations are preferred values. They were specified with regard to the experience made in laboratories and under operating conditions in utility systems.

2) If the cable end is in a transformer or in a metal-clad switchgear, this test is subject to agreement between the customerand manufacturers of the transformer or metal-clad switchgear.

3) The test methods shall be chosen such that secondary faults, e.g. caused by the energy content of impulse waves, areavoided.

Extract of Test requirements in CENELEC HD 620 S1 part 5 section C (ident with the German norm DIN VDE 0276-620)Recommended tests after installation, if required

2-3

Programmable voltage waveforms

programmable steps1. . . 10

test voltage1 . . . 80 kV PHG 801 . . . 70 kV PHG 70

test time1 min . . . 6 h

programmable output voltage+80 kV PHG 80+70 kV PHG 70

programmable output voltage-80 kV PHG 80-70 kV PHG 70

Sinewave test voltageat 0.1 Hz:

Programmable step testfor all voltage waveforms:

Squarewave voltage at 0.1 Hzwith defined slew-rate:

programmable frequency0.01 . . . 1 Hz

max. output voltage3 . . . 57 kVeff PHG 803 . . . 38 kVeff PHG 70

Programmable test voltageand waveforms

The PHG produces, at a frequency of 0,01 up to 1 Hz, a sinewavetest voltage up to 57 kVrms, as well as a squarewave test voltageup to 57 kV / 80 kV peak. Thus 33 kV cables can also be tested upto 3xUo. Even on mass-impregnated cables the VLF (0,1 Hz) testvoltage is applicable.For DC testing the PHG offers a stabilized positive or negativeoutput voltage from 1 up to 57 kV / 80 kV e.g., for mass-impregnated paper cables.

programmable frequency0.01 . . . 1 Hz

max. output voltage1 . . . 80 kV PHG 801 . . . 57 kV PHG 70programmableslew-rate

Programmable voltage waveforms

Regulated DC test voltagewith positive or negative polarity:

2-4

- Isolate the test object, lock against reconnection and make surethat zero voltage condition exists.

- Insulate nearby items which are under voltageAll other hot parts (station switches, cable terminations, busbars etc.) besides the test object, must be secured from thetest object to avoid flashover and overvoltage stress.

- On multiphase systems connect all phases to the station groundexcept the one under test.

- If necessary clean the terminations.

Prepare Test Object

Prepare Test Object

2-5

Earth connection

Action Procedure

A Connect protective earth lead to station earth.

B Connect protective earth lead to earth terminal ofKTG cable drum rack. Take shortest distance ofcopper terminal. Protective earth lead must be asshort as possible!

C Equipotential lead (cross-section min. 25 mm2 /max. length = 10 m) to the next low-resistanceearth. If the copper cable is not connected apotential rise of the unit in case of breakdownscan be the result.

Earth connection

test object

A

Earth terminal of KTGcable drum rack:

protective earth cableyellow / green

station earth

C

earth

copper terminal

≥25 mm2

lmax= 10 m

Equipotentiallead

HV - plug - interlock

B

2-6

Action Procedure

A Connect the shield of the high voltage lead to thestation ground.

B Connect strand of the high voltage connectinglead to the strand of the test object.

C Insert H.V. plug into DU and tighten with nut.

D Place the external emergency switch (Option) at aneasy accessible place.Replace the short circuit jumper by the externalemergency plug.

E Connect power supply lead.

3

test object

station earth

shie

ld

high voltage lead

high voltage plug

Emergency off, externally(option)

Connecting High Voltage Leads

Connecting High Voltage Leads

DE

C

A

B

2-7

Action Procedure

A Switch ON the power supply switch (16) on theSCU

B Switch On the personal computer

C Start the PHG software

D Push the "READY TO SWITCH ON" pushbutton(17) on the SCU.The PHG is ready to switch on only when followinginterlocks are released:- the high voltage plug on the DU is connected

and the screwed plug is completely locked in- the emergency off switch on the SCU and the

external emergency switch (option) are notactivated

The green indicator lamp is switched OFF, thered indicator lamp is illuminated.

E Select the menu:"Manual test" or "Automatic test".

F Define test procedureTerms, explanatory diagrams for the symbols as wellthe Help functions can be selected with the ? button.

G Start the test procedureA red high voltage arrow signal will be displayed whichgives a feedback of the switched ON high voltage. ThePHG is now "IN OPERATION".

Proceed High Voltage Test

Proceed High Voltage Test

16 17

Before going into operation, local safety regulations and safetyprecautions for the protection against direct or indirect contactof live parts have to be met accordingly!

2-8

Switching OFF of the system

Action Procedure

A Stop the test procedure by the PC program "Stop"

B Push the high voltage OFF pushbutton (18)The PHG TD will return to the operation condition"READY FOR OPERATION"

The red indicator lamp is switched OFF, thegreen indicator lamp is illuminatedThe automatic discharge unit discharges theinternal capacitors and all connected highvoltage leads

C Discharge live parts, ground and short circuit allleads with optional discharge rod

Switching OFF of the system

The PHG System has an internal discharge unit but NOT asolid grounding device.Before releasing the safety precautions you must absolutelyonce again externally discharge, ground and short circuitnecessary all live parts with a ground rod.

18

2-9

PHG Software for dissipation factor measurement (TD)

Select HELP

Enter title andpress SEARCH

Summary of icons

PHG Software

2-10

PHG Icons

Manual Test

Within this MANUAL TEST menu the test voltage is enteredmanually. After switching ON the high voltage a minimum outputvoltage will be applied. (DC 1 kV, Sinusoidal 1 kV, Rectangular1 kV). In the field of VOLTAGE, FREQUENCY (Def.) the outputvoltage and frequency can be selected via mouse or keyboard.

PHG Software

2-11

SINUSOIDALFREQUENCY option 0.01 - 1.0 Hz

RECTANGULARFREQUENCY option 0.01 - 1.0 HzSelect Slew Rate (Rate of Voltage Rise) 10 - 100 kV/sec.The maximum slew rate is dependent from the capacitive load.If the slew rate is too high a comment will be displayed showing themaximum possible slew rate.

DC MINUSDC voltage output, negative polarity

DC PLUSDC voltage output, positive polarity

commands - TEST REPORTInput of required test report name

- MIN-MAX. VOLTAGEMIN. VOLTAGE = Preselected voltage valueMax. Voltage shows the maximum allowable voltage level.

- LOAD CAPACITYAfter starting the test procedure the system calculates thecapacity of the load. This value is needed to control the digitalcontroller device. This capacity value is displayed and is alsointeresting for the user application.

- PHG STATUSShows the acual generator status

- DWELL TIMEShows the time interval of output voltage burn down cycle.I CURRENT TRIP OFF'YES' If an overload switch-off in the test sample occurs the

generator will be switched OFF immediately.'NO' If an overload switch-off in the test sample occurs the burn

down cycle will be activated.- OIL TEMPERATURE

Shows the oil temperature in the power HV unit

PHG Software

2-12

Automatic Test

Define testsequence

Enter title for test sequence,parameter and confirm with 'OK'Factory settings: SAMPLE FILE is writeprotected

PHG Software

2-13

In the menu 'Automatic Test' you can test procedures. Within thefollowing voltage waveforms you can select:

SINUSOIDALSelect FREQUENCY 0.01 - 1.0 Hz

RECTANGULARSelect FREQUENCY 0.01 - 1.0 HzSelect SLEW RATE (Rate of Voltage Rise) 10 - 100 kV/sec. Themaximum SLEW RATE is dependent from the capacitive load. If theSLEW RATE is too high a comment will be displayed showing themaximum possible slew rate.

DC MINUSDC voltage output, negative polarity

DC PLUSDC voltage output, positive polarity

Automatic test

selectable voltage waveforms

Commands - TEST PROCEDUREWithin the window 'Test Procedure' you can select the appropriatecycle, by clicking the icon. All available test cycles are listed.Select appropriate test procedure. Overview of test parameterswill be displayed

- TEST REPORTInput of required test report name

- MIN-MAX. VOLTAGEMIN. VOLTAGE = Preselected voltage valueMAX. VOLTAGE shows the maximum allowable voltage level.

- LOAD CAPACITYAfter starting the test procedure the system calculates thecapacity of the load. This value is needed to control the digitalcontroller device. This is displayed and is also interesting for theuser application.

- STEPeach step you have to enter the voltage value and the testingtime. Maximum 10 steps are possible.

PHG Software

2-14

Notes

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3-1

Topic Page

The ageing mechanisms of plastic insulated cables 3-2

Dissipation factor measurement 3-4

The dissipation factor measurement principle 3-5

How to carry out the dissipation factor measurement 3-6

Assessment of the dissipation factor measurement values 3-9

Limits and criterions for homopolym. PE and XLPE cables 3-9

Prepare the Diagnostic Measurement 3-10

Earth connection 3-11

Connecting High Voltage Leads 3-12

Preform a Diagnostic Test 3-14

Switching OFF of the system 3-15

Software 3-17

In this chapter you will find all relevant information on cablediagnostic. More literature references or standards you will find inthe chapter 4-29 or on request.

Please read also the SOFTWARE HELP functions!

Start PHG Software and choose "Help" function.

Cable Diagnostic

This chapter describes following topics:

3. Cable Diagnostic

Overview

3-2

The ageing mechanisms of plastic insulated cables

The ageing mechanisms of plastic insulated materials

The experience gained over the past few years has shown thatwater-treeing is the major factor that determines the durability,especially of first-generation plastic insulated cables. Whileinstallation and mounting errors tend to be locally repairable, water-treeing occurs in areas where extension of the equipment life canonly be achieved through the replacement of sections or throughchemical refurbishment.

Water-treeing is an effect to the physical background which hasnot yet been fully explained despite various theories. Basically,water trees are channel-shaped structures which develop in theform of minute trees in the insulating material as a result ofmoisture and electrical fields emanating from defects. The electricalconditions prevalent in these water-trees, which are invisible to thenaked eye, differ from those in the healthy surrounding insulatingmaterial and this feature can be utilised for their measurement. Thedevelopment of water-trees takes place over some years. Water-trees can occur continuously in a cable without reducing itsfunctional capacity. The critical phase begins when the PD-inception field strength at the tips of a water-tree is exceeded.

3-3

The ageing mechanisms of plastic insulated cables

Figure 1: Water-treeing inplastic insulated cables

Electrical treeing is a process which, unlike water-treeing, takesplace only in areas of high field strength. It occurs very quickly, andis recognised by a series of partial discharges. The resulting hollowchannel-shaped structures are however not visible to the naked eye.The final breakdown of the insulation path under the influence ofelectrical trees is sometimes just a question of minutes or hours.

Unlike water-treeing, electrical treeing can be detected by PD-measurement.

Since long water-trees in the insulating material are likely to pavethe way for future electrical trees, they can also be used to measurethe ageing condition of a plastic insulated cable.

A method of diagnostic which does not give just a "go/no-go"appraisal, but which also evaluates the overall condition of the cableinsulation, must produce a measurement value which will correlatevery well with the "concentration" of long water-trees. Even thoughthis "insight" into the cable insulation can only give an integratedresult, significant similarities can be detected in most casesbetween the results of the measurements and the actual state of thecable using appropriate methods of diagnostics.

"bow-tie" trees

"vented" trees

Insulation

Core

Outer semiconducting layer

Inner semiconductor

The higher the dissipation factor of the insolation, the lower isdielectric stregth.

3-4

Dissipation factor measurement at 0,1 Hz sinusoidal voltage as ageingdiagnostics for plastic insulated cables and other electrical equipments

Dissipation factor measurement

Unlike tests which only give information about one local weak point,the most important function of diagnostic on a plastic insulatedcable is the evaluation of the overall condition, which is mainlydependent on the water-tree concentration.

The only way to evaluate water-trees in the cable in the frequencydomain is through dissipation factor measurement. Bad joints andterminations can be diagnosed through PD-measurement withalternative voltage.

For the past few years, very low frequency dissipation factormeasurement has continued to be used as the standardmeasurement technique for water-tree concentration and as acriterion for the medium term operating capacity of plastic insulatedcables. Reports on thousands of measurements carried out on siteby various power supply utilities are now available. These reportsconfirm the good correlation between measured values and degreeof degradation with lowered breakdown voltage.

In consideration of the various experiences and requirements of itsclients, as well as the results of scientific research, BAUR hasdeveloped a user-friendly system for dissipation factormeasurement, PHG the improved resolution and extendedmeasurement range of which can permit safe differentiationbetween new, slightly and badly aged cable systems.

3-5

During diagnostics using the PHG, the measuring voltage is derivedfrom a resistive voltage divider and current from the specimenunder test via a standard capacitor. The dissipation angle and thedissipation factor are calculated with the help of Fourier analysisand subsequent evaluation of the fundamental waveforms of bothmeasurement signals.

Since dissipation factor measurement on installed cables must becarried out with the test specimen earthed, all the leakage currentsbetween the high voltage and earthed parts would form part of themeasuremend value. An additional shielding connection, VSE, hastherefore been introduced to intercept all leakage currents fromsupply lines, surface leakage and insulation spacing in the testobject. The VSE is maintained at earth potential artificially andensures that this leakage current at the surface of the terminationsbypasses the capacitive current of the measurement.

The following conditions are essential for the measurement:

- no corona discharge at terminations of the test and measuringset-up.

- Suppression of the surface current on terminations and theinsulation leakage current of the connecting cable.

- Suppression of the dielectric loss in the connecting cables to thetest object.

Simple water-tree model, The dissipation factor measurement principle

The dissipation factor measurement principle

3-6

How to carry out the dissipation factor measurement

In practice, appropriate measures are taken:− Appropriate corona shields are used to eliminate the effects of

corona. These corona shields are attached to the cable socketson the terminations.

− Surface current on both terminations is conducted by guard ringsto VSE.

− In order to eliminate the effect of the high voltage cable on thetest specimen, the insulation leakage current of this cable ischannelled to VSE.

These measures have made the achievement of an accuracy of+1 x 10-4 for tan δ possible during on site diagnostic of installedcables.

How to carry out the dissipation factor measurement

The test object is isolated and discharged and then disconnected atboth ends from the sub-station, and the corona shields are fittedover the cable lugs. In the connecting sub-station, the corona shieldalso links the high voltage cable to the test generator PHG.A spacing of 20 cm from the surrounding earth is enough to preventcorona influence during full voltage testing.In the connecting high voltage station the corona hood will be usedfor the HV connection of the high voltage lead.

After connecting the earth line and the potential balance line, thecopper guard rings are fixed on the lower part of the cableterminations with velcro tape. There is direct contact between theguard ring and the VSE-Box at the connecting point, the guard ringat the cable termination in the opposite sub-station is indirectlyconnected through a spare phase. The screen of the high voltagecable leading to the test generator is similarly connected to theVSE-Box (Figure 8).

Very clean terminations with long creepage paths may not requireguard rings. However, it is not totally impossible that surfacecurrent may affect the measurement results due to the absence ofguard rings.

The recording of the dissipation factor values at different voltagelevels takes just a few minutes. At relatively low diagnostic voltagelevels up to about 2 U0, damaging of sound cable sections, whichshortens service life, is impossible.

3-7

How to carry out the dissipation factor measurement

Figure 5: Wiring in theconnecting sub-station

1. High voltage connecting line2. Connecting line cable screen / VSE-Box3. Earth line to the test object4. Guard ring connection in the opposite sub-station5. Return wire from the opposite sub-station6. VSE box

4

3

2

15

6

3-8

How to carry out the dissipation factor measurement

Figure 6: Corona shield andguard ring arrangement in theopposite sub-station.

7. Guard ring connection to thespare phase

8. Flexible VSE conductorconnected to the bottom of thesealing end

Figure 7: VSE-Box connection

1

23

4

5

78

The VSE conductor 7 should not have contact with the sheath orground of the cable!

1. High voltage connecting line2. Connecting line cable screen /

VSE-Box3. Earth line to the test object4. Guard ring connection in the

opposite sub-station5. Return wire from the opposite

sub-station6. VSE box

3-9

For some years now, it has been possible to calibrate the 0.1 Hzdissipation factor measurement on a very stable calibrationstandard, the absolute value of which is known to better than+ 2 x 10-5. With this standard BAUR offers the possibility of goingbeyond simply making comparison measurements to provide itsclients with real absolute measurements.

The only important factors to take into account when makingan assessment are the change of dissipation factor since thetest object was new and the voltage dependency of thedissipation factor.

The absolute maximum permissible value, at which operation-inhibiting damage is bound to occur, depends on the composition ofthe cable’s insulation material. This also varies from cable to cable.Therefore, the measured values should, if possible, always beconsidered in comparison with the tan δ value of a new cable. Thetypical dissipation factor absolute values of new homopolymeric PEand XLPE cables lay between 1 x 10-4 up to 2 x 10-4 . Copolymercables have much higher dissipation factor absolute values.Especially on new copolymere insulated cables the dissipationfactor might be highly frequency dependent.

* tan δ (2xUo) < 1,2×10-3 and* tan δ (2xUo) - tan δ (Uo) < 0,6×10-3

** tan δ (2xUo) > 2,2×10-3 or** tan δ (2xUo) - tan δ (Uo) > 1×10-3

* To secure the detection of local defects in the insulation an additio-nal high voltage withstand test with 3 Uo is recommended.

** Immediate replacement of cable or cable section isrecommended.

Please look carefully for a corona free measuring connectionand a correct connection of the virtual ground to avoidleakage current on the surface of terminations. If these criteriaare not fully attended, misinterpretation of the test results arepossible.

Assessment of the dissipation factor measurement values

Assessment of the dissipation factor measurement values

Limits and criterions for homopolymeric PE and XLPE cables

}}cable not fully penetrated

with water trees

cable with very highoperating risk

Caution!

3-10

- Isolate the test object, lock against reconnecting and make surethat zero voltage condition exists.

- Insulate nearby items which are under voltage.It has to be ensured, that the application of the diagnosticvoltage does not lead to flashovers to other nearby items ofthe cable station which are in service.

- On multiphase systems connect all phases to the station groundexcept the one under diagnostic.

It is known that the dissipation factor is highly temperaturedependent. Therefore it is recommended not to perform suchdiagnostic test during high load conditions. Wait until thetemperature reaches ambient conditions.

Prepare the Diagnostic Measurement

Prepare the Diagnostic Measurement

3-11

Action Procedure

A Connect protective earth lead to station earth.

B Connect protective earth lead to earth terminal ofKTG cable drum rack. Take shortest distance ofcopper terminal. Protective earth lead must be asshort as possible!

C Equipotential lead (cross-section min. 25 mm2 /max. length = 10 m) to the next low-resistanceearth. If the copper cable is not connected apotential rise of the unit in case of breakdownscan be the result.

Earth connection

Earth connection

test object

A

Earth terminal of KTGcable drum rack:

protective earth cableyellow / green

station earth

earth

copper terminal

≥25 mm2

lmax= 10 m

Equipotentiallead

HV - plug - interlock

B

C

3-12

Action Procedure

A Disconnect the strand to be diagnosed fromstation on both ends.

B Connect the guard ring with braided shield aroundthe bottom of the sealing ends.Caution:• The connection of the guard rings may not

produce corona or partial discharges.• The guard must not have any contact with

ground!• If necessary clean the terminations.

C Connect the guard lead with the VSE Box.Connect the other guard ring at the far end of thetested cable over spare phase for the returnleakage current (Fig. 5 / page 3-9 and Fig. 6 /page 3-10).

Connecting High Voltage Leads

Connecting High Voltage Leads

test object

Emergency off, externally(option)

high voltage plug

high voltage load

shield (VSE)

guardguar

d

3isolated phase

VSE box

F

H

F

C

E

B

D

B

FC

return line

3-13

Action Procedure

D Ground the VSE ground terminal with a contactclamp of the ground lead (yellow/green)(Fig. 7, page 3-10)

E Connect the shield of the high voltage connectinglead to the VSE box (Fig. 7, page 3-10)

F Place on corona hood at the far end of the testedcable and placeon corona hood with the highvoltage test lead on the strand to be tested.Caution:Be aware that all adjacent parts have a minimumHV distance.

G Place the external emergency OFF switch (option)at a convenient place and connect it instead of theshort circuit jumper.

H Connect power supply.

Connecting High Voltage Leads

3-14

Action Procedure

A Switch ON the power supply switch (16) on theSCU

B Switch On the personal computer

C Start the PHG software

D Push the "READY TO SWITCH ON" pushbutton(17) on the SCU.The PHG is ready to switch on only when followinginterlocks are released:- the high voltage plug on the DU must beconnected and the screwed plug is completely

locked in- the emergency off switch on the SCU and the

external emergency off unit (option) are notactivated

The green indicator lamp is switched OFF, thered indicator lamp is illuminated.

E Select the menu:"Dissipation factor measurement0.1 Hz sine wave".

F Diagnostic procedureTerms, explanatory diagrams for the symbols as wellthe Help functions can be selected with the ? button.

G "Start" DiagnosisA high voltage arrow signal is displayed which gives afeedback of the high voltage switched ON. ThePHG TD is "IN OPERATION".

Perform a Diagnostic Test

Perform a Diagnostic Test

16 17

Before going into operation, local safety regulations and safetyprecautions for the protection against direct or indirect contactof live parts have to be met accordingly!

3-15

Switching OFF of the system

Action Procedure

A Stop the test procedure by the PC program STOP

B Push the high voltage button (18) OFFThe PHG TD will return to the status "READY FOROPERATION"

The red indicator lamp is switched OFF, thegreen indicator turns ONThe automatic discharge unit will discharge theinternal capacitors and all connected highvoltage lines

C Discharge all hot lines, ground and short circuit allleads

Switching OFF of the system

18

The PHG System has an internal discharge unit but not a solidgrounding device.Before releasing the safety precautions you must absolutelyonce again externally discharge, ground and short circuit ifnecessary all live parts with a ground rod.

3-16

Notizen

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3-17

Software

The PHG software controls the programmable High Voltage Gene-rator and the Tan-Delta loss factor measuring system. The PHGsoftware enables fully automatic voltage tests and Tan-Deltadiagnostic measurements. This programe offers optimum supportfor evaluation and documentation of measuring results.

PHG TD Software Tan-Delta Diagnostic

Introduction

Correct connection of the test sample (see 'Help' 'Information').First enter data in 'Description'.Fill in the relevant date, select the 'diagnostic' procedure and'evaluation' and then enter 'phase voltage Uo'.The display for 'max. voltage' indicates the maximum test voltageduring this diagnostic process. Check the entered data and thenstart the process with 'OK'. The next screen displays 'StartDiagnostic'. This screen informs about programe and status ofdiagnostic process. Start the PHG system by activating button 'StartDiagnostic'. The different graphic display modes can be selectedduring and after diagnostic process (see 'Help' 'Icons andsymbols').

Description

The description is used as data base and definition of the diagnosticprograme and evaluation. Frequently used data and definitions arestored in 'copy layout'. After recall of 'copy layout' in 'description', thenew data can be entered. Delete the name 'copy layout' and fill inthe new title. Confirm with 'OK'.As soon as a new title is entered, the system will store itautomatically as new file.

Description 'copy layout'

3-18

Software

A new title or recall and correction of stored title results inoverwriting of the original title. The title file can be deleted if the titlename is cleared and confirmed with 'OK'.

See 'Description Tan-Delta Diagnostic'

Description title

Display of actual phasePhase

After start up, the system measures the load capacity of the testsample.

Load

Set'Set voltage' = pre-set value of voltage step

Max. voltage'max. voltage' indicates the maximum voltage level applied duringthe diagnostic process. For calculation of maximum voltage levelthe selected diagnostic process is used.

Set / max. voltage

Step 1: 1 * UoStep 2: 2 * UoStep 3 3 * Uo

Voltage Phase/N phase against neutral Uo= 6 kVMax. voltage = 18 kV

Example Diagnostic process

Actual Tan-Delta ValueTan-Delta

Displays the actual and the total number of measurements of thisstep

Process

Actual average valueAverage

Actual standard deviationSTD Dev.

see 'Help' 'Evaluation Tan-Delta Diagnostic'Evaluation

Each of these files has it`s own description and it`s own voltageindication. The PHG TD PC version has only one description andone phase voltage Uo for all phases.

3-19

- enter new title- enter phase number 1 or 3- enter phase voltage Uo (check and change old data for Uo)

Correct input values for phase voltage Uo are necessary to get validtan-delta evaluation diagrams.

- confirm with 'OK'- quit the now displayed screen 'PHG - Start Diagnostic' with 'exit'.

Description for creating new files basedon old VLF files

Loading files

By activating icon 'load file' followed by selecting and activating'load old VLF files' the screen for selection of old VLF files isopened.

The sequence of loading is only important insofar as the last loadedVLF file is stored in 'description' can be completed or modified.

Now a file converted from old VLF files can be printed out andstored as a new diagnostic file.

Loading VLF files

Software

3-20

Software

The filing system can be used to organize the stored dataFiling

Description PHG Tan-Delta Diagnostic

Stored data can be identified using the title and loaded using thetitle of data

Title

Up to one A4 page additional comments can be storedComment

Data file in MS DOS format xxxxxxxx.datTest file name

Statement of the path in the MS DOS formatPath

'no'Test results will not be stored

'yes'Measuring test results are stored after the test procedure.

'Yes' (with sinusoidal data)Measuring results and the data of current and voltage curve arestored. For the sinusoidal data you have to enter it`s own file name.

xxxxx000.sinfor 000 an automatic increased number will be selected andentered.

Automatic storage

3-21

- General Input Fields

CompanyLocationOperator

- Cable Data

- Phase1 Phase: Test procedure for the diagnostic for one phase will bestarted.3 Phase: Test procedure for the diagnostic for three phases will bestarted. Automatic sequence will be L1, L2, L3. The sequence canbe changed at any time with 'Start Test Procedure'.

After pushing the button 'more cable data' a new window will allowto enter more specific cable or test sample data. 15 different fieldsare available, which also are printed in the report.

General

Software

3-22

Software

Up to 10 test procedures can be defined. Open description. Selectthe subtopic diagnostic format by clicking the window 'sample 1'.The window 'diagnostic procedure' will be displayed. You canoverwrite the text 'sample 1' using a new diagnostic format name.To delete the diagnostic procedure format you delete the descriptionof the procedure. After selecting a new format you can enter newlisted parameters.

- StepsEnter the number of steps. Up to 7 steps can be defined

- FactorStep Voltage = Factor x Phase to ground voltage Uo must bedefined

- NumberPlease enter the number of Tan-Delta tests to be measured perstep

- DurationAfter the input of number of steps the system calculates thenecessary testing time. If you increase this time the system willfinish the number of selected tests, the remaining time the stepvoltage test will continue.

Define Programme

PHG TD - Programme Sequence

3-23

- IntervalIf the selected total time is higher than two times the needed timefor the test procedure, a new window will be displayed where youcan enter the 'Interval'.

example:Step 1 1 * UoNumber 8Duration 10 min.Interval 2

Interval 1:- 8 Tan-Delta Test (2 min.)- for 6 min. the step voltage will remain for the test

Interval 2- 8 Tan-Delta Test (2 min.)- Test finished

Software

3-24

Software

Discontinue criterion atthe step voltage test

Syntax:'s' ... Step'd' ... Difference of Tan-Delta between two test voltage intervals'>' '-' ... Allowed operators

After the letter 's' the step number is entered. All the step numbersare equal or smaller than the actual step number.Afer the letter 'd' the letter 's' and the step number must be entered.The Tan-Delta criterion is entered with the letter [E-3] followed by adecimal point. A criterion will be finalized by a comma ','.The distance, the number of blanks between the operators, thevalue of criterion and the final character are not important.Within a 'ds' term only the actual step is tested.Up to maximum 5 discontinue criteria for already measured valuescan be selected. Up to a maximum 50 characters for thediscontinue criteria can be selected.

If the discontinue criterion is reached, the Tan-Delta test will bediscontinued before the next step of test will be started. All thediscontinue criteria are related to the already measured Tan-Deltaand the gradient of step values.On an interval test the limits are calculated after each package oftest result and if necessary the test will be discontinued.

Step 1: S1 > 3.5If the Tan-Delta value at step 1 is higher than 1 * 10 E-3 the testcycle will stop.

Step 2: S2 - S 1 > 0.4If the difference of Tan-Delta value between step 2 and step 1 ishigher than 0.4 * 10 E-3 the test cycle will stop.

Step 3: ds > 0.5If the difference of Tan-Delta value between two intervals is higherthan 0.5 * 10 E-3 the test cycle will stop.

s2-s1 > 0.6, ds2 > 0.4, s2 > 1.2

Time event of a discontinue criterion

Example 2

Example 3

Example 4

_Example 1

3-25

'(' , ')' ... Tan-Delta Values in brackets'-' , '+' ... Operators for adding and subtracting'<', '>' ... Operators for comparison'A' , 'a' ... Operators for a logic operation 'and''O' , 'o' ... Operators for a logic operation 'or''G' , 'g' ... Limited value

Example for an input of a creation:

Limited Value G1 TD(2xUo)-TD(Uo) < 0.6Limited Value G2 TD(2xUo) < 1.2Limited Value G3 TD(2xUo)-TD(Uo) > 1.0Limited Value G4 TD(2xUo) > 2.2Limited Value G5 TD(1.5xUo) > 2.0Limited Value G6 G3 a G4 a G5Limited Value G7 G1 o G2

The word 'TD for description Tan-Delta is optional. Following anopening bracket '(' a multiplying factor and the rated Voltage '*Uo'must follow. The multiplying factor is entered either with or without adecimal point. If the factor becomes 1 or 1.0 this value can beomitted.Max 3 operators can be used to define the limiting values forevaluation. The operator for comparisons like '<' or '>' is comparingthe linked Tan-Delta value at defined limit [E-3] either with theoperators plus '+' or minus '-' linked with defined Tan-Deltalimits [E-3].

Totally 9 limiting values with an adequate priority can be entered.The highest priority '1' and the lowest priority '9'. If more than onecriterion is fulfilled the priority level will then decide the criterion.As result of the diagnostic test the limiting values and the criteriaare calculated with different assessment strings or customer text forfurther decisions will be displayed.

The least limiting value will be the criterion calculated and displayedif both operators '<' or '>' are used and their criteria are not fulfilled.The assessment string should not be longer than 100 digits. Theassessment string with the highest priority will be used for thereport.

Key Functions (Syntax)

PHG TD - Evaluation Tan-Delta Diagnostic

Software

3-26

Software

Short descriptions of further functions

Switch to PHG Automatic Test

Switch to Manual PHG - HV Test

Load diagnostic and sinusoidal data

Store diagnostic and sinusoidal data

Overview Tan-Delta measurement

Tan-Delta measuring

Graphic: Tan-Delta / HV

Graphic: Tan-Delta / measurement number

Graphic: Sinusoidal Voltage and Current

Print report results

Delete actual measurement results

Help for the Tan-Delta test

3-27

Notes

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4-1

This chapter describes followeing topics:

4. Partial discharge measurement

Overview

In this chapter you will find all relevant information on partialdischarege measurement with PHG. More literature references orstandards you will find in the chapter 4-30 or on request.

Please read also the SOFTWARE HELP functions!

Start PHG Software and choose "Help" function.

Partial discharge measurement

Topic page

Design and Function 4-2

Principle of PD-location 4-4

Specific features of different types of cables 4-8

Connections 4-10

Software 4-12

- PHG PD Sorftware Partial discharge measurementProgram start-up 4-12

- Basic settings 4-14

- Set-up 4-15

- Functions 4-19

- Menu options 4-27

References 4-30

4-2

Design and Function

Design and Function

The PD-measurement system consists of the following systemcomponents:

- VLF generator PHG 70, PHG 80

- Discharge unit DU

- Interference suppression filter NF

The interference suppression filter is used for suppression ofinterfering signals arising from high voltage generation. As a result,a sensible PD-measurement is guaranteed.

- Coupling unit CU

The coupling unit is directly connected with the cable head at thecable station. There the PD-pulses are coupled out capacitively viaa coupling quadripole.

Design

2

- BNC line on hand-operated cable drum

The BNC line is used for the transmission of measured signalsfrom the coupling unit to the PD-measurement unit.

3

1

1

2

1 - ground connections

2 - High voltage electrode

3 - signal output

4-3

Design and Function

Calibrator

3

1- Button

Button to change calibration charge

2 -Button

Press to turn calibrator on

Press to change calibration chargepolarity

Press 3 seconds to turn calibrator off

3 - Display

actual calibration charge is displayed

4 -Connector

To connect with coupling capacitorduring calibration

2

4

1

4-4

Principle of PD-location

Principle of PD-location

The PD-measurements with source location in the system PHG PDworks on the principle of the echometry. This means that for theevaluation the fact is used that the PD-pulses generated in the PD-fault point are propagated as transient waves on the cable line andreflected from the ends.

From the different pulse propagation time the fault distance can bedetermined. The Figures below shows the principle.

The Generator is connectet to the DUT and to the Couplingcapacitor.

The Quadripole of the Coupling Capacitor is connected to the PDmeasurement system.

The Quadripole and the DUT have to be grounded proper.

A PD impulse is moving from the source of PD in both directions,one to the near end of the cable, one to the far end of the cable.

4-5

Principle of PD-location

The impulse towards the far end of the cable is reflected back

The impulse to the near end is reflected back and the PDmeasuring system is triggered

During their way both impulses are damped.

4-6

The impulse reflected on the far end arrived on the near and isreflected back towards the far end again.

This can be seen in the PD Detector display.

The Impulse reflected on the near end arrives on the far end andis reflected towards the near end again.

4-7

The impulse reflected on the near end and reflected on the far endarrives on the near end a second time.This can be seen in the PDDetector display.

With this informations the location of the PD can becalculated:

time between impulse 1 and impulse 2 * pulse velocity

Length from far end to source of PD = ——————————————

2

Length from near end to source of PD = cable length - Lengthfrom far end to source of PD

4-8

Specific features of different types of cablesPD Diagnostics is general

PD Diagnostics has been a well proven method for non-destructivejudgement of insulation behavior. From laboratory testing PDmeasurement is well-known as a routine test. The PD levelsrequired there are dependent on the product. In case of mediumand high voltage cables the levels are in the range of some pC.

For on-site testing the required levels are different. For on-sitetesting the exact level itself is less important compared to thelocalisation of the PD source. The PD level has to be known onlywithin a range. The PD pulses are subject to the damping of thecable. Therefore the level to be measured is dependent on thedistance of the PD source. For PD source location only the timedelay between the first and the reflected pulse is important.

In most cases the PD source is not located in the cable insulationitself, but in the accessories. Would the PD source be locatedwithin the cable insulation, this would lead to a breakdown withinshortest time. Practical measurement prooved that most of the PDsources are located in the joints. PD sources outside the joints arerare and then mostly defects on the sheath.

Thus leads to the fact that for on-site PD diagnosis PD levels in therange of some 100 pC are relevant only. Most important is theknowledge of the location of the PD source.

Experience on plastic cables

Numerous practical measurements worldwide showed that PDlocation at plastic cables (means in the joints of those) wereperforming successfully [1][2][3][4]. [2] describes the location of 6defective, out of total 36 joints. The reason was a mounting defectduring installation. [3] describes the investigation of two out of the 6defective joints in laboratory. Reason for the measurement was ajoint defect 6 months after installation. The results of the on-siteand the laboratory PD measurements are equivalent.

A visual examination of a faulty joint showed that this joint, having1.6 nC would have led to a defect rather soon.

Table 1 presents the results of this on-site measurement. Theresults were prooven by laboratory measurements on the jointsbeing removed from the grid.

4-9

Specific features of different types of cables

Position Joint1 Joint2 Joint3 Joint4

118m 541m 780m 1150m

L1 126pC 1.2nC 260pC

L2 428pC

L3 1.6nC 472pC 604pC

Table 1: Summary of the on-site measurement on a 30 kV systemat 1.7 U0

A lot of measurements were performed on other plastic cables(PE/XLPE and EPR) with the same success.

Experience on paper mass cables

The PD measurement on paper mass cables is the same as onplastic cables regarding the measurement technique. The mostimportant difference exists in the interpretation of the results.From its design a paper mass cable has a lot of PD within itsinsulation. In contradiction to a plastic cable this is not harmfull tothe insulation. The voids in the insulation open and closefrequently due to the thermal expansion and viscosity of theinsulation mass. The harmlessness of this is prooven by papermass cables showing nC of PD but being in operation since morethan 80 years. This background PD level of the cable itselfdepends on type, manufacturer, manufacturing year and conditionof the cable and ranges between some 10 pC and some nCwithout being risky to the cable.

As already described for the plastic cables the PD measurement atpaper mass cables is done in order to locate defects in joints andterminations. In some cases defects of the sheath (corrosion of thelead sheath) were detected.

In comparison to plastic cables, the paper mass cables never wereroutine PD tested at the manufacturer. Therefore the interpretationof the results and the operation risk are much more difficultcompared to plastic cables. Only comparison between the cablesof different phases and of same type and manufacturing yearenable an interpretation.Additional to that the measurement itself ismore difficult. Many of the (non-risky) discharges in the cable arerecorded of the measurement system. Each impulse shows theequivalent position of the source. This leads to a distribution ofmany pulses all over the cable length. In order to locate a defectwhich shows up with a PD level higher than this „backgroundnoise“, many recordings are required. Measurement systems withautomatic position recognition are to be favored.

Practical experience of the authors in Germany, Austria, Italy,Russia, Ukrainia and other countries have shown, that despite theabove described difficulties a reliable identification of PD sourceswas possible. Even sheath defects could be identified. Additionalto that lead corrosion at railway crossings and river crossings weredetected. Therefore PD location and measurement on paper masscables is also recommended in order to increase the reliability ofthe grid.

4-10

Connections

Connecting for PD DiagnosisPreparation of the DUTDisconnect all poles of the DUT, prevent reclosing, and check de-energisation. Neighbouring parts under voltage must be insulated.Check that the test voltage cannot lead to flashovers toneighbouring parts under voltage. In a three- or more-phase-system ground all conductors except the phase under test.

Connecting of safety earthWith the included safety-earth-line (yellow-green) connect thetesters safety-earth-connector to the station earth. Connect thestation earth to the ground connector of the coupling capacitor.Ensure good connection of the DUT cable steath to ground onboth ends of the DUT.

Connection of the high voltage lineThe sheath connector of the high voltage cable of the tester has tobe connected to the grounded sheath of the DUT. The high voltageconnector has to be connected to the Coupling capacitor via theincluded resistor. Connect the inner conductor of the DUT to thecoupling capacitor via the included unshielded HV cable.

Connection of the signal lineConnect the signal line (black coax-cable with BNC plugs) to thesignal output of the coupling capacitor and on the other side to thePD measuring system (Plug named „RPA1“).

1- VLF Generator

2 - Partial discharge measuring system

3 - Coupling capacitor

1

2

3

4-11

connenctions

Please ensure that adequate precautions and general safetyinstruction are followed

1 - connect groundconnectors of couplingcapacitor to ground.

2 - screw included resistorto coupling capacitor.Connect HV cable fromgenerator to resistor,

3 - connect couplingcapacitor with DUT viaunshielded cable

1

2

3

Connect the black BNCmeasuring cable to thecoupling capacitor and tothe measuring system likeshown.

4-12

PHG PD Sorftware Partial discharge measurement, Program start-up

The Partial Discharge Measurement program is started from thePHG control program. This is done by selecting "Partial DischargeMeasurement" from the main menu.

The screen then appears as shown in the following figure. When theprogram starts up, the last used parameters and measurement dataare loaded and displayed. The automatic search routine thenchecks that a partial discharge measurement unit is attached andready.

Following successful initialization of the unit, the set-up settings forthe unit are loaded and any modifications to values for e.g. Position,Zoom, Gain, Cable Length and Propagation Velocity are displayed.The screen is divided into several areas. The function buttons onthe bottom edge of the screen allow quick access to the mostimportant functions. These functions are also available from themenu at the top of the screen. The menu bar also contains themore seldom used functions and options.The status indicator can be seen beneath the menu. The "RPA"LED indicates whether the coupling unit is connected or not. Greenor white lights mean normal operation. The red "ERR" light signalsan interruption in the transmission of data between the unit and thePC or errors in the data exchange between the PHG voltagemonitoring software and the PD measurement software. The "RXD"and "TXD" lights on the right hand edge are red if data is beingexchanged over the serial interface.

PHG PD Software Partial discharge measurementProgramm start - up

The software can also be used for offline-evaluation of themeasurements. Install the Software on a desktop PC runningWindows 98(TM Zeichen in Word einfügen) or Windows 2000(TMZeichen in Word einfügen) from the CD. Ensure, that the online-mode is deactivated on the office-PC. After doing measurementscopy all the recorded files with extension <.DSO> and make aReplay on your office PC like described later.In addition you shouldbackup all your measurements on printed on paper and/or backupthe recorded files on you office PC or a floppy disk. Archiving themeasurements only on the BAUR system PC is not recommendedbecause the system may be exposed to heavy duty environmentalconditions such as very high/low temperatures and mechanicalshock. All components, also the PC, are designed for this heavyduty condition but a failure of e.g. the inbuilt harddisk could destroyall the data saved on the PC.

4-13

Program start-up

The graphical interface shows this using two x-y plots. On the lefthand side is the DSO (Digital Storage Oscilloscope) (1). Thisdisplays the graphs transmitted from the unit against time. The y-axis shows the amplitude of the input signal at the preamplifier inmillivolts. The x-axis has a display range from a minimum of 2μs toa maximum of 80μs. With an A/D sampling interval of 10ns, thiscorresponds to between 200 to 8000 transmitted values. Underthese graphs there is an area which displays the current section ofthe window in relation to the maximum possible total data period(80μs) (2). The cursor positions are always shown there.

The associated graphs are shown on the right hand side. At thepresent time the graph is in the form of a correlation frequency plotagainst the cable length. Beneath these, you can position manuallymarkers for e.g. couplings or cable ends.

In the middle of the screen there is line of several control windowsfor the parameter settings of the unit and the software (3). Any ofthese values can be modified by the user. Each one of these isdealt with in more detail later.

The area above the function buttons is used to display the currentcalculated values for cursor positions, PD value or voltage (4). Themost important basic settings and all the set-up options areexplained in the next chapter.

1

23

4

4-14

Basic settings

Basic settings

After starting the program you can choose between two differentmodes of operation.

(a) Online measurement for testing the cable and

(b) Offline - data exchange.

For online measurement, a connection to the PD measurement unitvia a serial interface is set up and all the preparations such asconnection of the coupling unit and safety precautions arecompleted. To start continuous data transmission you must selectRUN mode. The F1 key can be used to move between the twomodes (see the chapter on functions). In this mode the curves inthe DSO graph representing the transmission velocity and thetrigger mode are updated as quickly as possible.

For offline data evaluation, no unit is to be connected as otherwiseseveral important functions e.g. Replay, are not available. With nounit connected the software is always in HOLD mode. The RUNmode cannot be activated offline (no serial connection).

Basic settings

Connecting the calibrator

No high voltage must be applied to the DUT during calibration!Switch off the generator and press the emergency-off button toprevent switching on high voltage by mistake!

For the calibration process use the included calibrator and connectit to the coupling capacitor high voltage electrode and to thecoupling capacitor ground connector.

Begin calibration with low Level (e.g.0.1 nC) for maximumsensitivity and increase level if necessary.

4-15

Set-up

The value in Position determines the displacement of the x-axis inrelation to the trigger point. The x-axis has its origin exactly at thetrigger point. The pre-trigger zone is set within the unit as 1μs. Thiscorresponds to a Position value of 0μs. The Position value changesthis pre-trigger zone in RUN mode and only the displayed area andnot the original data in HOLD mode or Offline. Position and Zoom inHOLD mode are automatically adjusted with respect to one anotherso that no overlapping can occur.

Set-up

Position

Changing the Position valueresults in displacement of the xaxis, at position 0μs the x-axisstarts at -1.0μs

Range markings; in HOLD orOffline modes a light grey barindicates the selected section

4-16

Set-up

In RUN mode these values determine the transmission time span(Range) in microseconds. The time base for the DSO graph shouldbe as small as possible in order to avoid unnecessarily long datatransmission times from the unit to the PC.

Due to the dispersion in the cable, a Range some 10-20% greateris chosen to ensure that all of the reflected signal can be seen. Thevalue selected for this setting must always be a multiple of 2μs. Themaximum value is 80μs.

The white bars under the DSO graph indicate the maximumpossible measurement range. The area marking is shown as apercentage of the whole area.

The area marking for Position and Range (Zoom) can have thefollowing appearance:

Range/Zoom

Position

a) Run Modus:

b) Hold Modus:

Zoom

Position Zoom

The values for Position and Zoom can be changed by shifting therange marking using the mouse. When the mouse pointer reachesthe range marking then either a hand appears for moving Positionor a double arrow for moving Range or Zoom. You can change thebar display by holding down the left mouse button.

Under the bars you can see the markers (grey, green and bluevertical lines) for the cursor positions in the DSO graph. The red "T"at the start remains where it is and indicates the trigger position.

It is to be noted that any area which you wish to see in HOLD modecan only show part of the originally measured data (i.e. Zoom =Range always applies). Therefore it is always better to choose aslightly bigger Range for measurement so that there is more scopefor using Zoom in the evaluation.

4-17

Set-up

The value for Gain determines the amplification of the highfrequency measurement signals. It is adjustable from 1 to 80000 (0- 98dB) in steps. The trigger threshold can be set between 0 and100%. These two fields are only accessible in RUN mode. If acyclic repeating triggered signal cannot be seen, this could be dueto several reasons:

- The amplification is too low, the trigger threshold is not reached;

- The trigger level is too high; if necessary choose a lower triggerthreshold for very weak signals

- No PD pulses are present; for very high gain values only noisesignals are triggered.

A suitable combination of gain and trigger values is best achievedusing the calibrator signal. The trigger level should ideally bebetween 50% and 90%. The gain should then be set so that thereflection from the cable end is clearly visible but the first triggerpulse is not too strongly overmodulated. A reflection position isessential in each case for a test to be carried out.

Gain (Amplification), Trigger level

On the right hand side near the field for the Gain value there is abutton which can be used to initiate an automatic gain adjustment.This causes the gain to be increased in stages and only when themeasuring signal exceeds the trigger threshold does the automaticgain adjustment stop.

Auto / Normal /Single Trigger Mode

Automatic gainadjustment

Trigger level in percent;no differentiation betweenpositive and negativesignals; Arrow is movedby mouse or kept belowabsolute value;

green arrow:trigger ok;

red arrow:no trigger, gain too low ortrigger level too high

4-18

On the right hand side near the Trigger Level field there is a buttonwhich can be used to set the trigger mode. The letter shownindicates the currently active mode. In Auto mode (A) the DSOgraph is continuously updated, irrespective of whether a triggerevent took place or not, in Normal mode (N) only triggered signalsare shown and Single mode (S) only shows a trigger event andimmediately afterwards switches into Hold mode.

Set-up

The values for the cable length and the propagation velocity, ifknown, can be entered directly into the fields. If only the cablelength is known then by calibration the value for the propagationvelocity can be automatically calculated.Calibration procedure:Connect the calibrator, to the coupling unit and enter a value in pC.This procedure can only be carried out in the non-live condition.Then set the gain and trigger level so that a continuous triggeredmeasurement signal is provided. In order to be able to carry out acalibration, the Range in the DSO graph is set so that the reflectionposition at the cable end is clearly visible. Now start the LOCfunction (see more in the chapter on functions) and a correlationfrequency distribution is displayed in the right hand graph whichideally shows a pronounced maximum at the reflection position. Bydouble clicking the mouse on this vertical red bar, a window opensin which a value for the exact length of the cable length can beentered. Closing the window with "Ok" displays the propagationvelocity, taking into account this value and the position of the redbar in the LOC graph.

Cable Length and Vc

(Propagation Velocity)

4-19

Functions

The function buttons on the bottom edge of the screen make all ofthe most important functions for cable fault location available. Thefollowing text describes these in more detail and the various waysin which the program can be used. Active functions have a darkgrey background.

Functions

Offline (no connection to unit) in HOLD mode

Offline with Replay function started

Online (serial communication) in RUN mode

Online in RUN mode and Scan function running

The program can show the DSO graph in two ways: The first is inRUN mode, in which there is a continuous flow of data between thePC and the unit and updating of the DSO graph takes placeaccording to the trigger mode. If the Trigger mode is set to Autothen all the transmitted DSO graphs are displayed. In the HOLDmode the DSO graph shows the last transmitted DSO graph or thelast one read from a file. The button label always shows the actionthat would be carried out if the button were to be pressed. In theRUN mode the button label is shown as "Hold DSO" and in theHOLD mode the button label is "Run DSO". If there is no serialconnection to a PD measurement unit then the program willautomatically be in HOLD mode. Switching to the RUN mode is notpermitted in these circumstances.

Run / Hold DSO(F1, Ctrl+U or Ctrl+O)

4-20

Functions

This is one of the most important functions for data evaluation. InOnline operation the Scan function is available and the Replayfunction is available in Offline operation. Both are dependent on oneanother.

The Scan function allows you to store the readings sequentially infiles which can then be reloaded and evaluated offline using theReplay function. Only the raw data and set-up information arestored in the DSO files (file ending *.dso) so that the use of harddisk space is minimised. Scan is then startedand the secondary window shown on the left appears. The valueentered in "Scan Directory" determines the directory where the filesin question are to be stored. This can be either entered manually orchosen from the existing directory structure using the "Browse"button. The file prefix determines the complete file name. The filename consists of the file prefix, a consecutive number and theending "dso". The maximum number of files that can be created bythe Scan procedure is limited by the value of the "Max FileNumber".This value can be between one and a thousand. When activated,the "Scan non triggered" option means that data not produced bythe triggering of a pulse is also stored in the files. This option issometimes of use if a very severely interrupted signal is presentand reliable triggering on dominant PD pulses is very difficult toachieve. Then in these circumstances, PD pulses and their echoesappear at random in the data stream and are stored for laterevaluation.The Cancel button is used to interrupt the Scan procedure and Okis used to start data storage. The file name previously savedappears over the DSO graph in blue letters. The Scan functionstops automatically after saving the previously set number of filesor by manual interruption from the user (Stop Scan).

Start / Stop Replay, Start / StopScan (F2, Ctrl+A)

4-21

Function

If the Replay function is started in Offline mode then a secondarywindow appears in which the scanned files must be selected. Makesure only those files are selected that were stored with the sametime "Range".

Choose the first file, press STRG + and click at the last file.

After the files have been chosen it is then up to the user whether ornot to look at each in detail, selecting each file for retention orrejection or accept all of the files. For the last option, the question"Single File Select?" should not be answered.

Selection

4-22

If the question is answered with a "Yes" then a new secondarywindow appears for the files to be pre-selected. The DSO graphshows the saved graph and the cursor positions. This information issaved with each file from Version 1.30.The file name is displayed beneath the DSO graph. The user cannow rename the displayed file and save it under another name(Save As), delete it (Delete), select (Select) or skip (Skip) the file.As above, the Replay process can be interrupted with "Cancel".Pressing the "All" button means that from the next file onwards allthe remaining files are automatically selected.

Each file chosen is automatically included in the calculation of theLOC display (correlation frequency distribution). The LOC display isupdated on the main screen after every calculation. The DSO graphshows the last selected file on the main screen.

Functions

4-23

This report is stored with each CFL file saved with the function"Save (F5)". Using the window shown below, the user is able toenter comments associated with the measurements that can beloaded again later and will appear on the page on every printout.

Functions

Ctrl+R

In Offline mode the saved files can be loaded and displayed on thescreen. These files can be scanned files (*.dso) or project files(*.cfl). The project files contain the set-up information for the unit aswell as the last displayed DSO graph, the report and the last faultlocation calculations from the LOC display.

Load (F4, Ctrl+L)

Saves the currently displayed data in a cfl file.Save (F5, Ctrl+S)

This function establishes the link to a PD measuring unit or breaksit. All the serial interfaces listed in the initialisation file are searched.Normally these are the ports COM1 and COM2. Depending on theparticular system configuration there could be up to 16 serialinterfaces.

Search / Offline (F6, Ctrl+E)

Report (F3, Ctrl + R) This report falls back on to the TD Description and makes acommon access to the cable line description possible (see 3-22)Additionally, you can fill in the position of joint and PD fault as wellas the PD inseption and extinction voltage.

4-24

Functions

Monitoring window display for the test generator voltage. Therequired voltage Uphg can be entered as the actual value in thiswindow. Further options can be accessed using the "Def" button.This brings up the secondary window PHG-PD parameter. Themaximum allowable voltage, the synchronization frequency and theparameters for the PDIV mode can be set in this window.

The PDIV mode automatically increases the test voltage up to thepreviously entered PDIV value (partial discharge value) in pC. Fromthis point the voltage is not further increased. Each increase involtage is maintained for a fixed number of time intervals. The sizeof the voltage increase and the starting voltage for this mode canbe varied.

PHG Control(F6, Ctrl+H)

After the start of the voltage control, the displays of the currentvoltage Uphg in the analogue display and the bar display in thePHG control window are constantly updated. The kV- and kV+buttons in the PHG control window are not available in the PDIVmode. These buttons are only accessible during manual setting ofthe voltage or after the PDIV mode has been automaticallyswitched off. Pressing the Start button starts the generator andshows the button against a red background. A red high voltagearrow near the Uphg display signals the presence of high voltage.

4-25

This function can be used to start or stop the automatic faultlocation calculation (LOC / Location). The calculation produces acorrelation frequency distribution which is shown in the graph onthe right. Every triggered graph from the DSOgraph is correlated with a reference pulse. This reference pulse hasbeen artificially "aged" i.e. the pulse has already taken into accountthe dispersion in the cable. After correlation the maxima are plottedin a three dimensional array. This produces frequency clusters fromthe measured times to the reflection positions. The accumulationsof these frequency clusters within a segment of the x-axis areshown with red vertical bars on the LOC graph. It should be notedthat the accumulations are only shown for those clusters that haveexceeded an adjustable pre-set level.The most pronounced maxima are directly translated into faultpositions and shown beneath the LOC graph as Pos 1-3. Using themenu options for the LOC graph, the various results can besuperimposed or removed and changes made to the details of thedisplayed image.

Functions

Start / Stop LOC (F9, Ctrl+T)

The LOC function is started automatically during a Replay. It shouldbe noted for LOC graphs that the dimensioning of the x-axis beginsat the remote end. For this reason the display range for the x-axis(Max. Display) should always be greater than the cable length(Cable Length) otherwise some of the fault locations could bemissed. The vertical red bars which show the accumulations arealso called "Projections", whilst the frequency clusters are referredto as "Peak Distribution" in the menu under LOC Graph. The cursorcan be turned on and off for this graph. The cursor positions can beread off the right hand edge of the screen beneath the graph.

The use of correlation frequency distribution as the only criterion forfault analysis of a cable is not advisable. The relevant DSO graphs,the layout plan and the effect of interference are always to be takeninto consideration.

Note

4-26

This function produces a print of the currently displayed data. TheDSO and the LOC graphs in addition to the previously enteredreport can also be output on paper.

Print (F3, Ctrl+P)

This button closes the partial discharge measurement program andreturns to the main menu. If the generator voltage has not yet beenswitched off then the program cannot be closed down. In this caseyou have to press the "HV Stop" button.

Exit (F10, Ctrl+X)

Functions

4-27

Menu options

In the Edit menu there are useful functions such as "Copy DSO","Copy LOC" and Copy DSO+LOC" which copy the contents of theDSO and LOC graphs individually or together into the Windowsclipboard. This makes the writing of reports in, e.g. Word, verymuch easier. "Scan Settings…" can be set using this functionwithout having to start the actual function.

The program has further functions that are more seldom usedavailable from the menu bar. Only those that are not accessiblefrom the main menu are explained below.

The PgUp and PgDown buttons allow you to load the next DSO filefrom the current Replay directory in Offline mode. If the programcannot find a DSO file in the directory, then a short messageappears.The function "Default Directory…" opens a directory selectionwindow from which the directory can be chosen that will appear asthe default directory for Load and Save functions.

Menu options

4-28

Menu options

Under "Window Main Panel" the LOC graph can be switched off sothat the whole width of the screen can be used for the display of theDSO graphs. This is useful for very long cables and therefore longtransmission times in order to obtain better resolution. The normalsetting is "DSO+LOC" for which the two graphs are visible.

Under Options there is a collection of various general settingparameters.

The "Pulse Velocity" (propagation velocity of the signal within thecable) can be displayed as an absolute value (v) or a halved value(v/2). The units of measurement for length or velocity can beselected as either the "SI (mks) - metre kilogram second" - systemor the "fps - foot pound second" - system.

Pulse velocityUnits

4-29

Menu options

The LOC graph offers the most possibilities for setting. The differentresults like "Peak Distribution" and "Projections" can be insertedand removed individually. The type of summing of the projectionscan be variated between absolute and relative. In the absolutemode only the individual accumulation points are added and thenweaker impulses appear more intensively. The relative mode needsto be selected for strong signals. Here the dispersion along thecable is very clear and the fault positions can be differentiated in abetter way.

LOC Graph

The LOC graph has the most options for its settings. The differentresults such as "Peak Distribution" and "Projections" can beindividually superimposed or removed. The type of accumulation ofthe projections can be either absolute or relative. In absolute modethe individual frequency clusters are added together so that theweaker pulses become more noticeable. The relative mode is usedwith stronger signals as the dispersion along the cable will be theclearest and the fault locations are easier to differentiate.

The cursor for the DSO graph can be switched on and off as for theLOC graph. The trigger mode can be switched between "Single","Normal" and " Auto" modes using the menu.

Sensivity

4-30

References

[1] Erfahrungen bei der 0,1 Hz- Verlustfaktormessung mit der VLF-Anlage der Firma BAUR, Oberstein- Id. Elektrizitäts AG, IdarOberstein 1992 (Prüfbericht)

[2] Kaul, G.; Plath, R.; Kalkner, W.: Development of computerizeddissipation factor measurement system for differentfrequencies, including 0,1 Hz and 50/60 Hz8th ISH, Yokohama,1993

[3] Bach, R.; Kalkner, W.; Oldehoff, H.: Verlustfaktormessung bei0,1 Hz an betriebsgealterten PE/VPE- KabelanlagenElektrizitätswirtschaft, Jg 92 (1993), Heft 17/18

[4] Müller, K.-B.; Stucki, F.: Eigenschaften individueller water treesin VPE- KabelnElektrizitätswirtschaft Jg.92 (1993), Heft 26

[5] Oldehoff, H.: Diskussionsbeiträge von der VDEW-Kabeltagung1993, Elektrizitätswirtschaft, Jg 92 (1993), Heft 26

[6] Krefter, K. H.: Prüfungen zur Beurteilung von Kabelanlagen inMittelspannungsnetzenVWEW-Verlag, Frankfurt am Main 1991

[7] Steenis, E. F.; van de Laar, A. M.:Characterisation test andclassification procedure for water- tree aged medium voltagecables Electra No. 125 S. 88- 101

[8] Kuschel, M.; Plath, R.; Kalkner, W.: Dissipation Factor Meas-urement at 0,1 Hz as a Diagnostic Tool for Serviceaged XLPE-Insulated Medium Voltage Cables9th ISH, Graz, 1995

[9] Verhoeven, C.W.J.: Tangent Delta measurements with VLF.Sense or Nonsense?NV PNEM Facilitair Bedrijf, 1995

[10] BAUR, Prüf- und Messtechnik GmbH: Prüfung und Diagnosean Mittelspannungskabeln mit dem BAUR System PHG TD;Ident.Nr. 810-006Informationsschrift, Sulz 4/96

[11] Wonnay, J.R.; Mathis, H.-J.: Voltage test and dissipation factordiagnosis of medium voltage cables with a new high voltagefunction generator9th ISH, Graz, 1995

[12] Kuschel, M.; Plath, R.; Kalkner, W.: Dielectric Response as aTool for Insulation Diagnosis - Comparison between Time andFrequency DomainKuschel / ICDI 1997

References

4-31

[1] IEEE P400/D14Draft Guide for Field Testing and Evaluation of the Insulation ofShielded Power Cable Systems 1 to 500 kV.IEEE Standards DepartmentCopyright and Permissions445 Hoes Lane, P. O. Box 1331Piscataway, NJ 08855-1331, USAhttp://standards.ieee.org

[2] Harmonisierungsdokument HD 620 S1, Juni 1996,„Energieverteilungskabel mit extrudierter Isolierung fürNennspannungen von 3,6/6 (/,2) kV bis 20,8/36 (42) kV“CENELEC, Europäisches Komitee für ElektrotechnischeNormung, Zentralsektretareat; Rue de Strassart 35, B 1050Brüssel, Belgien.info_pub6cenelec.org

[3] Harmonisierungsdokument HD 621 S1, Oktober 1996,“Energieverteilungskabel mit getränkter Papierisolierung fürMittelspannung”CENELEC, Europäisches Komitee für ElektrotechnischeNormung, Zentralsektretareat; Rue de Strassart 35, B 1050Brüssel, Belgien.

[4] DIN VDE, Deutsche Norm für Strakstromkabel VDE 0276,Dezember 1996, Teil 620: “Energieverteilungskabel mitextrudierter Isolierung für Nennspannungen von 3,6/6 (/,2) kVbis 20,8/36 (42) kV”VDE - Verlag Berlin, 10625 Berlin, Deutschland,http://www.vde-verlag.de/

[5] ASTM100 Barr Harbor DriveWest Conshohocken, PA19428-2959Phone: (610) 832-9585Fax: (610) 832-9555http://www.astm.org

References, ContinuedReferences, Continued

Standards

[6] K. Rethmeier, W. Kalkner: „Untersuchungsbericht: Vor-Ort-TE-Messungen an Mittelspannungskabelstrecken sowie Labor-untersuchungen an aufgenommenen teilentladungsbehaftetenMuffen“, Untersuchungsbericht TU Berlin, Institut fürHochspannungstechnik, 2000

[7] M. Baur, „Case Study on PD Diagnosis in Southern Germany“, interner BAUR Bericht, 2001

[8] K. Rethmeier, W. Kalkner: „TE-Messungen an zwei geborgenen Mittelspannungsmuffen (Kurzbericht)“, Untersuchungsbericht TU Berlin, Institut für Hochspannungstechnik, 2000

[9] Colloca, Fara, de Nigris, Rizzi: „Comparision among different diagnostic systems for medium voltage cable lines“, Cired, Amsterdam, 2001