mpeschel-vlf cable testing
DESCRIPTION
MANUALTRANSCRIPT
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10/4/2006 1
Michael T. PeschelHigh Voltage, Inc.Copake, NY. USA
www.hvinc.com
VLF CABLE TESTING INCLUDING TANGENT DELTA & PARTIAL DISCHARGE
WITH A BRIEF LOOK AT CABLE FAULT LOCATING.
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10/4/2006 2
SUBJECTS COVEREDWhat Is VLF
VLF ApplicationsIEEE Standards
Lab and Field ResultsHow To Perform The Test
Myths about VLFWho Uses VLF
Selecting a VLF ModelSelecting A Cable Test Method
VLF ConclusionTan Delta Testing
VLF Partial Discharge TestingCable Fault Locating
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THIS CAN BE PREVENTED
In-service failures cause great damage to faulted cables and adjacent cables. Not so if failed under a VLF test.
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10/4/2006 4
WHAT IS VLF?
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A VLF HIPOT IS SIMPLY AN AC OUTPUTINSTRUMENT BUT AT A LOWER FREQUENCY.
THE LOWER THE FREQUENCY OUTPUT, THE LOWER THE CURRENT AND POWER REQUIRED TO TEST HIGH
CAPACITANCE LOADS LIKE CABLES.
DONT OVERCOMPLICATE IT. ITS A SIMPLE AC WITHSTAND TEST.
VLF IS THE EASIEST, LEAST EXPENSIVE, MOST CERTAIN WAY OF TESTING THE AC INTEGRITY OF A CABLE.
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10/4/2006 6
DROP THE FREQUENCY
Very Low Frequency: 0.1 Hz and lower.By decreasing the frequency, it is possible to test miles of cable with a small and affordable unit.
Output frequencies range from 0.1 0.01 Hz.IEEE400.2 recognizes frequencies as low as 0.01Hz.
At 0.1 Hz, it takes 600 times less power to test a cable, or any other high capacitance load, than at 60 Hz. At 0.01 Hz, 6000 times higher capacitive loads can be tested than at 60 Hz with the same power consumption.
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Xc = 12 x pi x f x C
The lower the frequency, the higher the capacitive reactance, or Xc. The higher Xc , or resistance across the power supply output, the lower the current/power needed to apply a voltage.
VLF EXPLAINED
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60 Hz vs. 0.1 Hz
At 60 Hz. a 1 F cable has an Xc of 2.65 kOhms. At 22 kV peak, it requires 8.3 amps of current to test.
Total power supply rating must be 183 kVA.
At 0.1 Hz, the Xc is 1.59 megohms. At 22 kV, the current needed is 14 mA.
Total power supply needed is only .304 kVA.
(22 kV is the typical test voltage for 15 kV cable)
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10/4/2006 9
50 kVAC @ 3 kVA
Can test ~ 50 of cable
60 Hertz
40 kVAC @ 1.2 kVA
Can test ~ 5 miles of cable
0.1 0.02 Hertz
60 Hz. vs. 0.1 Hz.
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APPLICATIONS
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Power CableIEEE 400-2001 & IEEE 400.2-2004
Large Rotating MachineryIEEE 433-1974
Diagnostic Testing:Tan Partial discharge
IEEE STANDARDS EXIST
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CAN OTHER LOADS BE VLF TESTED?
Yes, but no standards exist that define the test.
Most other loads are low in capacitance, permitting60Hz AC hipots to be used.
Sometimes large insulators are VLF tested if apowerful enough 60Hz hipot is not available.
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10/4/2006 13
WHY TEST CABLES WITH AC VOLTAGE?
Cables are designed to carry AC voltage.
They are factory tested with AC voltage.
Cables operate under AC voltage stress.
Cables should be tested with AC voltage.
Why would you not use AC if you could?
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Can Now AC Stress Test Cable
z With VLF, utilities, testing services, industrials, and others can now AC stress test cables in the field.
z Just like with vacuum bottle or rubber glove testing, now a go/no-go AC stress test can be performed on power cable.
z If a cable cant hold 2 3 times normal voltage, its not healthy. Find the problem, make the repair, and move on.
z At the very least, every newly installed and repaired cable should be VLF tested before energizing, since many failures are due to installation damage, faulty workmanship, stress from in-service failures, or over voltage thumping.
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Other Methods Dont Get It Done.
DC Hipot5 kVdc Megger
DC Hot stick adaptor24 hour soak
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VLF IT!
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IEEE STANDARDS
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NORTH AMERICAN STANDARDS FOR VLF TESTING
IEEE 400-2001 overall cable testing standard sanctions VLF testing of cables.
IEEE 400.2-2004 standard for VLF cable testing
IEEE 433-1974 covers VLF testing for rotating machinery. Now beingupdated. Standard for smaller motors/gens. under consideration.
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IEEE Std. 433-1974 (1974)z Recommended Practice For Insulation Testing of Large AC
Rotating Machinery with High Voltage VLF.
z Refers to Large AC Machines 10 MVA/6 kV & above.
z Test Waveform: Must be Sinusoidal.
z Test Frequency: 0.1 Hz.
z Test Voltage: 1.63x 60 Hz RMS Level
MOTOR & GENERATOR TESTING
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IEEE400.2-2004z Recommends test voltage of 2 - 3V0
(V0 equals line-to-ground voltage)
z Test duration is 15 60 minutes
z Best recommendation is for 30+ minutes
CABLE TESTING
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System Voltage
phase to phase
kVrms
5
15
25
35
Installation
phase to ground
kVrms/kVpeak
9/12
18/25
27/38
39/55
Acceptance
phase to ground
kVrms/kVpeak
10/14
20/28
31/44
44/62
Maintenance
phase to ground
kVrms/kVpeak
7/10
16/22
23/33
33/47
---------------------- 0.1 Hz Test Voltage --------------------
IEEE400.2 FIELD TEST VOLTAGESFor Shielded Power Cable Systems
Using Sine Wave Output VLF
Test voltages are generally 2 3 time the line-to-ground system voltage.
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Cable Test Voltages Determined
12.5 kV system = 7,217 V0 or line-to-ground.x 3
21.7 kV Maintenance test
The peak of the sine wave is the factor driving the inception of partial discharge. Hence, the 22 kV test spec is used for the peak of a sine wave VLF. The test is equivalent to ~ 2x V0 rms. Also, kV/mm insulation varies greatly. Need at least 2Vo.
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WHY 2Vo 3VoThe IEEE standard says 2 3V0 for 15 - 60 minutes.
Cables routinely see 2x normal voltage due to reflected waves, transients, etc. VLF test voltage
must be at least 2x normal line-to-ground.Must use enough voltage for enough
time to let the VLF do its job of growing electrical trees to failure.
An abbreviated test or a test too low in voltage is worse than no test.
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Growth rate at 0.1-Hzsinusoidal test voltage
(mm/h)2.3
10.9-12.658.3-64.2
Test voltage factor
(V/Vo rms)234
XLPE TREE GROWTH IEEE 400-2001Sine wave VLF rapidly grows electrical trees to failure.
A 15kV 133% cable has an insulation thickness of 5.9 mm.In a 30 minute test, nearly all defects triggered into pd will grow to failure.
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RESULTS FROM FIELD USE AND LABORATORY RESEARCH
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VLF TEST RESULTS
Numerous case studies show that if a cable passes a properVLF test, there is a > 95% assurance of no in-service failure in the next few years. Nothing is perfect, but only a few percent possible failure rate post VLF testing is very good. Far better by multiples than with other testing methods.
Bottom line: If a cable can hold 2 3 times normal voltage for 30-60 minutes, its good for years.
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XLPE TESTING STATISTICS
TNB in Malaysia 3 V0 @ 60 minutes
17,435 VLF tests performed 2,179 cable failures
4.9210746 - 60
5.9312931 - 45
21.5446913 - 30
67.6214720 - 12
Minutesto failure Failures % of total
89.16%
2.78% of tested cables failed later in service. (Many cables were PILC)Tests conducted 2001 2002. Continue to buy VLF and test all cables.
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XLPE TESTING STATISTICS
Japan: Furukawa, Chubu & Tokyo Electric
Research done to determine test voltage and duration versus expected life. Results were:
A 33 kV cable tested at 60 kV peak @ 0.1 Hzhas a 97% probability of no failure for >3 years.
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10/4/2006 29
Germany went through extensive research and testing and produced some of the first VLF products more than 20 years ago.
German standard calls for 3Vo rms/peak for 60 minutes.
Following a successful VLF test, there is a >98% chance of no in service failure for the next several years.
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Most US users test at the IEEE recommended voltages for 30 minutes. When in doubt, err on the high side for voltage and/or longer duration
Consensus of data shows that once passing a VLF test, better than 95% of cables will not
fail in service in the next few years.
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10/4/2006 31
The World View Of VLF
DC not recommended by cable companies for cables > 5 years & in moist environments
IEEE 2 3Vo for 15-60 minutes30+ minutes @ 3Vo recommended.
Germany 3Vo for 60 minutes
Japan 3Vo for 15 minutes
Malaysia 3Vo for 60 minutes
Over 40 countries have purchased the
HVI VLF
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HOW TO PERFORM A VLF TEST
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TEST PROCEDUREz VLF testing is easier than DC testing.
z Isolate cable ends like with DC testing, although no cleaning and bagging is necessary.
z Remove all arrestors, capacitors, transformers, etc.
z Connect VLF HV lead to conductor & ground to shield.
z After selecting appropriate test frequency, apply voltage
z There are no leakage currents to read. Test is go/no-go
z If cable holds, test is over. Cable is good for years.
z If cable fails, make repairs and repeat test, or replace.
z If second insulation failure occurs, maybe stop testing and replace.
z Most models can test all three phases at once, saving time.
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VLF Test Hookup Per IEEE400.2
Some VLF units have no return wire. HV output and ground cables only.
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CABLES INCLUDED WITH TWO PIECE MODEL
HV outputfrom tank
Phase jumpers Interconnectwith grounds
Scope bnc
2 test leads for capacitance
measurement
Ground hook
Cable connectorshook or clamp
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VLF-4022CM
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OPERATING INSTRUCTIONS
1. Select Frequency
2. Turn to mA
3. Rotate to zero(Zero start intlk)
4. Press Main Power
5. Press HV On
6. Rotate to raise voltage
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WHAT IS CABLE FAILURE INDICATION?
Thermal overload on panel will trip
Voltmeter will indicate breakdown
Current will spike
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FAULT LOCATING NECESSARY
When VLF testing, severe cable defects will fail. A thumper will be needed. Trouble trucks should be equipped with a VLF and thumper sized for the cable class.
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COMMON VLF MYTHS
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VLF IS DESTRUCTIVE TO INSULATION.
NOT TRUE. Cable is factory tested at voltages far higher than field VLF levels. VLF is destructive to existing defects that are severe enough to be triggered into partial discharge during the test. Thats the point of the test light up defects and let them grow to failure. Minor defects and good insulation are not effected.
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VLF AGGRAVATES DEFECTS THAT FAIL LATER IN SERVICE
Only if the test is not properly performed, like any testing method. The proper VLF voltage must be applied for a long enough time to permit defects triggered into pd to grow to failure. An improper test is worse than no test at all. The same can be said for 60Hz hipoting, pd testing, and other tests. If done wrong, problems could result. If done correctly - positive results.
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VLF IS REALLY ALTERNATING DC
Not true. At 0.1 Hz there are polarity reversals every 5 seconds. Even at 0.01Hz there are reversals every 50 seconds. That does not compare at all to a 15 minute, constantly negative output DC hipot test. Space charges and traveling waves are not developed in insulation during a VLF test. The IEEE recognizes frequencies down to .01Hz as ok.
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VLF EFFECTIVENESS IS UNPROVEN
Very wrong. Tell that to the hundreds of users over more than 15 years that have tested tens of thousands of cables with great success. Tell that to the IEEE, CEA, EPRI, cable companies, utilities, and many international organizations that have all endorsed VLF.
A VLF instrument is just a low frequency AC hipot. Simple product simple test simple physics. There is nothing to not work.
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ONLY 0.1 HZ IS A VALID TEST
The IEEE standard recognizes frequencies down to 0.01Hz. Whileit is true that most of the worldwide research over the last 20 yearsinto testing levels and durations has been done at 0.1Hz, that doesnot mean lower frequencies are ineffective.
Its a tough argument to make that 60 Hz is ok, DC is ok for a lot of things including new cable, 0.1Hz is ok, but 0.05Hz is not?
60Hz
.1Hz
.05Hz DC
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ONE WAVEFORM OUTPUTIS BETTER THAN ANOTHER
Of the three major VLF vendors, two output waveformsare offered: sine wave & cosine-rectangular (trapezoidal).
Both work well to VLF hipot cable, although the sine wave output grows electrical trees faster - see IEEE400.
-However -A sine wave VLF is better suited for use as a voltage source for tan delta and partial discharge testing, both desirable add-ons to VLF testing. Also, a sine wave is necessary for motor/generator testing per IEEE433.
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WHO USES VLF
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UTILITIES TESTING SERVICES
INDUSTRIALS CONTRACTORS
Other methods of cable testing have their place, but VLF is embraced worldwide as the easiest, most effective, most
economical method of cable testing.
Over 500 VLF units have been shipped from High Voltage, Inc. over the last eight years, delivered to 40 countries and
many US locations. Other VLF products have shipped from other vendors for even longer.
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COUNTRIES USING HVI VLF
HVI has shipped over 500 VLF products to the following:
USACanadaTaiwanIndonesiaSo. KoreaAustraliaSaudi ArabiaEnglandCosta RicaBoliviaIsrael
So. AfricaSingaporeHong KongBelgiumPuerto RicoHollandNew ZealandJapanMalaysiaRussiaSpain
Slovak RepublicCzech RepublicChinaUAEVietnamPanamaJordanGermanyCyprusHondurasLithuania
ThailandMexicoIndiaBulgariaFijiVenezuelaFinlandGreeceQatarArgentina
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SELECTING A VLF MODEL
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System Voltage
phase to phase
kVrms
5
15
25
35
Installation
phase to ground
kVrms/kVpeak
9/12
18/25
27/38
39/55
Acceptance
phase to ground
kVrms/kVpeak
10/14
20/28
31/44
44/62
Maintenance
phase to ground
kVrms/kVpeak
7/10
16/22
23/33
33/47
WHAT SIZE CABLES ARE TO BE TESTED?
Do you do Install, Acceptance & Maintenance testing?From IEEE400.2
The above chart only covers ratings to 35kV. VLF testers exist that can test cables rated up to 230kV.
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WHAT CABLE LENGTHS ARE TO BE TESTED?VLF units are rated by the uF of load they can test.
Model VLF-25CM
0 - 25 kV Peak
0.1 Hz @ 0.4 f Load
Can test up to 4000 of 15 kVcable depending on size.
Perfect URD model
Example: 15 kV XLPE 750mcm 220 mils ~ .1uf/1000
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Most Popular Utility Model VLF-6022CM Can test cables rated to 35 kV.
0 - 60 kV Peak
0.10 Hz @ 1.1 f Load0.05 Hz @ 2.2 f Load0.02 Hz @ 5.5 f Load
Example: 15 kV XLPE 750mcm 220 mils ~ .1uf/1000
At 0.1 Hz can test ~ 2 miles. At 0.02 Hz can test ~ 10 miles.
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MODEL SIZES AVAILABLE(all vendors included)
Voltage ratings from 20 kV 200 kV
Load ratings from 0.4 uF 50 uF
For a 15 kV cable, 0.4 uF can test ~ 4000
Some models can test > 30 miles of cable
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Sine wave output is needed to use VLF as a voltage source for td and pd testing.
IEEE433 for VLF testing rotating machinery requires a sine wave output.
Leave all your future testing options open by buying a sine wave VLF.
WILL IT BE USED FOR TAN DELTA& PD TESTING?
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120 kV peak up to 5.5 uF
90 kV peak
Up to 2.75 uF
40 kV peak up to 5.5 uF
65 kV peak up to 22 uF
Other Models
200 kV soon available
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VLF THUMPER
Complete URD Cable Care System
Combination VLF AC Hipot and Thumper
VLF Output: 0 - 30 kVAC peak
Load Rating: 1.0 uF @ 0.1 Hz ~ 1.5 miles of 15 kV cable
Discharge: 0 12 kV @ 650 J
VLF Cable Burning Mode
Radar Ready
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SELECTING A CABLE TEST METHOD
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CABLE TEST METHODS
AC Power Frequency. AC Series & Parallel Resonant. DC Hipot. Very Low Frequency (VLF) AC Hipot. Tan Delta, Partial Discharge, And Other
Diagnostic Methods.
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Ideally, VLF, Tan Delta, and Partial Discharge should all be used.However, there are real world factors affecting the decision.
1. Type of test results desired2. Ease of use3. Cost of equipment
There is no one perfect method that does it all. A variety ofapproaches is needed to meet all the requirements encountered.
SEVERAL METHODS WHAT TO USE?
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WHATS THE GOAL?
z Verify new installation?
z Verify repaired cable?
z Verify critical cable?
z Help to prioritize cable replacement or injection?
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WHATS THE SITUATION?
z Direct buried must pinpoint problem to repairz Cable in conduit or trench - replaceablez Cable in raceways visible and easily replaceablez How old is cablez What is the failure historyz How easy is it to repairz Is there alternate feed should failure occur during testz Is fault location and repair available?z How much downtime can be tolerated?
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EXAMPLES OF SITUATION vs. METHOD
New Install: Diagnostic test not appropriate, the insulation is presumed good. VLF it to make sure there are no installation flaws or pulling damage.
Old suspect cable: There may be many defects, dont VLF. Use TD to see how degraded cable is. If modest degradation, then PD possibly followed by VLF.
Critical cable in conduit: PD test to expose location and severity of defects. If no PD tester available, VLF.
Direct buried, hard to repair: TD test to evaluate condition to prioritize cable injection.
Prioritization for replacement or injection: If a comparative condition assessment test is desired, tan delta is the easiest method.
Post repair test: VLF repaired cable to make sure it holds no further damage caused by over voltage thumping or from original failure.
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SO, WHAT TO DO?
NO SHORT AND EASY ANSWER.
If an effective method is beyond the economic reach and ability to operate of 90% of the market, then its not a
solution. A combination of methods is needed: some easy and economical (VLF) and some more complicated and more expensive (TD & PD), and each yielding different
but important data about your cable.
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IT ALL STARTS WITH A VLF
Fact: As more industrial customers, utilities, and specifying engineering companies spec VLF testing, per IEEE400.2, you will need a VLF.
Fact: In addition to performing VLF AC stress tests, a VLF hipot is the foundation for other tests, like partial discharge and tan delta. You need VLF for pd and td.
To learn the most about the health of your cable, all three tests, if economically and logistically feasible, are recommended. If not all possible, VLF should be the fallback.
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SUMMARY &CONCLUSION
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z Has the virtues of DC test equipment (low cost, small size, light weight, easy to use) but is AC.
z Does not have the negative consequences of DC.
z Requires 1/600 1/6000 of the kVA of power frequency.
z Can be used for breakdown tests and predictive tests such as TanDelta and Partial Discharge. (sine wave VLF units)
z Internationally accepted Standards exist and more are in the process of issuance.
VLF TESTING SUMMARY
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CONCLUSION
The surest way to verify the AC integrity of any load is perform an AC stress test.
Its easy and certain. The load holds voltage or fails.
VLF testing is easily performed with minimal training.
Worldwide standards and decades of history exist.
Some VLF models are very portable and affordable.
VLF makes Tan Delta and Partial Discharge diagnostic testing easier and more economical.
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OTHER CABLE TEST METHODS USING VLF
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YOU HAVE YOUR VLF. WHAT ELSE CAN YOU DO?
Accessorize. Add on a
Tan Delta measurement instrument.
Partial Discharge detection instrument.
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Dissipation Factor or Loss Angle Measurement For Power Cables
Non Destructive Testing To Determine Insulation Quality
(Similar to Power Factor Testing)
TANGENT DELTA or TAN
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z Evaluates overall condition of cable (rather than localized problems as with PD measurement)
z Absolute values, variations, and trending of values are of interest for predicting insulation integrity
z Tan Delta is more easily measured at VLF (magnitude increases as frequency decreases)
z Requires VLF sinusoidal applied test voltagez Excellent way to evaluate Water Treesz Useful to help prioritize replacement, injection and helps to
determine what additional test may be useful
TAN DELTA MEASUREMENTUsing VLF @ 0.1 Hz
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73
z Addition of a parallel R-C Component
z Water trees increase resistive current through insulation
z The R component is voltage dependent (nonlinear I = V/R)
z Tan Delta values increase with increasing voltage
CHARACTERISTICS OF WATER TREES
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74
With perfect insulation, a cable is a near perfect capacitor, with a 90 phase shift between voltage and current. Less than 90 indicates insulation degradation. Cables can be rated good, marginal, or bad. Not extremely precise but valuable for prioritizing cable replacement or injection. Also helps to determine what further tests may be worthwhile.
The tangent of this angle is calculated
I
V
IC
IR
IR IC
= tangent of C R
Cable insulation Cable Cross Section
Simplified Cable Model and Phasor DrawingTan Delta = IR/ IC - measured in radians
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75
TAN DELTA VS. VOLTAGE NEW AND AGED XLPE CABLES
New and Aged 15 kV XLPE Cable (Nov 2000)
0
0.01
0.02
0.03
0.04
0.05
0.06
0 2.5 5 7.5 10VLF Voltage (kV rms)
L
o
s
s
A
n
g
l
e
(
T
a
n
D
e
l
t
a
)
Aged
New Cable
New cablelinear tan delta #s
versus voltage
Aged cablenon-linear tan
delta #s versus voltage
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0.1 Hz phase 1 phase 2 phase 3 phase 1 phase 2 phase 3x Vo tgdelta L1 tgdelta L2 tgdelta L30.5 0.0018 0.0008 0.0013 (2Uo-Uo) (2Uo-Uo) (2Uo-Uo)1.0 0.0019 0.0009 0.0014 0.0035 0.0018 0.00251.5 0.0026 0.0011 0.0019 0.0019 0.0009 0.00142.0 0.0035 0.0018 0.00252.5 0.0044 0.0026 0.0032 0.0016 0.0009 0.0011
0.0000.0020.0040.006
0.0 1.0 2.0 3.0Voltage x Vo
t
a
n
d
e
l
t
a
L2: tg delta 0.1Hz L3: tg delta 0,1HzL1: tg delta 0.1Hz
TAN DELTA NUMBERS VERSUS INCREASING VOLTAGE
& RATIO OF 2Vo/Vo
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Dissipation Factor Tan DeltaFrom IEEE Std 400-2001
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TAN DELTA LOSS ANALYZER
HV Divider Signal analyzer/controller
60kV model
Used with VLF as voltage source
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TAN DELTA TESTING
Advantagesz Less destructive than VLF, DC, or 60 Hz testingz Allows prioritization of cable replacement or injectionz Easier to use and interpret than other diagnostic methods
Disadvantagesz Can be destructive if cable very degradedz Gives overall condition of cable, not singularitiesz Not best for mixed type cable runsz More useful with historical data
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VLF PARTIAL DISCHARGE
TESTING
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SEE UNDERGROUND CABLE DEFECTS
A PD detection system can show you the location and severity of insulation and accessory defects.
Using a VLF as the voltage generator to apply voltages up to 2Vo, long cables can be tested with portable equipment.
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OFF-LINE VS. ON-LINE PD TESTING
Off-line testing using a VLF permits over voltage analysis. Can measure PDIV and PDEV up to 2Vo.
On-line pd testing can only detect pd at operating voltage, missing defects with a PDIV > 100% of operating voltage, yet cables routinely see twice normal voltage due to reflected waves, transients, switching surges, etc. Useful for accessory checking.
Off-line testing may be less convenient, but the information gained is far more valuable.
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0.1Hz vs. 60Hz PD TESTING
Both frequencies initiate pd at defect locations. Both can measure PDIV, PDEV, magnitude, and location.
The benefit of VLF is smaller size, lower weight, far lower cost, and can test longer cables.
A 100lb VLF can do the job of a2000lb 60Hz series resonant
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THE BEST OF EVERYTHINGStart with a VLF tester to perform AC withstand testing.
Add a Tan Delta accessory for evaluating the overall conditionof a cable to help prioritize replacement, injection, or todetermine what other tests might be helpful.
Add a Partial Discharge accessory to map the locationand severity of pd in the insulation and splices, or todetermine what other tests might be helpful.
Perform all three tests to get the most complete profile possibleof your cable.
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CABLE FAULT LOCATING
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FAULT LOCATING ON NETWORK SYSTEMS
GET THE RIGHT TOOLS FOR THE JOB
Thumper Features Needed For PILC
Multiple output voltage taps
High joules >2000
High burn current >200mA
TDR/radar capability w/current pulse
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10/4/2006 87
THUMPING CONCEPT
1. Thump with low voltage but high joules. A powerful burner or VLF is needed to reduce fault voltage. Thumper must have 2 or 3 output voltage taps.
2. Need high joule rating to make loud noise and to generate strong current pulse for tracing.
3. Good use of TDR helpful, even in network systems.
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10/4/2006 88
VLF AIDS FAULT LOCATING
VLF hipoting is the best method of burning down faults.
Permits use of lower voltage, less expensive thumpers.
Utilities should have VLF anyway for cable integrity verification.
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10/4/2006 89
LISTENING DEVICES NECESSARY
Dont handicap your efforts by not buying a top level listening device.
Acoustical & electro-magnetic needed
TEC X35 from TEC Power Corp
SDAD from Aquatronics
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SDAD X35 Acoustical & Magnetic Electro-Magnetic
Solid & PILC Networks Only
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THE IDEAL SETUP FOR NETWORKS
VLF-6022CM60 kV, 0.1 0.05 HzLoad rated to 5.5 uF
CDS-3632U9/18/36 kV @ 3200 joules280 mA burn current
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FAULT LOCATING - A SYSTEM APPROACH
Properly sized & featured thumper
Quality listening device
TDR
Other knowledge of network system
Accurate maps
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10/4/2006 93
Thank You
Mike Peschel - High Voltage, Inc.
www.hvinc.com