transformer winding resistance tester.pdf

7/28/2019 transformer winding resistance tester.pdf

1/9

ETP SYSTEM: UM3B

1/1

UM3B: Basic features

CBM: Condition Basedmaintenance philosophy. Three phase Winding

resistant meter. Charge of the transformer

winding inductance andcore saturation.

Safe dissipation of theenergy stored in thetransformer after test.

Fully automatic test. Guided operation. Automatic storage tests. Automatic reports

generation. Numerical and Graphical

data presentation. Maintenance Contracts

and help on-line. CE Marked.

UM3B Transformer Winding Resistance Tester

ETP System: Transformers Test

Introduction

UM3B is a low resistance ohmmeter specially designed for transformer windingresistance measurement. However, thisequipment is also suitable to measurerotating machines windings resistance.

Power transformer windings resistancemeasurement presents special problems tosave. These problems are:

- Transformer windings inductancecharging and core saturation.

- The actual measurement of thewindings resistance

- The safe dissipation of the energystored in the transformer after test.

In order to stabilize windings resistancemeasure we need to charge the windinginductance and gets core saturation. Onlyin these conditions we will obtain the testcurrent required for the test. UM3B makesit automatically assuring that all made tests

are comparative in time ( Repeatability of measurements) and time test shorter.

Once the measurement is completed, theenergy stored in core and windings of tested transformer must be dissipated in asafe manner to avoid substantial arks withor without adverse consequences. UM3Bmakes it in an automatically way too.

It is in the measurement of three- phase transformer windings, wherefull power of the equipment isshown, since with only oneconnection, the instrument provides simpleand compound resistance value for eachwinding: both high and low voltage andtertiary. Furthermore, to calculate theresults, the system takes into account thetransformer connection group, and thetemperature at which the test is carried out,as such results are provided at the


2/9

ETP SYSTEM: UM3B

2/2

reference temperature specified by theoperator.

UM3B equipment allows us to do thefollowing measurements automatically:

Automatic windings resistance onthe three phases.

Temperature corrected resistancevalues.

Calculations of individual andcompound resistance values.

This System has been developed in closecollaboration with users and experts intransformers measurement andmaintenance of Iberdrola Company, amajor European utility.

UM3B is a based microcontroller unitcontrolled by a portable PC connected

through one RS-232 line. The power software installed in the portable PC is anuseful guide through the measurements

process and also offer an easy to use toolfor predictive maintenance and diagnostic.

The based Windows software allows us tointroduce the transformer characteristicsand make an automatic and guided test. Allthe tests will be automatically stored intothe PC hard disk, organized by machineidentification characteristics (for exampleserial number).

Application

To ensure the proper operation of power transformers we must to check periodicallythat insulation between turns and

electrical/mechanical properties are theexpected ones.

Due to used current is far from nominalone, the UM3B test is totally non-destructive for the machine. With windingsresistance measurement it is possible todetect problems in transformers like:

Pressure lost in connections Damages in the regulator Short-circuit turns Winding hot points

Some problems can be corroborated withother ETP Systems measurements.

UM3B test has several advantages andmeets the following requirements:

Automatic measuring system . For the prevention of errors due to acquisition,handling and correction times resulting

from the environmental and machineconditions at the time of measuring.

Measurements Repeatability . Thisguarantees that readings performedover a period of time have been

obtained in the same way and with thesame degree of accuracy andtolerances. This allows studying theevolution of such measurements.

Automatic and organized results storage . This greatly simplifies thehandling of the large amount of information obtained.

Updateable system . The system has been developed such that whatever new software developmentmight arise, may beimplemented with the samehardware elements.

Key parameters acquisition .The system automatically calculates alist of parameters and graphics for machine status diagnosis.

Non-destructive testing . If handled properly, there is no risk of damage tothe insulation during testing.


3/9

ETP SYSTEM: UM3B

3/3

UM3B:Testing Procedure

The control software has two differentoptions: test performance and resultanalysis. The first one is very easy tool for the operator because allows to make aguided test after the operator introduce the

basic transformer characteristics. Theanalysis block is a very useful option for expert that must to analyse all stored datafrom a tested machine.

Main Screen. Transformer Winding Resistance Meter Software.

Test Processes

Following the steps proposed by thesoftware it is possible to make a completetest. Software guides the operator about

connections, precautions that must to takeand the actual measuring state, being veryinteractive. Every step has a new screenwith simple and useful information for theoperator.

Test Processes. Transformer Winding Resistance Meter Software


4/9

ETP SYSTEM: UM3B

4/4

In order to initiate the test, the operator should introduce the basic parameters toidentify the transformer under test. Thismachine technical data information onlyhas to be introduced in the first made test,

following tests recover these data andcreate automatically an organizedhistorical tests database. In the next figuresevery step window appear:

Technical Data Screen

Measurement configuration

Connection Indications


5/9

ETP SYSTEM: UM3B

5/5

In the test option the basic screen is themeasurement window. The software willautomatically store the numeric data andthe current signal into a file that will be

loaded from the analysis option. Resistancemeters are very useful for operator in order to detect possible windings problems.

Basic measurement screen. Resistance meters

Measurement sampling

Magnetization


6/9

ETP SYSTEM: UM3B

6/6

Analysis Processes

These processes load the results file of every test stored by test software and alldata are presented in several screens. Threedifferent fields can make the search: platenumber, manufacturer and kind of machine.

Maintenance responsible uses these data todiagnostic the machine state. Finally, it is

possible to print all data in a nice reportformat. The clear presentation of thesereports makes interpretation of resultsstraightforward and facilitates predictivemaintenance techniques.

When the machine has got several taps,software also presents a graph with allwinding resistance, which is a very usefuldiagnostic tool.

Analysis option. Transformer Winding Resistance Meter Software.

Winding resistancetable

Machineidentification


7/9

ETP SYSTEM: UM3B

7/7

Winding resistance graph

Result Table

Application Note

In the following example the capacity of UM3B system is shown to detect problemsin transformers. In this case it is thedetection of a regulator problem in a12MVA-20/6,9 Kv-Dyn1 load regulationtransformer.

In the first UM3B test, a variation isdetected in the resistance measure at 5 tapC phase. In the report generated whenconcluding the test a revision of the

regulator it is recommended. Oncedisassembled the regulator a defect of thesame one is observed.

With the repaired and mountedregulator is carried out a secondUM3B rehearsal, being observedthat the problem has disappeared.

Next figures illustrate the process:


8/9

ETP SYSTEM: UM3B

8/8

Transformer with regulator problems (5 Tap C Phase )

Regulator Breakdown

Measurement after repair. Regulator problem has disappeared


9/9

ETP SYSTEM: UM3B

9/9

Specifications

Power requirements:

230VAC 10%50/60 Hz115V AC 10%50/60 Hz

Installation category II, according to IEC 664-1

Power: 450 VA (max)

Test signal

Voltage: 24 Vdc (Current cables in open circuit)

Current: 0 - 20 A 5%

Winding resistance Measurement

Conditions Range Accuracy Resolution

@ 20 A 10 m 0.5%

2 digits1

4 digits

@ 20 A 100 m 0.5%2 di its

10 4 digits

@ 5 A 1 0.5%2 di its

100 4 digits

@ 500 mA 10 0.5%2 digits

1 m 4 digits

@ 50 mA 100 0.5%2 digits

10 m 4 digits

@ 5 mA 1000 0.5%2 digits

100 m 4 digits

CE Certified

CE Directive: DC 93/68/CEEElectromagnetic Compatibility:

DC 89/336/CEEIEC 61000

Electric Safe: DC 73/23/CEEUNE-EN 61010-1

Measurements mode:

Manual: User stops test when he believes thatMeasurement reaches stabilityAutomatic: Software stops test automatically when

measurement reaches stability.

Parameters used:

Compound winding resistancesSimple winding resistances

Ambient conditions

Operation:Temperature: 5 to 35CHumidity: 10 to 80%

Storage:Temperature: 10 to 75CHumidity: 5 to 90%

Mechanical Properties:

Length: 40 cm.Width: 45 cm.Height: 13.5 cm.Weight: 8 Kg.

Other characteristics:

Hardware: Microprocessor controlled measurement. High efficiency Power-On and Communications

LEDs indicators. Relay control matrix for measurement with three-

phase equipment. Protection circuit that discharges the energy stored

in the equipment being tested once the test hasfinished, or if there is a drop in mains voltage.

Security & heavy duty test connector.

Software: Direct control, data visualization, storage and

analysis in Personal Computer. Communicationthrough RS232 line.

Specific software for MS Windows 95 and upper operative system.

Test easy to perform, by suitably trained personnelat the installation and without the need for

specialists to be present. Advanced test identification and storagesystem.

Graphic visualization for windingresistance.

UNITRONICS, S.A.U.Avda de la Fuente Nueva, 528709 San Sebastin de los ReyesMadrid SpainTel: +34-91-540 01 25Fax: +34-91-540 10 68

Http://www.unitronics.esEC - 1.059.0300

transformer winding resistance tester.pdf

Documents