Megger MTO106 Operating Manual

MTO106

Transformer ohmmeter

User’s Manual

Art No. ZP-BN01E Doc. BN034794AE V01a 2018

WWW.MEGGER.COM

MTO106

Transformer ohmmeter

User’s Manual

NOTICE OF COPYRIGHT & PROPRIETARY RIGHTS

The contents of this manual are the property of Megger Sweden AB. No part of this work may be reproduced or transmitted in any form or by any means, except as permitted in written license agreement with Megger Sweden AB. Megger Sweden AB has made every reasonable attempt to ensure the completeness and accuracy of this document. However, the information contained in this manual is subject to change without notice, and does not represent a commitment on the part of Megger Sweden AB. Any attached hardware schematics and technical descriptions, or software listings that disclose source code, are for informational purposes only. Reproduction in whole or in part to create working hardware or software for other than Megger Sweden AB products is strictly prohibited, except as permitted by written license agreement with Megger Sweden AB.

TRADEMARK NOTICES

Megger® and Programma® are trademarks registered in the U.S. and other countries. All other brand and product names mentioned in this document are trademarks or registered trademarks of their respective companies.

Megger Sweden AB is certiﬁed according to ISO 9001 and 14001.

Postal address:

Megger Sweden AB Box 724 SE-182 17 DANDERYD SWEDEN

T +46 8 510 195 00 F +46 8 510 195 95

BN034794AE ZP-BN01E MTO106

Visiting address:

Megger Sweden AB Rinkebyvägen 19 SE-182 36 DANDERYD SWEDEN

seinfo@megger.com www.megger.com

Contents

1 Introduction

............................................................. 6

1.1 Product description ......................................6

Features and beneﬁts .................................................. 6

Applications ................................................................ 6

1.2 Winding resistance testing ..........................6

1.3 Receiving instructions ...................................7

1.4 Warranty .....................................................7

Warranty repair ........................................................... 7

2 Safety

............................................................. 8

2.1 General ........................................................8

Symbols on the instrument .......................................... 8

2.2 Safety instructions ........................................8

Maintenance ............................................................... 9

3 Instrument description and

Accessories ....................................... 10

3.1 Panel .........................................................10

3.2 The display .................................................11

3.3 Accessories ................................................11

Included .................................................................... 11

Optional .................................................................... 11

4 Setup and operation

........................................................... 12

4.1 Preparations ...............................................12

4.2 Testing Single and Dual windings ...............12

4.3 Testing Delta winding resistance .................13

5 Application examples

........................................................... 14

5.1 Testing transformers with tap changers ......14

5.2 Temperature correction ..............................14

5.3 Manual demagnetization of a transformer .15

6 Troubleshooting and Calibration ....... 16

6.1 Troubleshooting .........................................16

7 Speciﬁcations

........................................................... 18

Speciﬁcations ...................................................18

4 MTO106 ZP-BN01E BN034794AE

BN034794AE ZP-BN01E MTO106

1 INTRODUCTION

1

Introduction

1.1 Product description

The MTO106 transformer ohmmeter is an easy-to-use, line-operated instrument speciﬁcally designed for safe and accurate ﬁeld measurement of winding resistance in smaller transmission and distribution transformers.

It has dual channels with a wide measurement range and can accurately provide information about the vast majority of power transformers, reactors and instrument transformers. The test current can be manually set in ﬁve different ranges to ﬁt transformers of various sizes.

The unit has built-in safety protection for testing transformers and other components with high inductance. To ensure operator safety, MTO 106 automatically discharges the stored energy in the transformer at the end of each test. If a current lead is disconnected while current is ﬂowing through the transformer, the current will ﬂow through the alternate path of the potential lead without damage to the instrument or risk to the operator

Features and beneﬁts

▪ Test current up to 6 A and stable current generation

▪ Up to 48 V output voltage for fast charging of

transformer windings

▪ Light weight and portable

▪ Very short start-up time

▪ Ease of use

▪ Resistance range, 10 µOhm to 30 kOhm, for testing a

wide variety of transformers.

1.2 Winding resistance testing

Transformer winding resistances are measured in the ﬁeld in order to check for abnormalities due to loose connections, broken strands, and high-contact resistance in tap changers. Interpretation of results is usually based on a comparison of measurements made separately on each phase in the case of a wye-connected winding or between pairs of terminals on a delta-connected winding. Comparison may also be made with original data measured in the factory.

Winding resistance measurements in transformers are of fundamental importance for the following purposes:

▪

Calculations of the I2R component of conductor losses.

▪ Calculation of winding temperature at the end of a

temperature test cycle.

▪ As a diagnostic tool for assessing possible damage in the

ﬁeld.

Problems or faults occur due to poor design, assembly, handing, poor environments, overloading or poor maintenance. Measuring the resistance of the windings assures that the connections are correct and the resistance measurements indicate that there are no severe mismatches or opens. Many transformers have taps built into them. These taps allow ratio to be increased or decreased by. Any of the ratio changes involve a mechanical movement of a contact from one position to another. To tetect contact wear, winding resistance measurements are usually performed at each tap in a load tap changer.

Applications

The MTO106 is mainly intended for ﬁeld measurements of smaller transmission and distribution transformers:

▪

To verify factory test readings

▪ As part of a regular maintenance program.

▪ To help locate the presence of defects in transformers

such as increased contact resistance in terminal connections and tap changers.

The instrument can also be used for general resistance measurements of for instance control wiring, voltage regulators, motors, generators and all types of connections.

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