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Transformer diagnostics: MT-3
Transformer diagnostic devices

Thanks to the co-operation with the B&C Diagnostics company, a completely new measurement construction dedicated to transformer diagnostics has been developed.

Basic characteristics of MT-3

This device has replaced the previously produced MT-1 and MT-2 instruments. Thanks to its new technical solutions the MT-3 allows for significantly simpler and faster diagnostics. The relay matrix used as well as the system of measurement cables, enables fully automatic measurements to be undertaken for the most common transformers and, as a result, there is no need to modify the measurement set-up i.e. re-clipping of wires.

No matter which parameter is to be measured and which tap position (or range of taps) is desired, the software will select an appropriate source, set up a proper circuit and control motor-drive to obtain appropriate measuring conditions.

Significant progress comparing previous versions (MT-1 and MT-2) as well as devices produced by competitors, is the three-phase measurement of the transformer ratio and magnetizing currents.

The modification significantly shortens measurement time. An important feature of the MT-3 is security against destructible activity of over-voltage caused by circuit break whilst measuring winding resistance. The used cabling method minimizes the risk of accidental opening of the circuit during measurement and together with electronic protection practically liquidates the risk of damage.


The wide experience gained during the development and operation of previous MT series instruments enabled the creation of well-designed software. The application controls all parameters during measurement, but also assists the user in the analysis and evaluation process of results obtained. The software allows the user to avoid unnecessary work by calculating deviations, converting temperatures and comparing the values obtained to previous results.

It is worth mentioning that there is the possibility of comparing registered current curves of the diverter switch that allows for precise tracking of changes of the technical condition of diverter switch.

Functions of MT-3 measurement application:
  • graphically displayed results
  • report of measurements undertaken
  • automatic comparison of measurement results to previous values (factory values, previous measurements)
  • advanced procedures of results analysis

Value examinedAccuracy
Measurement of motor drive inherent delay
Measurement of power switch time
Resolution measurement time 0,1ms
Winding resistance measurement
Technical method in accordance
PN-81/E-04070.05 standard
Scope of measurement 0,001 Ω - 100 Ω
Resistance precision measurement 0,2%
Voltage and current precision measurement 0,1%
Measurement of transformer ratio in accordance
with PN-81/E-04070.06 standard
Measurement precision of transmission 0,2%
Magnetizing current measurementPrecision of current measurement 0,2%
Operation parametersAllowable values
Scope of operation temperature-15 ... 45oC
Personal computerPC LAN (IPX/TCPIP protocol)
Supply voltage230V AC +10% -20%
Weight8,5 kg


In the MT-3 construction, typical computer components and measuring card have been replaced by a specialized system designed and produced by Diagnostics from Hungary, for use in transformer diagnostics instruments. Thanks to this, substantially increased precision of measurements have been obtained together with the elimination of additional external power sources for the measurement of winding resistance.

Usage of the system mentioned allows for substantial reduction of the dimensions and weight of the equipment.

In the MT-3 device, data acquisition and signal processing take place in the measuring part of the instrument. Controlling of the measurement process and visualization of the measurement results is undertaken by an additional computer (usually a laptop). Communication between the MT-3 instrument and the computer takes place via the LAN network.

Thanks to this, practically any PC equipped with a network card which operates under Windows 98/2000/XP, can be used.

Documentation:    MT-3 DTR     MT-3 DOU

Winding resistance
measurements report

The possibility of comparing
OLTC switching times by
directly placing them on each
other makes assessing changes
of technical condition easier

The table of measurement
results with deviations of
average values allow a quicker
evaluation of transformer's
technical condition during carrying
out test and a faster printout of
the measurement report

Comparison of the
oscillographic waveforms
of the OLTC head
switching times




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