At the end of June, tests of the new control instrument for PKR-2М OLTCs VACUTAP MR on TRDTSN-200 MBA 220/11 kV power transformer with OLTC have been carried out.

PKR-2М has inherited advantages of its predecessor (PKR-2) and acquired new additional features. The instrument allows radial diagram measurement (for reactor and resistor type OLTCs) and oscillography of contactor operation (high-speed resistor-type OLTCs) for all phases at the same time, but unlike its predecessor, OLTC in-place diagnostics mode has been implemented in PKR-2М (DRM method).

In-place diagnostics mode allows you to check the state of OLTCs without removal of the contactor tank cover and oil drain. This mode is based on the DRM method and consists in measurement of current through the winding that includes OLTC.

Oscillography results for OLTC contactor switching – VACUTAP MR using DRM method
Graphical representation in the PKR-2M software

Note: According to the regulatory documents, contact transfer time shall be in the range of up to 40 ms. In accordance with diagnostics results, the transfer time ≈ 38.6 ms.

PKR-2М software is functional, interactive, and most importantly, it is simple and intuitive, which allows you to carry out the most accurate analysis:

  • A feature of VACUTAP MR OLTC is an absence of the bridge position, unlike instruments like RS-3, which was recorded on the oscillogram of contactors operation;
  • In addition to a range of analysis parameters, initial data allow for the determination of resistor resistance;
  • After mathematical treatment, the initial data enable more accurate determination of the contactor contact transfer time and make it possible to check if the current limiting resistors are in good condition, as in this case. Using zoom, enlarge switching of taps and put special cursors, which allow you to see details of any section of the graph.

Gaining experience, we are ready to share it with you, so if you want to study the instrument practically, you can always leave an application for an individual workshop on our website and the experts of our company will contact you.

We express our gratitude to the employees of RETO Plant JSC, who took part in this testing.

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