Test run of micro ohmmeter MIKO-9 at Irkutsk hydro electric station

In July 2018 SKB is launching a new micro ohmmeter MIKO-9 for DC current resistance measurement in inductive and noninductive circuits in the range from 10 µOhm ÷ 30 kOhm for the currents of up to 10А. 

Very soon the first set of MIKO-9 will arrive to the warehouse and we will start the sales. At the moment we are receiving purchase orders. Meanwhile we are testing the instrument to be included into the State Register of the measuring instruments. The tests are run at the high voltage objects at Irkutsk hydro electric station.

The instrument has demagnetization mode for residual magnetization of transformer magnetic core after tests running at DC before switch to other type of testing, for example no-load run, short circuit and transformer ratio measurement and other.

MIKO-9 provides demagnetization of power transformer core according to the state standard ( GOST 3484.1) at automatic mode or manual mode when input current demagnetization borders and pitch..

According to the state standard ( GOST 3484.1) demagnetization of transformer core is done by supplying current first at one direction and later at the another one. Each time DC direction should be changed and its value should be reduced by 30-40% relatively to the previous value. As the experience shows, sometimes at the stage of current direction change it is not always possible to demagnetize transformer up to the needed parameters. This influences the results of the no-load run experiment.

If there is a doubt that increased current of no-load run is caused by the demagnetization quality and not by a transformer magnetic core, it is possible to reduce the current supply up to 1%. Demagnetization time is increased accordingly.

In addition to measuring the electrical resistance and demagnetization MIKO-9 has a number of additional functions making the instrument different to the analogues:

• Database of typical measured objects such as power transformer, current transformer, resistant transformer, resistant object, generator, etc. This function not only helps a user to chose an object but also allows the instrument to consider the object’s specific and exclude additional settings. In addition, this function makes it easier to systemize the results and save them in the archives.
• Testing technical condition of OLTC contactor without opening the transformer (DRM test). Based on the results of the measurements at the moment of contacts switching a graph of the current change is made. The graph helps to determine the switching time and the overall technical condition of the tested time.
• Winding resistance measurement at the process of cooling test according to the State regulations.
• Fully automatic process of measurement and results archiving. The archive of measurements in the device is designed to view, copy or delete the measurement results stored in the non-volatile memory of the device and to provide data such as: automatic calculation of the relative deviations of the electrical windings resistance between 3 phases; automatic recalculation of the linear windings resistance connected by a triangle or a star in the electrical resistance of the phase windings; automatic conversion of the electrical winding resistance measured at the current temperature into electrical resistance of the passport temperature (taking into account the winding material).
• The device can also transmit the results both by USB and Bluetooth channel; it corresponds to the digital energy.