No, neither MIKO-7 nor MIKO-8 does that. Electric current can be measured prior to the open-circuit test. Perform the open-circuit test first, then measure resistance of the transformer windings to direct current. In 1-3 days the transformer will demagnetize in a natural way.
From10 to 0.001А. At resistance above 0.3 ohm the amperage decreases. Thus, high amperage allows saturation of the magnetic core, which considerably reduces the time of measurements.
Time of measurement depends on inductance of the controlled object and averages from 20 seconds to 1.5 minutes. Maximum time of measurement is 7 min 51 s. It was recorded during testing the ORDC-533000/330000 transformer.
Its impact is reduced to the maximum extent as minimum drift of the instrument current is ensured: <0.002%/s.
This function allows more accurate determination of conditions the transformer winding is. If according to the results of calculations the deviation of resistance between windings does not exceed 2%, we can assume that winding is in good order. Knowing such passport values of a transformer as resistance, temperature of resistance measurement and winding material we can calculate working temperature of the winding. Winding overheating accelerates the insulation aging and, hence, reduces the service life of a transformer.
It perfects the accuracy of measurements as in this case the cable resistance and resistance between cable cramps and transformer inputs have no impact on the results of measurements.
In case of the circuit break (e.g., in case of cable rupture or faulty LTC) the self-induction emf occur. MIKO-7 and MIKO-8 have in-built protection from critical voltage at open elements and parts of the instrument. But deliberate stop of measurements by breaking the instrument cables may result in a failure of the instrument protection. Therefore, please follow the safety rules.
