Transformers are the devices intended for transformation of tension of alternating current without loss to power. At input of the transformer in operation it is necessary to define its characteristics and to check their compliance to the parameters specified in technical documentation. A part of such works is determination of its resistance.
It is required to you
- - megohm meter;
- - technical documentation on the transformer;
- - dielectric gloves;
- - dielectric boats.
Instruction
1. Ground transformer conclusions. Connect all conclusions of windings of one tension together, other windings and a tank of the transformer have to be grounded. Measure transformer insulation resistance by means of the megohm meter.
2. Attach the current carrying conductor to a clip of the line device, and a wire from the grounding device (the case, a zero wire) - to a clip "earth". Put the switch of ranges of the megohm meter in position "megohms" (Mom). Twist the device handle. Determine resistance of case isolation of the transformer by a device arrow on a scale.
3. Compare the received value of insulation resistance of the transformer to specified in technical documentation. dry transformers insulation resistance at a temperature of windings of 20 - 30 wasps with a rated voltage up to 1 kV has to be not less than 100 megohms, with a rated voltage from 1 kV to 6 kV - not less than 300 megohms, more than 6 kV - not less than 500 megohms.
4. Measure resistance of windings of a direct current of the transformer. If in the transformer there are devices of regulation of tension, measurements are taken at three cycles of switching. It is necessary to measure linear resistance of windings, their size at three-phase transformers should not differ more than for 2%.
5. Check correctness of connection of windings to switches, using a method of "two voltmeters". Bring tension to one of them. Measure at the same time by two voltmeters the brought tension and tension on other winding of the transformer. The brought tension should not exceed nominal and at the same time has to be not less than 1% of its nominal size.
6. Perform measurements for all branches of windings and all phases. The relation of the brought tension to nominal also should not differ from the specified values in technical documentation more than for 2%.