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Operation precautions of DC resistance tester

time:2020/11/16   source:华天电力  reading:227 time

In the measurement process of the DC resistance tester, in addition to strictly complying with the electrical safety regulations test procedures and equipment, it also points out that the coil temperature is measured stably, and the transformer tank is required. The lower part of the temperature difference should not exceed 3℃. There is transformer coil inductance, the charging current measurement is unstable, the current must be stable before counting, measures must be taken to shorten the charging time, if necessary, to minimize the contact resistance of the test lead loop. Transformer taps in operation are often affected by dirt such as oil film and make their contact poor. Generally, it is necessary to switch several times before measuring to avoid discrimination errors. When measuring the low-voltage side of the transformer, all personnel should keep a proper safe distance from the high-voltage side.


Transformer DC Winding Resistance Tester.png


The DC resistance tester should avoid strong social vibration, direct sunlight and magnetic fields during transportation, storage and work. When storing and using the instrument, pay attention to protecting the environment with different temperatures and humidity. It should be placed in a dry, ventilated, and free of corrosive gas, and no damp, rain, or exposure to the sun. When in use, handle it with care and do not drop it. You can check whether the conductive circuit of the company's equipment has direct contact with the society, poor welding, faulty coils, and wrong wiring methods. In the actual measurement of small and medium-sized transformers, most of them use a DC bridge method. When the resistance value of the tested coil is above 1 ohm, it is generally measured by a single-arm bridge, and when the resistance value of the tested coil is less than 1 ohm, it is measured by a double-arm bridge. When a double-arm bridge is used for wiring, the potential pile head of the bridge should be close to the For resistance measurement, the current pile head should be connected to the potential pile head.


Before the DC resistance tester performs the measurement, the resistance value of the tested coil should be estimated first, and the bridge magnification selector should be placed in an appropriate adjustment position to short-circuit the non-tested coil and ground it. Then turn on the power switch to charge, after fully charged, press the galvanometer switch to quickly adjust the measuring arm. Move the pointer of the galvanometer to the direction of the zero line in the middle of the scale of the galvanometer, make fine adjustments, and record the resistance value when the pointer steadily stops at the zero position. At this time, the resistance value of the tested coil=multiplying factor×the resistance value of the measuring arm. After the measurement is completed, first turn on the ammeter button, and then release the power switch


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