The DC resistance tester has high measurement accuracy and simple operation. It is suitable for test products such as distribution transformers, transformers, reactors, generators, motors, etc. It can also be used to measure switches, copper bars, contactors, relay contacts, metal wires, Fast measurement of test products such as cable accessories has the characteristics of fast speed and stable data.

When we use the DC resistance tester, when the measured resistance exceeds the limit, we should pay attention to the following points:

1. The resistance value of DC resistance is greatly affected by temperature, so it must be converted to the same temperature (usually 20℃, R20=(T+20)/(T+T), TCu=235) for comparison , And generally based on the oil temperature of the upper layer.

2. First consider whether there is a measurement error (such as whether the external lead is connected, whether the test lead is too long or too thin, whether the contact is good, whether the battery voltage in the bridge is insufficient).

3. Poor contact of the tap changer leads to high resistance values. For example, the switch is clean and electroplated, insufficient spring pressure, uneven stress, and carbon deposits on the overvoltage contacts will cause the resistance value to conduct. At this time, the tap changer cover should be opened and rotated several times, usually it can be eliminated.

4. The three-phase distribution transformer currently in use, the high-voltage winding adopts Y-shaped connection, when the resistance value exceeds the limit value, the following formula can also be used [RA=(RAB+rac-rbc)/2, RB=(RAB+) rac-rac)/2, RC(RBC+rac-rab)/2] in order to find the defect phase.