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Detection Technology

The DC resistance tester is malfunctioning

time:2020/10/3   source:华天电力  reading:614 time

The DC resistance tester is optimized for measuring the DC resistance of three-phase windings of large-capacity transformers. The three-phase winding DC resistance of the transformer can be tested at the same time. The tap switch can be directly adjusted without discharging the on-load tapping transformer. The measurement time is one-third of the traditional single-phase measurement, which can greatly shorten the working time and labor intensity. , The equipment uses a large-screen LCD display, a full Chinese graphical interface, clear and intuitive, and the operation is very simple.

Transformer DC Winding Resistance Tester.png

The purpose of the DC resistance tester to measure the DC resistance of the transformer winding is to:

1. Check the welding quality of wires and leads inside the winding;

2. Check whether the winding or lead wire is broken;

3. Check whether the contact of each position of the tap changer is good;

4. Check whether there is a short circuit between layers and turns;

5. Check the correctness of the parallel branch circuit, whether there is one or several breaks in the windings wound by several parallel wires.

When the DC resistance tester is used for a period of time, various problems will always appear. At this time, it is necessary to solve in time, therefore, as a user, you should master some necessary troubleshooting methods.

Failure 1: Three coil failure

Test method: Usually, when the coil fails, the oil in the tank is more oily, the box is bulging, and the oil-flavored Coke. Insulation resistance and DC resistance can be measured, insulation resistance "zero" and DC resistance increase unstable.

Treatment method: Check the hanging core to determine the fault. If the damage is minor, it can be repaired. If the fault is serious, please replace the coil. Technical transformation should be carried out when the seal of the oil conservator is not enough.

Fault 2: Tap changer failure

Test method: measure different DC resistance separately, if it is not complete, it means that the switch is burned out. If the sub-DC resistance is unbalanced, it means personal contact burns. The burnt taste is heavy, indicating overheating or arcing.

Treatment method: the core should be suspended for inspection. If the switch contacts are in poor contact or there are only slight traces of overheating or arcing, the transformer DC resistance tester can be disassembled for maintenance and reused. If the burn is severe or there is contact between ground discharges, a new switch should be replaced. When it touches the ground, it may cause the deformation of the high-voltage coil and the rotation of the cross-section wire. The coil should be repaired or re-wound (replaced).

Trouble three: core failure

Test method: measure the core of the screw insulation resistance, which is less than this. The transformer DC resistance tester should be repaired.

Treatment method: After pulling the core, pull out the damaged core screw and replace the insulation.

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