Test transformer is a relatively common instrument, then how to test its core whether there are problems, the impact of the work efficiency problems, so today Xiaobian to give you a simple analysis, how to test the core is faulty . Can roughly use the following three methods
Clamp ammeter method (online measurement). The clamp-type ammeter method for transformers with external core leads can accurately test the multipoint earth fault of the iron core without power failure. Measure the grounding lead current regularly every year. The current should be less than 100 mA. If it is higher than this value, monitoring should be strengthened. After the transformer is put into operation, the resistance of the grounding wire is continuously measured several times. As the initial value, if the initial value itself is large, it indicates that the transformer itself is caused by a large magnetic flux leakage, and the measured value can be regarded as a no-fault grounding point after a small difference. If the grounding line current is greater than 1 ampere, and the increase is more than the initial value, it may be a low-resistance grounding or a metal grounding fault. This situation should be dealt with in time.
Chromatography (charged oil). Chromatographic analysis of sampling, if the total hydrocarbon significantly increased, and the gas in the main component of methane, ethylene, and carbon monoxide and carbon dioxide gas compared with the previous change is not or almost unchanged, can be judged as bare metal overheating, may be iron core Multi-point grounding or iron core silicon steel sheet edge damage needs further inspection. If acetylene is present in the above total hydrocarbons, it is likely that the unsteady current core is now grounded at multiple points.
Insulation resistance method (blackout test). Measure the resistance between the iron core and the shell with a 2500 volt shake meter. The insulation resistance is 200 megaohms and above, indicating that the iron core is well insulated. If the rocking table indicates that the iron core is connected with the shell, you can use an ohm meter to measure the resistance between the iron core and the shell. If the measured value is 200 to 400 ohms, it means that the iron core has a high-resistance grounding point. Multi-point grounding fault treatment; if the measured value is more than 1000 ohms, the current flowing through the ground is small, and it is difficult to eliminate the fault, and it is not necessary to continue the operation and perform on-line monitoring periodically, such as clamp-type ammeter method (with core (External lead), oil chromatographic analysis, found after abnormal treatment; if the measured value is 1-2 ohms, it is determined that the core has a metal grounding point, the transformer must be processed.
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