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The combined transformer for preventing electricity theft is simply a kind of transformer, mainly for preventing electricity theft. As it is a kind of equipment for measuring and protecting the system, it is likely to burn out if it is not properly used. So why does it burn out? Let's see.
(1) in case of short-circuit between low voltage side turns and phase to phase of combination transformer to prevent electric theft, the low voltage insurance has not yet been fused. As the exciting current rapidly increases, the fuse wire of the high voltage fuse tube will fuse or the transformer will be burnt out.
(2) when single-phase grounding occurs on the 10kV outgoing line, the non-fault relative ground voltage on the primary side of the transformer is square root 3 times of the normal voltage value.
(3) the elements with capacitive and inductive parameters in the power network, especially the ferromagnetic inductance elements with iron core, cause ferroresonance when the combination of parameters is not favorable. If the circuit breaker does not close at the same time, the no-load bus input with transformer and ferromagnetic transformer, and the high-voltage coil of distribution transformer shorting to the ground may cause ferroresonance. When ferroresonance occurs, its overvoltage multiple can reach more than 2.5 times, which causes insulation breakdown of electrical equipment and equipment burning accident.
(4) the zero-sequence current flowing through the primary winding of the combination transformer against electric theft increases (compared with the system where the grounding current exceeds the standard). When running for a long time, the thermal effect generated by this zero-sequence current will cause insulation damage and explosion crack of the transformer.
(5) nonlinear oscillation (arc grounding overvoltage) exists in the system, which greatly aggravates the damage process of the transformer in the system.
(6) the heat dissipation condition of ct is poor.
If the rating or wiring of the anti-electric theft combined transformer is not installed and used in the correct way, then it is easy to have various problems, so it must read its operating procedures carefully when it is used in the future.