10kV capacitor bank discharge PT burned out
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In a friend’s factory, the discharge PT connected in parallel with the 10kV capacitor bank has burned out. What could be the reasons? Could out-of-phase operation of high-voltage contactors cause the PT to burn out? Can it be prevented by adding zero-sequence voltage protection?
If the system experiences a single-phase ground fault, a large capacitive current will flow in the circuit; the heat generated by this capacitive current in the arcing coil can burn it out! Voltage surges can occur during different phases, causing damage to the coil assemblies and also burning out the PT; applying zero-sequence voltage should help avoid normal imbalances in the system
The PTs connected in parallel to a 10kV system are primarily used to obtain the measurement voltage; when protection devices are installed on the high-voltage side, they provide the voltage necessary for protecting the capacitors. It only discharges when the capacitor loses power. Different phases have almost no effect on PT; if it gets damaged, it should be due to a quality issue.