The voltage of one phase in the 6KV incoming cable cabinet shows zero. Why is this?
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There is a 6KV incoming voltage cabinet at the production site, with incoming lines for phases A, B, and C; the voltage of one of these phases shows as zero, while the voltages of the other two phases are 6KV； Downstream of the cabinet is a three-phase dry-type transformer. Why does the phase voltage become zero? Missing phase?
For a 6kV power supply system, if the voltages of the other two phases are normal while the voltage of this phase is zero, and the low-voltage supply is still working properly, it indicates that the voltage meter is damaged； The possibility of a phase loss is low; in the event of a phase loss, the low-voltage motor will trip or some of the lighting fixtures will stop working.
The low-voltage power supply downstream is working properly, and the three-phase 220V outputs of the dry-type transformer all show normal values. So why is the voltage of phase B showing zero? Are the voltages measured by the sensors for phases A and C not line voltages?
First, measure the voltage on the secondary side of the incoming current transformer, and then determine where the problem lies based on those measurements.
Check whether the voltages of the three phases at the PT output terminals are normal, and then verify that the wiring of the voltmeter is secure.