Help, please! Experts, help me!
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Dear experts, may I ask: 1. Can a medium-voltage comprehensive protection system calculate the zero sequence current? If so, is it still necessary to install a zero-sequence current transformer? 2. Contactors are rarely used in medium-voltage systems, while contactors are present in the circuits of low-voltage motors. Why aren’t there any in medium-voltage systems? Economic reasons?
Medium-voltage protection: if all three phase currents flow into the integrated protection device, the zero-sequence current is calculated automatically, eliminating the need for a zero-sequence current transformer. In some medium-voltage installations, in order to save on investment, medium-voltage contactors are used for low-capacity circuit motors.