What is the function of a zero-sequence current transformer (ZSCT) in core-balance earth fault protection?
Direct Answer
Option C: Detect vector sum of 3-phase currents; any non-zero value indicates earth leakage current
A zero-sequence current transformer detects earth faults by summing the instantaneous currents of all three phases. Under normal conditions, the vector sum is zero. Any deviation indicates leakage current to the hull, triggering protective relays as required by IEC 60092-503 for effective insulation monitoring and fault detection in HV systems.
All Options
Detailed Explanation & Context
A zero-sequence current transformer detects earth faults by summing the instantaneous currents of all three phases. Under normal conditions, the vector sum is zero. Any deviation indicates leakage current to the hull, triggering protective relays as required by IEC 60092-503 for effective insulation monitoring and fault detection in HV systems.
Relevant Framework: STCW 2010 Manila Amendments • DG Shipping E-Learning & Exit Exam Standards • High Voltage Safety Officer & Switchgear Operations (HV).
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