What does a pole disagreement scheme do in relation to an EHV breaker?

A pole disagreement scheme is specifically designed to improve the reliability and safety of electrical systems, especially when dealing with Extra High Voltage (EHV) circuit breakers. This scheme monitors the closing operation of the circuit breaker to ensure that all poles (typically three for a three-phase system) operate in unison. If the poles do not close simultaneously, it indicates a potential malfunction that could lead to system instability or damage should a fault occur.

By tripping the breaker when a discrepancy is detected among the poles, the pole disagreement scheme protects the power system from issues such as unbalanced loading, which can result from one or two poles closing while another remains open. This is crucial for maintaining proper system operation because an uncoordinated closing can create transient conditions that may lead to equipment damage, overheating, or system outages. The primary purpose of this protective measure aligns with ensuring coordinated operation of all poles, thus enhancing overall system reliability.