Why Are There Significantly More High-voltage Disconnect Switches Than Circuit Breakers In Substation Design?

In typical substation configurations, the number of hv isolator devices often far exceeds that of circuit breakers. This phenomenon is common in power engineering design, typically reaching 2 to 4 times the number of circuit breakers. This situation primarily relates to system operation and maintenance conditions. According to the operational rules for high-voltage side equipment in substations, hv isolator switch primarily provides clear circuit break points under low-current conditions. In contrast, circuit breakers serve as core devices responsible for power system protection and current interruption tasks, exhibiting distinct functional differences.

high voltage electrical isolator must be positioned at multiple locations along each incoming/outgoing line, bus section, and even between equipment to establish compliant electrical clearances during different operational phases. isolator high voltage lacks arc-extinguishing mechanisms and is unsuitable for breaking load currents. However, under no-current conditions, it physically disconnects circuits to achieve visual isolation of specific equipment. The requirement to provide such explicit break points at every connection significantly increases the number of high voltage isolators.