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IEC 60265-1: High-Voltage Switches — The Functional Boundary Between Switches and Circuit-Breakers
Load-Break Switch, Disconnector, Circuit-Breaker — Understanding Their Functional Boundaries Saves 60–80% on Switchgear
IEC 60265-1:1998 specifies high-voltage switch (1–52 kV) general requirements. A load-break switch can interrupt rated load current but cannot interrupt fault current — this is the fundamental distinction from a circuit-breaker, and the reason it costs 70–90% less.
| Equipment | Interrupts | Fault Making | Visible Isolation | Relative Cost |
|---|---|---|---|---|
| Circuit-Breaker | Fault current ✓ | ✓ | Maybe | 100% |
| Load-Break Switch | Rated load current | ✓(limited) | Maybe | 10–30% |
| Disconnector | No/minimal capacitive | ✗ | ✓ | 3–10% |
When is a load-break switch sufficient?: In transformer protection schemes, if the transformer HV side has a circuit-breaker, downstream branch load-break switches do not need fault interruption capability — the upstream breaker clears faults. Ring Main Units (RMU) embody this philosophy: incomer/outgoer use load-break switches (normal switching); transformer feeders use switch-fuse combinations (fuse operation during faults triggers the switch to open). This combination saves 60–80% on switchgear investment vs. an all-breaker scheme.
TN Lab — All breakers is safest but most expensive. Understanding the functional boundary between switches and breakers enables optimal techno-economic decisions.
