67kA Short-Circuit Making and 82kA Peak Withstand Capacity
Distribution networks near large power sources or heavy industrial loads can experience short-circuit currents well above standard levels. This switch is type-tested to close safely onto a short circuit with a peak making current of 67kA and to withstand the subsequent dynamic forces up to 82kA peak. These ratings exceed typical 12kV load switch specifications, making the unit suitable for substations fed directly from high-capacity transformers or utility busbars where fault levels are elevated.
Multi-Second Short-Time Withstand Ratings
Upstream protection coordination in complex distribution networks sometimes requires the switch to carry fault current for more than one second before the breaker clears the fault. This unit provides graded short-time withstand ratings: 31.5kA for 1 second, 25kA for 2 seconds and 20kA for 3 seconds. The thermal capacity of the copper conductive path and the structural strength of the mounting frame are verified at all three durations, giving system designers flexibility in relay setting and breaker selection.
1600A Fuse-Combination Breaking Capacity
In the fuse-combination version, high-voltage current-limiting fuses mount directly above the switch body. The fuses carry normal load current and clear short-circuit faults inside their rated breaking range. The combined breaking capacity reaches 1600A at 12kV, which covers transformer feeder protection for most secondary substations up to about 10MVA. A fuse striker mechanically trips the three-phase load switch whenever any fuse blows, ensuring full isolation without needing a separate circuit breaker. The maximum XRNT fuse current is 125A, matching standard high-voltage fuse dimensions.
Compressed-Air Arc Quenching with Visible Isolation Gap
The switch breaks load current by drawing the arc into a compressed-air column inside the arc-extinguishing tube. When the contacts separate, the moving contact pulls the arc through the tube, where the air flow cools and stretches the plasma until it cannot sustain itself. This method requires no sealed gas or vacuum bottles, which keeps the unit light and simplifies field service. After the arc is extinguished, the moving contact drops away from the fixed contact to create a clear, visible air gap that meets safety standards for maintenance access.
2000-Cycle Mechanical Endurance
Frequent switching operations in industrial distribution networks wear down contact surfaces and operating linkages over time. This switch is type-tested to 2000 full make-break cycles without overhaul. The contact system uses silver-plated copper with optimised pressure springs that maintain consistent contact force through the full service life. For substations that switch feeders daily or run automated load-transfer schemes, the 2000-cycle rating reduces downtime and extends the interval between maintenance inspections.
Application Scope
This load switch is intended for indoor 10kV/12kV distribution systems in power stations, industrial plants and commercial buildings. It controls power flow to distribution transformers, isolates feeders for cable maintenance, and sections industrial busbars. The 630A rating covers secondary substation transformers up to about 6.3MVA, and the fuse-combination version extends protection to transformers up to 10MVA depending on fuse selection. The series is also applied in 20kV and 24kV networks with voltage-specific insulation components.
