The SW-DLZ series ground fault monitoring and protection device (anti-step-over tripping device) is the new generation of digital and intelligent product launched by Shangwei Electric in 2014. It is primarily used in the 400VTN systems of power plants, steel, textile, chemical industries, etc. It mainly solves the issue of the lack of zero-sequence protection for phase-to-ground faults in the MCC section of low-voltage systems, which leads to extensive power outages in the PC section.

The SW-DLZ series phase-to-earth short-circuit monitoring and protection device (anti-over-step tripping device) is suitable for 400V TN systems. It can address issues such as non-metallic grounding of MCC lines, failure to operate of plastic-case switches and thermal relays, which lead to over-step tripping of the PC and widespread power outages. The phase-to-earth short-circuit monitoring and protection device continuously monitors the zero-sequence CT current of each circuit, triggers an alarm and then a trip upon meeting the conditions. It drives the tripping coil (trip release) of the circuit breaker for phase-to-earth short-circuit protection, cutting off the faulty power supply line, and realizing the phase-to-earth (zero-sequence) protection function. Simultaneously, the alarm contact outputs a yellow light alarm, indicating that this drawer has been removed from operation due to zero-sequence protection action. It also adjusts the setting values (current threshold and delay) of the phase-to-earth short-circuit protection to prevent over-step tripping and power outages, which could cause significant economic losses.