This type of boundary switch (watchdog), is an intellectual switch for locality protection and auto disconnecting. The switch makes real-time monitoring on the over-current, short-circuit and earthing failures within the boundary. And it makes effective isolation of the failure zone under the boundary so as to avoid the power interruption of the whole system caused by one point failure or some zone failure.
This switch is mainly made up of ZW20A-12 vacuum circuit breaker, FDR-2 intellectual controller and voltage transformer. The three apparatuses are electrically connected by aerial plug and sealed cable. It functions as over-current protection, instantaneous break protection, zero-sequence protection, reclosing and avoiding rush current. Equipped with remote controller, it can control the opening and closing within a short distance. And with GPRS communication module, it can realize four-remote function. When the switch is put into operation, it checks the current of each phase and zero-sequence. Upon the logic judgement of the intellectual controller, it can automatically switch off the over-current, single-pole grounding and short circuit between phases.