Differential protective switch with neutral cable break protection

摘要

The energy for the circuit breaker is derived from an amplifier, with the amplifier (A) supplied from the phase line and connected to the neutral line through a rectifier diode (D1). The conductor connecting the amplifier to the diode (D1) connected to the neutral (N) is also connected to the earth wire (PE) by a branch which comprises another diode (D2), with appropriate polarity, and a neon lamp (T) connected in series with the diode (D2) to earth and having an operating voltage (80V) substantially less than the mains phase voltage. In the event of the neutral wire being cut, the neon lamp (T) is raised to a sufficient potential above earth to illuminate it, while under normal operation it is held one diode drop above neutral.