NEUTRAL TO EARTH OVERVOLTAGE DETECTION DEVICE

摘要

An electronic device for continuously monitoring the neutral to earth voltage of an electronic or electrical equipment operating on AC mains. The device (30) comprises a voltage amplifier (32) configured to receive and amplify the voltage across the neutral (14) and earthing (16) of the equipment, a voltage rectifier (37) configured to receive and rectify the voltage from the amplifier, a voltage comparator (34) configured to compare the rectified voltage received from the rectifier with a reference DC voltage preset in the comparator and give a low output or a high output depending on whether the rectified voltage is below the reference voltage or at or above the reference voltage, a semiconducting switch (54) configured to remain in open position when the comparator output is low and to switch to closed position when the comparator output is high and a relay (36) comprising a common contact (C), a normally closed (NC) contact and a normally open (NO) contact. The amplifier is configured to receive power from a DC power supply (31). The voltage comparator and common contact of the relay are powered by a DC voltage source (31a). The NC and NO contacts of the relay are connected to a first indicator and to a second indicator respectively. Also an electronic device for continuously monitoring the neutral to earth voltage of an electronic or electrical equipment operating on AC mains and disconnecting the AC mains to the equipment under neutral to earth over voltage conditions, in which the NC and NO contacts of the relay are connected to a tripping device connecting the equipment to the AC mains (Fig 2).