Residual Overvoltage Relay (Neutral Displacement Relay)
NPUH800 provides the zero-sequence voltage monitoring of three-phase networks with isolated or high impedance earthed neutral.
This multi-function relay supervises phase to phase and phase to earth faults and the good operating of the circuit breaker and its trip circuits.
As well as the usual protection functions, NP800 relays provide monitoring, measurement and recording of the electrical quantities of the network. The relays can be set locally, using either the keypad and display or the RS232 port, or remotely using the RS485 port.
Setting, reading, measurement and recording are all available locally or remotely.
CONTROL AND PROTECTION FUNCTIONS
- Maximum of zero sequence voltage with 2 thresholds [59N]
- Latching of the output contacts 
- Trip circuit supervision of the breaker [74TC]
- Configuration and parameter setting by local MMI or off-line / on-line PC
- Measurement of electrical quantities:
– Residual voltage and maximum value
- 2 setting groups, locally or remotely selectable by digital input or by the communication channel
- Self-diagnosis: Memories, output relays, A/D converters, auxiliary supply, cycles of execution of software, hardware failure
- 3+1 assignable output units / 4 assignable digital inputs (option: additional card with 4 assignable output relays and 4 assignable digital inputs)
- Event recording: 250 locally recorded events, 200 saved in case of loss of auxiliary supply
- Disturbance recording according to Comtrade® format: storage of 4 recordings of 52 periods
- Optional Communication by Modbus/RTU® RS 485 or Ethernet by Modbus/TCP