Voltage and Frequency Relay
NPU800 provides the voltage and frequency monitoring of electrical networks.
This multi-function relay supervises phase to phase and phase to earth faults, positive, negative and zero sequence voltage and the good operating of the circuit breaker and its trip circuit. With its numerous under and over voltage and frequency thresholds, NPU800 is suitable for network supervision, load management and load-shedding.
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
- Undervoltage with 4 thresholds 
- Positive sequence voltage drops with 3 thresholds [27P]
- Max of negative sequence voltage with 2 thresholds 
- Overvoltage with 2 thresholds 
- Max of zero sequence voltage with 2 thresholds [59N]
- Overfrequency with 4 thresholds [81O]
- Underfrequency with 4 thresholds [81U]
- 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:
– Instantaneous, integrated and maximum values of phase to neutral voltages or phase to phase voltages
– Positive and negative sequence voltage (according to wiring)
– 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