Functional Description

Overview

The earth-fault protection consists of measuring the earth-leakage current in an electrical installation, and disconnecting the installation when the current becomes hazardous to life and property.

Functions

The VigiPacT RHU/RHUs relay is used together with a VigiPacT toroid (open or closed) or a rectangular sensor.

• Measures the earth-leakage current detected by the toroid.

• Displays the earth-leakage current.

• Trips the installation protection circuit breaker through an MN or MX release if the earth-leakage current exceeds the threshold IΔN for a time greater than the delay Δt.

• Implements two earth-leakage current thresholds, one corresponding to a pre-alarm and an other to an alarm.

• Communicates via the Modbus communication serial line (only for VigiPacT RHU relay).

Alarm Detection

The alarm threshold I alarm corresponds to an earth-leakage current that is hazardous for the installation.

An alarm is active when the measured earth-leakage current is greater than the set alarm threshold (I alarm) on toroid for a period of time greater than the set alarm delay (t alarm in milliseconds or seconds).

• When an alarm is active, the ALARM and PRE-AL LEDs are switched on.

• When alarm is detected, the Metering screen is displayed, and the earth-leakage current value blinks.

Pre-alarm Detection

The pre-alarm threshold I pre-alarm correspond to an earth-leakage level that must be eliminated before it becomes hazardous for the installation.

A pre-alarm is active when the measured earth-leakage current is greater than the set pre-alarm threshold for a period of time greater than the set pre-alarm trip delay (t pre-alarm in milliseconds or seconds).

• When a pre-alarm is active, the PRE-AL LED is switched on.

• When pre-alarm is detected, the Metering screen is displayed and the earth-leakage current value blinks.