Protection functions

The protection relay offers integrated protection functions including two-stage 

overvoltage and undervoltage protection, two-stage residual overvoltage protection, 

as well as singlestage negative phase-sequence overvoltage protection and 

single-stage positive phase-sequence undervoltage protection.

Measurement

The protection relay physically measures the three phase-tophase voltages and the residual voltage of the power system.

Further, from the phase-to-phase voltages the protection relay

calculates the positive and negative phase-sequence voltages,

the one-minute average phase-to-phase voltage, the average

phase-to-phase voltage for a user-specifiable time frame, the

maximum value of the one-minute average voltage, and the

maximum and minimum phase-to-phase voltage value since last reset.

The values of the voltages measured or calculated can be

accessed locally via the user interface on the protection relay’s

front panel, or remotely via the serial communication interface

on the rear panel of the protection relay.

Disturbance recorder

The protection relay is provided with a built-in battery backedup digital 

disturbance recorder for four analog signal channels and eight digital signal channels. 

The analog channels can be set to record the curve form of the voltages measured. 

The digital channels can be set to record external or internal relay

signals, for example the start or trip signals of protection relay’s

stages, external blocking or control signals. Any digital relay

signal such as a protection start or trip signal, or an external

relay control signal can be set to trigger the recording. 

The recordings are stored in a nonvolatile memory from which the

data can be uploaded for subsequent fault analysis.