Operation of Phase Failure Relay

Asitha, I can speak of the American models I see. The three phase monitors I encounter are used to control the start circuit. The internal contacts break the starter / contactor coil. They can reset automatically or manually. This is the basic unit and I'm sure someone makes a model that will work for your application.

View www.time-mark.com. They have schematics for all their models and this will give you a clear idea of one example.

Good Luck,

James

Phase failure relay is an voltage relay.This relay will have set of no/nc contacts.Under normal condition no will become closed contact and nc will become open contact.

With this arrangement further tripping , reclosing etc are arranged by the system designer to suit the requirement.

The breaker can be made to trip through shun trip or under voltage trip through these contacts.

If you want to reclose the breaker after restoration , it is possible through these contacts.

If you want to reset manually it is possible through external auxiliary relay.

A Phase Failure Relay is not a Phase Failure Relay is not a Phase Failure Relay. There is no universal standard by which they all operate. Some are based on voltage, some are based on current, some are both. Some will automatically reset, so will not, some can be programmed either way.

This would be a simple question to answer if you provided a model number and manufacturer of a PFR relay.

There are several possible application situations where you might need to protect your power system for a three phase circuit operating without one of the phases operational.

So both of these questions should be answered to then answer your question.

It is all in the configuration. Is it hard wired, is it an input to a plc which provides lockout or other forms of protection. Most often a PFR operates when one phase is lost by a fuse operating in the MCC. A motor protection relay often has the facility for phase failure detection so it requires more definition before an operational mode can be determined.