Additional Protection Options; Breaker Failure Protection; Mode Of Operation - ABB RELION REB500 Operation Manual

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Table Of Contents

Table of Contents

1MRK 505 400-UEN B

Section 6

6.1

Breaker failure protection

6.1.1

Mode of operation

The circuit-breaker is the last and most important link in the protection chain. The purpose of

BFP is to take the right action should the circuit-breaker fail to execute a trip command. This

involves tripping the circuit-breakers surrounding the fault, which are mainly in the same

station, but may also include circuit-breakers at the remote ends of lines (intertripping).

The principle of BFP is based on monitoring the time the fault persists after a trip command

has been issued to the circuit-breaker (starting of BFP has been enabled by the main

protection, for example, feeder protection).

A complete block diagram of BFP, including additional functions such as initiation logics and

I0-measurement, is shown in

The following internal REB500 functions can start the breaker failure function in all three

phases:

•

REB500 intertripping system (such as, BBP and BFP)

•

An external trip command

•

Time-overcurrent if logic 3 is configured

•

Breaker pole discrepancy protection if logic 3 is configured

BFP can be started phase-selectively via two separate inputs. All three phases can be started

via up to six different inputs and the currents of all three phases monitored.

It is recommended to adjust the pick-up current of the phase measurement such that I

Kmin

This setting applies to phase faults und ground faults as well under the condition that I

reflects the minimal short circuit current out of these fault types. In certain cases, the ground

fault current may be much lower than the phase fault value (for example, low resistive

grounded networks). Under such exceptional cases, the BFP I0 (adjusted with a lower pickup

value) can be used in addition to the breaker failure phase system (see

Operation of BFP can also be started by the internal signals. These internal signals are shown

with the following symbol

and the outputs on the right.

Distributed busbar protection REB500

Technical manual