Circuit Breaker Failure Protection Scheme

How CBF is implemented in Substations, Power Plants & Electrical Systems

What you'll learn
What are different types of breaker failure that can occur in power system
Circuit Breaker Failure due to Mechanism Fail
Circuit Breaker Failure due to non-interruption of fault current
Circuit Breaker Failure due to DC control/trip supply fail
Circuit Breaker Failure due to tripping coil failure
Circuit Breaker Failure due to low DC voltage
Circuit Breaker Failure due to Aux contact failure
Circuit Breaker Failure due to Fire
Circuit Breaker Failure due to delayed tripping
Circuit Breaker Pole Discrepancy
What is Circuit Breaker Pole Discrepancy
Single pole & three pole circuit breaker operated mechanisms
advantages of single pole tripping & reclosing
How single pole reclosing support system
What is meaning of pole discrepancy
How pole discrepancy is detected in system
Pole discrepancy circuit working
Timer circuit in pole discrepancy
Stage 1 & Stage 2 operations of pole discrepancy
Pole discrepancy during closing command & tripping command.
Re-trip and 2nd stage
What is typical time settings for Pole discrepancy
Creation of 3I0 zero sequence current during pole discrepancy condition
How Pole Discrepancy can lead to indiscriminate tripping in the network
Busbar Schemes
Single Bus Single Breaker Scheme, Double bus single breaker scheme, one and half breaker scheme, double bus double breaker scheme, mesh breaker scheme
How to change over load from one bus to another bus without interruption, advantages of different busbar scheme
Circuit Breaker Fail Philosophy
Circuit breaker failure protection using relay coordination at low / MV levels
What to do & protect if one breaker fail
Understand basic concept of breaker failure, if some one understand well can design and understand all CBF protection schemes & logic
CBF protection example in one and half breaker scheme, how to protect system if middle breaker fail
How to protect system if main breaker fail. CBF protection example in double bus double breaker busbar, consider the case of bus coupler & bus sectionalizer.
Circuit Breaker Failure logic block, CBF initiation function, CBF current guard, CBF Low current mode, CBF CB Aux contact input,
CBF timer, CBF stage 1 & Stage 2, CBF for Mechanical Protection not involving current, CBF protection and End fault protection
CBF Re-trip & 2nd stage faulty CB isolation from sources
CBF when Circuit Breaker is faulty
CBF and lockout function, 86 close block relay
Description
The circuit breaker failure protection provides a backup protection in the case, that the local circuit breaker fails to clear a system fault.

In this training we have started from basic concepts, explained circuit breaker symbol and how circuit breaker look like in substation. We have discussed in training how to represent circuit breaker by ANSI code, difference of circuit breaker and line isolator. What are different functions that are performed by circuit breaker, what is arc, how to quench arc, what are media to quench arc, what will happen if arc is not quenched.

We have discussed different components of circuit breaker that include CB closing coil, tripping coils, auxiliary contacts, normally open and normally close contacts, simplified protection system consisting of DC battery banks/charger, relays, Current and voltage transformers, why CT & VTs are required at substation, what do you understand by CT ratio 1000/1, use of redundant DC supplies, why DC is used not AC for control & trip functions, how circuit breaker spring is charge, circuit breaker operation, what is trip free/ready to trip function of CB, Trip Circuit Supervision feature, DC supply supervision, trip coil supervision, TCS Relay, control & protection DC supplies & Tripping coils, what is typical tripping and closing time of circuit breaker.

What are different types of breaker failure that can occur in power system

Circuit Breaker Failure due to Mechanism Fail

Circuit Breaker Failure due to non-interruption of fault current

Circuit Breaker Failure due to DC control/trip supply fail

Circuit Breaker Failure due to tripping coil failure

Circuit Breaker Failure due to low DC voltage

Circuit Breaker Failure due to Aux contact failure

Circuit Breaker Failure due to Fire

Circuit Breaker Failure due to delayed tripping

Circuit Breaker Pole Discrepancy

What is Circuit Breaker Pole Discrepancy

Single pole & three pole circuit breaker operated mechanisms

advantages of single pole tripping & reclosing

How single pole reclosing support system

What is meaning of pole discrepancy

How pole discrepancy is detected in system

Pole discrepancy circuit working

Timer circuit in pole discrepancy

Stage 1 & Stage 2 operations of pole discrepancy

Pole discrepancy during closing command & tripping command.

Re-trip and 2nd stage

What is typical time settings for Pole discrepancy

Creation of 3I0 zero sequence current during pole discrepancy condition

How Pole Discrepancy can lead to indiscriminate tripping in the network

Busbar Schemes

In order to understand it is good idea to learn about busbar schemes, we will go through following busbar schemes.

Single Bus Single Breaker Scheme

Double Bus Single Breaker Scheme

One and half breaker scheme

Mesh Breaker schemes

double bus and double breaker

How to change over load from one bus to another bus without interruption

Advantages of different busbar scheme

Circuit Breaker Fail Philosophy

Circuit breaker failure protection using relay coordination at low / MV levels

What to do & protect if one breaker fail

Understand basic concept of breaker failure, if some one understand well can design and understand all CBF protection schemes & logic

CBF protection example in one and half breaker scheme, how to protect system if middle breaker fail , How to protect system if main breaker fail.

CBF protection example in double bus double breaker busbar, consider the case of bus coupler & bus sectionalizer.

Circuit Breaker Failure Logic, Function

Circuit Breaker Failure logic block

CBF initiation function

CBF current guard

CBF Low current mode

CBF CB Aux contact input

CBF timer

CBF stage 1 & Stage 2

CBF for Mechanical Protection not involving current

CBF protection and End fault protection

CBF Re-trip & 2nd stage faulty CB isolation from sources

CBF when Circuit Breaker is faulty

CBF and lockout function, 86 close block relay

CBF & CB close blocking

CBF typical times for stage 1 & stage 2 & when CB faulty

By completing this course you will be able to understand circuit breaker failure relay function, Circuit breaker failure scheme/trip matrix, how CBF stage 1 & 2 operate, CBF protection for different busbar schemes.

I wish you best of luck for the course.

Best Regard

Elite Engineering

Who this course is for
Engineers, students and field technicians