Workshop on Circuit Breakers & Switchgears: Operations & Maintenance

Course overview:

Switchgear & Circuit Breakers are critical components in electrical distribution systems, control of electrical power in manufacturing or power plant and in a utility distribution system. Switchgear is used for controlling, regulating and switching on or off the electrical circuit in the electrical power system. The switches, fuses, circuit breaker, isolator, relays, current and potential transformer, indicating instrument, lightning arresters and control panels are examples of the switchgear devices.

The switchgear system is directly linked to the supply system. It is placed in both the high and low voltage side of the power transformer. It is used for de-energizing the equipment for testing and maintenance and for clearing the fault.

Lack of good maintenance practices can lead to power system inefficiency and loss of system reliability.

This workshop is designed to update participants with the latest development of Circuit Breakers operations and maintenance for power system efficiency and reliability.

For whom:

This course is designed for Maintenance Engineers and Supervisors, Project Engineers, Junior graduated Electrical Engineers, Electrical Foreman’s and Technicians. Engineers in inspection, materials, safety, and electrical maintenance team will equally benefit from this program.

Learning objectives:

At the end of the program, participants will be able to:

• describe switch gear construction;
• describe the four basic types of medium voltage circuit breakers;
• read MV CB nameplate and select circuit breaker specifications;
• explain the arc phenomena and circuit interruption;
• list and explain the different types of circuit breakers and industrial switch gears;
• develop the maintenance procedures;
• operate and maintain MV circuit breakers;
• carry out various tests on MV CBs (type/routine/special and field tests);
• manage work related issues such as risk and safety; and
• develop safe working practices.

Course outline:

Day 1 Industrial Switchgear & Circuit Breakers: An overview

• Electrical engineering basic concepts
• Three phase review and per unit
• Voltage levels
• One line and three-line diagram
• Generation system layout
• Transmission system layout
• Substation system layout
• Distribution system layout

Industrial Switchgears

• Fuses
• Auto-reclosers
• Automatic sectionalize
• Circuit Breakers
• Isolator switches
• Load switches
• Relays
• Current transformers
• Voltage transformers

Day 2: CB Design Specification Based on Short Circuit Current Level

• Faults on power systems
• Transient phenomena in power system
• Symmetrical component analysis of three phase network
• Network connection for various fault types
• PU system
• Current and voltage distribution in system due to a fault
• Effect of system on zero sequence quantities
• MVA method
• Computer programs based short circuit calculation.

CB Design Specification Based on Arc Phenomena and Circuit Interruption and Safe Operation

• Arc phenomena
• Maintenance of the Arc
• Properties of Arc
• Arc Interruption theory
• Circuit Breaker Rating
• Circuit constants and circuit conditions
• Conditions of severity
• Restriking voltage transient
• Class A ultra-fast transients
• Class B system transients
• Class C low transients
• Transmission line transient
• Switching transients
• Duties of Switchgear

Safety Policies & Electrical Hazards

• Safety rules
• Authorization levels
• Safety documents
• Hazardous associated with electrical equipment
• Electrical hazards & Shock to human
• Arc Flashing hazards (IEEE 1584)
• Incident energy
• Boundary distances
• Labeling
• PPE
• Approved & Standard organizations

Day 3: LV Circuit Breakers

• Low voltage molded case current limiting circuit breakers
• Low voltage molded case circuit breakers with high breaking capacity
• Insulated case circuit breakers
• Low voltage air circuit breakers
• Low voltage circuit breakers specification

Modern MV and HV Vacuum CB

• Advantages of vacuum interruption
• Vacuum contactors and interrupters
• The vacuum medium
• The vacuum arc
• Vacuum arc stability
• Vacuum break down
• Vacuum switch construction
• Applications of vacuum circuit breakers

Modern MV and HV SF6 CB Introduction

• Basic Features of SF6 Breakers
• Dielectric properties of SF6
• Quenching properties of SF6
• Construction of SF6 breaker
• SF6 CB types
• Puffer type SF6 breakers
• Double Pressure System
• Single Pressure Puffer-Piston System
• Single Pressure Self Blast System
• Improvement in SF6 Breakers for HV

Day 4: Other Types of Circuit Breakers

1. a) Air Circuit Breakers

• Method of increasing arc resistance
• Plan break type
• Magnetic blow out type
• Arc splitter type
• Application
• Construction and operation
• Axial air CB
• Blast air CB

1. b) Oil Circuit Breakers

• Arc rupture under oil
• Advantages of oil
• Disadvantages of oil
• Plan break oil circuit breakers
• Arc control circuit oil breakers
• Minimum oil circuit breakers
• Construction and operation

1. c) Dc Circuit Breakers

• Construction
• Methods of interruption
• Application

Day 5: Circuit Breaker Inspection, Maintenance and Services

• Inspection
• General inspection technical procedure
• Daily inspection of circuit breakers
• Monthly inspection of circuit breakers
• Annual inspection of circuit breakers
• Disassembly
• Cleaning
• Tightening
• Lubrication
• Equipment’s used in testing
• Testing procedure
• Direct testing
• Contact resistance test
• Insulation resistance test
• Test report
• Indirect testing
• Video playback on HV CB Maintenance and Repair)

Circuit Breakers Control, Protection and Testing

• Switchgears control devices and wiring
• Switchgears protection devices and wiring
• Testing Classification
• Testing laboratories
• Description of a simple testing station

CB Troubleshooting

• Low insulation Resistance (below 2000 Mega-ohms)

between a) Phase terminal and earthed frame,

with breaker closed

1. b) Phase terminals of a pole

• Resistance between Terminals of Pole too high (above 100 microhms) (15 micro-ohm per joint) contact
• Unequal contact Wipe and Travel in 3-pole Measured from top surface of interrupter flange and the contact lip by a simple rod with a) breaker open and b) breaker closed
• One of the pole docs not close
• Breaker operation too Slow During opening timing from trip command to contact separation instant too large (60 ms instead of say 40 ms)

Training Methodology

Lectures, discussions, exercises, and case studies will be used to reinforce these teaching/learning methods.