LV/MV/HV Circuit Breakers and Switchgears: Specification, Design, Operation, Inspection, Testing, Maintenance, Repair and Troubleshooting

Introduction

This intensive five-day training is designed to update participants with the latest development of Circuit Breakers and to present some of the more common and updated aspects of low, medium, and high voltage switchgear maintenance. It must be understood that there is an incredible variety of equipment used on low, medium, and high voltage switchgear today. Switchgears play an important role in the distribution and control of electrical power in manufacturing or power plant and in a utility distribution system. Negligent maintenance practices can lead to power system inefficiency and loss of system reliability. An older plant may have switchgear that was built in the forties in the older areas and modern switchgear in other areas as the plant was upgraded. This course will present maintenance problems to the maintenance manager and technician. Newer plants will have the modern equipment of a limited variety and manufacture. It is these similarities that will be covered in the course.

Objectives

By the end of the training, participants will be able to:

• Design, inspect, maintain, repair, and troubleshoot circuit and switchgear
• Apply in-depth knowledge and skills on LV/MV/HV circuit breakers and switchgear
• Describe switchgear details such as ratings, degree of protection, service conditions, and ancillary equipment
• Explain switchgear asset management including CBM and RCM process, tripping devices, maintenance and testing
• Apply load and fault calculation to decide the task of protection system and the operating conditions of the power system
• Explain circuit breaker control circuits, types and application of protective relays, the structure of control circuits, and the use and application of current and voltage transformers
• Discuss circuit breaker characteristics in relation to protection control circuits, selectivity, sensitivity, and speed of the control circuits
• Recognize the value of the earthing system to protection control circuits and the power system protection as well as fault clearance and power redundancy through a control system application
• Identify the various switchgear diagnostic techniques and employ the different types of substation circuit breaker techniques and determine the switchgear vital equipment including batteries condition and monitoring, relay applications for basic complex busbar arrangement, and zone selection logging
• Employ substation maintenance techniques and discuss their description, structures, features, and functions
• Apply the switchgear maintenance practices and improve maintenance and repair procedures
• Carry out maintenance work orders including their process development, procedures and problems encountered
• Introduce computerized maintenance management systems (CMMS) and recognize its importance in circuit breaker design, inspection, maintenance, repair, and troubleshooting

Training Methodology

This is an interactive course. There will be open question and answer sessions, regular group exercises and activities, videos, case studies, and presentations on best practice. Participants will have the opportunity to share with the facilitator and other participants on what works well and not so well for them, as well as work on issues from their own organizations. The online course is conducted online using MS-Teams/ClickMeeting.

Who Should Attend?

This course is intended for all Engineers and other Technical Staff who need a sound understanding of Low, Medium, and High Voltage Switchgear and Circuit Breaker design, inspection, maintenance, repair, and troubleshooting.

Course Outline

DAY 1: GENERAL INTRODUCTION

• 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 SWITCHGEAR

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

DAY 2: CB DESIGN SPECIFICATION BASED ON SHORT CIRCUIT CURRENT LEVEL

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

CB DESIGN SPECIFICATION BASED ON ARC PHENOMENA AND CIRCUIT INTERRUPTION

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

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

• Introduction
• 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 TYPE OF CIRCUIT BREAKERS

• 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 o Blast air CB
• 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
• DC Circuit Breakers o Construction o Methods of interruption
  • Application

DAY 5: CIRCUIT BREAKER INSPECTION, MAINTENANCE, AND SERVICES

• Inspection
• General inspection technical procedure
• Daily inspection of circuit breakers
• The 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
• One-hour Video, 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 b) Phase terminals of a pole
• The resistance between Terminals of the Pole too high (above 100 microhms) (15 micro-ohms per joint) contact
• Unequal contact Wipe and Travel in 3-pole Measured from the 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)