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49 - LONG - Long-Term Programs

LONG 506 - Electric Substation Design and Electrical Protraction Systems (52 Weeks)



Course Description

This program is designed to provide an introductory for the fundamentals of the electrical, civil, structural design issues of electric power substations. The program also it will address a complete variety of substation design subjects. It will also discuss application, installation, maintenance and testing issues related to low, medium and high-voltage switchgear and electrical circuit breaker equipment. Additionally the course will provide fundamentals on protection, relay design and protection schemes for transmission lines and transformers

Course Objectives

  • Understanding of substation technology and modern substation design practices
  • Understanding the importance of preventive maintenance check and servicing of the various types of circuit breakers
  • Implementing safe electrical systems of work and operations
  • Understanding the fundamentals of electrical power protection and applications
  • Recognizing the different fault types
  • Performing simple fault and design calculations
  • Understanding protection system components

Course Details/Schedule

Week 1

Electrical Substations, Power Systems, and Deregulation

  • Structure of the electric power system overview
  • Systems for distribution of power
  • Classifications
  • Equipment definitions
  • Design principles

Substation Project Chronology

  • Workflow and project sequence
  • Site identification and acquisition
  • Engineering design, drawings and documentation
  • Construction, testing and commissioning

Developing the Scope/Identifying the Constraints for the Overall Project

  • Safety
  • Power requirements
  • Site constraints
  • Atmospheric
  • Environmental community and societal influences

Costs and Schedules

  • Costs and financial analysis
  • Schedules and impacts

Site Grading Design

  • Substation grade types
  • Drainage and erosion protection
  • Oil spill containment


  • Slab on grade and others
  • Design Techniques
  • Open air
  • Metal clad switchgear
  • Gas insulated subs/SF6

Bus Configurations & Conductor

  • Types of common configurations
  • Reliability criteria


  • Insulation protection and shielding
  • Clearance
  • Surge arresters


  • Need for grounding
  • Personnel safety
  • Hazardous potentials during faults


  • Materials
  • Design options and considerations
  • Finishes

Principle Equipment

  • General specifications and ratings
  • Transformers
  • Core, winding configuration
  • Tap changers
  • Specifications

Circuit Breakers/Switches

  • Design and purpose

Ancillary Equipment

  • Potential transformers
  • Current transformers

Substation Auxiliary Systems

  • Necessity
  • AC station power
  • DC and battery power


Week 2

Introduction - reasons for faults - and classification of faults

  • Distinction between load and fault current
  • Sources of short-circuit current
  • Introduction to fault calculations
  • Balanced and unbalanced faults

Overview of Power System Protection

  • Measurement - voltage and current transformers
  • Protective device characteristics
  • Types of protection systems
  • The role and importance of the circuit breaker in power systems

Overview of types of circuit breaker

  • Air-Break
  • Vacuum
  • Gas
  • Other related switching devices
  • The single-line diagram
  • Substation layouts


  • Principles of arc extinction
  • D.C. circuit breaking
  • A.C. circuit breaking
  • Contacts and arc initiation
  • Arc chutes
  • Performance characteristics
  • General construction Principles


  • History – The early years
  • The vacuum arc – An overview
  • Current interruption in vacuum
  • Methods of keeping the arc diffuse
  • Current chopping – general implications
  • Vacuum interrupters in series
  • Design of vacuum switchgear
  • Maintenance and testing requirements

SF6 Gas

  • Properties of SF6
  • Principles of arc extinction
  • Features and construction
  • Mechanism principles
  • Insulation principles
  • Gas leak problems
  • Specific supervision requirements
  • Circuit power factor considerations
  • Maintenance and testing requirements

International Standards

  • Importance and relevance to specifications
  • ANSI and IEEE
  • IIEC and IEE

Circuit breakers and power system

  • Circuit breaker failure and the effects on power system operation
  • Circuit breaker inspection, testing and maintenance program
  • The Principles of modern substation control systems
  • Power circuit breaker maintenance

Importance of adequate maintenance


Maintenance of molded case circuit breakers

  • Frequency of maintenance
  • Routine maintenance tests

Maintenance of Iow-voltage circuit breakers

  • Frequency of maintenance
  • Maintenance procedures

Maintenance of medium-voltage circuit breakers

  • Frequency of maintenance
  • Safety practices
  • Maintenance procedures for medium-voltage air circuit breakers
  • Maintenance procedures for medium-voltage oil circuit breakers
  • Maintenance procedures for medium-voltage vacuum circuit breakers

Maintenance of high-voltage circuit breakers

  • Frequency of inspections
  • External inspection guidelines
  • Internal inspection guidelines
  • Typical internal breaker problems
  • Influence of duty imposed

Maintenance of SF6 gas circuit breakers

  • Properties of SF6 (sulfur hexafluoride) gas
  • Handling nonfaulted SF6
  • Handling faulted SF6

Week 3

Power System Overview

  • Electrical distribution system
  • Reading single line diagrams
  • LV, MV AND HV equipment
  • Function and types of electrical switchgear
  • Basic circuit breaker design

Basics of Power System Protection

  • Need for protective apparatus
  • Basic requirements and components

Types of Faults and Short Circuit Current Calculations

  • The development of simple distribution systems
  • Faults-types, effects and calculations
  • Equivalent diagrams for reduction of system impedance
  • Calculation of short circuit MVA
  • Unbalanced faults and earth faults
  • Symmetrical components

System Earthing and Earth Fault Current

  • Phase and earth faults
  • Comparison of earthing methods
  • Protective earthing
  • Effect of electric shock on human beings
  • Sensitive earth leakage protection
  • System classification

Fuses and Circuit Breakers with Builtin Protection

  • Fuse operating characteristics, ratings and selection
  • Energy 'let through'
  • General rules of thumb
  • IS-limiter
  • Circuit breakers - types, purpose and arc quenching
  • Behavior under fault conditions
  • Protective relay-circuit breaker combination
  • Circuit breakers with in-built protection
  • Conventional and electronic releases

Instrument Transformers Transformer ratio and errors of ratio and phase angle

  • 'Class' of instrument transformers
  • Voltage and current transformers
  • Applications

Relays and Auxiliary Power Equipment

  • Principle of construction and operation of protective relays
  • Special focus on IDMTL relays
  • Factors influencing choice of plug setting
  • The new era in protection - microprocessor, static and traditional
  • Universal microprocessor overcurrent relay
  • Technical features of a modern microprocessor relay
  • Future of protection for distribution systems
  • The era of the IED
  • Substation automation
  • Communication capability
  • Need for reliable auxiliary power for protection systems
  • Batteries and battery chargers
  • Trip circuit supervision
  • Why breakers and contactors fail to trip
  • Capacity storage trip units

Protection Grading and Relay Coordination

  • Protection design parameters on MV and LV networks
  • Coordination - basis of selectivity
  • Current, time and earth fault grading
  • Time-current grading
  • Grading through IDMT protection relay
  • Coordination between secondary and primary circuits of transformers
  • Current transformers - coordination
  • Importance of settings and coordination curves

Unit Protection and Applications

  • Protective relay systems
  • Main, unit and back-up protection
  • Methods of obtaining selectivity
  • Differential protection
  • Machine, transformer and switchgear differential protection
  • Feeder pilot-wire protection
  • Time taken to clear faults
  • Unit protection systems - recommendations and advantages

Protection of Feeders and Lines

  • Over current and earth fault protection
  • Application of DMT/IDMT protections for radial feeders
  • Directional over current relays in line protection
  • DMT and IDMT schemes applied to large systems
  • Unit and impedance protection of lines
  • Use of carrier signals in line protections
  • Transient faults and use of auto reclosing as a means of reducing outage time
  • Auto-reclosing in circuits with customer-owned generation
  • Auto-reclosing relays for transmission and distribution lines

Protection of Transformers

  • Winding polarity
  • Transformer connections and magnetizing characteristics
  • In-rush current
  • Neutral earthing
  • On-load tap changers
  • Mismatch of current transformers
  • Types of faults
  • Differential protection
  • Restricted earth fault
  • HV overcurrent
  • Protection by gas sensing and pressure detection
  • Overloading

Protection of Rotating Machinery

  • Motor protection basics
  • Transient and steady state temperature rise
  • Thermal time constant
  • Motor current during start and stall conditions
  • Stalling of motors
  • Unbalanced supply voltages and rotor failures
  • Electrical faults in stator windings earth fault phase-phase faults
  • Typical protective settings for motors
  • An introduction to generator protection