POWER SYSTEM PROTECTION FUNDAMENTALS

SESSION 1: POWER SYSTEM FAULTS

• Different types of faults
• Incidence of faults on power system equipment
• Effects of power system faults
• Magnitude of fault current, short circuit calculations
• Detection of faults
• Clearance of faults
• Requirements of protective relaying systems

SESSION 2: SIMPLE CALCULATION OF SHORT CIRCUIT CURRENTS

• Revision of simple formulae
• Calculation of short circuit MVA & fault currents
• Worked examples

SESSION 3: COMPONENTS OF POWER SYSTEM PROTECTION SCHEMES

• Fault detecting relays
• Tripping relays and other auxiliary relays
• Circuit breakers - bulk oil, air-blast, vacuum, SF6
• Current Transformers
• Voltage Transformers
• Ground Transformers
• The transition from electro-mechanical relays to electronic and digital microprocessor-based relays
• The application of programmable logic controllers
• Modern microprocessor-based relays: review of types available

SESSION 4: SYSTEM EARTHING

• Solid, impedance, touch potentials
• Effect of electric shock
• Earth leakage protection

SESSION 5: RELAYS

• Inverse definite minimum time (IDMT) relay
• Construction principles and setting
• Calculation of settings - practical examples
• New Era - modern numerical relays & future trends
• Problems in applying IDMT relays

SESSION 6: CIRCUIT BREAKERS

• Purpose & duty, clearance times, types

SESSION 7: LOW VOLTAGE NETWORKS

• Air & molded circuit breakers
• Construction and installation
• Protection tripping characteristics
• Selective co-ordination (current limiting, earth leakage protection, cascading)

SESSION 8: FEEDER PROTECTION

• Cables
• Pilot wire differential
• Overhead lines
• Distance protection (basic principles, characteristics, various schemes)

SESSION 9: TRANSFORMER PROTECTION

• Phase shift, magnetising in-rush, inter-turn, core & tank faults
• Differential & restricted earth fault schemes
• Bucholz relay, oil & winding temperature
• Oil - testing & gas analysis

SESSION 10: SWITCHGEAR (BUSBAR) PROTECTION

• Requirements, zones, types
• Frame leakage
• Reverse blocking
• High, medium & low impedance schemes

SESSION 11: MOTOR PROTECTION

• Thermal overload, time constraints, early relays, starting & stalling conditions
• Unbalanced supply voltages, negative sequence currents, de-rating factors
• Phase faults protection
• Earth faults - core balance, residual stabilising resistors

SESSION 12: COORDINATION OF ELECTRICAL PROTECTION SYSTEMS

• Fuse to fuse
• Circuit breaker to fuse
• Fuse to circuit breaker
• Back-up protection
• Limitation of fault current
• Selective zones of protection
• Types of bus protection schemes
• Basic concept of differential protection
• Application to various bus configurations
• Applications to switchboards
• Testing of bus protection schemes

9:00AM - 12:00PM

PROTECTION OF ELECTRICAL MOTORS

This presentation explains the fundamentals of motor protection. Every motor is designed for a specific operating temperature depending upon its insulation. Once this limit is exceeded, its life decreases drastically. In this presentation, a brief overview of existing protection philosophy for motors is reviewed with special consideration of thermal protection of motors.

Section No 1:

• Introduction
• Principles of magnetism, basic construction of AC motors and operation of the induction and synchronous motors
• Motor specifications

Section No 2:

• Thermal modeling
• Motor thermal limit curves
• The five key motor thermal modeling elements

Section No 3:

• Differential protection, short circuits and ground faults
• Current unbalance, single phasing, mechanical jam, loss of load
• Undercurrent, underpower, under and overvoltag
• RTDs
• Additional special features

Section No 4:

• Microprocessor Motor Management Relays
• Monitoring, Control and Communication (this is new information and not
• presented before)

12:00PM - 1:00PM - Lunch

1:00PM - 4:00PM

FUSE FUNDAMENTALS

With this presentation, the participant will learn the fundamentals of circuit protection using fuses. There will be a review of overload conditions that exist in an electrical circuit, along with the evolution of fuses in the electrical industry.

The electrical industry started off with using fuse wire for protection, then to the cartridge body. Over time, this fuse became under-rated, and there had to be something better. HRC (high rupture capacity) fuses were adopted for their higher interrupting ratings, and along with these ratings, came greater degree of current limitation. These features allowed for better component and circuit protection.

Motor loads require specific protection schemes. When one looks at the motor control circuit, one finds that the fuse in fact protects the motor control circuit, NOT the motor. However, with time delay fuses, one may actually find back-up overload protection for the motor circuit. Transformers also require specific protection.

Power Semi-conductors require extremely fast acting, low let-thru energy fuses for protection. These semi-conductor devices can be found in Variable Frequency Drives, Soft Starts, or solid state relays. As the variable frequency drive industry evolved, internal DC Bus fuses have been designed out of the drives. However, drives still require input fuse protection.

Arc hazards produce many dangerous issues. This presentation is designed to show what some of these issues may be and how one can limit the issues and dangers associated with arcs, including how fuses can play a role in limiting these dangers.

Topics of discussion include:

• Review (low-voltage fuses)
  
• Overload conditions
  
• Fuse construction & terminology
  
• Fault clearing & current limitation
  
• Coordination
  
• Applications (transformers, feeders, motors)
  
• Motor load protection
  
• Power semi-conductor protection (specifically variable frequency drives & soft starts)
  
• Arc hazards and how to limit exposure to them.

Day 2 Wrap-Up

Course Timetable for Both Days:

• START: 8:00AM
• COFFEE BREAK: 10:00AM
• LUNCH: 12:00PM
• REFRESHMENT BREAK: 2:30PM
• FINISH: 4:30PM