This professional development course is designed for engineers and technicians who need practical skills and knowledge in understanding power system protection, including how to calculate fault currents, and select relays and associated instrument transformers appropriate to each typical system or equipment.
At a glance
- 3 Months
- Professional Certificate
Any power system is prone to ‘faults’ (also called short-circuits), which occur mostly as a result of insulation failure and sometimes due to external causes. When a fault occurs, the normal functioning of the system gets disturbed. The high current resulting from a fault can stress the electrical conductors and connected equipment thermally and electro-dynamically.
Arcs at the fault point can cause serious or even fatal burn injuries to operating and maintenance workers in the vicinity. Faults involving one phase and ground give rise to high ‘touch’ and ‘step’ voltages, posing the danger of electrocution to personnel working nearby.
It is, therefore, necessary to detect and clear any fault quickly. The first device used in early electrical systems was the fuse, which acted both as the sensor and the interrupting device. With larger systems, separate devices have become necessary to sense and interrupt fault currents
In both high voltage systems and low voltage systems of higher capacities, the sensing is done by more sophisticated devices called relays. Relays were initially electro-mechanical devices, but static relays, and more recently, digital relays, have become the norm. With more complex systems, it is necessary to detect the point of fault precisely and trip only those sections affected by the fault, while the rest of the system can continue to function normally.
In the event of the nearest circuit breaker failing to operate, the next breaker in the upstream (feeding) side has to be tripped as a ‘back up’ measure. Another requirement is to minimize the time for which a fault remains in the circuit; this is necessary to reduce equipment damage and the danger to operating personnel.
These requirements necessitate different forms of relaying apart from the simple current sensing relays. Equipment such as generators, transformers, and motors also need special forms of protection characterized by their design and operating principles.
This course will explain all of these points in detail and provide you with the skills and knowledge necessary to calculate fault currents, and select relays and associated instrument transformers appropriate to each typical system or equipment. You will also learn how to adjust the setting of the relays so that the relays closest to the fault will operate and clear the fault faster than the backup devices.
The course is composed of 12 modules, covering the fundamentals of electrical power protection and applications, how to recognize the different fault types, protection system components, performing simple fault and design calculations, performing simple relay settings, and choosing appropriate protective devices for various equipment.
It will also teach you how to interpret the protection systems existing in your plant, understand their functions, detect any shortcomings, and explain any undesired or uncoordinated relay operation.
Module 1: 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
Module 2: Basics of Power System Protection
- Need for protective apparatus
- Basic requirements and components
Module 3: 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
Module 4: 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
Module 5: Fuses and Circuit Breakers With Builtin Protection
- Fuse operating characteristics, ratings and selection
- Energy ‘let through’
- General rules of thumb
- 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
Module 6: Instrument Transformers Transformer Ratio and Errors of Ratio and Phase Angle
- ‘Class’ of instrument transformers
- Voltage and current transformers
Module 7: Relays and Auxiliary Power Equipment
- Principle of construction and operation of protective relays
- Special focus on IDMTL relays
- Factors influencing the 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
Module 8: Protection Grading and Relay Coordination
- Protection design parameters on MV and LV networks
- Coordination – the 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
Module 9: 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
Module 10: Protection of Feeders and Lines
- Over-current and earth fault protection
- Application of DMT/IDMT protection for radial feeders
- Directional overcurrent 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
Module 11: 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
Module 12: 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
To obtain a certificate of completion for EIT’s Professional Certificate of Competency, students must achieve a 65% attendance rate at the live, online fortnightly webinars. Detailed summaries/notes can be submitted in lieu of attendance. In addition, students must obtain a mark of 60% in the set assignments which could take the form of written assignments and practical assignments. Students must also obtain a mark of 100% in quizzes. If a student does not achieve the required score, they will be given an opportunity to resubmit the assignment to obtain the required score.
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You are expected to spend approximately 5-8 hours per week learning the course content. This includes attending fortnightly webinars that run for about 90 minutes to facilitate class discussion and allow you to ask questions. This professional development program is delivered online and has been designed to fit around full-time work. It will take three months to complete.
Registrations are open for our upcoming intakes. Please ensure you book your place at least one week before the start date of the program.
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