Power System Protection
Introductory treatment of protective-relaying theory and practical application for electric-power systems. The course develops protection zones, primary and backup schemes, instrument-transformer behavior, symmetrical-component fault analysis, equipment modeling, and relay applications for buses, transformers, transmission lines, shunt equipment, distribution feeders, generators, and motors, including breaker-failure protection, automatic reclosing, and restoration.
Objectives
- Describe the roles of primary, backup, and redundant protective-relaying schemes.
- Identify and coordinate zones of protection for substations and power-system equipment.
- Select appropriate current-transformer and voltage-transformer inputs for protection schemes.
- Calculate fault currents for balanced and unbalanced faults using per-unit quantities, symmetrical components, and sequence networks.
- Model generators, transformers, transmission lines, and shunt equipment for fault studies.
- Develop metering and relaying diagrams that show instrument-transformer connections, protection zones, redundancy, and fault isolation.
- Apply and set high-impedance and low-impedance differential protection for power-system buses.
- Apply differential, overcurrent, and overexcitation protection to power transformers.
- Apply distance, overcurrent, differential, and pilot protection to transmission lines.
- Select fuses, reclosers, sectionalizers, and relays for distribution-feeder protection and coordination.
- Apply protection schemes to shunt reactors and shunt capacitor banks.
- Select protection functions for generators, induction motors, and synchronous motors.
- Explain breaker-failure protection, automatic reclosing, high-speed reclosing, and synchronism-check restoration.
Textbooks
Protection & Automation Application Guide
Michael Bamber, Michael Bergstrom, Andrew Darby, Susan Darby, Graham Elliott, Peter Harding, Graeme Lloyd, Alan Marshall, Allen Millard, Andrew Myatt, Philip Newman, Anthony Perks, Stephen Potts, Simon Richards, Jack Royle, Peter Rush, Brendan Smith, Mark Stockton, Abraham Varghese, Paul Wilkinson, Alan Wixon, John Wright · GE Grid Solutions
Modules
Description: Introduces major power-system equipment, normal and abnormal operating conditions, the purpose of protective relaying, fault isolation, primary and backup protection, circuit-breaker operation, station DC supplies, and the current and voltage inputs used by relays.
Description: Develops protection zones and zone overlap, unit and non-unit protection, relay operating quantities and technologies, ANSI device numbers, metering and relaying diagrams, redundancy, sensitivity, selectivity, security, reliability, and automatic restoration.
Description: Introduces current-transformer construction and operation, bushing and free-standing CTs, transformer ratios and burden, metering and protection classes, accuracy ratings, C-class voltage ratings, rating factors, taps, and CT selection for relaying applications.
Description: Examines CT transient response during faults, DC offset, core flux and saturation, saturation-avoidance calculations, the effects of burden and tap selection, and the application of linear couplers, voltage transformers, and capacitively coupled voltage transformers.
Description: Reviews phasor representation and complex arithmetic, the j and a operators, balanced three-phase voltage and current relationships, per-unit and percent quantities, impedance-network reduction, and the motivation for symmetrical components.
Description: Develops positive-, negative-, and zero-sequence components, transformations between phase and sequence quantities, sequence representations of voltages and currents, and the use of symmetrical components to analyze unbalanced systems.
Description: Builds sequence-impedance models for transmission lines, shunt capacitors and reactors, transformers with different winding and grounding configurations, synchronous generators, motors, and other rotating equipment.
Description: Applies per-unit conversion and sequence-network construction to a three-bus system with generators, transformers, transmission equipment, and grounding impedances, then uses the resulting network models for fault-current calculations.
Description: Surveys bus arrangements and their protection implications, establishes bus differential zones from CT and breaker locations, develops CT polarity and differential-current connections, and explains how external-fault CT saturation can create false operating current.
Description: Develops high-impedance differential protection with stabilizing resistors and voltage limits, low-impedance percentage-biased differential protection, restraint and slope settings, CT saturation security, directional supervision, and modern numerical bus relays.
Description: Introduces transformer failure modes and differential protection, CT ratio and phase compensation, percentage restraint, magnetizing inrush and harmonic restraint, and the special current relationships created by delta-wye transformer connections.
Description: Applies CT connections and vector-group compensation to transformer differential schemes, develops tap and auxiliary-CT calculations, and shows how numerical relays perform ratio, phase-shift, and zero-sequence compensation through settings.
Description: Reviews overhead and underground transmission construction, conductor characteristics, resistance and inductance, Carson earth-return relationships, and the calculation of positive- and zero-sequence line impedances used in relay settings.
Description: Compares current-differential and non-unit line protection, communication channels, phase comparison, directional overcurrent relaying, and the impedance and R-X concepts that lead to distance-relay characteristics.
Description: Develops distance-relay voltage and current inputs, primary-to-secondary impedance conversion, phase and ground fault loops, zero-sequence compensation, measurement errors, stepped-distance zones, and underreaching and overreaching settings.
Description: Examines zone coordination and end-zone faults, then develops communication-aided pilot schemes including direct and permissive transfer tripping, permissive overreach, directional comparison blocking, and the security and dependability of their channels.
Description: Develops local breaker-failure backup logic, current detectors, initiate signals, timers, retrip and adjacent-breaker tripping, then examines automatic reclosing, dead time, high-speed reclose, synchronism checks, and restoration constraints.
Description: Explains reactive compensation, long-line voltage behavior and surge-impedance loading, shunt-reactor and capacitor applications, equipment types and connections, grounding, switching, and the protection considerations for shunt reactors.
Description: Develops system and bank protection for externally fused, internally fused, and fuseless capacitor banks, including unit overvoltage capability, voltage-differential schemes, tap-PT calculations, fuse-loss detection, unbalance protection, and bank relay settings.
Description: Introduces radial distribution configurations and feeder impedances, then applies expulsion and current-limiting fuses, reclosers, sectionalizers, breakers, phase and ground overcurrent relays, and time-current coordination to distribution protection and restoration.
Description: Covers synchronous-generator construction, system connections and grounding, fault-current behavior, stator and field protection, abnormal frequency and volts-per-hertz protection, reverse power, inadvertent energization, negative sequence, loss of field, and loss of synchronism.
Description: Applies protection to induction and synchronous motors, including voltage and frequency limits, stalling, overload and thermal protection, locked-rotor conditions, phase unbalance and sequence protection, loss of synchronism, and safe motor re-energization.