Improve Failure Detection and Optimize Protection
In the ever-evolving field of protective relay technology, an engineer’s personal preference and professional judgment are as important to power system protection as the physical relays used to detect and isolate abnormal conditions.
Invaluable Insights from an Experienced Expert
Protective Relay Principles focuses on probable power system failure modes and the important characteristics of the protective relays used to detect these postulated failures. The book presents useful new concepts in a way that is easier to understand because they are equally relevant to older, electromechanical and solid-state relays, and newer, more versatile microprocessor-based relays. It introduces the applications, considerations, and setting philosophies used in transmission-line, distribution-line, and substation applications, covering concepts associated with general system operations and fault detection. Topics include relay load limits, cold load pickup, voltage recovery, and arc flash. The author also delves into the philosophies that engineers employ in both urban and rural areas, with a detailed consideration of setpoint function.
Analysis of Key Concepts That Are Usually Just Glossed Over
This versatile text is ideal for new engineers to use as a tutorial before they open the instruction manuals that accompany multi-function microprocessor-based relays. Guiding readers through the transient loading conditions that can result in relay misoperation, the author elaborates on concepts that are not generally discussed, but can be very helpful in specific applications. Readers will come away with an excellent grasp of important design considerations for working with overcurrent, over- and undervoltage, impedance, distance, and differential type relay functions, either individually or in combination. Also useful for students as a textbook, this book includes practical examples for many applications, and offers guidance for more unusual ones.
Power System Components
Transmission Lines
Distribution Lines
Transformers
Circuit Breakers
Buses
Switchyards
Fuses
Substations
Reclosers
Generators
Power System Subcomponents
Current Transformers
Voltage Transformers
Capacitive Coupled Voltage Transformers
Protective Relays
Control Relays
Master Trip Relays
Programmable Logic Controllers
Insulators
Bushings
Cable Terminators
Disconnect Switches
Air Break Switches
Motor-Operated Air Break Switches
Ground Switches
Surge Arrestors
Sectionalizers
Batteries
Abnormal Power System Conditions
Short Circuits
Overloads
Overvoltage
Undervoltage
Overfrequency
Underfrequency
Open Phase
Single Phasing
Phase Unbalance
Volts per Hertz
Short-Circuit Calculations
Symmetrical Components
Positive Sequence Networks
Negative Sequence Networks
Zero Sequence Networks
Operators
Sequence Diagram Connections—Three-Phase Faults
Sequence Diagram Connections—Phase-to-Phase Faults
Sequence Diagram Connections—Single Phase-to-Ground Faults
Per-Unit Quantities
Sample Calculations
Sample Calculations—Three-Phase Faults
Sample Calculations—Phase-to-Phase Faults
Sample Calculations—Single Phase-to-Ground Faults
Sample Calculations—Mutual Coupling
Protective Relay Functions
Time Overcurrent Relay (51)
Instantaneous Overcurrent Relay (50)
Overvoltage Relay (59)
Undervoltage Relay (27)
Distance Relay (21)
Differential Relay (87)
Directional Relay (67)
Underfrequency Relay (81)
Overfrequency Relay (81)
Protective Relay Functional Combinations
Voltage-Controlled Time Overcurrent Relay
Torque-Controlled Time Overcurrent Relay
Logic-Controlled Instantaneous Overcurrent Relay
Torque-Controlled Instantaneous Overcurrent Relay
Logic-Controlled Overvoltage Relay
Logic-Controlled Undervoltage Relay
Logic-Controlled Distance Relay
Current-Supervised Distance Relay
Logic-Supervised Differential Relay
Current-Supervised Differential Relay
Current-Supervised Underfrequency Relay
Dual Underfrequency Relays
Zones and Regions of Protection
Zones of Protection
Regions of Protection
Physical Characteristics of Protective Relays
Electromechanical Relays
Solid-State Relays
Microprocessor-Based Relays
Relay Operation
Relay Packaging
Setting Considerations
Power System Configuration and Operation
Power System Requirements
Maximum Short-Circuit Current—Fault in Protected Zone
Maximum Relay Short-Circuit Current—Fault in Adjacent Zone
Minimum Relay Short-Circuit Current—Fault in Protected Zone
Fault Current Ratio
Relay Sensitivity
Circuit Loading
Relay Coordination
Directionality
Accuracy of Calculations
Device Accuracy
Circuit-Breaker Operating Times
Transient Overreach
Cold Load Inrush
Redundancy
Relay Drift
Security
Arc Flash Hazard
Circuit Breaker-Failure Detection and Isolation
Free-Standing CT Flashover Detection
Switchable Settings
Recovery Voltage Inrush
Protection and Control Schemes
Alternative Protective Relay Trip Logic
Supervised Protective Relay Logic
Protective Relay Coordination
Instantaneous Current Relays
Time Overcurrent Relays
Instantaneous Voltage Relays
Time-Delayed Voltage Relays
Instantaneous (Zone 1) Impedance Relays
Time-Delayed (Zone 2 or Zone 3) Impedance Relays
Instantaneous Frequency Relays
Time-Delayed Frequency Relays
Distribution-Line Protection: Radial Lines
Distribution-Line Protection Philosophy
Setpoint Margin Considerations
Distribution-Line Protection
Time Overcurrent Phase Relay Pickup Setting—Load Capability
Time Overcurrent Ground Relay Pickup Setting—Load Capability
Low Set Instantaneous Overcurrent Phase Relay Pickup Setting
Low-Set Instantaneous Overcurrent Ground Relay Pickup Setting
High-Set Instantaneous Overcurrent Phase Relay Pickup Setting
High-Set Instantaneous Overcurrent Ground Relay Pickup Setting
Time Overcurrent Phase Relay Pickup Setting—Sensitivity Check
Time Overcurrent Phase Relay Pickup Setting—Time Delay
Time Overcurrent Phase Relay Pickup Setting—Upstream Coordination
Time Overcurrent Ground Relay Pickup Setting—Sensitivity Check
Time Overcurrent Ground Relay Pickup Setting—Time Delay
Time Overcurrent Relay Ground Pickup Setting—Upstream Coordination
Distribution-Line Protection: Network Lines
Networked Distribution-Line Protection Philosophy
Setpoint Margin Considerations
Distribution-Line Protection
Time Overcurrent Phase Relay Pickup Setting—Load Capability
Time Overcurrent Ground Relay Pickup Setting—Load Capability
Instantaneous Overcurrent Phase Relay Pickup Setting
Instantaneous Overcurrent Ground Relay Pickup Setting
Definite Time Overcurrent Phase Relay Pickup Setting
Definite Time Overcurrent Ground Relay Pickup Setting
Time Overcurrent Phase Relay Pickup Setting—Sensitivity Check
Time Overcurrent Phase Relay Pickup Setting—TimeDelay
Time Overcurrent Phase Relay Pickup Setting—Upstream Coordination
Time Overcurrent Ground Relay Pickup Setting—Sensitivity Check
Time Overcurrent Ground Relay Pickup Setting—Time Delay
Time Overcurrent Relay Ground Pickup Setting—Upstream Coordination
Transmission-Line Protection
Phase Distance Relays
Ground Distance Relays
Overcurrent Ground Relays
Instantaneous Overcurrent Ground Relays
Time Overcurrent Ground Relays
Directional Unit Sensitivity for Ground Faults
Current-Polarized Ground Relays
Voltage-Polarized Ground Relays
High-Speed Relaying Schemes
Line Differential Scheme
CT Saturation
Transformer Protection
Transformer External Fault Protection
Bus Protection
Overcurrent Bus Differential
Bus Differential—Quick Trip Settings
Bus Differential—Time Overcurrent Settings
High-Impedance Bus Differential
Sensitivity for Bus Faults
Breaker Failure Relaying
Remote Breaker Failure Protection—Phase Distance Relays
Remote Breaker Failure Protection—Overcurrent Ground Relays
Remote Breaker Failure Protection—Watt-Type Ground
Relays
Local Breaker Failure Protection—Traditional
Control Elementary Diagram
Control Elementary Diagram
Local Breaker Failure Protection for Transformer Protection
Capacitor Protection
Neutral Current Monitoring
Midpoint Voltage Monitoring
Shunt and Series Reactor Protection
Grid Protection
Voltage Issues
Undervoltage Protection—Grid Protection
Undervoltage Protection—Load Protection
Overvoltage Protection—Grid Protection
Overvoltage Protection—Load Protection
Frequency Control
Underfrequency Relaying
Overfrequency Relaying
Index
Biography
Anthony Sleva is president of Sleva Associates, an electrical consulting and training company. He is a registered Professional Engineer with a BSEE degree from Pennsylvania State University. During his career, he has designed electrical systems for nuclear generating stations; designed 500-230 KV, 230-69 KV, 138-12 KV and 69-12 KV substations; provided technical support to power dispatchers, system operators and plant operators; and developed technical training programs for technicians, drafters, designers and technical clerks. Mr. Sleva specializes in the analysis of power system events that cause the loss of customer load and/or the initiation of emergency load control procedures as well as events that may have been caused by incorrect protective relay actuations.
