Generator Protection course

Trainer: Dr. Saeed Roostaee (Profile)

Power plant introduction

• Power System Components
• Single Line Diagram (SLD)
• Hydro-Electric Power
• Fossil fuel power
• Nuclear power generation
• Wind energy
• Diesel Engine
• Solar power

Generator Introduction

• Synchronous Generator
• Generator construction
• Stator
• Rotor
• Salient pole rotor
• Cylindrical rotor
• Synchronous Generator operation
• Equivalent circuit of synchronous generator
• Power triangle – reactive power
• Generator connection
• Direct Connected Generators
• Unit Connected Generator

Faults in Generators

• Stator Earth Faults
• Rotor Earth Faults
• Stator Short Circuits
• Stator Interturn faults
• External faults
• Stator Winding Faults
• Control System and Field Winding/Rotor Circuit Faults
• Abnormal Operating Conditions

Abnormal Operating Condition

• overcurrent/overload
• unbalanced load
• overtemperature
• over- and undervoltage
• over- and under-excitation
• over- and under-frequency
• over-fluxing
• asynchronous running
• out of step
• generator motoring
• failures in the machine control system
• failures in the machine cooling system
• failures in the primary equipment
• open phase

Short-circuit study in Generators

• Generator behavior during short circuits
• Generator short-circuit current Decay
• Effect of DC offsets
• IEC 60909 standard

Generator Protection introduction

• Why Generator Protection
• The objective of the protection system
• Sensitivity
• Reliability
• Selectivity
• Speed
• Zones of protection
• Ground fault protection
• Phase fault protection
• Field protection

Generator Protection Standard

• IEEE Recommendations of protection elements for different Generator capacities.
• 32 Reverse Power
• 40 Loss of Excitation
• 46 Negative Sequence
• 49 Thermal Overload
• 51V voltage restraint
• 51G Ground over current
• 60 Voltage Balance
• 64 Ground Relay
• 87 Differential
• IEEE C37.102 standard (Large machine protection scheme)
• Typical Unit connected Generator
• Typical Protection Function for a large generator

Multifunction Generator Protection System (MGPS)

• Protection relay evaluation
• Multifunction Generator Protection System (MGPS)
• Typical MGPS block diagram
• MGPS features:
• Metering of voltages, currents, power, and other measurements
• Oscillography; sequence of events capture with time tagging
• Remote setting and monitoring through communications
• User reconfigurability of tripping schemes and other control logic
• Reduced panel space and wiring
• The low burden on the VTs and CTs
• Continuous self-checking and ease of calibration
• Communications
• Numerical relay advantages
• Digital phase measurement
• Phasor values
• Symmetrical component
• Overcurrent element
• Negative sequence element
• Voltage protection element
• Differential protection
• Impedance plane
• Distance element

Generator Differential Protection

• CT error effect
• CT saturation effect
• Generator Differential settings
• Internal faults
• External faults
• External faults with CT saturation
• Generator diff Electro-mechanical
• Electro-mechanical diff protection based on induction relay
• Electro-mechanical Diff Protection with moving coil relay
• Electro-mechanical Diff Protection Based on Analogue Static Measuring
• Digital Differential Protection
• Numerical differential relay technology

Turns to Turns Faults Protection

• Split phase relay scheme
• Using Separate CTs
• Split phase current tripping
• Split phase current variation and measurement
• Split phase current Settings
• Using unbalanced overvoltage

Stator Ground Fault Protection

• Stator ground fault damage
• Generator Neutral Grounding
• Solidly Grounded
• Low Impedance
• High Impedance
• Hybrid Grounding
• Ungrounded
• 87GD Generator Ground Differential
• 59N overvoltage protection
• 95 % of the stator winding protection
• Third Harmonic Neutral Under Voltage 27N3
• 27N3 and 59G combination Stator Ground Fault Cover
• Sub Harmonic (Low Frequency) Injection

Rotor Ground Fault

• Field Fault Protection
• Second Rotor Ground Fault
• Using a DC Source
• Using a Voltage Dividers
• Field Ground Detection Using Injected Voltage
• Field Ground Tripping

Loss of excitation

• Underexcitation And Loss of Excitation Protection
• Generator Capability Curve
• Generator impedance variation
• Negative Offset Mho Element Schemes
• Loss Of field Protection (ANSI 40)

Overexcitation and Overvoltage Protection

• Over Flux Protection 24
• V/Hz Versus Overvoltage Damage
• Causes of V/Hz Problems
• Offline generator voltage regulator problems
• System problems
• IEEE V/Hz Capability Standard
• IEC Standard for Generator V/Hz Capability
• V/Hz Damage
• Typical V/Hz Curve for generators
• Typical V/Hz Curve for Transformer
• Definite time V/Hz Protection
• Inverse time V/Hz Protection

System Backup Protection

• Overcurrent 51V
• Generator Transformer Basic Backup Protection
• Voltage Controlled Overcurrent
• Voltage Restrained Overcurrent
• V R Overcurrent
• Impedance protection 21
• Back-up protection against phase short circuit
• Distance phase backup protection
• Protected zones
• Distance Phase Backup

Out Of Step Protection

• Out Of Step (Pole Slip) Protection
• Network short-circuit
• High load variation
• Mho characteristics and blinders

CBF

• Circuit Breaker failure 50BF
• Generator Breaker Failure
• CBF Logic

Frequency Protection

• Abnormal Frequency Protection
• Under frequency
• Over frequency
• Conformance to IEC 60034:2007
• Turbine Operational Limit

Negative Sequence Protection

• Current Unbalance (Negative Sequence)
• Typical Source of I2
• I2 in the Generator
• Continuous unbalanced current capability
• Short-time unbalanced current capability
• Negative Sequence ( 46 ) Relay
• Modern I2 Relay Characteristics

Reverse power protection

• Reverse power protection (Ansi 32)
• Loss of Prime Mover Anti-motoring ) Protection
• Damage Potential
• Motoring Power

Inadvertent Energization Protection

• Causes
• Operating errors
• Breaker head flashovers
• Control circuit malfunctions
• Combination of above
• Generator Response and Damage from Inadvertent Energization
• Inadvertent Energization Scheme
• Inadvertent Energization Event Recorded

Transformer Protection in the Power Plant

Transformer Fault

• Earth fault on H.V. external connections
• Phase-to-phase fault on H. V. external connections
• Internal earth fault on H.V. windings
• Internal phase-to-phase fault on H.V. windings
• Short circuit between turns H.V. windings
• Earth fault on L.V. external connections
• Phase-to-phase fault on L.V. external connections
• Internal earth fault on L. V. windings
• Internal phase-to-phase fault on L.V. windings
• Short circuit between turns L.V. windings

Transformer Protection

• Unit Differential Protection (87 T)
• Overall Differential Protection (87 U)
• Buchholz (83)
• Oil Pressure (71)
• Backup OC (51)
• Backup Earth fault (51 N)
• Restricted Earth Fault (REF) (87 N)
• Differential Protection
• Restricted Earth Fault Protection
• Thermal overload Protection
• Over-excitation Protection
• Overcurrent protection
• Earth fault protection
• Under and over voltage protection
• Mechanical protection such as Buchholz-relay, winding temperature, …

Generator Protection Relay IEDs and software

• ABB Generator Protection Relays
• PCM600
• REG 216
• REG 316
• REG 630
• REG 650
• REG 670
• REG 670 Protection System
• REG 670 Available functions
• REG 670 Control and monitoring functions
• Local HMI
• Applications
• SIPROTEC 4
• Digsi 4
• Digsi 5
• 7UM61
• 7UM62
• 7UT61/2
• SIPROTEC 5
• 7UM85
• 7UT82/85/86/87