switchgear and protection 1
TRANSCRIPT
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Introduction to Power System protection
Md Irshad [email protected]
Electrical Engineering DepartmentSubject: NEE –602: SWITCHGEAR AND
PROTECTION
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Unit I: Introduction to Protection System: Introduction to protection system and its elements, functions of protective relaying, protective
zones, primary and backup protection, desirable qualities of protective relaying, basic terminology.
Relays: Electromagnetic, attracted and induction type relays, thermal relay, gas actuated relay, design
considerations of electromagnetic relay. Unit-II: Relay Application and Characteristics: Amplitude and phase comparators, over current relays, directional relays, distance relays,
differential relay. Static Relays: Comparison with electromagnetic relay, classification and their description, over
current relays, directional relay, distance relays, differential relay. Unit-III Protection of Transmission Line: Over current protection, distance protection, pilot wire protection, carrier current protection,
protection of bus, auto re-closing, Unit-IV: Circuit Breaking: Properties of arc, arc extinction theories, re-striking voltage transient, current chopping,
resistance switching, capacitive current interruption, short line interruption, circuit breaker ratings.
Testing Of Circuit Breaker: Classification, testing station and equipments, testing procedure, direct and indirect testing.
Unit-V Apparatus Protection: Protection of Transformer, generator and motor. Circuit Breaker: Operating modes, selection of circuit breakers, constructional features and
operation of Bulk Oil, Minimum Oil, Air Blast, SF6, Vacuum and d. c. circuit breakers.
Syllabus SWITCHGEAR AND PROTECTION
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Introduction to protection system and its elements Functions of protective relaying Protective zones Primary and backup protection Desirable qualities of protective relaying Basic terminology. Relays: Electromagnetic Attracted and induction type relays Thermal relay & gas actuated relay Design considerations of electromagnetic relay
UNIT-1
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Switch gear - It's function
SWITCHGEAR : Gear for Switching
Switching DevicesControl & Sensing
DevicesDecision Making
Devices
Circuit breakersIsolatorsSwitches
Current Transformers;
Voltage Transformers;
Reactors;Tripping Units.
Protective RelaysLightning Arresters
Fuses
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System protection is the art and science of detecting problems with power system components and isolating these components.
What is System protection?
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The power system must maintain acceptable operation 24 hours a day
Voltage and frequency must stay within certain limits Protect the public Improve system stability Minimize damage to equipment Protect against overloads
Need for the protection
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Damage to Main Equipment
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Reliability: System operate properly Security: Don’t trip when you shouldn’t Dependability: Trip when you should
Selectivity: Trip the minimal amount to clear the fault or abnormal operating condition
Speed: Usually the faster the better in terms of minimizing equipment damage and maintaining system integrity
Economics: Don’t break the bank
Desirable Protection Attributes
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• Transformers - to step up or step down voltage level • Breakers - to energize equipment and interrupt fault current to isolate
faulted equipment• Insulators - to insulate equipment from ground and other phases• Isolators (switches) - to create a visible and permanent isolation of
primary equipment for maintenance purposes and route power flow over certain buses.
• Bus - to allow multiple connections (feeders) to the same source of power (transformer).
Primary Equipment & Components
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• Grounding - to operate and maintain equipment safely• Arrester - to protect primary equipment of sudden overvoltage (lightning
strike).• Switchgear – integrated components to switch, protect, meter and
control power flow• Reactors - to limit fault current (series) or compensate for charge
current (shunt)• VT and CT - to measure primary current and voltage and supply scaled
down values to P&C, metering, SCADA, etc.• Regulators - voltage, current, VAR, phase angle, etc.
Primary Equipment & Components
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Typical Bulk Power SystemGeneration-typically at 4-20kV
Transmission-typically at 230-765kV
Subtransmission-typically at 69-161kV
Receives power from transmission system and transforms into subtransmission level
Receives power from sub transmission system and transforms into primary feeder voltage
Distribution network-typically 2.4-69kV
Low voltage (service)-typically 120-600V
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1. Generator or Generator-Transformer Units2. Transformers3. Buses4. Lines (transmission and distribution)5. Utilization equipment (motors, static loads, etc.)6. Capacitor or reactor (when separately protected)
Protection Zones
Unit Generator-Tx zoneBus zone
Line zoneBus zone
Transformer zone Transformer zone
Bus zone
Generator
~XFMR Bus Line Bus XFMR Bus Moto
r
Motor zone
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1. Overlap is accomplished by the locations of CTs, the key source for protective relays.
2. In some cases a fault might involve a CT or a circuit breaker itself, which means it can not be cleared until adjacent breakers (local or remote) are opened.
Zone Overlap
Zone A Zone B
Relay Zone A
Relay Zone B
CTs are located at both sides of CB-fault between CTs is cleared from both remote sides
Zone A Zone B
Relay Zone A
Relay Zone B
CTs are located at one side of CB-fault between CTs is sensed by both relays, remote right side operate only.
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Thank You