About Lesson
Key Components of a Switchyard
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Power Transformers
- Function: Step up or step down voltage levels for transmission and distribution.
- Specifications:
- Voltage Rating: Primary and secondary voltage levels.
- Power Rating: MVA (Mega Volt Amps).
- Cooling Method: ONAN, ONAF, OFAF (Oil Forced Air Forced).
- Impedance: Percentage impedance.
- Tapping Range: On-load or off-load tap changer ranges.
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Circuit Breakers
- Function: Interrupt fault currents and protect the electrical system.
- Types: SF6, vacuum, oil, and air circuit breakers.
- Specifications:
- Voltage Rating: Rated operational voltage.
- Current Rating: Continuous current rating.
- Breaking Capacity: Rated short-circuit breaking current.
- Insulation Medium: SF6 gas, vacuum, oil, or air.
- Operating Mechanism: Spring-operated, hydraulic, or pneumatic.
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Disconnectors (Isolators)
- Function: Provide a visible disconnection point for safe maintenance.
- Specifications:
- Voltage Rating: Operational voltage.
- Current Rating: Continuous current carrying capacity.
- Type: Single-break, double-break, pantograph.
- Motor Operation: Motorized or manual operation.
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Current Transformers (CTs)
- Function: Measure current and provide isolation for measurement instruments and protection relays.
- Specifications:
- Voltage Rating: Rated primary voltage.
- Current Rating: Primary and secondary current ratings.
- Accuracy Class: For metering (e.g., 0.2, 0.5) and protection (e.g., 5P, 10P).
- Burden: VA rating of the secondary load.
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Voltage Transformers (VTs)
- Function: Step down high voltages for metering and protection.
- Specifications:
- Voltage Rating: Rated primary and secondary voltage.
- Accuracy Class: For metering and protection.
- Burden: VA rating of the secondary load.
- Type: Electromagnetic or capacitive.
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Busbars
- Function: Conduct and distribute electrical power within the switchyard.
- Specifications:
- Material: Copper or aluminum.
- Configuration: Single bus, double bus, ring bus, breaker-and-a-half.
- Current Rating: Continuous current capacity.
- Short Circuit Rating: Maximum fault current capacity.
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Protection Relays
- Function: Detect faults and initiate circuit breaker operations.
- Types: Overcurrent, differential, distance, and earth fault relays.
- Specifications:
- Voltage Rating: Rated operational voltage.
- Current Rating: Input current rating from CTs.
- Features: Communication protocols (e.g., IEC 61850), trip settings, and response time.
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Surge Arresters
- Function: Protect equipment from transient overvoltages.
- Specifications:
- Voltage Rating: Maximum continuous operating voltage (MCOV).
- Discharge Current: Rated discharge current capacity.
- Energy Rating: Absorption capacity for surge energy.
- Material: Metal oxide, silicon carbide.
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Control and Communication Systems
- Function: Monitor, control, and automate switchyard operations.
- Specifications:
- SCADA Systems: Supervisory control and data acquisition capabilities.
- Communication Protocols: IEC 61850, DNP3, Modbus.
- Automation: PLCs (Programmable Logic Controllers) and RTUs (Remote Terminal Units).
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Grounding and Bonding Equipment
- Function: Ensure safety by preventing potential differences and dissipating fault currents.
- Specifications:
- Grounding Conductors: Material (copper or aluminum) and cross-sectional area.
- Grounding Grid: Layout and depth.
- Earthing Resistance: Maximum permissible resistance value.