A substation Single-Line Diagram (SLD) is a simplified representation of the electrical distribution system that shows the major components and their connections. It uses standardized symbols & single lines to show how power flows from input sources to multiple outputs.
Key Components of a Substation SLD
- Lightning Arresters
- Instrument Transformers
- Circuit Breakers
- Isolators (Disconnect Switches)
- Bus Bars
Lightning Arresters
These devices protect equipment & structures from high-voltage lightning strikes (or) switching surges by diverting the surge to the ground, so preventing electrical system damage.
Instrument Transformers
Current Transformer (CT)
Measures alternating current by creating a decreased current proportional to the primary circuit current.
- Primary winding is connected in series with the main circuit and carries a high current.
- Secondary winding generates a scaled-down current for measurement or protection devices.
- The IEC 61869-2 standard specifies current transformers (CTs) utilized in AC power systems to provide precision, safety, and dependability in metering and protection applications.
Potential Transformer (PT)
- Potential Transformer (PT) Reduces high voltage to a safe level for measurement, metering, & protection.
- The primary winding is connected in parallel to the high-voltage side of the system.
- Secondary winding generates a low-voltage output proportional to the primary voltage.
- Standard secondary voltages: 110 or 100 volts.
- IEC 61869-3 defines the specifications for PTs in AC power systems.
Circuit Breakers
Circuit breakers safeguard electrical circuits from overloads, short circuits, and failures. It works by stopping the flow of current when abnormal conditions occur.
There are several types of circuit breakers, including air, vacuum, oil, and SF6.
Isolators (Disconnect Switches)
These devices isolate a section of the substation for safety during repair.
No-load switches act after the circuit breaker interrupts current flow.
Bus Bars
Power connectors for the substation! Bus bars transmit electricity across many circuits, ensuring a smooth and efficient power flow across the network.
These components are essential to the substation functioning, both efficiently and safely.