Single Line Diagram (SLD) is a simplified representation of a three-phase electrical power system using a single line and standard symbols. It shows the main components of a power system—such as generators, transformers, circuit breakers, busbars, and transmission lines—in a simplified manner.
A Lightning Arrester (LA) is a protective device that protects substation equipment from high-voltage surges caused by lightning or switching operations. It provides a low-resistance path to ground so that surge voltages are safely discharged without damaging equipment.
A Current Transformer (CT) is an instrument transformer that reduces very high current in the power line to a small, proportional current value that can be safely measured by meters and protective relays.
A Potential Transformer (PT), also called a voltage transformer, steps down high system voltage to a lower standard value suitable for measurement and protection.
A Capacitive Voltage Transformer (CVT) is used in high-voltage transmission systems to measure voltage. It works using a capacitive voltage divider to reduce very high voltage to a lower measurable value and is also commonly used for communication coupling in transmission lines.
Power Line Carrier Communication (PLCC) is a system used in substations where the power transmission line itself is used to transmit communication signals. It is used for telecommunication, protection signaling, and control between substations over long distances.
A Wave Trap (Line Trap) is used in PLCC systems to block high-frequency carrier signals from leaving the desired transmission path. It works as a low pass filter by eliminating high frequency signal and pass the power frequency.
An Isolator (Disconnect Switch) is a mechanical switching device used to isolate a part of the electrical system for maintenance or safety. It is operated only when the circuit carries no current and ensures complete disconnection of equipment from the power supply.
A Circuit Breaker (C.B.) is an automatic switching device used to protect electrical systems from faults such as short circuits or overloads. It can interrupt current flow under normal and fault conditions.
Sequence: L.A--->C.V.T--->ISO--->C.T--->C.B--->ISO










