The protective equipment used to protect equipment against lightning stroke is:
Lightning arrester
Understanding Lightning Protection for Electrical Equipment
Electrical equipment installed outdoors or connected to overhead lines is highly susceptible to damage from lightning strokes. A direct lightning strike or even nearby strikes can induce very high voltage surges on the power system, which can severely damage insulation and components.
To protect valuable electrical equipment such as transformers, generators, substations, and transmission lines from these dangerous voltage surges, special protective devices are employed. The question asks about the specific equipment used for this purpose.
Analyzing the Protective Equipment Options
Let's examine the functions of the given options:
- Shunt reactors: Shunt reactors are used in power systems primarily to consume reactive power. They help control voltage levels on long transmission lines by compensating for the capacitive reactive power generated by the lines. They are not designed to protect against lightning surges.
- Circuit breaker: A circuit breaker is a switching device that can interrupt a circuit under normal or fault conditions. Its main purpose is to protect equipment from overcurrents (like those caused by short circuits or overloads) by quickly interrupting the flow of current. While they protect against faults, they are not the primary device for diverting voltage surges caused by lightning.
- Isolator: An isolator (or disconnector) is a mechanical switch used to isolate a section of a circuit from the power supply. It is operated only when the circuit is de-energized and is used for maintenance purposes to provide a visible break. Isolators offer no protection against lightning surges while the equipment is in operation.
- Lightning arrester: A lightning arrester (also known as a surge arrester) is a protective device installed on power systems to protect equipment from overvoltage transients caused by lightning strikes or switching surges. It works by diverting the surge current safely to the ground, thus limiting the voltage rise across the protected equipment.
How a Lightning Arrester Protects Equipment
The lightning arrester is connected in parallel with the equipment to be protected and between the live wire and the ground. Under normal operating conditions, it acts like an open circuit and allows no current to flow through it (or only a very small leakage current). However, when a high-voltage surge, such as that caused by a lightning stroke, reaches a certain threshold voltage, the lightning arrester becomes conductive. It provides a low-resistance path for the surge current to flow to the ground, bypassing the protected equipment. Once the surge has passed and the voltage returns to normal levels, the lightning arrester quickly returns to its non-conductive state, preventing the normal power system current from flowing to the ground.
Therefore, the equipment specifically designed and used to protect electrical installations against the damaging effects of lightning strokes is the lightning arrester.
| Equipment | Primary Function | Protection Against Lightning Surges? |
|---|---|---|
| Shunt Reactor | Reactive power compensation (Voltage control) | No |
| Circuit Breaker | Fault current interruption (Overcurrent protection) | No |
| Isolator | Electrical isolation (for maintenance) | No |
| Lightning Arrester | Diverting overvoltage surges (Lightning/Switching) | Yes |
Conclusion on Lightning Protection Equipment
Based on the functions of the various devices, the lightning arrester is the specific equipment used to protect electrical equipment against voltage surges caused by lightning strokes. It is an essential component in substations, transmission lines, and other parts of the power system exposed to lightning risk.
Revision Table: Key Protective Devices
| Device | Role in Power System | Protected Against |
|---|---|---|
| Lightning Arrester | Overvoltage protection | Lightning strokes, Switching surges |
| Circuit Breaker | Overcurrent protection & Switching | Short circuits, Overloads |
| Isolator | Provides visible isolation | Accidental re-energization during maintenance |
| Shunt Reactor | Voltage Control | Reactive power issues |
Additional Information: Types and Placement of Lightning Arresters
Lightning arresters are crucial for ensuring the reliability and safety of power systems. Different types of lightning arresters exist, such as Silicon Carbide (SiC) gap-type arresters and Metal Oxide Varistor (MOV) gapless arresters. MOV arresters are more commonly used now due to their superior performance characteristics, like faster response and better energy handling capability.
Proper placement of lightning arresters is vital. They are typically installed at:
- Substation entrances
- Terminals of transformers, generators, and other critical equipment
- Along transmission and distribution lines
Effective grounding is also essential for the lightning arrester to function correctly, as it relies on diverting the surge current to the earth.
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