The most c ommon surge arrester is a non-linear metal oxide resistors type in a porcelain or silicone rubber housing, and are fitted in parallel with the intended circuit to protect from surges and connected to the earth grid.
This is because the main reason for most of over voltages was lightning when the power system design was not that much complicated. In most advanced designs, load shading, sudden change in high power in load, and disconnector switching in EHV substation causes over voltage where surge arrester are used in a substation instead of lightning arrester which provides protection against all of the above mentioned surges.
Lightning Arrester is a protective device used to protect the circuit from lightning strokes having high transient voltage surges, surge currents due to lightning, spark and isolation arcs etc. It is used to protect the power system by redirecting the high voltage surges to the ground.
Although, the earthing or ground wire also protects the overhead lines and power system from direct lightning strikes but it may fail to protect against traveling waves which may reach to the terminal connected devices and equipment. For this reason, surge diverters or lightning arresters are used to protect the power system against such produced surges by faults or lightning stokes.
Lightning arresters are installed on the peak height of a structure i. A lightning rod also known as lightning conductor is a metal rod copper or aluminium or other conducting materials installed on the top of the structure transmission and distribution towers , buildings etc to protect it from the direct lighting strikes. Lightning is the electrostatic discharge between clouds and earth.
If they hit the power lines directly, the system voltage may rise to a dangerous level which may harm the electrical installation and equipment. For this reason, a lightning rod is used to protect the electrical installation, equipment and devices from direct hit of lightning strokes. Lightning rod is cheaper than surge arrester which is mounted on the top surface of a building or power lines tower which provides a safe path to the high value electrostatic charges and lightning currents to the ground it must be properly earthed to the grounding system as well.
Surge Suppressor is also known as surge protector or transient suppressor. It is a device installed in the home distribution board to protect the home wiring installations from voltage surges or switching surges. For example, when an inductive load is switched off, it generates voltage surges also known as switching surges in the system following the self inductance laws of back EMF.
Surge arresters or lightning arresters are used by utility companies in power transmission and distribution systems to protect their electronic equipment and infrastructure.
They can also be found in large-scale industrial operations, such as mining or oil and gas. They look like this:. Surge protectors are used to protect domestic and consumer electrical equipment. They protect electronic appliances in your home like your computer, television, and refrigerator. The clamping voltage refers to the maximum amount of voltage that can pass through a surge protector or electrical breaker before it restricts further current from passing through it.
You can use a good multimeter to measure the voltage across an electrical breaker. There are many national and international standard related to surge protectors. Some of the most prominent include:. After the transient is diverted, the SPD automatically resets back to its high impedance state.
On a basic level, the lightning protection system protects the facility and structure from direct strikes , while SPDs protect electrical equipment and systems against surges or transients. How the two operate, and the components involved, also vary. Lightning protection system components are always in place and ready to function, while SPDs monitor internal system voltages and spring into action if a transient voltage occurs on the circuit.
Though lightning is not the most common transient event, it is the most significant. While a lightning protection system protects the exterior against the affects of lightning, SPDs must be in place to support the other system and the related transients a strike creates. SPDs will activate and begin to conduct energy into the grounding system if surges to bonded equipment exceed the designated rating. Lightning is the most likely external cause of a significant surge, and SPDs must be installed to limit currents entering into the internal environment, showing the importance of an interconnected facility electrical protection system.
What this rating means is that it can handle greater surges than devices with a lower I n rating. Lightning and surge protection are two elements of an effective electrical protection system.
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