Surge Arresters are used to limit voltage surges on an
electrical system to level that it can be controlled. It is designed and
connected between a conductor of an electrical system and ground to limit the
magnitude of transient over voltages on equipment.
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Surge Arresters |
WHAT EXACTLY DOES A SURGE ARRESTER DO?
1.
Surge Arresters does not absorb
the lightning.
2.
Surge Arresters does not stop the
lightning.
3.
Surge Arresters divert the
lightning to ground.
4.
Surge Arresters clamp (limit) the
voltage produced by lightning.
5.
Surge Arresters equipment
electrically in parallel with it.
HOW DOES SURGE ARRESTERS WORK?
At the heart of all arresters is Metal Oxide Varistors
(MOV). The MOV disk is a semiconductor that is sensitive to voltage. At normal
voltage, the MOV disk is an insulator and will not conduct current. But at
higher (extreme) voltage caused by lightning or any surges, it becomes a conductor.
The usual construction of a typical surge arrester consists
of disks of zinc oxide material sized in cross-sectional area to provide
desired energy discharge capability, and in axial length proportional to the
voltage capability. The disks are then placed in porcelain enclosures to
provide physical support and heat removal, and sealed for isolation from
contamination in the electrical environment.
There are four basic types of surge arresters defined by
industry standards. The surge arrester type selected for the application
depends on the equipment being protected and what level of protection is
required.
Secondary Type – Available in ratings up to 650 Volts, and
are used to protect equipment at the utilization voltage level.
Distribution Type – Typically used for the protection of
equipment on power distribution circuits. They are available in ratings up to
42 kV. This type of surge arrester is further defined by normal and heavy duty.
Intermediate Type – Available in ratings up to 144 kV. This
type of surge arrester offers improved protective characteristics and
durability. They are generally used for protection of smaller substations, or
medium class power equipment.
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Station Type Surge Arresters |
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