Surge arresters are protective devices that limit voltage by bypassing or discharging surge current. They stop the flow of current from continuing to follow to the ground. An arrester does not absorb lightning or stop lightning; it protects equipment by limiting voltage, directing the lightning, and diverting it.
Surge arresters are used in many places, from protecting homes to utility substations. They are used on residential circuit breakers, transformers mounted on pads, pole-mounted transformers, riser poles with pole-mounted risers, and utility substations.
The IEEE C62.11 standard and IEC 60099-4 standard define the standards for surge arresters.
Why Should You Use a Surge Arrester?
Voltage surges can occur on distribution power lines, primarily caused by lightning. On average, 100 lightning strikes occur on Earth’s surface each second. Lightning is an unpredictable and random event.
Temporary overvoltages and switching surges are also sources of voltage surges. Switching surges, caused by changes in system operating conditions, are the primary voltage surge for station-class arresters. Switching surges involve trapping and subsequently releasing energy. Ground faults in one phase can cause temporary overvoltages, resulting in voltage rising on the unfaulted phases until faults are cleared.
Why Do Arresters Operate?
The surge arrester should be able to handle the power frequency voltage at which it will operate. It must discharge transient energy in the system as current while preventing excessive voltage across the protected equipment. It must operate in the same environment as the equipment it protects. The Temporary Overvoltage (TOV) or TOV capability shows the maximum overvoltage that an arrester can sustain without damage.
There are several reasons why arresters may be activated:
– The TOV condition has lasted too long.
– The arrester is undersized.
– The duty rating was exceeded by lightning surges.
– Gap degradation in silicon carbide arresters.
– Leakage of silicone oil additive from the oil-based polymer housing can cause housing degradation.
– Wildlife interference.
– Disk aging.
– Porcelain arresters can break after a life-ending event, while polymer arresters may experience a side blowout or disconnection from the ground.
Types of Surge Arresters
Secondary Arresters:
Secondary arresters protect against secondary surges. Transformer failure rates can range between 0.4% and 1%. 50%-70% of transformer failures can be attributed to surges on the low side. The failure rate of transformers can be significantly reduced by using secondary arresters, whether at home or at the entrance of the service.
Distribution Arresters:
Distribution arresters have ratings of 1 to 36 kV and come in three categories: light duty, normal, and heavy duty. The riser pole is an example of a heavy-duty arrester. Transformers can also use distribution arresters, including under-oil-mounted, elbow-mounted, or cubicle-mounted types. The Evolution arrester is suitable for all overhead applications. Riser poles are used to reduce voltage surges seen by underground cables and equipment, and open point arresters prevent voltage doubling or surge reflection.
Intermediate Arresters:
Intermediate arresters have higher discharge voltages and a high fault current resistance capability. They are available in ratings of 3 to 120 kV.
Station Class Arresters:
Station class arresters have the highest fault current resistance and the best discharge voltages among all arresters. They are available in ratings of 3 to 684 kV. Station class arresters come in various cantilever strengths to meet the needs of even the most demanding applications.
For nearly half a century, Swartz Engineering has been at the forefront of industry safety. They are a family-owned company specializing in power distribution for the electrical industry. They are the leading manufacturer of surge arrestor. Our design ensures maximum flexibility for excellent reliability and a high return on investment.