Functions and Kinds of Surge Arrester

Functions and Kinds of Surge Arrester

What is Surge Arrester?

Surge Arrester is sometimes called an overvoltage protector, or overvoltage limiter. Install the arrester near the protected device and connect it in parallel with the protected device.

01 The Function of Surge Arrester

Surge Arrester is a very important power system to protect the electrical equipment or line from overvoltage damage equipment. It is actually discharge equipment, which is usually connected between the wire and the ground, and the equipment is protected in parallel.

When the protected equipment runs under the normal operating voltage, the arrester does not act, then it is regarded as the circuit breaker.

Once the overvoltage occurs and endangers the insulation of the protected equipment, the arrester immediately acts to direct, which makes the high voltage impulse current to the ground, thus limiting the voltage amplitude and protecting the insulation of the electrical equipment. When the overvoltage disappears, the arrester quickly restores to its original state, so that the system can supply power normally.

02 Classification of Surge Arresters

Tubular Arrester

Tube type is protection gap type, mostly used in the power supply line for lightning protection. A tubular arrester is actually a kind of protection gap with a higher arc-extinguishing ability. It is composed of two series gap.A gap in the atmosphere, known as the outer gap, works to isolate the working voltage to avoid the production pipe by the power frequency leakage current through the pipe burned. The other is installed in the trachea, known as the internal clearance or arc extinguishing clearance. The arc extinguishing ability of the tubular arrester is related to the size of the power frequency continuous current. But the tubular arrester also has the following disadvantages:

(1) The volt-second characteristic is steeper and the discharge dispersion is larger, while the volt-second characteristic of the shock discharge of general transformers and other equipment insulation is relatively flat, and the two can not be well matched.

(2) After the operation of the tubular arrester, the working busbar is directly grounded to form a truncated wave, which is unfavorable to the longitudinal insulation of the transformer. In addition, its discharge characteristics are greatly affected by atmospheric conditions, so the tubular arrester is only used for line protection at present (such as large span and cross gear distance and incoming line protection of power station and substation).

Valve Type Arrester

It is a gap-type lightning protection device composed of many gaps in series. Composed of spark gap and valve plate resistance, valve plate resistance material is special silicon carbide. When there is lightning overvoltage, the spark gap is broken down, and valve plate resistance drops, which leads to the lightning flow into the earth. This protects electrical equipment from lightning currents. Normally, the spark gap does not break down and the valve disc resistance rises, preventing normal AC current from passing through.

A valve arrester is used to protect the main components of power generation and transformer equipment. The gap in the arrester is discharged first, limiting the overvoltage amplitude on the electrical equipment, when a higher amplitude of the lightning wave invades the protected device. In the process of discharging lightning current, the residual pressure on the arrester is limited to the insulation level of the equipment because the nonlinear resistance value of the silicon carbide valve disc is greatly reduced. After the thunder wave, the discharge gap recovery silicon carbide valve disc nonlinear resistance value and greatly increased, automatically cutting off the power frequency current, and protecting the electrical equipment.

Zinc Oxide Arrester

Zinc Oxide Arrester is a kind of lightning protection equipment with superior protection performance, pollution resistance, and lightweight and stable valve disc performance. Metal Oxide Arrester (MOA) is an important protective appliance used to protect the insulation of power transmission and transformation equipment from the harm of overvoltage. It has the advantages of fast response, flat volt-ampere characteristics, stable performance, large current capacity, low residual pressure, long life, simple structure and so on. It is widely used in power generation, transmission, power transformation, distribution and other systems.

Zinc Oxide has good non-linear characteristics, a large flow rate, low residual pressure level, fast response time and no continuous flow and other characteristics, lightning arrester is easy to absorb energy, no series clearance restriction, only related to the strength of the valve disc itself. Compared with silicon carbide valve disc, the flow capacity per unit area of oxide valve disc is 4 ~ 4.5 times larger.

Therefore, with such a valve plate made of an arrester, not only can limit atmospheric overvoltage, but also can be used to limit operating overvoltage, and even can withstand a certain duration of short-time (power frequency) overvoltage. The defect has a leakage current, which will make the device aging in advance. In addition, metal oxide arresters basically have no continuous current, light load, and strong resistance to repeated action, Voltammetric characteristics are symmetrical, no polarity problems, therefore, can be made into DC arresters.