Types of Lightning Arresters-Horn Gap, Rod Gap, Valve Type

There are different types of lightning arresters like Rod Gap Arrester, Horn Gap Arrester, Valve type, expulsion type and they differ from each other only in construction details. but they operate on the same principle which is to provide a low resistance path for surges to the ground.

Types of lightning Arresters

  • Rod Gap Arrester
  • Horn Gap Arrester
  • Valve Type
  • Expulsion Type
  • Multi Gap arrester

Rod gap Lightning Arrester

Rod Gap Arrester is a very simple type of lightning arrester, which consists of two 15mm rods that are bent at an angle 90° with a gap in between them as depicted in the diagram. One end of lightning arrester connected to the line and another end of rod connected to the earth.

Rod-Gap-type-lightning-Arrester
Rod gap lightning arrester


The distance between rod and insulator must not be less than 1/3 of the gap length so the arc may not reach the insulator and damage it.

At a healthy operating condition gap between rod is non conducting but during the surge, gap spark over and conduct excessive current to earth. in this way surge energy dissipated into the earth.

Horn Gap Lightning Arrester

Horn-gap-type-arrester

Horn gap type lightning arrester consists of two horn-shaped metal rods separated by a small gap as shown in the diagram. The horns are constructed that the distance between horns increases gradually toward the top. this horn assembly mounted on the porcelain insulator and one end of horn connected to the line through choke and resistor. While other end connected to ground. The choke coil used which provides low reactance at normal frequency but high reactance to surge frequency/ voltage. due to this surge not reach to the transformer or the equipment which to be protected.

Horn-Gap-Lightning-Arrester
Horn Gap Arrester


Gap length between horns is kept such as normal voltage does not enough to cause spark over of gap. 

Valve Type Lightning Arrester

An improved but more expensive surge arrester is the valve type arrester and is extensively used on the system operation on higher voltages. The diagram shows valve type lightning arrester contains numbers of series-connected gaps, coils units, and the valve elements of nonlinear resistance material usually made of silicon carbide discs. the nonlinear resistors are connected in series with the spark gap and all this assembly fitted in the tight porcelain container.

Valve-Type-Lightning-Arrester
valve type lightning arrester

Spark gap consists of a number of similar gaps in series. each gap consists of two electrodes with gap spacing. The voltage distribution across the gaps linearised by using additional resistors called grading resistors.

The gap between two electrodes does not spark during normal voltage but on the occurrence of the high surge, the air between the gaps breaks down forming an arc between electrodes. this arc carry surge current to ground through nonlinear resistors. Nonlinear resistors offer high resistance to current at the normal operating voltage and very low resistance to surge current.

Expulsion Type Arrester:


Expulsion type arresters also called a protector tube and normally used on the voltage up to 33Kv. this type of arrester consists of a rod gap in series with an additional gap which is enclosed in fiber tube. A fiber tube is made of two electrodes. the upper electrode connected to the rod gap and a lower electrode connected to the ground.

When a surge voltage is an incident on an expulsion tube, the series gap is spanned and an arc is formed between the electrodes within the tube. in this way surge current conducted into the ground.

Read. What is Lightning Arrester

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