What is a Surge Arrester? Explain its Working Principle and Types

What is a Surge Arrester?

A surge arrester, as the name implies, is a device which protects electrical devices by “arresting” or discharging surge currents caused by external (e.g., lightning) (or) internal (switching event) constraints. 

It is also known as a surge protection device (SPD), or, less typically, a (TVSS) voltage surge suppressor.

Surge arresters and lightning arresters are frequently confused because they perform nearly identical functions on paper. 

But while lightning arresters are set outside, surge arresters are installed inside.

Surge arresters are protective devices that limit the voltage on the equipment by discharging (or) bypassing surge current induced by lightning or a power surge. 

IEEE standard C62.11 & IEC standard 60099-4 specify the requirements for surge arresters. 

How do Surge Arrester Work?

All appliances & electrical devices operate within a predetermined voltage range. 

This is a range of operating voltages within which a specific device is designed to operate safely. 

If the voltage acquired by a device exceeds its permissible voltage range, the equipment may malfunction, damage its internal components, or even explode up in the worst-case condition.

These may result from multiple factors, such as

• Rusted or loose connections in house or building, 
• Wiring faults, 
• Poor power supply quality, 
• Interference, and so on. 

Most of the time, these oscillations do not surpass normal voltage ranges & are therefore not cause for concern. 

However, voltage variations may suffer significant dips and spikes as a result of lightning storms & switching over-voltages.

Surge arresters prevent over-voltages generated by lightning (or) switching surges. 

They are not intended to protect from a direct lightning strike, should one occur.

Instead, they provide some protection from electrical transients induced by lightning strikes that occur in the general region of the wire. 

In this way, surge arresters can divert transients comparable to those caused by lightning (or) incorrect switching in a high voltage system.

Despite the source of the overvoltage, a surge arrester acts in the same way. It either clamps surge to reduce the voltage that flows via its power system or directs it to ground. 

Some surge arresters on market now have a “surge counter” component that is a module which enables the device to detect the presence of a discharge.

A metal oxide varistor (MOV) surge arrester consists of many blocks. 

These MOV blocks function as an insulator for line voltage, similar to a voltage-controlled switch. 

When the voltage that the arrester experiences exceeds the MOV blocks start to conduct at the arrester’s reference voltage. 

MOV blocks are extremely non-linear, thus when the voltage goes below the reference voltage, conduction stops.

Characteristics of Surge Arrester

The electrical characteristics of surge arrester are as follows:

• Resealing voltage refers to the voltage across an arrester that interrupts current flow following a spark over.
• It has the maximum power frequency, ranging from 50 to 60Hz.
• Maximum continuous operating voltage.
• Rated short-circuit current.
• The nominal discharge current have 3 values: 5 kA, 10 kA & 20 kA.
• These are connected to the earth and life conductors.
• Surge arresters with voltages more than 52 kV can be supplied by the discharge operation counters.

Types of Surge Arresters

The first surge protection devices were rod gaps. Rod gaps are inexpensive but have several drawbacks: 

• They may not protect against quick fronts, 
• Produce sharp surges at sparkover, & 
• Cause a defect with each operation – they do not reseal. 

Silicon-carbide valve-type surge arresters use a silicon carbide non-linear valve element with series spark gaps.

Zinc oxide is a replacement for silicon carbide. 

ZnO arresters have a more prominent nonlinear characteristic than SiC & can be employed without series gaps because of their low current at nominal voltage. 

However, they are particularly good at reducing surge voltages.

There are three types of electrical system surge arresters: 

1. Secondary Surge Arresters, 
2. Distribution Surge Arresters, 
3. Intermediate Surge Arresters, and 
4. Station Surge Arresters.

1). Secondary Arrester

A secondary arrester has a voltage rating of less than 1000 volts. They provide additional surge protection in a domestic’s service transformer. 

According to estimates, the failure rate of a transformer is somewhere between 0.4 and 1 percent, with low-side surges being responsible for between 50 and 70 percent of all failures. 

Utilizing a secondary arrester, the failure rate can be greatly reduced.

2). Distribution Arrester

Distribution arresters possess the lowest protective powers of any arrester type. 

As a result, they are only utilized in medium voltage networks (or) for elbow and cubicle-mounted transformers.

In positions with strong lightning activity, heavy-duty surge arrester is employed to meet the demand. 

Places with less lightning typically can get by with standard duty arresters. In these conditions, an arrester mounted on a riser pole is used to help stop the voltage surge detected by the equipment & the system’s subterranean table.

3). Intermediate Arrester

Intermediate arresters are commonly employed in small substations (or) for under-ground cable protection. 

In addition, they are ideal for use with dry type transformers.

They can withstand high discharge voltages as well as having a high current resistance capacity, but of a lesser scale than secondary arresters.

Voltage Range: Intermediate arresters can be found in voltage ratings ranging from 3 to 120 kV.

4). Station Arrester

Station class arresters are most effective equipment for handling high voltages. 

Among all arrester types, they provide the highest discharge voltages and can sustain the most defective currents. 

Voltage Range: These arresters can be found in voltages ranging from 3 to 684 kV. 

Station class arresters can also be obtainable in a variety of cantilever strengths to suit a wide range of demanding applications.

What is Type 2 Surge Arrester?

To protect against over-voltages induced by atmospheric (or) switching activity, install a Type 2  surge arrester at the main incoming supply (unless the application needs Type 1 & at any of the electrical switchboard in excess of ten meters from upstream SPD (Surge Protection Devices).

What is Type 3 Surge Arrester?

Type 3 surge arrester protection rounds out the protection principle. As device protection, it restricts the last residual pulses that could damage the building installation (or) system. Type 3 SPDs are positioned directly upstream from the end device.

What is the role of Surge Arrester in Transformer?

A surge arrester safeguards system equipment like transformers & transmission lines against overvoltage and/or voltage spikes generated by lightning (or) switching surges.

Difference between Lightning Arrester and Surge Arrester

Lightning Arrester vs Surge Arrester

Lightning Arrester	Surge Arrester
Protects equipment against lightning strikes.	Protects equipment against transient voltage surges.
Positioned at the entrance to substations or buildings.	Installed near essential machinery (or) electrical lines.
Transfers high-voltage lightning energy to earth.	Limits transient overvoltage due to switching (or) failures.
Designed to withstand very high voltages from the lightning strikes.	Designed to handle lower transient overvoltages.
Acts against the natural lightning occurrence.	Protects against internal system surges (such as switching surges).
Generally includes spark gaps & resistors.	Includes metal oxide varistors (MOVs) and silicon carbide.
Specifically for direct current (or) high frequency disturbances.	Operates with power frequency & transient surges.
Utilized in outdoor applications such as substations & towers.	Utilized to protect systems both indoors and outside.