How does a surge arrester work?

A surge arrester diverts lighting and switching surges by metal oxide varistors inside its housing. MOVs (metal oxide varistors) are no-linear semiconductors. MOVs work as an insulator at normal voltages and the current cannot pass through it. MOVs start acting as a resistive conductor, while overvoltages occur. The overvoltages will be diverted to the ground.

What is the purpose of a surge arrester?

Line surge arresters (LSA) are designed to prevent ground faults and short circuits in power lines caused by lightning or switching overvoltages. Insulator flashovers, voltage dips and interruptions are prevented by eliminating all lightning and switching overvoltages above the insulator insulation level.

Line surge arresters

Q: Where should surge arresters typically be installed?

The line surge arresters are installed at recommended locations along the line in accordance with the line simulation, and ensures anhanced overvoltage protection. Selecting the optimum line surge arresters, especially in terms of their quantity and installation locations, significantly improves the reliability of the overall line system and the quality of power that it supplies.

Q: Up to what system voltage can Siemens Energy line surge arresters be used?

Siemens Energy offer line surge arresters for system voltages up to 800 kV and an energy discharge capability of 3.6 C.

Installation of line surge arresters at recommended locations along the line in accordance with our line simulation ensures anhanced overvoltage protection. Selecting the optimum line surge arresters, especially in terms of their quantity and installation locations, significantly improves the reliability of the overall line system and the quality of power that it supplies. We offer line surge arresters for system voltages up to 800 kV and an energy discharge capability of 3.6 C.

Improve lightning protection performance
Reduce outages caused by poor grounding and high lightning activity
Reduce double-circuit outage rates / protect underbuild distribution lines
Provide switching surge control - structural optimization and lower clearances
Improve safety - prevents personal injuries and damage to equipment
For line upgrading and compaction - reduced insulation levels
For live work on the line -temporarily reduce minimum approach distance
Achieve lower installation costs and losses in line system (outages)

Non-gapped line surge arresters (NGLA) offer a high degree of mounting flexibility and operational reliability. Depending on the tower design and the arrangement of insulators and lines, these arresters can either be installed directly on the insulators or on the tower. NGLAs limit overvoltages to value levels below the insulator withstand voltage.

Benefits:

Most flexible solution (installation at conductor, tower, insulator etc.)
Offer a very high level of protection against lightning and switching overvoltages thanks to their high energy absorption capacity
A disconnector is installed in series that disconnects the arrester in case of thermal overload
This ensures further operation of the overhead line until a replacement can be scheduled
Designed and tested to comply with the latest IEC 60099-4 standard

Siemens Energy EGLA line surge arresters have an external spark gap placed in series that galvanically isolates the active part of the line surge arrester from the line voltage under normal conditions.

In case of lightning, the spark gap flashes over and the arrester limits the ground fault current from several kA to a few amperes, and extinguishes the arc within 10 ms such that no circuit breaker operation at both line ends is needed, i.e. no reclosing operation.

Benefits:

No leakage current, since the series gap disconnects the arrester part of the EGLA - metal-oxide varistor (MOV) blocks - from the system voltage under normal service conditions
Lower arrester rated voltage required (arrester is not energized all the time, i.e. it's insulated by the series GAP)
--> less material and fewer MOVs are needed
No disconnector and no ground lead are needed
Suitable for multiple-circuit towers with short clearances - the highly compact design of the EGLA and the absence of a ground lead allow installation and lightning protection even on towers with very small cross-arm clearances
Better suited for live installation
Complete EGLA solutions with polymer insulators also available
Designed and tested to comply with the latest IEC 60099-8 standard

Siemens Energy optionally offers software analysis (simulation) based on Cigré studies to examine and conduct preliminary tests of customer-specific applications as a way of determining the optimal, cost-effective solution. With this approach, the customer only needs to equip particular phases or individual line segments with line surge arresters, and can still ensure sufficient lightning protection of the overhead line.

In the first phase of an analysis, all important parameters of the transmission line under study are entered into the simulation software, and the installations to be examined are selected. This approach takes the following factors into consideration:

Line parameters: operating voltage, number of three-phase circuits, ground wire data, length, span length and sag on line, conductor type, diameter, and clearances
Tower data: tower surge impedances and footing resistance, tower geometry (position and distances of the individual phases and any existing ground wires)
Insulator data: arcing distance, connection length, rated lightning impulse withstand voltage
Lightning activity: keraunic level (lightning strokes per year and km²), network topology (elevation profile)
Customer priorities: fewer short interruptions, prevention of phase and multisystem short-circuits, elimination of ground wires

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A lightning strike or an electrical surge can cause several irreversible damage to electrical devices, when this lightning strike or electrical surge is above the certain insulation level of devices. The main task of a surge arrester is to limit the overvoltage and protect the valuable equipment. With the help and the correct implementation of surge arresters, lightning strikes and surges cannot damage the system or device.

Line Surge Arresters (LSAs) are increasingly used to improve the service security of transmission lines and therefore the system stability in cases where the following problems are present:

• High ceraunic level (high ground flash density).

• Poor earthing conditions of towers.

• High switching surges on EHV lines.

• Danger of double flashovers (shorts between 2 systems).

A cost effective line upgrade is possible without substitution of insulators and

without adding shield wires.

Externally Gapped Line Arrester (EGLA) operates above a defined minimum lightning impulse value, but this value is below the flashover (Critical Impulse Flashover) of the insulators. Overvoltage below this level will not lead to any flashover along the line, i.e. they are not relevant.

None Gapped Line Arrester (NGLA) operates permanently for all kinds of overvoltage (lightning impuls &switching impuls).

If the line is equipped with sufficient LSA (EGLA/NGLA) based on line-study results, it can become foolproof system against all flashover failures.

Line surge arresters

Overvoltage protection by line surge arresters

Beneficial applications of line surge arresters

Two different LSA designs are available

Siemens Energy EGLA line surge arresters have an external spark gap placed in series that galvanically isolates the active part of the line surge arrester from the line voltage under normal conditions.

Software analysis for customer-specific applications

Watch our video

Downloadable resources for you

Get in touch with us

Get answers: FAQs on line-surge arresters

Line surge arresters

Overvoltage protection by line surge arresters

Beneficial applications of line surge arresters

Non-Gapped Line Arrester (NGLA) – Directly connected to the overhead line

Externally Gapped Line Arrester (EGLA)– Insulated from the high-voltage line by series gap

Software analysis for customer-specific applications

Downloadable resources for you

Get in touch with us

What is a surge arrester?

How does a surge arrester work?

What is the purpose of a surge arrester?

Where should surge arresters typically be installed?

What are line surge arresters and what do they protect against?

Up to what system voltage can Siemens Energy line surge arresters be used?

How does the line surge arrester operate during a lightning event?