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.

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.

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.

Transmission Line Surge Arresters | Overvoltage Protection up to 800 kV

Key functions:

High voltage capability: designed for system voltages up to 800 kV with an energy discharge capacity of 3.6 C.
Lightning protection: externally gapped spark gap flashes over during lightning events, limiting ground fault currents from several kiloamperes to just a few amperes, extinguishing arcs within 10 milliseconds, and avoiding circuit breaker operation.
Enhanced system reliability: Siemens Energy proprietary simulation software, based on Cigré studies, optimizes LSA placement and quantity, ensuring robust lightning protection while minimizing costs.
Reduced power interruptions: LSAs eliminate overvoltages above the insulator’s lightning-impulse withstand level (LIWL), preventing insulator flashovers and voltage dips, thereby improving power quality and reducing outages.
Advanced simulation and support: detailed software analysis models customer-specific line conditions, enabling precise LSA selection and placement for maximum effectiveness.

Non-gapped line surge arresters (NGLA) provide exceptional mounting flexibility and high operational reliability. Depending on tower design and insulator arrangements, NGLAs can be installed directly on insulators, conductors, or tower structures. They effectively limit overvoltages to levels below the insulator’s withstand voltage, preventing flashovers and equipment damage.

Key benefits:

Highly flexible installation: suitable for mounting on conductor, tower, or insulator, adapting to various line configurations.
Superior protection: high energy absorption capacity ensures robust defense against lightning and switching overvoltages.
Thermal overload safety: integrated disconnector isolates the arrester during thermal overload, allowing continued line operation until replacement.
Standards compliance: designed and tested according to the latest IEC 60099-4 standard for surge arresters.

Surge arrester - Non-gapped line arrester (NGLA)

Siemens Energy EGLA surge arresters feature an external spark gap in series, which galvanically isolates the arrester’s active components from the line voltage under normal conditions. Upon lightning strike, the spark gap flashes over, limiting ground fault current from kiloamperes to amperes and extinguishing the arc within 10 ms. This rapid arc quenching prevents circuit breaker trips and eliminates reclosing operations.

Key benefits:

Zero leakage current: the series gap disconnects the metal-oxide varistor (MOV) blocks from system voltage during normal operation.
Material efficiency: lower rated voltage arrester required, reducing MOV quantity and overall material use.
No disconnector or ground lead needed: simplifies installation and maintenance.
Compact design: ideal for multiple-circuit towers with short clearances; enables live-line installation.
Complete solutions: available with polymer insulators for enhanced performance.
Standards compliance: conforms to the latest IEC 60099-8 standard for externally gapped surge arresters.

Surge arrester - Externally gapped line arrester (EGLA)

Feature	NGLA	EGLA
Installation	Direct connection	External spark gap
Voltage range	Up to 800 kV	Up to 800 kV
Energy discharge	Up to 3.6 C	Up to 3.6 C
Disconnector	Built-in	Not required
Leakage current	Present (normal operation)	None (isolated in normal operation)
Standards	IEC 60099-4	IEC 60099-8
Housing	Silicone rubber	Silicone rubber
Mounting options	Tower, insulator, conductor	Tower, insulator
Maintenance	Minimal	Minimal

Siemens Energy 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

Siemens Energy transmission line surge arresters are designed to provide unparalleled protection and reliability for power systems worldwide. With a legacy of proven technology and decades of field experience, our surge arresters are engineered to meet the rigorous demands of modern electrical infrastructures.

Here’s why Siemens Energy is the trusted choice for transmission line surge protection:

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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.

Transmission line surge arresters

Overview of transmission line surge arresters

Siemens Energy transmission line surge arrester portfolio

Technical highlights and benefits

Optimized software analysis for transmission line surge arrester applications

Why choose Siemens Energy transmission line surge arresters?

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