Practical Applications of High-Voltage Surge Arrester

Practical Applications of High-Voltage Surge Arrester

I. Core Function: Not "Avoiding" but "Diverting" and "Limiting Voltage"

A key concept must be clarified first: High-voltage surge arrester do not prevent lightning from striking equipment. Instead, they provide a low-impedance path to discharge the massive energy from lightning strikes or switching over-voltages and limit the voltage across the equipment to a safe level. This protects the insulation of expensive electrical equipment from breakdown.

Think of it as an "intelligent safety valve": Normally completely closed (high impedance), it doesn't affect the system. The instant the system voltage exceeds a dangerous level (e.g., during a lightning strike), it opens completely (low impedance) instantaneously, diverting the current and "clamping" the voltage. Once the danger passes, it rapidly closes again.

II. Primary Application Sites and Equipment Protection

Substations / Converter Stations (Core Application Area)

21. Protecting Transformers (The Most Critical Task): Transformers are the heart of a substation and are of the highest value. Arrester is installed directly near transformer bushings to protect their main and longitudinal insulation from incoming surge damage.
21. Protecting High-Voltage Switchgear: Such as circuit breakers, disconnect switches, instrument transformers (CTs/VTs). The insulation levels of this equipment are relatively low, requiring arrester to limit over-voltages.
21. Protecting Busbars: Arrester installed on busbars provide protection for the entire switchgear assembly.
21. DC Converter Stations: Use dedicated DC arrester to protect core equipment like converter valves and smoothing reactors. Their operating conditions are more complex than on the AC side.

Transmission Lines

21. Line-Type Arrester: Installed directly in series or parallel near insulator strings, especially in areas with high lightning activity, high soil resistivity, or on towers prone to strikes or critical crossing sections (e.g., spanning large rivers, railways, highways). They significantly improve the lightning withstand level of the line and reduce the lightning trip-out rate.
21. Incoming Line Protection: Within the first 1-2 kilometers of the transmission line entrance to a substation, measures like strengthening shield wires, reducing grounding resistance, and installing arrester form an "incoming line protection section." This weakens and limits the steepness and amplitude of incoming lightning surges.
21. Power Plants

Protecting Generators / Motors: Generator insulation has a lower withstand capability than transformers. "Generator-specific arrester" are typically used, often combined with capacitors, to protect them from lightning surges coming from overhead lines and system switching over-voltages.

Protecting Station Service Transformers and Auxiliary Systems.

Electrified Railways

Protect traction substation transformers and rectifier equipment, as well as the catenary system, ensuring stable and safe railway power supply.

21. Industrial Users

At the entrance of high-voltage distribution rooms in large factories, mines, etc., and near critical equipment (e.g., large motors, variable frequency drives), arrester is installed to prevent production interruptions and equipment damage caused by external lightning surges and internal switching over-voltages.

Distributed Renewable Energy Stations

21. Wind Farms: Turbines located in open fields or on hilltops are prone to lightning strikes. Arrester is required in the nacelle, at the base of the tower, and in pad-mounted transformers to protect generators, converters, and control systems.
21. Photovoltaic (PV) Power Stations: Dedicated arrester is required on both the AC and DC sides of DC combiner boxes and inverters to protect expensive inverters and PV modules.

III. Key Technologies and Considerations in Practical Application

Type Selection: The current mainstream is the Metal Oxide Arrester (MOA), which is gapless, has fast response, excellent protective performance, and high discharge capacity.

Installation Location:

21. As Close as Possible to the Protected Equipment: To shorten the protection distance and avoid "protection gaps" caused by voltage drops on connecting leads.
21. Grounding Must be Excellent: The arrester's ground terminal must be connected to the substation or system grounding grid via the shortest path with the lowest impedance. Poor grounding can drastically reduce protection effectiveness or cause failure.

Coordination with Other Protective Measures:

21. Arrester is the last line of defense. They work together with lightning rods/shield wires (for direct strike protection), grounding grids, and Surge Protective Devices (SPDs, for low-voltage fine protection) to form a complete lightning protection system.
21. Insulation Coordination: The protective level (residual voltage) of the arrester must be lower than the insulation withstand level of the protected equipment, with a certain safety margin.

Monitoring and Maintenance:

Modern arrester is often equipped with leakage current monitors or online monitoring devices. By monitoring changes in resistive current, potential issues like valve block aging or moisture ingress can be detected early, enabling condition-based maintenance.

Regular preventive tests like infrared thermography, DC reference voltage, and leakage current measurements are conducted to ensure they are in healthy condition.

IV. Summary

The practical application of high-voltage surge arrester is a cornerstone of the safety and stable operation of power systems. Their core value lies in:

21. Ensuring Reliability: Significantly reducing equipment damage and power outages caused by lightning and over-voltages.
21. Economic Benefit: Protecting core equipment worth millions or even billions with relatively low-cost devices (arrester).
21. Technical Importance: They have evolved from simple spark gaps to intelligent metal oxide devices, deeply integrated with online monitoring technology, becoming important state-awareness nodes in smart grids.

 

In short, wherever there is high-voltage electrical equipment, arrester protection is needed. Their presence can be seen in every link of the chain: power generation, transmission, transformation, and consumption.