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The complexity of modern electrical systems makes them exposed to power surges and overvoltage. These electrical issues, even when they occur in a minority, can wreak havoc on your systems. That's where surge arresters protect your electrical equipment.
Ever wondered how surge arresters work? This blog post will break down the step-by-step working principles as well as how to maintain them.
A surge arrester is a protective device that is designed to divert excess current away from an electrical component. It acts as a watchman between your electrical component and power surges, such as those caused by lightning surges, overloads, and other malfunctions.
Metal Oxide Varistor (MOV) Blocks: A typical surge arrester consists of MOV blocks. These are the heart, or main part, of the surge arrester. It is made from Zinc Oxide (ZnO) granules and has nonlinear resistance, which changes with voltage. Its nonlinear resistance is responsible for its fast, automatic protection. During power surges, it has low resistance, while during normal voltage, it has high resistance.
Housing: The housing, or enclosure, is usually porcelain or polymer and is meant to contain the MOV blocks. It must withstand UV radiation, contamination, and weather to insulate and protect the internal components.
Rods and Holding Plates: Surge arresters have supporting rods and holding plates that encircle the MOV blocks like a cage.
Sealing System: The sealing system is in the form of a sealing ring and pressure relief diaphragm. Both are installed twice at either end of the surge arrester body. The sealing system prevents the inflow of moisture and contamination within the housing of the surge arresters. In the case of an overload, it acts as a fast-operating pressure relief device (PRD). It also provides a point of contact for the transfer of current from the surge arrester external connection terminal to the MOV block.
Grading Rings: Grading rings are installed at the high voltage terminal to control even voltage distribution from the high voltage end to earth.
Electrodes: Electrodes are conducting terminals enabling safe electrical and mechanical contact between the surge arrester and the power system.
Grounding System: This works to provide a safe conduction of excess current into the earth.
The core idea is that surge arresters remain passive during normal operation but swing into action once something goes wrong.
Normal Operation: At normal times, the voltage level is under the safe range. The MOV demonstrates very high resistance, acting like an open circuit, which allows current flow uninterrupted. However, in this condition, no current flows from the arrester to the ground.
Surge Detection: Anything can cause a voltage spike. It could be a lightning surge, switching operations, or an electric fault. When this happens, the voltage rises above the arrester's threshold. Furthermore, the MOV resistance drops sharply (demonstrating very low resistance).
Current Discharge: The excess current is redirected out of the equipment by the surge arrester. This way, your system does not receive the high voltage that would otherwise damage it. Instead, the arrester provides a low resistance to the ground. Thus, the surge bypasses sensitive equipment and minimizes negative impact.
Voltage Clamping: The surge arrester keeps the voltage at a safe level. This clamping prevents insulation breakdown of electronic equipment.
Recovery: Once the surge subsides and the voltage has returned to normal level, the MOV quickly returns to high resistance mode. The arrester goes back to its passive state, waiting for the next event.
The ability of the MOV to quickly switch from insulator to conductor in the blink of an eye makes it effective.
The voltage rating of the surge arrester must match that of the system. Underrated ones can become active early, overrated ones may never turn on.
The energy rating of a surge arrester tells how much energy it can absorb in a single surge event. Powerful surges, such as those caused by direct lightning, must be protected with high-energy-rated arresters.
The faster a surge arrester responds to a surge, the better the protection it gives. In the case of modern arresters, the time to activate is on the order of microseconds, or perhaps nanoseconds, causing minimal damage to equipment.
Humidity, temperature, UV rays, and pollution can deteriorate surge arresters, especially those installed outdoors. For a better performance, surge arresters are made with polymer housings. Polymer material offers high resistance to harsh weather.
Even a high-quality arrester will degrade with age, especially in conditions of frequent surges. Repeated surges can reduce the MOV's ability to clamp voltages. For long-term performance, regular checks and tests are required.
Poor grounding or loose connections can cause the failure of your surge arrester. Thus, arresters should be connected with short, direct, low-resistance ground paths to ensure fast discharge.
Some geographical areas have higher lightning activity than others. Areas sensitive to frequent surges need higher-rated arresters for maximum protection. When selecting arresters, consider local weather patterns to make a good choice.
Not all surge arresters are made equal. Some brands make better arresters than others. Opt for renowned brands such as Haivol Electrical when it comes to certified products. Our 6kV middle voltage zinc oxide lightning surge arrester possesses a nonlinear volt-ampere characteristic of zinc oxide to change resistance.
In transmission and distribution systems, surge arresters are installed at substations, on transmission towers, and along distribution feeders to protect them from breakdown. It guards underground cables as well, keeping the system reliable and minimizing expensive outages. Furthermore, it improves grid performance.
Factories, refineries, and manufacturing plants are designed to run on a steady power supply. Surge arresters are used in these cases to shield the heavy machinery from sudden voltage spikes. It also ensures that workers are safe and saves on downtime and equipment failures caused by electrical faults.
Wind turbines and solar farms are very vulnerable to lightning strikes as they are outdoors. As a result, surge arresters are used to protect inverters, solar panels, and power electronics from damage. It increases the longevity of renewable energy assets and ensures smooth energy transfer in grid integration points.
Mobile towers and data centers need to have a stable power source in order to store valuable information. Surge arresters are put in place to prevent loss of data and to guarantee the reliability of the system. Arresters also prevent hardware damage and service interruptions during a storm.
Conduct a visual inspection of your arrester. Examine the housing visually; watch out for any evidence of discoloration, cracks, burns, or, in case of a flashover. Moreover, run checks after a storm regularly to make sure everything is in its place.
The grounding system must be in place and free of corrosion to resist harsh weather conditions.
Maintain the housing by cleaning it of dust and contaminants on a regular basis.
You should replace worn-out parts of your arrester in order to ensure its optimum performance. Although there may be no signs of wear or cracks, you can always go with the manufacturer's recommendation on how long components last, as well as a rough estimate to the time when they need replacement.
The initial step is to measure the system voltage and also determine the surge current. Next, evaluate the level of risk depending on the location and equipment you are safeguarding. Finally, ensure that the surge arrester you have chosen will be compatible with your existing system and is according to standards.
Type 1 surge arresters on the service entrance are used to absorb high-energy surges. Type 2 surge arresters are installed at distribution panels to handle low-energy surges.
It is commonly referred to as the maximum continuous operating voltage (MCOV). It is the highest power-frequency voltage that the surge arrester can withstand continuously without damage.
Under normal conditions, surge arresters can last for up to 5 years. Their lifespan depends on how frequently they are exposed to surges and the kind of material they are made of.
Moisture, external flashover, aging, and lightning strike exceeding the arrester's design limits can cause it to fail.
Surge arresters are the unsung heroes in electric systems. Knowledge of how they work and what influences their performance will enable you to maximize protection. For more information on surge arresters and how to get one, contact Haivol Electrical.
