20 kV Lightning Arresters: Essential Protection for Medium-Voltage Systems
A 20 kV lightning arrester—most people call it a surge arrester, and that’s more accurate—is a key device that protects electrical power systems. It mainly keeps safe the equipment that works at medium-voltage levels.
Its main job is to protect transformers, switchgear and other expensive equipment. These pieces of equipment can get damaged by sudden high voltages. Most of the time, these high voltages come when lightning hits power lines—or hits near them. Sometimes, they also come from switching work in the power network.
Operating Principle
During normal use, the voltage of the 20 kV system is much lower than the arrester’s trigger point. When that happens, the arrester has very high resistance. It acts almost like an open circuit, so the power system works normally without any problems.
The core of a modern 20 kV arrester is a set of Metal-Oxide Varistor (MOV) discs. Most of these discs are made from zinc oxide. They have a special trait—their relationship between voltage and current isn’t linear at all.
If a sudden high voltage—like a lightning surge—makes the voltage at the arrester’s ends hit a certain level (people call this level sparkover voltage), the resistance of the MOV material drops a lot. After that, the arrester becomes very conductive. It gives the strong surge current an easy path to the ground.
This way, the arrester sends the dangerous surge energy to the ground safely. It also keeps the voltage across the protected equipment at a safe level—people call this level residual voltage.
When the surge is gone and the system’s voltage goes back to normal, the MOV discs automatically get high resistance again. That cuts off the ground connection. So the power system can start working normally again.
Key Components and Selection Criteria
A regular 20 kV arrester has several parts:
MOV Block: This is the main part made of zinc oxide. It soaks up the surge energy.
Housing: It’s made of porcelain or polymer. It gives the arrester strength, protects it from the environment, and stops electricity from leaking.
Sealing System: It stops water from getting inside. This is very important—if the arrester is going to work well for a long time.
End Fittings: They let the arrester connect tightly to the power line and the ground.
When engineers choose a 20 kV arrester, they need to think about several important things:
Rated Voltage: This is the highest regular power voltage the arrester can handle without stopping.
Duty Cycle: This tells how well the arrester can handle sudden high voltages that don’t last long.
Nominal Discharge Current: This is the highest point of the lightning current—people use it to sort the arrester (like 5 kA or 10 kA).
Line Discharge Class: This shows how much energy the arrester can handle from switching surges.
Residual Voltage: This is the voltage you measure across the arrester when it releases the nominal current. A lower number here means the arrester does a better job of protecting.
Conclusion
The abimat 20 kV lightning arrester is a must-have for medium-voltage power networks. It helps these networks work reliably and last for a longer time. The arrester works well to stop sudden high voltages. This keeps equipment from breaking, cuts down on power outages, and makes sure electricity is delivered safely without stopping. To let these devices do their important protective job well, you need to choose the right one, install it the right way, and check it on a regular basis.
