How to Select the Right Surge Arrester for Medium Voltage Distribution Lines
Selecting the Right Surge Arrester for Medium Voltage Distribution Systems.
One of the most vital aspects in the process of ensuring that a medium voltage distribution based communication system operates safely and efficiently is picking the right type of surge arrester. In other words, it is essential to note the importance of surge arresters since they offer protection to electrical distribution lines from being affected by voltage surges coming from natural or artificial sources such as lightning, switching activity, and system faults, among others. Therefore, this paper will highlight the various issues which must be considered when selecting a surge arrester with emphasis on the equipment which is used at the level of 11kV and 33kV.
Surge Arresters
A surge arrester is characterized as a device that prevents the damage of electrical equipment by diverting excess voltage to the ground through a protective medium. Surge arresters are meant to limit voltage peaks in order to minimize damage that can occur to electrical systems including components like transformers and circuit breakers. The most significant thing that should be taken into consideration concerning surge arresters is that many people think of them as lightning arresters, while these two devices complement each other. Despite the fact that the two types of devices are often confused, surge arresters are mostly used to control transients instead of lightning arresters, which play the role of protecting the system against shocks of lightning.
Key Factors to consider before choosing Surge Arresters.
1. The Nature of System Voltage Level.
Understanding the system voltage level is needed for shock arresters selection. For mid-voltage systems like those of 11kV and 33kV systems, it is crucial to choose devices rated under this criterion, since selection parameters will depend on this issue because of the need to ensure compatibility and safety.
2. MCOV Determination:
MCOV defines the voltage due to surges. The selected surge arresters should be capable to take any surge above the MCOV rating. It is optimal to use surge arresters, which are rated higher than peak working voltages. As a rule of thumb, surge arresters are chosen with MCOV ratings of 10 to 20% more than the standard voltage pattern they would usually operate on.
3. Energy Capacity:
The energy handling capacity of the surge arresters has to do with the quantity of energy, it can take from the surges. This is usually measured in kilojoules (KJ). It is very important to use the appropriate arresters with enough energy capacity especially when dealing with frequent transients.
4. Environmental factors:
The conditions of the environment where the surge arresters are going to be applied very much affects the kind of selection of surge arresters to be made. The environmental conditions may include climatic factors like temperature, level of humidity, and pollution level of the environment among others. For example in the case of application of the surge arresters in the coastal region, salinity of the soil is a factor that should be considered during the installation.
5. Installation Location:
Installing surge arresters at the appropriate site is of utmost importance for their proper functioning. It is important to install surge arresters as closely as possible to the equipment to be protected from urgent electrical surges.
Surge Arrester versus Lightning Arrester
The surge arresters serve similar functions as lightning arresters but they differ significantly in the way they operate. Whereas surge arresters protect electrical equipment from surges associated with triggered electrical surges activated by voltage changes, lightning arresters route electrical surges caused by lightning strikes directly to the ground.
Frequently Asked Questions
Selecting a Proper Surge Arrester for 11kv/33kv Systems
Choosing the best surge arresters for a particular voltage system requires identifying the voltage levels within a certain voltage range.
How long do surge arresters last?
The useful lifetime of the arresters is between 10 and 15 years old.