Arcing is defined as a flow of current from one conductor to another, where air is worked as a medium for the current. Potentially it starts at as low as 5 volts, but there should be a flow of follow-on current. Only two technical causes of arcing or flares are defined. However, there are many other factors around the substation that enhance the probability of these causes. The two technical causes of arcing or flares are as follows:
Image substation- nasaimages.org
- Noise – if a connection produces noise, a change in the way the current flows is produced. This is because current tries to force its flow to the other side of the connector. This force, applied by the current, directly translates into heat. This heat causes burning of the metal surface and arcing starts there.
- Vibration – when the connectors start vibrating, they start making and breaking contact. This problem introduces arcing inside the connectors and because of successive oxidation, it becomes worse. This increased arcing restricts current flow and due to this, starts burning of the metal surfaces.
- The main cause of arcing or flares is the decrease in quality of polymer insulators used in the substation. Polymer insulators are electrical devices composed of insulating sections of polymer materials and metal fittings. These insulators have an important role in the working of a substation. The qualities of polymer insulators are affected by environmental factors such as moisture, rain, sunshine, etc. The decreased quality insulator enhances arcing. Due to this, high quality polymer insulators, having high resistance to pollution, should be used in substations.
- In my opinion, all problems on earth can be related to pollution. Here also, we find that pollution is the biggest cause of arcing. Substations are surrounded by polluting elements such as coastal regions, industrial dust and gases, highway road salt, car emissions, agricultural dust and fertilizers, marshy land, etc. These elements enhance the probability of arcing, but at a slow rate.
- Porcelain insulators are also used in substations. When they get cracked due to external reasons, they do not perform properly and introduce arcing. Rusted metal caps and pins present on the porcelain insulator are also a cause of arcing. Maintenance of porcelain insulators is very essential to avoid arcing.
- Wrong design and improper installation are also important causes of arcing. These are the factors which are responsible for mechanical and electrical failure of substation elements such as conductor and corona rings because they introduce wear and tear. Obviously, failed components cannot work properly, and there starts the degradation of the substation and enhancement of the probability of arcing.
- Noise is also an important cause of arcing. The noise coming from outside such as RFI, TVI, and audio sources enhance the vibration of connectors, starting arcing. (Substations constructed far away from noisy places have a longer service life.)
- Small hardware such as spacers, slices, clamps, etc. are also used in substations. These hardware devices are used for the gripping and fixing of components of the substation. When this hardware gets loose, they start vibrating and these vibrations enhance the vibration of connectors. As we already know, the vibration of connectors is the technical cause of arcing.
- Shorted bells present in the substation are also considered a cause of arcing.
So these are the main causes of arcing or flare in a substation. Proper maintenance and regular inspection have an important role to prevent this problem. High quality polymer insulators that resist weather and pollution should be used in the substation. Dust, due to pollution, should be removed properly in a regular time period. There should be used well designed components so as to avoid unnecessary mechanical and electrical failure. Proper installation of those components is also necessary. All components should be gripped tightly to each other. There are available a variety of arcing detection instruments on the market, so a good detecting instrumentation should be used.
Protection of the substation from troubles such as arcing, flash-over, and corona results in many economic benefits. It increases service life of a substation, decreases maintenance cost, resists metal surface burning, and provides many other benefits by avoiding arcing.