Outdoor insulator and substation equipment become low voltage transformer when contaminated as a result of atmospheric pollution caused by, for example, saline, dust and ash 1 Atmospheric contamination and adherence to outdoor high voltage insulators and substation equipment can cause various problems such as erosion and surface degradation and even complete failure of the insulator 2 , 3 , 4 The use of non-ceramic insulators increased significantly in last five decades.
Low voltage outdoor lighting systems use only 12V of power, making them the most common for household use and are the best option for dramatic lighting effects. Administers Standards Testing Laboratory North America (STLNA) activities group to develop consistency for high-voltage product testing and promote global harmonization of switchgear and circuit breaker testing Standards. Indoor Substation: The indoor substations are generally of lower voltages and are built under a roof or closed compartment.
These days gas insulated substations are built for high voltage systems. Extra High Voltage Substations (EHV)- Involving voltages between 132 kV and 400 kV. High Voltage Substations (HV Substations) – Involving voltages between 11 KV and 66 KV.
Types of Substations by Operating Voltage Levels. As the name suggests, Converter substations contain equipment that changes the frequency of current from higher to lower and can also convert AC to DC or the reverse also. The distribution substations are located at the lace where voltages of primary distribution are being stepped-down.
Breakers for protections against earth faults too small to trip an over-current device: In 2012 ABB presented a 75 kV high-voltage breaker that uses carbon dioxide as the medium to extinguish the arc. 72.5 kV carbon dioxide high-voltage circuit breaker.
Such breakers would be useful to interconnect HVDC transmission systems. Due to environmental and cost concerns over insulating oil spills, most new breakers use SF6 gas to quench the arc. High-voltage breakers are broadly classified by the medium used to extinguish the arc:
The definition of high voltage varies but in power transmission work is usually thought to be 72.5 kV or higher, according to a recent definition by the International Electrotechnical Commission (IEC). 400 kV SF6 live-tank circuit breakers. Often used for main power distribution in large industrial plant, where the breakers are arranged in draw-out enclosures for ease of maintenance.
Air circuit breakers—Rated current up to 6,300 A and higher for generator circuit breakers. These breakers interrupt the current by creating and extinguishing the arc in a vacuum container – aka “bottle”. Vacuum circuit breakers —With rated current up to 6,300 A, and higher for generator circuit breakers application (up to 16,000 A & 140 kA).
Three-pole common trip breakers are typically used to supply three-phase electric power to large motors or further distribution boards. Two-pole common trip breakers are common on 120/240-volt systems where 240 volt loads (including major appliances or further distribution boards) span the two live wires. Large power circuit breakers, applied in circuits of more than 1000 volts, may incorporate hydraulic elements in the contact operating mechanism.