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Classification and Characteristics of Automatic Superposition

1. The classification of auto recloser


The automatic recloser is divided into single-phase and three-phase according to the number of phases; column type, underwater type, ground type and underground type according to the installation method; series and parallel type according to the division of energy. According to the control mode, it is divided into two categories: hydraulic control and electronic control.


(1) The classification of hydraulic control

The main advantages of hydraulic control are economy, simplicity, reliability, and durability. These advantages are important for power grids in rural places and some place where the equipment is installed remotely. These occasions for equipment maintenance are not convenient and frequent. In addition, the maintenance of hydraulic control switches does not require special tools, expensive instruments and complex technical training.


The hydraulic control of the superposition is divided into a single hydraulic system and a double hydraulic system. Single hydraulic arc extinguishing, insulation, operation counting, timing are using the same type of oil. Common transformer oil is used for double hydraulic arcing insulation and operation counting. Time keeping in slow operation needs a special aviation oil which has stable viscosity and is sealed in a closed system. The former is used for early single-phase reclosers and small-capacity three-phase reclosers; the latter is mostly used for larger-capacity three-phase reclosers.


(2) Electronic control auto recloser

The advantages of electronic control mode are flexible, multi-function, good interchangeability, stable protection function, wide range of choice and easy to use. This is of great significance to improve the protection cooperation, enhance the reliability of power supply, simplify the work of field personnel and advance the degree of operation automation. In addition, this kind of auto circuit recloser passes the current through the casing CT detection line on its top cover. There is no series coil in the main loop, so it is easy to pass the thermal stability test. The disadvantage is that it is more expensive and needs higher level of maintenance.


(3) Classification based on arc extinguishing mediums

Auto recloser is divided into three categories: oil, vacuum and SF6. Oil superposition is of multi-oil type and it has the longest running history. The arc extinguishing chamber structure has two kinds of single fracture and double fracture, generally using hydraulic control. The typical  type of products are OYT and RX. Vacuum arc extinguishing chamber was used in the design of recirculator in the 1960s, and the typical product is KFE type recirculator. It places the vacuum bubble in the oil tank for outdoor using and it is controlled electronically. The advantages of vacuum arc extinguishing chamber is that it can use for longer time, and there is no need for maintenance and fire prevention.


2. The characteristics of automatic superposition


Electronic control SF6 Auto recloser is a new technology developed in 80's. It combines the advantages of rotary arc type SF6 arc extinguishing principle and microcomputer technology. In the high voltage electrical appliance field, it reflects the trend of the combination of strong and weak currents. The arc extinguishing principle of rotary type SF6 can be realized by two kinds of structures. One is the insertion type, variable opening distance and another is the knife gate type, fixed opening distance. SF6 Auto recloser abroad adopt the latter. Its rotating arc coil is wound on a metal arc ring. The static contact is located in the center of the arc ring. The moving contact rotates along the radial arc ring. And the rotating shaft is connected with end of the rotating arc coil. When the moving contact and the static contact are separated under high current, an arc is generated. When the moving contact turns to the arc ring, the arc connects the arc coil to the conductive loop. The direction of the magnetic field generated by the coil is right angled to the arc. According to Fleming's law, under the action of magnetic field, the arc column rotates at a high speed along the tangential direction of the arc ring with the static contact as the axis, so that the arc constantly contacts the cold S F6 gas ionized in the future. The arc column energy is released by gas ionization, and the temperature of the arc column is reduced so that the arc is extinguished at the first time the arc current passes zero.


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