Application status of outdoor medium voltage switc

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Application status of outdoor medium voltage switchgear in China

outdoor medium voltage switchgear is mainly used in agriculture and urban-rural areas. As China's rural power accounts for about 1/3 of the total power, there are many outdoor medium voltage switches, and the market is large. The annual consumption of outdoor medium voltage switches in China is about 40000 sets. According to the agricultural characteristics, two mode schemes are specifically adopted: the first scheme is the short-term scheme, the column SF6 or vacuum circuit breaker and integrated centralized control device are adopted at the l0kV side, and the oil or oil-free circuit breaker is adopted at the 35kV side; The second plan is the long-term plan. Reclosers and sectionalizers are used at 10kV side, and fuses and load disconnectors are used at 35kV side

at present, more than 90% of rural substations in China are in the first scheme, while the second scheme has an obvious growth trend of production commissioning in January next year

the rural voltage level is 110kV → 35kV → 10kV → 220/380V. Among them, 110kV uses circuit breaker or GIS, which has no difference in the same city. 35kV and 10kV products are unique. For example, 10kV products are column mounted and 35kV circuit breakers are floor mounted. In the second scheme, the 35kV load disconnector + fuse can also be arranged on the column

for the electric power with nominal voltage of 10kV and 35kV, the rated voltage and the maximum working voltage of the high-voltage switch used shall be 12kV and 40.5kV under the goal of automobile environmental protection and lightweight. In the two grades with low waste quality in China, SF6 switch and vacuum switch, as two pillars, have replaced the original multi oil switch. The products include circuit breakers, reclosers, sectionalizers and load disconnectors

the characteristics of agricultural switch are different from those of urban switch. It belongs to small capacity, miniaturization, outdoor type and column installation. Since agricultural switches are mostly installed on columns, there is no need to build workshops, which can save 30% ~ 40% of the area and cost. However, agricultural switches are mostly installed outdoors, so the problem of external insulation of outdoor switches must be solved

at present, column switches in the market have less oil output, various forms of bubbles and different performances. It can be divided into the following categories:

① it can be divided into domestic and imported according to the country of production

② it can be divided into circuit breaker and load switch according to the arc extinguishing capacity of contact

③ according to arc extinguishing medium, it can be divided into vacuum and SF6

④ it can be divided into oil insulation, air insulation and SF6 insulation according to the insulation medium

⑤ according to the operating mechanism, it can be divided into electromagnetic operating mechanism, spring operating mechanism and permanent magnetic operating mechanism

⑥ it can be divided into circuit breaker, recloser, sectionalizer and load disconnector according to the use function of the product

⑦ according to the material of outgoing line bushing, it can be divided into porcelain bushing and silicone rubber bushing

characteristics of various switches:

1 domestic switches

are designed and manufactured according to the use characteristics of domestic power systems. Generally, the spring operating mechanism is used for electric and manual opening and closing operations. The secondary current of current transformer shall be designed as 5A; Multiple groups and changes can be set to meet different requirements of relay protection, telemetry and metering. Generally, the switch itself is equipped with a knife switch, and there is an operation lock between the switch and the knife switch

2 inlet switch

the common points of all inlet switches are: ① the secondary current of current transformer is designed as 1a. Generally, there are two options: 600/1 and 1000/1. ② All switches are not equipped with knife switches. ③ Equipped with dedicated operation controller. The controller has complete control and protection functions and strong selectivity, which is conducive to the protection cooperation between the upper and lower levels. ④ SF6 gas insulation under zero gauge pressure is adopted, which is not affected by external environment. The manufacturing process of the operating mechanism is fine, and most of them are sealed in the SF6 gas cavity, which is maintenance free on site

3 circuit breaker, recloser, load switch, sectionalizer

circuit breaker: it has strong arc extinguishing ability. It can close and cut off the fault current. The controller with microcomputer protection is equipped to protect the branch line

recloser: the switch body is exactly the same as the circuit breaker. The difference lies in the function of the controller. The controller function of the circuit breaker is simple. It can only control the line current and protect the site. Other functions are realized by FTU. In addition to all the functions of the circuit breaker controller, the recloser controller also has its own functions. It has the reclosing function of more than three times, a variety of characteristic curves, phase judgment function, connection function with the automation system, etc. The price is high

load switch: it can turn on the fault current and turn off the rated load current. There are two types of vacuum and SF6 arc extinguishing. It is mainly used as line section switch. Equipped with an intelligent controller, it becomes a sectionalizer. Low cost

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