Current situation, selection and application of th

Abstract: through the analysis and comparison of the structure, performance and standards of circuit breaker, knife switch (electric) and automatic transfer switch, this paper points out that the ideal electrical product used in the switching of two-way power supply is PC level ATSE

key words: current situation selection and application of transfer switch

1 current situation of ATSE products at home and abroad

automatic transfer switching appliance (ATSE) is mainly used in emergency power supply system. It is a switching appliance that automatically changes the load circuit from one power supply to another (standby) power supply, so as to ensure the continuous and reliable operation of important loads. Therefore, ATSE is often used in important electric fields, and its product reliability is particularly important. Once the conversion fails, it will cause one of the following two hazards: short circuit between power supplies or power failure of important loads (even short-term power failure), and the consequences are serious. This will not only bring economic losses (halt production and financial paralysis), but also may cause social problems (put life and safety at risk). Therefore, industrial developed countries have put the production and use of automatic transfer switching appliances as the focus to be restricted and standardized

the research and production of automatic transfer switching appliances in China was still blank in the early 1990s, and there was no national standard. The domestic dual power conversion device is often replaced by the combination of contactors, circuit breakers and other products by the design and complete set departments. This kind of programmatic product often has great hidden dangers in its reliability and safety because it has not been tested and tested (especially when two contactors are used as two-way power conversion, the electrical interlocking is extremely unreliable, and once the pole locking fails, it will cause two power transformers to be connected in parallel, and the system power flow formed by the parallel connection of power supplies can seriously destroy the whole power supply system). After that, Tianjin low voltage electrical appliance company developed the automatic transfer switch composed of circuit breaker + mechanical chain + controller. Its progress is made by product substitution schemes and product test verification according to certain technical specifications, which greatly improves the reliability and safety of products. In the mid-1990s, the cycle was composed of two isothermal processes and two adiabatic processes. In view of the urgent need for high-performance and reliable automatic transfer switch products in the domestic market, Japan, France, Germany, the United States and other automatic transfer switch appliances successively entered the Chinese market, alleviating the market demand of our country to a certain extent

in recent years, China's automatic transfer switch electrical appliance manufacturing enterprises (especially CB level ATSE enterprises) have increased rapidly, and their product performance and product quality are different, which makes it difficult for the design and user departments to select and use AT1 The data of the built-in lighting system and inner box adopts the data of resistance to combustion; Improper use and selection of Se have caused great losses to national property. In order to standardize the production and selection of automatic switching on electrical appliances (ATSE) products, AQSIQ issued gb/t14048 in December 2002 Automatic transfer switching apparatus (equivalent to iec60947.6.) National standard, implemented on April 1st, 2003. This standard will be produced by ATSE in the future; A technical regulation document jointly followed by enterprises, design users and commercial activities will also be the technical regulation on which 3C certification is based

automatic transfer switch (ATSE) is divided into PC and CB. The world's advanced products representing PC level include ASCO and onan of the United States

ats-nzm from Moeller, Germany and Schneider, France represent CB level

at present, there are about dozens of domestic enterprises producing CB level ATSE products, such as Tianjin low voltage electrical company, Changshu Switchgear Factory, Wenzhou Sankai and Muller electric (Shanghai) Co., Ltd. The enterprises that produce PC level ATSE products include Guangdong Qizheng, Beijing No.1 low voltage electrical appliance, Shanghai Huanqi, etc

there are also enterprises that produce electric knife switches (for dual power switching) products, such as France Shuo gaomei, etc

atse generally consists of two parts: ① switch appliance body; ② Controller

1.1 switch appliance body

switch appliance body is divided into two categories:

the first category is CB level. It is composed of two circuit breakers and mechanical interlocking, with short-circuit protection function

the second type is PC level, integrated structure (three-point type). It is a special switch for dual power switching. It has the advantages of simple structure, small volume, self interlocking, fast conversion speed (within 0.2S), safety and reliability, but it needs to be equipped with short-circuit protection appliances

1.2 controller

controller also has two forms: one is composed of traditional electromagnetic relay; The other is digital electronic intelligent products. It has the advantages of good performance, adjustable parameters, high precision, high reliability and convenient use

see Table 1 for the comparison of several common ATSE products and electric knife switch products at home and abroad. Comparison table of common ATSE products and electric knife switch products 1

2 Analysis and comparison of product structure and selection of ATSE

at present, there are roughly three kinds of switching appliances used for two-way power switching in the domestic market: ① CB ATSE; ② PC level ATSE; ③ Knife switch (electric)

next, from the three aspects of product structure, performance and standards to be followed, CB level and PC level ATSE are divided respectively; PC ATSE and knife switch (electric) are compared and analyzed. It is not difficult to find that PC ATSE is an ideal two-way power switching electrical product

2.1cb level ATSE and PC level ATSE have the following differences

2.1.1 their mechanical design concepts are different

cb level is composed of circuit breakers, which are responsible for breaking the arc, and its machinery is required to trip quickly. Therefore, the mechanism of the circuit breaker has the problems of slipping and re screwing; PC products do not have this problem. The reliability of PC grade products is much higher than that of CB grade products

2.1.2 the circuit breaker does not bear the short-circuit withstand current, and the contact pressure is small

when the short-circuit occurs in the power supply circuit, when the contact is turned off, it will produce a current limiting effect, thereby breaking the short-circuit current; While PC ATSE shall bear overload current of 20ie and above. The contact is not easy to be rejected due to high pressure, so the contact is not easy to be welded. This characteristic is particularly important for the fire power supply system

2.1.3 there is a problem of power superposition in the conversion process of two power supplies

pc ATSE fully considers this factor. The electrical clearance and creepage distance of PC level ATSE are 180% and 150% (standard requirements). Therefore, PC level ATSE has better security

2.1.4 the selection angles of contact materials are different

circuit breakers often choose silver tungsten and silver tungsten carbide materials to match, which is conducive to breaking the arc. However, this kind of contact material is easy to oxidize, and the spare contact is exposed for a long time, which is easy to form an oxide that hinders conductivity and is difficult to drive away. Once the spare contact is put into use, the increase of contact temperature is easy to cause the switch to burn or even explode; PC ATSE fully considers the consequences of contact material oxidation

2.2 the difference between PC ATSE and knife switch (electric)

2.2.1 the two follow different standards

pc ATSE conforms to gb/t14048.11 automatic transfer switching apparatus. Knife switch (electric) complies with gb14048.3 switches, isolators, disconnectors and fuse combinations

2.2.2 different arc extinguishing systems

pc ATSE fully considers the possible secondary arc breakdown in the process of power conversion, so there are certain requirements for the contact opening distance, and it is required that the free gas of the arc should be discharged quickly. Otherwise, it is easy to cause short circuit between power supplies

2.2.3 the electrical performance requirements of the two are different

pc ATSE is under 6in current and 1.05ue voltage, and the number of on/off cycles is 12; The knife switch is turned on/off 5 times under 3ie/1ue. The electrical life and mechanical life of the two are also different. The electrical life of PC ATSE is at least 1000 operating cycles and 5000 mechanical life under the condition of 2in/1.05ue; The electrical life of the knife switch is only 200 times under the condition of 1in/1ue, and the mechanical life is 800 times. The electrical reliability of the two is different

2.2.4 the conversion speed is different

pc ATSE conversion speed is generally less than 0.3s; When the knife switch is used for dual power supply switching, the conversion speed shall not be less than 1s

2.2.5 different test methods

when conducting on and off tests, PC level ATSE is carried out under different power phase sequences (strict assessment of arc extinguishing ability); The knife switch has no requirements for phase sequence

through the above comparison, it can be seen that PC ATSE is an ideal power transfer switch product

3atse product application

with the economic development, the tolerance of modern life and modern industry to power failure is getting worse and worse. Foreign industrial developed countries (especially the United States) regard ATSE products as part of the power supply, and are very cautious about the selection and use of ATSE products. In the dual power emergency power supply system, PC level products are the first, and the switch is not allowed to stay in the middle during the conversion process (i.e. without zero position). Its purpose is to increase the reliability of the power supply

due to different types of standby power supply, ATSE selection should also be different

at present, there are three forms of domestic standby power supply: (1) electricity; (2) Generator set; (3) EPS (battery inverter). When the standby power supply is (2) or (3), its capacity is generally only 20% - 30% of the common power supply capacity. Generally, the controller of ATSE shall have the function of non critical load selection (as shown in Figure 1). QT is controlled by controller. QT opens before ATSE conversion and closes after ATSE return

Figure 1 emergency power supply system line

note: ① UN is the common power supply (electricity)

② UG is the standby power supply (generator)

③ QG is the fuse isolator

④ QT is the load selection switch, which is operated by the controller

⑤ DN is the controller

when ATSE is used at the end of the circuit and for the conversion of fire power supply, the overload of load shall have an alarm prompt function. The protection characteristics of its fuse (QG) shall match the load requirements

atse generally does not allow large motors or high inductive reactance load conversion. If the load of large motor is switched during operation, it will be subjected to huge mechanical stress when the phase difference of power supply is large. At the same time, the overcurrent caused by the back EMF generated by the motor may cause the fuse to fuse or the circuit breaker to trip. The solution is often resistance absorption or load reduction

Figure 1 is the ideal circuit diagram of ATSE in emergency power supply system. QG in the figure plays two roles in the circuit: one is short-circuit protection; The second is the maintenance partition

4 introduction to the new generation of PC level ATSE products

in order to provide ideal ATSE products to the majority of users, Shanghai Institute of electrical science and a number of domestic enterprises jointly developed a new generation of PC level ATSE products in China - hyq1 series automatic transfer switching appliances. This product is the first PC level ATSE product in China that is designed, produced and tested completely according to the new national standards. This series of products include 80A, 160A, 225A, 400A, 800A, 1600A

4.1hyq1 product features

(1) comply with gb/t14048 Standard of automatic transfer switching apparatus

(2) the product has strong adaptability to the environment and strong reliability:

wide working environment temperature: +55 ℃/~25 ℃, (2) the impact of vanadium price fluctuations on the cost of vanadium batteries

wide working voltage range: 70% ue~120% UE,

electromagnetic environment 1: public electricity

(3) the switch body structure is of building block type, with small volume, which is 1/3~1/2 of the volume of CB ATSE of the same specification

(4) the main contact system is a single pole double throw (three-point) structure, which is interlocked by itself and will not be connected to two power supplies at the same time

(5) the operating mechanism is a single coil two-way operation, with simple mechanism, fast switching speed and less than 150ms

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