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Basic knowledge of box-type substation

Word:[Big][Middle][Small] QR Code 2020/5/20     Viewed:    

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  I.Introduction

  Box-type substation is a new type of complete equipment that can penetrate into the load center as power reception and distribution.Its application has just begun in China.It adapts to the development of power system transmission and transformation equipment towards oil-free,miniaturized,low-loss,low-noise,complete,pollution-free,and maintenance-free.It occupies less space and is installed.The advantages of rapid and convenient,reliable operation,convenient movement,and low investment are increasingly trusted and affirmed by users,and are being widely used.

  2.Structure performance of box-type substation

  Box-type substation is composed of high-voltage switchgear,transformer,low-voltage switchgear and power compensation device,etc.,which constitutes a compact transformer and distribution complete set in one or several boxes.It is mainly used to replace the traditional civil-built substation and realize the function of substation and distribution.At present,it is mainly used for users of 3-35KV power distribution system.The high-voltage line enters the box-type substation.After passing through the high-voltage switch,the transformer changes to low voltage,and then passes through the low-voltage main switch and branch switch to the final power equipment.There are many specifications of box transformers,which can be classified as:

  1)From the wiring scheme:it can be divided into three schemes:single-ended loop,double-ended loop,and ring network loop.

  2)According to the conditions of use:it can be divided into indoor and outdoor forms.

  3)According to the structure:it can be divided into one type and split type.The integral type is mainly used for outdoor,and the split type is mainly used for indoor.

  4)From the shell:can be divided into steel plate shell,composite plate shell,aluminum alloy shell,etc.

  3.Characteristics of box-type substation

  Box-type substation is a combined complete product,which has the following characteristics compared with conventional equipment:

  1)Compact structure,less investment,and less land occupation.Since the box change is to arrange a large part of the power distribution device in a closed box body,through optimized design and reasonable combination,the insulation distance between the components is greatly reduced.It compresses the occupied area and occupied space.The box transformer covers an area ofabout 6-10M2 and can be placed directly on the green belt.Relevant design data shows that compared with traditional civil-built substations,the use of box-type transformers can reduce land occupation by about 80%,and save about 60%of land acquisition and building costs.

  2)Easy installation and fast construction.The main components and secondary wiring of the box transformer are assembled at the manufacturer,and are shipped to the site after passing the commissioning and factory test.During installation,just hang it on the civil foundation and fix it,and it can be installed within one day.Put into operation,the installation is greatly simplified,the workload is greatly reduced,the construction progress is accelerated,the installation period is shortened,the construction cost is saved,and it has significant economic value.

  3)Higher reliability and safety.The electrical equipment of general conventional substations,because they are outdoors for a long time,their insulation and conductors are susceptible to deterioration due to atmospheric pollution.Due to the characteristics of the structural design of the box transformer,the conductor,internal insulation,contact parts,etc.are completely enclosed in the box.The protection level of the shell can generally be IP2X and IP3X or higher,which is not easily affected by external pollution,and is not easy to be affected by wind,dust and rain.,Salt damage,fog damage,damage and accidents caused by animals and external forces,high reliability.No exposed live conductors are exposed outside the box,which will not cause foreign objects to short-circuit and risk of electric shock.There are complete five-proof measures on the high-voltage side,with mechanical and electrical interlocks,and high safety.

  4)Strong universal interchangeability.The high and low voltage schemes of the box transformer are complete,and the line schemes between the high and low voltages can be arbitrarily combined;the high and low voltage equipment and components can be selected from various famous or imported products;the transformer can be selected from dry or oil-immersed transformers,and the electrical components are universal and interchangeable Sexuality.

  5)Convenient operation and maintenance.Each room has an automatic lighting device.The transformer room has a track and a transformer trolley,which is convenient for the installation and replacement of the transformer.Open the box door to maintain the high and low voltage room.

  6)Flexible cable access.High-voltage lead-in adopts cable or overhead line,low-voltage lead-in adopts cable,lead-in and lead-out cable can be buried directly or channel laid to high-voltage power supply and users,and can also be led to electric pole.

  Fourth,equipment selection

  1)High voltage switchgear

  There are two ways to configure the high-voltage switchgear in the box substation:one is a circuit breaker,and the other is a load switch plus a fuse.Due to the large size,high price,and large maintenance workload of the circuit breaker,the second method is recommended in general design.The first method is used only when there are higher requirements.High-voltage switchgear can use domestic switches or imported switchgears.

  2)Transformer

  Transformer can use oil-immersed transformer or dry-type transformer.A dry-type transformer is recommended.The dry-type transformer has the characteristics of low loss,low noise,and no oil.It can avoid the leakage and explosion of traditional oil-immersed products and cause pollution to the environment.There is no fire hazard and it has good environmental protection value.When selecting a transformer,it is recommended that the transformer be equipped with temperature display,temperature control,fan and zero sequence protection equipment.

  3)Low voltage switch

  There are many kinds of low-voltage switches,and users can choose according to their needs.It is recommended that low-voltage switches have tripping coils and leakage protection functions.

  4)Protection

  The configuration of protection can be configured according to the needs of users.It is recommended that the box transformer has the following monitoring,alarm,control and protection methods:

  High-voltage equipment is equipped with high-voltage current-limiting fuse protection,single-phase short-circuit protection,overload protection and five-proof safety protection.

  The transformer is set with high-temperature starting fan,trip protection(high-voltage switch trip)and zero sequence protection.

  Low-voltage equipment installed with main switch has overcurrent trip,shunt trip,branch switch overcurrent trip and leakage protection.

  Box transformer is equipped with emergency trip button and accidental sound and light alarm.Acousto-optic alarm signal is taken from transformer short circuit,zero sequence,temperature protection,high voltage circuit breaker fault protection,low voltage main switch overcurrent protection,branch switch overcurrent and leakage protection.

  V.Application prospects

  The box-type substation has the advantages of less floor space,quick and easy installation,excellent electrical and mechanical performance,neat and beautiful appearance,and low investment.It can penetrate into the load center and can be used in urban public buildings,concentrated residential areas,factories,mines,and oil fields.,Construction sites,roads,ports and other low-voltage distribution sites.It is expected that there will be a broader application prospect in the near future.

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