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what is metal clad mv switchgear?

Views: 0     Author: Site Editor     Publish Time: 2023-12-18      Origin: Site


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1.Metal clad switchgear overview

2.Switchgear standards and specifications

3.Switchgear operating conditions

4.Electrical parameters of switch cabinet

5.Switchgear resistance to inside fault arc

6.Switchgear dimensions and mass

7.Switchgear overview of switch cabinet structure

8.Switchgear basic structure/drawing

9.Switchgear enclosure and partition plate

10.Switchgear small compartments in the switch cabinet

11.Switchgear interlocking/protection against misoperation

12.Switchgear delivery conditions

13.Switchgear packaging

14.Switchgear transportation

15.Switchgear delivery and intermediate storage


Armored metal-enclosed switch cabinet to three-phase 50Hz,40.5kV,AC busbar segment power system.It has “fiveprevention” function.Vacuum/SF6 breaker,isolating handcart,voltage transformer handcart,etc.are configurable as separable parts of the switch cabinet.


2.Standards and specifications

·The switch cabinet conforms to IEC298,IEC62271,GB3906,DL404 and  other standards.


·The IP rating of the switch cabinet enclosure is IP4X.When the breaker compartment door is opened and the handcart is moved out,the IP rating is IP2X.


·The system installation and operation should conform to all the relevant IEC specifications and national or local safety guidelines.


3.Operating conditions


· Normal operating conditions

·Indoor ambient temperature:+25℃

·Maximum temperature:+40℃

·Average daily temperature:+35℃

·Minimum temperature:not higher than +35℃

·Indoor ambient humidity:-25℃

·Daily mean relative humidity:95%and below

·Monthly mean relative humidity:95%and below

·Altitude of installation site:90%and  below

·Seismic intensity:Not higher than VII

·A place free from fire and explosion risks,serious contamination and chemical corrosion.


· Special operating conditions

·For special working conditions,please consult the manufacturer.The manufacturer and the user shall agree on the special operating conditions


·The influence of air dielectric strength reduction on the insulation level has been considered when the altitude of the installation site exceeds 1,000m.


·When the ambient temperature exceeds the limit,compensation shall be made or carrying capacity shall be restricted in the design of busbars and branch busbars.Installation of ventilation devices in the switchgear facilitates its heat dissipation.


· Precautions

In case of operating in an environment with high humidity and fast and large temperature fluctuation,the switch cabinet may suffer a condensation risk.Therefore,the heater should be put into operation all day long when the switch cabinet is in either operating or standby state.However,the heater cannot be put into operation during operation at large current.


4.Electrical parameters of switch cabinet

Rated current of branch busbar

Rated voltag



Rated peak withstand current (peak value)

1min power frequency withstand voltage (effective value)


95 (phase-phase,phase-ground)

118 (isolating break)

Lightning impulse withstand voltage (peak value)


185 (phase-phase,phase-ground)

215 (isolating break)

Rated frequency



Rated current of main busbar



Rated current of main busbar



Rated short-time withstand current(effective value,4s)



Rated peak withstand current (peak value)



*Ventilation devices are required.


5.Resistance to inside fault arc

Since inside fault arc problems of the switchgear have already been considered in the design switch cabinet and the test has been carried out in strict accordance with GB3906 and IEC298,the safety of equipment and operators can be effectively ensured.

6.Dimensions and mass

·Height (a):2600(mm)  




7.Overview of switch cabinet structure

The switch cabinet consists of cabinet body and vacuum breaker handcart.This is the basic structure.

8.Basic structure (Fig.1)

Cross Section for Basic Structure for Incoming and Outgoing Cabinets

The incoming or outgoing cabinet is the basic cabinet design and there is also a derivative design such as busbar sectionalizing cabinet or metering cabinet, etc.In  addition,transformer  handcart,fuse   handcart,isolating  handcart,etc.are  configurable.The  switch  cabinet shall not be installed against a wall or face to face.Details on the structure and equipment installed inside the switch cabinet can be found in ordering documents.

9.Enclosure and partition plate

·The shells and partitions of the switch cabinets are of quality  steel plates.Such steel plates are of antioxidation and corrosion resistance and are superior to ordinary low-carbon steel plates in terms of rigidity and mechanicalstrength.Each of the three high-voltage compartments is equipped with a pressure relief plate  on the top.When the pressure increases in the high-voltage compartment in case of an internal fault,the high-pressure gas will push the pressure relief plate open and be relieved as the switch cabinet door is reliably sealed.The adjacent switch cabinets are separated by their own side plate and there is still an air buffer layer after connection of the cabinets,which can prevent puncture and melting of switch cabinet by fault electric arc.

·The low-voltage compartment A is arranged as an independent compartment from the high-voltage area.The plate separates the breaker compartment B form the cable compartment D.Thus,even when the hand trolley of the circuit breaker is displaced (where the valve  automatically  closes),the  plate  can  also  prevent  operators  from  touching  the  live  parts  in  the  busbar compartment C and cable compartment D.The horizontal plate can be removed by demounting the fixing bolts,which facilitates the installation of sealing terminals for cables.

10.Small compartments in the switch cabinet

Front View of Incoming or Outgoing Cabinet

·Breaker compartment (see Figs.1 and 2)

The circuit breaker handcart is installed in the breaker compartment B with rail,so it can be moved between the two different positions of Operation and Test/Isolation.When the handcart is moved from Operation to Test/Isolation,the valve automatically closes to cover the static contact,and opens vice versa.The handcart can be operated when the switch cabinet door is closed,because there is an observation window on the door.Through the window,the position of the handcart,the ON (circuit breaker closed)/OFF (circuit breaker opened)button on the handcart,closing/opening state indicator and energy storage/release state indicator can be observed.

·Circuit breaker handcart (see Fig.3)

Structure of circuit breakers

The handcart can be moved manually.The frame is pieced together with alloy steel plates,on which circuit breaker and other equipment are mounted.The contact arm with spring contact system is mounted on the post terminal of the circuit breaker and acts as electrical connection when the handcart is inserted into the position of “Operation”.

The signal,protection and control wires between the handcart and switch cabinet are connected by one control plug.When inserted into the switch cabinet,the handcart is fixed to the position of "Test/Isolation" and reliably connected to the grounding system of the switch cabinet.The position of the handcart can be observed through the observation window or the electrical position indicator of handcart on the panel of LV compartment.


In addition to the vacuum circuit breaker,the handcart is also equipped with isolation device,metering device and other devices.


The busbar is led from one switch cabinet to another and fixed by the branch busbar and wall bushing. Rectangular branch busbars are directly connected to the main busbars with bolts without the use of any connecting clamps.All the busbars and branch busbars are covered with heat-shrinkable bushing.The sleeve pipe plate and bushing are used to isolate and support the busbars between the cabinets.


·Cable compartment (Figure 1)


Behind the cable compartment,the current transformer and the earthing switch are installed.Meanwhile the lightning arrester can be provided for the cable compartment.The cable compartment with door opened has sufficient space to allow the construction personnel to enter the compartment to mount cables (at most 3 cables connected in parallel per phase).

The baseplate covering the cable inlet is made of nonmagnetic stainless steel plates with a split-type dismountable design to facilitate site construction.The variable-diameter seal ring openings for the primary and secondary cables to pass through the baseplate shall be matched with the laid cables to prevent the entry of small animals.


If the humidity of the cable trench is relatively high,it is recommended to seal the switch cabinet with fireproofing mud and epoxy resin.


·LV compartment (Figures1 and 2)

The secondary components of the switch cabinet shall be installed in the LV compartment and at the door.The trench for control cable shall be wide enough to lead in and out the cable between switch cabinets.The LVcompartment is provided with control wire holes on its side plate to control the power supply connection.

11.Interlocking/protection against misoperation

There are a series of interlocking devices which fundamentally prevent the occurrence of dangerous situations and misoperations likely to cause serious consequences,thus effectively ensuring the safety of operators and switch cabinet.Functions of the interlocking devices are as follows:


·When the breaker and earthing switch are at off position,the handcart can be moved to the operating position from the test /isolating position or to the test/isolating position from the operating position(mechanic interlocking).


·The breaker can be switched on only when the handcart is fully moved to the test or operating position.


·When the handcart is put at test or operating position without control voltage,the breaker cannot be switched on,but it can be switched off manually(electrical interlocking).


·When the handcart is put at operating position,the control cable plug will be locked and cannot be pulled out.


·The earthing switch can be switched on only when the handcart is put at the test or isolating position or moved away(mechanical interlocking).


·The handcart cannot be moved to the operating position from the test /isolating position when the earthing switch is switched on(mechanical interlocking).

Additional interlocking devices like latching electromagnet can be installed on the operating mechanism of handcart and /or earthing switch.But the user shall express such requirements at ordering.If a latching electromagnet is installed,the main shaft of the ground switch cannot be operated for closing /opening when the cable compartment is powered on.

12.Delivery conditions

In addition to checking based on the order,the assembled switch cabinet shall also be subject to delivery test in accordance with corresponding IEC 298 and GB3906 regulations,so as to verify correctness of the structure and functions.The busbar,fasteners and accessories are separately packed.



The switch cabinet shall be packaged according to actual situations,for instance,seaworthy packaging or being Bun packaged.For transportation by sea,the switch cabinet shall be sealed with plastic film and accompanied with desiccant to prevent damp even that it is placed in a container.



Generally,a single switch cabinet is a transportation unit.Each switch cabinet is installed with 4 lifting lugs.

Foundations of 1400mm 1680mm Wide Switch Cabinets

·In transporting,the switch cabinet shall be kept upright,and safety measures shall be taken to protect.

·Loaded with a crane.

Schematic Diagram of Lifting

·Loaded with a forklift.

Moving switch cabinet with Forklift

·The lifting rope shall have adequate loading capacity,and the opening width of a lifting hook shall be equal to or more than 30 mm.

·The angle between the rope connecting to the lifting hook and the horizontal line shall be kept over 60°.

·When the switch cabinet is lifted,the lifting lugs are allowed to be bent accordingly.

15.Delivery and intermediate storage

When the switch cabinet arrives at the site,the consignee has the responsibility (but not limited to)to perform the following work:

·Notify our site service engineers to participate in the unpacking acceptance inspection.


·Check whether  the delivered goods are complete and undamaged.Check if labels and certificate of conformity of the switch cabinet are correct and complete and if there is any specification.In case of any doubt,open the package and check it.Seal the switch cabinet again with desiccant put in during any intermediate storage of the switch cabinet.


·Record all shortages,defects and the damages related to transportation in detail,and timely inform relevant agencies.


·Note that the switch cabinet and installation materials shall be kept away from any hazard during intermediate storage.


Unpacking procedure:

Remove the top plates and then the side plates of the packing container.Finally remove the bolts connecting the  switch cabinet and the base plates.Lift the switch cabinet vertically at the four lifting lugs on the top from the base plate.Move away the base plate and lay rollers under the switch cabinet.Pry the rollers slowly with a stick to move the switch cabinet to the installation position or temporary storage position.Keep the switch cabinet from heavy impact or vibration during movement.


Simply packaged or unpackaged switch cabinet:

·Keep the warehouse dry and well-ventilated.

·The indoor temperature shall not be less than -25℃;

·Keep the warehouse free of any hazardous environmental influence.

·Place the switch cabinet vertically.

·Do not stack up switch cabinets.

·Do not remove or damage the package.

·Cover each switch cabinet with plastic film to prevent contamination.Keep the warehouse well-ventilated to prevent  corrosion.

·Check condensation regularly till installation.

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