What You Should Know About Compact Substation

Publish time:

2020-12-28 15:51:00

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Compact substation, also known as prefabricated substation, is a kind of indoor and outdoor compact distribution equipment. It combines the high voltage switch equipment, distribution transformers and low voltage power distribution equipment together in a certain wiring schemes, installed in a steel structure which is moisture, rust, dust, rat, fire prevention, guard against theft, thermal insulation, fully enclosed and movable. It is suitable for mines, factories, oil and gas fields and wind power stations. It replaces the original civil distribution house and power station and becomes a new complete set of transformer and distribution equipment.

 

Structure of Compact Substation

The compact substation is mainly divided into three parts: high voltage switchgear, transformer and low voltage switchgear.

According to the needs of the system, HV switchgear can choose sulfur hexafluoride (SF6) or vacuum circuit breaker, ring network switch, load break switch and fuse.The high voltage side can also be installed with metering devices. The low voltage side is generally installed with main switch and branch feeder switch, but some only install feeder switch. Feed directly to the low voltage end user. In addition, compensation capacitors and metering devices also can be installed. Distribution transformers generally choose oil-immersed or dry type transformers. 

European type compact substation: The high voltage chamber is generally composed of high voltage load break switch, high voltage fuse and lightning arrester, which can be shut down and protected by overload and short circuit. The low-voltage chamber is composed of low-voltage air switch, current transformer, ammeter, voltmeter, etc. Transformers are generally S9 or dry type.

American type box-type transformer substation: Its structure is divided into front and back parts. The front part is the connection cabinet. The connection cabinet includes HV and LV terminals, HV load switch, plug-in fuse, HV tap switch operating handle, oil level gauge, oil temperature gauge, etc. The rear part is the oil tank body and heat sink. Transformer windings, iron cores, high-voltage load switches and plug-in fuses are all in the oil tank body. The box is fully sealed. The integrated box has recently been developed by domestic manufacturers and is not widely used. It is of double-layer structure with high and low voltage Chambers placed above the transformer room.

The European, American and integrated compact substation have their own advantages and disadvantages. The European type have a large volume, and the high and low voltage switches and transformers are located in a large shell, so the heat dissipation conditions are poor and the mechanical exhaust device needs to be installed. Due to the direct external heat dissipation of the transformer cooling plates, the American box transformer has relatively good heat dissipation conditions, but its shape is worse than that of The European type, and its appearance is difficult to cooperate with the green environment such as residential quarters. The integrated type occupies less space, and its advantages and disadvantages are similar to those of American type. In addition, American and integrated compact substation can only be manufactured in China with a capacity of less than 630kVA, while European type can be manufactured with a capacity of up to 1250kVA.

 

Operation and maintenance of compact substation

Ⅰ. Basic requirements for compact substation operation

1. The floor of compact substation equipment should be placed in a higher place, not in a low-lying place, so as not to affect the operation of rainwater into the box. Empty gear should be left when pouring concrete platform. It is convenient for cable in and out laying.

2. There must be two reliable connections between the box body and the grounding net. The grounding net and the grounding net can be connected together. The grounding net is generally grounded at the four corners of the foundation and then connected as a whole.

3. There should be no illegal piling around the box equipment to ensure the ventilation and inspection of the electrical equipment. The box should be cooled mainly by natural air circulation and the transformer room door should not be blocked.

4. The equipments in the high voltage distribution device should be inspected and maintained regularly which includes the ring main switch, transformer and lightning arrester. The defect should be repaired in time, and the insulation preventive test face should be carried out regularly. The mechanical linkage should be properly broken and operated with insulating rods.

Ⅱ. Inspection and maintenance of the transformer shall make periodic inspection according to the inspection and maintenance cycle (not less than once a month), test the temperature at the connection of the cable terminal head, check the operation condition of the equipment, and test it if necessary.

 

General inspection items are as follows:

1. Making sure the foundation is firm, the holes are blocked, and the cabinet has no moisture.

2. Whether the grounding device is complete and connected well. Whether the grounding resistance meets the requirements.

3. Is there any change of the outdoor environment. Does it affect the safety of traffic and pedestrians?

4. Check all feeder loads. Whether the three-phase load is balanced or over load phenomenon, whether the switch position, instrument indication is correct, whether the control device is working normally.

5. Dust removal inside the transformer room should be done once every other year. The surface of cabinet body of high pressure room and low pressure room and the surface of gas box can be wiped with wet cloth. In the transformer room, air blowing or vacuum cleaning is used for dust removal of transformers.

6. Daily maintenance and overhaul of the fan to check the operation of the fan. If the fan is not in operation, use the temperature and humidity controller, set it below the existing temperature, and start the fan inspection.

7. Maintenance and repair of high voltage switch and low voltage switch operating mechanism

(1) Check the barometer pointer. Is it in the green area? If it is in the red area, open and close the operation. Notify the manufacturer to deal with it immediately.

(2) For the lubrication of mechanical parts, separate and combine operation tests can be carried out after the completion of lubrication with universal lithium base grease (butter).

(3) Routine tests of cables and lightning arresters shall be conducted according to the requirements of routine tests. Conduct insulation test and leakage current test for cable and lightning arrester.

8. Routine test of temperature and humidity controller; Routine test of smoke alarm devices; Fastening and inspection of terminal bars: fastening and inspection of standard parts.

9. Terminal strip maintenance, terminal row may become loose due to heat expansion and cold contraction, annual inspection should be conducted to re-tighten all terminals in the terminal room. Note: Before refastening, please make sure that both the primary ac circuit and the secondary control circuit are powered off to avoid electric shock!

10. Notes for compact substation maintenance

(1) The door of the box is equipped with a windproof mechanism, which is to ensure that it is kept in a fully open state. When closing the door of the box, the root of the windproof mechanism must be lifted upward, and then the door cannot be yanked, so as to prevent the deformation of the mechanism or door and affect its normal use.

(2) After the local manual operation of the high-voltage load switch is completed, the load break switch operating handle should be placed back on the handle bracket inside the outer door. Lest it be lost.

(3) If the spare circuit of HV ring main unit is not connected with cables temporarily, the spare circuit should be closed before sending power, or the cable seat should be blocked with matching insulation cap to avoid accidents!

(4) The dustproof cap equipped with the ring main unit can not replace the insulation cap.

(5) It is not allowed to use any short-circuit plug to insert the test hole during operation. Otherwise, the voltage sensor will be damaged.

(6) The low-voltage isolation switch can only be operated in the unlocked position. Don't force and drag!

 

Correct operation of compact substation

1. Closing operation

Close the door - Open earth switch - Close the load break switch

2. Opening operation

Open the load break switch - Close earth switch - Open the door

 

Operational Considerations

(1) When performing the opening and closing operation of the load break switch, the switch must be pushed to the final position of opening and closing. Do not loosen or pull out the operating handle before the switch completes the operation, otherwise the spring rebound will hurt the operator.

(2) During the load break switch opening and closing operation, the operating handle should be turned out to prevent the operator from being hurt during operation

(3) Before the opening and closing operation of the load break switch, the upper left electric manual switching knob of the corresponding unit panel must be pulled out and fixed to the manual position by rotating 90° before the manual operation of the load break switch can be carried out; otherwise, the mechanism may be damaged.

 

Troubleshooting method

Ⅰ. The frame breaker cannot close

1. Failure of control loop.

2. The red button on the panel does not reset after the smart trip.

3. Energy storage mechanism has no energy storage

 

Elimination methods:

1. Check open points with a multimeter.

2. Find out the cause of tripping, and press the reset button after troubleshooting.

3. Manual or electric energy storage.

 

Ⅱ. Plastic case circuit breaker cannot close

1. There is no reset after the mechanism trip.

2. Circuit breaker with undervoltage coil and no power supply at inlet end.

Elimination methods:

1. Find out the cause of trip and reset after troubleshooting.

2. Make the incoming wire live, reset the handle and then close the switch.

 

Ⅲ. the circuit breaker will jump when it closes

1. Short circuit in the output circuit

Elimination methods:

1. Do not close the switch repeatedly. Fault must be identified and removed before closing the switch.

 

Ⅳ. The capacitor tank cannot be automatically compensated

1. The power supply in the control loop disappears.

2. The current signal line is not connected correctly.

Elimination methods:

1. Check the control circuit and restore the power.

 

How to construct the compact substation?

 

The construction of the grounding device

1. The ground network around the compact substation is connected with the ground network of surrounding buildings.

2. The embedding depth and welding requirements of grounding devices shall meet the design requirements and relevant specifications.

3. After the grounding device is installed, the grounding resistance shall not be tested until the ground humidity reaches the specification in a sunny day. If there is a grounding device whose grounding resistance value does not meet the requirements, the grounding electrode and the grounding bus shall be added as specified until the grounding resistance value meets the design requirements.

4. The connection between grounding device and equipment should be reliable and beautiful.

 

Installation and construction of compact substation

1. Approval application: provide the compact transformer manufacturer with the requirements of the compact transformer design drawing and the use requirements, order the corresponding materials and equipment, provide the equipment model to the power supply department before the transformer is ordered, and report for approval.

2. Wiring: After field investigation, determine the reasonable inlet point of 10kV power supply inlet line, and work out the corresponding electric receiving construction plan

3. Embedment: Carry out the foundation construction of compact substation and embed the corresponding components and cable protection steel tubes.

4. Installation: After the foundation reaches more than 70% of the designed strength, the compact transformer shall be inspected before it arrives at the site. The installation of the equipment can only be carried out after the accessories are complete, the equipment is in good condition, and there is no rust or mechanical damage.In this process, attention should still be paid to the maintenance of the foundation.

5. Inspection: After the completion of the construction, the construction unit shall report to the qualified testing department for testing.

 

Rockwill Compact Substation Display:

https://youtu.be/Q818eL6jxbI

https://youtu.be/gdcW3RYNXMs