24KV 250kva Compact Substation Configuration

24KV 250kva compact transformer substation

Applicable places for box type substations

1. Used as a street light box transformer: Both European style and American style box transformers have advantages over traditional civil engineering electrical rooms in small load power systems. The box type substation has a much lower cost compared to ordinary electrical rooms and a beautiful appearance. European style box transformers can also use landscape type shells, making it a beautiful scenery.

2. Electricity consumption in parks and residential areas: Box-type substations are often used for power supply in parks and residential areas. Parks and residential areas often pursue aesthetics and occupy space. Box-type substations effectively solve these two problems, with beautiful appearance and small footprint.

3. Industrial and mining electricity: Due to the complex terrain and high time cost, areas such as factories and mines have high requirements for power supply equipment. The box type substation is easy to install, with a small amount of on-site construction, and a protection level of IP33, which can greatly reduce the construction amount and duration. It is installed in areas with complex terrain.

4. Temporary electricity usage: The construction unit often changes the location of electricity usage with the relocation of the construction site, so a set of movable distribution equipment is needed. The box type substation has good mobility and sufficient load capacity, which can fully meet the temporary electricity demand of the construction site.

1、 The Function and Characteristics of Box Substation

Box type substation refers to an outdoor distribution device that installs high and low voltage switchgear and transformers together in a closed box. The main function is to provide the required electrical energy for high-voltage or low-voltage users. It has the following characteristics:

1. Small footprint. Installing a box type substation can save more than two-thirds of the land area compared to building a substation of the same size.

2. Flexible combination methods. The structure of box type substations is relatively compact, with each box forming an independent system, which makes the combination method flexible and variable. The user can freely combine some modes according to the actual situation to meet the needs of different places.

3. Beautiful appearance, easy to coordinate with the environment. The box casing can be selected in different colors according to different installation locations, making it easy to coordinate with the surrounding environment. It is particularly suitable for densely populated areas such as urban residential communities, stations, ports, airports, parks, green belts, etc. It can be used as a fixed substation or a mobile substation.

4. Low investment and short construction cycle. Box type substations reduce investment by 40% to 50% compared to conventional substations of the same scale, and the construction and installation cycle can be significantly shortened. At the same time, the daily maintenance workload of the box type substation is also relatively small.

2、 Types of box type substations

1. Assembly type

Install the complete set of high and low voltage devices and transformers into metal boxes, and leave operating corridors in the high and low voltage distribution devices. This type of box transformer has a large volume and is rarely used nowadays.

2. Combination device type

Instead of using the existing complete set of devices, the high and low voltage control and protection electrical equipment are directly packed into the box, forming a whole. The design is considered maintenance free, with no operating corridors and a small box, also known as European style box transformers or ordinary box transformers.

3. One body type

Simplify the high-voltage control and protection devices, and put the high-voltage and low-voltage distribution devices and the main body of the transformer into the transformer oil tank together to form a whole, smaller, close to the oil immersed transformer of the same capacity, which is 1/3 of the European box type transformer. Also known as American style box transformer or compact box transformer.

3、 Structure of Box Substation

1. Structure of European style box transformer

(1) In China, European style box type substations are commonly used, with three parts each consisting of one room, forming a "mu" or "pin" structure. Commonly used models include ZBW and XWB. The cross-sectional and wiring diagrams are shown in Figure GYPD00102003-1. The high voltage chamber of the European style box transformer is a ring network, double line or terminal unit load switch, with a small volume and compatibility with the ring network cabinet. Adopting a safe and reliable compact design, with comprehensive anti misoperation interlocking function, high reliability, and convenient operation and maintenance. High voltage equipment generally adopts a combination of load switch and fuse. The fuse is equipped with an impactor. After the fuse is blown, the striker will push the release mechanism, and the load switch three-phase will jump open at the same time to avoid phase loss operation. At the same time, if an electric operating mechanism is used, distribution automation function can be implemented. The 10kV cable outlet of the ring network structure is equipped with a ground fault indicator and zero sequence sensor. Transformers can be oil immersed or dry type, with D, yn11 wiring. Considering unfavorable heat dissipation, natural ventilation or top forced ventilation can be used. The low-voltage room is equipped with metering and reactive power compensation, and the secondary circuit and number of outgoing lines can be designed according to user needs to meet different needs. The outer shell is made of steel plate or alloy plate, with a double-layer top cover and good insulation. The appearance and color can be coordinated with the environment. The high-voltage chamber, transformer chamber, and low-voltage chamber are separated into independent compartments by partitions. For monitoring and maintenance, lighting devices are installed in each compartment, and the lighting switch is controlled by the door.

2. Structure of American style box transformer

(1) The American style box transformer shares a high voltage switch and transformer in the same oil tank. Common American style box transformer models include ZB1336, GE, and COOPER.

The American style box transformer adopts a fully sealed and fully insulated structure, with high safety. It can be used for ring networks and terminals, and the high voltage is controlled by a T-type or V-type three-phase linkage four position oil load switch

(2) The transformer adopts a backup fuse connected in series with a plug-in fuse to provide protection. The backup fuse is installed inside the box and only acts when there is an internal phase fault in the box transformer, used to protect the high-voltage line. The plug-in fuse fuses when there is a short circuit or overload on the secondary side.

High voltage cables are connected to sleeves with good insulation performance, which are connected to elbow type cable plugs to seal the live parts. The elbow type cable plug is a fully shielded insulated plug that can be fully loaded and unplugged, equivalent to a load switch. However, if it is connected to a short circuit point, the elbow type plug and sleeve should be replaced.

4、 Operation of Box Substation

1. The box type substation should be placed at a relatively high place, not in low-lying areas, to prevent rainwater from entering the box and affecting equipment operation. When pouring concrete platforms, gaps should be left on the high and low voltage sides to facilitate the laying of cables in and out. When excavating the foundation, if encountering the ground formed by the accumulation of garbage or corrosive soil, it must be excavated to solid soil, then backfilled with good soil quality and compacted, and then filled with three layers of soil or gravel to ensure the stability of the foundation.

2. The grounding and neutral connection of the box type substation share a common grounding network. The grounding grid generally adopts the method of driving grounding piles at the four corners of the foundation, and then connecting them as a whole. There must be two reliable connections between the box type substation and the grounding grid. After operation, the grounding connection should be checked regularly to ensure it is not loose or corroded. Regularly measure the grounding resistance, not exceeding 4 Ω.

3. The box type substation mainly adopts natural air circulation cooling. Therefore, debris should not be piled up around it, especially the transformer room door. Louver ventilation holes should also be regularly cleaned to ensure that the equipment does not exceed the maximum allowable temperature.

After the low-voltage circuit breaker trips, the cause should be identified before power can be transmitted to prevent the accident from expanding.

5. The high-voltage chamber of the box type substation should be equipped with zinc oxide lightning arresters, and the installation method should be convenient for testing and replacement.

6. Equipment such as ring network switches, transformers, lightning arresters, etc. in the high-voltage room should be regularly inspected and maintained, defects should be discovered and dealt with in a timely manner, and insulation preventive tests should be conducted regularly. If it is discontinued for more than 3 months and is put into operation again, a full project preventive test should be conducted.

7. To replace a high-voltage fuse without breaking capacity, the transformer must be powered off, and the mechanical interlock must be properly released during operation, and an insulated operating rod must be used.

8. All incoming and outgoing cable holes of the box type substation should be sealed to prevent small animals from entering and causing accidents.

9. Must have a warning sign of "high voltage danger" and a nameplate number for electrical equipment

Configuration of high-voltage side of box transformer

(1) The box transformer is divided into terminal type and ring network type based on the primary wiring method on the high-voltage side. The terminal type box transformer does not need to consider additional wiring: if the high-voltage side is one in multiple out or multiple in one out (mostly one in two out or three out, or two in one out or two out), it can be considered as a ring network type box transformer.

(2) European style box transformers have circuit breaker configurations on the high-voltage side, as well as load switch fuse combination protection. Considering the cost of box transformers, for box transformers with a capacity not exceeding 800 kV · A and low requirements for high-voltage side protection configuration, the latter is often used.

(3) The high-voltage load switches configured in European style box transformers are mostly FLN-12 sulfur hexafluoride load switches.

(4) The rated current of the high-voltage fuse melt for protection is selected according to the following formula:

Irr=KIgmax

In the formula, Irr - rated current of the melt, A; K - coefficient, generally taken as 1.3:

Igmax - Rated current on the high-voltage side of the transformer.

(5) Considering the safety of operation and maintenance, the high-voltage side configuration of European style box transformers should meet the following requirements.

① When the load switch is disconnected, there is a grounding device to ensure maintenance safety.

② The load switch and isolation switch ensure mutual locking to ensure safe operation.

(6) Due to the combination of high-voltage load switch and fuse, the American style box transformer is assembled in the same oil immersed box, including position load switch, backup fuse, plug-in fuse, and transformer. The ring network type is achieved by converting the internal connection terminals of the position load switch.

 

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TECHNICAL REQUIREMENTS AND CHARACTERISTICS OF EQUIPMENT
Re:82 sets compact substation
Item- No.	Schedule of Technical Data	Unit	Required (at 3000 m	Offered Data
	System Data Requirements
1.05.10	Stranded copper conductor for earthing
	Manufacturer	-
	Material	-	copper
	Cross-section	mm2	>50
	Length	m	>40
1.05.11	Earthing rods
	Manufacturer	-
	Type	-
	Materia!	-
	Length	m
	Sections per rod	pcs
1.6	Compact Substations (Option 1)
	Manufacturer	-		fengyuan
	Type	-		OutDoor
	Overall protection class for complete substation	-	IP 44	IP 44
	Material of enclosure	-		GI
	Overall dimensions (W x L x H)
	for S/S with 1x50 kVA transformer	mm/mm/mm		3000x1850x2150
	■ for S/S with 1x100 kVA transformer	mm/mm/mm		3000x1850x2150
	for S/S with 1x160 kVA transformer	mm/mm/mm		3000x1850x2150
	• for S/S with 1x250 kVA transformer	mm/mm/mm		3000x1850x2150
	Overall weight
	■ for S/S with 1x50 kVA transformer	kg		1000kg.
	■ for S/S with 1x100 kVA transformer	kg		1000kg.
	■ for S/S with 1x160 kVA transformer	kg		1000kg.
	■ for S/S with 1x250 kVA transformer	kg		1000kg.
1.6.1	20 kV Switchgear equipment
	Manufacturer	-		Chnt / Equivalent
	Type	-		Indoor RMU
	Rated voltage	kV	20	20
	Maximum operating voltage	kV	24	24
	Rated current	A	400	400
	Rated short time current	kA	16	16
	Rated power frequency withstand voltage	kV	50	50
	Rated impulse withstand voltage (peak value)	k-^peak	125	125
	Insulating medium		SF6/air	SF6/air
	Protection class		lP4x	lP4x

 

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