250 KVA Pad Mount Three-Phase Oil-Immersed Distribution Transformer

 

Built for compact urban and light industrial networks, this 250 kVA pad-mounted transformer utilizes high-quality copper or aluminum windings and oil-immersed construction. Its three-phase design ensures stable voltage delivery, and the layout allows straightforward inspection and maintenance.

 

 

 

 

The ZBW series prefabricated box-type substation (commonly referred to as the American-style box-type transformer) features a "product"-shaped structure. Its transformer and high/low-voltage equipment are closely integrated into a single unit. Among its design highlights, three sides of the transformer are exposed to the air-ensuring excellent heat dissipation-and the transformer can be separated from the enclosures of the high and low-voltage equipment, facilitating easy maintenance.

The 813 series oil-immersed transformer is equipped with a chip-type oil tank, requires no oil cushion, and adopts a fully enclosed design. Components such as high-voltage and low-voltage bushings, tap changers, oil level indicators, pressure relief valves, and oil drain valves are all installed on the end plate of the high-pressure chamber. This layout ensures reasonable component positioning, making it convenient for observation and operation.

The high-pressure chamber and low-pressure chamber are separated by steel plates. While the high-pressure chamber, low-pressure chamber, and transformer are relatively independent, they collectively form a complete, integrated box. This design results in a compact structure, small volume, and lightweight build. Additionally, power distribution switchgear is installed on both the high-voltage and low-voltage sides of the substation.

 

 

 

 

The pad-mounted transformer must operate under specific environmental conditions to ensure stable performance and safe operation, with requirements integrated from both data sources as follows:

1. Cooling Condition
Adopts air self-cooling mode, relying on natural air circulation to dissipate heat generated during transformer operation, which is suitable for its structural design and common application scenarios.

 

2. Wind speed:
Equivalent to 34m/s (not more than 700 Pa);

 

3. Temperature Requirement
The outdoor ambient temperature shall not be higher than 40℃ and not lower than -45℃.
The monthly average temperature shall not exceed 30℃, and the annual average temperature shall not exceed 20℃. This limits the long-term temperature load on the transformer to avoid performance degradation caused by extreme temperature accumulation.

 

4. Altitude Requirement
The installation altitude shall not exceed 1000m.

 

5. Humidity Requirement
At a temperature of 25℃, the maximum relative humidity of the air shall not exceed 95%, and the daily average relative humidity shall not exceed 90%.

 

6. Vibration and Acceleration Requirement
The horizontal acceleration of the installation site shall not exceed 0.3g, and the vertical acceleration shall not exceed 0.15g).

 

7. Installation Platform Requirement
The installation site shall be clean, free from explosive or corrosive gases, conductive dust, strong vibration, and impact. The slope shall not exceed 3°, and the transformer must be placed on a flat, solid cement platform to ensure stability.

 

8. For product orders beyond the conditions specified above, please negotiate with our company.

 

 

 

 

• Small size, compact structure, and easy installation: It can be used for both ring network and terminal applications, with reliable personal safety protection.
• Low loss, low noise, and superior performance
• Anti-theft cabinet design: The cabinet adopts an anti-theft structure.
• Low temperature rise and strong overload capacity

 

 

 

 

Compact structure and small size: It is only about 1/3 to 1/5 the size of domestic European-style boxes with the same capacity, greatly reducing the floor space.
Fully sealed and fully insulated structure: This eliminates the need for insulation distances and provides reliable personal safety protection.
Flexible high-voltage connection: It can be used for both ring network and terminal connections, offering flexible power supply modes and high reliability.

Excellent transformer performance: The transformer features low loss, low noise, low temperature rise, strong overload capacity, and excellent short-circuit impact resistance.
Adaptable to low-voltage needs: It meets the requirements of various low-voltage power supply scenarios, and can either be selected based on existing plans or customized according to specific demands.

Versatile cable connections & supporting devices: Two types of cable connections are available-cable head plugs and 600A/200A elbow-type fixed cable joints. It can also be equipped with fully insulated zinc oxide arrester devices. Additionally, the 200A cable head supports live hot-swapping and functions as an isolating switch.
 

 

 

 

This product complies with the following standards:

• GB/T 17467-1998 High-Voltage/Low-Voltage Pre-Installed Substations
• DL/T 537-1993 Technical Conditions for Ordering 6-35kV Box-Type Substations
   

Main Technical Parameters

Serial number	Item	Units	Technical parameter
1	Rated voltage	KV	10/0.4 (High/low voltage)
2	Maximum operating voltage	KV	12 (High voltage side)
3	Rated frequency	Hz	50
4	Rated capacity	KVA	150-1600
5	1min power frequency withstand voltage	KV	35
6	Lightning impulse voltage	KV	75
7	Cooling mode	-	Oil-immersed self-cooling
8	High voltage backup fuse breaking current	KA	50
9	Breaking current of plug-in fuse	KA	2.5
10	Ambient temperature	℃	-35 ~ +40
11	Coil allowable temperature rise	K	65
12	No-load voltage regulation	-	±5% or ±2×2.5%
13	Noise level	dB	50
14	Protection class	-	IP43

 

 

 

A new S9 series transformer body is selected, featuring low loss, good overload capacity, and strong short-circuit resistance; all fasteners are protected. Alternatively, the S11 series ring jointless core transformer (with better performance) can also be chosen.
Transformer Selected new S9 series transformer body, low loss, good overload capacity, strong short-circuit resistance, all fasteners are protected. The S11 series ring jointless core transformer with better performance can also be selected.

 

Capacity (KVA)	Voltage KV - High tension	Voltage KV - Low pressure	Join group label	No-load current % - S9	No-load current % - S10	No-load current % - S11	No load loss W - S9	No load loss W - S10	No load loss W - S11	Impedance voltage %	Load loss
160	10±5% or 2×2.5%	0.4	Dyn11/Y,yno	1.4	1.4	0.2	400	320	255	4	2200
200	10±5% or 2×2.5%	0.4	Dyn11/Y,yno	1.3	1.3	0.2	480	380	305	4	2600
250	10±5% or 2×2.5%	0.4	Dyn11/Y,yno	1.2	1.2	0.2	560	450	360	4	3050
315	10±5% or 2×2.5%	0.4	Dyn11/Y,yno	1.1	1.1	0.2	670	530	425	4	3650
400	10±5% or 2×2.5%	0.4	Dyn11/Y,yno	1	1	0.15	800	650	505	4	4300
500	10±5% or 2×2.5%	0.4	Dyn11/Y,yno	1	1	0.15	960	750	605	4	5100
630	10±5% or 2×2.5%	0.4	Dyn11/Y,yno	0.9	0.9	0.15	1200	910	755	4	6200
800	10±5% or 2×2.5%	0.4	Dyn11/Y,yno	0.8	0.8	0.15	1400	1080	980	4.5	7500
1000	10±5% or 2×2.5%	0.4	Dyn11/Y,yno	0.7	0.7	-	1700	1260	-	4.5	10300
1250	10±5% or 2×2.5%	0.4	Dyn11/Y,yno	0.6	0.6	-	1950	-	-	4.5	12000

 

 

 

 

On the high-voltage side of the American-style box-type substation, full-range protection is provided by a backup protection fuse and a plug-in fuse connected in series. This protection principle is simple, cost-effective, and reliable.
The backup protection fuse is an oil-immersed high-voltage current-limiting fuse with a high breaking capacity; it only operates in the event of an internal fault in the transformer. The plug-in fuse is equipped with a double-sensitive fuse element, which provides dual protection against overcurrent and overtemperature. Once the double-sensitive fuse element is blown, it can be easily replaced on-site.

 

 

 

 

1. Basic load-bearing requirement: The foundation must withstand a pressure of over 100 kPa.
2. Foundation for elevated areas: Ensure proper drainage around the foundation. The foundation should be constructed with red bricks and cement mortar; the external walls shall be plastered with 1:2 cement mortar (20 mm thick), with 3% waterproofing agent added.
3. Cable chamber drainage: The bottom surface of the cable chamber shall be slightly inclined toward the water collection pipe to facilitate drainage.
4. Steel mesh and rib installation: Use a 150×300 steel mesh with (10×20) diamond-shaped openings; weld ribs to the inner wall of the outer frame.
5. Compliance with standards: Foundation construction shall comply with the relevant provisions of JGJ16-83 Code for Electrical Design of Buildings.
6. Grounding system requirements: Conduct routine inspections on the main grounding steel and its connecting ends. The grounding wire led from the cable trench can be routed along the perimeter of the ring network cabinet or extended from one side for grounding. The grounding resistance shall be ≤ 4 ohms.
7. Dimension reference: Follow the dimensions specified in the construction drawing (as recommended).
8. Cable well flexibility: For user convenience, cable wells can be installed in 3 to 4 directions on-site based on actual conditions.
 

 

 

 

S/N	Name	Unit	Technical Parameter
1	Rated Voltage	KV	10/0.4
2	High-voltage Side Rated Voltage	KV	10
3	Low-voltage Side Rated Voltage	KV	0.4
4	Maximum operating voltage (High voltage side)	KV	12
5	Rated Frequency	Hz	50
6	Rated Capacity	KVA	150-1600
7	High-voltage Switch Heat Stable Capacity	KA	20/26
8	Low-voltage Main Circuit Breaker Rated Short-circuit Breaking Capacity	KA	35
9	Low-voltage Distribution Circuit Breaker Rated Short-circuit Breaking Capacity	KA	35
10	High-voltage Load Switch Transfer Current	A	>1500
11	1 min Power Frequency Withstand Voltage	KV	35
12	Lightning Impulse Voltage	KV	75
13	Cooling Mode	-	Oil immersed self-cooling
14	High-voltage Backup Fuse Breaking Current	KA	50
15	Breaking Current of Plug-in Fuse	KA	2.5
16	Ambient Temperature	℃	-35 ~ +40
17	Coil Allowable Temperature Rise	K	65
18	No-load Voltage Regulation	%	±5% or ±2 × 2.5%
19	Noise Level	dB	<50
20	Protection Grade of Box Shell	-	Not less than IP3X

 

Insulation Level

Rated voltage(KV)	10			0.4
	Transformer	Switch to ground and phase to phase	Between disconnectors
Power frequency withstand voltage (KV)	35	42	48	2.5
Peak value of impulse withstand voltage(KV)	75	75	85	–

 

 

 

 

Selected new S9 series transformer body, low loss, good overload capacity, strong short-circuit resistance, all fasteners are protected. The S11 series ring jointless core transformer with better performance can also be selected.

 

Capacity KVA	Voltage KV		Join group label	No-load current %			No load loss W			Impedance voltage %	Load loss
	High tension	Low pressure		S9	S10	S11	S9	S10	S11
160	10±5% or 2×2.5%	0.4	Dyn11 Yno	1.4	1.4	0.2	400	320	255	4.0	2200
200				1.3	1.3	0.2	480	380	305		2600
250				1.2	1.2	0.2	560	450	360		3050
315				1.1	1.1	0.2	670	530	425		3650
400				1.0	1.0	0.15	800	650	505		4300
500				1.0	1.0	0.15	960	750	605		5100
630				0.9	0.9	0.15	1200	910	755		6200
800				0.8	0.8	0.15	1400	1080	980		7500
1000				0.7	0.7	-	1700	1260	-	4.5	10300
1250				0.6	0.6	-	1950	-	-		12000

 

Item Name		Units	315A	630A
Rated voltage		KV	12	12
Maximum current		A	315	630
Rated frequency		Hz	50	50
Rated short-circuit closing current		kA	31.5	50
Rated short-time withstand current		kA	12.5	50
Rated short endurance time		S	2	2
Mechanical life		Second-rate	2000	2000
Lightning impulse test	Phase to phase	KV	75	75
	Isolation fracture		85	85
1min power frequency withstand voltage	Phase to phase	KA	42	42
	Isolation fracture		48	48
Rated peak withstand current		KV	31.5	50

 

 

Capacity	A	B	C	H	Weight KG
200kVA and below	1830	1420	820	1850	＜ 2800
250-400kVA	1830	1450	850	1980	3000-3300
500-630kVA	1830	1480	880	2070	3600-3950
800kVA	2200	1700	950	2170	4500

Note:The above is the standard size for reference.

 

Capacity	A	B	C	H	Weight KG
315kVA	2560	1600	600	1000	3050
400kVA	2560	1600	600	1000	3270
500kVA	2560	1600	600	1000	3400
630kVA	2560	1600	600	1000	3900
800kVA	2760	1600	800	1000	4200
1000kVA	2760	1950	800	1000	4800
1250kVA	2910	1950	800	1000	5400
1600kVA	2200	1700	950	2170	4500

Note:The above is the standard size for reference.