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

 

Featuring compact design and reliable performance, this 50 kVA pad-mounted transformer uses copper or aluminum windings and supports primary voltages of 10–35 kV at 50/60 Hz, providing efficient operation for residential or small-scale urban distribution networks.

 

 

 

 

The pad - mounted transformer serves as an integrated prefabricated product that combines distribution network power supply unit cables, high - voltage control, protection, substation, and power distribution equipment. It is widely applied in urban and rural distribution networks. The transformer and high - low voltage equipment are closely connected into one unit. Three sides of the transformer are exposed to the air, ensuring good heat dissipation conditions. Moreover, the transformer can be separated from the high - low voltage equipment housing, facilitating maintenance. Power distribution switchgear is installed on the high and low voltage sides.

 

 

 

 

• Taking the ZBW series as an example, the model is represented as ZBW - 12/0.4 - □ - □ - □.
• The first part "ZBW" indicates the prefabricated substation.
• "12/0.4" represents the rated voltage levels, with 12kV for the high - voltage side and 0.4kV for the low - voltage side.
• The subsequent boxes respectively denote the high - voltage measurement of rated voltage (KV), low - voltage measurement of rated voltage (KV), and rated capacity of the transformer (KVA).

 

 

 

 

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.
 

 

 

 

• Compact structure, small size, easy installation.
• Applicable to ring network and terminal power supply, ensuring personal safety.
• Low loss, low noise, excellent performance, and anti-theft box structure.
• Low temperature rise and strong overload capacity.

 

 

 

 

• Transformer and Chambers: The pad-mounted transformer uses the 813 series oil-immersed transformer with a chip-type oil tank (no oil cushion, fully enclosed). High/low-pressure bushings, tap changers, oil level indicators, pressure release valves, oil release valves, etc., are mounted on the high-pressure chamber end plate for easy observation and operation. Its high/low-pressure chambers are separated by steel plates (relatively independent) and integrated into a complete box.
• Components: It is equipped with plug - in fuses, pressure gauges, pressure relief valves, oil level gauges, oil thermometers, load switches, high - voltage cable joints, off - circuit tap changers, ground points, drain valves, and low - voltage switch cabinets, etc.
• Load Switch: It is an oil - immersed, three - phase linkage switch with a spring operating mechanism. It can be operated with load, and its closing speed has nothing to do with the operating force. There are types such as two - station, four - station T type, and four - T position V type to choose from.
   

 

 

 

 

● Foundation Bearing Capacity and Protection
The foundation bearing capacity shall be not less than 100 kPa.

-If the foundation is located in highlands, external drainage systems shall be provided around it.

-The foundation shall be built with red brick cement mortar, and both inner and outer walls shall be plastered with 20mm-thick 1:2 cement mortar mixed with 3% waterproofing agent to enhance waterproofing.

-The concrete foundation surface shall be flat, and after installation of the prefabricated substation, the surrounding foundation shall be sealed with cement.

 

● Structure and Embedded Parts

-The bottom of the cable chamber shall be slightly inclined toward the water collection pipe to prevent water accumulation.

-A diamond-shaped expanded steel mesh (150×300 frame, 10×20 mesh size) shall be welded inside the louver frame, with reinforcement ribs embedded into the wall for enhanced strength.

-Grounding bars and cable fixing brackets shall be pre-embedded, and their shapes and positions shall be determined according to actual site conditions.

--The positions of incoming and outgoing cable holes shall also be determined as required on-site.

 

● Operation and Space

After installation of the prefabricated transformer substation, an operation clearance of not less than 1.5m shall be reserved in front of the switch to ensure safe operation and maintenance.

 

● Grounding System

-The grounding trunk shall be led out from the cable trench, and may be arranged around the ring main unit or extended to the grounding electrode from one side.

-The grounding grid shall be constructed with Φ12mm galvanized round steel or 30×4mm galvanized flat steel.

-The grounding resistance shall be ≤4Ω, in compliance with the requirements of the power authority.

 

● Construction Standards and Flexibility

-Foundation construction shall comply with JGJ/T16-92 "Code for Electrical Design of Civil Buildings".

-The dimensions shown in the drawings are recommended values. Cable wells can be arranged in three or four directions according to site conditions to meet different incoming line requirements.

 

 

 

 

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.