HUARUI 
Single Phase Pole Mounted Transformer
A single-phase pole-mounted transformer, also known as an overhead distribution transformer, is an oil-immersed distribution transformer specifically designed for outdoor overhead power line installation. The equipment has a compact cylindrical or elliptical tank structure and is suspended from a utility pole using a dedicated bracket. It plays a crucial role in reducing medium- and high-voltage (e.g., 7.2 kV, 12.47 kV, 34.5 kV) power to low voltage (e.g., 120/240V) on the user side.
As a terminal hub in the distribution network, this product widely serves rural power grids, remote mountainous areas, scattered villages, agricultural production, and urban and rural residential electricity consumption. It can operate independently as a single-phase line or support three single-phase transformers combined into a three-phase transformer bank to meet different power supply mode requirements. It is an ideal solution for addressing problems such as excessively long power supply radius and high line losses.
It can be used as a single-phase transformer to supply power to residential or light industrial areas, or three units can be grouped together to form a three-phase distribution system, suitable for power grid upgrades, temporary power supply, and power supply in remote areas.
The core uses high-permeability grain-oriented silicon steel sheets (CRGO) or lower-loss amorphous alloy strips, combined with optimized coil design, significantly reducing no-load and load losses, meeting the latest DOE energy efficiency standards.
It uses mineral oil or high-flash-point natural ester oil (such as FR3) as the cooling and insulating medium, with high specific heat capacity and good fluidity. The oil tank, combined with corrugated or plate radiators, effectively increases the heat dissipation area and has excellent short-term overload withstand capability.
The pole-mounted suspension installation design is small in size and light in weight, eliminating the need for a separate transformer substation, significantly saving on infrastructure investment. Flexible single-pole or double-pole installation methods shorten the construction period. 5. Fully Sealed Structure, Durable and Reliable: The fuel tank adopts a fully sealed welded structure, effectively isolating it from external moisture, dust, and salt spray, exhibiting outstanding anti-aging and corrosion resistance. Combined with high-quality insulation materials, it adapts to various harsh outdoor climates and has a long service life.
It can be configured with fully automatic protection (CSP) function, integrating high-voltage fuses, surge arresters, and overload protection devices, which can automatically isolate internal faults and improve the safety of power grid operation.
| Parameter | Specification / Details |
| Rated Capacity | 5 kVA ~ 500 kVA (Customization supported, common specifications: 15, 25, 37.5, 50, 75, 100, 167 kVA) |
| High Voltage Side | 2.4 kV ~ 34.5 kV (Common: 7.2, 7.62, 12.47, 13.2, 13.8, 14.4, 19.92, 24.94 kV) |
| Low Voltage Side | 120/240V, 240/480V, 277V, 347V, 600V (Dual winding or single winding structure) |
| Tap Range High Voltage Side | ±2×2.5% or ±4×2.5% (No excitation voltage regulation) |
| Connection Group | II0 (Single Phase) |
| Number of Phases | Single-phase (can be grouped into a three-phase system with three units) |
| Rated Frequency | 50Hz / 60Hz |
| Cooling Method | ONAN (oil-immersed self-cooling) |
| Insulation Heat Resistance Class | Class A (105℃) |
| Insulating Oil Type | Mineral oil (IEC 60296) or environmentally friendly natural ester oil (FR3, high flash point, biodegradable) |
| Protection Class | IP54 (outdoor type) |
| Standards | ANSI C57.12.00 / C57.12.20, IEEE Std C57.12.20, CSA C2.2, DOE 2016 energy efficiency standard, IEC 60076 |
Core
Utilizes high-permeability grain-oriented silicon steel sheets (CRGO) or amorphous alloy strips, with a 45-degree fully oblique joint and no-perforation structure, effectively reducing hysteresis and eddy current losses.
High and Low Voltage Windings
Winded with high-quality copper or aluminum wire, using a cylindrical or layered structure, providing high insulation strength and strong short-circuit withstand capability.
Insulating Oil
Mineral oil or FR3 environmentally friendly natural ester oil, undertaking the three core tasks of insulation, heat dissipation, and arc extinguishing.
Transformer Tank
Constructed from cold-rolled steel or stainless steel plates, with a fully sealed structure and corrugated or heat sink fins on the outer wall to enhance heat dissipation.
Constructed from cold-rolled steel or stainless steel plates, with a fully sealed structure and corrugated or heat sink fins on the outer wall to enhance heat dissipation.
Porcelain or composite insulating bushings used to connect overhead lines. American transformers typically use insert bushings.
Tap Changer
Usually a non-excited tap changer, installed on the tank cover or side, used to adjust the output voltage.
Protection Accessories
Includes pressure relief valves (explosion-proof pressure relief), oil level gauges (window type or meter type), drain valves/sampling valves, hooks, grounding terminals, etc. Optional accessories include surge arresters, high-voltage current-limiting fuses, overload protectors, etc. [CITATION:2]
1. Core Product Advantages
① Extremely High Cost-Effectiveness: Compared to prefabricated substations or dry-type transformers, pole-mounted transformers have a simple structure, low manufacturing cost, and eliminate the high investment in ground infrastructure, making them an economical choice for large-scale power distribution upgrades.
② Significant Loss Reduction and Energy Saving: By using a "small capacity, dense distribution point, short radius" installation method, the transformer is placed close to the load center, which can significantly shorten the low-voltage power supply radius and reduce low-voltage line losses by up to 60% or more.
③ Flexible and Convenient Installation: Small in size and lightweight, it can be installed using single or double pole suspension, allowing for fast construction and saving ground space, making it particularly suitable for densely populated areas or mountainous regions with complex geographical conditions.
④ Stable and Reliable Operation: The fully sealed tank structure effectively prevents water and dust, ensuring long-term stable operation in harsh outdoor environments such as coastal salt spray, high altitude, and extreme temperature differences.
⑤ Excellent Fault Tolerance: Equipped with a fully self-protection (CSP) device, it can automatically disconnect the circuit in the event of an internal fault, preventing the accident from escalating and improving power grid safety. ⑥ Flexible Networking: It can be used for single-phase power supply or three units can be combined to form a three-phase transformer group, greatly facilitating rural power grid upgrades and temporary power supply.
2. Service Life
Under standardized operation and maintenance conditions (such as regular oil quality testing and seal inspection), the overall design service life of the equipment can reach 20-30 years. Optimized customized models using high-quality silicon steel sheets or amorphous alloy cores and environmentally friendly insulating oil can further extend the service life. Transformer aging mainly stems from insulating oil deterioration and seal aging; regular maintenance and replacement can significantly extend its lifespan.
1. Daily Maintenance
① Daily Inspection: Regularly check the external parts of the equipment for oil leaks and abnormal noises, observe whether the oil level gauge reading is within the normal range, and record the operating temperature.
② Oil Quality Testing: It is recommended to sample and test the dielectric strength, moisture content, and dissolved gas (DGA) of the insulating oil every 1-2 years, and filter, regenerate, or replace it based on the test results.
③ Component Inspection: Regularly calibrate pressure relief valves, oil level gauges, and other protective devices; check the tap changer's operation for flexibility; and tighten external wiring terminals.
④ Cleaning and Maintenance: Regularly clean dust and debris from the surface of the oil tank and heat sink to ensure unobstructed heat dissipation channels.
2. Safety Regulations
① Live-Line Work Safety: When working on the transformer platform, strictly adhere to the "Electrical Safety Work Regulations." Operations can only proceed after power is disconnected, tested for voltage, and grounded.
② Fire Safety: Conventional mineral oil is a flammable liquid. Open flames and the storage of flammable materials are strictly prohibited around the equipment. Dry powder fire extinguishers and other fire-fighting equipment must be readily available.
③ Fall and Impact Prevention: Personnel working at heights must wear safety belts. Tools and materials must be passed using ropes; throwing is strictly prohibited to prevent falling objects from injuring people.
④ Environmental Compliance: When replacing or disposing of insulating oil, use dedicated containers for recycling. Random dumping is strictly prohibited to prevent soil and water pollution.
1. Rural Power Grid Upgrading: As a core component of the "small capacity, dense distribution" strategy, it solves the problems of long power supply radius and unstable voltage in remote mountainous and pastoral areas.
2. Urban Residential Power Supply: Provides end-point power distribution access for residential communities and villa areas in suburban and urban-rural fringe areas.
3. Agriculture and Irrigation: Provides power for agricultural production such as greenhouse planting, farmland irrigation and drainage, and agricultural and sideline product processing.
4. Temporary Power Supply and Infrastructure: Serves as temporary or mobile power distribution facilities for construction sites, oil field operations, and mining.
5. Street Lighting Systems: Provides single-phase power for municipal road lighting, highway lighting, etc.
6. Distributed New Energy Grid Connection: Step-up or step-down grid connection of small distributed photovoltaic power stations or energy storage systems.
1. Environmental Risks
1. Lightning Strike Risk: Overhead lines are located at high outdoor locations and are susceptible to direct lightning strikes or induced lightning overvoltages. 1. **Zinc oxide surge arrester (MOA)** is recommended as standard equipment, or a model with full self-protection (CSP) function should be selected to include the surge arrester [CITATION:2].
2. **Leakage and Pollution Risk:** Mineral oil leakage can pollute the environment. In areas with high environmental protection requirements (such as water sources and farmland), it is strongly recommended to use environmentally friendly high-flash-point natural ester oils such as FR3, and to strengthen the inspection of the oil tank's sealing.
3. **Extreme Climate Risk:** In cold regions, attention should be paid to the low-temperature fluidity of the insulating oil; low-temperature antifreeze oils can be selected. In high-humidity or salt spray environments (coastal areas), C4-grade or higher anti-corrosion coatings and stainless steel fasteners are required.
4. **Fire Risk:** Mineral oil is flammable. In locations with strict fire protection requirements, it is recommended to use FR3 natural ester insulating oil with a flash point higher than 300℃, or to implement fireproofing measures.
5. **Mechanical Strength Requirements:** When installed on a pole, the oil tank must withstand wind loads, icing, and conductor tension. The structural strength of the oil tank and the secure welding of the support frame must be ensured. In earthquake-prone areas, a reinforced anti-vibration base is required.
2. Installation Restrictions
1. Load-bearing Capacity Restrictions: Before installation, verify the mechanical strength, burial depth, and guy wire condition of the pole to ensure it can withstand the total weight of the transformer (including support) and the tension of the conductors.
2. Safety Distance Restrictions: Installation must meet the minimum safety distance requirements for live parts to the ground, buildings, and crossing lines to ensure sufficient space for personnel operation and maintenance.
3. Altitude Adaptability Restrictions: For areas with altitudes exceeding 1000 meters, the reduced air density leads to a decrease in external insulation strength; therefore, customized reinforced insulation products (increasing creepage distance) are required.
4. Noise Restrictions: If the pole is near residential windows, pay attention to the transformer's no-load noise limit (e.g., ≤55dB at night); a low-noise design can be selected.
This product supports deep personalization customization and can provide precise adaptation based on project standards (ANSI/IEEE/IEC/DOE), installation environment, capacity requirements, and accessory configurations. Key dimensions are as follows:
| Customization Dimension | Optional Range / Description |
| Capacity and Voltage | 5 kVA ~ 500 kVA; High Voltage ≤ 34.5 kV, Low Voltage ≤ 600V |
| Tap Switch | No Excitation (±2×2.5% or ±4×2.5%) |
| Insulating Oil Type | Mineral Oil (IEC 60296) / Environmentally Friendly Natural Ester Oil (FR3) / Synthetic Ester Oil |
| Winding Material | All Copper, All Aluminum, High Voltage Aluminum / Low Voltage Copper |
| Tank Structure | Corrugated Plate Heat Sink, Plate Heat Sink; Ordinary Steel Plate or 304 Stainless Steel |
| Protection and Corrosion Protection | C3 / C4 / C5 Corrosion Resistance Rating; High Altitude, High Pollution Level Insulation Reinforcement |
| Protection and Accessories | Fully Automatic Protection (CSP, including fuse + surge arrester), Load Switch, Insertion Bushing, Intelligent Oil Temperature/Level Monitoring, Remote Fault Alarm, etc. |
| Phase Combination | Single-phase operation of a single unit, or three units grouped together to form a three-phase transformer bank. |
| Standards | ANSI C57.12.20 / IEEE C57.12.20 / CSA C2.2 / DOE 2016 / IEC 60076 |
| Colors and markings | User-specified color codes (e.g., Munsell or RAL), Chinese/English nameplates and warning labels. |
