Distribution Transformer: Key Equipment in the Power System

Overview

Distribution Transformer is a critical equipment in power transmission and distribution systems, responsible for converting medium-voltage power from the transmission grid to low-voltage power usable by end consumers. As the final link in the power system, distribution transformers directly impact power supply quality, reliability, and safety. According to international standard IEC 60076 and Chinese national standard GB 1094.1, distribution transformers typically refer to those with rated capacity up to 6300kVA and voltage levels in the 10-35kV range.

Working Principle and Technical Characteristics

Distribution transformers operate based on Faraday’s law of electromagnetic induction, achieving voltage transformation through the turns ratio between the primary coil (high-voltage side) and secondary coil (low-voltage side). The basic formula is:
V1V2=N1N2V2​V1​​=N2​N1​​
where V1V1​ and V2V2​ represent voltage, and N1N1​ and N2N2​ represent the number of coil turns.

Technical parameters of distribution transformers include:

• Rated capacity: Typically 50kVA to 2500kVA
• Loss requirements: No-load loss ≤0.5%~1.2%, load loss ≤1.0%~2.5% (according to GB 20052 standard)
• Cooling methods: Oil-immersed (ONAN) or dry-type (AN/AF)

Classification and Applications

Classification by Installation Location

• Pole-mounted transformers: Installed on utility poles, suitable for rural and suburban areas
• Pad-mounted transformers: Installed on ground foundations, commonly found in urban communities
• Indoor substations: Installed inside buildings, used for commercial and industrial areas

Classification by Insulation Medium

• Oil-immersed transformers: Use mineral oil or biological oil as insulation and cooling medium
• Dry-type transformers: Use epoxy resin casting, suitable for places with high fire protection requirements

Role in the Power System

Distribution transformers are critical equipment at the end of the distribution network, primarily converting medium and high voltage (typically 10kV or 35kV) to low voltage (such as 400V/230V) for direct use by industrial, commercial, or residential customers. They are typically installed on utility poles, ground pads, or in distribution rooms, with different types and configurations selected based on user needs and environmental conditions.

Advantages and Challenges

Advantages

• High-efficiency conversion: Modern distribution transformers can achieve efficiency over 95%
• High reliability: Design life typically exceeds 20 years
• Strong adaptability: Can adapt to various environmental conditions and load requirements

Challenges

• High cost: Especially for large and specially designed transformers
• Complex installation: Requires professional technicians for installation and maintenance
• Environmental impact: Oil-immersed transformers may present leakage risks

Future Development

With the development of smart grid technology, distribution transformers are moving toward intelligent, high-efficiency, and environmentally friendly directions. New generations of distribution transformers will integrate monitoring, communication, and control functions to achieve real-time condition monitoring and fault prediction, improving grid reliability and efficiency.

Conclusion

As an indispensable component in power systems, the performance of distribution transformers directly affects the power quality of end users. With technological advancements, distribution transformers continue to evolve to meet modern power systems’ higher requirements for efficiency, reliability, and intelligence.