Distribution Transformer Selection

Distribution Transformer Selection and Load Matching Guide

The selection of distribution transformers, a core component of power systems, and their load matching directly affect equipment lifespan and operational costs. It is essential to scientifically calculate the load and make reasonable selections. The following points are analyzed from both normative and practical perspectives:

I. Foundation of Load Calculation: Power and Capacity Conversion

Rated capacity (kVA) and load power (kW) are converted through power factor (PF): Load power = Capacity × PF. In industrial and commercial scenarios, PF is generally 0.85 – 0.9. It is recommended to install capacitor compensation equipment (installation spacing ≥ 50mm, anchor bolt fixation, wire connection at 45° – 60° angle). Before operation, check the tightness of the wiring, with an operation interval of 1 minute. Inductive loads need to be supplied separately or buffer capacity reserved.

II. Selection Criteria: Standards and Capacity Margin

Long-term load factor control standards: Civil buildings ≤ 85% (JGJ16-2008), industrial settings 75% – 85% (Power Distribution Design Manual), charging stations single bus ≤ 100% (GB/T 51313). Capacity selection should be increased by 10% – 20%, and derating is required in high-temperature/high-harmonic environments.

III. Key Influencing Factors: Details Determine Efficiency

1. Temperature and Heat Dissipation: With 25℃ as the base, reserve 10% – 15% redundancy in high-temperature areas, and clean the heat sink regularly.
2. Harmonic Interference: Install filtering devices or choose anti-harmonic models.
3. Load Characteristics: The capacity demand for resistive loads is low, inductive loads need compensation, and for mixed loads, reserve a 10% safety margin.

IV. Practical Case Analysis

For a commercial complex with a power demand of 655kW (PF=0.9), a 1000kVA model is selected; for an industrial park with a peak demand of 3529kVA, a 3500kVA model with overload capacity is chosen; for coastal projects, natural ester insulating oil transformers (flash point > 300℃, with a 40% reduction in no-load loss) are adopted.

V. Optimization Suggestions: Full Life Cycle Management

Match scene standards in the design stage (e.g., load rate in Beijing ≤ 80%); monitor temperature/current/harmonic during operation; conduct annual maintenance to check oil quality indicators (breakdown voltage ≥ 25kV, moisture ≤ 15mg/L, gas content ≤ 1%); handle abnormalities with vacuum oil filtration and chromatographic analysis.

Summary:

Balance technical specifications, economic factors and environmental conditions, follow the three major principles of “capacity reserve margin, power factor compensation and environmental adaptation”, and ensure the efficient and safe operation of the power system.