Measuring the quality of oilimmersed transformers relies on standardized tests and key performance indicators covering electrical, insulation, thermal, and structural aspects. Here’s a concise, practical guide:

　　1. Core Electrical Performance Tests

　　These verify operational efficiency and stability.

　　Load loss test: Measures power consumption under rated load (GB/T 64512015 standard). Lower loss indicates better energy efficiency—amorphous alloy cores have 3060% lower load loss than traditional silicon steel.

　　Noload loss test: Assesses iron loss at rated voltage (no load). Qualified transformers must meet the loss limits specified by their capacity class.

　　Voltage regulation test: Checks output voltage stability when load changes (allowable deviation ≤±5% for most grades).

　　Shortcircuit impedance test: Ensures the transformer can withstand shortcircuit currents without damage (impedance value typically 410% for distribution transformers).

　　2. Insulation Performance Evaluation

　　Insulation is critical for safety and lifespan.

　　Dielectric strength test: Applies AC/DC withstand voltage to windings (e.g., 10kV transformers require 35kV AC for 1 minute) to detect insulation defects.

　　Oil quality analysis: Tests transformer oil for moisture (≤10ppm), dielectric breakdown voltage (≥35kV), acid value (≤0.03mgKOH/g), and dissolved gas content (e.g., methane ≤100μL/L, ethylene ≤50μL/L) to avoid insulation aging or arcing.

　　Insulation resistance test: Uses a megohmmeter to measure resistance between windings and ground (≥1000MΩ for 10kV transformers at 25℃).

　　3. Thermal Performance & Structural Checks

　　Temperature rise test: Runs the transformer at rated load to measure winding and oil temperature rises (max allowable oil rise ≤60K, winding rise ≤75K for ONAN cooling).

　　Structural integrity: Inspect tank tightness (no oil leakage), core clamping force (prevents vibration), and radiator efficiency (ensures heat dissipation).

　　Vibration & noise test: Qualified transformers have noise levels ≤65dB(A) for distribution grades (reduces environmental impact).

　　4. Factory Qualification & Traceability

　　Verify manufacturer certifications (ISO 9001, GB/T 1094 series).

　　Check serial number, production date, and test reports (each transformer should have a detailed factory test record).