You mentioned “transformer test transformer” again, combined with your previous inquiries about “partial discharge tester” and “microcomputer relay protection tester”, it seems you may be constructing a comprehensive transformer testing scheme, or organizing a list of test equipment. To help clarify your thoughts, I will place the test transformer within the entire transformer testing process, explaining its coordination with other equipment and its core role: 1. The Core Role of Test Transformer in Transformer Testing In the factory, acceptance, or preventive tests of power transformers, the test transformer is the “heart” that generates high voltage. Without it, the following key tests cannot be performed: External Applied Voltage Withstand Test (AC Withstand Voltage Test): Purpose: To assess the strength of the transformer's main insulation (high-voltage winding to ground, high-voltage to low-voltage). Operation: Use the test transformer to raise the voltage to the specified value (e.g., 28kV, 35kV, 68kV, depending on the voltage level) and maintain it for 1 minute. Supporting Equipment: Requires a voltage regulator (to control the rate of voltage increase), a sphere gap (overvoltage protection), and a voltage divider (to measure high voltage). Induced Overvoltage Test: Purpose: To assess the transformer's longitudinal insulation (between turns, layers, and sections) as well as phase-to-phase insulation. Special Feature: Typically requires a triple-frequency power supply (150Hz) to drive the test transformer to avoid core saturation, thereby applying 2 times the rated voltage on the low-voltage side and inducing high voltage on the high-voltage side. High Voltage Source for Partial Discharge Test: The partial discharge tester you asked about earlier is the “ear” (detecting signals), while the corona-free test transformer is the “mouth” (providing a clean high-voltage environment). Key Point: When conducting partial discharge tests, the requirements for the test transformer are extremely high; it must be a dedicated transformer with low partial discharge and corona-free design, otherwise background noise will drown out the actual discharge signals. 2. Complete Transformer Test Equipment List (Reference) If you are configuring a laboratory or field test vehicle, a standard transformer test system typically includes: Table Test Item Core Equipment Auxiliary/Supporting Equipment Function Insulation Resistance/Absorption Ratio Megohmmeter (2500V/5000V) None Preliminary check for insulation moisture DC Resistance DC Resistance Tester None Check winding welding quality and tap changer contact condition Turns Ratio and Group Vector Turns Ratio Tester None Verify turns ratio and connection group correctness Dielectric Loss (tanδ) Dielectric Loss Tester (Bridge) Standard Capacitor Assess overall insulation aging and moisture External Applied Voltage Withstand Test Transformer + Voltage Regulator Sphere Gap, Voltage Divider, Microammeter Assess main insulation strength Induced Overvoltage + Partial Discharge Triple-Frequency Power Supply + Corona-Free Test Transformer Partial Discharge Tester, Coupling Capacitor Assess longitudinal insulation and detect internal defects No-Load/Load Characteristics Power Analyzer / High-Current Generator Voltage Regulator Measure loss parameters Protection Calibration Microcomputer Relay Protection Tester None Verify transformer protection device logic
