If it's a power supply bureau/large power plant: directly use a three-phase fully automatic DC resistance tester (with waveform analysis function)



Although it's more expensive, it saves more on labor costs and power outage time costs. If it's a small factory/construction team: a high-performance single-phase DC resistance tester (with fast demagnetization) offers the best cost-effectiveness. 3. Typical fault waveforms and data analysis (expert-level application) High-end DC resistance testers not only provide a value but also reveal deep hidden issues through waveforms and three-phase unbalance rate: Three-phase unbalance rate exceeds standard: Standard: For transformers above 1600kVA, phase-to-phase difference ≤2%; when there is no neutral point lead-out, line-to-line difference ≤1%. Diagnosis: A certain phase resistance is too high: the phase winding lead has a cold solder joint, tap changer has poor contact, or wire is broken. A certain phase resistance is too low: there may be inter-turn short circuit (needs to be confirmed with no-load test). On-load tap changer (OLTC): Normal waveform: resistance changes smoothly, transition process is clear, no obvious burrs. Abnormal waveform: Waveform interruption: open circuit occurs during switching (resistance infinite), indicating that the contact is not connected or the drive mechanism is stuck. Waveform burrs/jitter: unstable contact of the contacts, possibly due to burning or insufficient spring pressure. Transition time too long: mechanical mechanism wear or excessive oil chamber damping. 2026 new feature: the instrument has built-in AI algorithm that automatically compares with standard waveform library and directly gives a diagnostic conclusion of "qualified/caution/severe". 4. Linkage with "high-current generator": full process of temperature rise test Combined with the high-current generator you asked about before, the DC resistance tester plays a key role in the temperature rise test: Cold state measurement: before powering on, use the DC resistance tester to accurately measure the winding resistance