A wrong diagnosis is expensive: a healthy transformer is taken out of service, or a real fault is missed. Most errors come from a handful of causes.
- Instrument accuracy. Thermometers, meters and insulation testers out of calibration give misleading numbers. Check calibration dates before testing.
- Experience. Staff who do not know the design and the usual failure modes may overlook early signs or read too much into normal variation.
- Site conditions. Heat, humidity and electromagnetic interference affect readings. Insulation resistance measured on a humid day can look low without any real fault.
- Operating history. Without the record of overloads, voltage surges and load pattern, it is hard to tell a long-term overload problem from a sudden fault.
- Hidden or combined faults. Some faults have several causes at once, or sit where tests cannot easily reach.
- Incomplete records. Missing commissioning values and trend data leave nothing to compare against.
A typical example: a modest rise in oil temperature is blamed on an internal fault when the real cause is a hot day and a heavier load. Comparing with ambient temperature and load history would have shown it.
How to reduce the risk
- Keep commissioning test results and repeat the same tests at fixed intervals
- Record load, oil temperature and ambient temperature together
- Use calibrated instruments and note test conditions
- Confirm one abnormal result with a second, independent test before deciding
Our service page explains the support the factory provides.