Electric heating and electrical four is not a standard industry term
Based on your previous consecutive inquiries about test transformers, DC resistance testers, and dielectric loss testers, it is speculated that you may be asking about one of the following two situations: The “four major conventional electrical tests” in power preventive tests (possibly mistakenly recorded as “electric heating” or referring to tests involving temperature/heat). The fourth category of related instruments or the fourth test item of “electrical tests” and “electric heating equipment”. Or a “four-in-one” integrated device from a specific manufacturer (such as the “Electric Heating Electrical” brand). Combined with the current industry context (2026), the most reasonable explanation is that you want to understand the core “four” key tests in preventive tests of high-voltage electrical equipment, or the fourth commonly used precision test instrument. In power operation and maintenance, for core equipment such as transformers, the most classic “four major” tests usually refer to: Insulation resistance test (using a megohmmeter) DC resistance test (using a DC resistance tester, which you have already asked about) Dielectric loss and capacitance test (using a dielectric loss tester, which you have already asked about) AC withstand voltage test (using a test transformer, which you asked about first) If you are referring to the fourth commonly used high-precision instrument, usually after the above three, the next is: Oil chromatographic analyzer (DGA): detects dissolved gases in transformer oil to judge internal latent faults (such as overheating, discharge). Or Partial discharge tester (PD Tester): detects tiny discharges inside the insulation. Assuming you are referring to the “fourth core test” or “fourth key instrument” In the complete electrical test process, after DC resistance, dielectric loss, and withstand voltage, oil chromatographic analysis or partial discharge testing is often regarded as a deeper diagnostic method. 1. Transformer oil chromatographic analyzer (DGA - Dissolved Gas Analysis) This is the most sensitive method for judging internal latent faults (especially “thermal” faults and “electrical” faults) in transformers, perfectly fitting the “electric heating” concept you mentioned. Core function: analyzes hydrogen dissolved in transformer oil (
