Formålet med DC-motstandstesteren for å måle DC-viklingsmotstanden til transformatorviklingen er å sjekke sveisekvaliteten til viklingsskjøtene og om det er kortslutning mellom viklingene. Om kontaktposisjonen til spenningskranbryteren er god, om den faktiske posisjonen til kranen stemmer overens; om ledningen er ødelagt. Strandede ledninger og viklinger er ødelagt. Når transformatoren er overhalt, eller etter at kranposisjonen er endret, eller etter at utløpsfeilen er kortsluttet, er det nødvendig å måle DC-viklingsmotstanden til viklingen og bøssingen.
Målemetoden til transformatorens DC-motstandstester er som følger:
(1) Strøm, voltmetermetode, også kjent som spenningsfallmetode, prinsippet er å måle spenningsfallet på motstanden gjennom likestrøm i den målte motstanden, og beregne den målte motstandsverdien i henhold til Ohms lov. Siden den interne motstanden til amperemeteret og voltmeteret vil påvirke måleresultatene, bør du vurdere nøye hvordan de er koblet til målekretsen.
(2) Balanced bridge method. This is a method that uses the principle of bridge balance to measure the resistance of the DC winding. Commonly used balanced bridges include single-arm bridges and double-arm bridges. When measuring the DC winding resistance of the transformer, the transformer DC resistance tester should be performed after the transformer is powered off and the high-voltage wire is removed. For large and large-capacity power transformers, the charging time constant τ of the rl series circuit is very large, so that each measurement takes a long time to wait for the current and voltmeter to indicate stable, so the work efficiency is very low, and special instruments (such as constant Current). Replacing the power supply in the test with a power supply can greatly reduce the test time. The standard for measuring the DC winding resistance of transformer coils is: For transformers above 1600 kva, the difference in resistance of each phase winding should not exceed 2 percent of the three-phase average value, and the neutral line should have no winding point lead wire. The difference between the lines should not be greater than 1 percent of the average value of the three phases. For transformers of 1600kva and below, the difference between the phases is generally not greater than 4 percent of the three-phase average, and the difference between the lines is generally not more than three-phase. 2 percent of the average value, compared with the measured value in the previous part, its change should not exceed 2 percent . And the neutral point lead wire should not be twisted. The difference between the lines should not be greater than 1 percent of the average value of the three phases. For transformers of 1600kva and below, the difference between the phases is generally not greater than 4 percent of the three-phase average, and the difference between the lines is generally not more than three-phase. 2 percent of the average value, compared with the measured value in the previous part, its change should not exceed 2 percent . And the neutral point lead wire should not be twisted. The difference between the lines should not be greater than 1 percent of the average value of the three phases. For transformers of 1600kva and below, the difference between the phases is generally not greater than 4 percent of the three-phase average, and the difference between the lines is generally not more than three-phase. 2 percent of the average value, compared with the measured value in the previous part, its change should not exceed 2 percent .