Current Transformer Insulation Resistance Test

To ensure that each winding of the current transformer has sufficient insulation resistance with respect to earth ct body and between the two secondary cores.

Current transformer insulation resistance test.

Current transformer loop test. The transformer resistance testing will reveal a lot of details about the transformer by measuring the winding resistance of a transformer from one hv transformer bushing to another. Generally transformer windings are immersed in insulation liquid and covered with paper insulation hence it is impossible to measure the actual winding temperature in a de energizing transformer at the time of transformer winding resistance measurement. Ct resistance excitation curve ratio polarity test.

Developed early in the 20th century the insulation resistance ir test is the oldest and most widely used test for assessing the quality of insulation. Transformer winding resistance measurements are obtained by passing a known dc current through the winding under test and measuring the voltage drop across each terminal. Also acceptable values of insulation resistance depend upon the equipment you re testing. An approximation is developed to calculate the temperature of winding at that condition.

Leakage reactance 3 phase equivalent and per phase 6. You might think of a winding resistance test set as a very large low resistance ohmmeter. The insulation resistance test consists in measuring the insulation resistance of a. September 5 7 2018 ieee c57 152 2013 ieee guide for diagnostic.

Apply the test voltage and note the reading. The transformer neutral bushing is to be disconnected from earth during the test. The international electrical testing association neta specification maintenance testing specifications for electrical power distribution equipment and. The insulation resistance test is the second test required by the electrical safety testing standards.

Modern test equipment for this purposes utilizes a kelvin bridge to achieve results. Value at 60 seconds after application of the test voltage is referred to as the insulation resistance of the transformer at the test temperature. Ttr transformer turns ratio 5. Turns ratio test 8.

Historically many field electricians use the somewhat arbitrary standard of 1 megohm per kv. Insulation resistance is the ratio of the applied voltage dc to the total leakage current.