What tests need to be performed on instrument transformers?





I. The test items for instrument transformers should include the following contents:



(1) Measure the insulation resistance of windings; (Test equipment: MS-2000 Insulation Resistance Tester)



(2) Measure the dielectric loss tangent tanδ of instrument transformers with voltage levels of 35kV and above; (Test equipment: MS-101D Anti-interference Dielectric Loss Tester)



(3) Partial discharge test;



(4) AC withstand voltage test; (Test equipment: MSXB Series Series Resonance Test Device)



 



MSXB Series Series Resonance Test Device



(5) Insulating medium performance test;



(6) Measure the DC resistance of windings; (Test equipment: MS-510 DC Resistance Tester)





(7) Check the connection group and polarity; (Test equipment: MS-100B Ratio and Group Tester)



(8) Error measurement;



(9) Measure the excitation characteristic curve of current transformers;



(10) Measure the excitation characteristics of electromagnetic voltage transformers;



(11) Detection of capacitor voltage transformers (CVT);



(12) Sealing performance inspection;



(13) Measure the insulation resistance of the core clamping bolts.



 



MS-601F Full-function Comprehensive Characteristic Tester for Instrument Transformers



Note: The tests for current transformers in SF6 gas-insulated switchgear and bushing-type current transformers should be carried out according to the provisions of items 1, 6, 7, 8, and 9 of GB50150-2006 Standard for Acceptance Test of Electric Equipment Installation Engineering - Instrument Transformers.



II. Measuring the insulation resistance of windings should comply with the following regulations:



(1) Measure the insulation resistance of the primary winding to the secondary windings and the shell, between each secondary winding, and between each secondary winding and the shell; the insulation resistance value should not be less than 1000MΩ;



(2) Measure the insulation resistance between sections of the primary winding of current transformers; the insulation resistance value should not be less than 1000MΩ, but if it cannot be measured due to structural reasons, it may be omitted;



(3) Measure the insulation resistance of the last screen of capacitor-type current transformers and the grounding terminal (N) of voltage transformers to the shell (ground); the insulation resistance value should not be less than 1000MΩ. If the insulation resistance of the last screen to ground is less than 1000MΩ, its tanδ should be measured;



(4) The insulation resistance measurement should use a 2500V megohmmeter.



III. The measurement of the dielectric loss tangent tanδ for instrument transformers with voltage levels of 35kV and above should comply with the following regulations:



(1) The tanδ measurement voltage for the windings of instrument transformers should be measured at 10kV, and the tanδ should not be greater than the data in Table 9.0.3. When there is doubt about the insulation performance, the high-voltage method can be used for testing within the range of (0.5～1)Um, and the change in tanδ should not be greater than 0.2%, and the change in capacitance should not be greater than 0.5%;



(2) The measurement voltage for the last screen tanδ is 2kV.