Current Transformer Tests CT Insulation Resistance 1kV Insulation Resistance Tester – Check CTs isolated or HV dead () Measure the insulation resistance (D70 D90 at terminal 10) M – Disconnect CT star point earth (terminal 10) () Measure the insulation resistance (D70 D90 at terminal 10) M – Reconnect CT star point earth (terminal 10) () CT Polarity Flick Test – Open CT shorting-links (terminals 1 and 2) () Check L1 phase CT polarity D11 at terminal 1 (+ve) to D70 at terminal 10 (-ve) () – Check L3 phase CT polarity D51 at terminal 2 (+ve) to D70 at terminal 10 (-ve) () – CT Ratio Check Primary Injection or Prevailing Load* – CT Ratio CT Ratio Injected Calculated Measured Ratio Primary Secondary Primary Secondary Term Secondary Correct Phase Current Current Current* Current Current [A] [B] [C] [D = B / A * C] [E] [E = D] L1 200A 5A 50 / 100A A A 1-10 A () L3 200A 5A 50 / 100A A A 2-10 A () L1 400A 5A 50 / 100A A A 1-10 A () L3 400A 5A 50 / 100A A A 2-10 A () On completion of test ensure correct CT ratio low (200A) or high (400A) as specified by () designer is selected * Delete as applicable. CT Relationship to VT Output at Terminal Box L1 CT associated with L1 voltage ** () L3 CT associated with L3 voltage ** () ** If all CT and VT tests are correct the CT relationship to the VT is proven and the above can be ticked CT Burden Maximum CT burden per phase at metering unit terminal box 0.5 VA Maximum CT burden per phase at meter terminal box 7.5 VA Final Checks Reconnect metering multi-core cable (if disconnected) () If metering multi-core cable is not connected leave CTs shorted close shorting () – links (terminals 1 and 2)
Current Transformer Tests CT Insulation Resistance – 1kV Insulation Resistance Tester Check CTs isolated or HV dead () Measure the insulation resistance (D70 – D90 at terminal 10) M Disconnect CT star point earth (terminal 10) () Measure the insulation resistance (D70 – D90 at terminal 10) M Reconnect CT star point earth (terminal 10) () CT Polarity – Flick Test Open CT shorting-links (terminals 1 and 2) () Check L1 phase CT polarity – D11 at terminal 1 (+ve) to D70 at terminal 10 (-ve) () Check L3 phase CT polarity – D51 at terminal 2 (+ve) to D70 at terminal 10 (-ve) () CT Ratio Check – Primary Injection or Prevailing Load* Phase CT Ratio Primary Current CT Ratio Secondary Current Injected Primary Current* Calculated Secondary Current Term Measured Secondary Current Ratio Correct [A] [B] [C] [D = B / A * C] [E] [E = D] L1 200A 5A 50 / 100A A A 1-10 A () L3 200A 5A 50 / 100A A A 2-10 A () L1 400A 5A 50 / 100A A A 1-10 A () L3 400A 5A 50 / 100A A A 2-10 A () On completion of test ensure correct CT ratio low (200A) or high (400A) as specified by designer is selected () * Delete as applicable. CT Relationship to VT Output at Terminal Box L1 CT associated with L1 voltage ** () L3 CT associated with L3 voltage ** () ** If all CT and VT tests are correct the CT relationship to the VT is proven and the above can be ticked CT Burden Maximum CT burden per phase at metering unit terminal box 0.5 VA Maximum CT burden per phase at meter terminal box 7.5 VA Final Checks Reconnect metering multi-core cable (if disconnected) () If metering multi-core cable is not connected leave CTs shorted – close shorting links (terminals 1 and 2) ()
ECP+11-0515c+Schneider+HV+Metering+Unit+3+Limb+Test+Form.docx