On Site Current Transformer Testing Energy Meter under Test 1 2 - PowerPoint PPT Presentation

On Site Current Transformer Testing Energy Meter under Test 1 2 3 4 5 6 7 8 9 11 a b a b a b Problems: 1. Accuracy of Energy Meter A B A B A B ( SOLVED ) 2. Connection correctness in Potentaial measurement circuit Transformers 3. CT ratio and phase shift error 4. Burden of Current and Voltage Current Transformers S1 S2 S1 S2 S1 S2 Transformers P1 P2 P1 P2 P1 P2 L1 L2 L3 www.calmet.com.pl Poland, 65-472 Zielona Gora, 1 Kukulcza Street 18

Calport100 Plus Analyser & Tester of Energy Meters and Network 1 2 3 4 5 6 7 8 9 11 U1 U2 U3 CALPORT 100 Plus calmet *I1 U1 I1 *I2 U2 I2 *I3 U3 I3 Umax Umax U0 RS232 40kVAC 600VAC S1 S2 S1 S2 S1 S2 P1 P2 P1 P2 P1 P2 L1 Power 10VA 1A 85-265V L2 L3 N www.calmet.com.pl Poland, 65-472 Zielona Gora, 2 Kukulcza Street 18

Results of Connection Correctness Test Correct connection Primary Current Ip2 connected in reversed way Interchanged Secondary Windings IS2 & IS3 www.calmet.com.pl Poland, 65-472 Zielona Gora, 3 Kukulcza Street 18

CT Ratio & Phase Shift Error Ip – measured value of primary current Is – measured value of secondary current Ip/Is – measured CT Ratio Ip n /Is n – nominal value of CT Ratio ε ε ε ε – CT Ratio Error d ϕ ϕ ϕ – CT Phase Shift Error ϕ Example: CT ratio and phase shift error test CT: 25A/5A in phase L2 www.calmet.com.pl Poland, 65-472 Zielona Gora, 4 Kukulcza Street 18

CT Burden Test ε ε – CT Ratio Error in [%] ε ε Limits of Accuracy [%] Percent of Nominal Power of CT - Sn 25% 100% Energy Meter under Test Typical Working Area 1 2 3 4 5 6 7 8 9 11 Connecting Wires Ip Is Example: Rp – wires Resistance 2 mm Us1 Us2 0,0175 2 10 Ω ⋅ ⋅ m ρ ⋅ l m 0,35 = = = Ω R CU P 1 2 S mm Current Transformer Pp – Power losses in Wires CT 2 5 2 0,35 8,75 = ⋅ = ⋅ Ω = P I R A VA 2 P P www.calmet.com.pl Poland, 65-472 Zielona Gora, 5 Kukulcza Street 18

CT Burden Test by means of Calport100Plus 1 2 3 4 5 6 7 8 9 11 U1 U2 U3 CALPORT 100 Plus calmet *I1 U1 I1 *I2 U2 I2 *I3 U3 I3 U0 RS232 Power 10VA 1A 85-265V S1 S2 S1 S2 S1 S2 P1 P2 P1 P2 P1 P2 L1 Connection diagram during L2 CT Burden Test L3 N www.calmet.com.pl Poland, 65-472 Zielona Gora, 6 Kukulcza Street 18

CT Burden Testing - examples Current Transformer with nominal power Sn=20VA Correct, full power usage Nominal Power Sn is exceeded (99.88% of Sn) (125.2% of Sn) www.calmet.com.pl Poland, 65-472 Zielona Gora, 7 Kukulcza Street 18

Conclusions Extended measurement functions and graphic representation of results enables full test of Energy Measuring System on Site. Tested is not only Energy Meter but also all additional accessories like CT and PT. Tested are also working conditions of equipment by checking the wiring and burden (load) of transformers. www.calmet.com.pl Poland, 65-472 Zielona Gora, 8 Kukulcza Street 18