Current Transformer Ratio And Polarity Tests; Figure 1.4-4 -Connections For Overall Fault Setting Tests By Secondary Injection; Figure 1.4-5 -Connections For Ct Ratio And Polarity Tests Using 3P Load Current - Siemens 7PG2113 Technical Manual

7PG2113/4/5/6 Commissioning & Maintenance
E E

Figure 1.4-4 -Connections for Overall Fault setting Tests by Secondary Injection

1.4.4

Current transformer ratio and polarity tests

Remove the trip links at both ends of the feeder. Connect ammeters in the current transformer secondary leads at
each end in turn, as shown in Figure 1.4-5. Pass three phase load current through the primary and check the ratio
of each current transformer by comparing the secondary current in each phase with the corresponding primary
current. Check the polarity of the current transformers; the reading of ammeter X in the neutral circuit should be
negligible compared with the secondary phase-currents. Some current may exist in the neutral circuit due to
unbalance of primary load current and/or secondary burden.

Figure 1.4-5 -Connections for CT Ratio and Polarity Tests using 3P Load Current

©2010 Siemens Protection Devices Limited Chapter 6 Page 16 of 77