We are did CT testing in live outdoor substation with CT analyzer ( OMICRON)
CT was enclosed with Oil Circuit Breaker.
The dis-connectors of CB both sides are opened and a personal Ground placed on the line side as shown in the fig.
The CB is closed and CT analyzer primary leads are connected as shown and secondary leads are connected with CT secondary terminals.
When equipment on it says " Secondary leads are open pls check".
Then we are checked completely and every think is ok and normal and CT secondary resistance are measured with same lead and its ok and perfect.
After long search we found 60 V in CT secondary leads without on the test kit.
Then we are inspect the substation and found one live line cross the bus as shown.
Due to this some induction voltage developed and leakage current flow through the personal ground ( As red line). This leakage primary current developed the voltage in secondary.
To rectify the problem we shifted the personal grounding to before the CT -1 as shown in fig. and induced current grounded before the CT.
Now CT secondary voltage is reduced and test is competed successfully.
