DOC. MIE91093 Rev. 1.34 Page 137 of 145
. Take from the label the following parameters: nominal
current IN; VA rating; accuracy class (for instance, 5P20).
Then, compute:
. Maximum voltage at IN: Max V(IN) = VA / IN;
. Knee voltage = Max V(IN) * P
Example: IN = 5 A; VA = 20 VA; class 5P20.
. Max V(IN) = 20 / 5 = 4 V;
. Knee voltage = 4 * 20 = 80 V.
This knee can be tested very easily. The maximum nominal
knee voltage is 200 V, as you need to proceed some more
further.
1.19.2. Test set connection
The saturation knee test of a CT is performed applying a
voltage to the CT secondary side, and slowly increasing it
while measuring the corresponding current. The connection is
shown in the following.
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