In order to add current transformer to the scheme, user should select from Electric elements panel. Current transformer parameters tab is opened by double clicking on the inserted current transformer element .
Current transformer tab is designed to calculate ALF value, which is “Accuracy limiting factor” of the transformer. However, properties that will be specified for the current transformer, is not going to affect trip unit operation in any way. Explanation of the current transformer parameters are provided below:
CT type – current transformer type (name). If it is 5P20, then 5P is accuracy class and 20 is accuracy limiting factor (ALF). This means that when current is less than “20 * In “(In is nominal current) then accuracy is 5%.
Coefficient – current transformer ratio.
Wire loop length – Wire loop length should be calculated according to the CT connection type (4- or 6- wire connection).
The difference between 4 and 6 wire schemes is depicted below.
For example, if distance between the current transformer and relay is 5 meters, then in case of 6 wire connection wire loop length should be taken as 2 x 5 = 10 m and only 1,2 x 5 = 6 m for 4 wire connection.
PN – is current transformer burden at which rated accuracy of the transformer is reached.
Wire cross section and Wire material – parameters that software need to calculate resistance of the wire. User should specify this data to represent real installation conditions of the transformer.
IED load – trip unit winding resistance (internal resistance of the connected relays).
Note: Some of the parameters needed for ALF calculation EA-PSM will be taken automatically from the load flows and short circuits calculation results, therefore, user should make sure that these calculations are done, and all network parameters are specified correctly.
The current transformer tab is designed to calculate ALF value, which is “Accuracy limiting factor” of the transformer. However, properties that will be specified for the current transformer, is not going to affect trip unit operation in any way. Explanation of the current transformer parameters are provided below:
CT type – current transformer type (name). If it is 5P20, then 5P is accuracy class and 20 is accuracy limiting factor (ALF). This means that when current is less than “20 * In “(In is nominal current) then accuracy is 5%.
Coefficient – is current transformer ratio.
PN – is current transformer burden at which rated accuracy of the transformer is reached.
IED load – trip unit winding resistance.
Explanation of the breaker properties are provided below:
from Electric elements panel. Current transformer parameters tab is opened by double clicking on the inserted current transformer element 
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