MR ETOS IM - Motor Current Index (MCI)

7 Operation
Maschinenfabrik Reinhausen GmbH 2019180 5163667/06 ENETOS
®
IM
7.11.3 Motor Current Index (MCI)
The term Motor Current Index (in accordance with IEEEPC57.143) de-
scribes the area below the curve of the motor current during an on-load tap-
change operation. The Motor Current Index is a measurement that takes into
account the inrush current, the present tap-change conditions and the tap-
change duration.
3
6
9
12
15
A
0
0 1 2 3 4s
I
t
200
400
600
800
1000
0
Tap-change operations
MCI
Motor current Motor Current Index
Figure133: Example illustration of the temporal progression of the motor current I and of the
Motor Current Index MCI calculated from this in comparison with the values of the MCI for fur-
ther on-load tap-change operations
The motor runtime and therefore the Motor Current Index differ depending
on the type of tap-change operation. The Motor Current Index will therefore
be categorized in accordance with the following types of tap-change opera-
tion to aid comparison:
Tap-change operation type Description
TSO/CSO
Tap selector operation / change-
over selector operation
The switching direction is the same as the pre-
vious switching direction. Example:
▪ Previous tap-change operation: pos. 2 →
pos. 3
▪ Current tap-change operation: pos. 3 →
pos. 4
RSO
Reverse tap-change operation
The switching direction is not the same as the
previous switching direction. Example:
▪ Previous tap-change operation: pos. 2 →
pos. 3
▪ Current tap-change operation: pos. 3 →
pos. 2
Unknown The tap-change operation type is unknown.
This is the case after the device has been
restarted or if the motor protective switch has
been triggered.
Table53: Tap-change operation types