Based on the cross-linking of the cans, in case of an element fault, the capacitance of the parallel cans must be
determined first:
•
Capacitance of 2 parallel cans in case of an element fault:
C
2K,1EF
= 19.456 μF + 19.67 μF = 39.126 μF
Capacitance in the quarter of C1 in case of an element fault:
C1
1EF
= 3.0249 μF
•
Capacitance in the quarter of C3 in case of an element fault:
C3
1EF
= 2.6217 μF
2g) Capacitance in the Quarters of the H Connection without Element Fault
•
Capacitance in the quarters of C1 and C3 without element fault:
2h) Unbalanced Current and Threshold-Value Setting in Case of a C-Element Fault
•
Unbalanced current:
•
Unbalanced current in case of an element fault in C1:
•
Unbalanced current in case of an element fault in C3:
The lesser of both values is relevant for the setting of the threshold value. For instance, set the threshold to
75 % of this value:
•
Threshold value (primary): 0.75 ⋅ 20.0 mA = 15.0 mA
The threshold is a primary value. In order to detect this, a 1:1 transformer is required. Under this assumption,
the secondary setting value is equal to the primary value.
NOTE
Use sensitive device current inputs in order to apply secondary thresholds of < 30 mA.
Capacitor Bank Protection
7.4 Current-Unbalance Protection for Capacitors, 3-Phase
SIPROTEC 5, Overcurrent Protection, Manual 989
C53000-G5040-C017-8, Edition 07.2017
To Next Page
Loading...
