Characteristic
Value
Start time for under current stage
2,
3
Typically 26 ms
Reset time for overload and alarm
stage
Typically 60 ms
Reset ratio
Typically 0.96
Operate time accuracy in definite
time mode
1 % of the set value or ±20 ms
Operate time accuracy in inverse
time mode
10 % of the theoretical value or ±20 ms
Suppression of harmonics for under
current stage
DFT: -50 dB at f = n × fn, where n = 2,3,4,5,..
4.12.2
Current unbalance protection for capacitor banks
CUBPTOC (ANSI 60N)
4.12.2.1
Identification
Table 1063: Function identification
Function description
IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Current unbalance protection for
shunt capacitor banks
CUBPTOC
dI>C
60N
4.12.2.2
Function block
Figure 627: Function block symbol
4.12.2.3
Functionality
The current unbalance protection for shunt capacitor banks function CUBPTOC
is used to protect the double-Y-connected capacitor banks from internal faults.
CUBPTOC is suitable for the protection of internally fused, externally fused and
fuseless applications.
CUBPTOC has two stages of operation, that is, operation stage and alarm stage.
In the operating stage, CUBPTOC starts when the measured unbalance current
1
Harmonics current before fault = 0.5 × I
n
, harmonics fault current 1.5 ×
Start value, results based
on statistical distribution of 1000 measurements
2
Includes the delay of the signal output contact
3
Harmonics current before fault = 1.2 × I
n
, harmonics fault current 0.8 ×
Start value, results based
on statistical distribution of 1000 measurements
1MRS759142 F
Protection functions
REX640
Technical Manual
1119