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Sigma Iy monitoring
10.3.2
Sigma_Iy monitoring function (i.e., sigma_Iy function) is provided in order that the circuit
breaker should be supervised. Flowing current at CB will be measured at every tripping;
respective flowing current amounts are integrated in the function. Consequently, the user can
check the CB interruption capability in the function. If a trip command is issued for every fault
occurrence, the function will identify the largest current at CT primary (i.e., I); then, the
function integrates it, which will be powered by parameter 'y'. The user can check the value of
total broken current in the sigma_Iy function.
Operation
(i)
Principle of sigma Iy
Equation (10.3-1) will be satisfied, if value "number of the fault currents (n)" can be provided:
For typical CB having parameter 'y', the user can set value '2.0' for the setting [SIGMA_IY-
Y]. This means that the accumulation is performed with the fault currents squared (I
other hand, the user should be set a small value (i.e., '1.0') for the [SIGMA_IY-Y] when a special
CB is required (that is, it can be for the high voltage system).
Maximum broken current
I 1
at the first
Tripping CB
Command issuing #1
Command issuing #2
The function will issue an alarm when the total value reaches the alarm level set by
[SIGMA_IY-Alarm]. Issuing will be performed when scheme switch [SIGMA_IY-AEN] = On.
y
∑ I
=I
+I
Y
1
y
∑ I
=I
+I
Y
1
Figure 10.3-4 Concept of Sigma_Iy function
- 845 -
y
y
y
+I
+⋯+I
n
2
3
Maximum broken current
I n
at the n
Command issuing #n
y
y
y
+I
+⋯+I
n
2
3
6F2T0207 (0.01)
(10.3-1)
). On the
2
th
Tripping CB
GRE200 (5,6)
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