Toshiba GR200 Series Instruction Manual page 1158

Operation of sigma Iy
10.4.1
When the value 'n' is provided as the number of the fault currents, equation (10.4-1) is satisfied:
As setting for a conventional CB with regard to the parameter 'y', the user can set a value
'2.0' for the [SIGMA_IY-Y]; that is, the accumulation is performed with the fault currents
squared (I ). On the other hand, the user can be required to set a less value (say '1.0') for the
2
[SIGMA_IY-Y] when a special CB is required (that is, for the high voltage system).
Maximum broken current
I 1
at the first
Tripping CB
Command issuing #1
Command issuing #2
The sigma_Iy function can designed to issue an alarm when the synthesized broken
current value reaches an alarm level set by [SIGMA_IY-Alarm]; issuing an alarm is ready when
the user sets On for scheme switch [SIGMA_IY-AEN].
y
∑ I =I
Y
1
y
∑ I =I +I
Y
1
Figure 10.4-1 Concept of Sigma_Iy function
- 1137 -
y y y
+I +I +⋯+I
n
2 3
I n
y y y
+I +⋯+I
n
2 3
6F2S1915 (0.46)
(10.4-1)
Maximum broken current
at the n
th
Tripping CB
Command issuing #n
GRZ200 (Soft 031 & 032)