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10.4.1 Operation of sigma Iy
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 (
). On the other hand, the user can be required to set a less value (say ‘1.0’) for the
[SIGMA_IY-Y] when a special CB is required (that is, for the high voltage system).
Figure 10.4-1 Concept of Sigma_Iy function
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].
Maximum broken current
at the first
Maximum broken current
at the n
th
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