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10.2.16 Supervision of the current in zero-sequence (I0 error)
The zero-phase-sequence current entering to the input circuit is monitored; it is possible to
provide a high sensitivity to detect the failure using the residual circuit current. Equation
(10.2-2) is represented for the supervision:
where,
I
e
Residual current
Max(|I
a
|, |I
b
|, |I
c
|) The largest amplitude among I
a
, I
b
and I
c
k
0
: 5% of the rated current†
†Note: The rated current above the equation is defined with the setting of the VCT. For
more information regarding the VCT, see Chapter
Technical description:
Transformer module for AC analog input
.
(i) Error level
Generally, the default error level has been set at level 3 (Minor error), but the user can program
the level using settings [CHK_IZ:LVl] and [CHK_IZ2:LVl]; then, set On for the settings
[CHK_IZ:Sw] and [CHK_IZ2:Sw]. The time to detect can be set using [CHK_IZ:Timer] and
[CHK_IZ2:Timer], each of which is set for 15 seconds as default. If the error is cleared, resetting
will be performed after the elapse of setting time.
(ii) Error message
When the function operates and detects error, an error message can be shown at the LED and
the LCD screen.
Table 10.2-33 Error messages provided by the supervisor in CHK_IZ
Meaning of the information
Detection of flowing the zero-sequence current
Table 10.2-34 Detailed information in Hexadecimal in CHK_IZ
Meaning of the detailed information
(No information is displayed)
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