Advertisement
10.2.17 Supervision of current in zero-sequence (IZ 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:
1.
where,
I e
Max(|I a |, |I b |, |I c |)
k
:
0
†Note: rated current is set by the setting. See Chapter Technical description: Rated
Frequency and rated current (→p. 626).
Error level
(i)
The error level has been set at level 3 (Minor error; default), but the user can change it with
setting [CHK_IZ:LVl]. Remember that the user needs to set On for setting [CHK_IZ:Sw]. The
time to detect can be changed with setting [CHK_IZ:Timer]; the default time is 15 seconds. If
the error is solved, resetting the error will be performed after the elapse of the setting time.
Error message
(ii)
When detecting error, the error message will be shown on the LCD screen. LED will be lit up.
Table 10.2-33 Error messages provided by the supervisor in CHK_IZ
Message and level
I0 error
Error level
Table 10.2-34 Detailed information in Hexadecimal in CHK_IZ
Display
area
Top
00000001: IZ error is existing
row
Middle
Calculated Max (| I
row
Bottom
Calculated Ia+Ib+Ic value
row
| I
|
+ I
+ I
− I
a
b
c
e
≥ 0.1 × Max (| I
3
Residual current of secondary CT
The largest amplitude among I a , I b and I c
5% of the rated current†
Detection of flowing the zero-sequence current
Minor error (Level 3)
Meaning of the detailed information
Left column
| , | I
| , | I
|) value
a
b
c
- 818 -
| , | I
| , | I
|) + k
a
b
c
Meaning of the information
Calculated value of |Ia+Ib+Ic-Ie|
(No information is displayed)
6F2T0207 (0.01)
(10.2-2)
0
Right column
Ie value
GRE200 (5,6)
Advertisement
