Toshiba GR 200 Series, Instruction Manual

Page: 1108 / 1563

6F2S1915 (0.46)
GRZ200 (Soft 031 & 032)
- 1087 -
10.2.14
Abnormal current flowing in CT (CT error)
The CT supervision is to examine whether the three-phase currents are balanced and the
current in zero-sequence is minimum. It secures the operation of the CT circuit. By monitoring
of the currents flowing in the AC analog input circuit, it is also applied to detect the failure in
the CT circuit. The failure is determined If Equation (10.2-1) is satisfied.
1.
Max(|I
a
|, |I
b
|, |I
c
|) − 4 × Min(|I
a
|, |I
b
|, |I
c
|) ≥ k
0
(10.2-1)
where,
Max (|Ia|, |Ib|, |Ic|): The selection of maximum amplitude among Ia, Ib and Ic
Min (|Ia|, |Ib|, |Ic|): The selection of minimum amplitude among Ia, Ib and Ic
k0:
Current multiplied a rated current by 20%
(i)
Error level
Generally, the default error level has been set at level 3 (
Minor error
), but the user can program
the level using setting [
CHK_CT:LVl
]; then, set
On
for the setting [
CHK_CT:Sw
]. The time for
the detection can be set using [
CHK_CT:Timer
], which is set for 15 seconds as default. After
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 10.2-29 Error messages provided by the supervisor in CHK_CT
Message and level Meaning of the information
CT error Detection of the extraordinary current flowing
Error level Minor error (Level 3)
Table 10.2-30 Detailed information in Hexadecimal in CHK_CT
Display area Meaning of the detailed information
N/A (No information is displayed)