Toshiba GR200 Series Instruction Manual page 1108

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.
where,
Max (|Ia|, |Ib|, |Ic|):
Min (|Ia|, |Ib|, |Ic|):
k0:
Error level
(i)
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.
Error message
(ii)
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
CT error
Error level
Table 10.2-30 Detailed information in Hexadecimal in CHK_CT
Display area
N/A
Max (| I | , | I | , | I |) − 4 × Min (| I
a b c
The selection of maximum amplitude among Ia, Ib and Ic
The selection of minimum amplitude among Ia, Ib and Ic
Current multiplied a rated current by 20%
Meaning of the information
Detection of the extraordinary current flowing
Minor error (Level 3)
Meaning of the detailed information
(No information is displayed)
- 1087 -
| , | I | , | I |) ≥ k
a b c 0
6F2S1915 (0.46)
(10.2-1)
GRZ200 (Soft 031 & 032)