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Automatic transfer operation (ATO)
Automatic transfer operation (ATO) is the function to issue CB open and CB close commands
automatically to change the lines for power reception, when a fault has occurred at substitution.
ATO commands shall be customized depending on the lines; hence, the user can describe them
separately depending the circuit architectures.
Figure 2.27-1 shows an example about switching electric power system by the ATO commands.
The ATO sequence is shown from Step 1 to Step3:
(a) Step1: Before ATO operation
Power is fed from Source-A via Line-1, whereas another power is fed from Source-
B via Line-2.
(b) Step2: Fault occurrence on Line-1
A fault is occurring on Line-1, then CB-A is tripped. It will stop the power feeding
from Source-A.
(c) Step3: ATO action
ATO function issues CB close command to CB-T, so CB-T is closed. Accordingly,
Line-1 can receive the power from Source-B.
Source-A
Source-B
Tr-A
Tr-B
CB-A
CB-B
DS
DS
CB-T
Line-1
Line-2
(a) Step1
Figure 2.27-1 Switching electric power system by ATO operation (Examples)
The ATO function has several settings and condition points to check customized PLC logics.
Consequently, the ATO application can serve on versatile substation architectures.
Source-A
Source-B
Tr-A
Tr-B
Fault
CB-A
CB-B
DS
DS
CB-T
Line-1
Line-2
(b) Step2
- 307 -
6F2T0207 (0.01)
Source-A
Source-B
Tr-A
Tr-B
CB-A
CB-B
DS
DS
CB-T
Line-1
Line-2
(c) Step3
GRE200 (5,6)
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