GE P742

P74
x/EN AP/Na7
Application Notes
(AP) 6
-12 MiCOM P74
1, P742, P743
AP
reinstated and after the set reset timer.
2.1.1.5 Protection options for the Check Zone
2.1.1.5.1 Options for a Circuitry Fault
To block the operation of the other zones in case of internal fault during a circuitry fault in the
Check Zone, there are 5 options:
1. Blocking Latched
An alarm is provided and this alarm can only be reset manually,
The Check Zone is blocked and this blocking can only be reset manually.
2. Alarm Latched
An alarm is provided and this alarm can only be reset manually,
The Check Zone is blocked and this blocking will be automatically reset once the
differential current will disappear and after the set reset timer.
3. Self-Reset
An alarm is provided and this alarm can only be reset manually,
The Check Zone is blocked and this blocking will be automatically reset once the
differential current will disappear and after the set reset timer.
To allow operation of the other zones in case of internal fault during a circuitry fault in the
Check Zone, there are 2 options:
1. Alarm and No blocking
An alarm is provided and this alarm can only be reset manually,
The Check Zone is not blocked
2. Alarm Self-Reset and No blocking
An alarm is provided.
The Check Zone is not blocked
2.1.1.5.2 Options for a PU error mode
To block the operation of the other zones in case of internal fault during a loss of Check
Zone, there are 3 options:
1. Blocking Latched
An alarm is provided and this alarm can only be reset manually,
The zone is blocked and this blocking can only be reset manually.
2. Alarm Latched
An alarm is provided and this alarm can only be reset manually,
The Check Zone is blocked and this blocking will be automatically reset once the
communication will be reinstated and after the set reset timer.
3. Self-Reset
An alarm is provided and the Check Zone is blocked.
The alarm and the blocking will be automatically reset once the communication will be
reinstated and after the set reset timer.
To allow the operation of the other zones in case of internal fault during a loss of Check
Zone, there are 2 more options:
1. Alarm and No blocking
An alarm is provided and this alarm can only be reset manually,
The Check Zone is not blocked
2. Alarm Self-Reset and No blocking
An alarm is provided.
The Check Zone is not blocked
2.1.1.6 Voltage criteria for busbar Protection
Where there is a need to use voltage criteria such as undervoltage, zero sequence
overvoltage, direct overvoltage or inverse undervoltage, an external device such as a P923
must be connected to the VT(s).