ABB Relion 670 Series Applications Manual page 119

1MRK 505 370-UUS Rev. K
The IED has built-in feature to provide either self-reset or latched tripping in case of busbar protection
operation. Which type of trip signal each zone will issue is determined by a parameter setting DiffTripOut
which can be set either to SelfReset or Latched. When Latched is selected the trip output from the IED
will only reset if:
1. Manual reset command is given to the IED
2. DC power auxiliary supply to the IED is interrupted (that is, switched-off)
However, if it is required to have mechanically latched tripping and lock-out in the circuit breaker closing
circuit, then it is recommended to use one dedicated lockout IED for each bay. Such mechanical lock-out
trip IEDs are available in the COMBIFLEX range (for example RXMVB2 or RXMVB4 bistable IEDs
alternatively MG6 (hand reset contact) IEDs).
From the application point of view lock-out trip IEDs might have the following drawbacks:
• The trip contacts will remain closed. If the breaker would fail to open the tripping coil will be burnt
and the DC supply short-circuited.
• The trip circuit supervision (TCS) IEDs will reset and give alarm for a failure in the trip circuit if the
alarm is not opened by the lock-out IED or a double trip circuit supervision is recommended where
the trip circuit is supervised with two alternatively, TCS IEDs.
6.1.3.11 Contact reinforcement with heavy duty relays
There is sometimes a request for heavy duty trip relays. Normally the circuit breaker trip coils, with a
power consumption of 200 to 300 W, are provided with an auxiliary contact opening the trip circuit
immediately at breaker tripping. Therefore, no heavy duty breaking capacity is required for the tripping
relays. Nevertheless heavy duty trip relays are still often specified to ensure trip circuit opening also if the
circuit breaker fails due to a mechanical failure or a lack of energy for operation. This can particularly
occur during site testing. In this case it is recommended to use COMBIFLEX RXMH 2 or RXMVB 2 or
MG6 heavy duty relays.
6.1.3.12 Trip circuit supervision
Trip circuit supervision is mostly required to supervise the trip circuit from the individual bay IED panel to
the circuit breaker. It can be arranged also for the tripping circuits from the busbar protection.
However, it can be stated that the circuit from a busbar protection trip relay located in the busbar
protection panel is not so essential to supervise as busbar faults are very rare compared to faults in bays,
especially on overhead power lines. Also it is normally a small risk for faults in the tripping circuit and if
there is a fault which affects only one bay and all other bays are thus correctly tripped meaning that the
fault current disappears or is limited to a low value.
6.1.4 Two-zone busbar arrangements
6.1.4.1 General
Busbar differential protection application principles for typical busbar arrangements, up to two differential
zones, are shown and described in the following sections.
Busbar protection REB670
Application manual
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Section 6
Differential protection
M12120-3 v1
M12120-4 v3
M12121-3 v3
M12121-4 v3
M6640-3 v2
113