ABB RET670 Product Manual page 21

ABB
Transformer protection RET670
Customized
Product version: 1.2
voltage apparatuses or for other user defined
functionality.
11. Scheme communication
Scheme communication logic for residual
overcurrent protection ECPSCH
To achieve fast fault clearance of earth faults on
the part of the line not covered by the
instantaneous step of the residual overcurrent
protection, the directional residual overcurrent
protection can be supported with a logic that
uses communication channels.
In the directional scheme, information of the fault
current direction must be transmitted to the other
line end. With directional comparison, a short
operate time of the protection including a channel
transmission time, can be achieved. This short
operate time enables rapid autoreclosing function
after the fault clearance.
The communication logic module for directional
residual current protection enables blocking as
well as permissive under/overreaching schemes.
The logic can also be supported by additional
logic for weak-end infeed and current reversal,
included in Current reversal and weak-end infeed
logic for residual overcurrent protection
(ECRWPSCH) function.
Current reversal and weak-end infeed logic for
residual overcurrent protection ECRWPSCH
The Current reversal and weak-end infeed logic
for residual overcurrent protection ECRWPSCH is
a supplement to Scheme communication logic for
residual overcurrent protection ECPSCH.
To achieve fast fault clearing for all earth faults on
the line, the directional earth-fault protection
function can be supported with logic that uses
communication channels.
The 670 series IEDs have for this reason available
additions to scheme communication logic.
If parallel lines are connected to common busbars
at both terminals, overreaching permissive
communication schemes can trip unselectively
due to fault current reversal. This unwanted
tripping affects the healthy line when a fault is
cleared on the other line. This lack of security can
result in a total loss of interconnection between
the two buses. To avoid this type of disturbance,
1MRK 504 117-BEN D
a fault current reversal logic (transient blocking
logic) can be used.
Permissive communication schemes for residual
overcurrent protection can basically operate only
when the protection in the remote IED can detect
the fault. The detection requires a sufficient
minimum residual fault current, out from this IED.
The fault current can be too low due to an
opened breaker or high-positive and/or zero-
sequence source impedance behind this IED. To
overcome these conditions, weak-end infeed
(WEI) echo logic is used.
12. Logic
Tripping logic SMPPTRC
A function block for protection tripping is
provided for each circuit breaker involved in the
tripping of the fault. It provides pulse prolongation
to ensure a trip pulse of sufficient length, as well
as all functionality necessary for correct co-
operation with autoreclosing functions.
The trip function block also includes functionality
for evolving faults and breaker lock-out.
Trip matrix logic TMAGGIO
Trip matrix logic TMAGGIO function is used to
route trip signals and other logical output signals
to different output contacts on the IED.
TMAGGIO output signals and the physical outputs
allows the user to adapt the signals to the
physical tripping outputs according to the specific
application needs.
Fixed signal function block
The Fixed signals function (FXDSIGN) generates a
number of pre-set (fixed) signals that can be used
in the configuration of an IED, either for forcing
the unused inputs in other function blocks to a
certain level/value, or for creating certain logic.
13. Monitoring
Measurements CVMMXN, CMMXU, VNMMXU,
VMMXU, CMSQI, VMSQI
The measurement functions are used to get on-
line information from the IED. These service
values make it possible to display on-line
information on the local HMI and on the
Substation automation system about:
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