Direct Transfer Trip Dtt - ABB RED670 Product Manual

Line differential protection RED670 ANSI
Customized
Product version: 1.2
The logic can be controlled either by the autorecloser (zone
extension) or by the loss-of-load current (loss-of-load
acceleration).
Scheme communication logic for residual overcurrent
protection ECPSCH (85)
To achieve fast fault clearance of ground 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, 85) function.
Current reversal and weak-end infeed logic for residual
overcurrent protection ECRWPSCH (85)
The Current reversal and weak-end infeed logic for residual
overcurrent protection ECRWPSCH (85) is a supplement to
Scheme communication logic for residual overcurrent protection
ECPSCH (85).
To achieve fast fault clearing for all ground faults on the line, the
directional ground-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, 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
ABB
IED. To overcome these conditions, weak-end infeed (WEI)
echo logic is used.

Direct transfer trip DTT

Low active power and power factor protection LAPPGAPC
(37_55)
Low active power and power factor protection (LAPPGAPC,
37_55) function measures power flow. It can be used for
protection and monitoring of:
• phase wise low active power
• phase wise low power factor
• phase wise reactive power and apparent power as service
values
Following features are available:
• Definite time stage for low active power protection
• Definite time stage for low power factor protection
• Individual enabling of Low active power and Low power
factor functions
• Low active power trip with 2 selection modes '1 out of 3'
and '2 out of 3'
• Phase wise calculated values of apparent power, reactive
power, active power and power factor are available as
service values
• Insensitive to small variations in voltage and current
Compensated over and undervoltage protection COUVGAPC
(59_27)
Compensated over and undervoltage protection (COUVGAPC,
59_27) function calculates the remote end voltage of the
transmission line utilizing local measured voltage, current and
with the help of transmission line parameters, that is, line
resistance, reactance, capacitance and local shunt reactor. For
protection of long transmission line for in zone faults,
COUVGAPC, (59_27) can be incorporated with local criteria
within direct transfer trip logic to ensure tripping of the line only
under abnormal conditions.
Sudden change in current variation SCCVPTOC (51)
Sudden change in current variation (SCCVPTOC, 51) function is
a fast way of finding any abnormality in line currents. When
there is a fault in the system, the current changes faster than
the voltage. SCCVPTOC (51) finds abnormal condition based on
phase-to-phase current variation. The main application is as a
local criterion to increase security when transfer trips are used.
Carrier receive logic LCCRPTRC
In Direct transfer trip (DTT) scheme, the received CR signal
gives the trip to the circuit breaker after checking certain local
criteria functions in order to increase the security of the overall
tripping functionality. Carrier receive logic (LCCRPTRC, 94)
function gives final trip output of the DTT scheme.
1MRK505226-BUS D
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