The IED at A2, where the forward direction element was initially activated, must reset before
the send signal is initiated from B2. The delayed reset of output signal IRVL also ensures the
send signal from IED B2 is held back till the forward direction element is reset in IED A2.
15.7.2.2
Weak-end infeed logic
M15285-6 v5
Figure
shows a typical system condition that can result in a missing operation. Note that
there is no fault current from node B. This causes that the IED at B cannot detect the fault and
trip the breaker in B. To cope with this situation, a selectable weak-end infeed logic is provided
for the permissive overreaching scheme.
A
B
IEC99000054-3-en.vsd
Strong
source
Weak
source
IEC99000054 V3 EN-US
Figure 385: Initial condition for weak-end infeed
15.7.3
Setting guidelines
IP15042-1 v1
M13933-4 v5
The parameters for the current reversal and weak-end infeed logic for residual overcurrent
protection function are set via the local HMI or PCM600.
Common base IED values for primary current (
IBase), primary voltage (UBase) and primary
power (
SBase) are set in a Global base values for settings function GBASVAL.
GlobalBaseSel: It is used to select a GBASVAL function for reference of base values.
15.7.3.1
Current reversal
M13933-6 v5
The current reversal function is set on or off by setting the parameter
CurrRev to On or Off.
Time delays shall be set for the timers
tPickUpRev and tDelayRev.
tPickUpRev is chosen shorter (<80%) than the breaker opening time, but minimum 20 ms.
tDelayRev is chosen at a minimum to the sum of protection reset time and the communication
reset time. A minimum
tDelayRev setting of 40 ms is recommended.
The reset time of the directional residual overcurrent protection (EF4PTOC) is typically 25 ms.
If other type of residual overcurrent protection is used in the remote line end, its reset time
should be used.
The signal propagation time is in the range 3 – 10 ms/km for most types of communication
media. In communication networks small additional time delays are added in multiplexers and
repeaters. Theses delays are less than 1 ms per process. It is often stated that the total
propagation time is less than 5 ms.
When a signal picks-up or drops out there is a decision time to be added. This decision time is
highly dependent on the interface between communication and protection used. In many
cases an external interface (teleprotection equipment) is used. This equipment makes a
decision and gives a binary signal to the protection device. In case of analog teleprotection
equipment typical decision time is in the range 10 – 30 ms. For digital teleprotection
equipment this time is in the range 2 – 10 ms.
If the teleprotection equipment is integrated in the protection IED the decision time can be
slightly reduced.
1MRK 505 343-UEN B
Section 15
Scheme communication
619
Application manual
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