When a signal arrives or ends 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 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.
Below the principle time sequence of signaling at current reversal is shown.
Protection
Function
Protection
Function
Tele-
Protection
Equipment
Tele-
Protection
Equipment
Tele-
communication
System
CS from the
protection
function,
operating and
reset time
CS initiation to
the
communication
system, operating
and reset time
CS propagation,
propagation
CR selection and
decision,
operating and
reset time
CR to the
protection
function,
operating and
reset time
Time
Fault
occurs
Protection
pick-up
CS initiation
CR to
teleprot.
eq.
CR to
prot.
func
Fault current
reversal
Sending
protection
reset
CS to
communication
drop
CR
reception
drop
CR to
prot.
func
drop
Minimum setting of tDelay
en05000536.vsd
IEC05000536 V1 EN
Figure 202: Time sequence of signaling at current reversal
12.6.3.2 Weak-end infeed
The weak-end infeed can be set by setting the parameter WEI to Off, Echo or Echo &
Trip. Operating zero sequence voltage when parameter WEI is set to Echo & Trip is set
with 3V0PU.
The zero sequence voltage for a fault at the remote line end and appropriate fault resistance
is calculated.
To avoid unwanted trip from the weak-end infeed logic (if spurious signals should occur),
set the operate value of the broken delta voltage level detector (3V
0
) higher than the
1MRK 506 334-UUS A Section 12
Scheme communication
411
Application manual
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