Hitachi Relion 670 Series Applications Manual page 296

Section 13
Scheme communication
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.
The principle time sequence of signaling at current reversal is shown.
Protection
Function
CS from the
protection
function, operate
and reset time
Fault Protection
occurs pick-up
IEC05000536 V2 EN-US
Figure 144:
13.4.3.2 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 2U0>.
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 (2U0) higher than the maximum false
network frequency residual voltage that can occur during normal service conditions. The
recommended minimum setting is two times the false zero-sequence voltage during normal service
conditions.
290
Tele-
Protection
Equipment
CS initiation to
the
communication
system, operate
and reset time
CR to CR to
teleprot. prot.
Fault current
CS initiation
eq. func
reversal
Time sequence of signaling at current reversal
© 2017 - 2023 Hitachi Energy. All rights reserved
Tele- Tele-
communication Protection
System Equipment
CR selection and
CS propagation,
decision, operate
propagation
and reset time
Sending CR
protection reception
reset drop
CR to
CS to
prot.
communication
func
drop
drop
Minimum setting of tDelay
1MRK506375-UEN Rev. N
Protection
Function
CR to the
protection
function, operate
and reset time
Time
IEC05000536-2-en.vsd
M13933-12 v6
Railway application RER670
Application manual