In an intertrip scheme, the send signal is initiated by an underreaching zone or from an
external protection (transformer or reactor protection). At the remote end, the received
signals initiate a trip without any further protection criteria. To limit the risk for an
unwanted trip due to the spurious sending of signals, the timer tCoord should be set to
10-30 ms dependant on the type of communication channel.
The general requirement for teleprotection equipment operating in intertripping
applications is that it should be very secure and very dependable, since both inadequate
security and dependability may cause unwanted operation. In some applications the
equipment shall be able to receive while transmitting, and commands may be transmitted
over longer time period than for other teleprotection systems.
16.1.3 Setting guidelines
The parameters for the scheme communication logic function are set via the local HMI or
PCM600.
Configure the zones used for the CS send and for scheme communication tripping by
using the ACT configuration tool.
The recommended settings of tCoord timer are based on maximal recommended
transmission time for analogue channels according to IEC 60834-1. It is recommended to
coordinate the proposed settings with actual performance for the teleprotection equipment
to get optimized settings.
16.1.3.1 Blocking scheme
Set
Operation Enabled
Set
SchemeType Blocking
Set
tCoord
25 ms (10 ms + maximal transmission time)
Set
tSendMin
0 s
Set
Unblock Disabled
(Set to
NoRestart
if Unblocking scheme with no alarm for loss of guard is to be used.
Set to
Restart
if Unblocking scheme with alarm for loss of guard is to be used)
Set
tSecurity
0.035 s
16.1.3.2 Delta blocking scheme
Set
Operation
=
Enabled
Set
SchemeType
=
DeltaBlocking
Set
tCoord
= 0 s
Set
tSendMin
= 0 s
Table continues on next page
Section 16 1MRK 506 369-UUS -
Scheme communication
754 Line distance protection REL670 2.2 ANSI
Application manual
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