ABB Relion 670 series - Local User Account Management; User Authorization and Role Management

of networks, different channel delay times are automatically compensated for, and
echo timing can be used. If a fixed route has specified asymmetry, this can be
compensated for by using the AsymDelay parameter.
The maximum interruption time for route switching and echo timing (for example
when a communication channel is lost) without affecting the synchronization of
internal clocks is 2 s. The protection function gets blocked for the duration of the
interruption. The 2 s time limit is derived from the stability of the internal clocks. If
route switching takes longer than that, the protection function gets blocked until the
internal clocks are re-synchronized. Proper re-synchronization of the internal
clocks takes an additional 15 seconds after the channel is restored.
From protection point-of-view, route switching interruptions should be < 50 ms
(normally route switching takes < 0.1 ms). The maximum time delay in a
telecommunication network can be set to 40 ms (default delay being 20 ms). In
echo timing mode, this time represents round-trip delay divided by two. If the
channel delay is longer than the set value, the protection function gets blocked.
The recommended value for maximum time delay when using echo
timing is 20 ms.
The protection function also gets blocked if the maximum time deviation
(MaxtDiffLevel) between the line differential protection IEDs' internal clocks is
higher than ±200-2000 μs (see Figure
3). Blocking of the function lasts until the
internal clocks' deviation reaches the set value range. Time required for new
synchronization depends on the interruption time.
Maximum transmission time
T
d
≤ 20 ms
*Depending on required sensitivity
Protection
slave
IEC07000221-1-en.vsdx
< 0.2-2 ms* difference
continuous
Protection
master
Protection
slave
A
B
C
IED
IED
IED
IEC07000221 V1 EN-US
Figure 3: Three-end application (protection master/slave)
1MRK 505 382-UEN B Section 2
Telecommunication networks and line differential protection
Communication set-up 670/650 series 2.2 15
Application Guide