2.3.1 Maximum time deviation between internal clocks
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2.3.1.1 Setting the maximum time deviation
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Maximum time deviation between internal clocks is set using the MaxtDiffLevel
parameter in the respective (one to five) line differential protection IEDs. The
setting is done on the local HMI or via PCM600 (see Figure
4). Maximum time
deviation depends on:
• Jitter and wander in the telecommunication network: typically ±100-200 μs in
PDH networks and ±50 μs in SDH networks (< ±100 μs according to
telecommunication standards).
• Acceptable small asymmetric delay: typically ±50–100 μs. A constant (fixed)
asymmetric delay in the duplex channels can be adjusted by setting the
asymmetric delay on the local HMI or via the parameter setting tool (PST)
which is part of PCM600.
• Buffer memory in the telecommunication network: typically < +100 μs (buffer
memories should be avoided).
• Clock drift during two seconds: < ±100 μs.
IEC10000062 V1 EN-US
Figure 4: Setting the MaxtDiffLevel in PCM600
The setting range for MaxtDiffLevel is ±200-2000 μs, and it must be coordinated
with reference to the sensitivity of the protection function. This setting is only
relevant for echo timing.
MaxtDiffLevel is defined and measured at a sudden change in time difference
between the line ends induced by route switching. If the set value for
MaxtDiffLevel is exceeded, the protection function gets blocked. To avoid
unwanted trips produced by a number of small changes below the set value, these
small changes are summated and checked to be below MaxtDiffLevel.
Section 2 1MRK 505 382-UEN B
Telecommunication networks and line differential protection
16 Communication set-up 670/650 series 2.2
Application Guide
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