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2.2.6
Transmission Data
The following data are transmitted to the remote terminal via the 64kb/s digital link. The data
depends on the communication mode and whether a function is used or not. The details are
shown in Appendix N.
A-phase current
B-phase current
C-phase current
Residual current
Positive sequence voltage
A-phase differential element output signal
B-phase differential element output signal
C-phase differential element output signal
A-phase breaker and disconnector status
B-phase breaker and disconnector status
C-phase breaker and disconnector status
Scheme switch [LOCAL TEST] status
Scheme switch [TFC] status
Reclose block command
Sampling synchronization control signal
Synchronized test trigger signal
User configurable data
Current and voltage data are instantaneous values which are sampled every 30 electrical degrees
(12 times per cycle) and consist of eleven data bits and one sign bit. This data is transmitted
every sample to the remote terminal.
Three differential element outputs and the transfer trip command are related to remote terminal
tripping and are transmitted every sampling interval.
Other data is transmitted once every power cycle.
The data transmission format and user configurable data are also shown in Appendix N.
A synchronized test trigger signal is used to test the differential protection simultaneously at all
terminals. For details, see Section 6.5.3.
In addition to the above data, cyclic redundancy check bits and fixed check bits are transmitted to
monitor the communication channel. If a channel failure is detected at the local terminal, all the
local and remote current and voltage data at that instant are set to zero and outputs of the
differential protection and out-of-step protection are blocked, and these protections of remote
terminal are also blocked because the channel failure is also detected at the remote terminal.
2.2.7
Synchronized Sampling
The GRL100 performs synchronized simultaneous sampling at all terminals of the protected
line. Two methods are applied for the sampling synchronization; intra-system synchronization
and GPS-based synchronization. The former is applied to communication modes A-MODE and
17
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