Table 4. Time synchronization methods supported by the relay
Methods Time-stamping resolution
SNTP (Simple Network Time Protocol)
1)
1 ms
IRIG-B (Inter-Range Instrumentation Group - Time Code Format B)
2)
4 μs
PTPv2 (IEEE 1588) with Power Profile (IEEE Std C37.238-2011)
4 μs
3)
1) Ethernet-based
2) With special time synchronization wiring
3) Required especially in process bus applications
PTPv2 features:
• Ordinary Clock with Best Master Clock algorithm
• One-step Transparent Clock for Ethernet ring topology
• PTPv2 Power Profile
• Receive (slave): 1-step/2-step
• Transmit (master): 1-step
• Layer 2 mapping
• Peer-to-peer delay calculation
• Multicast operation
The required accuracy of the grandmaster clock is +/-1 μs to
guarantee performance of protection applications. The relay
can work as a backup master clock per BMC algorithm if the
external primary grandmaster clock is not available for short
term.
In addition, the relay supports time synchronization via
Modbus, DNP3 and IEC 60870-5-103 serial communication
protocols.
Table 5. Supported station communication interfaces and protocols
Interfaces/Protocols Ethernet Serial
100BASE-TX RJ-45 100BASE-FX LC RS-485 Fiber optic ST
IEC 61850-8-1 ● ● - -
IEC 61850-9-2 LE ● ● - -
MODBUS RTU/ASCII - - ● ●
MODBUS TCP/IP ● ● - -
DNP3 (serial) - - ● ●
DNP3 TCP/IP ● ● - -
IEC 60870-5-103 - - ● ●
● = Supported
21. Protection communication and supervision
The protection communication between the relays is enabled
by means of a dedicated fiber optic communication channel;
1310 nm multimode or single-mode fibers with LC connectors
are used. The communication link transfers analog and binary
information between line ends for line differential, line distance
and transfer trip functions. No external devices, such as GPS
clocks, are needed for the line differential protection
communication. Additionally, the link can be used to transfer
any freely selectable binary data between line ends. In total, 16
binary signals can be transferred between two REX640
protection relays.
Each REX640 communication card variant contains an SFP
rack for dedicated point-to-point protection communication via
an SFP plug-in module. Three variants of SFP plug-in modules
can be selected. The variants support optical communication
for distances typically up to 2 km (multimode), 20 km (single-
mode) and 50 km (single-mode). The SFP plug-in unit can be
ordered together with the relay or later on when the need to
establish the link arises. The line differential protection can be
realized between two REX640 relays or between REX640 and
RED615 relays. If the line differential protection is to be realized
between REX640 and RED615 relays, the SFP plug-in module
has to match the RED615 communication card variant.
Additionally, the RED615 relay version must be 5.0 FP1 or later.
If a galvanic protection communication link is requested, it can
be realized with RPW600 modems. The RPW600 modem offers
a 5 kV (RMS) level of isolation between the pilot wire terminals
and ground. The RPW600 modems (master and follower) are
galvanically connected to either end of the pilot wire and
1MRS759144 A
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