transmitted on Physical Channel 1 are intended for the device connected as its Remote 1, and the eight IM64
commands transmitted on Channel 2 are intended for the device connected as its Remote 2. So, eight full-duplex
commands are available between any two terminals. Each device transmits both channels of eight IM64
commands to the connected devices. At the Remote 1 device, the eight Channel 1 IM64 commands are used
directly by the receiving device which passes through the eight Channel 2 IM64 commands to the remote 2 device.
All three devices in the scheme perform similarly, ensuring that, so long as one device is able to communicate with
the other two, scheme integrity is maintained.
This Chain topology (normally invoked when a communication link fails) can be used to save cost in a three-
terminal scheme. This is because two legs are cheaper to install than full triangulation implementation. Also if a
suitable communication link is not available between two of the line ends, it may be the only option. If a Chain
topology is used, or one link in a fully triangulated scheme is lost, the operating delay of the teleprotection
commands increases by approximately 7 ms, plus the communications channel signalling delay, due to the
extended path length and additional processing.
3.1.6
PHYSICAL CONNECTION
The protection communications into and out of the products are fibre-optic. Connections are made using BFOC/2.5
connectors (BFOC/2.5 connectors are commonly referred to as “ST” connectors where “ST” is a registered
trademark of AT&T).
According to application, different fibre-optic interfaces are available described in the following table:
Wavelength of light (nm) Fibre type Maximum transmission distance (km)
850 Multi-mode 1
1300 Multi-mode 50
1300 Single-mode 100
1550 Single-mode 150
Connections are made using appropriate fibre-optic cables terminated with BFOC/2.5 connectors. The transmitter
of one device (for example Tx1) is connected to the receiver of another (Rx1 or Rx2 according to the scheme set-
up)
Products can be supplied with the following fibre-optic channel arrangements:
Ch 1 Ch2
850 nm 850 nm
1300 nm multi-mode Not fitted
1300 nm multi-mode 1300 nm multi-mode
1300 nm single-mode Not fitted
1300 nm single-mode 1300 nm single-mode
1550 nm single-mode Not fitted
1550 nm single-mode 1550 nm single-mode
850 nm 1300 nm multi-mode
850 nm 1300 nm single-mode
850 nm 1550 nm single-mode
1300 nm multi-mode 850 nm
1300 nm single-mode 850 nm
1550 nm single-mode 850 nm
Chapter 20 - Fibre Teleprotection P543i/P545i
506 P54x1i-TM-EN-1
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