P54x/EN OP/La4 Operation
(OP) 5-110
MiCOM P543, P544, P545 & P546
OP
ITU-T designation Description Connector pin Direction
- Case earth 1 -
G Common return 8 -
T Transmit data A 2 From P593
T Transmit data B 9 From P593
R Receive data A 4 To P593
R Receive data B 11 To P593
S Signal element timing A 6 To P593
S Signal element timing B 13 To P593
X.21 circuits supported by P593 unit
Connections of X.21 signals to the P593 unit are made via a standard male 15 way D-type
connector, wired as a DTE device. The interface cable should consist of twisted pairs of
24 AWG, overall shielded, and have a characteristic impedance of about 100 . It is
generally recommended that the interface cable shield is connected to the multiplexer frame
ground. The choice of grounding depends however on local codes and practices.
Please refer to Installation chapter for the external connection diagram.
The P54x must be set with Clock Source as ‘External’, refer to section 2.3.3.
The P593 fro
nt panel consists of four indicating LEDs and two switches.
The LED labeled ‘Supply healthy’ is green and provides indication that the unit is correctly
powered.
The LED labeled ‘Clock’ is green and provides indication that an appropriate X.21 signal
element timing signal is presented to the unit.
One of the switches is labeled ‘Fiber Optic Loopback’. This is provided to allow a test
loopback of the communication signal across the fiber optic terminals. When switched on,
the red LED labeled ‘Fiber Optic Loopback’ is illuminated.
The second switch is labeled ‘X.21 Loopback’. This is provided to allow a test loopback of
the communication signal across the X.21 terminals. It loops the incoming X.21 ‘Rx’ data
lines internally back to the outgoing X.21 ‘Tx’ data lines, and also loops the incoming fiber
optic ‘Rx’ data line (via the X.21 signal conversion circuitry) back to the outgoing fiber optic
‘Tx’ data line. When switched on, the red LED labeled ‘X.21 Loopback’ is illuminated.
2.1.12 Protection communications connection over unconditioned pilot wires
It is po
ssible to deploy P54x
on certain circuits where unconditioned 2-wire or 4-wire pilots
are available for communication. To achieve this requires a combination of P590 series
optical fiber to electrical interface units together with third-party baseband modems. The
application will be restricted by the length and quality of the pilots, with maximum pilot
lengths restricted to less than 20 km.
When considering applying a scheme based on P54x and P590 in conjunction with
baseband modems, the impact of the modem retrain time on the application needs to be
understood before making the decision. Unconditioned 2-wire and 4-wire pilots are generally
routed in proximity to the electrical power transmission and distribution feeders that they are
helping to protect. As such, they are partial to electro-magnetic interference during switching
or fault conditions on the power system. The induced interference on the pilots can cause
disruption of the communications signals, and if this is sufficient to cause the synchronization
of the communications to be lost, then the modems will have to re-synchronize, or retrain.
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