scheider electric MiCOM P746, Technical Manual

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Firmware Design P746/EN FD/G31
MiCOM P746 (FD) 9-
11
FD
2.3.3 Universal opto isolated logic inputs
The P746 relay is fitted with universal opto isolated logic inputs that can be programmed for
the nominal battery voltage of the circuit of which they are a part. i.e. thereby allowing
different voltages for different circuits e.g. signalling, tripping. They nominally provide a Logic
1 or "ON" value for Voltages 80% of the set voltage and a Logic 0 or "OFF" value for the
voltages 60% of the set voltage. This lower value eliminates fleeting pickups that may occur
during a battery earth fault, when stray capacitance may present up to 50% of battery
voltage across an input. Each input has filtering of 7ms. This renders the input immune to
induced noise on the wiring: although this method is secure it can be slow.
In the Opto Config. menu the nominal battery voltage can be selected for all opto inputs by
selecting one of the five standard ratings in the Global Nominal V settings. If Custom is
selected then each opto input can individually be set to a nominal voltage value.
Setting Range
Menu Text Default Setting
Min. Max.
Step Size
OPTO CONFIG
Global Nominal V 48/54V
24/27V, 30/34V, 48/54V, 110/125V,
220/250V, Custom
Opto Input x 48/54V
24/27V, 30/34V, 48/54V, 110/125V,
220/250V
2.4 Power supply module (including output relays)
The power supply module contains two PCBs, one for the power supply unit itself and the
other for the output relays. The power supply board also contains the input and output
hardware for the rear communication port which provides an EIA(RS)485 communication
interface.
2.5 Power supply board (including EIA(RS)485 communication interface)
One of three different configurations of the power supply board can be fitted to the relay.
This will be specified at the time of order and depends on the nature of the supply voltage
that will be connected to the relay. The three options are shown in table 1 below:
Nominal dc Range Nominal ac Range
24/54 V DC only
48/125 V 30/100 Vrms
110/250 V 100/240 Vrms
Table 1: Power supply options
The outputs from all versions of the power supply module are used to provide isolated power
supply rails to all of the other modules within the relay. Three voltage levels are used within
the relay, 5.1V for all of the digital circuits, 16V for the analogue electronics, e.g. on the
input board, and 22V for driving the output relay coils and communication boards 3.3V power
supply (through on board DC-DC converter).
All power supply voltages including the 0V ground line are distributed around the relay via
the 64-way ribbon cables. One further voltage level is provided by the power supply board
which is the field voltage of 48V. This is brought out to terminals on the back of the relay so
that it can be used to drive the optically isolated digital inputs.
The two other functions provided by the power supply board are the RS485 communications
interface and the watchdog contacts for the relay. The RS485 interface is used with the
relay’s rear communication port to provide communication using K Bus Courier. The RS485
hardware supports half-duplex communication and provides optical isolation of the serial
data being transmitted and received.
All internal communication of data from the power supply board is conducted via the output
relay board which is connected to the parallel bus.