Power Supply Module (Including Output Relays); Power Supply Board (Including Rs485 Communication Interface); Opto Inputs Threshold Levels; Power Supply Options - GE MiCOM P40 Agile Technical Manual

P44x/EN FD/Hb6
(FD) 8-12
Nominal
battery voltage
(Vdc)
24 / 27
30 / 34
48 / 54
110 / 125
220 / 250
Table 1 – Opto inputs threshold levels
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 also has selectable filtering which can be utilised. This allows use of a pre-set
filter of ½ cycle which renders the input immune to induced noise on the wiring: although this
method is secure it can be slow, particularly for intertripping. This can be improved by
switching off the ½ cycle filter in which case one of the following methods to reduce ac noise
should be considered. The first method is to use double pole switching on the input, the
second is to use screened twisted cable on the input circuit.
2.5

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 RS485 communication
interface.
2.5.1

Power supply board (including RS485 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
24 – 48 V
48 – 110 V
110 – 250 V
Table 2 - Power supply options
The output 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, 5.1 V for all of the digital circuits, ±16 V for the analogue electronics, e.g. on the
input board, and 22 V for driving the output relay coils. All power supply voltages including
the 0 V earth line are distributed around the relay via the 64-way ribbon cable. One further
voltage level is provided by the power supply board which is the 48 V field voltage. 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 one of either Courier,
Modbus or IEC 60870-5-103 protocols. 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.
The watchdog facility provides two output relay contacts, one normally open and one
normally closed which are driven by the processor board. These are provided to give an
indication that the relay is in a healthy state.
Standard 60% - 80%
No Operation Operation
(logic 0) Vdc (logic 1) Vdc
<16.2 >19.2
<20.4 >24.0
<32.4 >38.4
<75.0 >88.0
<150.0 >176.0
MiCOM P40 Agile P442, P444
50% - 70%
No Operation
(logic 0) Vdc
<12.0
<15.0
<24.0
<55.0
<110
Nominal ac range
dc only
30 – 100 V rms
100 – 240 V rms
Firmware Design
Operation
(logic 1) Vdc
>16.8
>21.0
>33.6
>77.0
>154