Main Input Board - GE MiCOM P40 Agile Technical Manual

Firmware Design
MiCOM P40 Agile P442, P444
Up to 5 current inputs
Figure 2 - Main Input Board
The other function of the input board is to read the state of the signals present on the digital
inputs and present this to the parallel data bus for processing. The input board holds 8
optical isolators for the connection of up to eight digital input signals. The opto-isolators are
used with the digital signals for the same reason as the transformers with the analogue
signals; to isolate the relay's electronics from the power system environment. A 48 V 'field
voltage' supply is provided at the back of the relay for use in driving the digital opto-inputs.
The input board provides some hardware filtering of the digital signals to remove unwanted
noise before buffering the signals for reading on the parallel data bus. Depending on the
relay model, more than 8 digital input signals can be accepted by the relay. This is achieved
by the use of an additional opto-board which contains the same provision for 8 isolated
digital inputs as the main input board, but does not contain any of the circuits for analogue
signals which are provided on the main input board.
Each input also has selectable filtering which can be utilised.
The P440 series relays are 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. In the 'Opto Config'
menu, they can also be programmed as Standard "60% – 80%" or "50% – 70%" to satisfy
different operating constraints.
Threshold levels are as follows:
16:1
Multiplexer
Parallel bus
P44x/EN FD/Hb6
3/4 voltage inputs
Transformer board
Input board
(FD) 8-11
P3027ENa