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As an option this module contains two independent power supplies, with diode-auctioneered outputs for reliability pur-
poses; both supplies are powered from a dc battery voltage. The switching power supply, operating at 25 kHz, generates
transformer-isolated voltages as follows:
System
Voltage
8.5 Vdc
+12 Vdc
Analog Input Module
This module interfaces with the voltage and current transformers that are mounted on the Backplane module. These
transformers provide the following ac values: V
antialiasing filters, with a cut-off frequency determined by the Nyquist criterion and the system sampling rate. Values I
I
, I
are summed to produce 3I
B
C
All 7 inputs (V
, V
, V
, I
A
B
C
self-calibrating 12-bit (plus sign), with an internal track-and-hold amplifier. Additionally, the autoranging circuitry provides
16 bits of dynamic range needed to measure high fault current values.
Modem Module (9600 bps Audio Tone Option)
This module interconnects two REL 356 systems, located at each end of the protected line. A 4-wire communication
channel of sufficient quality to provide reliable data interchange is required. The modem, operating at a carrier frequency
of 1700 Hz, conforms to ITU V.29 standards, and provides a communication speed of 9600 bps.
The modem is under the control of an on-board digital signal processor and interfaces, via a parallel bus, with the
Microprocessor module.
The analog signals (transmit and receive levels), and digitally-encoded S/N ratio, are also available to the Microproces-
sor module. The modem transmit level is controlled by the Microprocessor module via the above-mentioned parallel bus.
Modem TXA and RXA are transmitter tone output and receiver tone input lines. TXA is 600 ohms and RXA is high
impedance. TXA will output + 5.0 Vdc for 0 dBm modem output. Modem receive input is amplified/rectified and will
output + 5.0 Vdc for a 0 dBm input. The dc output is approximately proportional to modem tone output voltage level
below 0 dBm.
There are two jumpers on the modem board, J1 and J2. These are factory set for REL356 in position (2 – 3). Position (1
– 2) is for use with REL350.
CODEC (56/64 kbps Digital Communication Option)
This module interconnects two REL 356 systems, located at each end of the protected line.
CODEC (Coder/Decoder) provides digital communication capability at 56 or 64 kbps, selectable via setting.
The CODEC is under the control of an on-board digital signal processor and interfaces via a parallel bus with the
Microprocessor module.
The two signals, TX (transmit data) and RX (receive data) interface to the Digital Communication Interface module (DCI).
Installation, Operation and Maintenance
System
Circuitry Supplied
Voltage
Processor Board
-12 Vdc
+5 Vdc Supply
Analog Circuitry
+24 Vdc
, V
A
.
0
, I
, I
, 3I
) are connected to the multiplexer and to the A/D converter. The A/D converter is a
A
B
C
0
ABB REL 356 Current Differential Protection
Circuitry Supplied
Analog circuitry
Channel Modem,
PONI Module
, V
, I
, I
, I
. These values are applied to active third-order Butterworth
B
C
A
B
C
System
Circuitry Supplied
Voltage
Channel Modem
-24 Vdc
VF Display COPS
Chips
Vacuum Fluorescent
6.5 Vac
Display Filament
,
A
2-5
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