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I.L. 40-386.3
• PT Module:
Consisting of 3 voltage transformers for V
• CT Module:
Consisting of 4 current transformers for IA, IB, IC and IP, where IP is used for zero-
sequence dual-polarizing ground current measurement.
• Filter Module:
Consisting of the anti-aliasing filters for the seven inputs from the vt and ct mod-
ules, the multiplexer to the A/D converter, the A/D converter itself, and the Opto-
isolator for the input contacts.
• Microprocessor Module:
Consisting of a microcontroller (16 bits Intel 80C196 at 10 MHz), two EPROM pro-
gram memory chips; two RAM chips, an EEPROM for data retention, a real time
clock with battery and indication LED's.
• Power Supply (PWRSUP) Module:
This is an isolated switching power supply capable of supplying +5 Vdc for micro-
controller and surrounding IC logic, ±12 Vdc for reference voltages and + 24 Vdc
for communication. All output contacts are on this module.
Three power supply options are available:
• Reclosing/Synch-check Module (optional):
consisting of an independent microcontroller (16 bits Intel 80C196) with its IC logic,
signals, contact inputs and outputs. See I.L. 40-386.11 (Version 1.11) or 40-386.12
(Version 1.1) for details.
• Man machine interface (LCD display) module (Optional):
consisting of a 2-line, 16 character per line, liquid crystal display (LCD), four
pushbuttons for setting data entries and a switch for either protection or reclosing
information.
1. 4.
UNIQUE FEATURES
1.4.1
Fault Detection Software
REL 301/302 fault-detection software operates in two modes: Background and Fault
mode.
The REL 301/302 relay normally operates in the "Background mode". During non-
fault operation (Background mode), the REL 301/302 Microprocessor checks hard-
ware, services the operator panel, and checks for a disturbances in voltage or current
which indicates a potential fault. If a disturbance is seen, the program switches to the
Fault mode, for several power cycles, to perform phase and ground unit checks for
each zone and logic functions.
The REL 301/302 relay program functions are included in a flow chart loop shown in
Figure 1-6, which the Microprocessor repeats 8 times per power cycle. Most functions
are performed all of the time, in the background mode, as shown. An important detail
(not shown in Figure 1-6) is that many of the checks are broken into small parcels, so
that the whole complement of tasks is performed over a one-cycle period (eight passes
through the loop). Some of the checks are performed more than once per cycle.
1-4
, V
and V
.
AN
BN
CN
48 Vdc
125 Vdc
250 Vdc
(10/94)
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