Control Circuits; Communications Circuits; Jumper Selection - Schweitzer Engineering Laboratories SEL-267D Instruction Manual

CONTROL CIRCUITS

The control inputs are dry. To assert the 52A input, control voltage must be applied to the
52A input terminals. Each input is individually isolated, and a terminal pair is brought out
for each input. There are no internal connections between control inputs.
Control outputs are dry relay contacts rated for tripping duty. Each contact is protected by a
metal-oxide varistor.

COMMUNICATIONS CIRCUITS

Connections to the two EIA RS-232-C serial communications ports are made via the two
nine-pin connectors labeled PORT 1 and PORT 2R on the rear panel and PORT 2F on the
front panel. Pins 5 and 9 connect directly to frame (chassis) ground. These connections
should not be relied upon for safety grounding, since their current-carrying capacity is
less than control-power short-circuit current and protection levels.
The communications circuits are protected by low-energy, low-voltage MOVs and passive RC
filters. Communications circuit difficulties can be minimized by keeping the length of the
EIA RS-232-C cables as short as possible. Lengths of 12 feet or less are recommended; in no
case should the cable length exceed 100 feet. SEL recommends shielded communications
cable for lengths in excess of 10 feet. Modems are required for communications over long
distances.
Route the communications cables well away from the secondary and control circuits. Do not
bundle the communications wiring with secondary or control circuit wiring. Noise could be
coupled into the communications wiring from the control or secondary wiring. This noise
could exceed the communications logic thresholds, introducing communications errors. The
IRIG-B clock cable should also be routed away from control wiring and secondary circuits.

JUMPER SELECTION

All jumpers are located on the front edge of the main board. They are easily accessed by
removing the top cover or pulling the drawout assembly out from the front.
5-2 Installation
SEL-267D Instruction Manual
Date Code 920326