GE D90 Plus Instruction Manual page 160

DIRECT INPUTS AND OUTPUTS
Using direct inputs and outputs for interlocking busbar protection
150
Figure 124: Direct input and output settings for IED 2
The message delivery time is about 0.2 of power cycle in both ways (at 128 kbps); that is,
from device 1 to device 2, and from device 2 to device 1. Different communications cards
can be selected by the user for this back-to-back connection (for example: fiber, G.703, or
RS422).
A simple interlocking busbar protection scheme can be accomplished by sending a
blocking signal from downstream devices, say 2, 3, and 4, to the upstream device that
monitors a single incomer of the busbar, as shown below.
Figure 125: Example interlocking busbar protection scheme
For increased reliability, a dual-ring configuration (shown below) is recommended for this
application.
PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 6: COMMUNICATIONS