B
Control Equations & Relay Logic
SIMPRO-100
138 PRIM-2400C
B.2.4 Control Equations
After evaluating the fixed logic, the relay
evaluates the control equations, then controls the
relay output contacts. See Section B.4, page 141
for a full discussion.
B.2.5 Background Tasks
By design, there is always processing time left
after the relay controls its output contacts and
before it begins digitally filtering acquired signals
again. During this free time, the relay performs
background tasks such as:
• Self-testing
• Monitoring RTD temperature
• Storing start report, event report, and SER
records
• Responding to serial port and front-panel
commands
Figure B.1 Relay Processing Order
B.3 Relay Word Bits
The protection and control element results are
represented by Relay Word bits. Each Relay
Word bit has a label name and can be in either of
the following states:
1 (logical 1) or 0 (logical 0)
Logical 1 represents an element being picked up
or otherwise asserted. Logical 0 represents an
element being dropped out or otherwise
deasserted.
The Relay Word bits are collected into a table of
11 rows, each row containing 8 bits. The
collection is called the Relay Word. Table B.1 on
page 139 and Table B.2 on page 141 show a
complete listing of Relay Word bits and their
descriptions. The Relay Word bit row numbers
correspond to the row numbers used in the TAR
command (see Section 6.8.40, page 96).
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