The first ControlNet network system
installation in eastern Washington was part of the control system
renovation at Washington Water Power's (Avista Utilities) Kettle Falls generating station.
The ControlNet system, a new high speed "producer/consumer" local area
network for production facilities, was designed by Programmable Control
Services, Inc., the control system integrator for the renovation project.
The 15-year-old control system at the Kettle Falls generating station had
become a serious problem for Washington Water Power (Avista), and its renovation
presented several challenges.
The existing system was not fully documented since the PLC program was
written prior to the advent of documentation systems. Some of the I/O was
wired with "hot leg" switching and some with "neutral leg" switching. The
program and hardware had been modified several times since 1982, again
without proper documentation. The generating station's control system
consisted of over 1,000 input/output (I/O) points. The manufacturer of the
original PLCs was unable to furnish support and spare parts for the I/O
system. A requirement for the renovation was that the start-up and
commissioning had to be accomplished within a 24 hour period with no
allowable deviation from this requirement.
To accomplish start-up and commissioning
within 24 hours, PCS provided new I/O elementary drawings which
cross-referenced old and new wire numbers and terminal numbers. Back
panels were prefabricated and wired in PCS's shop.
An Allen-Bradley PLC-5/40C programmable
controller replaced three obsolete PLCs. An existing Windows-based
operator interface PC was reused by re-addressing, installing a new
ControlNet card and using WinLinx driver software by Rockwell Software.
Washington Water Power (Avista) technicians mounted the new back panels in existing
enclosures and terminated the pre-labeled wires and bundles on the existing
I/O terminal blocks. The field wiring required no changes. The old PLC
programs were converted so that the system control was exactly the same as
before the conversion.
Having been given an absolute time frame
of 24 hours for the entire start-up procedure, Washington Water Power (Avista)
personnel along with PCS engineers accomplished it in just four hours.
