Energy & Power Generation Consulting,
Engineering & Management Services



PROJECT: State Prison Solar Turbines (2) Maintenance Services

This State Prison was a facility that has two 3.0 MW Centaur 40 Solar Turbines with each turbine exhausting heat into its own Heat Recovery Steam Generator (HRSG). Steam produced from the HRSG was used for facility heating, laundry cleaning, kitchen dish washing, and food preparation. The facility has a central power house that also serves as the electrical distribution hub for switchgear control between the two gas turbine/generators, local utility power, and four additional high voltage load feeder breakers.

Three years prior (at the end of 2004), The State completed a major turbine, turbine controls, and facility control system upgrade. The goal of the 2004 project was to fully automate the dispatching of the two gas turbine/generators based on facility loads such that the local utility power consumption was held at a fixed operator set point of approximately 300 kW. The operator would select the lead/lag assignment between the two turbines and the automatic controls would start/stop the lag turbine based on the facilities change in load demand always attempting to maintain 300 kW of "import" power from the local utility power source.

Engineering services were required to resolve instabilities resulting from the automatic controls not correctly controlling the gas turbines. The State was unsuccessful at forcing the original contractor to resolve final commissioning instabilities in the 2004 upgrade project.

The primary load and switchgear breaker control system logic was performed in PLC style controllers supplied by ENCORP. The Solar Turbine logic was resident in Allen-Bradley PLC-5's and obtained direct on/off digital commands and an analog kW set point from the ENCORP PLC's.

The engineering services successfully diagnosed numerous tedious logic errors, incorrect tuning values, and design flaws that all contributed to, at times, very severe load instabilities. Prior to these improvements, the units always ran in manual with the operator performing all load changes through 15 minute periodic inspections of the facility load requirements. Now the units run in full automatic and the site operators have stated they have never seen this good a performance in the machines since their original commissioning.


• Used the A/B RSLogix 5 & Emulate 5 to model the software lockup problems found in the gas turbine control ladder logic. Found and corrected numeous software design issues resulting from improper PID control and over-ride logic.

• Performed a complete performance evaluation of the site's Allen-Bradley PLC-5 ControlNet version 1.25 communication with the 1794 Flex I/O modules due to a suspicion of corrupted module configurations in the PLC-5/40C processor.

• Constructed a full Siemens APOGEE modular building automation panel as a bench test system. Conducted programming development work using DataMate Base to determine viability of the addition of process input alarm functions for an annunciator.

• Completed a study of the functional logic for load shedding existing within a problematic design, built a complete bench test system including real world simulation, and redesigned the logic to meet the site's load shedding requirements.