This paper describes a turbine and compressor performance monitoring software program developed by Pacific Gas & Electric Company. The paper further discusses actual turbine and compressor performance and its impact on flow capacity and compressor fuel use. This performance monitoring software program is used to:
Identify compressor and turbine problems as they occur for proactive
maintenance and avoidance of larger problems
Ensure accurate transmission system hydraulic models thereby providing
accurate flow capacities to the market, optimum operations, and optimum
system expansions and modifications
Help identify general maintenance needs
Help identify serious performance degradation to justify additional repair
Identify SCADA/metering/instrumentation errors or problems
Identify excessive recycle valve operation and surge control system
Identify field changes in allowable operation that may not be communicated
back to operations and planning
Identify inefficient operations for corrective action
Once per month the program retrieves data from the gas transmission SCADA database as a basis for compressor and turbine performance monitoring. Utilizing pipeline data such as compressor unit suction and discharge pressures, gas temperatures, unit flow, ambient temperature, and other factors, the program determines actual performance measures such as turbine horsepower generated, turbine heat rate, compressor efficiency, and other factors. These performance measures are then compared to expected performance provided by manufacturer's specifications. Various graphs and tables trend the comparisons of actual vs. expected performance for a variety of performance measures. These reports are issued to the operations and maintenance departments along with a summary of recent findings on performance gaps that may merit investigation. Individual unit performance and overall average system performance are also provided. The program downloads and calculates data in an automated, user-friendly fashion. Microsoft Access is used to retrieve SCADA data and generates data tables used by the performance monitoring program. The performance monitoring software program automatically calculates all performance factors with minimal user entry and generates various performance graphs and tables. The software operates within Excel and uses Visual Basic Applications programming language.
PG&E has developed in-house, custom, operator friendly, optimization programs that recommend compressor unit operation, parallel unit discharge configuration and cross tie configuration to minimize fuel and to maximize flow capacity. (Refer to Paper 9607, Custom Optimization Program Used By Dispatchers, 1996 PSIG Conference in San Francisco and Workshop #1, Off-Line Optimization - Minimizing Fuel and Maximizing Flow Capacity for Numerous Operating and Design Scenarios, 1998 PSIG in Denver.) Utilization of these programs by the operators led to feedback that the compressors could not achieve the pressure differential predicted by the optimization programs. PG&E planning engineers investigated the operator claims and found them to be true; the turbines were generating 10-20% less pressure differential for a given flow than expected. In addition, over time some units' performance deteriorated further prompting the planning engineers to recognize the need to develop a program that would quantify and track turbine and compressor performance over time.