By Douglas J. Smith, IEng, Senior Editor
Utilities and Original equipment manufacturers are beginning to “see” benefits from remote Monitoring and Diagnostics.
Utility companies are continually looking at ways to reduce the operations and maintenance costs of their power plants. According to Tim Holtan, senior business analyst, SmartSignal Corporation, the solution might be found in condition monitoring. Condition monitoring provides early warning of deteriorating equipment conditions before they result in a catastrophic failure, Figure 1.
With recent developments in diagnostics and communication technology, it is now possible for electric utilities to monitor and analyze operating data on all of their plants, remotely, from a centralized monitoring and diagnostic center. The aim of these centers is to improve system wide performance, decrease maintenance costs and lower outage rates. Using data historians for real-time data feeds and visualization, combined with predictive condition monitoring technology for early detection of problems, power plant owners can rely on information from monitoring and diagnostic centers to implement proactive maintenance strategies.
Many power plant equipment OEMs are also utilizing remote monitoring centers. OEMs use these centers to improve customer service, pre-empt possible machine trips and collect feedback on the operations of their equipment.
Water Chemistry Control
Water chemistry control is a major concern for all electric utilities. If water chemistry is not controlled, it can cause corrosion-related failures and reduce energy conversion efficiency. A leading factor of unplanned outages is inadequate control of water treatment. With older power plants, proper water chemistry control may be the only way the plant can operate economically. Advanced simulation tools and diagnostic systems are now being used to remotely monitor and diagnose water chemistry problems.
In recent years iSagacity, Inc., Half Moon Bay, California, has developed a web-based monitoring and diagnostic system for water chemistry and performance monitoring at electric power plants. According to Peter Millett, founder and CEO, iSagacity, the technology can be managed remotely at a central monitoring center or it can be installed on a utility’s intranet. The technology is able to interface with a variety of plant data sources including data historians, SCADA and distributed control systems.
A typical system could have 100 or more sample points (with a sample rate of once/minute), several months of on-line data storage, and long-term storage of minimum, maximum and average data. “Remote Manager,” an internet-based management tool utilizing a secure web site hosted in iSagacity’s California Data Center, is used to access the plant’s data. The Remote Manager performs basic statistical tests to help in identifying key trends on all incoming data. A data view page on the website allows any authorized user to create trend plots of historical data. Multiple parameters can be viewed on a single screen and, if needed, saved for future analysis.
According to Millett, a key feature of their technology is the pattern recognition technique used to diagnose the data. This approach can use a mathematical model, a simulator of the process or a library of patterns of data of operational events or scenarios. In addition, the model can be used to generate “fingerprints” of equipment operations under abnormal condition. By creating a set of fingerprints, or scenarios of the plant, it is possible for the system to simulate and track a fault condition.
In a joint venture with Nalco Company, iSagacity is installing a remote monitoring and diagnostic system (remote manager) at Portland General Electric’s Coyote Springs Unit 1, a 250 MW gas fired combined-cycle plant that went into operation in November 1995.
When completed, the remote manager will monitor the water chemistry of the heat recovery steam generator (HRSG) and cooling tower, Figure 2. The HRSG portion is currently being tested prior to being put into commercial operation. In addition to access by the plant personnel and iSagacity, Nalco will receive all alerts from the system when the performance has degraded or an abnormal condition is identified. Nalco and iSagacity will use this information to recommend corrective action for optimizing the plant’s water chemistry program.
OEM Remote Monitoring Centers
In early 2001, Sermatech Power Solutions opened its monitoring and diagnostic center in Orlando, Florida. The center was designed for remote on-line monitoring and diagnostics, analyzing plant modifications and upgrades, and providing support for gas turbine users. The center is staffed with gas turbine, generator and steam turbine engineers. The center includes “Tiger” gas turbine monitoring system software which allows Sermatech and its clients to track the operating conditions of turbomachinary units in real time. The Tiger software collects data from the turbine’s control system and analyzes the data to determine if there are any anomalies or other operating problems. When an operating problem is detected, all of the data is stored.
The stored data can be used to review significant events and compare data for rundown times and/or critical operating temperatures and pressures before a shutdown or after an overhaul. A machine baseline can be set up. After an overhaul the machine’s operating characteristics can be compared with the previous baseline data.
Electric utilities can have Sermatech monitor their equipment 24/7 or daily. When monitoring on a daily basis, the performance monitoring and diagnostic center downloads and reviews the data once/day. The data is coded with different colors for critical reports, fault indicators, warnings, turbine events and turbine operations. Trending of data, either on-line or from stored historical data, allows past data and baseline data to be compared to current operating information.
After analyzing the data for trends, operational characteristics, performance and potential problems, the information is then available to Sermatech and plant operations and engineering staff. Using this information Sermatech has the ability to resolve problems before they occur. They are also able to prevent trips, determine faulty instrumentation and make software changes. All of this can be done without sending engineers out to the plant(s).
Before being acquired by Siemens, Westinghouse was remotely monitoring steam turbines and generators from a monitoring and diagnostic (M&D) center in their Orlando facility. Today, Siemens Power Generation and its legal entity Westinghouse Power Corporation have two M&D centers: One in Orlando and the other in Erlangen, Germany. The two centers together monitor more than 130 units worldwide.
The aim is to provide plant operating data to Siemens for analysis by advanced diagnostics tools, experts and engineers to ensure optimum operation and performance of the customer’s plant, Figure 3.
The M&D centers use multiple data acquisition tools for remotely obtaining operational data from gas turbines, steam turbines, generators and balance of plant. According to Siemens Westinghouse the primary tool used for data acquisition is WIN_TS, a PC based tool that is passively connected to the power plant’s instrument and control system. This data acquisition system does not affect plant operation functions or control system settings.
During plant operations selected signals from the plant’s distributed control system are transferred, analyzed and stored in the WIN_TS computer at the plant. The data can be transmitted in real-time when an event or anomaly is detected. Several screens that display temperatures, pressures, vibration and other operating data can be viewed in real-time by the M&D staff. The power plant staff is also able to analyze the data. Figure 4 is a typical screen.
At the plant the WIN_TS computer has several modules to monitor key parameters of the gas turbine and other plant equipment. These include outlet temperature profile, turbine vibration, peak starting temperature, bearing condition and other plant parameters. The goal is to detect hardware damage, performance or operational anomalies before they become more severe and result in an unplanned outage or serious plant damage. Module alarm limits are customized for each unit being monitored.
Once the data is transmitted to the M&D center it is processed and analyzed through a series of advanced models and AI (artificial intelligence) software. The results are posted on the computer where it can be accessed by the center’s monitoring and diagnostic team for further engineering analysis and reference for that particular unit.
Should an alarm on the WIN_TS indicate a serious problem, a “Watchdog File” is automatically transferred to the appropriate M&D center. This file will contain a snapshot of data such as temperatures and pressure measurements that can be quickly analyzed by the center’s engineers and compared to expected operating conditions. Siemens would notify the plant of the condition and make recommendations as to what actions the plant should take.
Using their M&D centers, Siemens Westinghouse was able to diagnose a broken tooth on a step down gear between a gas turbine and generator. In another plant they determined that high-frequency air oscillations in the differential pressure switches of a gas turbine compressor were caused by the plant’s control system. Over the last 15 years the company has prevented extensive damage to generators. These included detecting:
- Fatigue cracks of the copper strands in the stator end windings of a gas-cooled generator
- Hydrogen leaks in hydrogen cooled generators
Siemens has seen a growing market demand of what they call total plant solutions. To address this demand, the scope of monitoring and diagnostics is expanding to not only monitor major equipment but also the balance of plant equipment. A recent Siemens contract includes the remote monitoring and diagnostic analysis of electric equipment and instrumentation and controls.
Other OEMs, including Bently Nevada, a GE Energy business, and Mitsubishi Power Systems, also remotely monitor and diagnose power plant equipment. A recent Bently Nevada project is the networking and remote monitoring of Iberdrola Generacion’s worldwide combined-cycle power plants. When completed the plants will be monitored from an M&D center in Spain.
Mitsubishi Power Systems’ remote monitoring center is located at their Orlando Service Center. The center supports customers through real-time acquisition and monitoring of turbine operating data. The data is collected via a secure internet connection to the customer’s host supervisory or control system. In addition to real-time monitoring and troubleshooting the center is able to analyze and evaluate and trend gas turbine performance over a period of time.
Gary Conkright, president, SmartSystems, says that the growth of M&D centers has been spurred by electric utilities looking to improve system-wide performance, decrease maintenance costs and lower unscheduled outages. Monitoring and diagnosing data over a period of time allows power plants to trend the operation of equipment and predict and detect operating problems before they happen, thus allowing them to take proactive and not reactive maintenance.