GE Remote Services

 

Abstract

As deregulation becomes a reality for the power generation industry and as competitive power production becomes standard operating procedure, the quality of power a company produces becomes the measure of its success. This requires the utility, independent power producer (IPP), and/or industrial power producer to bid power competitively at current market rates. The power producer that operates at the lowest cost per kilowatt-hour will thrive in this challenging environment.

 

GE Power Systems and its Energy Services business offer an abundance of products aimed at increasing the availability and reducing the cost of plant operation. These include long-term service agreements (LTSA); operation and maintenance (O&M) contracts; inventory-management programs; life-extension services; refurbished turbine parts offerings; and remote services (RS), an integrated management tool that helps customers meet their plant life-cycle objectives. This paper is focused on new developments in RS over the past four years.

 

Introduction

Increasing competition has caused power plants to switch from traditional time-based maintenance strategies to those based on a plantÕs operating condition. In order to stay competitive, power producers such as utilities, IPPs and industrials have focused their efforts on improving the availability of plant equipment, reducing maintenance costs and becoming the lowest- cost producer. To meet this need, GEÕs Monitoring and Diagnostic Center (M&DC) developed RS, which provides real-time data assessments and recommendations from remote locations to improve the availability and performance of equipment, systems and plants. The main elements of the RS process are monitoring and communication, on-site data acquisition and monitoring system, and communication vehicles such as the satellite, the Internet, the telephone and the LAN.

 

GE has designed, manufactured or commissioned more than 50% of the worldÕs installed base of power generation equipment and maintains the largest field sales and service workforce in the industry. The M&DCÕs RS strategy combines GEÕs considerable practical experience in O&M with the M&DCÕs expertise in remote diagnostics gained through the deployment of over 150 units with RS features. This allows customers to respond quickly to a rapidly changing environment by extending the intervals between maintenance outages, reducing the duration of scheduled outages, maximizing plant performance, predicting life cycles, optimizing plant output, reducing unplanned outage events and managing the timing of those which do occur, as well as providing operating recommendations that maximize the revenue stream and decrease plant life-cycle costs. The critical components of RS and their functions are:

 

On-site data acquisition and monitoring system

Communication vehicles such as the satellite, the Internet, telephone and the LAN

 

Measurement and analysis of equipment condition and performance

Comparison of conditions to fleet and equipment baselines, design specification and experience

Communication of relevant data to the M&DC

 

Identification and isolation of problems

Root-cause analysis and experience-based learning

Problem reporting and corrective action recommendation

Data archiving and unit/fleet analysis

 

A broad range of service modules are available to cover equipment at component, system or plant level.

 

(Telediagnostics) gas turbine generator health report

(GTD) gas turbine diagnostics

(GD) generator diagnostics

(Enter) online heat balance analysis.

 

GE Energy ServicesÕ RS Solution

GEÕs RS solution provides the ability to collect, validate and analyze operational data from a customerÕs equipment. Operational data is reviewed at different frequencies, depending on the RS modules supplied. The review can take place on an as-needed or a continuous basis. Concurrent analysis is performed on site in real time and at the M&DC. This methodology is designed to identify operating anomalies (symptoms and/or indications) or incipient problems and, thus, provide validated solutions. If an anomaly is detected on site, the system automatically notifies diagnostic specialists at the M&DC. Figure 1 outlines the design, organizational structure and functionality of the M&DC.

Diagnostic specialists are able to connect to equipment remotely to examine its operation and performance or investigate the nature of a problem in addition to providing online site consulting to customers. When warranted, the diagnostic specialist is able to generate recommendations on plant operations and/or maintenance actions. The recommendations are designed to maximize the equipment's performance, reliability and availability and, potentially, extend its outage interval cycle. This process is designed to occur as a complement to normal plant operating procedures and will allow the plant manager and operator to use GE's RS as a resource for better-informed and, thus, higher-quality maintenance and operating decisions.

 

The monitoring and diagnostic system (MDS) architecture provides networking among a site   component (referred to as the on-site monitor, or OSM), the M&DC, GE expert engineers and a data communication component (Figure 2).  

 

 

Plant Monitoring and Diagnostics Concept and Architecture

The concept of a remote monitoring and diagnostic (M&D) service that provides ready access to operating data, transmits it to a central location, performs diagnostic evaluation through a combination of automation and experts, and reports on a plantÕs operating condition has existed for some time. Numerous technical papers have been written about monitoring and diagnostics, each of which is specific in nature and often deals with a single issue such as vibration or performance of a single piece of equipment.

 

Very few publications describe a detailed approach to monitoring a fleet of similar machines with variable features. This paper should fill that void by describing various technologies that were developed over the past decade for monitoring such a fleet. A power plant fleet consists of gas turbines, steam turbines, generators and balance of plant (BOP). The infrastructure needed to diagnose an entire range of issues that affect a fleet of turbines is presented here, and only examples of only GEÕs gas turbine fleet will be cited to reduce the paper's scope.

 

Figure 3 provides a pictorial summary of the remote fleet-monitoring concept. Two functional components, an MDS and a central M&DC, monitor a fleet of turbines. The MDS consists of an OSM; a computer that logs data from the power plantÕs control system; various telecommunication technologies; and a network of computer systems, located at a central M&DC, that archive fleet operating data and perform diagnostics and reporting functions. The OSM measures and analyzes large amounts of data, detects anomalous conditions and then transmits information to the M&DC for further analysis on the condition of equipment; compares conditions to equipment baselines, design specifications and experience; and communicates the relevant information to customer personal.    

 

 

The M&DC can additionally interpret fleet data and provide advice to the remote operators regarding plant operations as and when needed. This includes commissioning and startup support, optimizing plant operations and critical shutdown scenarios that are not handled by the plant control systems. The M&DC performs these functions by using modules (querying and archiving the data periodically), trend analysis, problem identification and isolation, root-cause analysis and experience-based learning, problem reporting, and recommendations for corrective action.

 

Although a variety of equipment needs to be monitored, the principles of M&D are similar and common tools and processes are used where practical. Special and highly engineered software is also used to detect unique anomalies and aids the diagnostic team in reporting and recommendations. GEÕs Energy Services M&DC is a single M&DC monitoring different types of turbomachinery applications. It is located in Atlanta, GA.

 

A simple diagram of the remote monitoring and diagnostics (M&D) concept of regularly transferring operational data to determine the current operating condition of a plant is depicted in Figure 4. All operational data collected is validated through advanced mathematical algorithms before it is used. Transient and steadystate (startup, shutdown, load-change) data are utilized in problem diagnosis. Also, past and current data and relevant baselines are utilized in discovering operational anomalies, which are detected on the OSM and at the M&DC. Anomalies detected on the OSM are usually operational or unusual equipment problems that have not been detected by the control system and require immediate attention by the M&DC. Thus, detection of a first-level deviation is performed on site by the OSM. Detection of anomalies that develop over several hours or days is performed at the M&DC. Methods and approaches for detecting anomalies include the following:

 

Many of the well-understood root-cause algorithms have been catalogued and automated using advanced mathematical and computational techniques to resolve operational problems quickly. Root-cause assessments of all operational anomalies, deviations in performance and abnormalities in maintenance condition are used as a basis for determining whether operational and maintenance recommendations are required.

 

Trend monitoring is performed at the M&DC to identify long-term deviations in condition and performance. This provides a means to highlight and detect emerging problems well in advance of actual failures and identify subtle deviations in performance that may be indicators of emerging problems. Thus, although mature anomaly-detection algorithms are deployed on the OSM, when necessary, more detailed root-cause analyses and diagnostic functions are performed by experts at the M&DC.

 

The M&D Viewer

Many specialists and engineers employ the M&D systemÕs user interface to display archived operational data for diagnostic assessments and associated preliminary recommendations. It manages periodic assessment functions, performs selected assessments on demand, carries out hypothetical assessments, conducts remote OSM administrative functions and displays real time operational data (up to a one-secondupdate rate).

 

A variety of on-site and remote clients use the M&D viewer to access diagnostic results and operational data. A flexible and open system with Internet data access capabilities is provided to satisfy this need.

 

Diagnostics Functionality

The M&D system provides detection, notification and diagnoses of automated and manual anomalies to assist the diagnostic specialist in making assessments and determining operational and maintenance recommendations.

 

Validated Sensor Data

All operational data collected is validated by thresholding and cross checking, as appropriate. The validation is complementary to but more detailed than the range checking carried    out on the OSM. Support is provided for both transient and steady-state operating conditions. Transient conditions include startup, shutdown and load change. In steady-state operations, trending and rate-of-change monitoring is provided. Invalid sensor data would be flagged and highlighted in any analysis or report.

 

Trend Unit Health and Performance

The trending of equipment and system health and performance is accomplished by using operational data collected from the OSM as well as historical operating data. The operational data includes monitored sensors (pressure and temperature) as well as derived sensors (enthalpy). Manual entry of operational observations (e.g., visual, NDE, meteorological) will be recorded as needed.

 

Assessment of a unit's health and performance calculations (e.g., its efficiency and thermal performance) is carried out periodically to track the condition of each monitored unit over time and to build up its health and performance history. All performance data and results are normalized to ISO conditions as appropriate to facilitate comparison of unit-specific data over time. This will also facilitate comparisons between similar units and comparison of unit data to design specifications.

 

Detection of Anomalies

The M&D system utilizes a unitÕs current and historical health and performance data and applicable baseline data to detect anomalies (e.g., higher-than-expected vibration levels or significant deviation in performance from what is expected). Detection of an anomaly is composed of two components: real-time assessment within the OSM (minutes to hours) and data evaluation over an extended time frame (12 hours or more).

 

 

The relevant baselines to be used as benchmarks include the historical performance of the unit, fleet averages for similar units and the design-specification performance of the given unit and its subcomponents. Maintenance and operation logs will be consulted (Figure 4).

 

Root-Cause Analysis

Root-cause analysis is aided by an automated diagnostic system that includes cause-and-effect knowledge of equipment-specific failure, equipment design knowledge, past problem/solution information and the site-specific configuration. Its key purpose is to provide the necessary technical input for determining appropriate maintenance or operating recommendations.

 

Once a problem is defined, its root cause must be determined. To do that, a cause-and-effect diagram is constructed that relates each problem to its underlying cause. It also shows the hierarchical nature of the process because problems often have causes that can themselves be considered problems with causes. Take, for example, a low turbine efficiency that is caused by low compressor efficiency that is caused by aerodynamic losses due to deposits.

 

Recommendations for Operators

The M&D specialists and diagnostic engineers develop short-term operation recommendations (such as Run at reduced power levels or Adjust operating settings) and long-term data-collection or maintenance recommendations (such as Plan for a shutdown within two weeks to further assess the unitÕs condition or Perform a gas turbine water wash on-line or off-line) as appropriate to a unit's health anomalies. The diagnostics engineer will also consider measures that can be taken while a unit is operating (e.g., on-line against off-line actions).

 

The M&D diagnostic engineer will, upon determination of a problem, provide recommendations for avoiding unplanned outages, minimizing possible secondary damage, enhancing the reliability and availability of the units, maintaining the intended level of performance and optimizing unit performance.

 

Product Functionality

 Although power plant rotating machines are carefully designed with high levels of safety and exceptional performance, operating flaws can still occur. The M&D system has been designed to predict these deviations and provide recommendations so operators can prevent serious failures or deviations from peak performance. Typical evaluations that the M&D system is able to make on the steam turbine, gas turbine and generator are listed below.

 

Steam Turbine, Gas Turbine and Generator Assessment:

Monitoring turbine and generator performance parameters (baseline predictions) Detecting performance deviations

Discovering and identifying causes of performance problems early on

Rotor train vibration monitoring

Remote access analysis programs

Engineering-advised vibration diagnostics

 

The OSM

The OSM is an assembly of electronic components that incorporate microprocessor technology. It is designed and fabricated to perform integrated monitoring, data analysis and communication to a centralized M&D data server. The OSM is installed on site and receives data from plant systems.

 

Primary OSM functions are acquisition of operational data from plant equipment, performance of anomaly detection for deviations from baseline and buffering the data for subsequent transmission to the M&DC.

 

The OSM can interface with various devices (e.g., the unit control system, DCS and thirdparty systems) and collect operational data from them. In addition, it will perform analysis on the data, provide temporary storage of operational data and communicate data remotely. The OSM provides a first level of anomaly detection and notification, which alerts on-site personnel and the M&DC to developing problems or potential issues. The OSM allows the diagnostic specialist remote access to the customerÕs equipment to allow real-time viewing of the operating data.

 

The OSM's functions are performed independently. Data collection, processing and buffering, deviation detection and notification are performed as needed for the unit-monitored equipment. Detected events and trips will not impair the OSM's real-time data-collection performance, nor will M&DC or engineering-initiated interactions and local-user-initiated interactions.

 

A calculation engine aboard the OSM uses high-fidelity data to produce calculations of the equipmentÕs operating mode, performance, vibration and equipment-specific parameters. Within its architecture is an action engine that can trigger remote notification when anomalies are detected.

 

A single OSM can monitor multiple pieces of equipment installed at a plant site. The OSM software is standardized but highly configurable so that together with the flexible data interfaces, the OSM can be tailored to the needs of the site-specific installation to be monitored. The OSM also provides local and remote capability for RS system configuration. In addition to providing notification of an anomaly, the OSM is an Internet interface that provides on-line access to selected portions of the operating data archives.

 

Gas Turbine Diagnostics Module (GTDM)

The GTDM is a monitoring strategy that focuses on specific equipment behaviors and monitors them on a nearly continuous basis. Failure modes are detected and managed through an OSM and M&DC experience procedures. Specifically, avoiding gas turbine rotor and combustion operation issues have been key to assuring that customers maximize turbine run times. M&D specialists and M&D engineering work closely to understand the plant operating characteristics by monitoring vibration and combustion parameters. Plant operation is then understood by using these data profiles, and a monitoring strategy is developed with techniques and software to detect gas turbine rotor or combustion anomalies.

 

Gas Turbine Generator Health Report (GTHR)

The GTHR is a monitoring and diagnosis module that allows the customer to send stored data to the M&DC for analysis and interpretation. A modem connection lets GE's diagnostic specialists view the plant in real time for collaborative troubleshooting. Up to 14 different systems can be monitored, depending on a unit's complexity and a customerÕs needs, resulting in a description of trends and abnormalities as well as recommendations for corrective action.

 

The GTHR module automatically records data from the three-hour period before a trip, startup or shutdown. Next, this data can be sent to the M&DC by way of modem for analysis. Data files are transmitted to the M&DC each month, leading to generation of reports that provide an overview of the plant's health and recommendations for O&M.

 

The GTHR determines aspects of plant performance such as turbine performance and compressor efficiency, which can be used to schedule water washes. The monthly data analysis allows a GE diagnostic specialist to detect deviation from normal behavior and to prescribe corrective action.

 

Generator Diagnostics Module (GDM)

The GDM is a generator-monitoring module that detects developing problems and utilizes structured analysis processes and engineering experience to provide detailed diagnoses and real-time operational recommendations for corrective action. The recommendations are based on the monitoring of all relevant data, which is analyzed by the GDMÕs expert knowledge base and checked by generator engineers. Its dynamic tracking capabilities allow the GDM to detect incipient problems as they develop, often long before alarm conditions are reached. If followed, these recommendations will help the customer avoid generator-operating conditions that could cause damage to the equipment. The diagnosis also will assist maintenance and outage planning, and the GDMÕs information will help the customer to assess a unit's condition and plan future operation accordingly.

 

The GDM is a highly capable module. It monitors eight generator subsystems: core, excitation, hydrogen cooling, lubricating oil, seal oil, rotor, stator and stator water cooling. Within each of these subsystems are numerous specific diagnoses; some examples are high core-end temperature, overfluxing core, reduced hydrogen cooler efficiency, blocked lubricating oil flow, rotor shorted turns, rotor winding ventilation problems, seal oil vacuum treatment malfunction, fouled or plugged stator bar coolant path or high stator cooling-water conductivity.

 

The GDM provides multimode diagnostics under the following operating conditions: turning gear, run up, full-speed, no-load and no excitation, normal-loaded, run down. It performs online sensor data trending and displays information on multiple Internet screens.

 

On-line Heat Balance Analysis Module (HBM)

The HBM uses EfficiencyMapª, GEÕs power plant optimization and performance-monitoring software. It assists the plant's operational staff in predicting the most profitable way to run the plant and measuring and tracking changes in plant performance. The HBM tells operators where to set controllable parameters to maximize profitability. It reduces degradation to 0.5% per year, and it also identifies sensors with poor accuracy and retrieves and shows results quickly.

 

The HBM has many useful features. It optimizes plant operation to maximize profitability while evaluating performance and determining degradation, validates measurements using model-based plant mass and energy balances and acquires real-time measurements, and archives data for easy retrieval and viewing.

 

Diagnostics Engineering Team

The diagnostics engineering team provides additional customer contact for technical support on combustion, mechanical, electrical, performance, vibration, systems and controls expertise. It provides consistent, high-quality responses to customers' queries and is available seven days a week, 24 hours a day. The technical advice structure allows it to direct O&M questions rapidly to the proper GE engineer. When the GE engineer receives a question, a case documenting the situation is opened. The diagnostics engineering commitment tracking system allows for team utilization of the case as a problem- solving vehicle. The case is recorded in the technical advice database as a part of the site history and equipment profile.

 

There are three tools that help the diagnostics engineering team provide quick, accurate, experience-based responses: the problem-solution database, the reference library database and the reliability/availability/maintenance (RAM) database.

 

Problem-Solution Database

The problem solution database stores all previous problems and causes by class for GE and non-GE fleets. Once potential causes are defined, validation/testing of symptoms of the causes begin. Validation is conducted by a review of current relevant conditions, similar fleet problems and solutions, and expert team assessment and advice. A diagnostic engineer is the overall owner of the specific fleetwide component in question and validates each problem and solution before it is entered into the database.

 

Reference Library Database

The reference library database contains the full scope of technical documents for equipment and system design. It also contains the design and operating specifications for optimal performance. An example in the case of a gas tur- bine would be pressure drops across the HRSG and inlet exhaust systems, including the performance excursions as the unit sees an ambient temperature change.

 

Reliability/Availability/Maintenance

This tool gives the diagnostic specialist immediate reference to monthly RAM data provided by the plant operator. This data identifies the specific start-and-stop times of plant outages. It also computes reliability and availability calculations; in addition, it documents plant outage caused by a specific component. This allows for a model of plant availability as a function of mode of operation, design, fuel type and other common parameters. The results of the modeling used in conjunction with M&D data will be used in making recommendations for configuration and/or operating changes.

 

Experience

 GE Energy Services has deployed RS modules on over 150 units around the world and uses M&D as a tool to manage, analyze and resolve potential equipment problems. Real-time access and continuous on-line evaluation of turbine condition is available to our engineers for problem resolution. Several benefits were derived during customer application.

 

For example, an IPP partner operating during peak demand was alerted to a slight deviation from baseline rotor dynamic characteristics. Shutting down the plant meant up to $1 million in lost revenue per day. Immediately, GE engineers were online, assessing the signature to identify risk in continued operation of the turbine. The evaluation resulted in a realization that this rotor signature suggested a shutdown and machine inspection. The inspection, combined with the data analysis and prior analysis history, caught the condition before significant rotor and other system damage took place. Detecting this incipient failure quickly and correctly allowed for the equipment's rapid repair and return to service. The estimated saving to the customer through generation of revenue exceeded $150 million.

 

Another example of the demonstrated value of M&D occurred during the normal data review process at the M&DC when it was noted the combustion exhaust profile of a gas turbine was beginning to change. The monitoring frequency of this gas turbine was increased from four hour to one-hour intervals. The unit was placed on M&D combustion alert and the customer was notified that a potential combustion issue was developing. Exhaust combustion profiles continued to indicate that a combustion issue indeed had developed. Using the M&D GTDM monitoring strategy, the customer w-s able to operate safely for an additional 13 days to a non-critical production time before the gas turbine was shut down and a combustion inspection focusing on specific combustion hardware was performed. This recommendation was preceded by a technical review with the customer to explain what the data indicated. Results of an inspection revealed that the specific hardware had experienced cracking, making continued operation of the unit no longer prudent. The unit was back in operation two days after the unit was shut down for inspection and subsequent replacement of hardware.

 

Conclusion

 GEÕs RS system is part of GE Power Systems- Energy Services offerings to increase output, performance and availability. The system consists of modularized functionality, which can provide a full scope service that will:

 

 

RS provides the ability to access, transmit, analyze and report on the operating conditions of a wide range of customer equipment. Through learning experiences and key technological developments and acquisitions, RS gives customer operators, managers and diagnostic experts the proper tools to make equipment, plant and/or fleet-operating decisions.

 

References

 Makansi, J., ÒOutage/Maintenance Management Puts Information Technology to Work,Ó Power, pp. 41-49, January 1994.

 

Madej, J. et al., ÒMonitoring and Diagnostics Service Delivery System,Ó GER 3956, GE Company, 1996.