The generating utility market’s deregulation has underscored the value of stand-alone generation management systems – real-time control systems that monitor and control generation assets over a wide dispatch area, helping firms maximize the benefits of corporate control over key elements of their industry while allowing autonomous plant operation in some day-to-day functions.

Rahul Nargotra, Invensys Operations Management, Singapore

In the past 15 years, many utilities have migrated from a vertically regulated structure, where electric power distribution, transmission and generation are managed in a single load control area (LCA), towards a market-based structure where the load control area is managed by an independent entity called an independent system operator (ISO) or regional transmission operator (RTO).

These changes have required different automation systems and business models. In the traditional vertical utility with an LCA, the utility maintains generation, transmission and distribution assets. The utility generates power, buys and sells power from neighbouring utilities, and is responsible for regulating system frequency in its area.

The regulated utility knows its instantaneous load and monitors the exchange of power with neighbouring utilities. In the USA, the rate base at which the utility charges the end user for power generation is regulated by the Public Utility Commission (PUC), and wholesale transactions are regulated by the Federal Energy Regulatory Commission.

Traditionally, as the rates a utility can charge for electricity generation, transmission and distribution were regulated, utilities have focused on reliable delivery of electricity with limited capital investment. Growth of the power generation market was often restricted as utilities held a monopoly on the generation, transmission and distribution of electricity in their regions.

Generation management systems

Generation management functions were traditionally part of the utility’s Energy Management System (EMS). The generating utility, or genco, is for the first time now specifying and procuring a new type of control system, the generation management system (GMS), sometimes called a GenDesk (Generation Desk).

The GMS system replaces the traditional automatic generation control (AGC) component of the EMS system, and provides for additional functionality geared towards the new issues related to power generation in the de-regulated market. These issues include:

  • Wide area generation control of owned assets;
  • Market-based economic dispatch;
  • Operator scheduling interface;
  • Interface to in-house systems;
  • Interface to generating plant DCS;
  • Interface to ISOs or RTOs;
  • Interface to publicly available information;
  • High adaptability to new business requirements.

Within the offering from Invensys Operations Management (IOM), the GMS system links to the distributed control systems (DCS) and PowerEdge, which promotes collaboration and monitoring performance tied to business goals, and provides the following basic functions:

  • AGC: The basic cycling programme compares the actual versus schedules and the error accumulation and payback. From this, setpoints are determined for each generating unit or lump-sum plants under control and are sent to the individual units. Ramping of units is performed to meet new schedule requirements.
  • Flexible generation control: The GMS also receives from the ISO or RTO direct dispatch instructions and calculates individual plant or unit setpoints, and sends those setpoints directly to the resources.
  • Scheduling: Interfaces to a utility’s power bidding and scheduling system, which allows the operator to view and modify day-ahead and hour-ahead schedules to meet their overall scheduled megawatts.
  • Metering: Provides for monitoring and optionally control of associated generation, under contract to the generating utility or where the generating utility has a commitment to monitor the generating resource delivery according to market bid.
  • Real-time data: Provides real time data from various sources, including in-house generation sites and the ISO.
  • Market information: Publicly available market information, typically from the internet, is made available to the system operator to improve his decision-making process. The automated process scrapes data from publicly available web pages and/or contracted data sources using HTML (Hypertext Markup Language) or XML (eXtensible Markup Language). The data are made available as any real-time data source and are available for display, historization, decision-making processes and trending.
  • Energy accounting: Provides for accumulated information made available to the generating utility planning authority for ‘after the fact’ accounting. This includes accumulation of generated megawatts and schedules over time for accounting of energy generation.
  • Emergency generating needs: Ensuring these are met to handle abnormal generating requirements such as resource rejections, cutbacks and lay-offs. 

Williams Power Company case study

Williams Power Company, formerly known as Williams Energy Marketing and Trading, is a subsidiary of The Williams Companies that bought and sold energy commodities, including electricity, natural gas and refined petroleum products, as well as provided risk management services to wholesale utility and industrial companies in North America.

The company managed 7900 MW of electricity and 0.8 billion m3 of natural gas per day. The Invensys GMS system provided to Williams Power in 2006 enabled it to monitor and control 12 owned or under-contract power plants and three ISO control areas: California ISO (CAISO), Midwest ISO (MISO) and Pennsylvania/New Jersey/Maryland Interconnect (PJM).

Applications such as General Physics’ EtaPRO offer valuable tools for utilities that need to monitor and control many operations Source: General Physics Corporation

The GMS system provided the following main components: two redundant main servers acting as symmetrical primary and back-up InFusion Industrial Application Servers (IAS); a high-availability InFusion Historian database server and galaxy repository; a high-availability web portal server utilizing InFusion Suite Voyager; eight operator positions utilizing InFusion-View separated into generation desks for each operational area (West, Central, and East); and an engineering station for development using the InFusion Engineering Services.

The system interfaces to an existing LiveData ICCP Server, which in turn interfaces to the Alleghany Electric EMS; the Georgia System Operations Center EMS; Red Oak generating plant; the CAISO for retrieval of ADS information (using MS SOAP web interface); and the MISO dispatches for Kinder Morgan (using MS SOAP web interface).

In the Williams Power GMS system configuration 12 modbus over TCP/IP interfaces are provided to DCS systems in the generation plants controlled by the GMS system.

The system also supports a PI interface to the Cleco generating plant using the OSI Soft OPC Client interface software. Setpoints are retrieved from the Red Oak plant using a file transfer protocol (FTP) interface. The data are retrieved every 15 minutes and placed in the database.

Distributed network protocol (DNP3) is provided for future interfacing to alternate plant resources. Each operator position has two screens: the leftmost screen is the primary screen and the rightmost is the back-up.

The three most recent alarms are always shown on the primary screen. The top of the screen is divided into a menu bar, which provides for drop-down menus and display navigation. Data fields are dynamically coloured to indicate the status and alarm conditions of each field. Historical trending is supported using the Active Factory gateway. In addition, a number of customized Active Factory workbook reports are configured to support the reporting of various plant sites.

The GMS system provided Williams Power Corporation with automatic downloading of AGC setpoints to generation plants, as well as the monitoring of operation of plants versus actual setpoints requested; historical data collection, including short-term and long-term data capture in Microsoft SQL compatible format; maintained calculations of plant gas usage, total plant generation; interfaces to other automation systems using Modbus, DNP3, FTP and PI server interface; immediate alerting of abnormal operating conditions for fast resolution of system operating problems.

Performance Monitoring and Diagnostic Optimization

Performance monitoring means: knowing actual and expected performance for current ambient and operating conditions; knowing where inefficiencies are and their impact on financial performance; understanding the impact of performance deficiencies on current and future operations.

The objective is to have performance information available to the entire power generating enterprise in a concise and timely manner.

A plant belonging to South Africa’s Sasol, among the clients of Invensys Operations Management’s solutions for running power utilities Source: IOM

IOM offers the EtaPRO™ performance and condition monitoring from General Physics Corporation. EtaPRO with VirtualPlant™ technology provides real-time knowledge of plant performance for the entire generating fleet of the enterprise down to the plant equipment level.

When integrated with the plant’s distributed control system, this solution provides management and operations personnel with decision-support tools for optimizing plant performance and economy. EtaPRO compares actual plant performance to expected performance using real-time VirtualPlant thermodynamic models and puts these comparisons, both real-time and historical, on the users’ computer desktops.

Solutions such as Enterprise Asset Management (EAM) from Invensys Operations Management (IOM) can enable enterprises to do more than simply maintain assets. They are also designed to meet the sophisticated maintenance and materials management requirements of today’s asset-centric organizations.

Fully and seamlessly integrated with distributed control systems on the plant floor, they incorporate and respond to predictive condition monitoring processes, which facilitates business intelligence through key performance indicators in decision-support solutions.

Global enterprise capabilities are inherent in the IPS Asset Management solution, and provide large organizations with the ability to operate multiple businesses within a single asset management installation. Each business unit may run autonomously, while still providing the enterprise with the ability to quickly and easily consolidate and analyze information across all of them as a whole. Costs of maintaining the system are minimized as a result of centralizing the hardware and software needed to support the global enterprise, without compromising on EAM capabilities. Furthermore, the IPS Asset Management solution offers the same robust functionality in its thin-client applications that users have come to expect in traditional solutions; hence, no compromises need be made on either functionality or performance.

Seamless integration with the plant floor enables the IPS Asset Management solution to take account of current operating conditions, and respond to warnings and alarms raised by monitoring systems in the production environment. Changing conditions that may impact the ability of production to deliver can be caught early, and dealt with through preventive and predictive maintenance routines that have much less impact on operations than unplanned emergency downtime.


General Physics’ VirtualPlant Technology is the cornerstone of several advanced application initiatives.

1. Thermodynamic modelling framework uses engineering models of major plant components & cycle

2. Conventional Rankine (Fossil), Nuclear & Combined Cycles

3. Intuitive drag & drop connection methodology.

4. Component wizards for modeling complex equipment

5. Real-time host for on-line deployment with EtaPRO.

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