Efficient, reliable network operation is essential in these deregulated times. The UK’s National Grid Company is about to install a new integrated energy management system that will help it maintain its current operations and adapt to future needs.
GE Harris’ XA/21 system will help NGC meet future operational requirements.
Eighteen months ago, National Grid Company (NGC) of the UK began to look for suppliers for implementing a new integrated energy management system (IEMS). In February 2000, it awarded a $20 million contract for the project to GE Harris Energy Control Systems, and is now on track to commission the system in autumn 2003.
The new system will be the primary interface for the real-time management of NGC’s power system as well as the source of data for other computing systems to carry out other functions. It will, according to NGC, meet not only the company’s current needs, but also allow it to adapt to changing future needs.
NGC is the largest privately-owned, independent transmission system operator in the world and is among the top 100 FTSE-listed companies in the UK. It owns and operates the 400 kV and 275 kV transmission system in England and Wales and is responsible for matching the generation of electricity and demand in the region. When the region’s New Electricity Trading Arrangements (NETA) come into effect in autumn 2000, it will be the system operator and will also be responsible for balancing the system using the balancing mechanism.
Operating in a deregulated, competitive environment, utilities such as National Grid are under pressure to reduce costs, maximise efficiency and maintain adequate security margins. This, however, was not the main driving force behind NGC’s decision to implement a new IEMS.
NGC’s current system was commissioned in 1993 and is based on the Artex 2 system supplied by CDC, a company later bought by Siemens. The system was installed at NGC’s main national control centre and also at four other regional control centres, but has been discontinued as a product, and the hardware is obsolete. In addition, the four regional control centres were closed, except for one which now serves as a contingency control centre, following a period of consolidation by NGC which was completed in 1998.
The obsolete system needed replacing, therefore, and a system that could cope with future changes that NGC faces, was required.
NGC’s future needs are clear. Although the changes that NETA will bring to the liberalized market in England and Wales will not directly impact on the company’s EMS systems, the four-hour balancing mechanism and other features of the new trading mechanisms will require some changes; NGC will have to cope with shorter time frames in the balancing mechanism and more on-line applications. NGC therefore needs a system with a higher level of sophistication.
An IEMS that was easy to upgrade was also needed to prevent early obsolescence, along with a supplier with a proven track record, according to NGC’s IEMS Project Manager Bruce Archer. “It’s not fundamentally about saving costs, it’s about being able to maintain the service and expand the system for future business needs,” said Archer. “We are looking for a system that can keep up to date with technology from a supplier that’s going to be there for some years’.
NGC went through an extensive tender evaluation and contract reconciliation exercise with the main EMS suppliers before it awarded GE Harris the contract. GE Harris will supply NGC with its XA/21 IEMS for real-time management of its entire system. The NGC transmission system comprises 7000 route km of overhead lines, 650 km of underground cable and over 300 substations. It also owns and operates interconnections with France and Scotland.
The XA/21 system’s key operational functions include interfacing data acquisition and control with all NGC RTUs, presenting events and alarms via modern user interface facilities, providing real-time and historic data to other computer systems, and archiving data for replay and analysis. The system also includes a full complement of advanced real-time and study network analysis tools to assist users in managing the power system, applications to manage various operational safety procedures and related documents, and a dispatcher training simulator.
Over 100 Sun workstations will be installed at NGC’s national control centre at Wokingham in Berkshire and its contingency centre in Birmingham, and some 125 users will need to be trained on the new system. The XA/21 will initially communicate with 260 NGC substations via the Energis communications network and will continuously monitor up to 250 000 alarms and switch states and 17 000 analog readings for real-time grid system management and control.
Installation of XA/21 will also allow NGC to reduce the amount of custom-built software, cutting the number of special enhancements needed from 200 to 70. This will reduce implementation time and will also simplify future maintenance support and system upgrades.
The implementation of future upgrades will keep the XA/21 system ‘evergreen’, i.e. keep it up to date with emerging technology in order to help NGC meet its evolving business needs. The XA/21 will replace NGC’s system management hierarchy of SCADA and Power System Management (PSM) computers that cannot be developed to meet future needs. It will use 30 interconnected Sun Enterprise servers that will provide display and data access to the workstations. This will overcome a constraint of the current system that prevents users from accessing data and displays in a SCADA or PSM system to which they are not connected.
The XA/21 system has modular software and open system architecture allowing operators to see a real-time view of the entire electrical network. It has the ability to allow the analysis of alternate operating strategies based on current or postulated system conditions, an important feature in deregulated markets where wholesale power trading is increasing.
Using XA/21’s distributed processing architecture, a utility’s enterprise system can be entirely integrated and interfaced. It can unify corporate data across the utility’s operational system while providing a single system image and a single point of maintenance. The architecture consists of three main components: data acquisition and control (DAC), the database, and the graphical user interface.
Data acquisition and control: The DAC acquires measurement data via remote terminal units or data links via industry standard protocols. It validates the data for reasonability and communication failures, determines the quality and integrity of the data, and performs checks on process variable limits and executes the user-defined calculations. The DAC also generates alarms for abnormal data conditions, and provides remote supervisory control capabilities.
Database: The XA/21 database provides a single secure repository for all mission critical data. Its View Data Editor provides an object-oriented user interface for the administration of data in relational form, thereby eliminating the need for detailed knowledge of the underlying database structures. Key features also include:
- Relational source and historical databases
- Online database updates
- Full semantic and syntactic validation of data
- Performance-oriented run-time database
- Interface to other corporate archival systems
- An option for geographically distributing source and run time data, enabling distributed operation and maintenance, the sharing of data among sites without administering that data, and disaster prevention and recovery between sites. Graphical user interface (GUI): The GUI of the XA/21 allows the operator to visualize the past, current and future operating states of the power system and take the necessary control action to ensure economic operation. It also has high speed pan and zoom capabilities to allow the operator to navigate large interconnected system networks easily. Other key features include:
- Deterministic display response, secure, controlled access from outside the control room via the corporate intranet or extranet.
- X Windows displays for consistent user interface regardless of platform
- DFX graphic import capability
- Single set of oneline display definitions for all applications
- Display definition and maintenance using AutoCAD.
Building on these foundations are modules that can be integrated to form a fully IEMS. These include power network applications (PNAs) which provide the operator with the capability to analyse and optimize the operation of the transmission grid under current and postulated conditions.
PNAs such as state estimation and contingency analysis are software applications that use available telemetered status and analog data to improve the reliability of the transmission grid by alerting the operator to the presence of existing or potential overloads and abnormal voltages. The state estimator can also estimate quantities that are not metered, and can improve metering reliability and reduce maintenance costs by detecting sustained measurement errors, estimating replacement values and alerting personnel as to the location of suspect metering.
NGC’s IEMS will be commissioned in Autumn 2003. The utility has a support agreement with GE Harris that will see its new system software maintained and upgraded until 2015. NGC will also play a part in the development of the XA/21 in years to come, according to Archer. “We have made ourselves active in the user group that determines where the product goes, and we looked at long-term strategies as part of our decision making process.” GE Harris’ XA/21 system will help NGC meet future operational requirements.