Drax Power Limited
Drax Power Station Process Control Refurbishment (Units 1 to 3)
Analogue Based Technology
First half control systems were based upon various technologies from that age and mainly comprised conventional hard controls and indications, relay based sequencing equipment and analogue based technology for the boiler modulating controls. This equipment became obsolete and difficult to maintain and also limited the flexibility of the plant.
Therefore Drax needed to replace these systems with a modern and flexible process control system in order that the generation plant could be operated more flexibly to optimise production in line with Drax’s demanding business needs. In addition, due to the environmental restrictions placed upon all power generators regarding emissions, new plant and equipment was installed which required additional control systems to be closely integrated into the main process control systems.
Following the successful pilot project of an Advanced Process Management System (APMS) at West Burton in the mid 90’s, the decision was taken to embark upon a complete control and instrumentation refurbishment on the first half Units (1-3) at Drax. In 1997 Capula was awarded the turnkey contract for the implementation of the full control and instrumentation refurbishments on the first half units scheme. The project was successfully completed on the first unit within 9 months. As well as advanced control and automation, this project involved significant electrical installation work involving cabling, instrumentation, desk and cubicle replacements which was included in our contract and implemented with assistance from our installation sub-contractor.
Soft Desk Operator Interface
The main requirement for these projects was to improve the operational flexibility of the unit and increase reliability and availability, particularly during start up. This was achieved by completely replacing the traditional hardwired control desk and back panel with a soft screen operator interface and installing a new digital control system for the automatic boiler controls.
The chosen Human Machine Interface (HMI) on all the units was APMS. This is a powerful operator platform SCADA product designed specifically for the demanding needs of the power industry, and runs under Verano RTAP on Tru64 UNIX on a dual redundant Compaq Alphaserver computer platform.
The chosen process control platform for the project was Siemens Moore APACS – a powerful, sophisticated PLC platform providing high reliability and compliance with the IEC1131-3 programming environment.
Boiler protection was provided by hard wired relay based interlocking systems. These were refurbished and retained intact, whilst monitoring of the relays was brought into the DCS to improve diagnostics. Operators interact with the system through nine 21” workstation screens, supplemented by three 67” rear projection screens which forma video wall.
Plant monitoring and control
With respect to plant monitoring and control, basic operations are carried out through simple control panels, whilst more complex functions are driven through custom designed displays. Particular attention was given to the new desk which is based on the latest modular technology.
Extensive diagnostic facilities
As all plant related information is held in a central repository, this facilitates the use of a task based working environment for key functions in addition to the traditional plant area approach.
The value of this to the operations staff is reflected in reduced workload and risk whilst navigating screens. Operator best practice was built into the system.
Extensive diagnostic facilities are inbuilt to assist fault finding and maximise the availability of the system. A separate emergency shutdown desk section was provided with conventional controls and indicators to enable the safe shutdown of the unit in the unlikely event of a computer failure.
The first unit was returned to commercial operation on the planned date and on budget, and was deemed to be a complete success by both Companies. Drax went on to exercise options with Capula for modernisation of two further units, both of which were fully completed and returned to service on time and to budget.
Since then Capula have continued to provide support of all systems through support contract arrangements. Having successfully completed over 25 similar major refurbishment projects in power stations across the UK, with a 100%record in bringing the units back to service on schedule, this makes Capula the leader in Process Control System refurbishment on coal fired power plants.