Drax Power Limited

Drax Power Station Process Control Refurbishment (Units 4 to 6)

Business challenges

Following the first half refit in 1997, the main control room comprised three modern ‘soft’ operator desks based upon the APMS SCADA system, and three ‘hard’ control desks using conventional controls and indications. Operating two types of control desk required different skills and restricted flexibility and efficiency.

Given the size of this project, a competitive tender was issued and after an intensive tendering period, Capula were awarded a multimillion pound contract to replace the process control and information systems on the second half units (units 4 to 6) plus the Water Treatment Plant control system and a large number of Common Station Service plant areas. A key factor is that the common services needed to be successfully upgraded whilst continuing to keep the plant in operation.

APMS system

The chosen HMI platform was the APMS system. This gives a uniform operator interface platform across all six units and common plant areas, thus simplifying maintenance and permitting operators to move around plant areas more easily. The APMS system is based upon the latest versions of the product which runs under the Linux operating system on a dual redundant Intel computer platform manufactured by Dell.

Schneider Quantum

The Schneider Quantum Unity PLC platform was chosen after an intensive evaluation period of suitable platforms carried out jointly by Drax and Capula and was favoured over APACS due to its improved performance, interface capability and longevity. Quantum Unity is the latest high end process control system manufactured by Schneider Electric and is based upon the proven Quantum PLC range which has found many applications in power and other industries. Unity provides a very modern and powerful PLC platform providing high reliability and compliance with the IEC1131-3 programming environment.

The new ‘soft desk’ was installed in the main control room and houses 10 off 20” LCD monitors, keyboards and mice. These are supplemented by three off Mitsubishi 67” projection cubes built into rear panels. Operator screens are designed to use the same standards as the first half units in order to provide a common user interface to the operators.

A separate emergency shutdown desk section is provided with conventional controls and indicators to enable the safe shutdown of the unit in the unlikely event of a computer failure.

Safety and plant protection interlocking previously controlled by a hard wired relay based system were replaced with a separate programmable safety system. This system is a Triple Modular Redundant (TMR) system which provides very high availability through its two-out-of-three voting of all channels and a functional safety integrity rating of IEC61508 SIL 2.

Commercial operation

Each unit was returned to commercial operation on time and budget after an intensive installation and commissioning phase. This brought the total to over 25 full Control and Instrumentation refits carried out by Capula over the previous 10 years; all units returned to service on time and with minimal disruption.

Why Capula

When a major power generator embarks on a complete process control refit within a fixed time frame, they can’t afford for things to go wrong. The potential for huge financial losses are real therefore they have to choose a company that can be trusted to deliver.

Based upon our track record of previous process control refurbishments at Drax and other sites, Drax Power selected Capula to undertake this important project as they could rely upon us to deliver this project to their complete satisfaction.