Harmonised PLC use through single interface

An improved and simplified single operator interface, that gives greater insights into the performance of district heating plants, is realised by Ume Energi after it standardised on ABB control technology. With fewer process screens leading to lower operator risk, the company has significantly improved monitoring and process control and operator effectiveness of its plants.

Because the district heating network had expanded over time, the Swedish energy provider found itself using a mix of control systems, human-machine interfaces (HMIs) and programmable logic controllers (PLCs). This was the result of different departments working with various subcontractors employing their own automation products for the PLC control. There was no standardisation.

Ume Energi's ambition is for all its PLCs to be visible through the same HMI, so that the operator would have a familiar work environment, while minimising risk, operating and maintenance costs. Having all information available in one single HMI gives the operators and maintenance staff new ways to proactively monitor processes more efficiently and maintain a high system and plant availability.

At the heart of its distributed control system are three independent ABB Ability System 800xA platforms, each managing sections of the two district heating plants covering Ume. In addition, the company uses 21 Siemens S7-300 PLCs to control pumps in booster stations and sectioning chambers so that the correct pressure is maintained throughout the network. The PLCs were operated using two Siemens Simatic HMIs.

However, these HMIs were outdated, making PLC operation increasingly difficult. This led to higher maintenance costs and increased risk. Furthermore, with only basic integration with the Ability System 800xA, operators were forced to use different HMIs, each with its own look and feel, to manage different parts of the same plant.

Integrating PLCs

While modernising the Siemens HMIs would be the most obvious answer, it would not provide the single operator experience Ume Energi desired. An alternative approach was sought that would integrate the 21 PLCs into ABB System 800xA, which would then act as the main HMI.

The fast track way of integrating PLCs is to use ABB OPC Connect; a tool that connects PLC objects and its signals simultaneously, such that up to 50 per cent of engineering time can be saved. This avoids the time-consuming manual integration of individual signals from each asset.

Ume Energi took the opportunity to standardise on the function blocks used within its PLCs, thereby removing the many different object types created for the same asset, such as pumps or valves. Dirk Mottmann, IS and Process Manager at Ume Energi says: "We did a thorough work in standardising our function block library. I think it is absolutely necessary if you are planning to do this kind of integration." Now with function blocks optimised to match their application and fewer object types, integration into the System 800xA's HMI would be highly cost efficient.

Information from the PLCs was directly integrated into the existing process screens of the System 800xA HMI. This meant that the presentation in the process screens could be optimised, such that the original 100 process screens in the Siemens setup, was reduced to 20 process screens in System 800xA.

For the operator, it does not matter which controller or PLC is connected to the asset, everything works in the same way and for the operator the experience is a seamless integrated environment.

Ume Energi now has one common HMI that spans the entire system and its processes, giving the operator a completely integrated plant and district heating network experience. Furthermore, all production and distribution network process data are available in one common database. This enables Ume Energi to conduct, for the first time, a larger investigation to see how different parts of the distribution network interact and how they could be optimised together.

The PLCs are optimised to work together, fine tuning the complete process, instead of only completing their individual task therefore creating a much more coherent process control of the PLCs.

Go to www.abb.com for more information about ABB System 800xA and ABB OPC Connect.