Plant B of the Sapugaskanda Thermal Power Stations has eight 10MW installed capacity-diesel generators and has an annual energy production of 500GWh. This plant with approximately 260 employees was commissioned in two phases in September 1997 and September 1999 respectively (B1 & B2) with the Instrumentation and Control system of Siemens Simatic S5. This system was first implemented thirty years ago functioning as a Data Acquisition system. However, the migration to Simatic S7 has become essential for all automation systems, especially for increased functionality, availability and efficiency.

Thus, Siemens together with DIMO took on the challenge of upgrading the Sapugaskanda Plant with minimum disturbance to the operations of the plant and successfully completed the project without any loss of production and zero hazards.

The Solution

The Automation system (Instrumentation & Control) of the Simatic S5 PLC was considered to be obsolete by the manufacturer, Siemens AG. Therefore, replacing it with the latest Simatic S7 PLC was essential with DIMO approached to provide a total solution.

Thus, this project involved the upgrading of the Siemens S5 PLC Control & COROS Data Acquisition System to S7 & SoftOM Data Acquisition System.

For the above, the work scope carried out by DIMO included:

Establishing a backbone network of fibre optic cables for the automation highway of the main PLCs at the Switchyard, Plant room A and B; splicing, terminating, commissioning and testing for communication losses for the same.

Establishment of a Local Area Network (Ethernet) and Process field bus for the Application and Automation highways of the main PLCs at UM, NK and KA* panels. Terminating and testing for communication losses for the same and commissioning.

Site management, resource management and manpower utilization for all control, power and data wiring. Installation of Optical Link Modules and Fibre patch panels together with outdoor type enclosures.

Control wiring of all PLC units at UM, NK & KA panels of 08 numbers of Diesel and 12 numbers of stand-alone Generator sets. Testing and hot/cold commissioning of all PLCs, Control wiring, Input/outputs and alarm/tripping conditions.

*Note: The Plant consists of eight diesel generators each having three major I&C panels called UM, NK & KA (German abbreviations). Those I&C panels are dedicated to certain DAQ/controls as mentioned below;

  • UM – Engine controls (Speed, fuel, temperature, etc.)
  • NK – Generator controls (Gen protections, Power output, temperature, etc.)
  • KA – Other auxiliary services (Viscosity, Lube oil, nozzle cooling water, etc.)


The result of this upgradation project is largely beneficial for the power plant as well as the public at large. The monitor and control facilities have been largely improved with fewer operational staff required for the control centre in comparison to the previous system. All reports (alarm printer and report printer) are automatically generated. Since the main Server runs redundantly, all the data is archived for “anytime-usage”. Furthermore, the HMIs located at each generator’s control panel are touch-screens from which faults in the system can be diagnosed and rectified. The system has been handed over to CEB with DIMO maintaining the system under the Defect Liability Period contract.