Migration in record time

With the help of the Siemens Solution Partner Gesellschaft für Automatisierungstechnik (gat) and the TIA Portal, a power plant in Neubrandenburg, Germany accomplished the migration from Simatic S5-95U to Simatic S7‑1500 within a very short time frame.

Neubrandenburg has a population of roughly 65,000. A gas and a steam turbine plant operated by the public utility company secure the power supply of the inhabitants. What’s special in Neubrandenburg is the option the city has to store geothermal heat. It enables the power plant’s already high level of efficiency, for which it is known, to be increased even more. However, the capacities are somewhat limited so that the heat demand is the determining factor for the plant’s operation. All together, approximately 75 MW of power are generated, along with some 90 MW of heat.

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    Retrofit and optimization – along with highest availability

    Two gas turbines are responsible for the generation of electricity. They complement each other, and also replace each other whenever one is undergoing maintenance or repair work. The turbines operate redundantly, thereby making sure the lights stay on in Neubrandenburg. When the power plant was built in 1996, the Gesellschaft für Automatisierungstechnik (gat), based in Geesthacht, Germany, automated the two natural gas compressors, which are connected upstream from the turbines. A SIMATIC S5-95U and a SIMATIC OP5 operating panel were installed at the time. The signals from the Ex zone were integrated via third-party coupling modules. After replacement part supply for the modules was no longer ensured, the power plant operator commissioned a retrofit for the plant – also from the gat. The experienced Solution Partner offers automation solutions from a single source for all types of electrical engineering, measurement, control and instrumentation technology tasks and fields – from the concept to the commissioning and operation of the plant. The new requirements called for the connection of the plant to an existing higher-level control system in order to centralize the logging of alarms and the visualization. The connection needed to be able to receive the signals from both controllers via MODBUS and centrally carry out set-point adjustments. It was important that the existing wiring in the Ex zone thereby be maintained.

    Clever: S7-1500 as compressor controller and control system

    Manfred Hackbarth, gat director, chose to go with a SIMATIC S7‑1500, both to control the two compressors and for the control system connection. Now the signals from the Ex zone are connected to the control system through the already intrinsically safe SIMATIC ET 200iSP distributed I/O system. An additional coupling level via explosion-protection barriers is therefore no longer needed. As a Siemens Solution Partner Automation Drives, Hackbarth already had the chance to get to know and appreciate the S7‑1500 during a pilot application. “Since the coupling level is no longer necessary, we now have very neat wiring and a reduced spare parts inventory. We also benefit from the integrated MODBUS interface of the CM5411-PtP module,” Hackbarth explains. Since each compressor has its own SIMATIC Comfort Panel KP1200, they can be operated autonomously. The connection to the control system results in a highly available redundant system that precisely adjusts the compressor output for the respective energy demand.

    A positive converter experience

    As Hackbarth recalls: “One particular challenge for us was the fact that we only had two weeks for the entire transition. We had already exhausted our SIMATIC S5-95U options with complex controls using every trick in the book. It would have been impossible to reprogram everything in such a short time. Therefore, it was clear from the start that we would have to convert the existing programs.” The migration of the S5 program was performed in two steps. First, the S7‑300 code was generated using the S5 data converter. It was then converted into an S7‑1500 program. Hackbarth was pleasantly surprised. “The sequence and logic sections were transferred completely without any problems. There was also no need to change anything during commissioning,” he points out. “The analog value processing and the control were reprogrammed in the TIA Portal. We especially benefited from the floating-point arithmetic. For the visualization, we were able to transfer the TIA Portal variables to the SIMATIC WinCC with drag-and-drop functionality. Communication configuration between the three controllers was very easy thanks to the integrated assistance and automation tutorials function. The trace function of the S7‑1500 proved very helpful during the commissioning of the control system. Variables to be defined are stored in the CPU in a selected time slot. In our case, set-point values, actual values and control variables were recorded. That made setting the control parameters and checking the function in various load ranges very easy.”

    New TIA Portal options

    Hackbarth’s conclusion: “Replacing the existing SIMATIC S5 controllers with the new SIMATIC S7‑1500 is definitely advisable, because spare parts are available over the long term. The two-step migration with the offered converters is no problem at all. However, the question of whether it might not make more sense to take full advantage of the new modules and functions of the S7‑1500 during a reprogramming should be decided on a case-by-case basis. What’s more, the structured programming in the TIA Portal provides a very clear overview, thereby offering advantages for future program changes.”

    The power plant operator is also impressed with the new solution. Plant engineer Hartmut Beuster plans to use the SIMATIC S7‑1500 as the standard solution for further retrofits, for example, for the connections.