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One of the key topics of the energy transition is power quality

The absolute top priority of grid operators is to ensure a reliable supply of electric power

The energy transition, with its increasingly distributed power feed-in from renewable energy sources, poses major new challenges for distribution system operators. The goal is to adapt and optimize grid monitoring, control and automation systems at all levels to prevent disturbances in the quality of electricity and in particular to rule out fluctuations exceeding the required voltage-level range. Based on its long experience as a business partner serving the power industry, Siemens offers the right intelligent solutions and systems for achieving these goals.

Power quality in real practice

The vast range of application cases demands customized, tailor-fit solutions

How good is your grid? The rising number of fluctuating power producers feeding into the power grids requires targeted corrective measures to ensure high power quality.

Optimizing power quality is becoming an ever more complex and difficult task. Distribution system operators face daunting new challenges, especially from integrating renewable energy sources and coordinating the increasingly distributed power producers. How can disturbance and fault sources and impairments to voltage quality be efficiently and reliably detected? Siemens has developed numerous products and solutions for this purpose, custom-tailored to meet grid-specific requirements and thereby enhance the security of supply.

Semi-distributed concept for voltage and capacity management

Grids are accommodating a growing volume of power feed-in from numerous small, distributed power-producing facilities, which entails widely varying load and feed-in conditions with significant fluctuations in operating voltage. At the same time, the security of power supply and compliance with the regulations arising from codes and standards must be ensured, if possible without having to invest in costly grid expansions. In short, the challenges facing distribution system operators are growing on an enormous scale, and can only be mastered with intelligent solutions.

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Voltage regulation in a distribution grid according to different requirements

With an eye to enabling operators to be well-equipped for these and future requirements, Siemens has developed an intelligent semi-distributed design concept for managing voltage and capacity in power distribution grids. It's based on a regional controller and utilizes various approaches to voltage control depending on the given structures and conditions on site and in the field. In addition, various options can be combined to create an optimum, customized solution designed to achieve maximum efficiency with the existing grid arrangement.

 

Whether primary transformer substations or local distribution stations, modern remote-control systems and components such as voltage regulators at the medium-voltage level, controlled distribution grid transformers at the low-voltage level, or intelligent field devices, the solutions from Siemens not only ensure efficient operation of the entire medium-voltage grid. They also ensure regional and local voltage and grid stability right down to the low-voltage range.

 

Key benefits of this semi-distributed design concept:

  • Minimization of new investment through efficient use of existing structures
  • Improved capacity utilization of the medium- and low-voltage grids
  • Optimized use of the voltage range with just a few distributed measuring points
  • Regional communication with complex systems or high cost
  • Automatic monitoring of grid status for operation and planning

Smart products and components for smart voltage and capacity management

Harmony in the grid – through optimized power quality management

Owing to the growing volume of electricity generated by distributed power producers, grid operators in the future will have to monitor harmonic loads (e.g. due to potentially defective inverters) more closely. Such effects can negatively impact nearby industrial operations, and even television reception and computers in residential areas. Power grid regulatory authorities in many countries already demand compliance with EN 50160 as key performance indicators for power distribution systems.

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The integrated power quality solution shows only critical grid situation

For these and many other tasks, the SICAM product family offers a broad range of devices custom-tailored to serve various grid situations: from power measuring devices such as the SICAM P50 to the SICAM P850 as a Class-A measuring instrument in accordance with EN 50160. For integrating important components, SICAM Q100 also delivers additional information for further evaluation. Siemens has also developed the SICAM PQS Power Quality System as an add-on to the SICAM PAS to provide efficient analysis enabling automatic pre-processing of signals. As a result, the event monitor, for example. only displays critical grid situations and hides all irrelevant data.

 

Integrated solution for power quality management – with integral benefits

  • Automatic recognition and reporting of relevant events
  • Reporting and recording in accordance with EN 50160
  • Cost-efficiency through custom-fit solutions
  • Optimized ease of operation thanks to pre-processing of data

Product highlights for harmony in the grid

Validation of asset phase assignment

Phase asymmetries in grids can be detected and located based on captured data. These asymmetries often negatively impact equipment and electrical loads (i.e. electrical consumers) such as motors. As a growing volume of sensor and meter measuring data are available, these data can be used for analysis purposes, thereby greatly facilitating the difficult and time-intensive search locally for asymmetries among loads as well as sensors that have been cross-phased connected.

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Use of parallel data processing allows rapid localization of phase asymmetries

Parallel data processing by means of MapReduce functions can be introduced when dealing with large data quantities for the purpose of identifying sensor information that displays significant deviation from other condition histories. In addition, interactions and correlations with other processes can be evaluated and visualized. The more often events occur simultaneously at meters, the stronger the connection between them. Hence, this allows detection of asymmetries which a group of meters must verify independently of one another.

For example, such an investigation may reveal that these asymmetries occur in single-phase switched-mode power supply units of a residential building complex. The centralized telecontrol signal causes increased asymmetries when actuated because all loads are erroneously connected to the same phase. What is termed the power snapshot analysis delivers a synchronous replica of the grid condition based on smart meter data. A method developed especially for this purpose enables phase assignment in the low-voltage grid by means of electronic meters.

The voltage histograms yielded by the power snapshots deliver information on asymmetric loads. One analysis method involves interactive visualization of defined events such as sum totals or overvoltage and undervoltage.

Identify, locate and correct sources of disturbances and faults through PV inverters in the grid

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Identifying interference sources with unconventional methods of evaluating data

As a consequence of expanded use of regenerative energy sources, photovoltaic (PV) systems are generating an increasingly large share of our electric power supply. This creates new sources of disturbances and faults in the distribution systems that can negatively impact grid stability. A new approach to evaluation of existing data, however, provides the means for rooting out and eliminating these disturbances and faults.

 

The direct current generated in PV installations is fed into the distribution grid as a general rule by inverters. This requires setting certain specific parameters at these inverters governing such as aspects voltage and reactive power behavior. Stochastically distributed measured values can be used to validate these parameters to identify disturbances and faults that arise due to erroneous parameterization.

 

By creating graphic displays of these interactions and correlations, disturbance and fault situations in the grid are clearly reflected in the diagram. Correcting these values allows these settings to be adjusted – such that this unconventional evaluation of data makes it possible to analyze and eliminate sources of disturbances and faults in power grids.

References

Solutions tried and proven in reference projects

The products and solutions from Siemens for ensuring a reliable power supply, optimizing electric power grids and improving cost-effectiveness have long been tried and proven in practice. Listed below are just some of the reference projects.

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