Smart grid solution with a scalable power quality measurement system
Due to the increasing changes in electrical grids, load flow information is becoming more and more important. For you as a distribution network operator, increasingly also in combination with power quality data. As a distribution network operator, you are increasingly complaining that the relevant information at grid level 7 is either not available at all or is inadequate. Without a proper smart grid solution, this would be equivalent to “flying blind.” Intelligent metering systems (smart meters) won’t help you with this either. This is because, among other things, these are only suitable to a limited extent (e.g. due to data protection rules, insufficient measurement performance for network management, etc.).
One of the great challenges is that the formerly centralized electrical energy world is developing into a highly dynamic as well as very complex decentralized system. In this context, it must be possible to systemically process new but relevant information in a targeted handling of data.
ewz on the way to the smart grid
The “Elektrizitätswerk der Stadt Zürich” (Electricity company of the city of Zurich) has been responsible for the supply of electricity in Zurich since its foundation in 1892. As an institute under public law, the EWZ is organizationally subordinate to the Department of Industrial Operations as a service department. At the same time, ewz is also very well networked internationally.
Read here a media release how ewz has set out to roll out a fully comprehensive and digitalized smart grid solution. Companies such as smart grid solutions AG with its complete approach, Venios with its Venios Energy platform and Camille Bauer Metrawatt AG with the latest and scalable measuring technology of the LINAX® PQ5000CL series provide support.
Excursus: What does Smart Grid mean
A smart grid is an electrical system that intelligently ensures the exchange of electrical energy from various sources with consumers of different demand characteristics by incorporating measurement and mostly digital information and communication technologies. Such a system should take into account the needs of all market players and society. The use and operation of the system can thus be optimized and made more efficient, costs and environmental impact can be minimized, and the quality and security of supply can be guaranteed to a sufficiently high degree.
Source: Federal Office for Energy (BFE)
Classical differentiation matrix of measuring devices in the context of application
Effects of a smart grid on measurement technology
Basically, the common measurement data of voltage, current and frequency as well as their derived quantities are still required. However, and here comes the possible challenge for the smart grid application: The metering data will be combined and related to new customer needs (e.g., scalability, real-time, connection to existing control systems, integration into new platform solutions, connectivity, distinct technical consulting needs, cyber security, additional costs, etc.). Thus, the traditional IEC groupings of electrical instrumentation will possibly change and overlap even more. In addition, it certainly makes sense to continue to use analog indicators (electro-mechanical) redundantly for essential functions. These will withstand any failure and/or attack of a data communication. This is also very clear from the matrix shown above.
Customer Value: A modular smart grid solution incorporating the power quality
Basically, the measurement task initially creates “transparency in the cable”. For you as a distribution network operator, this means that the load flows can be controlled at network level (6) 7 and that the network quality limits can be used efficiently. As a result, no expensive network expansion should be necessary in order to avoid the enormous costs associated with it. For you as a network operator, this also promotes the issue of general resource conservation (e.g., dispensing with additional quantities of copper).
The basis: A metrological compass for Smart-Grid Solution
A scalable measurement system with Current Link
We propose certified power quality detection and power analysis up to 32 channels in the sub-distribution. Signal processing is implemented on the LINAX PQ5000 series measuring device. There, the respective current measured values of the so-called current link modules are processed. By means of the link technology, the individual Current Links and their sensors (Rogowski) are networked in a scalable manner by means of signal loops via coaxial lines. This reduces the installation effort to an absolute minimum and ensures proper cable routing. In addition, this measurement system for determining power quality is extremely cost-efficient. Thus, the scalable measuring instrument virtually combines the areas of transducers according to IEC60688, power metering and monitoring according to IEC61557-12 as well as power quality instruments according to IEC62586-1.
Fields of application
- Monitoring of power supply in substations
- Monitoring of industrial power distribution systems
- Energy optimization through identification of load behavior
- General smart grid applications
Exkurs: Why Coaxial particularly is verysuitable
Coaxial cables are two-pole cables with a concentric structure. They consist of an inner conductor (also called core), which is surrounded at a constant distance by a hollow cylindrical outer conductor. The outer conductor shields the inner conductor from interference radiation. Coaxial cables are suitable for transmitting high-frequency, broadband signals in the frequency range from a few kHz to a few GHz.
Due to their physical properties and simple nature, coaxial lines are very well suited for scalable current link technology. The high-frequency signals are transmitted cleanly and with high performance. In addition, interference from outside as well as interference to the outside is very well shielded. The coaxial technology also makes it possible to set up ring lines with a maximum total length of 20m as a “quasi-bus”, which in turn reduces the wiring effort enormously.
Thus, the auxiliary power supply of the Current Link modules as well as the signals are transmitted in one cable. This eliminates the need to feed many confusing individual cables into a distribution cabinet. In addition, the existing IT infrastructure is not additionally burdened, since the hard cabling is insensitive to radio signals. Hacker attacks via or even into the ring bus are also eliminated.
Advantages of the scalable measuring system with LINAX PQ5000
- Metrologically certified PQI according to IEC61000-4-30 Ed. 3 class A as basic device
- A scalable system for the areas of certified power quality as well as for load and efficiency management for up to 10 feeders
- An optional basic current measurement (e.g. directly after the transformer) with a high accuracy due to current transformer sensors
- 3 or 4 channels via Current Link per feeder (max. 32 currents)
- One measurement campaign time-synchronized for multiple feeders as opposed to the traditional measurement campaign per feeder
- Direct compliance reporting and event display by PQEasy reporting via web browser (e.g. according to EN50160)
- Time-synchronous fault recording of voltage events with currents of the individual channels (IEC61000-4-30 Ed. 3)
- Time synchronous load management for U/I/P/Q/cosφ
- Current measurement per Current Link channel up to 1’000A and overcurrents up to 20’000A
- Network tariff meter P & Q (purchase & delivery)
- Upgrade to control task in smart grid (e.g. PQ grid utilization)
- System management by means of a user-friendly multi-device tool for easy commissioning and efficient maintenance
- Large distribution systems (feeders) are continuously monitored with only one metrologically certified measurement system
- Low space requirement due to single voltage measurement
- Low wiring effort based on the scalable current sensors
- No need to shut down the plant for installation of the measuring system due to the non-invasive Rogowski measuring technique (Attention: observe occupational health & safety)
- Very high robustness due to proven coaxial principle
- Current values are time synchronous to voltage (IEC61000-4-30)
- Optional fault recording in case of short circuit
- Various communication interfaces (Modbus TCP/IP, Modbus RTU, REST API, IEC61850, Cloud with MQTT, Webbrowser) allow high connectivity flexibility to parallel as well as higher-level systems
- Multilingual
- Fast roll-out with robust measurement technology
Stationary power quality and load flow measurement
Mobile power quality and load flow measurement
Not to forget…the data and manipulation security on the level of measuring devices
Conclusion
Electrical network complexity continues to increase. To do this, it is probably important for you as a distribution system operator to create good transparency in the network and process it in a beneficial way. For this purpose, you should consider high-quality measurement systems in combination with modern software solutions.
In addition, you should not disregard time synchronism. Especially in the area of scalability, PQIs are often not able to determine or even display current and voltage events synchronously in time. This prevents real-time data determination.