Apps for electrical utilities are analysing the impact of prosumers on their network and come as handy tools in maintaining stability
Maintaining stability is one of the major challenges for electrical utilities in the field of renewable energy. At times, when consumption of energy is fine, we see raises and drops in the low voltage network due to energy producing sources — for example — wind turbines and solar panels (PV, photovoltaic) on the roofs of houses or at wind/solar parks. These so called “prosumers” cause instabilities in low-voltage distribution networks and need to be managed with efficiency. Special ‘Apps’ for fast and simple network impact analysis by network calculations, together with tools for planning and sketching of alternative solutions to solve such issues. These tools help utilities to fulfill their legal obligations in the context of renewable energy and help them perform network quality assessment for any new application to install a solar panel or equivalent device in order to improve the overall quality of the distribution network.
Together with EWE Netz GmbH, Germany’s fifth largest utility in the northern parts of the country, the apps for smart GIS through an easy-to-use interface with a Stop-Light Visualisation were developed. The aim of these apps is to support the assessment process of new prosumer applications to provide energy into the existing distribution network. The evaluation is done by means of voltage drop calculations without these Renewable Energy Sources (DERs) being active, or by calculating the raise in voltage level assuming that no one consumes energy and only the DERs produce energy. Based on Esri’s ArcGIS Server, these Apps enable a process of simulation for different network planning situations. The apps are built using a straight forward step-by-step approach. The results of any kind of assessment are presented in green-yellow-red colours to indicate further directions. In case critical values are superseded, an employee may defer the case to an expert who may perform more detailed simulation scenarios. Here, you may think of switch-order simulations, cable enforcements, or perhaps even the exchange of a transformer in a substation. Hidden under the user interface, such apps offer functionalities for server-based attribute editing and sketching of network planning objects in the GIS.
Upfront investigations are run in a sub-station to analyse the scenario and a tab is kept on — the number of service points and residents being served by a particular station; how much energy is being fed in to the low-voltage network; is the current transformer powerful enough to supply all necessary energy; how is the entire voltage drop over the entire feeder network, etc.
The Network Connection Assessment Apps, especially the NCA-Calculate App, takes all relevant GIS data through a feeder trace and transfers it into the network calculationsoftware package. The results are displayed in tabular formand on the map in stop-light colours. The user interface of these Apps is simple, straight forward and easy-to-learn
Apps supporting planning and simulation
The NCA-Plan App allows uncomplicated network analysis on the impact of a DERs in different alternative scenarios: Am I to encounter difficulties and outages with a
certain plan? The app enables a user to sketch new network elements, by means of an elegant gallery of predefined planning elements. The NCA-Calculate App brings in the newly-sketched network elements together with the existing network data and perform a network calculation to determine the impact of the planned and simulated new network. The network planner may even consider different measurements, for example, the stepwise increase of transformer levels. Alternatively, he may also enlarge the electrical capacity of the network by laying out an extra cable, which – of course – is a more expensive scenario. All actions are actually combinations of sketched planning elements that are “merged” with the existing network before performing the assessment calculations. And the results are visualised on the map in green-yellow-red colours.
In many occasions, it is a good option to switch parts of the network in such a way that the newly planned objects will be fed by another feeder in the network. The planning app can place such temporary switches and simulate their impact by performing a new network trace and a network calculation. Altogether, these apps bring quite complicated matters to the end user in an extremely easy way
Separating as-built network data from the planned network
Most utilities want to keep the as-built network data as they are. There is a daily process of updating this network data. Planning new networks will happen in a separate layer. The challenge is then, to bring as-built and planned network data together in order to perform the correct network traces and network calculations. The planning and calculation apps handles this by temporarily applying the planned features to the existing data. The result works as if someone was editing the data and performing a trace and doing a network calculation. This process is then ended without saving the data, and in this way keeping the as-built data unharmed. The calculation results for any electrical feeder may be presented in a tabular form or in the map. It is also possible to export the entire process into a nicely formatted report for later documentation of the different planning alternatives.
Such reports are documents that are associated to the planning project. In general, the planning project and its associated alternative scenarios are graphically presented on the map. This provides an overall overview to the network planner. The attached documents can be retrieved at any later point in time. Most likely a network planner will remove unnecessary planning alternatives.
As-builting planned network
Generally after doing your network analysis and simulations, the next phase that follows is the “as-builting”, when plans become reality. The NCA-Plan App provides some excellent tools to support this process. There is an entire suite of construction and dimensioning tools to project the new network into and on top of the existing network. The gallery of planning materials is extended for this specific purpose, enabling the user to pick materials from the utility companies Material Management System, most likely, containing Compatible Units (CU). The predefined attributes of these CUs are automatically set for all planning elements in the gallery of sketching tools. Attribute editing after sketching is always possible.
In this phase, a network planner will have many scenarios in parallel. He may also start a new scenario based on an existing one. For each scenario the Planning App will keep track of a detailed list of materials to be used, the so called Bill of Materials: how many meters of cable type so and so were designed and how many new devices were installed or old ones removed? Most of our utilities keep this material information in external system, for example — SAP. The NCA-Plan App allows reading relevant information from these systems. The bill of materials is also saved as a document that is permanently associated to the planning project and the as-built scenario. Such lists may be printed, but they can also be exported to any other office system, for example Microsoft Excel, and other softwares.
Arrival of data and requirements that apply to data?I
In order to be able to provide the necessary network information for any kind of network calculation, the data need to fulfill a minimal set of requirements:
• There is full network topology, including internals of stations
• All switchable devices in the network topology have correct normal position settings
• All DERs must be associated to a service point or other device in the network.
The built-in calculation engine performs its network calculations based on an Arc-Node-topology and a so called “Cable Book”, with important electrical properties of cables and devices being used in the calculation process.
Webservices and apps
All these editing, planning and simulation capabilities are actually based on Webservices using Esri’sArcGIS Server technology. AED-SICAD provides additional capabilities to these Webserviceswith the ArcFM UT Server. Over the last two years the UT Server was enhanced with Editing, Planning and Calculation capabilities that reside in the new Server extensions UT Server Edit, Plan and NCS.
EWE Netz GmbH staff have been using these capabilities since June 2012 in a production environment. The results are excellent: the “smartGIS” apps have helped to reduce the processing time of applications for renewable energy by customers drastically. This has led to less instability in the distribution network. The evolution of a project-based solution into a standard product enables many other utilities now to profit from this hard R&D effort. Server-based network planning and network calculation and simulation is now available for everyone.