12 secondary substations, 24 transformers of different types (including one variable), numerous sensors in the substations and supply lines with different measurement accuracy (including power quality measurements) as well as smart meters make up the basic infrastructure of the ASCR Smart Grid testbed. Furthermore, there are five grid storage systems in the substations with important functions both for the grid and the energy market. ASCR is investigating how to turn passive distribution network operations into actively managed smart grid operations.
Smart grids connect every player in the energy system via a communication network, thereby enabling prompt, bidirectional and cost-efficient communication between grid components, producers, storage facilities and consumers.
Smart grid migration path
The approach that has been adopted is based on the optimal use of existing copper reserves and the integration of smart ancillary technologies – not overnight, but continuously, along the smart grid migration path.
Phase 1 of the migration path is monitoring which sensors and which data are needed in which resolution. Phase 2 uses the sensors and pushes the equipment to its limits. Phase 3 is characterised by the efficiency gains from automation and active management.
Phase 1 – Measuring and monitoring the low-voltage network
While there are already suitable sensors and control systems at the level of high-voltage networks, these are still lacking in low-voltage grids. However, these make up the largest part of the electricity network and are the most active areas in terms of grid dynamics and fluctuating voltage. Now, for the first time, ASCR is recording comprehensive data in the urban low-voltage network on a large scale so as to make the grid status and utilisation at the low-voltage level transparent. Data capturing is carried out via smart meters and self configuring field sensors – including power quality meters (P855) or grid monitoring devices (GMDs).
How many sensors are needed?
A key issue for the ASCR research programme is to determine the minimum number of sensors required to provide a sufficiently detailed picture of how efficiently the network is operating and to aid network planning, whilst being mindful of the costs. The general rule is to use as many sensors as necessary and as few as possible.
Phase 2 – Low-voltage management with no active intervention
Further down the smart grid migration path, the data can be used to make management decisions that do not require any physical network expansion for the time being. They represent an efficient alternative to vague worst-case planning. Without active network intervention, specific network data enable infrastructure to be used closer to its physical limits and provides early warnings when thresholds or set KPIs (key performance indicators) are approached. In addition, the collected data/time series can be used to plan accurate expansion measures by means of relevant evaluations, extrapolations and simulations.
Phase 3 – Active grid management and automation
Active grid intervention can help to raise the efficiency of electricity network infrastructure. This, however, requires that the components are as fault-tolerant as possible and that they do not add significantly to overall cost during roll-out or operation.
Smart Grid testbed
The main components comprise:
Twelve prototypes of a smart grid station
24 transformers of different types (incl. one variable)
Five grid storage systems in the substations (120 kWh)
Fully equipped with grid monitoring devices (around 90 units)
Two construction fields with smart meters (over 500 units)
To simplify the visual processing of the network status, vectors of different grid parameters are calculated and presented in the “grid fingerprint”. Just as with a fingerprint, every network status and all network behaviour have a different pattern. Time and local differences, and the interplay between the battery storage system and grid activities, are very easy to see.
Monitoring reactive power
The monitoring of critical thresholds (shown in the figure to the left as reactive power) is a key factor of network operations. In the future, there will be an increased number of smart meters and other sensor technology in order to identify and handle critical consumption data. By comparing different time periods, ASCR is exploring whether thresholds are breached in the grid so as to optimise network operations. Major deviations are immediately visible.
Interim results in the Smart Grid research area
Existing battery storage systems are not yet compatible with grid technology. Questions are being asked of producers.
For much of the analysis, the 15-minute effective averages offer a sufficient insight into the distribution network. However, minimum and maximum values need to be stored.
The economically important factor driving the implementation of a smart grid is avoiding power outages (already at around one minute every year).
Vienna’s network has shown itself to be very robust, meaning that a flexibility operator is only needed in exceptional cases.
Early results show that, at individual connection points, reactive power breaches thresholds.
A distinction can already be made between consumption curves for normal operations and exceptional situations.
Characteristic failure patterns in smart meters can be read from the data flows.