dLab supervises one of Sweden’s largest PV power stations
Outside of Sjöbo municipality in the very south of Sweden, one of Sweden’s largest PV power stations are located, with an installed capacity of 12 MW, and contributes with an annual power production reaching 19 GWh. The solar park is connected to one of Sjöbo Elnät’s primary substations, which has been supervised by dLab’s application for disturbance analysis for several years. For some time now, the station has also been monitored using dLab’s application for analysing power quality, power flows and load. In what way does the solar park affect Sjöbo Elnät, and in what way can dLab’s platform assist?
It is a mandatory principle of Svenska Kraftnät (national grid operator, SvK) that each distribution system operator must regulate their reactive power balance. And according to SvK, connecting distribution system operators do not always have knowledge of how a zero exchange can be achieved due to a lack of knowledge about where reactive resources are located in their own power grid (*).
Due to the solar park, Sjöbo Elnät as an entity alternates over time between being a consumer and a net exporter of active power. The variation between the import and export is significant, which in turn creates a challenge to maintain a steady voltage level. A situation that makes it crucial to not only get a detailed overview of the load in the transformer bay, but also in the bays where different distributed energy resources supply power.
Furthermore, the solar park affects the reactive power flows in the distribution grid, where the park at high production consumes some reactive power but at the same time relieves the rest of the network, which in turn can generate higher reactive power flows from other cables. In Sweden, high reactive power flows pushed to overlying grid can result in high costs (penalties).
– Adding a large solar park to our grid where we already have rooftop solar power installed on residential buildings, a wind park etc., increases the urgent need for us to get our power flows under control. To accomplish this, we need a system that measures relevant data continuously and often, and we need actual values from all feeders. And of course, we need to easily be able to access all data and analysis, something we see that dQuality with dInsight provides, says Per Liljenberg, Grid Engineer Sjöbo Elnät.
Sjöbo Elnät has throughout the years continuously weatherproofed its grid, and today the grid consists almost exclusively of underground cables which further adds to the equation with reactive flows that vary over time and with the load.
The situation is clearly becoming increasingly complex where these power flows, active as well as reactive, cause several challenges. Perhaps the most critical is related to maintaining a steady voltage level, as voltage regulation itself becomes a much more complex issue.
A photovoltaic power station with large production capacity also induces risks for unwanted islanding in the event that the electricity power at the feeding point from the overlaying grid is lost. With the help of dLab, a high-quality risk assessment can be made.
In what way will dLab’s dInsight Analytics Platform help?
In dLab’s platform, the DSO receive continuous aggregated 10-minute values with actual measurements of load and power flows from each individual feeder, data that is very easy to follow over time to, for example, gain a deeper insight of how load situations vary and how it affects power flows.
The information from dLab facilitates for effective investigations and planning of appropriate measures. Grid operators will be able to:
• make high-qualitative risk assessments and understand how e.g. a change in switching state can affect the situation for the better or worse.
• understand where reactive flows originate from, what can be done, etc.
• know whether there in-fact is a zero exchange at the connection points to overlying grid and production sources, or how close they are to the limit.
• easily follow the voltage levels, voltage variations and voltage unbalance
• understanding the load
All in the same view!
As a bonus, increased activity in the voltage regulation affects the wear-and-tear patterns of the on-load tap changers, which can also be analysed by dLab’s application dState.