The large increase in solar and wind energy can cause voltage problems and grid disruptions. Many problems are behind the meter. “The electrification and large increase in solar and wind energy brings changes to the electricity grid. This can lead to more complexity and problems. In order to make a good analysis of the situation, data becomes much more important so that you know where the problems come from and what you can do about them,” says Arthur Hartsuiker, account manager at CN Rood power quality.
Power quality & problems
He outlines the problems that we will increasingly have to deal with. “Due to an increasing number of PV installations, you may experience an increase in voltage. If the voltage at the end of the line becomes too high due to the grid impedance, the AC connection of the inverter will switch itself off for safety reasons. The maximum voltage at which an inverter must switch off is 253 V (plus 10 percent of the nominal voltage). Increasing tension may have a number of disadvantages. It can lead to power loss in the conductors, loss of efficiency when the inverter switches itself off, the lifespan of the inverter may be reduced due to frequent switching off, and so on.”
Cause and responsibility
But what exactly is the cause and who is responsible? “The grid operator is responsible for the voltage. It must always remain 230 V plus or minus 10 percent. If the end user feeds back into the grid, he will not immediately be the cause of the voltage increase. However, if multiple parties - the entire district or neighborhood - feed back, the joint feed-in may lead to problems (high grid impedance) as the load on the line becomes too high. Since the network manager is responsible for establishing and maintaining the voltage, he will try to achieve a balance with the help of transformers. The transformer can be raised so that there is more power, but then there is a user at the beginning of the line who may have too high a voltage. Or the tension is turned down. But then the first end user will not receive - 10 percent of the voltage.
“At a certain point the grid operator can no longer do anything and is 'out of order'. The system no longer works, which means another solution is needed.” Zuckerman compares the problem to a water pipe. “If the water continues to flow, there is nothing wrong, but if you turn on the tap and on the other side you also turn on the tap, you will put pressure on the pipe.”
Super-harmonic
A second phenomenon or problem that can occur is super-harmonic distortion, which can lead to disruptions or damage to equipment. “So the normal tension is subject to extra tension. Poor power quality can therefore also lead to problems in electrical installations.”
Only when everything is added together does it become clear what is going on
Complexity
Voltage increases and super-harmonics can lead to problems in practice. But they are not easy to solve. “End users often do everything according to the rules. Installers as well. If you were to measure all the houses individually, you will see that everything is fine individually. Only when everything is added together does it become visible what is going on.” Measurement data is needed. Hartsuiker gives an example: “When an entire neighborhood with PV panels wants to supply energy back to the grid when the weather is nice, a PV converter will automatically switch off when the voltage is too high. The user who regularly encounters this can contact the installer and ask what is going on. This can monitor the voltage with equipment.”
“For example, if 257 V is measured on the line over a longer period, this can be passed on to the grid operator. NEN 1010 describes how long the increase in voltage is permitted. However, it is described in such a way that there must be a lot of complaints to go outside the standard. There is a bottleneck. There is a need for solutions to improve voltage maintenance and power quality on the electricity grid. But in order to take steps you will have to start measuring and monitoring.”
Private versus industry
However, Hartsuiker does not expect that private individuals will monitor. “If there is a problem, the grid operator will probably investigate what is going on and see whether a solution is possible. The issue is becoming more important for industrial companies. If an installer is approached by a large company, he can install a meter that permanently monitors the power quality. This also allows machine disruptions to be observed. This is also often the cause of a problem with power quality. Heavy machinery can cause lighting to flicker in the building or in other buildings in the vicinity. If that is the case, as an installer you can check whether the factory is disrupting the neighborhood so that measures can be taken.”
Growing problem
Hartsuiker expects that problems related to power quality will become much greater in the future. “The networks are increasingly burdened and we will have to be more critical about them. We not only have to monitor the grid, but also our own installations. Super-harmonics can cause a lot of damage to equipment and you want to prevent that. Measuring and monitoring is therefore necessary to determine what is going on. Many of the problems – about 80 percent – are behind the meter. Think of too much return, too heavy a load (demand) but also an unbalanced load. Such things will become more common in the future.”
Source: https://www.installationjournaal.nl/14590/power-quality-problems-achter-de-meter
Nederlands