Wind power and the national grid
The purpose of the national power system
The national power system is built to function reliably, efficiently and flexibly whilst responding to fluctuating electricity consumption. Finland’s electricity quality criteria ensure that local reliability is maintained when a new power plant is connected to the grid. In addition, the Finnish power system is capable of monitoring fluctuating consumption levels continuously at a national level, even in the event of a sudden disturbance. The organization responsible for the power system, Fingrid, is also tasked with ensuring that grid transmission capacity is sufficient for transporting large amounts of locally produced energy to wherever the electricity consumption is required.
Balancing and reserve power are required to ensure the system is functional. The main balancing power in Finland is hydropower or electricity purchased from neighboring countries. With the advancement of technology and electricity pricing, consumers can also play an active role in regulating the electricity system by for example by storing electricity in the battery of their electric car, when electricity is low due to abundant supply and limiting consumption when electricity demand id high.
In Portugal and Ireland, where wind power covers more than 25% of annual electricity consumption, the increased use of variable power has increased the use of balancing power. It is expected that also in Finland, additional construction of wind power will increase the use of balancing power and contribute to encouraging consumers to participate in flexible consumption.
The balancing and reserve power supply serves the entire electrical system, as well as all electricity producers. By adding or replacing small portions with different forms of production, the existing system can be used as it is.
All electricity producers and consumers connected to the grid have some effect on electricity quality. Good electricity quality means that the supply is uninterrupted, the electricity amplitude and frequency are stable, the waveform is a sine wave and the voltage level is appropriate.
Distribution networks are traditionally designed to transmit electricity from the substations to the consumers. When individual wind turbines or a small wind park is connected to a distribution network, it is important to ensure that the voltage stays within accepted values throughout the network and that network security functions correctly. In the event of a network fault, the wind turbine generator disconnects from the network automatically and stops production, so that it does not hinder the interruption of arc faults or continue electrification of an isolated part of the network, which would endanger returning the network to a normal state.
Transmission of electricity causes power losses. When wind turbines are located near consumers, less transmission is required and therefore power losses decrease.