Mitigating the environmental impacts of substations and reserve power plants
Substation equipment contains insulating oil or SF6 gas. Large volumes of light fuel oil are stored at reserve power plants. Large tanks and items of machinery containing chemicals are located above shielding pools. This is to ensure that chemicals cannot pass into the soil or bodies of water in the event of a leak.
Substations and reserve power plants are unmanned, so it is important that the equipment and shielding pools are fitted with alarm sensors that alert the maintenance service providers in the event of a fault. They also inform the Main Grid Control Centre of any faults. Furthermore, all substations and reserve power plants have absorption equipment for emergency damage limitation.
We have prepared ourselves for the occurrence of fires by using retaining pools, which can be used to take the oily fire extinguishing water in a controlled way. The reserve power plants have comprehensive fire detection and extinguishing systems.
The reserve power plants burn sulphur-free light fuel oil, which causes CO2 emissions when it is used. The reserve power plants are only used in the event of a disturbance in the main grid and during trial runs to verify the readiness of the plants to be started. The trial run cycle and the length of the trial run are optimised to take the minimum length of time necessary to verify functionality. In the event of a disturbance in the power system, reserve power plants are used for as long as necessary to ensure the security of the power system.
The SF6 gas used in some substation equipment is a highly potent greenhouse gas. For this reason, it is only handled by trained personnel, and the equipment that contains SF6 is under strict leak control. The annual leakage rate has been very low over the long term, averaging less than 0.2 per cent, which is one of the best results in the international ITOMS comparison.
Fingrid’s vision is to be a pioneer in SF6-free technology. We aim to switch to SF6-free 110-kilovolt GIS plants by 2025. There is currently no alternative to SF6 gas at GIS plants with a higher voltage than this.
Some substation equipment emits a noise that sounds like a constant buzz. This is usually caused by transformers, compensators and reserve power generators. The noise is not usually audible far from the station, and the noise emitted by reserve power generators is temporary and brief. None of the noises emitted by Fingrid’s stations exceeds the guideline values for noise stated in Government decision 993/1992.
Fingrid endeavours to keep local settlements in mind when planning the locations of substations. Sound propagation can be reduced using structural solutions and by guiding the noise in a direction that causes less environmental disturbance. Noise level requirements are set for devices during the procurement phase, and, if necessary, noise modelling and measurement are also carried out.