National Grid (NG) manages many oil containing assets and oil storage is susceptible to leakages. The use of alternative insulating fluids in transformers has been studied by NG and synthetic esters are now considered where enhanced fire safety and a more environmentally friendly solution is required. NG currently uses Bund Water Control Units (BWCU) and oil separators to capture oil, both of which require maintenance and are less effective to ester and emulsified mixtures. However, the existing oil capturing techniques used for mineral oil are not 100% effective with newer alternatives. This project looks at alternative oil capturing and bioremediation techniques with or without existing oil interceptors, with respect to the potential environmental implications based on typical pollution scenarios at NG sites.
Benefits
Benefits for this project include:
- Supporting NGET in reaching regulatory requirements for water quality with innovatice techniques
- Potential to increase biodiversity on substations with new techniques
- Provide a low energy and maintaince solution for oil remediation
Learnings
Outcomes
2024/25
National Grid sites are recognised to already integrate isolated SuDS features into drainage strategies. However, there is an opportunity to maximise their use by integrating SuDS management trains. SuDS add value when functioning as individual features, yet most SuDS schemes use a combination of SuDS components to achieve multifunctional design objectives for a given site, constituting a SuDS management train. Sites that pose a high risk of pollutions require careful consideration when designing a SuDS management train. It is imperative to determine the specification of pollutants present and their expected concentrations. Best practice recommends providing water treatment before incorporating vegetative components in a SuDS treatment train. Typically, this would entail the inclusion of an oil separator into a drainage network.
Additionally, maintenance considerations are a key part of the design process. All natural or manufactured SuDS components, including pretreatment and storage elements must be properly maintained so that the system continues to operate as designed. Failure to do so could result in harmful pollutants discharging into local watercourses or ground water. Therefore, maintenance should be factored in when making design decisions on the specification of SuDS to implemented on a specific site.
Recommendations for further work
An outcome of Phase 1 was a summary report which contained a series of recommendations, summarised as follows:
1) Baseline drainage performance monitoring programme
2) Amendments to National Grid technical standards – this is linked to recommendations for further work
3) Review of conditions and effectiveness of SGT containment measures
Lessons Learnt
2024/2025
The findings from the literature review, case study review and substation site visit have guided the following recommendations (detailed in the outcomes) for future phases of the project, these can be broadly categorised into three groups.
1) We should develop baseline drainage performance monitoring program
2) We should propose amendments to National Grid Technical Standards (TS 2.10.09 – Site Drainage).
3) We need to review of the condition and effectiveness of supergrid transformer (SGT) containment measures
Dissemination
An internal communications article was published to invite volunteer sites willing to run trials.
