Hi @Miek I am not very familiar with data standards for power systems, but where does the common information model (CIM) for electric power systems fit? And did you look at the ontologies page on this site for clues? Also Medjroubi et al (2017)? HTH, R.
References
Medjroubi, Wided, Ulf Philipp Müller, Malte Scharf, Carsten Matke, and David Kleinhans (2017). “Open data in power grid modelling: new approaches towards transparent grid models”. Energy Reports. 3: 14—21. ISSN 2352-4847. doi:10.1016/j.egyr.2016.12.001.