I believe you are referring to this source by Vattenfall, footnote, page 7: https://www.vattenfalleldistribution.se/globalassets/4.-var-verksamhet/projekt/samrad/overby-kungsangen/koncessionsansokan-maj-2025/bilaga-2.-mkb-overby-kungsangen-huvuddokument.pdf

This document confirms exactly what we are discussing about, operating, nominal and highest voltage for which this line is technically designed may differ with 138 and 145 kV being mentioned, but the last sentence cleary states, these lines will be referred to as 130 kV. Again I am just emphasising, we are talking about the same thing. You are talking about "operating" voltage while I am talking about the asset's voltage class or nominal voltage. No one's wrong here.

Thank you for your comments. I'd like to point out we're talking about the same physical system here - 130 kV and 138 kV refer to the same voltage class, just using different nomenclature. We are both right about the technical details; this is just a debate about which nomenclature to use in OSM. To clarify, I'm not downgrading any data, so please stay respectful before making such allegations.
According to Svenska Kraftnät's official documentation (https://www.svk.se/om-kraftsystemet/oversikt-av-kraftsystemet/sveriges-elnat/), Sweden's regional grid uses the 130 kV designation. Being an engineer myself, I am well aware that in operation, this could mean any voltage level close to this voltage class. Per OSM's voltage tagging guidelines (voltage=*#Nominal,_rated,_and_maximum_voltages), the system operator's designation should be used.
I would appreciate if you could share your source for the 138 kV specification so I can learn from you.

Some examples in the electricity sector: https://openinframap.org/#13.46/59.58128/16.45153

Appreciate your critical feedback, I am well aware of differences in operational voltage vs. nominal voltage. Now to my knowledge, transmission lines and substations are usually referred to by nominal voltage on maps. If you look at the entirety of the Swedish substations and lines, this particular entry is the only one labelled at 138 kV (as opposed to 130 kV). May I ask if you know whether this substation is different from all the other 130 kV substations?