Flex›Source - Svk Om Ö-drift (2025)

Source - Svk Om Ö-drift (2025)

“Om ö-drift” — Svenska kraftnät’s authoritative web page on island operation as an electricity preparedness (elberedskap) measure. Published 2025-04-02. The primary public statement of Svk’s role, taxonomy, and technical requirements for ö-drift in Sweden.

Bibliographic information

Key content

Definition and framing

Ö-drift is defined as operating an area as an “island” with local electricity production, without connection to the wider grid. Svk’s framing is important: a national, interconnected electricity supply is the best outcome for Sweden. Ö-drift is explicitly positioned as a fallback measure for “riktigt svåra situationer” (genuinely severe situations) — prolonged transmission failures where national restoration plans cannot quickly restore the grid. It is not a normal operating mode.

Four-level taxonomy

Svk distinguishes four scales of ö-drift in Sweden:

  1. Transmission-based ö-drift — for restoring the power system when all of Sweden, or large parts of it, has lost power. Svk is responsible, in accordance with EU regulations (Black Start rules).
  2. Local/regional ö-drift — for a town, city, or municipality, or parts thereof. Svk acts in its elberedskapsmyndighet role: provides support, funding, planning guidance, and oversees testing. Scale: a single community, not a region.
  3. Small area / single facility — e.g., an agreement with the owner of a small hydropower plant to use it for a specific area or facility. Outside Svk’s primary responsibility.
  4. Individual building — e.g., solar panels combined with battery storage. Entirely outside Svk’s scope; questions directed to the local electricity company (DSO).

Svk’s elberedskapsmyndighet role (local/regional ö-drift)

For level 2 (local/regional), Svk can:

  • Financially compensate costs for maintaining ö-drift capability (förmåga)
  • Support planning (planering)
  • Support and fund testing/simulation exercises (provning)

Limitation: Svk can only decide on preparedness measures towards actors within the electricity supply chain. It has no authority over municipalities or other actors outside the electricity sector directly. This matters because effective ö-drift requires coordination with hospitals, water utilities, and emergency services — which Svk can only influence indirectly.

Technical requirements

For a local/regional ö-drift to function, the following capabilities must exist in the target area:

Core requirement — black start (dödnätsstart): The most essential prerequisite. There must be local generation capable of starting from a dead grid — i.e., without an external voltage reference to synchronize to. Without this, ö-drift is impossible. This is the binding constraint in most potential ö-drift areas.

Frequency and voltage regulation: Once the island is energized, load and generation must be continuously balanced to maintain 50 Hz and acceptable voltage. This requires controllable generation (dispatchable, ramp-capable) rather than purely variable renewables.

Weak-grid operation: An isolated microgrid operates as a svagt nät (weak grid) — very different from normal grid-connected operation:

  • Fault currents are much lower (≤2 p.u. from inverter-based sources vs. 6+ p.u. from synchronous generators)
  • Protection relay settings designed for normal grid operation may fail to detect faults in island mode
  • The DSO must operate and protect the grid under these abnormal conditions

Organizational capabilities:

  • A written ö-driftsplan covering all contingencies
  • Trained personnel (significantly more demanding than normal operations)
  • Clear governance: who is ö-driftsledare (island operation leader) and what authority they have

Limitations and uncertainties

  • Cannot fully test: a live drill replicating actual conditions is not possible without creating real outages. Testing uses simulations and partial tests.
  • Hard load prioritization: in most ö-drifts, only the most critical societal functions will receive electricity. Other consumers must have their own backup (generators etc.).
  • Cannot guarantee function: the combination of inability to fully test and the complexity of weak-grid operation means 100% reliability cannot be promised.

Process for live ö-drift

Three sub-processes: (1) Säkerställa tekniska förmågor — ensuring technical capabilities are in place; (2) Ö-driftplanering — developing and maintaining the plan; (3) Skarpt läge — executing when needed, following the plan, communicating with all stakeholders, and re-connecting to the national grid when possible.

Relevance

This source provides the policy and preparedness framing for island operation that the existing technical microgrid sources (Arholma, Simris) lack. The taxonomy clarifies that Arholma and Simris are level-2 or level-3 cases — local initiatives with DSO as ö-driftsledare — while Svk’s transmission-based restoration is a separate, system-wide function. The elberedskap funding mechanism (Svk compensates local capability costs) is not documented elsewhere in the wiki.