N-1 contingency analysis

EuroRing deliberately rejects gold-plated N-1 ("a financial black hole", §4.4). Security comes from two places instead: nominal + 1 spare graceful de-rating at the hub (a lost transformer trims a link to ~80%, it does not drop it) and network-level N-1 from the ring topology (a lost link re-routes the other way). A Type C local hub is a single-stub radial by design.

Meshed core (A+B)

EXPOSED

re-routes around the A–B mesh

Secure

graceful / re-route

Degraded

local island, core holds

At risk

radial stubs / root

Fast N-1 screen (GridSim LODF, linear)

The screen a control room runs continuously: using Line Outage Distribution Factors, it predicts — without a full re-solve — how each cable's flow shifts when every other cable trips, ranked by the worst resulting loading. A DC early-warning; the top entries are the ones worth confirming with the accurate AC re-solve below.

Outage (N-1)	Worst predicted loading	on cable	Screen
L3 France–United Kingdom	125%	L0 Ireland–United Kingdom	beyond emergency rating
L0 Ireland–United Kingdom	125%	L3 France–United Kingdom	beyond emergency rating
L9 Holland–United Kingdom	124%	L32 United Kingdom–Germany	beyond emergency rating
L32 United Kingdom–Germany	124%	L9 Holland–United Kingdom	beyond emergency rating
L5 Holland–Germany	112%	L32 United Kingdom–Germany	on emergency rating
L2 Ireland–Spain	91%	L3 France–United Kingdom	within limits
L11 Spain–Morocco	82%	L3 France–United Kingdom	within limits
L1 Ireland–France	79%	L3 France–United Kingdom	within limits

Solver-backed N-1 (live GridSim re-solve)

Not just "can we still reach it" but "does it still solve": each in-service link is taken out and the AC power flow is re-run over what remains. A connected outcome reports the worst post-contingency bus voltage and line loading; a link whose loss disconnects a hub is flagged islanded (graceful for a Type C stub).

Outage (N-1)	Outcome	Solve	Worst \|V\|	Worst loading	ΔLoss
L0 Ireland ⇄ United Kingdom	Thermal overload — 124% (beyond the 120% emergency rating)	converged	1.000	124%	+22.4 MW
L1 Ireland ⇄ France	Secure — ring re-routes within limits	converged	1.000	79%	+0.5 MW
L2 Ireland ⇄ Spain	Secure — ring re-routes within limits	converged	1.000	91%	+16.7 MW
L3 France ⇄ United Kingdom	Thermal overload — 124% (beyond the 120% emergency rating)	converged	1.000	124%	+46.4 MW
L4 Belgium ⇄ France	Islands radial appendage (graceful, by design) → Belgium	—	—	—	—
L5 Holland ⇄ Germany	Secure on emergency rating — 112% post-contingency (re-dispatch to relieve)	converged	1.000	112%	+13.7 MW
L6 Norway ⇄ Germany	Islands radial appendage (graceful, by design) → Norway, Sweden, Finland, Estonia, Latvia, Lithuania	—	—	—	—
L7 Denmark ⇄ Germany	Islands radial appendage (graceful, by design) → Denmark	—	—	—	—
L8 Poland ⇄ Germany	Islands radial appendage (graceful, by design) → Poland, Austria	—	—	—	—
L9 Holland ⇄ United Kingdom	Thermal overload — 123% (beyond the 120% emergency rating)	converged	1.000	123%	+21.8 MW
L10 France ⇄ Morocco	Secure — ring re-routes within limits	converged	1.000	78%	+5.3 MW
L11 Spain ⇄ Morocco	Secure — ring re-routes within limits	converged	1.000	82%	+3.6 MW
L12 Algeria ⇄ Morocco	Islands radial appendage (graceful, by design) → Algeria, Libya	—	—	—	—
L13 Tunisia ⇄ Morocco	Islands radial appendage (graceful, by design) → Tunisia	—	—	—	—
L14 Iceland ⇄ United Kingdom	Islands radial appendage (graceful, by design) → Iceland, Greenland, Canada	—	—	—	—
L15 Greenland ⇄ Iceland	Islands radial appendage (graceful, by design) → Greenland, Canada	—	—	—	—
L16 Canada ⇄ Greenland	Islands radial appendage (graceful, by design) → Canada	—	—	—	—
L17 Italy ⇄ France	Secure — ring re-routes within limits	converged	1.000	69%	+39.4 MW
L18 Italy ⇄ Morocco	Secure — ring re-routes within limits	converged	1.000	71%	+1.6 MW
L19 Greece ⇄ Italy	Islands radial appendage (graceful, by design) → Greece	—	—	—	—
L20 Croatia ⇄ Italy	Islands radial appendage (graceful, by design) → Croatia, Romania, Bulgaria	—	—	—	—
L21 Egypt ⇄ Italy	Islands radial appendage (graceful, by design) → Egypt	—	—	—	—
L22 Portugal ⇄ Spain	Islands radial appendage (graceful, by design) → Portugal	—	—	—	—
L23 Romania ⇄ Croatia	Islands radial appendage (graceful, by design) → Romania, Bulgaria	—	—	—	—
L24 Bulgaria ⇄ Romania	Islands radial appendage (graceful, by design) → Bulgaria	—	—	—	—
L25 Sweden ⇄ Norway	Islands radial appendage (graceful, by design) → Sweden, Finland, Estonia, Latvia, Lithuania	—	—	—	—
L26 Finland ⇄ Sweden	Islands radial appendage (graceful, by design) → Finland	—	—	—	—
L27 Estonia ⇄ Sweden	Islands radial appendage (graceful, by design) → Estonia	—	—	—	—
L28 Lithuania ⇄ Sweden	Islands radial appendage (graceful, by design) → Latvia, Lithuania	—	—	—	—
L29 Latvia ⇄ Lithuania	Islands radial appendage (graceful, by design) → Latvia	—	—	—	—
L30 Libya ⇄ Algeria	Islands radial appendage (graceful, by design) → Libya	—	—	—	—
L31 Austria ⇄ Poland	Islands radial appendage (graceful, by design) → Austria	—	—	—	—
L32 United Kingdom ⇄ Germany	Thermal overload — 122% (beyond the 120% emergency rating)	converged	1.000	122%	+35.2 MW

Transformer bank contingencies

Element	Outcome	Effect	Rationale
United Kingdom — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Ireland — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
France — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Spain — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Belgium — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Germany — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Holland — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Norway — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Denmark — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Poland — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Morocco — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Algeria — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Tunisia — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Iceland — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Greenland — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Canada — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Italy — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Portugal — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Greece — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Croatia — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Romania — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Bulgaria — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Sweden — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Finland — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Estonia — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Latvia — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Lithuania — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Egypt — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Libya — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).
Austria — any single bank	Secure	Affected link de-rates to ~80%; spare bank picks up	Nominal + 1 spare: a lost transformer trims a link's capacity, it does not drop the link (§4.4).

Cable link contingencies

Element	Outcome	Effect	Rationale
Ireland ⇄ United Kingdom	Secure	Ring re-routes the other way — no nation lost	Network-level N-1: power re-routes around the meshed core (§11.3). Remaining links carry the redirected flow.
Ireland ⇄ France	Secure	Ring re-routes the other way — no nation lost	Network-level N-1: power re-routes around the meshed core (§11.3). Remaining links carry the redirected flow.
Ireland ⇄ Spain	Secure	Ring re-routes the other way — no nation lost	Network-level N-1: power re-routes around the meshed core (§11.3). Remaining links carry the redirected flow.
France ⇄ United Kingdom	Secure	Ring re-routes the other way — no nation lost	Network-level N-1: power re-routes around the meshed core (§11.3). Remaining links carry the redirected flow.
Belgium ⇄ France	At risk	Islands Belgium	Type C local hub is a single-stub radial by design — no network N-1. Accepted graceful degradation, not a ring outage (§4.4).
Holland ⇄ Germany	Secure	Ring re-routes the other way — no nation lost	Network-level N-1: power re-routes around the meshed core (§11.3). Remaining links carry the redirected flow.
Norway ⇄ Germany	At risk	Islands Norway, Sweden, Finland, Estonia, Latvia, Lithuania	Loss disconnects the listed hub(s); mitigated at hub level by graceful de-rating, not by topological N-1.
Denmark ⇄ Germany	At risk	Islands Denmark	Type C local hub is a single-stub radial by design — no network N-1. Accepted graceful degradation, not a ring outage (§4.4).
Poland ⇄ Germany	At risk	Islands Poland, Austria	Loss disconnects the listed hub(s); mitigated at hub level by graceful de-rating, not by topological N-1.
Holland ⇄ United Kingdom	Secure	Ring re-routes the other way — no nation lost	Network-level N-1: power re-routes around the meshed core (§11.3). Remaining links carry the redirected flow.
France ⇄ Morocco	Secure	Ring re-routes the other way — no nation lost	Network-level N-1: power re-routes around the meshed core (§11.3). Remaining links carry the redirected flow.
Spain ⇄ Morocco	Secure	Ring re-routes the other way — no nation lost	Network-level N-1: power re-routes around the meshed core (§11.3). Remaining links carry the redirected flow.
Algeria ⇄ Morocco	At risk	Islands Algeria, Libya	Loss disconnects the listed hub(s); mitigated at hub level by graceful de-rating, not by topological N-1.
Tunisia ⇄ Morocco	At risk	Islands Tunisia	Type C local hub is a single-stub radial by design — no network N-1. Accepted graceful degradation, not a ring outage (§4.4).
Iceland ⇄ United Kingdom	At risk	Islands Iceland, Greenland, Canada	Loss disconnects the listed hub(s); mitigated at hub level by graceful de-rating, not by topological N-1.
Greenland ⇄ Iceland	At risk	Islands Greenland, Canada	Loss disconnects the listed hub(s); mitigated at hub level by graceful de-rating, not by topological N-1.
Canada ⇄ Greenland	At risk	Islands Canada	Type C local hub is a single-stub radial by design — no network N-1. Accepted graceful degradation, not a ring outage (§4.4).
Italy ⇄ France	Secure	Ring re-routes the other way — no nation lost	Network-level N-1: power re-routes around the meshed core (§11.3). Remaining links carry the redirected flow.
Italy ⇄ Morocco	Secure	Ring re-routes the other way — no nation lost	Network-level N-1: power re-routes around the meshed core (§11.3). Remaining links carry the redirected flow.
Greece ⇄ Italy	At risk	Islands Greece	Type C local hub is a single-stub radial by design — no network N-1. Accepted graceful degradation, not a ring outage (§4.4).
Croatia ⇄ Italy	At risk	Islands Croatia, Romania, Bulgaria	Loss disconnects the listed hub(s); mitigated at hub level by graceful de-rating, not by topological N-1.
Egypt ⇄ Italy	At risk	Islands Egypt	Loss disconnects the listed hub(s); mitigated at hub level by graceful de-rating, not by topological N-1.
Portugal ⇄ Spain	At risk	Islands Portugal	Loss disconnects the listed hub(s); mitigated at hub level by graceful de-rating, not by topological N-1.
Romania ⇄ Croatia	At risk	Islands Romania, Bulgaria	Loss disconnects the listed hub(s); mitigated at hub level by graceful de-rating, not by topological N-1.
Bulgaria ⇄ Romania	At risk	Islands Bulgaria	Type C local hub is a single-stub radial by design — no network N-1. Accepted graceful degradation, not a ring outage (§4.4).
Sweden ⇄ Norway	At risk	Islands Sweden, Finland, Estonia, Latvia, Lithuania	Loss disconnects the listed hub(s); mitigated at hub level by graceful de-rating, not by topological N-1.
Finland ⇄ Sweden	At risk	Islands Finland	Loss disconnects the listed hub(s); mitigated at hub level by graceful de-rating, not by topological N-1.
Estonia ⇄ Sweden	At risk	Islands Estonia	Type C local hub is a single-stub radial by design — no network N-1. Accepted graceful degradation, not a ring outage (§4.4).
Lithuania ⇄ Sweden	At risk	Islands Latvia, Lithuania	Loss disconnects the listed hub(s); mitigated at hub level by graceful de-rating, not by topological N-1.
Latvia ⇄ Lithuania	At risk	Islands Latvia	Type C local hub is a single-stub radial by design — no network N-1. Accepted graceful degradation, not a ring outage (§4.4).
Libya ⇄ Algeria	At risk	Islands Libya	Type C local hub is a single-stub radial by design — no network N-1. Accepted graceful degradation, not a ring outage (§4.4).
Austria ⇄ Poland	At risk	Islands Austria	Type C local hub is a single-stub radial by design — no network N-1. Accepted graceful degradation, not a ring outage (§4.4).
United Kingdom ⇄ Germany	Secure	Ring re-routes the other way — no nation lost	Network-level N-1: power re-routes around the meshed core (§11.3). Remaining links carry the redirected flow.

Hub contingencies

Element	Outcome	Effect	Rationale
United Kingdom (Type A root)	At risk	Whole-ring event — root and all pendants	Root loss is not a topology contingency: it is covered by the dual synchronous HQ and fail-safe withdrawal, not by N-1.
Ireland (Type B)	Degraded	Islands only this hub; the rest of the ring holds	A pendant hub's loss is local; the meshed core continues. Its nation falls back to its own generation.
France (Type B)	Degraded	Islands only this hub; the rest of the ring holds	A pendant hub's loss is local; the meshed core continues. Its nation falls back to its own generation.
Spain (Type B)	Degraded	Islands only this hub; the rest of the ring holds	A pendant hub's loss is local; the meshed core continues. Its nation falls back to its own generation.
Belgium (Type C)	Degraded	Islands only this hub; the rest of the ring holds	A pendant hub's loss is local; the meshed core continues. Its nation falls back to its own generation.
Germany (Type A)	At risk	Islands Norway, Denmark, Poland, Sweden, Finland, Estonia, Latvia, Lithuania, Austria	This hub is the sole path for a downstream hub; its loss islands the chain (roots-to-A rule).
Holland (Type B)	Degraded	Islands only this hub; the rest of the ring holds	A pendant hub's loss is local; the meshed core continues. Its nation falls back to its own generation.
Norway (Type B)	At risk	Islands Sweden, Finland, Estonia, Latvia, Lithuania	This hub is the sole path for a downstream hub; its loss islands the chain (roots-to-A rule).
Denmark (Type C)	Degraded	Islands only this hub; the rest of the ring holds	A pendant hub's loss is local; the meshed core continues. Its nation falls back to its own generation.
Poland (Type C)	Degraded	Islands only this hub; the rest of the ring holds	A pendant hub's loss is local; the meshed core continues. Its nation falls back to its own generation.
Morocco (Type A)	At risk	Islands Algeria, Tunisia, Libya	This hub is the sole path for a downstream hub; its loss islands the chain (roots-to-A rule).
Algeria (Type C)	Degraded	Islands only this hub; the rest of the ring holds	A pendant hub's loss is local; the meshed core continues. Its nation falls back to its own generation.
Tunisia (Type C)	Degraded	Islands only this hub; the rest of the ring holds	A pendant hub's loss is local; the meshed core continues. Its nation falls back to its own generation.
Iceland (Type C)	At risk	Islands Greenland, Canada	This hub is the sole path for a downstream hub; its loss islands the chain (roots-to-A rule).
Greenland (Type C)	Degraded	Islands only this hub; the rest of the ring holds	A pendant hub's loss is local; the meshed core continues. Its nation falls back to its own generation.
Canada (Type C)	Degraded	Islands only this hub; the rest of the ring holds	A pendant hub's loss is local; the meshed core continues. Its nation falls back to its own generation.
Italy (Type A)	At risk	Islands Greece, Croatia, Romania, Bulgaria, Egypt	This hub is the sole path for a downstream hub; its loss islands the chain (roots-to-A rule).
Portugal (Type B)	Degraded	Islands only this hub; the rest of the ring holds	A pendant hub's loss is local; the meshed core continues. Its nation falls back to its own generation.
Greece (Type C)	Degraded	Islands only this hub; the rest of the ring holds	A pendant hub's loss is local; the meshed core continues. Its nation falls back to its own generation.
Croatia (Type C)	At risk	Islands Romania, Bulgaria	This hub is the sole path for a downstream hub; its loss islands the chain (roots-to-A rule).
Romania (Type C)	Degraded	Islands only this hub; the rest of the ring holds	A pendant hub's loss is local; the meshed core continues. Its nation falls back to its own generation.
Bulgaria (Type C)	Degraded	Islands only this hub; the rest of the ring holds	A pendant hub's loss is local; the meshed core continues. Its nation falls back to its own generation.
Sweden (Type A)	At risk	Islands Finland, Estonia, Latvia, Lithuania	This hub is the sole path for a downstream hub; its loss islands the chain (roots-to-A rule).
Finland (Type B)	Degraded	Islands only this hub; the rest of the ring holds	A pendant hub's loss is local; the meshed core continues. Its nation falls back to its own generation.
Estonia (Type C)	Degraded	Islands only this hub; the rest of the ring holds	A pendant hub's loss is local; the meshed core continues. Its nation falls back to its own generation.
Latvia (Type C)	Degraded	Islands only this hub; the rest of the ring holds	A pendant hub's loss is local; the meshed core continues. Its nation falls back to its own generation.
Lithuania (Type C)	Degraded	Islands only this hub; the rest of the ring holds	A pendant hub's loss is local; the meshed core continues. Its nation falls back to its own generation.
Egypt (Type B)	Degraded	Islands only this hub; the rest of the ring holds	A pendant hub's loss is local; the meshed core continues. Its nation falls back to its own generation.
Libya (Type C)	Degraded	Islands only this hub; the rest of the ring holds	A pendant hub's loss is local; the meshed core continues. Its nation falls back to its own generation.
Austria (Type C)	Degraded	Islands only this hub; the rest of the ring holds	A pendant hub's loss is local; the meshed core continues. Its nation falls back to its own generation.