N-1 Criterion

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Definitions

European Definitions

ENTSO-E

(N-1)-Criterion: The rule according to which elements remaining in operation within TSO’s Responsibility Area after a Contingency from the Contingency List must be capable of accommodating the new operational situation without violating Operational Security Limits. [1]

(N-1)-Criterion means the rule according to which elements remaining in operation after a Fault of one element within TSO’s Control Area must be capable of accommodating the new operational situation without exceeding Operational Security Limits. [2]

National Definitions

Australia

N-x notation, where N refers to the number of elements in a part of the network and x is the number of elements that can fail at the same time without causing an interruption to power supply. [3]
For example, a network built to a strict N-1 standard will be able to supply peak load with one element not operating, even if it is the largest element in the network.

Belgium

N-1-criterium: het net moet nog kunnen worden uitgebaat na een onvoorziene uitschakeling van een belangrijk element, een productie-eenheid of een verbinding. [4]

Critère N-1: principe suivant lequel le réseau doit rester exploitable même lorsqu'il perd de manière imprévue un élément important, une unité de production ou une liaison. [5]

N-1 criterion: the principle that the grid must remain in operation even during the unscheduled loss of an important component, generation unit or connection. [6]


Chile

Se entiende por criterio N-1 a un estándar aplicable a las actividades de planificación y operación de los sistemas eléctricos, de manera que éstos puedan enfrentar la falla de alguno de sus componentes, sin que dicha falla genere una caída general del sistema, o provoque una operación de las instalaciones por sobre sus capacidades permitidas. [7]

Ecuador

Un sistema cumple con el criterio N-1 si al aplicarle la contingencia simple más severa, el sistema sigue en condiciones aceptables de funcionamiento considerando que los flujos en las líneas se mantienen dentro de límites normales de operación, los voltajes en las barras no superan sus niveles mínimos-máximos de variación, no existen actuaciones de protecciones y no existen desconexiones forzadas de carga o equipos. [8]

Greece

The N-1 criterion means that under all operating conditions the loss of any given element (line, transformer, Generation Unit, etc.) will not lead to operating constraints in adjoining operating zones as a result of limit values being exceeded for currents, voltage, stability or other system parameters and, will not cause interruptions in supply. [9]

Guernsey

“N-1” Security criterion requires that the supplier should maintain sufficient plant and importation facilities such that island maximum demand can still be met with the single largest source of electricity unavailable. [10]

Netherlands

(n-1)-criterium or "enkelvoudige storingsreserve": Bij volledig in bedrijf zijnd net moeten de door de aangeslotenen gewenste leveringen dan wel afnamen kunnen worden gerealiseerd onder handhaving van de enkelvoudige storingsreserve. [11]
Bij een enkelvoudige storing is een onderbreking van maximaal 10 minuten met een maximale belasting van 100 MW toegestaan.

(n-2)-criterium or "enkelvoudige storingsreserve tijdens onderhoud": Bij het voor onderhoud niet beschikbaar zijn van een willekeurig circuit, dan wel een willekeurige transformator, dan wel een willekeurige productie-eenheid, dan wel een grote verbruiker, moeten de door de aangeslotenen gewenste leveringen respectievelijk afnamen kunnen worden gerealiseerd onder handhaving van enkelvoudige storingsreserve. [12]
Hierbij hoeft alleen rekening te worden gehouden met de als gevolg van de leveringen dan wel afnamen optredende belastingen tijdens de onderhoudsperiode.

New Zealand

(N-‘k’) criterion denotes that the system is planned such that with all transmission facilities in service the system is in a secure state and for any ‘k’ credible contingency event(s) the system moves to a satisfactory state. If any further contingency events were to occur loads may have to be shed to return to a satisfactory state. [13]
The single contingencies to be considered under an N-1 criterion are:
  • loss of a single transmission circuit
  • loss of a single generator
  • loss of an HVDC pole
  • loss of a single bus section
  • loss of an interconnecting transformer
  • loss of a single shunt connected reactive component, e.g. capacitor bank, SVC


Norway

«N-1-kriteriet» betyr at utfall av en komponent, som for eksempel en linje eller en transformator, ikke skal medføre overlast eller svikt i det øvrige strømnettet. Dette er et planleggings-og driftskriterium som man tilstreber å overholde. [14]

Philippines

N-1 Criterion specifies that the Grid shall continue to operate in the Normal State following the loss of one Generating Unit, transmission line, or transformer. [15]

Switzerland

(n-1)-Kriterium: Bezeichnet ein Prinzip, dessen Einhaltung den sicheren Netzbetrieb auch dann gewährleistet, wenn ein beliebiges einzelnes Element des Systems ausgefallen ist. [16]

See also

  • [Offsite] Explanation by Idaho Power (USA) [17]

Notes

A more stringent criterion that considers simultaneous outage of two critical components (i.e. “N-2”) may also be adopted in critical parts of a power transmission grid that require a higher level of reliability.

  1. ENTSO-E Glossary
  2. ENTSO-E draft Network Code for Operations Security (2012)
  3. National Electricity Market (NEM) - Current transmission reliability and planning frameworks
  4. ELIA, Belgium
  5. ELIA, Belgium
  6. ELIA, Belgium
  7. Department of Electrical Engineering of the Pontificia Universidad Católica de Chile
  8. Análisis de contingencia del sistema nacional interconectado" Paredes, Masache y Mera. Páginas 4-5
  9. NERA OPERATING CODE: PLANNING CODE APPENDIX 2
  10. GUERNSEY ELECTRICITY SUPPLY - FUTURE STRATEGY, The Chief Minister
  11. Begrippenlijst, ACM, Nederland
  12. Technische publicatie TenneT
  13. Transpower Main Transmission System Planning Guideline
  14. [http://www.statnett.no/Global/Dokumenter/Milj%C3%B8%20og%20samfunn/Energiskolen/statnett_l%C3%A6rehefte_oppslag.pdf Energiskolen Lærehefte Stattnett]
  15. Grid Management Committee Philippines / Section 6.2.2.3 of the Philippine Grid Code
  16. Swissgrid glossary
  17. Idaho power explanation of N-1