Raising energy transfer in corridors constrained by voltage instability-Statnett case

Statnett SF (The Norwegian Power Grid Company) is seeking new technologies to raise their grid energy transfer limits. One technology ABB is developing utilizes local measurements to assess proximity to voltage collapse. Statnett has conducted a joint computer simulation study with ABB and SINTEF Energy Research. A frequent problem for the Nordic power market is the limited power transfer capability to Sweden along the Hasle corridor. This limit caused a negative economic impact of approximately NOK 27M or USD 3.5M in the first 8 months of 1999. Power transfer corridor limits are usually determined prior to operation, and thus the limits may be set conservatively because of insufficient knowledge of the actual operating conditions, e.g. regarding proximity to voltage collapse. When using an advanced online sensor, the true transfer limit may show to be much greater than the existing conservative limit. When linked with dedicated system protection schemes, such as load shedding in the Oslo area, this sensor can raise the limit even further by quickly shedding load in the event of a contingency.