Quality of electricity supply
The Norwegian regulation of quality of supply (in Norwegian) applies to those who wholly or partially own, operate or use electrical installations or electrical equipment connected to the Norwegian power system.
Everyone connected to the power grid will influence the quality of the electricity supplied from the system to a certain extent. The term ‘quality of electricity supply’ includes continuity of supply, voltage quality and commercial quality, in terms of information on the level of continuity of supply and voltage quality to be expected.
Continuity of supply
Continuity of supply is the availability of electrical energy, measured by the frequency and duration of interruptions.
NVE has not set quantified requirements for the continuity of supply, but economic revenue regulations take the cost of the interruptions into account when deciding the income cap for network companies. Nevertheless, all network companies are obliged to fully restore the power supply without undue delay after an interruption. NVE may impose network companies to limit the consequences of interruptions.
Since 1995, network companies have been obliged to report interruptions above 1 kV to NVE. From 2014, interruptions on all voltage levels have been reported. NVE publishes an annual report where data on continuity of supply for each network company is presented. The network companies analyse all operational disturbances above 1 kV and report this data to the TSO, Statnett SF. The TSO publishes an annual report with data from these analyses, for voltage levels above and below 33 kV. All network companies use the national interruption reporting system FASIT (in Norwegian) for registration and reporting interruptions.
NVE considers the continuity of the electrical supply to be good. However, the continuity of supply is highly influenced by conditions in the surroundings, such as wind, snow, ice, thunderstorms, vegetation, birds/animals, etc. NVE does not exclude any exceptional events from the interruption data.
Voltage quality is a description of the applicability of electrical energy, and describes how the magnitude or waveform deviates from the ideal values. The voltage needs to be within a given quality to be useable and not cause damage to electrical equipment. Consequences of poor voltage quality include breakdown of equipment, reduced lifetime of devices and flickering in lighting.
The Norwegian quality of supply regulation includes minimum requirements for voltage frequency, supply voltage variations, rapid voltage changes, short and long-term flickering, voltage unbalance and harmonic voltages including total harmonic distortion (THD). If considered necessary, NVE may set minimum requirements for other voltage disturbances, such as voltage dips, voltage swells, transient overvoltage, interharmonic voltage and main signalling voltage.
Network companies have been required to continuously register dips, swells and rapid voltage changes in their own characteristic high and medium voltage network since 2006. In addition, from 2014, they have been obliged to register THD and flickering. From 2014, network companies have also been obliged to report the abovementioned voltage quality parameters (except rapid voltage changes) to NVE.
In the event of customer complaints regarding power quality, network companies have to make the necessary investigations in order verify compliance with the requirements according to regulations. If the complaint concerns voltage quality, on-site measurements must be made according to relevant IEC-standards. If the measurements prove non-compliance to limits set according to regulations, the network companies must identify the reason for this and who is responsible for the violation. Network companies cannot charge the customer for these investigations, if the complaint is legitimate. If the TSO or DSOs have carried out all the aforementioned investigations without reaching an agreement with the customer, the case can be brought forward to NVE for investigation.
Network companies are obliged to give information on given data for the quality of supply in their network within one month, upon request by current or potential customers. This data includes, amongst other things, results from registration of interruption data, analyses of operational disturbances and specific conditions in the network that could have an influence on the quality of supply for the customer.
Further details on the regulation of quality of electricity supply are described by the European energy regulators, in the CEER Benchmarking Reports on Quality of Electricity Supply.