Electricity quality reflects two complementary measurements: the quality of voltage and continuity of supply.
Voltage quality can be affected by different types of disruption. It is important to draw a distinction between disruptions that are momentary, resulting from a one-time event (events affecting grid components, weather conditions, equipment damage, actions of third parties, etc.), and phenomena that continuously affect the nominal characteristics of the voltage wave, related to the operations of facilities connected to the grid or fluctuations in consumption and generation.
Continuity of supply is the grid’s ability to continuously supply power to all customer points of delivery. It may be affected by interruptions in supply or outages (for instance a lightning-related weather event). Continuity of supply is estimated based on Energy not supplied as a result of customer power cuts, expressed as a ratio to total annual power supplied by RTE to its customers and Ratio between the number of short or long outages and the number of distributors and industrial customer sites supplied by RTE. An outage is considered short if it lasts between 1 sec and 3 min and long if it lasts more than 3 min.