Service continuity and quality are priority objectives for Terna: for the users of the transmissionElectricity transport and transformation activities along the interconnected high- and very high-voltage grid forthe purposes of delivery to customers, distributors, and recipients of self-produced energy. and dispatchingThe activity aimed at issuing provisions for the coordinated use and operation of production plants, thenational transmission grid, the grids connected to the same, and ancillary services of the electricity system. service, and more in general for the public at large, it is important that electricity is supplied without interruptionCondition in which the voltage of the terminals delivering electrical energy for a user is lower than 1% of therated voltage. and that the electricity supplied meets high quality standards.
For some time Terna has been monitoringAll the actions through which the current operational status of an electricity system is ascertained. the most important transmission service continuity indicators, and has set performance improvement targets. The tables below show the results achieved in 2006 and 2007, and the new targets for 2008. Since 2006, Terna has drawn up a plan to record also the quality of the electricity supplied. The parameters which Terna intends to monitor include, among others, frequencyThe number of oscillations per second, in which the value of the alternating current, such as voltage, variesfrom positive polarity to negative polarity. It is measured in Hertz (Hz).Fringe BenefitCompensation in kind, meaning benefits which do not consist in the payment of money, but the use of aservice or an object: such as the company canteen, lunch vouchers, company car or mobile telephone., range of voltage variations, and voltage dips.
In 2007, Terna implemented a measuring campaign by using 107 special measuring tools named Wally and placed along the EHV/HV systems and an additional 56 devices installed along sites of grid Users that participated in the voluntary campaign in compliance with art. 31.4 of AEEG resolution no. 250/04. The results of the 2007 campaign were analyzed and, with CESI’s support, helped the Authority draft a proposal for voltage quality indicators. The elementary and aggregated data were published in the web through the application named Monique to all Users participating in the campaign and to the Authority itself. The measuring campaign will also continue through 2008 also to better identify the electricity reference quantity.
The results of this exhaustive survey will form the basis for planningDefinition of the usage plans, for a specific period of time, for the available means of production andtransmission, in order to satisfy the energy requirements with respect to quality and continuity of service. the measures to be implemented for reducing voltage disturbances and for improving the efficiency of the electricity service.

Highlight: The crisis of the electricity system in Sicily



ASA - Average System Availability:

Defines the average availability for use of the electricity gridA group of plants, lines and stations for transferring electrical energy and supplying the necessary ancillary services. components in a specific period of time. This index can be expressed with reference to specific classes (for example voltage level), grid areas or, as in this case, the entire NTG.
The performance level obtained in 2007 is in line with the reference target



SAIFI + MAIFI - Short Average Interruption Frequency Index + Medium Average Interruption Frequency Index

An index of frequency of outages, calculated as the ratio between the number of customersBusinesses or distribution companies, wholesalers and the final buyers of electrical energy. involved in short outages (under 3 minutes) and long outages (over 3 minutes) and the number of users of the National Transmission Grid. Figures rounded off to the second decimal unit.
The performance level obtained in 2007 is in line with the reference target.



AIT - Average Interruption Time

Average interruption time of power in the Electricity System (NTG) in one year. It is calculated as the ratio between energy not supplied (ENS value) in a certain period and the average power absorbed by the Electricity System in the period under consideration. Figure rounded off to the second decimal unit.
The performance level obtained in 2007 is in line with the reference target.



ENS - Energy Not Supplied

Energy not supplied due to outages on the NTG in the period, for causes attributable to Terna. Figure rounded off to the unit.
In compliance with the terms envisaged by the Authority for Electricity and Gas in the AEEG resolutiono. 250/04, no. 79/05 and those that follow, starting in 2006, in the ENS calculation, the Relevant Incidents (Incidents involving an outage with 150 MWh of non supplied electricity lasting over 30 minutes, according to the definition of Relevant Incidents effective until December 31, 2007 and defined in the 2004-2007 regulatory period).
Previous years' values have been recalculated using the same method.
The performance level obtained in 2007 did not respect the reference target. The outages that occurred in the two following incidents had considerable relevance:
  • Area of Milan, March 5, 2007: outage that involved the AIR Liquide VR customer following a malfunction in the 220 kV(kilovolt=1,000 Volts) unit of measurement of voltage. Marcaria – Bussolengo line;
  • Area of Florence, February 12, 2007: outage of HV Users in the provinces of Grosseto and Livorno following a malfunction in the Suvereto electricity station.

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