Service continuity and quality

Continuity is the most important parameter for measuring the quality of the electric service. All the segments of the electric system – generation, transmission, and distribution – contribute to the final result: to ensure the availability of electricity to society with interruptions below pre-established thresholds and appropriate standards of technical quality.

Service continuity is an objective that is also recognised by the Authority for Electricity and Gas (AEEG). For the period 2008-2011, the AEEG has provided an incentive scheme, in which Terna’s performance with respect to the set targets activates a mechanism based on economic rewards and penalties.

The indicators considered are the electricity not supplied and the number of outages per user, a composite indicator measured at the level of the single Regional Operating Areas. The economic effects of the incentive scheme will begin in 2010.

In 2009, Terna continued its campaign to measure the voltage data in its infrastructure through the monitoring network that has been in operation since 2006 and in cooperation with end customers and distributors.

 

AVAILABILITY INDICATOR (REAL AVERAGE SYSTEM AVAILABILITY - ASA)

AVAILABILITY INDICATOR (REAL AVERAGE SYSTEM AVAILABILITY - ASA)

ASA (Average System Availability)i
This defines the average availability for use of the components of the electric grid in a certain period. This index can be expressed with regard to specific classes (for example, by voltage level), grid areas, or – as in this case – the entire NTG.
The performance achieved in 2009 is in line with the target concerned.

CONTINUITY INDICATOR (SAIFI+MAIFI)

CONTINUITY INDICATOR (SAIFI+MAIFI)

SAIFI+MAIFI (Short Average Interruptioni Frequencyi Index + Medium Average Interruption Frequency Index)
This is an index of the interruption frequency, calculated as the ratio between the number of customers affected by brief outages (less than 3 minutes) and the number of users of the National Transmissioni Grid. The figure is rounded to the second decimal.
Terna’s performance in 2009 exceeded the target.

SYSTEM CONTINUITY INDICATOR (AVERAGE INTERRUPTION TIME - AIT)

SYSTEM CONTINUITY INDICATOR (AVERAGE INTERRUPTION TIME - AIT)

 

AIT (Average Interruption Time)i
This is the average time of interruption of the electric system (NTG) in one year. It is calculated as the ratio of the energy not supplied (ENS) and the average power absorbed by the electric system in the same period. The figure is rounded to the second decimal.
Terna’s performance in 2009 exceeded the target.

SERVICE CONTINUITY INDICATOR (ENERGY NOT SUPPLIED - ENS)

SERVICE CONTINUITY INDICATOR (ENERGY NOT SUPPLIED - ENS)

The 2008 value differs from the one that was published in the 2008 sustainability report, because it was recalculated in 2010 to include significant incidents caused by force majeure.

ENS (Energy Not Supplied)
Until 2007, the “Energy Not Supplied” indicator was used as an internal process indicator in order to continually improve the Company’s performance. This indicator regarded the energy not supplied to the users directly connected to the NTG because of events that concerned the NGT itself and did not consider the share that was due to significant incidents.
Since January 1, 2008, AEEG Resolution no. 341/07 has regulated the service quality provided by Terna through an incentive mechanism based on rewards/penalties, which redefined the ENS indicator. The new index also includes the energy not supplied to directly connected users because of events on other connection grids that are not part of the NTG, as well as a share of the energy not supplied because of significant incidents(1). The performance achieved in 2009 based on the new index exceeded the benchmark level.

(1) “Significant incident” is meant any interruption with more than 250 MWh of energy not supplied. The share that affects the ENS index is a percentage of the energy not supplied that decreases as the energy not supplied in a single significant incident increases