Service quality

Service quality in 2009 recorded decidedly positive figures for Regulated Energy Not Supplied (RENS) and the Number of Supply Failures per User (NSFU), falling below the averages seen in recent years: RENS amounted to 796 MW, compared with a quality target of 1,425 MW; the NSFU value was 0.203, compared with a quality target of 0.231.
In 2009, only one significant incident attributable to Terna was reported, in the Naples area, in addition to an incident involving a 150 kV connection cable to the island of Ischia, which had only just been acquired from Enel Distribuzione (TELAT), and which triggered a significant outage on the island. Notwithstanding these incidents, the level of energy not supplied remained low.

Critical issues generated by causes not attributable to Terna included storms, strong winds and significant snowfalls between January and March 2009 in and around Turin and Naples, which led to an increase in the number of supply failures per user in these areas. No gas and water availability-related critical issues were recorded.

Although in line with the positive service quality generally, the larger islands continued to face their particular challenges connected with the structure of the transmission system.

In conclusion, the following are the four key indices of service quality and performance for Terna’s NTG systems, which are calculated in accordance with Resolution no. 250/04 of the Authority for Electricity and Gas and Terna’s Grid Code and which all show positive results:

  • AIT (Average Interrupt Time attributable to Terna) = 0.55 min/period; Annual national target = 1.00 min/year;
  • SAIFI + MAIFI (system and momentary average interruption frequency indices per user directly connected to the Terna NTG attributable to Terna) = 0.19; Annual national target = 0.22;
  • ENS (Energy Not Supplied attributable to Terna) = 330 MWh; Annual national target = 550 MWh;
  • ASA (Average System Availability of Terna network elements) = 99.034%; Annual national target = 99.05%.