Service continuity and quality

in

EU28

EU29

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

Terna has always monitored the quality of the service provided using different indexes, and identifies annual targets for improvement objectives. In the following pages we present in particular the performance of the reference indexes for the "quality of service and conduct of Terna NTG plants”, defined by AEEG Resolution No. 250/04 and the Terna Network Code.

It should be noted that the change in the indexes in the period considered does not reveal significant trends: in fact, each index moves within a very small range in ratio to the overall service measured. In addition, among the causes of change are both external factors, such as weather conditions, and events (for example faults) attributable to management of the NTG: the analysis of the latter non does not show systematic trends.

Since 2008 continuity has also been an objective encouraged by the Electricity and Gas Authority (AEEG), by means of a bonuses and penalties plan for performance with respect to pre-set targets. 

In 2012 the campaign to measure voltage quality data at Terna's plants continued, using the monitoring grid in service since 2006, in collaboration with the end HV customers and distributor companies. The devices installed on the grid provide important information on the quality of energy supplies.   

AVAILABILITY INDICATOR

Average System Availability (ASA)

Average availability of the electricity grid components for use in a given period. This index can be expressed with regard to specific categories (for example, by voltage level), grid areas, or – as in this case – the entire National Transmission Grid. The higher the level of the indicator, the better the service performance. The performance achieved in 2012 exceeded the target set.

AVAILABILITY INDICATOR

 

CONTINUITY INDICATOR

Short Average Interruption Frequency Index + Medium Average Interruption Frequency Index (SAIFI+MAIFI)
This interruption frequency index is calculated as the ratio between the number of customers involved in short (less than 3 minutes) and long (more than 3 minutes) interruptions, and the number of users of the National Transmission Grid. The lower the level of the indicator the better the service performance.
The performance achieved in 2012 was a little worse than the reference target (from 2012 the indicator also includes the Telat NTG).

CONTINUITY INDICATOR

 

SYSTEM CONTINUITY INDICATOR

Average Interruption Time (AIT)
Average interruption time of the electricity system supply (NTG) in one year. This is calculated as the ratio between the energy not supplied over a certain period (ENS) and the average power absorbed by the electricity system in the period in question. The figure is rounded to the second decimal. The lower the level of the indicator the better the service performance. The performance achieved in 2012 was better than the reference target (from 2012 the indicator includes also the Telat NTG).

SYSTEM CONTINUITY INDICATOR

 

SERVICE CONTINUITY INDICATOR

Energia Non Servita (ENS)
Up until 2007 the Energy Not Supplied indicator was used as an internal process indicator for the purpose of continually improving Terna’s performance.
This indicator regarded the energy not supplied to users directly connected to the NTG as a result of events that affected the latter and did not consider the shares caused by significant incidents(1).

Energia Non Servita Regolata (ENSR)
Since 2008, with its Resolution AEEG 341/07, the Authority has regulated the quality of the service provided by Terna through a mechanism based on incentives and penalties, which, among other things, adopted a new definition of the index. The new index also includes energy not supplied to directly connected users caused by events on other connecting networks that are not part of the NTG and a share of the energy not supplied because of force majeure events or significant events (1). The lower the level of the indicator the better the service performance. The performance achieved in 2011 exceeded the target set in terms of the new index.
The final calculation, by the AEEG, of the ENSR indicator for 2012 is not yet available.

SERVICE CONTINUITY INDICATOR

 

(1) A “significant event” is taken to mean any interruption with net energy not supplied exceeding 250 MWh. The share affecting the RENS index is a percentage which decreases as the energy not supplied during a single significant incident increases.