Thanks to its chemical and physical properties, which make it an excellent insulator, the gas SF6 (sulfur hexafluoride) is used in several kinds of electrical equipment.

Some of the gas present in Terna’s infrastructure seeps out into the air because the gaskets do not seal perfectly, as well as sometimes when the pressure is being restored. SF6 is classified as a greenhouse gas. Therefore Terna plans to keep its leakage under control in order to contain and possibly reduce its incidence with respect to all the gas used .

Terna plans to gradually reduce the incidence of leakage with respect to the approximately 0.7% in 2007 and 2008, net of the effect of the incident at Tavernuzze. According to plans for the installation of new equipment, the expected reduction is 0.1% over a period of five years. There will be a contribution from the application of the new procedure for monitoring equipment, which will enable anomalous leaks to be detected and prompt and targeted measures to be taken. 

 Type of programme/initiative 2009  2010 

New procedure for monitoring leaks (1)
and reducing dispersion when pressure is being restored  

Application of procedures to all plants for the whole year


Integrated compact modules –
a set of different equipment with at least a 30% reduction of the quantity of SF6 needed for insulation
with respect to steel-clad uprights

After positive test results, equipment is considered an applicative standard and will be installed as necessary

Installation for the first modules to test performance 

Remote systems for
detecting gas leaks in equipment (2)
Installation on the 380 Kv
section in the Lacchiarella S/E completed
Results examined and widespread application assessed
New sealed transformers (TA)
or with max leakage of 0.1% a year
(high-reliability TA)(3)
Prototype trials completed positively and production start-up 

Plan to replace old equipment with new highly reliable ultra low leakage equipment

(1)The new monitoring system records the gas used and dispersed at each station. Until 2007, leakage was calculated using the total quantity of SF6 acquired, net of new installations.  

(2)Early detection by the remote maintenance centre of equipment where the pressure is decreasing anomalously allows targeted action to be taken on the equipment, while also avoiding shutting down the plant because of loss of insulation.

(3)The particularity of this initiative, undertaken after detection of leakage exceeding the declared threshold, lies in the current unavailability on the market of equipment capable of ensuring an extremely low level of leakage over time.