According to the USA Department of Energy, California lost about 19.7 x 109kWh of electrical energy through transmission/distribution in 2008 (6). This amount of energy loss was equal to 6.8% of total amount of electricity used in the state throughout that year. At the 2008 average retail price of $0.1248/kWh, this amounts to a loss of about $2.4B worth of electricity in California, and a $24B loss nationally. It is commonly accepted among electrical utilities that resistive loss ranges between 1.9% and 2.8% over 1000km. These losses are fixed and depend on wiring configuration. Corona losses, on the other hand, range between 0.083% – 3.66% depending on power line properties & environmental factors (7). Although energy losses due to corona sum up to considerable figures, the main losses involved with corona are those resulted from its atrocious effect on the electrical elements and in particular on insulation material.
As an active ageing factor corona accelerates electrical and mechanical deterioration processes and is considered to be a major ageing factor. Corona activity creates corrosive substances, like nitrogen oxides and ozone that compromise the electrical properties of insulators. Nitric acid derivatives corrode metal end fitting and erode concrete fillings of porcelain insulators affecting the mechanical strength of these components. Corona leads to loss of hydrophobicity, and is therefore lethal to NCI. The outcome emitted ultraviolet radiation dries insulation and changes its chemical properties. The level of corona discharge may change from time to time according to humidity (increasing at higher humidity) and air temperature. However, corona problems are not problems that sort themselves out on their own. They always worsen with time. The first step to care about corona is to locate it by using a UV imager corona camera.
Electrical losses due to corona discharge and to corona related failures can be reduced to minimum through preventive and predictive maintenance scheme that makes use of combined imaging technologies, such as IR, Visible and UV.