Farhad Yazdi

Dissipation factor of capacitors  is a function of temperature and frequency (of supply voltage). In the other words, capacitors’ losses vary with temperature and frequency. Dissipation factor of capacitors has three additive components. The first and second components are related to changing of capacitors’ parallel and series (ESR) resistances due to temperature. Since both of these resistances increase with temperature, so these two components always are positive. The third component is related to intrinsic characteristic of dielectric material. Dielectric dissipation factor may increase, decrease or even remain constant with increasing temperature. So, cleverly choosing of film capacitors may decrease the probability of capacitor overheating and extends its overall life.

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In studying of losses in power systems, often spoken that power loss decrease is proportional to the inverse square of system voltage increase. For example, if the voltage is doubled, the losses will be a quarter. It should be noted that this conclusion is correct only when that after increasing the line voltage (and so reducing the line current) conductor cross section remains the same as previous. But this assumption is unreasonable and unwise, because conductor cross section must be chosen based on current amount.

It is a well known relationship that conductor cross-section and the energy loss is proportional to the square of the current. So, if we assume that the correct  conductor cross sections is chosen, the following conclusions can be found (in the case of system voltage increasing) :

1 -Because the conductor cross section will reduce proportional to the current decreasing, the costs of conductors  purchasing will reduce also. Instead,  the cost of the conductors insulating will increase with voltages increasing.

2 – With assuming that the conductor cross section is chosen based on nominal current, then the loss will be proportional to the voltage inverse (instead  of the inverse square of voltage).

For example, with doubling of the line voltage, conductor cross-section and the energy loss are both reduced approximately to half (there are other parameters that complicate heat transfer conditions and so we say conductor cross section approximately will reduce to half).

Astronomical  clocks, unlike photocells, control street  lighting based on  time of sunrise and sunset which  is calculated based on  latitude and longitude of  the  street. This equipment has a  main advantage in respect to photocell which is reducing on-time and off-time errors caused by contamination of the opaque cover of the photocell.

In inspecting one of the pilot projects, accidentally i turned my  thermal imaging camera on one of  these astronomical clocks (which was installed in the distribution substation) and saw the below image!

This picture reminds me a report that has presented in a loss reduction conference in Madagascar island . In this report, noted that after two years of  executing loss reduction projects  in an African country , studies show that energy losses increased 1% !!!!!!!

Schneider Electric, announced an expanded curriculum, additional languages and education credits, for its vendor-neutral, online educational community, Energy University™. Designed to provide the fundamentals needed to implement successful energy efficient solutions, Energy University has seen more than 21,000 registered users since its launch in June 2009. Twenty-one new courses have been added to the curriculum in 2010 to increase the educational offering to 34. Courses are available in multiple languages – English, German, and Spanish, with French, Italian, Brazilian Portuguese, and Russian launching later this year. Additionally, Energy University has now launched a fully translated version of the site in Chinese, making this the first online energy efficiency program available in that country.

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May targeted subsidies in electricity sector result more non-technical losses?