Capacitor Bank Protection

In general, higher than normal temperatures (from internal losses or external heating) will degrade dielectrics faster causing reduced capacitor life. Capacitor manufacturer should provide expected lifetime at specific temperatures.

Definitely one could provide temperature protection to Capacitors, but, for the capacity you have mentioned (50 kVAR), such a protection would not be cost effective. Normally 50kVAR capacitors are protected only with HRC Fuses, which are only for protection against Short circuits. That too, they cannot prevent short circuits, as they will respond only after a short circuit happens and high fault current flows. Fuses would only prevent spread of the fault damage.

Normally as per my experience there is a certain enclosure standards very for outdoor and indoor standards. You can see that the variation in temperatures create a lot of unbalance currents inside capacitors.

Does your installation is rated for outdoor use, normally outdoor use will have ventilation fans with an IP66 protection enclosure. if that is the case then the vendor is correct. otherwise the installation is not suited for such environments.

For longer life of the capacitors you want to keep them as cool as is practical for you situation. Temperatures above 45deg C are going to start causing problems. Many capacitors will blow soon after they have started to go over 55degC. Not much margin for Dubai. Fit a small evaporative cooler, like a BreezeAir with a thermostat to your installation, making sure there is ample roof ventilation if the units are indoors. The BreezeAir will work outdoors as well provided you duct the air onto the caps. Mind your flash distances. If you cannot get water to the installation you will have to go with an ammonia cooler or the likes thereof.

If your capacitor bank is enclosed along with the resistors.....well that's where the heat is coming from. Check that the cooling fans blow accross the capps first and then on to cooling the resistors.

I designed and built a system based on these principles for the Power Factor Correction buildings that housed the Capacitor Banks @ BHP Billiton's huge aluminium factory in South Africa. Eight years down the line they are running fine and have never had a cut-out because of temperature. The three buildings I cooled each generate some 700kW of heat and the custom designed evap coolers use less than 20kW of power in total to control the heat per building 24/7.

As others have said, generally no. Capacitors don't like heat and high ambient or running temperatures will dry them out and kill them very quickly. Check the data sheets for the capacitor bank again and see what ambient temperature they are designed for and the expected life time at the ambient temperature they are being subjected to in your application.

Before replacing the capacitor bank ensure that the capacitors are suitable for the application, otherwise they will likely fail in the same way after about the same time.

See posts above and other threads on CR4 on the subject.

Majid

These things have to be derated according to temp and other factors otherwise installation will be okay but after some time it will be mess .

But you can look ABB and schenider outdoor enclosures for rated temp above 50 degree you may need some extra cooling solution if it is some where in desert .