Overheating and Fire Hazards in Capacitor Banks

Overheating of capacitor banks is a common problem in reactive power control systems, and these systems are an essential part of electric distribution and transmission. It may occur due to inadequate ventilation, loose connections, bad design, or the overvoltage during lower demand period. Moreover, the capacitor lifetime depends directly on the operating temperature hence an overheating will lead to a faster aging. 

The main reason for a burning or even exploding capacitor bank is the liquid-filled capacitors, or the plastic parts that are combustible. If the temperature rises, the capacitor can cause a fire, a life-threatening situation, and economic loss.

One of the simplest and most affordable solutions to prevent overheating or explosion of the capacitor bank is the visual Fire Prevention Thermolabels (vFPT) from Streamer Electric AG. vFPT helps maintenance personnel understand the condition of the equipment, not only at the time of inspection, but also if the equipment has reached a certain temperature in the past. This temperature history is not available when only thermographic inspections are performed. These temperature labels are easy to install. The user just needs to stick them on the surface of any electrical equipment. An example of installation is shown in the picture 2. When the sticker reaches the activation temperature (70, 90 or 110 °C) the white strips irreversibly change color to black.

Picture 1 – vFPTs with activation temperatures 70, 90 and 110 °C

Picture 2 – Installation of the vFPTs on capacitors

Such an easy solution can help in prevention of the capacitor overheating and explosion. If you are interested in this problem, you can read an article from Allianz Global Corporate & Specialty (AGCS). They also give some advice on the capacitor bank design, way of installation, maintenance, and protection of capacitors.