The invention discloses a protection device and method for a metallized
film capacitor. The inside of the dry metallized
film capacitor is not potted or adopts a potted
dry structure, and a gap with certain height exists in the top of the
capacitor. The gas-sensitive protection device formed by a thermal conductive
hydrogen sensor and a detection circuit of the sensor is mounted at the top of the
capacitor. When an element in the
capacitor has a breakdown failure, a large amount of gas can be produced inside the element, escapes and can be gathered in the gap in the top of the capacitor finally. After the element produces the gas, the
hydrogen volume accounts for about 85% through detection, thus, the produced gas can cause the concentration of
hydrogen in the gap in the top of the capacitor to change, an output
signal of the detection circuit can change, and the internal failure of the metallized
film capacitor is detected. When a failure
signal is detected, a power supply of the capacitor can be
cut off from the outside, so that accidents such as capacitor explosions and the like caused by further development of the capacitor failure can be prevented, and failure detection and protection of the capacitor can be realized.