Linear heat detectors are based on the physical principle that volume and pressure of a gas changes whenever its temperature changes. The detectors senses rate of rise of temperature and maximum fixed temperature in terms of pressure and trigger an alarm by combine signals of both parameters. The change in pressure is instantly registered by microprocessor electronic pressure sensor connected to the extremity of the tube. A copper sensor tube is laid along the circumference of the transformer and monitors surrounding temperature. Over heating of the transformer is measured within few seconds, which trigger an alarm and actuates the water spray system. Water spray system is provided with number of nozzles to cover the complete surface area of the transformer.