Power transformers, are basically used for stepping up& down the voltage levels. They are the primary equipment used in power transmission system. So it is primary to maintain all the transformers located geographically, but due to lack of man power it is impossible to monitor regularly. Due to these reasons, if a failure occurs in transformer may cause the network power shutdown. Though there are lot of protection measures that accompany a transformer, but by providing a online monitoring system will increase the reliability and reporting instantaneous fault confidently. This paper gives out the details in design and construction of an automatic monitoring system for power transformer parameters. A node-mcu module [esp8266] was enabled to monitoring of voltage, oil level and temperature (oil & winding) on a typical power transformer. With the internet of things (IoT), a self-defense system is designed and implemented for the transformer. In this system Transformer parameter are continuously marked and a graph is plotted. If the level of the parameter increases than the actual value, it gives buzzer alarm, if no action taken then the whole system will be tripped safely in power transformers.