The modern and luxurious life styles with the increased automated machinery and devices have increased the demand for electrical energy. This has been one of the primary reasons to maintain prescribed standards in the field of electrical energy in terms of reliability, power quality, and stability of power system network. When such highly interconnected power system network experiences a disturbance like unbalances in load, frequencies, unnecessary tripping, or due to some external causes, it leads to unsynchronization with power grid effecting a massive damage to economy of the country. So it is important and necessary to have high secured power system. Even though Indian power system is well equipped, well designed with protection system, a massive power outage has been taken place in Mumbai in October 2020 leaving many areas affected. This paper describes a detailed study on Mumbai power outage 2020.