EHT Power Transmission grid in the state of Kerala came into existence in 1940 at 66kV level in connection with the commissioning of Pallivasal Hydroelectric Project. 66 kV substations at Alappuzha, Mavelikkara, Kothamangalam, Kundara, Kalamasserry, Viyyur, Aluva, and Thiruvananthapuram along with the associated 66kV tranmission lines were commissioned in 1940 for evacuating power from Pallivasal Hydroelectric Project.
After fourteen years, 110kV grid came into existence in connection with the commissioning of Sengulam Hydroelectric Project. 110kV Substations at Sengulam, Pallom and Kundara and associated 110kV tranmission lines were commissioned on 26.07.1958 for evacuating power from Sengulam power house.
220kV grid came into existence in connection with the commissioning of Sabarigiri Hydroelectric Project and Pallom 220kV Substation is the first 220 kV substation in Kerala, which was commissioned in 1966. After few months, 220kV Substation, Kalamassery was commissioned.
400 kV substation, Madakkathara is the first 400 kV substation in Kerala owned by KSEB, which was commissioned on 30.01.1993, which was connected to the interstate transmission network at 400kV level.
33 KV subtransmission network was established in Kerala in the year 2000. 33kV Substation, Kurumassery is the first 33 kV substation, which was commissioned on 22.12.2000.