A Transformer Conservator Isolation Valve (TCIV) comprising an inlet conduit or pipe (2), an outlet conduit or pipe (5) connected to a rectangular housing (7) with an operating device (10) fixed on a shaft (19) placed inside the rectangular housing (7) and lever (9) for locking of the operating device (10); the said operating device (10) is provided with a sealing gasket (20) fitted such that during flow of oil due to rupture of electrical transformer tank or bursting of electrical transformer bushing or draining of oil swings towards the outlet conduit or pipe (5) so as to restrict flow of oil from the electrical transformer conservator (1) to the electrical transformer tank (4). A handle (8) is provided with the operating device (10) outside the rectangular housing (7) which when truned anti-clockwise during operation, causes the operating device (10) to swing toward the inlet conduit or pipe (2) so as not to restrict flow of oil from the electrical transformer Conservator (1) during filtration or filling or refilling. Two locking plates (13 and 14) are provided outside the rectangular housing.