Tin-accompanied and true ternary fission of $^{242}$Pu

True ternary fission and Tin-accompanied ternary fission of $^{242}$Pu are studied by using Three Cluster Model. True ternary fission is considered as formation of heavy fragments in the region $28\leq Z_1,Z_2,Z_3\leq 38$, with comparable masses. The possible fission channels are predicted from potential-energy calculations. Interaction potentials, Q-values and relative yields for all possible fragmentations in equatorial and collinear configurations are calculated and compared to each other. It is found out that ternary fission with formation of a double magic nucleus like $^{132}Sn$ is more probable than the other fragmentations. Also the kinetic energies of the fragments for the group $Z_1=32$, $Z_2=32$ and $Z_3=30$ are calculated for all combinations in the collinear geometry, as a sequential decay.