These type of cable was invented by H. Hochstadter and hence the name is given the name is given. It consists of three cores and each core is insulated by impregnated paper of desired thickness. The insulation of each core is covered with the metallic screen which is made up of perforated aluminum foil. Cores are arranged such as a way that each metallic screen makes contact with each other. Additional conducting type is wrapped round all the three cores. Cable has no insulation belt, but provided with the lead sheath bedding armoring and saving as usual.
As all the four screen and lead sheath are at earth potential, the electric stresses are completely radial also the dielectric losses are reduced. another advantages of metal screen is that, heat dissipating capacity of cable increases and there are no sheath losses. Also ,the perforation in the metallic screen assist in the complete impregnation of the cable with the compound and thus the possibility of air pockets and voids in the dielectric is eliminated.
- The metallic screens assist in complete impregnation of the cable with the compound.
- The metallic screens increase the heat dissipating power of the cable.
- The lead sheaths in H type are thicker then S.L type cables