Another kind is steel pipe oil-filled cable, impregnant is slightly higher viscosity polybutylene oil, conductive line heart is solid, three insulated wire heart together in seamless steel pipe, tube filled with high pressure (generally about 1.5 million mpa, 15 atmospheric pressure) of impregnant, as the space between steel pipe and cable oil supply, and connected to the oil supply system. It has excellent electrical properties and mechanical protection, but the oil consumption is large, the joint is more complex, not suitable for high drop laying.