Martin Hochstadter was a German electrical engineer and the inventor of Type-H (or “metallized”) cable used for high-voltage power transmission.
Hochstadter worked for Siemens AG in Japan and then began developing Type-H cables in the United States in 1913 at Pennsylvania’s Standard Underground. He applied for a patent on this technology in the United States, but Siemens had filed a similar application in Germany.
Hochstadter’s cable was designed for circuits operating above two thousand volts. He installed a conductive shield around each insulated conductor to equalize electrical stress on overhead transmission lines and underground cables.
Siemens negotiated the rights to the patent outside of the United States, but found that the American standard, which used copper wiring, was not appropriate for European conditions. He worked with the Swiss aluminum industry to develop a metallized paper that would prove a complete metallic surface of the cores and allow the impregnation of the cable after its application. This cable greatly expanded the operating range of high tension cables from about 20,000 to 66,000 volts in the period from 1912 to 1924.
Acknowledging that greater capacity was needed, Hochstadter developed what became known as compression cables in the 1920s, which could handle 132,000 volts. These cables used mechanical pressure to expand the stresses that insulated cables could handle.