Have you ever heard of mineral-insulated cables? They only consist of two materials: Copper conductors, magnesia oxide powder as an insulant and the outer sheath being made of copper again. Since the melting temperature of copper is 1083°C and nothing happens to a mineral material like magnesia oxide up to such temperature, nothing will happen to the whole cable. It even survives a fire, while a so-called fire resistant cable made of special plastic materials only just remains functional for 30 or 90 minutes, respectively, under standardised test conditions which need not necessarily match those in a real fire very accurately.
Adding to this, the outer sheath has a greater cross section than the conductors and therefore can – and should – be used to provide an excellent equipotential bonding system with a very low impedance, simultaneously saving one conductor.Log in to post comments