The reinforcement of high voltage electric power cables is a promising application field of the composite wires. The temperature of the power cables can reach 200-300 °C due to an over-loaded electrical grid. The composite wires have to stand these high temperatures for a long time in the power cables. Long term heat treatments have been done to examine the eligibility of the composite wires. After heat treatment impact test was applied to measure the changes of the mechanical properties of composite wires. With the instrumented impact tester the process of the failure was examined. In this paper the continuous production method of ceramic fibre reinforced metal matrix composite wires and their properties are shown.