An auxiliary power supply equipment for a high voltage installation 1, 7, 8 has a power source 3 at ground potential, a load circuit 4 at high potential, and a transmission link 5, 6 for coupling the power source to the load circuit. The power source comprises a high frequency voltage generator 31, and the transmission link comprises a first 5 and a second 6 current path. Each path is closed by capacitive coupling 51, 61, 61' to provide insulation between the ground potential and the high potential, and each current path has a reactive compensation means 52, 62, 53, 312, 63, 313, 62', 53', 412', 63', 413 for series compensation of reactive power generated by the capacitive coupling.