A circuit arrangement for voltage testing and for detecting partial discharges in a single-phase or polyphase medium-voltage or high-voltage installation, comprising - one or more conductor signal inputs (1 1, 1 2, 1 3), each of which is set up for coupling to a capacitive coupling electrode (2 1, 2 2, 2 3) which is coupled to a conductor (L1, L2, L3) of the single-phase or polyphase medium-voltage or high-voltage system, at least one voltage testing unit coupled on the input side to the or an associated one of the conductor signal inputs (1 1, 1 2, 1 3) of the circuit arrangement, which is set up for threshold-based detection of the voltage state with respect to the associated conductor, at least one partial discharge detector unit set up to detect partial discharges with respect to the or an associated one of the conductors (L1, L2, L3), which comprises a partial discharge detector circuit and a partial discharge display circuit coupled on the input side to a signal output of the partial discharge detector circuit, and - a power supply for the partial discharge detector unit having a first power supply circuit which is arranged to supply the partial discharge detector circuit with power from the or one of the conductor signal inputs (1 1, 1 2, 1 3) of the circuit arrangement, and/or with a second power supply circuit which is arranged to supply energy from the or one of the conductor signal inputs (1 1, 1 2, 1 3) of the circuit arrangement to the partial discharge display circuit, a partial discharge terminal path which is set up to couple an input side of the partial discharge detector circuit to an earth side of a system capacity (C S1, C S2, Css) electrically parallel to the capacitive coupling electrode (2 1, 2 2, 2 3). - one or more conductor signal inputs (1 1, 1 2, 1 3), each of which is set up for coupling to a capacitive coupling electrode (2 1, 2 2, 2 3) which is coupled to a conductor (L1, L2, L3) of the single-phase or polyphase medium-voltage or high-voltage system, at least one voltage testing unit coupled on the input side to the or an associated one of the conductor signal inputs (1 1, 1 2, 1 3) of the circuit arrangement, which is set up for threshold-based detection of the voltage state with respect to the associated conductor, at least one partial discharge detector unit set up to detect partial discharges with respect to the or an associated one of the conductors (L1, L2, L3), which comprises a partial discharge detector circuit and a partial discharge display circuit coupled on the input side to a signal output of the partial discharge detector circuit, and at least one voltage testing unit coupled on the input side to the or an associated one of the conductor signal inputs (1 1, 1 2, 1 3) of the circuit arrangement, which is set up for threshold-based detection of the voltage state with respect to the associated conductor, at least one partial discharge detector unit set up to detect partial discharges with respect to the or an associated one of the conductors (L1, L2, L3), which comprises a partial discharge detector circuit and a partial discharge display circuit coupled on the input side to a signal output of the partial discharge detector circuit, and - a power supply for the partial discharge detector unit having a first power supply circuit which is arranged to supply the partial discharge detector circuit with power from the or one of the conductor signal inputs (1 1, 1 2, 1 3) of the circuit arrangement, and/or with a second power supply circuit which is arranged to supply energy from the or one of the conductor signal inputs (1 1, 1 2, 1 3) of the circuit arrangement to the partial discharge display circuit,