Alternating current power measuring apparatus

An alternating current power measuring apparatus comprising:

• a first capacitance element having one end capacitively coupled to a conductor wire of a first electrical cable of a set of three electrical cables for supplying three-phase alternating current to a load and having the other end capacitively coupled to a conductor wire of a second electrical cable of the set of electrical cables;
• a second capacitance element having one end capacitively coupled to a conductor wire of a third electrical cable of the set of electrical cables and having the other end capacitively coupled to the conductor wire of the second electrical cable;
• a first voltage measuring part for measuring a first voltage which is a voltage of both ends of the first capacitance element;
• a second voltage measuring part for measuring a second voltage which is a voltage of both ends of the second capacitance element;
• a first current measuring part for measuring a first current flowing in the first electrical cable;
• a second current measuring part for measuring a second current flowing in the second electrical cable;
• a switching part for capacitively coupling selectively either of said the other end of the first capacitance element and said the other end of the second capacitance element to the second electrical cable;
• and
• a processing part which computes a first value by a multiplication among a proportion between a specified voltage value of a voltage applied to the set of electrical cables and an effective value of the first voltage, the first voltage and the first current, by measuring the first voltage and the first current with capacitively coupling said the other end of the first capacitance element to the second electrical cable by the switching part, and which computes a second value by a multiplication among a proportion between the specified voltage value and an effective value of the second voltage, the second voltage and the second current, by measuring the second voltage and the second current with capacitively coupling said the other end of the second capacitance element to the second electrical cable by the switching part, and which computes a power to be supplied to the load by the set of electrical cables by summation of the first value and the second value.