NOVELTY - The apparatus has a voltage controller connected with an electrical installation for controlling voltage on the electrical installation independently of voltage supplied by the electrical installation. A portable training sensor is connected to an electrical appliance e.g. washing machine, and the electrical installation for recording appliance signatures of the appliance, where the signatures are obtained from electrical measurements of the appliance. A wired/wireless transmitter e.g. plug, transmits the appliance signatures to a load monitoring apparatus.    USE - Training apparatus for a load monitoring apparatus (claimed) to determine an operational state i.e. power/energy consumption, of an electrical appliance e.g. washing machine, TV and lamp such as fluorescent lamp and incandescent lamp, connected to an electrical installation powered by a power source in a home and a small-medium enterprise. Uses include but are not limited to a utility grid, local power generator, solar panel and battery of an electrical car.    ADVANTAGE - The appliance signatures and operational characteristic of the electrical appliance are independent of voltage fluctuations of a power source, so that reliable and correct attribution of an operational state to the electrical appliance is obtained when the voltage is kept at a constant level, thus reducing uncertainties of a match between the appliance signatures and the operational characteristics during comparison of the operational characteristic with the appliance signatures.    DETAILED DESCRIPTION - The appliance signatures are selected from a group consisting of current, power, electrical phase, admittance, transient characteristic and frequency spectrum. INDEPENDENT CLAIMS are also included for the following:    (1) a load monitoring system for determining an operational state of an electrical appliance connected to an electrical installation powered by power source, comprising a receiver    (2) a method for determining an operational state of an electrical appliance connected to an electrical installation powered by power source    (3) a computer program comprising a set of instructions for determining an operational state of an electrical appliance connected to an electrical installation powered by a power source.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a signature space of an appliance signatures for identification of operational characteristics of an electrical appliance.    Signature space (300)    Dimensions (301, 302)    Confined spaces (303-305)    Point (306)