1. A method for analyzing appliances in a power line network, comprising: obtaining, with circuitry, an electrical characteristic of the power line network using a sensor that is connected to the power line network, wherein the electrical characteristic is based on an injected test signal having a fixed frequency and variable line cycle position; extracting, with the circuitry, a line-neglecting feature from the electrical characteristic of the power line network; and detecting, with the circuitry, an appliance connected to the power line network based on the extracted line-neglecting feature, wherein the line-neglecting feature corresponds to the appliance connected to the power line network, and the line-neglecting feature is independent of influence of the power line network.