Protection technique based on parameter identification — its principle and application

A novel protection technique using parameter identification is proposed. According to the electric network theory, there are fixed relationships among the stimulated signals, the network parameters and the actual responses. This means that it is possible to identify the network parameters using measurement data from stimulation and network response. Any electric component to be protected can be considered as an electric network. When a fault occur, no matter inside or outside the component, the fault transient, i.e. response, can be used to identify the parameters. Comparing the calculated parameters with their normal values, the fault can be detected. Recent research indicates that some engineering problems in protection, such as the accurate fault location using local data, the instantaneous directional component, the fault identification of series compensated transmission lines and the fault line selection in the non-solid earthed network, can be solved by using the proposed principle. With the application of optical transducers, this protection principle could have great potential for practical applications.