Information Redundancy And Information Identification In Smart Protection

The application of distributed parallel computing technology has provided an effective way for the function cooperation in smart protection, and the rapid development of smart substation and modern communication technology have provided an achievement way for the redundancy information collection in smart protection. Research about the cooperation protection method and multi points’protection algorithm are the new trend in the future.In the existing smart protection schemes, the protection methods adopt the source data based on the peer to peer communication technology, in this case, if the device fails or the data loss, the protection function will not be achieved. In order to improve the reliability of protection schemes, this paper proposes an optimization program based on the following three methods:protection function decentralization, diversified information acquisition, data processing parallel. Analysis shows that the optimization scheme can effectively improve the protection performance on the conditions of equipment failure and data loss, increasing the reliability of the protection scheme.Based on the above cooperation protection scheme, we studied some substation area backup protection based on the voltage\current information. Currently backup protection of digital substation adopts the traditional way of action which is complex in the timeline and set value. This paper proposed four substation area back up protection algorithms based on the integrated impedance, energy conservation law, phase related current differential and DCT method using the redundant information. Then, we use PSCAD/EMTDC to build a220kV substation model, the simulation results show that the method could be set easily and could select phase naturally, the phase related current differential is sensitivity to the substation area current differential protection, and it can also identify the CT saturation when external faults occur.We also researched about the substation area backup protection based on the protection statues information. However, wide-area protection system needs to use information from a number of substations. Therefore, communication’s reliability requirement is high. To ensure reliability of the information transmitted between substations, this paper presents an encoding method based on compressed sensing (CS). This method creates sparsity for the data to be transferred and maps the information to the frequency domain before transmission. At the receiving end, an orthogonal matching pursuit (OMP) reconstruction algorithm is used to reconstruct the original information. The simulation results show that even with the worst case bit change, or when the communication channel has noise, the normalized root mean square error (NMRSE) is still acceptable. The method simplifies the encoding and decoding complexity, greatly improves efficiency. On the other hand, the protection algorithm also needs high error tolerance capability. In case of data errors, it can still be able to correctly determine the faulted zone. This paper proposes a novel fault detection and recovery algorithm based on the theory of compressed sensing. The algorithm uses system-wide secondary protection information as features of different faults to build a training set, then solves the coefficients of the new predicted fault in the training model by compressed sensing, finally the redundancy minimum error is the correct fault classification. The simulation shows that in case of data errors, it can still be able to identify the classification.