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Recently, smart grid is considered as the next generation of power grid by introducing information and communication technologies. Line-loss is an important synthetic indicator which can directly reflect the energy efficiency and power management level of smart grid enterprises. In order to obtain all residential areas, line-loss requires obtaining electricity consumption of each user. However, data about users’ electricity consumption could reveal sensitive information; a sophisticated adversary can use some data analysis methods to deduce economic situation, habits, lifestyles, etc. In order to solve the problem, we propose an Efficient Privacy-preserving scheme for Line-loss Calculation, named EPLC. In our scheme, a data item is reading from one smart meter which implies the energy consumption in a time period of the user who owns it, and each user lives in a residential area. For each user, we encrypt user’s data based on Paillier cryptosystem by using two Horner parameters, by leveraging homomorphism, and each residential area gateway calculates relevant data about corresponding line-loss and control center hides the area-level polynomial into the final output for representing line-loss of all residential areas which are both in the form of ciphertext. Finally, we can still recover each residential area line-loss with possessing private keys and Horner parameters. Moreover, EPLC adopts the batch verification technique to lower authentication cost. Finally, our analysis indicates that EPLC is not only efficient but also can protect individual user’s electricity consumption privacy, and the flexibility and expansibility of EPLC are very suitable for smart grid.

Taking a high speed on-off valve as an example, the effects of air gap, shell thickness, armature length, guide sleeve type and armature radius on the electromagnetic force performance are studied. The results show that the air gap is negatively related to the electromagnetic force, the shell thickness, armature length and armature radius are positively related to the electromagnetic force, and the effect of pure copper guide sleeve and non-guide sleeve on the electromagnetic force is basically the same. The electromagnetic force can be increased by the guide sleeve with magnetic separation ring. The influence order of parameters on electromagnetic force is: air gap > armature radius increment > armature length increment > shell thickness increment.

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