The substation cable trench inspection robot is mainly used to inspect the high-voltage cables in the underground cable trench of the substation, so as to find various hidden dangers in time. However, due to serious electromagnetic interference in the cable trench and no communication network underground, the environment is more complicated. Aiming at the complex environment in the cable trench, this paper designs a WLAN-based cable trench inspection robot communication program, combining WLAN with directional antennas, and relaying through relay routing, so that the communication between the robot and the PC is divided into pipeline communication and ground communication Two parts. At the same time, the communication hardware, software, and protocol are designed based on the B/S architecture, which effectively improves the communication distance. Through field verification, the packet loss rate of the communication system proposed in the thesis is less than 0.5‰, the communication is stable, and the communication task of the robot in the cable trench of the substation can be completed well.
The method to discriminate the fault within or beyond the protective zone according to the signals with high frequency detected in protection has problem with low reliability when the resistance of earth fault is high. The transient voltage with low frequency detected in protection can reflect the size of fault intensity approximately, and the transient voltage with high frequency detected in protection in internal fault is bigger than that in external fault when the size of fault intensity is same. The high frequency transient voltage and low frequency transient voltage detected in protection are chosen as inputs and fault section as outputs for training and testing the neural network for fault identification in the UHVDC transmission line, fault section can be identified when input fault characteristic data to the trained model. A variety of transmission line earth fault situation are simulated by PSCAD, and this earth fault section identification method based ANN shows satisfactory performance, even the fault resistance is high.
The paper studied the frequency characteristics of UHVDC transmission line and UHVDC transmission line boundary and their attenuation to high frequency components of fault-generated transient signal. The paper points out that existing approaches which utilize protectors to distinguish local side’s internal or external fault can’t protect the whole line. UHVDC transmission line and UHVDC transmission line boundary’s attenuation to high frequency fault-generated transient signal is overall considered, and a single-ended transient based voltage protection method which distinguishes the opposite side’s internal and external fault is proposed. The Yunnan-Guangdong UHVDC model of actual parameters was built up by PSCAD, and simulation experiment was conducted.
The extraction and analysis of fault information is key to making the transmission line protection configuration scheme. This paper analyzes the mechanism of DC line faults, like lightning, mental and non-mental grounding fault, short to AC line. By referring to actual parameters of Yunnan-Guangdong ±800kV UHVDC transmission system, simulation model is established by PSCAD/EMTDC. According to simulation tests of dc transmission line faults: lightning, grounding fault, high resistance grounding fault and short to DC line, the transient responses of UHVDC line faults are summed up.
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