Research On Faults Disposing Scheme For Distribution Network Of Hengshui

With the rapid development of national economy, the demand for high powerquality and reliability is in increase especially in the distribution network. In recentyears, the investment in the distribution network is increasing continuously to keeppace with the generation and transmission network. Actual operation data shows mostpower-cut accidents occurred in the distribution network and it is imperative toimprove power quality, reduce the power-cut time and improve reliability of powersupply. Therefore, deep researches are conducted in this paper including fault location,relay protection scheme for system with distributed generation to solve the problemexisting in distribution network. The major contributions of this dissertation are asfollows.1) To address the problem of protection coordination after DG accessing to thedistribution network，a new adaptive distance protection scheme of distributionnetwork with DG is proposed. Firstly, on the basis of the connected point of DGs, theprotected feeders are divided into different zones with adaptive distance protectionconfigured at the upstream side of DG. Then, based on a fault characteristic analysisof the distribution system with DG, the adaptive distance protection criterions ofsegment I and II are constructed. In this scheme, the protection setting values can beadjusted adaptively, not affected by the operating mode and the output capacity of DG.2) In order to identify multiple faults in multi-supply network accurately, a newscheme of fault location and isolation based on the fault current is proposed. Thisscheme firstly forms network description matrix by using the topology of distributionnetwork at normal operation condition of distribution network. When the faultdisturbance is monitored, the messages of circuit breakers and switches are detected inthe SCADA system based on FTU to identify the switch nodes of fault section. Thenthe operations of switches can be obtained to isolate the fault. The scheme has highaccuracy, simple calculation, and good real-time performance, expanding thegenerality and practicality of matrix algorithm in the case of distribution network faultlocation effectively.3) In order to improve the utilization of distribution network equipment and loadtransfer capability effectively, a novel load transfer scheme in the case of the maintransformer faults based on interconnection relationship is presented. This schemefirstly forms main transformer interconnection matrix and conforms load transfer area by using simplified network topology relationship at normal operation condition ofdistribution network. When the main transformer is out of operation due to failure ormaintenance, the load of faulted main transformer is distributed based on thecapacity-load ratio of the load transfer district. In the process of distribution, sub-loadtransfer strategy is proposed aiming at the constraint of interconnection capacity andsecondary transfer strategy aiming at the constraint of main transformer capacity.