Xu Bingyin

Distributed Distribution Automation system based on the identification of tie-switch

Distribution Automation (DA) could realize fault location, isolation and service restoration (FLISR), which is an important means of improve power supply reliability. Generally, to perform power supply restoration, the operator needs to know the position of tie-switch, which may vary due to structure changes in the distribution network. As a solution, a kind of distributed tie-switch identification method based on the smart terminal unit (STU) is proposed in this paper, with which fast service restoration can be realized in changing network structures. In this method, voltage transformers are not required to be mounted on switches, and the tie-switch identifying process can be accomplished without relying on the master station. The method can be carried out in normal operation time and fast service restoration could be realized even if the structure of the network is changed, and lab tests have been performed to verify the smart terminal units capability in the identification of tie-switch.

Research of islanding detection and islanding protection based on WAN phase comparison

Study PQ control mode of the inverter-based distributed energy resources(DER), and analyses its system characteristics while DER operating connected with distribution network. When the point of common coupling (PCC) between DER and distribution network is broken and the island formed, analyzed change characteristics of frequency and voltage phase and the influence of unbalanced power in islanding system, especially remarkable phase difference changes will occur between large power bus side and DER side voltage. Based on this the islanding detection and islanding protection method based on WAN phase comparison is proposed, the islanding detection criterion is the voltage phase difference between distribution network bus side and DER side, the synchronous measurement and calculation of voltage phase on both sides are completed by the feeder automation terminals (FTU), and realize information exchange through the rapid communication system. Based on Matlab, established the islanding detection simulation model, experimental results verify the reliability and applicability of the method..

Earth fault protection using transient signals in non-solid earthed network

Existing earth protections are not satisfactory in practical application due to the nature of weak fault current and unstable fault arc. Three earth fault protection methods using the transient zero sequence signals in special frequency band are presented and evaluated in this paper. The faulty feeder is selected by comparing amplitude and polarity of selected component of transient zero sequence currents of all feeders, an measuring the direction of selected component of transient zero sequence currents. They have higher sensitivity and reliability. Recorded real fault data proved the proposed techniques.

Study on the feeder topology modeling and IED configured methods for IEC61850

IEC61850 comprises complete data object modeling methods and consistent service interfaces, making the data interaction, function joint and interoperability among different terminals possible. Besides, its point to multipoint communication mode is very suitable for distributed intelligent feeder automation (FA) system that IP network based. Distributed intelligent FA is more and more valued and becoming to the trend because of its independence on the global information from the master station, fast fault process, better adaptability to the change of distribution grid, easier maintenance etc. In the applications of distributed intelligence FA, control functions are implemented based on the network topology information, such as power supply recovery has to know the location of the tie switch, island protection requires to track the trunk power, Load transfer must forecast the load bearing capacity. So, IEC61850 promoting to the field of distribution automation cannot avoid a key problem that how to clearly express the feeder connections/topologies among substations and configure them to related STUs. In this paper, the connectivity modes of medium voltage distribution feeder were analyzed ;the feeder equipment model and topology model were extended through the topology expressed methods of IEC 61968/61970 common information model (CIM); the SCL object model was put forward and the example cable ring network was partially described abiding by XML Scheme; Finally, several feasible methods by which the feeder topology configured to STUs were presented, as well as the comparison of their implementation effects. All of the above is to technically support the IEC61850 application for distributed intelligent FA.

LC resonance mechanism analysis of fault transient for single phase earth fault in non-solidly earthed network

Transient principle is one of the main methods of single phase earth fault detection in non-solidly earthed network. Clear and detailed transient mechanism analysis can further improve the reliability of fault detection. According to impedance characteristics of transmission line, distribution line shown as distributed parameter model will alternate present capacitive and inductive with frequency increasing. Transient process of single phase earth fault is produced by series or parallel resonance between different modulus and different lines that present as capacitive and inductive respectively. Transient current produced by series resonance between line-mode and zero-mode network contains clear fault location information, but other resonance mechanisms of fault transient do not have this information. ATP simulation results prove the correctness of the resonance mechanism.

Calculation method for one-section lumped-circuit model of uniform line

This paper aims to simulate transient characteristics of distributed parameter model by one-section lumped-circuit model (lumped-Π, lumped-T and lumped-Γ models). Based on error analysis of equivalent impedance in the lowest resonant frequency band of distributed parameter model and lumped circuits, a parameter calculation method of lumped circuits was proposed in this paper. The first simplification principle is to ensure power-frequency equivalent impedances equal. Secondly, be sure the first resonant frequency equal and comprehensive error of equivalent impedance in the lowest frequency band minimum. Contrast with traditional one-section lumped circuits, the applicable frequency band of one-section lumped-Γ, lumped-T and lumped-Γ models raised in this paper is extended. Obtained results can be used for the establishment of transient equivalent circuit.

The implement of carrier based islanding protection

In this paper, carrier based islanding protection is taken as the research objects, and the signal injection equipment and the islanding protection equipment are designed to implement the protection. First, it makes demands on signal injection equipment, and chooses proper signal injection mode, signal frequency and signal source according to the demands; then, it makes demands on islanding protection equipment, and chooses optimal signal detection method, signal processing algorithm and the measurement of voltage and frequency; finally, it establishes the simulation model of DG interconnection system with signal injection and islanding protection using matlab to validate the feasibility of signal injection equipment and islanding protection equipment. Simulation results show that the designed equipments satisfy the requirements and carrier based islanding protection can be implemented reliably.