Zhanjun Gao

An Automatic Faulted Line Section Location Method for Electric Power Distribution Systems Based on Multisource Information

This paper presents an automatic faulted line section location method for distribution systems. It can be divided into two parts: faulted line section location method for medium-voltage distribution feeders and faulted area identification technique for low-voltage distribution systems. In the first part, an adjacency list that shows the adjacency relationship and status of fault indicating devices is developed. Then, an iterative search technique is devised to traverse the adjacency list to determine the faulted line section. In the second part, a relational table that shows the association relationship between smart meters, meter boxes, and distribution transformers is developed. Based on the table and the voltage of smart meters received from the customer electric information acquisition system, the faulted area can be located. Several test cases studied in a real distribution system demonstrate the effectiveness of the proposed method.

A new fault location method for distribution networks using multi-source information

Along with the rapid development of the power industry, distribution networks get more sophisticated. Traditional fault location methods have obvious drawbacks. In this paper, an accurate and efficient method based on multi- source information from protective equipment and FTUs (Feeder Terminal Unit) as well as voltage sag profiles from monitored node is proposed for fault location in distribution networks. When a short-circuit fault occurs, by using BFS (Breadth First Search), topology analysis algorithm determines suspected faulted sections. Then, fault distance is calculated by substituting measured voltage sag magnitude and impedance angle into the simulation databases. Through simulating for a real 35 kV distribution network with short-circuit fault, the methods accuracy and validity are proved.

Fuzzy comprehensive risk assessment of distribution network fault based on rough set theory

For disadvantages such as plenty of low level risk factors, strong fuzzy characteristics and regional differences between urban and rural areas in traditional distribution network fault risk assessment, a comprehensive risk assessment method with multi-factor influence and multi-region effect is proposed to describe different influence on fault risk assessment for distribution network based on rough set theory and fuzzy comprehensive assessment method. The main influence factors are acquired based on attribute reduction in rough set, and then new comprehensive risk assessment model is established by introducing risk assessment theory into it. Lastly, compare and analyze the results of different areas to acquire risk assessment and indicate feasibility and effectiveness of the combined comprehensive risk assessment method.

Power System Fault Diagnosis Based on protection coordination and Petri net theory

In this paper, an approach of power system fault diagnosis based on the protection coordination and Petri net theory is presented. The construction of diagnosis model and the method of identifying the faulted equipments are described in detail. The relation grade between faulted equipments and their protections are described also. Test result shows that the method can reduce processing time and is more able than previous method to adapt to the changing of network configurations.

Study on Electrical Digital Simulation System Following IEC61850

Power system real-time digital simulation system, which is widely used in China, plays an important role in stability analysis, security assessment, relay protection equipments test, etc. With electronic transformers, D/A conversion and power amplification are no longer needed, output data by simulation software can be directly sampled. The schematic diagram of the new digital simulation system with electronic transducer is proposed in this paper. The interface converter connecting simulation system and digital equipment secondary and its modules are presented. A method to test the validity of the new digital simulation system is proposed. GTNET has been developed to provide real time communication to and from the simulator via Ethernet. The suggestion has a primary theoretical significance and has important values for promoting the application of electronic transducer, the RD digital simulation; interface; data transformation.

A fast directional comparison pilot protection for UHV transmission line

This paper proposes a new pilot protection method for ultra-high voltage (UHV) transmission line, which is based on the characteristics of the average value of the fault component current. Theoretic analysis shows for an internal fault, the signs of the average values of the fault component current detected by relays on both ends of the line are identical, while they are opposite for an external fault. Through comparing the signs of the average values detected by two relays on both ends of the line, an internal fault can be distinguished from an external fault. Using PSCAD software, a 1000 kV transmission line model was constructed, and extensive simulations were performed. The simulation results indicate the validity and feasibility of the proposed protection method.

Research on designing methods of the secondary system in digital substation

A designing method for the secondary system in digital substations is proposed, which takes the graphics software of Power Designing Institutes as a platform. The model of primary system and ICD (IED Capability Description) files of secondary devices are used as initial design information. Designers configure secondary devices and connect virtual terminals on the model of primary systems. Then visual virtual secondary circuits, network physical wiring and functional interoperation are generated to describe the configuration and structure of secondary system in digital substations. At the same time, SCD (Substation Configuration Description) files and CID (Configured IED Description) files will be generated automatically. The proposed method provides visual means for secondary system design in digital substations, which is good for standardized and normalized integration work of secondary systems in substations as well as for installation, adjustment, extension, reconstruction and update of devices in digital substations.

Generalized impedance-based fault distance calculation mehtod for power distribution systems

This paper presents a new impedance-based fault distance calculation formulation for power distribution systems. The majority of low- or medium- voltage distribution systems are characterized by having numerous branches, laterals and sub-laterals, highly unbalanced operation, and time varying load profile. All of these and other characteristics make most efficient approaches proposed for fault location in power distribution systems not applicable to distribution systems. The proposed method uses only measurements of voltage and current at the beginning of the analyzed feeder, and additional equipments such as, fault locators and monitoring devices are not needed to be installed in the distribution system. The apparent impedance is calculated by using the fundamental rms values of the measured voltage and current in this paper. This method is suitable to any kinds of fault and can be used to unbalanced power distribution systems, since it is derived in phase domain.