Xiaowei Ma

The protection cooperation of distribution network based on protection intelligent center and the validation of its reliability

With the development of communication technology and artificial intelligence, the study of protection intelligent center is becoming the research focus. To make full use of the technology advance, the concept of protection intelligent center is proposed. The protection intelligent center is a remote center which can gather the electrical information of the whole network and give out tripping signals on the basis of analysis. In distribution network, the protection intelligent center could provide multiple protection with its local layer and center layer. This paper focuses on the cooperation method of different types of protection which protection intelligent center can participate in, and proposes a practical scheme which combines the protection deployed in local layer and central layer to reach an optimal protection performance. The protection method of the system proposed in this paper is complicated to achieve multi-space and multi-layer protection, so the verification of the protection cooperation is also provided in this paper.

Novel protection & control architecture based on virtual devices in digital substation

In order to improve hardware utilization, a novel Protection & Control Architecture based on virtual devices in digital substation is proposed in this paper. An “all-in-one” monitoring and control device is developed to support new architecture. Based on a Cloud Computing platform, the protection and control functions are built as virtual devices. Based on virtual protection & control, the functional configuration and coordination are described for different applications. Extensive studies show that the proposed protection and control based on virtual devices is able to offer significant advantages over the existing devices, such as the reliability improvement and cost reduction.

Simulation study of power transformer inrush current and internal fault

This paper is devoted to electromagnetic transient model and algorithm of inrush current and internal fault for power transformer. In the paper, it presents transformer model with excitation nonlinear characteristic based on the controlled source theory transformer simulation and damping trapezoidal algorithm. It simulates inrush current and internal fault by that model. When transformer inrush current phenomenon is simulated, usually piecewise linearization method will be adapted to solve the problem of transformer excitation saturation. However, after the comparison of simulated results with different step sizes, the paper finds it has overshoot distortion with larger step size and it increases simulation time with smaller step size. Therefore the paper proposes to predict next simulated exciting current during the simulation procedure. When predicted value is over the saturation threshold, exciting current revised formula will replace the original one. This method effectively solves overshoot distortion problem without decreasing simulation step size and improves simulation efficiency. On the basis of this simulation, it researches on transformer internal fault principle and modellings turn-to-turn short circuit internal fault for transformer. This model is able to simulate transformer turn-to-turn short circuit internal fault directly by setting up the parameter without any external circuit building. These models and algorithm are validated by test case.

Adaptability analysis of differential protection for UHV half-wavelength AC transmission line

Relay protection is one of problems troubling the development of half-wavelength AC transmission technology. This paper modeled the half-wavelength line with the distributed parameter, researched the fault characteristics and the adaptability of phase-splitting steady current differential protection theoretically and through plenty of simulation work, and analyzed its influencing factors from three respects. The result indicates that conventional steady differential protection algorithm is not very suitable for half-wavelength transmission, the sensitivity of middle range is the biggest problem. Then adaptability of zero sequence current differential protection and differential protection based on deviation of power frequency component are researched, the simulation results indicate they have better sensitivity. The research result shows the differential protection can be set as backup protection, and need to coordinate with the quick protection which protect the range close to two ends.

A pre-study on operating model and supporting technology for new electricity retail policy

In order to adapt the new policy of the retail side reform, the novel operating models of power retail are proposed for Chinese electricity retailing side reform based on analysis of different power marketing systems in the world. The key technologies for the distribution and utility integrating system are discussed to support the electricity retailing company, which include the planning & design, optimal operation, device management & maintenance, and electricity trade service. According to the new electricity retail policy and development of energy technologies, the distribution and utilization integrating support system is proposed in this paper as the new trend and effective solution for the future electricity retail, which is called the Regional Energy Internet (REI). Both the architecture and the profile of the REI are described to show the preliminary concept of supporting platform for the competitive electricity retail, including SCADA (Supervisory Control and Data Acquisition) platform and advanced applications.

Hierarchy of distribution centralized substation area protection system based on All-in-One devices

With the rapid development of communication technology and the widely constructing of smart substations, wide-area protection and substation area protection have become hot research topics. As an important part of network protection, substation protection at present only realized the centralization of the information transmission, but the comprehensive utilization of information has not been an in-depth digging, on the other hand, protect devices still been placed centralized in the master control room, the regulation that primary equipment and secondary equipment must be set aside a safe distance results in the Large occupation of land, seldom play out the advantages of information protection which can make the devices highly integrated and miniaturized. In response to those questions, a novel distribution centralized substation area protection system based on All-in-One device is proposed in this paper, and the configuration and function of All-in-One device are also described in detail. Then introduces the VPN scheme of the proposed system. On this basis, considering the features of proposed system structure and networking schemes, this paper brings out a time-sharing cooperation work strategy. The example proves that the strategy is reasonable and effective, while shows the superiority of the distribution centralized substation area protection system compared to the traditional protection system.

The mechanism of fault searching for new energy distribution network based on variation of cutting current

With the increase of demand in power supply demand, increased strength of connection complexity and access of renewable energy, traditional current protection has been unable to meet the needs of the safe and reliable operation of distribution system. To prevent this, the cutting-current-based fault location searching algorithm is put forward in this paper using the single-end current vector. Firstly, the feeders are divided into several stages to determine the searching section. Secondly, search the whole line lengthways for the faulted stage, and the accurate fault location is carried out by the breadthwise search, and the fault can be cleared with the help of the existing method and the proposed method. For larger distribution network, dichotomy algorithm is utilized in lengthways search to minimize the time cost. PSCAD/EMTDC simulation results indicate that such a method can play a complementary role for existing protection equipped for the double end new energy distribution network.

The study of area protection principle optimization based on protection intelligent center indistribution network

With the development of communication technology, a large number of intelligent substation has been constructed, substation area protection and wide area protection technology has been widely used. Then Protection Intelligent Center (PIC) taking over the main functions of multiple substations protection in the distribution network comes into being, making large-scale information centralized processed becomes possible. Against to the problem that traditional local information-based protection is difficult to set and coordinate brought by increasingly complex distribution network, this paper redefines the partition to protection are and its search strategy, gives a fault criterion based on multi-terminal current differential protection. Finally we propose the scheme of current differential protection based on partition principle.

Description of protection intelligent center using IEC61850 defined SCL

Introduce the Protection Intelligent Center that suit the evolution tendency of the substation form, but the new form of substation is lack of corresponding description of information model, Based on IEC61850 defined SCL language, according to the characteristics of the Protection Intelligent Center, the paper put forward the structure of Protection Intelligent Center information model description. Then, based on the description of Protection Intelligent Center, a software application is brought out that can acquire the real-time topology of the grid within the range of Protection Intelligent Center, and the flow chart of software is given. Description of Protection Intelligent Center using IEC61850 defined SCL.