Advanced Materials Research Vols. 860-863

Abstract: Resistive monitoring method for conventional arrester is not applicable to cable line and it is also not easy to get access to voltage signal. In this thesis, a new method for testing resistive current is adopted, in which the only job is to collect the total leakage current of arrester, simulate a reference signal based on total current information, conduct phase shift to realize phase correction and find out the phase of capacitive component and resistive component, and thus the test on resistive current of arrester for cable line is completed.

Abstract: The monitoring points of cable circulation in cities are relatively scattered. The on-site collection devices restricted by the power supply, installation site and communication distance are usually unable to store large amounts of data or transmit data over a long distance. In this thesis the relay device of data management is developed, realizing the management and sorted storing of the data of the collection devices of close-distance wireless receiving data, and sending the data to remote places through the GSM/GPRS network. Therefore the scattered data can be transmitted to computer analysis and management system over a long distance after centralized processing of scattered data and long-distance data monitoring and comprehensive analysis can be realized. Key Words: Cable, Circulation Monitoring, Relay, Mega64

Abstract: A novel fault location algorithm for distribution network with DGs (distributed generators) is proposed in this paper. According to the distribution network topology and current information of the switch, fault location can be realized accurately through matrix manipulations and criterion analysis in the algorithm. Based on the fault location, a simple method is proposed for the realization of fast fault isolation. Finally, the correctness and feasibility of the algorithm is validated through the analysis of the typical distribution network with DGs.

Abstract: Harmonic transmission is influenced by many factors in the grid and the harmonic resonance phenomenon may be occurred. This paper analyzes the influencing factors, and the relevant model was established, and applied to the practical case.

Abstract: In recent years, natural disasters happened frequently, which caused more and more failures of power system. To study the transmission lines failure under extreme hot weather, firstly the line's temperature changing with time is forecast based on the heat balance equation and the line's failure probability is calculated according to the historical statistics of failure rate. Then a test system to simulate the power grid under extreme hot weather is built and the curve of line's failure probability changing with time is obtained. The results provide a reference to power sector to guarantee the security and stability of the power grid.

Abstract: There are large number of transient signals will be produced when the operation mode is changed. And the frequency of the transient signals distributed in wide range. The most of them are damped and oscillated. The impedance is a popular feature in power system, and it has been widely used in relay protection and fault location. So the impedance calculation based on the damped sinusoidal signal have been the important way to diagnosis the fault, locate the fault and so on. But the methods used now are based on the fundamental impedance calculation theory, lacking theoretical basis. In fact, the traditional methods for fundamental signal calculation are not appropriate for the quantitative analysis of damped sinusoidal signal. The paper analyzed the impedance calculation based on damped sinusoidal signal, combined the features of damped sinusoidal signals and the traditional impedance calculation method. The two typical signal analysis methods for damped sinusoidal signal extraction are used to calculate the accurate impedance based on the different extraction results. And the analysis laid a foundation for the impedance calculation using damped sinusoidal signals.

Abstract: The failure current in resonant grounder power distribution system is small, so it is difficult to detect the fault feeder. This passage presents the equivalent circuit of resonant grounded system, and discusses the difference of electrical characteristics between faulty feeder and sound feeders by using shunt resistors. To reduce the influence of shunt resistors on the system and improve the detection sensitivity, it presents the method of shunting multi-level resistors, and it proves the sensitivity and reliability of this method by EMTP simulation.

Abstract: Economic Load Dispatch (ELD) is a critical matter of improving the operating efficiency of power system and reducing the cost of generating electricity. In this paper, an Artificial Fish Swarm Algorithm (AFSA) which takes network loss into account is designed to search the optimization. Firstly convert the capacity of the generating units in decimal into a binary number which means the location of an artificial fish. And then foraging behavior of fish school algorithm is utilized to make a successive comparison of fitness within the visual distance of current fish. Additionally to avoid getting into local optimization, the position of current fish is changed with a small probability. The simulation results suggest that the algorithm is efficient and feasible in the case of less precision.

Abstract: As the continuous increase of wind power installed capacity in modern grid, its inherent randomness and fluctuation may cause a series of problems to power system frequency control. Since the dynamic characteristics of traditional automatic generation control (AGC) based on PI control cannot fully and effectively meet the interconnected power grids requirements for load frequency control. In this paper, a strategy based optimal control theory is proposed, and a new dynamic cost function is also presented. Compared to the conventional PI control method, the proposed strategy has better dynamic adaptability to interconnected power system with wind generation, and the optimal coordination among control areas can be realized more easily. Take the two-area interconnected power system with wind power model as an example, the simulation is carried out based on MATLAB/SIMULINK. The simulation results show that the control strategy can obviously suppress the fluctuation of system frequency and tie-line power, and its effectiveness is confirmed.

Abstract: In this paper, an communication and battery performance evaluation is discussed for a demand response and battery storage coordination algorithm, which provides a new way of microgrid tie-line smoothing service. A battery storage system and a total number of 1000 heat pumps are modeled to demonstrate the algorithm. A temperature priority list (TPL) model is used to describe the behavior of the heat pumps. Besides, a control strategy via a two-way communication networks is implemented to smooth the tie-line fluctuations. Then considering in a no ideal communication environment, the impacts of the unexpected changes of the on/off status of the heat pumps on the simulation results are studied. Meanwhile, the impacts of different numbers of batteries and batteries with different charging rates are also referred. The results show that coordinating the heat pumps and batteries can significantly smooth the fluctuations brought by the integration of the renewable resources such as the wind and solar power. The switching status changes of the heat pumps, the numbers and charging rate of the batteries also have great influence on the proposed smoothing performance.