Volume 11, Issue 5

A new tree structure called the two-level computation tree model is proposed for real time dynamic simulation of large-scale power systems. The features of the computation tree method are that the root node of the tree corresponds to a disconnected linear network, which is easy to be dealt with, and the tree leaf-nodes represent the partitioned subsystems. In the process of trajectory simulation, the correction factors of Newton type iteration are computed through a tree traversal procedure. One advantage of the new method is that the computation tasks for all subsystems can be carried out simultaneously using any parallel computation facilities. Case studies on the 10-generator New England test power system and on a representation of Northeast China power system verify the accuracy and validate the potential application of the proposed method in the real time contingency simulation for realistic large-scale power system.

Numerical simulation, which relies on precise mathematical models and parameters of elements, is currently the most efficient tool to study the power system stability. However, since some of grid companies in China did not foresee the rapid development of wind power, the lack of parameters information of wind farms negatively affects the system simulation study with scalable wind energy integration. In addition, the field condition of wind farm also limits the grid company to equip extra real-time measurement equipments to measure the dynamic response of wind generators. This paper proposes a method based on wide-area trajectory sensitivities to identify the parameters of FSIG-based (Fixed Speed Induction Generator) wind farms. By this method, the data recorded by Wide Area Measurement System (WAMS) are used to process identification, which satisfies the requirement from grid companies. This paper gives a detailed description on the modelling of identification, the analysis of trajectory sensitivity and the algorithm to solve the optimization problem. Both of the case studies of modified 9 and 39 bus systems show the numerical simulation results are closer to realistic after parameter identification, and it is feasible and beneficial to use this identification method based on WATS to enhance the accuracy of system simulation with scalable wind energy integration.

Distributed generations (DGs) have been increasingly connected on the distribution networks that will have the unfavorable impact on the traditional protection methods because the distribution system is no longer radial in nature and is not supplied by a single main power source. This paper presents a new automated protection method using radial basis function neural network (RBFNN) for a distribution system with DG units. In the proposed method, the fault type is determined first by normalizing the fault currents of the main source. For implementing fault location considering various types of faults, two staged RBFNNs have been developed. The first RBFNN is used for determining the fault distance from each power source and the second RBFNN is used for identifying the faulty line. To isolate the fault, another RBFNN has been developed for determining which circuit breakers (CBs) that must be open or close. Several case studies have been made to verify the accuracy of the method to specify the fault location and protection of the system in distribution networks with DGs. The predicted results showed that the proposed RBFNN based protection method can accurately determine the location of faults and isolate the faulted line in the test power system.

Fault-proof earthing switches are one of the important modules of a gas insulated substation, as it enables make at 100 percent short circuit current, which is functionally different from maintenance earthing switches. The fault-proof earthing switch shall be designed to make and break electro-magnetically and electro-statically induced currents as per IEC-62271-102. The paper discusses the impact of “test circuit configurations and voltage” on test parameters for gas insulated fault-proof earthing switch utilizing simulation with PSCAD software. Authors record the development of a 145 kV gas insulated fault proof earthing switch by considering novel design features like minimum arcing/pre-arcing time, effective current transfer from arcing contact to ground terminal, etc. The development has been evaluated successfully for electro-magnetically and electro-statically induced current duties as per IEC. Finally, design parameters to be considered for ensuring reliable performance during induced current switching from fault-proof earthing switches are also discussed.