摘要:

The application of the theory of voltage regulation on a distribution network to the problem of optimising the various voltage control facilities available is generally assumed to be well understood. However, with complex network arrangements, the wide variety and numbers of distribution transformers, and differing load patterns, a distribution engineer is faced with a major problem when attempting to optimise the voltage performance of a distribution network, while maintaining the voltages supplied to consumers within declared limits. The paper covers a theoretical approach to distribution network voltage performance, leading to the derivation of a parallelogram theory linking primary substation source busbar voltage and the tap setting on each distribution transformer on the network. Based on this parallelogram theory, a computer program has been developed which enables distribution networks to be surveyed in greater depth, thus enabling engineers to more readily identify problem areas. Overall the program provides a powerful and efficient means of assessing and optimising the voltages on existing networks, or modifying networks to accommodate additional loads, or for designing new networks. The program is adaptable for use on any MV/LV distribution network. The paper thus provides both a theoretical and practical approach to the problem of improving the voltage performance of distribution networks.

DOI:10.1049/ip-c.1983.0027

出版商:IEE    

年代:1983

数据来源: IET

摘要:

The stochastic load flow (SLF) is extended to include non-Gaussian ‘long-term’ nodal probability-density-function (PDF) data by replacing each non-Gaussian PDF with a ‘Gaussian sum’ approximation. A series of SLFs (stochastic load flows) are then performed and the results recombined, with the correct weightings, to generate non-Gaussian PDF profiles for busbars and lines of interest. Generally less than half of the most likely convolution components need evaluating.P–ø,Q–Vdecomposition and nodal dependence is easily incorporated in the study and moment matching can be used to determine the ‘best’ lower order Gaussian sum approximation. Long-term network topological impedance changes can also be included in the proposed method.

DOI:10.1049/ip-c.1983.0028

出版商:IEE    

年代:1983

数据来源: IET

摘要:

The economic dispatch of active power in large-scale power systems is considered and an algorithm for the solution of the problem by means of the sparse dual revised Simplex method is presented. Computational experience with large-scale problems, including dynamic dispatch over several time steps, is given, which indicates that the method has very low memory and processor time requirements and is suitable for implementation on minicomputer systems. The algorithm is extended to allow for hierarchical constraint relaxation and removal in cases where an infeasible problem has been specified inadvertently. The availability of such a constraint relaxation strategy permits the application of approximate methods for the inclusion of transmission losses and spare capacity constraints.

DOI:10.1049/ip-c.1983.0029

出版商:IEE    

年代:1983

数据来源: IET

摘要:

The paper presents an efficient method for minimising power losses and for improving the voltage profile of a large power system. This is accomplished by optimal allocation of reactive-power generation in the system by changing generator voltages and transformer tap settings. The problem is formulated as an optimisation problem, suitable for solution by the linear-programming technique. The advantage of this method lies in its very fast convergence. This, coupled with the fact that load-flow calculations are not necessary, results in considerable saving in computer time and memory. The proposed algorithm has been tested on sample systems and the results are presented and discussed.

DOI:10.1049/ip-c.1983.0030

出版商:IEE    

年代:1983

数据来源: IET

摘要:

A direct method is developed for investigating the transient stability of power systems, based on the approximation of the stability boundary by tangent hypersurfaces at certain unstable equilibrium points. This is a development of the tangent hyperplane method of Yee and Spalding. It is compared with the hyperplane method by application to three representative systems and is found to give improved results and to overcome some limitations. Other approaches to estimation of the stability region are also studied, which provide some indication of the shape of the separatrix and the transient behaviour of the state trajectories.

DOI:10.1049/ip-c.1983.0031

出版商:IEE    

年代:1983

数据来源: IET

摘要:

An HVDC scheme is an amalgamation of both AC and DC components, the behaviour of which is often difficult to describe because of the interdependence of many of the parameters. The response of the DC system is dependent on the AC system and vice versa. The basic scheme controls also include both rectifier and inverter controls, which are basically separate but interdependent. The complete scheme could be described as a nonlinear multivariable control system which is sensitive to external disturbances. The paper describes the analysis of such an HVDC scheme using a simulator model and frequency-response techniques. The results described constitute a sensitivity analysis of the system to the principal parameters which affect the steady-state stability, such as the inverter short-circuit ratio and AC-system damping, as well as the sensitivity to control parameter changes.

DOI:10.1049/ip-c.1983.0032

出版商:IEE    

年代:1983

数据来源: IET

摘要:

Stresses on materials for HV components have become increasingly large owing to the reduction of their size and the worldwide increase in voltage levels. Since the electrical stress depends heavily on geometric factors, critical domains of an arrangement cannot be represented by such simple bodies as rings, spheres or cylinders. The paper describes an algorithm based on the CAD concept for optimising electrode contours according to given field distributions on their surfaces. This algorithm strictly separates field calculations and geometric corrections. The curvature change necessary to alter the contour is obtained by the simultaneous displacement of all contour points. Using this method, for example, a constant and minimum field strength, or a maximum initial voltage in air or SF6, is achieved. Tests were run on several HV components designed for practical use. The experimental results demonstrated the improvements predicted by the computer calculations.

DOI:10.1049/ip-c.1983.0033

出版商:IEE    

年代:1983

数据来源: IET

摘要:

The paper examines the polarising signals used in British and Continental distance protection schemes, in an attempt to optimise the resistive reach of the polarised-mho relay, and also minimise the possibility of overreaching during zone 2 resistive faults. Dual and single polarisation schemes are investigated and alternative schemes with improved protection characteristics are suggested. Relay performance, during ‘reverse’ phase-to-phase faults, is considered, and a simple procedure is given to establish a relay characteristic for a ‘reverse’ fault.

DOI:10.1049/ip-c.1983.0034

出版商:IEE    

年代:1983

数据来源: IET

摘要:

The paper provides a detailed investigation of the principal properties of distance protection response, for the particular conditions of faults immediately behind the intended zone of protection coverage, and against which the protection is required at all times to discriminate. Based, first, on a nontransient evaluation model and stability indices defined for each earth- and phase-fault element of a complete protection terminal, the combinations of conditions for which reverse-fault stability margins are likely to be lowest are identified. The dependence of the margins on the fault level at the protection location, protection forward-reach settings, the crosspolarising level, and the power transfer at the instant of fault inception are examined. From this basis, the extent to which stability margins might be impaired by the presence of transients in comparator input signals is investigated using extensive dynamic simulation facilities. Of principal concern in close-up reverse-fault operation is the transient response of capacitor-voltage transformers, from which protection signals are derived, but the paper shows that, for all asymmetrical fault conditions, dynamic stability margins remain high. Protection discrimination is most severely tested by symmetrical 3-phase-to-earth faults, for then all primary input voltages to capacitor-voltage transformers collapse, and the subsequent protection response is determined mainly by their residual transients. In this extreme fault condition, all earth- and phase-fault comparators are close to an operating threshold, but the paper gives the form of capacitor-voltage-transformer response which guarantees stability.

DOI:10.1049/ip-c.1983.0035

出版商:IEE    

年代:1983

数据来源: IET