摘要:

The economic scheduling of power generation is considered, and an improved algorithm based on a combination of mixed integer-linear and dynamic programming presented. Mixed integer-linear programming is used to determine feasible combinations of units at each scheduling point, while a novel dynamic programming approach identifies promising scheduling routes in the time domain. The algorithm obtains the same solutions as mixed integer-linear programming, but with significant savings in the solution times required and the amount of computer memory used.

DOI:10.1049/ip-c.1986.0001

出版商:IEE    

年代:1986

数据来源: IET

摘要:

Frequency and duration evaluation in interconnected power systems involves the integration of both parallel and series elements. The paper presents a comprehensive technique for performing this task in the form of an integrated algorithm. This procedure is then extended to utilise a correlated load model developed from the chronological occurrence of load values in the two systems to assess the integrated system adequacy. The method to incorporate load correlation is fully described, and examples based on small hypothetical systems and the IEEE reliability test system are used to assess the correlation severity.

DOI:10.1049/ip-c.1986.0002

出版商:IEE    

年代:1986

数据来源: IET

摘要:

The magnetic leakage fields in large turbogenerators produce currents in the steel frame supporting the stator core. This paper describes measurements undertaken to determine the magnitude and distribution of the currents in the stator frame of a particular generator. Currents are produced mainly by the axial magnetic fields impinging on the core end, and vary linearly with the current in the stator winding. The radial current from the stator core end screen (15 kA per pole) flows mainly through flexible links to the stator frame. A simplified theoretical model is described to demonstrate the effect of different link systems. The results highlight the importance of considering in detail the electrical paths provided to accommodate large currents in the core frame, so that overheating at junctions of components of the frame may be avoided.

DOI:10.1049/ip-c.1986.0003

出版商:IEE    

年代:1986

数据来源: IET

摘要:

Stator end-region fields in turbine-generators are calculated using the finite element method. Representation of the nonlinearity of the stator iron and the eddy currents induced in the stator core back are features of the model. Computed results for axial flux are compared with measurements taken from a 660 MW machine running on load at leading power factor. The 3-dimensional electromagnetic field problem which requires solution in the end region of the machine is simplified by assuming that all quantities vary in a first harmonic sinusoidal manner in the circumferential direction. To represent the field, a combination of electric vector potential and magnetic scalar potential is used. Because the problem is nonlinear the finite element equations must be solved iteratively. A combination of Newton–Raphson and chord iterations is used. The first stage employs Newton–Raphson iterations assuming the problem to be magnetostatic, then, with this solution as a starting approximation, chord iterations are used to include eddy currents into the nonlinear model.

DOI:10.1049/ip-c.1986.0005

出版商:IEE    

年代:1986

数据来源: IET

摘要:

The paper investigates the effect of adding a second 1072 MVA turbogenerator to an existing one in a power station feeding a series capacitor compensated transmission line. In carrying out the investigation, the new two-generator system is modelled as one equivalent generator with increased capacity, and also as a multimachine system with two separate generators. A comparison of these models shows that, for this type of stability study and this transmission system configuration, there is no advantage gained in modelling the two generators separately rather than as one equivalent generator. The results further show that conditions can exist where the system is stable with one generator but unstable with two, and vice versa.

DOI:10.1049/ip-c.1986.0006

出版商:IEE    

年代:1986

数据来源: IET

摘要:

The paper is a follow-up to the paper written by Stalewski, Goody and Downes for the Second IEE International Conference on Developments in Power System Protection in 1980. The paper discusses the required performance of two types of pole-slipping relay which utilise the principle of impedance measurement and explains the difficulties with this method of measurement, as revealed by model machine and system tests, in distinguishing between pole-slipping and certain types of fault conditions. It describes the logic criteria developed for each relay to overcome these problems. The paper also describes the principles involved for the relay installation at Dinorwig, in determining how far each relay should reach in order to detect remote pole-slips.

DOI:10.1049/ip-c.1986.0007

出版商:IEE    

年代:1986

数据来源: IET

摘要:

A procedure is described for selecting cables for radially-connected low-voltage distribution networks of given layout, so that the volume of conductor in the network is a minimum. This corresponds to producing a minimum-capital-cost design when the cost of cables varies linearly with their conductor cross-sectional area. The procedure, based on analytical methods for the design of distributors, includes voltage regulation and the current ratings of the cables as limiting factors in the design. It also permits other factors, such as the unbalanced loading of phases and the presence of existing branches, to be allowed for. Results are given for two networks, with given costs for cables, and compared with results from a tried procedure which seeks to minimise costs directly. The comparison indicates that the method can produce good results rapidly. It is concluded that this, coupled with the fact that programming and computation are sufficiently limited for sizeable networks to be handled on a small microcomputer, suggests that it could be a useful design procedure.

DOI:10.1049/ip-c.1986.0008

出版商:IEE    

年代:1986

数据来源: IET

摘要:

The paper proposes a method for simplified analysis of earthing systems based on the aggregation of elements with (approximately) equal leakage current densities into equivalent single electrodes. The method makes possible a fair evaluation of earthing system performances with considerable savings of computer time and memory. The applicability of the method is checked for afew sample earthing systems.

DOI:10.1049/ip-c.1986.0009

出版商:IEE    

年代:1986

数据来源: IET

摘要:

Representative power system networks incorporating multi-terminal feeders are analysed under typical pre-fault load conditions, to establish suitability for differential protection on the basis of a circular relay characteristic of marginal operation expressed on a complex plane in terms of the ratio of local current to the sum of remote currents in the steady state. Differential protection is shown to be feasible, with discrimination improved at lower levels of protective circuit energisation by expanding the radius of the area of stability on the complex plane inversely as the magnitude of the equivalent remote relaying quantity. The desired effect is demonstrated practically in an analogue realisation using ideal signalling, by the modification of a two-input mean amplitude comparator relay through the provision of additional restraint with 1 cycle operating time achievable.

DOI:10.1049/ip-c.1986.0010

出版商:IEE    

年代:1986

数据来源: IET