摘要:

There is an increasing worldwide interest in economic optimisation approaches for power system expansion and reliability planning. The reliability-cost/worth approach for assessing an optimal level of customer service reliability is based on calculating the costs associated with different system configurations and evaluating the corresponding reliability worth at the customer level. This optimality condition simply intends that the marginal dollar spent to improve service reliability should yield the same benefits to consumers. The application of basic adequacy assessment concepts to generating capacity evaluation is relatively straightforward and the basic concepts are well known. The application of the optimality condition to evaluate simultaneously optimal generation investments and reliability levels is complicated by the difficulty of estimating the functional dependence of consumer interruption costs upon alternate generation and reliability levels. This difficulty has resulted in a number of studies directed towards estimating customer interruption costs. This paper utilises the economic criterion for system optimisation which extends the traditional approach by treating the reliability level as a variable to be optimised. The method is illustrated using the IEEE Reliability Test System (IEEERTS).

DOI:10.1049/ip-c.1988.0010

出版商:IEE    

年代:1988

数据来源: IET

摘要:

Using symmetrical component techniques the steady-state behaviour of a self-excited three-phase induction generator under unbalanced loading is examined. Particular reference is made to single-phase loading, a practical application being the use of standard three-phase cage machines in micro-hydro plants. An unbalanced excitation scheme is proposed which improves balance overall and maximises the allowable power output of a particular machine. A method is presented by which de-rating factor and voltage regulation can be predicted for a general unbalanced condition. The results of modeling are in good agreement with experiment. Possible further applications of the method are to the behaviour of induction generators in networks and the operation of three-phase motors from single-phase supplies.

DOI:10.1049/ip-c.1988.0011

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The paper presents a security algorithm which consists of the superdecoupled loadflow technique for loadflow solution, outage studies, contingency selection and line overload alleviation. A superdecoupled loadflow method with a distributed slack busbar has been applied to line and generator outage studies as well as for line overload alleviation. The accuracy and reliability of the line and generator outage contingency selection method, as previously developed by comparison of its ranking results with the correct ranking of AC outage simulation, has been investigated. A fast computation technique in real power line overload alleviation by generation scheduling and/or load shedding has been proposed by using injections at the terminating busbars of the overloaded line. These injections are determined by the amount of overload only without having to compute the sensitivity and Jacobian line flow matrices and pseudoinverse of the product of these matrices. The proposed algorithm has been validated in tests on the IEEE 24 busbar test system.

DOI:10.1049/ip-c.1988.0012

出版商:IEE    

年代:1988

数据来源: IET

摘要:

An analytic sensitivity method is proposed for the transient security assessment of large power systems. It is based on the recently developed ‘extended equal area criterion’, and on a related transient stability margin. It is shown that this margin leads to a simple algebraic formulation of sensitivity coefficients. Particular attention is focused on the sensitivity with respect to generation power, and possible applications to power system planning and online operation are suggested. For example, the computation of generation and load supply limits provides transient stability constraints and thence means of online transient security assessment and preventive control. Within the limits of the simplified electromotive force behind the transient reactance model, the method proves to be accurate, demanding very little with respect to computing time and fairly independent of the system size. The simulation results reported in the paper corroborate these conclusions.

DOI:10.1049/ip-c.1988.0013

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The paper proposes a new and practical procedure which, by operating on the complete linearised mathematical representation of an interconnected power network, is capable of extracting accurate models of selected portions of the system. The approach is useful for analysing the dynamic or small disturbance stability of the portion of interest without carrying out a full-scale detailed analysis of the whole system. Furthermore, the suggested method can be used to realise a selective near-optimal excitation control scheme of the decentralised type for the power network. A numerical example illustrates the capability of the proposed technique.

DOI:10.1049/ip-c.1988.0014

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The paper describes a technique of circuit analysis based on the diakoptic approach developed by Kron, but using mesh techniques to produce network equations which may be partitioned to facilitate their very rapid numerical solution. A general solution algorithm is presented and its computational efficiency is tested in the solution of typical power networks.

DOI:10.1049/ip-c.1988.0015

出版商:IEE    

年代:1988

数据来源: IET

摘要:

Wave propagation characteristics of overhead lines and underground cables are usually determined using the well known theory of natural modes of propagation. The paper shows that some special circumstances may inhibit the use of such methods of analysis, since the matrix diagonalisation involved in that procedure cannot always be carried out. A critical non-diagonalisable situation is presented with a configuration as simple as a single buried underground coaxial cable. For this irregular case, the wave propagation characteristics are described, and the correct solution is shown not to consist of a superposition of natural exponential modes. Furthermore, the paper alerts the reader to the fact that modal analysis in general, and eigenvalue calculation in particular, may not be so straightforward as it is usually thought, meaning that some surprises may arise with modal analysis computer programs currently in use. Besides informing the reader of the possibility of irregular non-diagonalisable cases the paper also points out two alternative methods of overcoming the difficulties associated with such cases.

DOI:10.1049/ip-c.1988.0016

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The presence of free metallic particles and some other conditions which might lead to breakdown in 420 kV gas insulated substations (GIS) can be detected by measuring their partial discharge activity. The discharge pulses excite the GIS chambers into many modes of resonance at ultra high frequency, which may be picked up by couplers built on to hatch cover plates. Signals from the couplers can be displayed in both the time and frequency domains. Because the oscillations spread throughout the GIS, only a few couplers are needed to cover a complete substation. The method has excellent sensitivity; for example, particles smaller than those likely to cause breakdown can be detected from many tens of metres. Moreover, the nature of the discharging source can be determined, and its position located with good accuracy by timing the wavefronts arriving at couplers on either side of it. Tests using various discharge sources have been made both in the laboratory and on site, and the results are reported. This technique is intended in the first instance for use during GIS commissioning tests. However, simpler equipment operating on the same principle has been developed to monitor continuously the partial discharge level of the GIS in service.

DOI:10.1049/ip-c.1988.0017

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The thyristor-controlled reactor (TCR) is used for AC voltage control on transmission lines and industrial busbars. It has a relatively simple main circuit and its performance depends very much on its control system. The phaselocked oscillator type of control system is now universally used for HVDC convertors, and is being introduced for the TCR. The form of this control described here is of the ‘zero-delay’ type, without control filters or other lags, and gives freedom from harmonic instability and a good combination of stability at other frequencies, with fast response. Examples of applications are described briefly.

DOI:10.1049/ip-c.1988.0019

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The development of two computer algorithms to assess the performance of IDMT over-current protection for interconnected power systems is described. The first algorithm considers the case of three-phase short-circuit faults, and the second considers single-phase to earth shortcircuit faults. Both can include multiple bulk supply points, parallel lines and transformers, directional and nondirectional relays, including both on the same circuit, teed points, and instantaneous high-set elements. The algorithms currently incorporate relays with a standard inverse characteristic but any relay with a current/time characteristic can easily be included. Results are presented of the application of these algorithms to the assessment of the relay performance for several actual power distribution systems. For each selected fault position, the operating time of each relay is calculated and the sequence of relay operation shown until the fault is completely isolated. The results also illustrate, in particular, the ways in which the performance of the relay systems can be tabulated to greatest effect.

DOI:10.1049/ip-c.1988.0020

出版商:IEE    

年代:1988

数据来源: IET