摘要:

The paper presents a new and simple method for transient stability assessment of multimachine power systems. The criterion for assessment is given in terms of the rate of change of kinetic energy of individual machines subsequent to fault clearance. The basic concepts and the mathematical formulation of the method are summarised. A number of practical test systems are used to demonstrate the superior efficiency of the method relative to three different Lyapunov functions given in the literature.

DOI:10.1049/ip-c.1988.0060

出版商:IEE    

年代:1988

数据来源: IET

摘要:

In the current reduced network formulation of the transient energy function method, all system loads are conventionally modelled as constant-impedance load to reduce the network to the internal nodes of the generators. Neglecting other types of load model (e.g. constant-power and constant-current load models), as in current approaches, may lead to incorrect results. The paper describes the inclusion of load modelling in the transient energy function method, using a sparse network formulation. In this formulation, the loads can be represented as they occur in practice (constant-impedance, constant-power, constant-current, or any combination thereof). Applications of the new technique to practical utility systems have proved the effectiveness of the new technique in producing more accurate results. The results compare favourably with those obtained by the time domain solution techniques.

DOI:10.1049/ip-c.1988.0061

出版商:IEE    

年代:1988

数据来源: IET

摘要:

Power systems DC load-rejection may result in system dynamic overvoltages sometimes followed by generator self excitation. These overvoltages may be unacceptably high. The paper introduces a new pattern-recognition-based algorithm to predict power system load-rejection overvoltages. Using a power system digital simulation, a training set of a wide range of system loading conditions is created. A discriminant hyperplane is then derived to identify overvoltages, i.e. insecure conditions. In addition, a least squares method is incorporated to derive the relationship between the voltage security indices and postcontingency voltage deviations in the training process. A corrective algorithm based on the sensitivity analysis is also developed so that power system operators can take appropriate action at the appropriate time.

DOI:10.1049/ip-c.1988.0062

出版商:IEE    

年代:1988

数据来源: IET

摘要:

Based on the best-first search strategy, this paper develops a general computational model for the automatic determination of circuit allocation schemes in subtransmission substations. Starting from a discussion of the allocation requirements, fault indices based on the percentage of power rating loss of circuits are first derived. The best-first strategy is then defined by the group allocation and overall allocation index trees, which are formed from the relations of the fault indices. A search procedure implementing this strategy is developed to determine the best overall allocation arrangement, which is found by combining the best group allocation schemes. A general method for assigning interconnectors to the tasks of source and load circuits to assess the security level of the overall allocation schemes in the process of islanding constraint checking is reported. The model is implemented by a logic programming language, Prolog. The developed software system is applied to allocate six groups of circuits from seven substations to a 132 kV duplicate-busbar substation.

DOI:10.1049/ip-c.1988.0064

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The analysis of currents flowing through a substation earth electrode and through earth wires of overhead lines, connected to the substation for ground faults within the substation, is performed, including the proximity effects between the substation and the earth electrodes of the lines towers. Comparison of the results obtained using the complete model suggested in the paper with the results obtained ignoring the proximity effects, for typical cases, has shown that the proximity of the earth electrodes might considerably affect the ground current distribution and therefore it must be taken into account in certain circumstances. Relatively simple expressions are derived for evaluation of currents flowing through different parts of earthing systems that cover the proximity effects.

DOI:10.1049/ip-c.1988.0065

出版商:IEE    

年代:1988

数据来源: IET

摘要:

Series resonance at ripple carrier frequencies, between distribution transformers and power-factor correction capacitors, has occurred at irrigation installations in the North Canterbury Electric Power Board's rural supply area. Inductor blocking to relocate the series resonance at a lower frequency is discussed. A low-cost inductor suitable for practical use is suggested. The use of interactive linear-network-simulation computer programs to analyse the inductor blocking requirements of various motor, transformer and capacitor combinations is then outlined, and optimised inductor parameters for the various equipment combinations used at pumps sites are presented. Laboratory tests with the low-cost inductors confirm the theoretical analysis.

DOI:10.1049/ip-c.1988.0066

出版商:IEE    

年代:1988

数据来源: IET

摘要:

Rotary arc circuit breakers interrupt low-level fault currents through the extinction of a free burning arc between the load current contacts but utilise an electromagnetic field for spinning the arc, transferred into a coil, for interrupting higher-level fault currents. The operation of such circuit breakers relies upon using the arc additionally for switching the coil into the circuit to produce the arc-controlling magnetic field. The paper reports the results of investigations into factors which affect the transfer of the arc root from the load current carrying contact to the annular contact that supports the arc during electromagnetic rotation and simultaneously allows the magnetic field producing coil to be activated. The influence of a number of parameters is considered including the peak arc current, point on wave switching, nature and pressure of the arcing medium and the contact/coil geometry. The results show that for SF6, in the current range of several hundred amperes, the arc transfer time may be prolonged by as much as 25 ms. However, by suitable design of the contact/coil geometry, this arc transfer time may be substantially reduced to promote improved circuit breaker performance through an earlier interruption of the fault current.

DOI:10.1049/ip-c.1988.0067

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The various control functions of a static TCR reactive current compensator can be implemented by software. A fast and versatile microprocessor-based control scheme has been developed which can be easily adapted to suit different power system requirements. Its useful applications to regulate and symmetrise 3-phase voltages and to improve dynamic stability of a power system are particularly examined in the paper.

DOI:10.1049/ip-c.1988.0068

出版商:IEE    

年代:1988

数据来源: IET