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Volume 150
Issue 4
IEE Proceedings - Generation, Transmission and Distribution
Volume 150, Issue 4, July 2003
Volumes & issues:
Volume 150, Issue 4
July 2003
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- Author(s): R.A. Jabr and B.C. Pal
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 150, Issue 4, p. 385 –391
- DOI: 10.1049/ip-gtd:20030462
- Type: Article
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p.
385
–391
(7)
A modified version of the weighted least absolute value (WLAV) method for the solution of the power system-state-estimation problem is presented. The WLAV method can be seen as minimising a linear objective function subject to a set of nonlinear constraints. The modification is aimed at producing a WLAV estimator that remains insensitive to bad data, even if they are associated with leverage-point measurements. This is achieved by bending the linear objective function, so that the residuals of bad measurements are allowed to grow without incurring much additional cost in the objective function. Consequently, the optimisation procedure would find an optimal solution where the residuals of all bad measurements are nonzero. The optimisation is carried out via sequential linear programming. It is shown that each linear program corresponds to a linearised WLAV problem with weights adjusted automatically during the iterations. To ensure fast execution time, the linear program is solved using a homogeneous interior-point method. Computational results show that the proposed method can identify bad data in leverage points. - Author(s): S. Kumagai and N. Yoshimura
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 150, Issue 4, p. 392 –398
- DOI: 10.1049/ip-gtd:20030502
- Type: Article
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p.
392
–398
(7)
Tracking and erosion resistances of highly filled silicone rubbers (SIRs) and of polymer alloys made from SIR and ethylene vinyl acetate copolymer (EVA) were evaluated after being aged by the stress of acid rain, UV, corona or water absorption. It was demonstrated whether or not high-level fillers could sufficiently protect tracking and erosion resistances against ageing. Acid rain dissolved alumina trihydrate filler at the surface layers of various polymers tested, thereby reducing the tracking and erosion resistances of those polymers. UV and corona stresses affected the basic polymers rather than the fillers, decreasing the polymers' resistances to tracking and erosion, while highly filled SIR and alloys maintained their tracking and erosion resistances after absorbing large amounts of water. - Author(s): B. Lee ; S.-H. Kwon ; J. Lee ; H.-K. Nam ; J.-B. Choo ; D.-H. Jeon
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 150, Issue 4, p. 399 –404
- DOI: 10.1049/ip-gtd:20030501
- Type: Article
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p.
399
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A fast contingency screening algorithm using SIME for the transient stability monitoring of the KEPCO system is implemented. This method evaluates the first-swing stability of a large number of contingencies in a short time with reliable accuracy. The salient features of the proposed screening algorithm are as follows. First, a critical cluster of generators is identified by a new index in the early stage of the time domain simulation. Thus, the computational time required for finding the equivalent one machine infinite bus system can be reduced significantly. Second, clustering critical machines can perform even in very stable cases. This allows us to avoid the extra calculation of the time trajectory that is needed in the SIME for classifying the stable cases. Third, the screening capability is improved using the power-angle trajectory and subdividing the contingency classification. The test results on the KEPCO system show that the proposed method can be adopted as a contingency screening function and the transient stability assessment for the transient stability monitoring of the KEPCO system. - Author(s): O. Rodríguez and A. Medina
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 150, Issue 4, p. 405 –412
- DOI: 10.1049/ip-gtd:20030423
- Type: Article
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p.
405
–412
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The paper describes the fundamentals, analytical formulation and application of an efficient methodology for the transient and steady-state analysis of the synchronous machine. The state space phase co-ordinates model of the synchronous machine takes into account the time-varying nature of the machine inductances and inter-spatial harmonic inductances. The dynamics of the synchronous machine are represented by a set of ordinary differential equations (ODEs) in the time domain. The machine behaviour is analysed under severe abnormal operation conditions. The model allows a detailed and accurate transient representation of the machine, which cannot be achieved with conventional models based on the dq0 frame of reference, especially for the case of unbalanced fault analysis. The steady state after the fault is cleared up is obtained efficiently with the application of a Newton technique for the acceleration of the convergence of the state variables to the limit cycle. The synchronous machine model is compared in terms of accuracy and computational efficiency against a widely used and accepted machine model of an electro-magnetic transient program (EMTP-ATP). - Author(s): R. Billinton ; S.O. Faried ; M. Fotuhi-Firuzabad
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 150, Issue 4, p. 413 –419
- DOI: 10.1049/ip-gtd:20030397
- Type: Article
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p.
413
–419
(7)
Composite system reliability studies incorporating a six-phase transmission line are presented. Both load-point and system indices are used to examine the impact on the individual bus and overall system reliability of incorporating a six-phase transmission line. Comparative studies are conducted in order to investigate the impact of the location of a six-phase transmission line on the load-point and system reliability indices. The worth of employing the six-phase transmission line is expressed in terms of the reduction in the customer interruption cost. The results are illustrated using a small test system. - Author(s): Y. Chen and P. Chowdhuri
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 150, Issue 4, p. 420 –426
- DOI: 10.1049/ip-gtd:20030246
- Type: Article
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p.
420
–426
(7)
A previous study on laboratory-model ground rods showed that the impulse impedance of these ground electrodes is a function of the injected impulse current and fits the relationship: Z=kIpα, where k and α are two parameters which depend upon the electrode configuration, soil properties and the impulse waveshape. The power-frequency and impulse impedances of two vertical rods embedded in the soil of a field near the university campus are measured. It is found that the ground electrodes in the field also have the similar relationship with the injected current. In complementary experiments, the same soil is tested in the laboratory with a laboratory model electrode system, consisting of a vertical rod embedded in the axis of a cylindrical soil holder with controlled moisture content in the soil sample. The objective is to correlate the laboratory data on the impulse impedance to estimate the impulse impedance of the ground electrodes tested in the field and compare the results with that of the actual field tests. It is possible to estimate the impulse impedance of the ground electrodes in the field from tests performed on laboratory-model electrodes. In correlating the laboratory data to the field data, the critical electric field of soil ionisation plays a critical role, which depends upon the soil properties, e.g. soil resistivity. Future research should be directed to find a more precise relationship between the critical electric field and the soil properties. - Author(s): P. Chowdhuri
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 150, Issue 4, p. 427 –433
- DOI: 10.1049/ip-gtd:20030500
- Type: Article
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p.
427
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Impulse impedance of vertical rods embedded in several soil types was determined by laboratory tests under four temperatures and four soil moisture contents with three different waveshapes of the applied impulse voltage. To avoid errors due to current spikes caused by soil ionisation, it is proposed that the impulse impedance be defined as the ratio between the average voltage and average current during the application of the impulse current. With this definition, the impulse impedance is a nonlinear function of the injected impulse current Zavg=kIPα where k and α are parameters that are functions of the soil characteristics and the grounding electrode configuration. It was also found that the impulse impedance is a function of the waveshape of the applied impulse voltage, higher for steeper wavefront of the applied impulse voltage. - Author(s): N. Amekawa ; N. Nagaoka ; Y. Baba ; A. Ametani
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 150, Issue 4, p. 434 –440
- DOI: 10.1049/ip-gtd:20030300
- Type: Article
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p.
434
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An impedance formula of a semiconducting layer at the core and sheath surfaces of a cable has been developed. The formula becomes identical to that derived by Schelkunoff when the semiconducting layer is neglected. A transient current waveform calculated by using the formula agrees well with that calculated by a numerical electromagnetic analysis method FDTD. The inner, outer and mutual impedances of a two-layered conductor show quite different characteristics from those of a single conductor neglecting the semiconducting layer. The characteristic results in the total cable impedance being oscillatory as a function of the semiconducting layer resistivity. A similar characteristic is observed in the cable admittance considering the semiconducting layer. Thus, transient voltage wave deformation is significantly different from that of a cable neglecting the semiconducting layer and is quite dependent on the resistivity. The difference is dominated by the semiconducting layer admittance and the impedance causes a minor effect, considering the fact that the thickness is less than 10 mm and the resistivity greater than 0.1 Ω m in an actual cable. - Author(s): K.P. Wong ; J. Yuryevich ; A. Li
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 150, Issue 4, p. 441 –446
- DOI: 10.1049/ip-gtd:20030405
- Type: Article
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p.
441
–446
(6)
The solution of the load flow problem is fundamental to the operation of every modern power utility. With the advent of modern power electronics, devices such as the unified power flow controller have been developed for the control of power systems. These devices provide unprecedented control over load flows and voltage levels at their location within the power system. With this increased control, however, comes an increase in the complexity of the load flow problem. It is necessary that existing and new load flow algorithms be developed which can accurately and reliably solve the load flow problem in the presence of these devices. An evolutionary programming load flow algorithm is presented which is capable of solving the load flow problem for systems containing unified load flow controllers. The performance of the algorithm is demonstrated on a modified version of the IEEE 30 node system. - Author(s): Z. Chen ; Z. Chen ; E. Spooner
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 150, Issue 4, p. 447 –454
- DOI: 10.1049/ip-gtd:20030304
- Type: Article
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p.
447
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A grid-commutated thyristor inverter based power electronic interface for a direct-drive modular permanent magnet generator in a variable-speed wind energy conversion system is described. The AC/DC/AC power electronic interface consists mainly of a diode rectifier and a thyristor inverter. The inverter ignition angle can be adjusted continuously to control turbine speed so that the optimal energy capture is achieved. The reactive power and harmonic characteristics of the thyristor converter system have to be compensated to meet the standards for grid connection. An active compensation system is discussed to minimise the harmonic distortion and to provide reactive power control. A simple method of deriving the reference current for the active compensator is proposed on the basis of optimal operation conditions. Several compensation schemes are considered. Experimental results from a laboratory model are presented along with computer simulation results, which are in good agreement. - Author(s): C.C. Wu and N. Chen
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 150, Issue 4, p. 455 –461
- DOI: 10.1049/ip-gtd:20030460
- Type: Article
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p.
455
–461
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A reasonable amount of spinning reserve is essential to satisfy system security constraints when the power system encounters a contingency. For isolated power systems, the influence of the system characteristics on spinning reserve requirements (such as load models, load variational characteristics, frequency sensitivity of loads) is more important than the reliability of individual units. The paper proposes a method that takes into consideration load variational characteristics, system load, load-frequency sensitivity factor and frequency operating standards to schedule spinning reserve requirements, which are called reasonable spinning reserve requirements. The one-minute recovery frequency following a contingency would be a more appropriate measure of system security and would represent an enhanced frequency regulating reserve policy. To examine the merits of the proposed method, simulation runs were performed on the Taiwan Power System (TPS) and compared with the Taiwan Power Company (TPC) manual dispatch. - Author(s): R. Billinton and A. Abdulwhab
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 150, Issue 4, p. 463 –468
- DOI: 10.1049/ip-gtd:20030401
- Type: Article
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p.
463
–468
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Overall evaluation of generating system adequacy appears to be declining in the new utility environment despite the fact that severe power shortages have occurred in jurisdictions such as California and Alberta due to inadequate generating facilities. The installed generating capacity should be capable of meeting the system load in the face of capacity outages and the removal of selected generating units for scheduled maintenance. In a deregulated utility environment, capacity shortages can be created by a lack of coordination in scheduling generating unit maintenance. This can be avoided by having impending maintenance requirements scheduled by the independent system operator. The objective in scheduling preventive maintenance should be to ensure that the resulting risk does not exceed a predetermined acceptable level. In a deterministic approach, the acceptable margin is either, a percentage of the available capacity or load, or a value equal to the largest loaded unit. A methodology for maintenance scheduling is presented that combines a probabilistic approach and an acceptable deterministic criterion into a single framework. This methodology is designated as the health levelisation technique. The effect of conducting preventive maintenance with different load profiles is illustrated. The concepts presented are illustrated by application to the RBTS. - Author(s): C.C.A. Rajan ; M.R. Mohan ; K. Manivannan
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 150, Issue 4, p. 469 –474
- DOI: 10.1049/ip-gtd:20030244
- Type: Article
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p.
469
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An approach to solving the short-term unit commitment problem (UCP) using a neural-based tabu search (NBTS) is presented. The solution of the unit commitment problem is a complex optimisation problem. The exact solution of the UCP can be obtained by a complete enumeration of all feasible combinations of generating units, which could be a huge number. The unit commitment has commonly been formulated as a nonlinear, large-scale, mixed-integer combinational optimisation problem. The objective is to find the generation scheduling such that the total operating cost can be minimised, when subjected to a variety of constraints. This also means that it is desirable to find the optimal generating unit commitment in the power system for the next H hours. Tabu search is a powerful optimisation procedure that has been successfully applied to a number of combinatorial optimisation problems. It has the ability to avoid entrapment in local minima by employing a flexible memory system. The neural network combines good solution quality for tabu search with rapid convergence for an artificial neural network. The neural based tabu search method is used to find the unit commitment. By doing so, it gives the optimum solution rapidly and efficiently. The Neyveli Thermal Power Station (NTPS) Unit – II in India has been considered as a case study and extensive studies have also been performed for different power systems consisting of 10, 26, and 34 generating units. The data collected has been used for implementation in the above methods. Numerical results are shown, comparing the cost solutions and computation time obtained by using the intelligent techniques with the conventional methods like dynamic programming and Lagrangian relaxation to reach proper unit commitment. - Author(s): G.W. Ault ; J.R. McDonald ; G.M. Burt
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 150, Issue 4, p. 475 –481
- DOI: 10.1049/ip-gtd:20030374
- Type: Article
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p.
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A strategic analysis framework for evaluating distributed generation and distribution utility strategies is presented. The framework is based on the idea of evaluating all distributed generation issues across many scenarios to encapsulate the breadth of uncertainties stemming from independent distributed generation in regulated distribution networks. A distributed generation value function is proposed to enable distribution system planners and strategists to gauge the aggregate impact of distributed generation on all parts of the distribution business. This enables the distribution company to formulate its response to distributed generation by testing prospective strategies using the range of generation market, power network and utility business models proposed. The results from a case study based on the UK situation shows the potential value of distributed generation (both positive and negative) to distribution network operators. The case study also demonstrates the application of the proposed strategic analysis framework and the value of the results produced. - Author(s): G. Verbič and F. Gubina
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 150, Issue 4, p. 482 –486
- DOI: 10.1049/ip-gtd:20030461
- Type: Article
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p.
482
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An algorithm for protection against voltage collapse is proposed. The algorithm makes use of the magnitudes and angles of the local phasors. The change in an apparent-power line flow during a time interval is exploited for computing the voltage-collapse criterion. The criterion is based on the fact that the line losses in the vicinity of the voltage collapse increase faster than the delivery of the apparent power, and, at the voltage-collapse point, the losses consume all the increased power. The selected criterion equals 0 when a voltage collapse occurs, which gives the protection relay with an appropriate setting an opportunity to react earlier. The proposed algorithm could be easily implemented in a numerical relay. The algorithm is simple and computationally very fast. An online protection scheme can be applied at the relay point of an endangered line. The algorithm was tested on various test systems including the Slovenian 275-busbar test system. - Author(s): C.C. Brozio and H.J. Vermeulen
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 150, Issue 4, p. 487 –492
- DOI: 10.1049/ip-gtd:20030422
- Type: Article
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p.
487
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A wideband, lumped-parameter equivalent circuit model topology for two-winding power transformers is proposed. This model topology is designed to reflect the internal electromagnetic behaviour of such transformers. A parameter estimation methodology is presented for determining the parameters of the proposed model structure from measured frequency responses of the open- and short-circuit input impedances and the voltage transformation ratios. Measured and simulated frequency- and time-domain results are presented for a 16 kVA, 22 kV/240 V distribution transformer. These results show that the proposed model accurately predicts the transformer terminal responses in the frequency range between 10 Hz and 100 kHz. - Author(s): C.J. Wu and T.H. Fu
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 150, Issue 4, p. 493 –500
- DOI: 10.1049/ip-gtd:20030302
- Type: Article
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p.
493
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The voltage flicker is one of the major power quality disturbances in a weak power system. Better measurement and limitation techniques are always desired. An effective and accurate calculation method is presented to obtain the voltage flicker components and the 10 Hz equivalent value. By using the indirect demodulation method, the RMS values of a voltage waveform are calculated cycle by cycle to obtain the envelope. Then the fast Fourier transform (FFT) is used to obtain the flicker components. This method can increase the computing speed and reduce the hardware requirement in a power quality instrument when the FFT is used. The effects of sampling rate, harmonics, and system frequency shifting are investigated. The latter two are common disturbances in addition to the voltage flicker when arc furnace loads are connected in a weak power system. A calibration procedure is used to improve the frequency leakage effect and increase the calculation accuracy. The calculation results from given voltage flicker waveforms and field measured waveforms reveal the effectiveness of the proposed method. It can be used in both 50 and 60 Hz systems. - Author(s): I.M. Dudurych ; T.J. Gallagher ; J. Corbett ; M. Val Escudero
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 150, Issue 4, p. 501 –506
- DOI: 10.1049/ip-gtd:20030252
- Type: Article
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p.
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An accurate analysis of the lightning performance of a HV transmission line using the EMTP program is presented. By means of simulation using a digital model developed within the ATP-EMTP program with its MODELS-feature, the performance of a 110 kV unshielded overhead line under the influence of a direct lightning stroke is analysed. The simulation includes an adequate model of the transmission line, while also taking account of other factors such as the frequency dependence of the line parameters, models of wooden-porcelain insulation, wooden, and metallic towers and grounding systems including their impulse resistance characteristics. An impulse corona model (described elsewhere) is used, which, together with an adequate presentation of the flashover mechanism appropriate to air/porcelain insulation, allows one not only to predict the crest value of the overvoltages throughout the line, but also to assess accurately the real impact on the line fittings and substation equipment of the lightning surge travelling over the line. All the models are thoroughly verified by an extensive comparison of the simulated results with experiments by previous authors. Practical recommendations based on the simulations are made for an improvement in the lightning performance of a typical 110 kV transmission line. - Author(s): Q. Jiang ; S. Cheng ; Y. Cao
- Source: IEE Proceedings - Generation, Transmission and Distribution, Volume 150, Issue 4, p. 507 –511
- DOI: 10.1049/ip-gtd:20030425
- Type: Article
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p.
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A method based on a Lure Lyapunov function is developed to analyse subsynchronous resonance (SSR) phenomena in power systems. An improved Lure Lyapunov function used to analyse the stability of a power system including the turbine-generator (T-G) shaft is presented first. Then, a standard Lure control model for a power system with a T-G shaft is obtained. The stability of such nonlinear systems at the equilibrium points is discussed in detail. The stable operation region of the system is discussed with the proposed method. The effectiveness of the proposed method is verified by a case study. This study has shown potential benefits and the validity of the Lyapunov direct method in the subsynchronous resonance analysis. Compared with the conventional analysis method, such as eigenvalue and frequency scanning techniques, the proposed method is based on the original nonlinear system. Error, that may be introduced by linearisation, is avoided completely. Moreover, the stable operation region of power systems can be obtained by the proposed method.
Iteratively re-weighted least absolute value method for state estimation
Tracking and erosion resistance stability of highly filled silicone and alloy materials against electrical and environmental stresses
Fast contingency screening for online transient stability monitoring and assessment of the KEPCO system
Efficient methodology for stability analysis of synchronous machines
Composite system reliability evaluation incorporating a six-phase transmission line
Correlation between laboratory and field tests on the impulse impedance of rod-type ground electrodes
Impulse impedance tests on laboratory model ground electrodes
Derivation of a semiconducting layer impedance and its effect on wave propagation characteristics on a cable
Evolutionary-programming-based load flow algorithm for systems containing unified power flow controllers
Current source thyristor inverter and its active compensation system
Online methodology to determine reasonable spinning reserve requirement for isolated power systems
Short-term generating unit maintenance scheduling in a deregulated power system using a probabilistic approach
Neural-based tabu search method for solving unit commitment problem
Strategic analysis framework for evaluating distributed generation and utility strategies
Fast voltage-collapse line-protection algorithm based on local phasors
Wideband equivalent circuit modelling and parameter estimation methodology for two-winding transformers
Effective voltage flicker calculation algorithm using indirect demodulation method
EMTP analysis of the lightning performance of a HV transmission line
Analysis of shaft torsional oscillation in a power system using a Lure Lyapunov function
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