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Your search keyword '"Mokhlis, H."' showing total 106 results
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106 results on '"Mokhlis, H."'

6. A New Centralized Adaptive Underfrequency Load Shedding Controller for Microgrids Based on a Distribution State Estimator.

Author

Karimi, M., Wall, P., Mokhlis, H., and Terzija, V.

Subjects
MICROGRIDS, ESTIMATION theory, ELECTRIC power consumption, SIMULATION methods & models, ENERGY consumption
Abstract

This paper presents a new centralized adaptive underfrequency load shedding controller that is integrated with a distribution state estimator to improve the frequency stability of islanded microgrids. While underfrequency load shedding is a well-established corrective emergency frequency-control action, it is not entirely suitable for use in microgrids with low inertia and a limited number of measurement devices. The novel centralized controller presented in this paper overcomes these challenges by incorporating a distribution state estimator to estimate the power consumption of the demand. In parallel to this, the actual active power imbalance in the microgrid is estimated by simultaneously monitoring the system frequency and its rate of change. The centralized controller uses these two variables to determine the correct amount of load to be shed. The performance of the proposed controller has been validated using computer simulations of the actual distribution network in Malaysia. These simulation results show the effectiveness of the proposed centralized controller for preventing power system instabilities, which might lead to cascading outages and even a complete blackout in microgrids that have been disconnected/islanded, from the main grid. [ABSTRACT FROM AUTHOR]

Published
2017
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25. Partial discharge phenomena within an artificial void in cable insulation geometry: experimental validation and simulation.

Author

Illias, H.A., Tunio, M.A., Bakar, A.H.A., Mokhlis, H., and Chen, G.

Subjects
PARTIAL discharges, CABLES, ELECTRIC insulators & insulation, GEOMETRY, ELECTRIC fields, SURFACE discharges (Electricity)
Abstract

In the presence of void in cable insulation, repetition of partial discharge (PD) occurrences is one of the main sources of insulation degradation, which may lead to complete breakdown. Therefore, it is important to monitor the condition of cable insulation through PD measurement. Replicating PD measurement on a test object with the presence of a void within cable insulation may help a better understanding of PD characteristics within cable insulation to be achieved. Therefore, in this work, test samples of cable insulation geometry containing an artificial void were prepared in the laboratory for PD experiment. The PD measurements were done as a function of void size and applied voltage. A physical model of PD activities within an artificial void in cable insulation geometry was also designed using finite element analysis method. The model was developed by considering PD occurrences within non-uniform electric field distribution in the void and charge movement along the void surface. The model was applied for simulation of PDs within the void in cable insulation geometry to increase the understanding on PD physical phenomena. This includes the impact of distribution of void surface charge on the distribution of the electric field within the void through comparison with the captured measurement results. [ABSTRACT FROM PUBLISHER]

Published
2016
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26. Experiment and modeling of void discharges within dielectric insulation material under impulse voltage.

Author

Illias, H. A., Tunio, M. A., Mokhlis, H., Chen, G., and Bakar, A. H. A.

Subjects
VACUUM, DIELECTRIC materials, ELECTRIC insulators & insulation, ELECTRIC potential, SIMULATION methods & models
Abstract

The presence of cavity in motor insulation fed by variable speed drive is one of the sources of partial discharge (PD) occurrence, especially under impulse voltage. This is a serious problem as PD can accelerate degradation of the motor insulation. Therefore, it is important to prevent void discharges from occurring in motor insulation under impulse voltage. In this work, the characteristics of void discharges within dielectric insulation material under impulse voltage were investigated through experiment and modeling. The test object consists of a rectangular void within a polyethylene material. The test object was stressed with different peak magnitude, front time and tail time of the applied impulse voltage. The experimental results were reproduced by simulation results from a void discharge model in insulation material. From the model that was developed, a better understanding on physical parameters that influence the characteristics of void discharges within dielectric material under impulse voltage can be attained. [ABSTRACT FROM PUBLISHER]

Published
2015
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45. Determination of partial discharge time lag in void using physical model approach.

Author

Illias, H., Tunio, M., Mokhlis, H., Chen, G., and A. Bakar, A.

Subjects
PARTIAL discharge measurement, HIGH voltages, ELECTRIC insulators & insulation, PARAMETER estimation, FINITE element method
Abstract

Repetition of partial discharge (PD) activities within a dielectric insulation of high voltage equipment may lead to dielectric breakdown, eventually resulting in failure of the whole equipment. Thus, PD measurement is essential in high voltage insulation system. Modeling of PD activity may increase an understanding of PD phenomenon. One of the parameters which can be determined from PD modeling is the statistical time lag. In this work, a physical model of PD using finite element analysis (FEA) method has been developed to determine the relationship of statistical time lag with different applied stresses; these include different applied voltage, frequency and temperature. The statistical time lag as a function of different applied stresses was determined through comparison between measurement and simulation results. The proposed experimental-modeling approach may increase an understanding on the physical explanation about the statistical time lag. [ABSTRACT FROM AUTHOR]

Published
2015
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