IEEE TRANSACTIONS ON EDUCATION, VOL. 38, NO. 3, AUGUST 1995 217

Computer Assisted Learning In Power System Relaying

L. L. Lai, Senior Member ZEEE

Abstract- A computer package developed for power system protection design is used to teach protection coordination at City University, London. Examples of package use and experi- ence gained from computer assisted learning in this subject are described. The simulation of protection systems gives students an opportunity to observe the actions of each device after they complete their protection schemes. In order to preserve flexi- bility within this self-learning environment, an expert system is included in the package. The use of an expert system is to make learning as effective as possible by providing guidance on the teaching material. It plays its role only if it is invoked. In other words, the expert system does not supervise learning, but can provide the necessary guidance if a request is made. If there is any error, the result of the simulation wil l also show the nature of the problem. The debugging function can help the students to detect the errors they have made and know how the devices work in the system. The potential of a well-designed computer package is not only to strengthen the teaching and learning, but also lead to creative contributions to the educational process. This benefit is not available through traditional lectures and textbooks.

I. INTRODUCTION NGINEERING is a graphics-oriented discipline in which E drawings, sketches and graphs have always played an

important role but required enormous manpower to produce. The scope of engineering design can be considered to be from the conceptual design solution of a problem down to the for- mulation of that design. The text-only approach constraints the application domain, application of graphical representations can enhance the understanding of complex concepts associated with many engineering disciplines. However, the difficulty lies in ensuring that the design principles are fully understood and not lost in the complexities of learning to use computer packages.

It is possible to produce experts in the use of packages rather than engineers who are able to use software tools to produce, verify and implement their designs. Therefore it is important to address these problems by embedding the package in an environment which firstly provides an easy to use interface and secondly uses knowledge based techniques [l], [2] to encapsulate essential engineering design principles which are used to guide the students through the use of the package and to educate them in these design principles. Moreover, in arriving at a final design, the proper interaction with marketing, business, product planning, organization, finance, time, and manpower need to be taken into account.

Manuscript received February 22, 1993; revised September 10, 1993. L. Lai is with Energy Systems Research Group, City University, London,

IEEE Log Number 9413577. UK.

In responding to the Engineering Councils proposal [3] for BEng and MEng degree programs, Universities now place much emphasis on both design and management. A problem which arises is how the extra material required can be accom- modated in an already overcrowded degree course. One of the most obvious solutions is to use computer teaching. The rapid development of the capabilities of personal computers made computer-aided instruction systems more feasible and economical, indeed, evidence has been produced to show the effectiveness of computer assisted learning material 141, [51.

This paper describes the potential for improving the teach- ingflearning process by using a computer based teaching pack- age for power system protection. The success of developing and using the package will certainly depend upon lecturers and industrial representatives working closely together to exchange views, expertise and experience. The finished package is therefore designed to match both the industrial and curriculum needs which are detailed later.

11. COMPUTER ASSISTED LEARNING The use of computers as a means for learning, or to

supplement teaching, is becoming widespread. A number of terms are used to refer to this type of computer application. The most widely encountered in the literature is computer assisted learning. This paper is concerned with the use of a computer as an aid for learning, and in particular self-teaching where a learner may study at a pace and time of convenience. Many calculations in engineering design are repetitive in nature. A set of principles or rules may need to be applied many times over in the analysis of a problem. A particular example of this type of problem is the analysis of protection coordination of an industrial power system.

Within the power industry, a power system protection engi- neer has one of the most challenging jobs. Wrong application or calculations can lead to disastrous results. One of the objectives of the power system protection course at City is to reduce the industrial training period for new engineers; the lecturer acts as the supervisor of the group and assignments are undertaken from a set of actual cases that occurred in industry. The protection engineer will not only be involved in the technical decisions but often financial considerations as well. The analysis of such a system is very difficult without the aid of a computer. However, the principles involved are quite simple and are detailed in [6] and [7]. Algorithms have been developed and used in large computers and have been reported in [8]. These techniques have also been adopted and used commercially by companies, for example, as reported in [9].

0018-9359/95$04.00 0 1995 IEEE

218 IEEE TRANSACTIONS ON EDUCATION, VOL. 38, NO. 3, AUGUST 1995

In the past, lack of computational power has meant that in covering the design of protection coordination, students have been taught the theory and have then applied it to small and hypothetical systems. This adequately tests the students basic protection theory, but it does not allow for consideration of the optimum design. The rapid advances occurring in interactive computing have provided the engineer with a powerful means of processing, storing, retrieving, and displaying data. The use of computers has meant that much larger systems can be analyzed, opening up the possibility of giving the students an exercise and tuition in the wider aspects of the design and management of an industrial power system. Also, from the industrial point of view, coordination of protection devices by manual methods is a tedious process and does not allow for numerous changes in data which occur between design and final commissioning of a system. Since the selection of device parameters follows well defined rules, it is possible to develop computer programs to select the settings and trace the curves.

Because of the ovemding need to contain costs, the anival of low cost microcomputers, peripherals with graphic capabil- ities and a growing supply of useful engineering and admin- istrative packages, most computer-aided educational materials are developed on microcomputers. The algorithm as reported in [lo] provides coordination plots and is implemented in Fortran on an IBM 486. The kinds of protection and simulation that could be designed and performed by the package are detailed in [8] and [lo].

III. PACKAGE DEVELOPMENT To enable graduate engineers to make valid contributions

to the development of industry, the engineering curriculum in the universities must reflect the immediate requirements of industry [ll].

It is also imperative for universities to establish a strong liaison with industry; students need to have a great deal of contact with engineering in the form of industrial visits, vacation training and lectures by practising engineers. This should give them a taste of what lies ahead in their career as engineers, as well as help smooth over the eventual transition from university to practice.

Teaching is a complex activity concerned with course de- sign, development, evaluation, and performance. Ideally, an appraisal of teaching effectiveness should address all of these dimensions. Modem power engineers should be well educated to meet the needs of future industrial developments. They should be educated with not only the theory and computer techniques, but also industrial application knowledge. How- ever, the vast majority of university engineering students are lack of hands on experience in their classroom, while they may be well trained with profound theoretical knowledge in related disciplines. As laboratory experiment is expensive and time consuming, the students cannot spend too much time on it. This situation makes it difficult for the students to adapt themselves to a new job environment when they depart from the university and are recruited by industry to begin their professional careers. To bridge gaps between theory, practice, academia, and industry, direct integration of industrial application cases into educational software is needed.

The content of the teaching material described in this paper has therefore been developed by joint consultation between industry and education, through a continuing process of review, modification, and evaluation toward the finished package.

To develop an effective self-learning system would require the consideration of many other factors. The most challenging, perhaps, is the layout of information on the screen. Strict guidelines such as the amount of text, highlighting, graphics, and a design philosophy, had to be followed for consistency.

In the development stage, the display layout and readability, the use of color and graphics, the validation of input, the standardisation of screen page presentation, different symbol size, the possibility of defining new symbols and transferability between menus are all checked and improved upon.

In the modification and evaluation stages, trials of the packages with feedback from students are involved. The quality of teaching and performance of students is measured by coursework and assignments. Evaluation of the method has also taken the form of a student questionnaire at the end of each trial, together with careful and critical but informal observation of student activities. Some of the questions will be to assess whether the students have been effectively advised in how to prepare for the session and whether the students have an understanding of what has been achieved. Industrial representatives have also been included in this process in order that they could judge the impact and potential of the package from their point of view.

A computer can improve learning if its use has been carefully designed to make the process easier. In order to preserve flexibility within this self-learning environment, an expert system is developed to make learning as effective as possibly by providing guidance on the teaching material. It plays its role only if it is invoked. In other words, the expert system does not supervise learning, but can provide the necessary guidance if a request is made.

IV. THE A I M S The package provides facilities for the guidance or su-

pervision of the students in design principles. The overall objective of the engineering design facility is to provide an environment containing a variety of design aids which will enable the student to design, select, and analyze a protection scheme guided by stored experience and techniques. The package allows the student to obtain a good understanding of the consequences of variation of parameters interactively. It leads the student into logical selection and decision making processes.

In summary, there are two aims of the protection package related to the educational needs of the students. The first aim is to test the students understanding of the basic theory and to encourage students in the use of self-assessed and negotiated learning strategies. It is important that the students first try to solve the problem by themselves; only showing the correct method is not encouraged.

The second aim of the package is to develop the ability of the student to produce an optimal design to take into account both the scientific and technical factors. By using this package,

LAI: COMPUTER ASSISTED LEARNING IN POWER SYSTEM WAYING 219

TABLE I Ww: CHOICE OF OPTIONS

ED GD VD DE Demonstration EX Exit from package ss Store current system data PS HE Help with expert systems RC Run coordination study pc Plot/display curves RT Run transient study vs

Enter data for new system Get stored system data files Viewleditladd to protective devices data base

Print specified current system data files

View/edit current system data files

the students should be able to use their understanding of the protection theory to develop new or modified designs. The package will improve the effectiveness of teaching and provide the students with an independent learning tool at whatever time they prefer.

v. FEATURES OF THE PACKAGE Students can practice protection coordination conveniently

on the monitor by superimposing and shifting time-MVA curves. This improvement of the instructional tool can make students become more interested in the course and get the fundamental concept accordingly. The package has also two extra functions, that is, debugging and simulation. In the past, students could not know whether the setting of protective devices are appropriate or not until the finished assignments are submitted to the lecturer for corrections. Because relay coordination has no unique solutions; it is tedious work for the lecturer to correct students homework. The package includes an expert system which can point out the errors after the student has carried out the exercise. If there exists any conflict, the package will inform the student what the errors are and where they are. Thus students can correct the errors immediately. This debugging system that utilizes an expert system enables students to learn more efficiently. Data input/output procedures have also been made as simple and straightforward as possible and a menu is very suitable for parameter modifications and interacting different modules within the package. The choice of options could be assessed by using the menu as described in Table I, the students can selected the application type they want to solve as an exercise.

Regarding simulation of protection systems, the protec- tion system is simulated when there is an overcurrent [12]. Previously, students could only imagine the action of each protective device on the basis of the characteristic curves and the set values of protective devices. The package can now simulate the actions of the protective devices when an arbitrary fault occurs. The students can assign a location for the fault to occur on the one-line diagram, and the simulation system will display the status and sequence of operation of the devices according to the tripping order. This design can thus make students understand the protection coordination by observing the dynamic operation of the protection system instead of guessing under conventional teaching methods. By means of simulation, the students can be sure whether there is a proper coordination between the primary protection and backup pro-

tection. And the students can also make sure whether the action of protection system corresponds to their estimation or not. Students can therefore have a better understanding in protection coordination. This will enable students to face an actual situation more easily when they become an engineer in the future.

In addition, the package can perform protection coordination automatically. Most of the current commercial packages have this standard function. It can help students to know more about the software packages that are used in industry today. It also gives students an opportunity to compare their homework with the results from automatic analysis. The results can also be used for reference when students need to correct their homework themselves. The automatic analysis is only an auxiliary function to understand the basic concept of coordination. When students use this package, they must at first decide the setting of each device by graphics, then they can examine their result with the debugging system or observe the simulated operation of the protection system. From the educational point of view, this is a better way of teaching.

If the power system is of a radial structure, then some protective devices may be the upstream device of several downstream devices. Hence a device may become miscoor- dinated after adjustment. When the students adjust settings of time-MVA curves, the package draws all the characteristic curves of the protective devices on the path that is assigned on the computer monitor. This procedure, like the conventional coordination, must take all the characteristic curves of the associated devices into account. The package will find out the new settings of the protection device for a new operating time by adjusting the settings of the protective devices and by shifting time-MVA curves, it can make the students realize conventional procedures and the meaning of protection coor- dination. For this reason, this method is suitable for students to learn the protection coordination.

VI. APPLICATION EXAMPLES A coordination study is carried out for a typical industrial

system as shown in Fig. 1. Two chains are selected: chain1 consists of devices with A, B, C, and D; while chain 2 consists of E plus devices common to both chains. The costs for the current transformers, relays, fuses, miniature circuit breakers, thermal relays, cables, and voltage transformers are given. The students have to decide the number of protective devices, the type of devices, and transformers used. They also have to make sure that any section of the system is not overloaded during normal operating conditions. No other information is given and the students are given four weeks to complete the exercise. The lecturer does not provide any information unless the students ask questions This type of situation which constantly occurs on actual jobs encourages thinking by the students and results in increase class participation.

The coordination results are shown in both Table 11 and Fig. 1. Fig. 1 shows the discrimination curves clearly indicate that at the various locations, the time interval between curves is satisfactory at both the maximum and minimum fault levels seen by the protective devices. Details of the protective devices and system could be found in [lo].

220

SEC 1000

100

10

I

0 1

Coordination study on a typical industrial system P D N a NAME TSM PS(%) A r T M M inn . . . . . . ..- B CDG63 012 100 C CDG31 0 1 6 IW D CDV62 031 100 E IOOA

I

J 6 6 k E O W A B 7515 L

75OkVA

\ B 4 1 5 V IOMVA EE A d l S O / S

0 1 1 10 100 MVA

Fig. 1. Protection coordination for an industrial power system.

TABLE II COORDINATION RESULTS

No Device name Highset or Highset Load Current

A CTM44 0.78 127 140 B CDG13 10 65.1

CDG17 13.95 1626 65.1 C CDGll 67 180 D CDV62 33.5 450 E 300A 10 230

TABLE III DATA (IN PU) FOR MOTOR STARTING UP

fault MVA setting % A

LSS = 4.086 Lrr = 4.048 Lsm = 0.0 Lrm = 0.0 Msr = 2.653 rs = 0.0041 IT = 0.0324 H = 2.85s Rating = 0.78 MVA Voltage = 415 V

Lss and LIT self-inductances of the three-phase stator and rotor circuits respectively;

Lsm mutual inductance between stator phases; LlTtl mutual inductance between rotor phases; Msr mutual inductance between three-phase stator and rotor cir-

cuits; rs and rr resistance of the stator and rotor windings respectively; and H inertia constant.

Load torque characteristic: a = 0 b = -2 c = I where Tm = a + bs + cs2, s: slip

To illustrate the simulation function, the induction motor is started with the direct-on-line scheme and at the instant of switching, the voltage at phase a is at its maximum. The same model and symbols as used in [131 are adopted. The machine data and load torque characteristic are given in Table III. The stator current is shown in Fig. 2. With an accurate staring characteristic, the protective device (e.g., a thermal relay) could be set more precisely. As in this case, since the start current is just less than the highset value and also the starting time is only about 5 sec, therefore no adjustment in settings is required for the thermal relay.

The same industrial power system is chosen to demonstrate debugging function and the usefulness of the expert system within the package. In the example, modifications are made in the type of protective devices in order to create different scenarios of coordination problems. A typical set of require-

IEEE TRANSACTIONS ON EDUCATION, VOL. 38, NO. 3, AUGUST 1995

f l

- 7 I

Fig. 2. A motor starting characteristic.

ments and a solution derived to satisfy the requirements by the resulting rule firing within the expert system for this case is given below: Problem: TSM of 3/10 is too low at B ( c 0.15)

Solution: Relay 1.3/10 is used to solve the coordination problem

Sequence of rule applied: Rule 2 used to identify the problem and propose a solution; rule 28 used to compute new results; rules 23 and 25 used to check the time and current grading respectively; rule 1 concluded that coordination is achieved.

For convenience of the reader, the required rules [ l ] are restated below:

Rule 1 If time grading is within limit and current grading is within

Rule 2 If the TSM of a (3/10) relay is less than 0.15 then use a

(1.3/10) relay Rule 23 If the operating time of a backup relay should exceed that

of its corresponding primary relay for all the fault considered by a coordination time interval then the two relays are time graded

limit then coordination is achieved

Rule 25 If the pickup setting of a relay is within the lower and upper

limits, and the lower pickup tap setting limit is the larger of the minimum pickup tap or a factor times the maximum load MVA through the relay or a factor times the pickup MVA of the previous relay and the upper limit is the smaller of a factor times the normal remote bus fault MVA or a factor times the minimum fault MVA through the relay then the relay is current graded

Rule 28 If the time grading or current grading is violated and the

parameters of the system or protective devices are changed then compute the grading again

This problem has been chosen because it shows the fun- damental difficulties of achieving correct overcurrent grading for an industrial system. It also demonstrates the advantages

LM COMPUTER ASSISTED LEARNING IN POWER SYSTEM RELAYlhG

Tq Tq

quadrature axis transient short circuit time constant; and quadrature axis subtransient short circuit time constant.

221

of the various characteristics available from overcurrent re- lays, namely, instantaneous, independent and dependent time, and directional. For the same problem, students may select different devices for different reasons. Because of this and compromises which have to be made in satisfying the guide- lines, the given problem does not have a unique solution. When the assignments are turned in, the students can defend their choice of solutions and designs. This results in interesting and stimulating class discussions.

In the past, to carry out protection coordination, the as- sumption usually made in the selection and application of protecting schemes is that the subtransient component of fault currents can be neglected. Thus for high-speed and instantaneous schemes single-valued transient reactances are used to determine the fault level while for schemes that have a time delay, steady state values are used. But, in compact isolated power systems both the dc component and the subtransient and transient components of fault current may have significant effect on relay performance. Since it is not possible to generalize circumstances in which transient currents significantly affect relay operation, a worst case example such that a 3-phase to earth fault occurs at the terminals of a synchronous generator is considered and data is shown in Table IV. For a leading power factor operation, the fault current is shown in Fig. 3. It can be seen that the current decays very fast to a small value such that the relay may reset. This effect could easily be studied by using the present package while the traditional way of teaching and learning could hardly provide this possibility.

VII. THE BENEFIT To introduce a new approach to the way in which mod-

ern engineering education and training may be carried out effectively in a continuously changing environment is to be welcome. The present method of teaching has been used since 1986. After a few years of using this package for training purposes, it concludes that the students have actually learnt power system protection. They have learned a number of trade- offs that can be made in the design process. For example, if the

- 4 I Fig. 3. terminals.

Current in phase c for a 3-phase to earth fault occurs at generator

coordination is not possible, then they might have to reduce the grading margin to achieve a solution.

They have also dealt with specifications that can conflict, such as reducing the pickup setting of a relay will increase the relay operating time at maximum fault levels. Effects on coordination due to different types of relays can be observed. From this package, the students gain a wealth of information concerning the coordination of relays and fuses. It confirms that this approach of teaching produces improvements in students knowledge.

However, the students also commented that they find it difficult to tackle an open-ended problem, that is, they do not exactly know how much the lecturer expects from them. They also said that too much time has to be spent on reading the manual and learning to use the package. Therefore a number of changes have been made to the package in order to improve its effectiveness as a teaching aid and to make it more interesting for the students. The major one of these is the introduction of the demonstration at the start of an exercise. Previously the students are not familiar with the package and they are taking a long time in entering problem data, and are making many mistakes. The demonstration module largely overcomes these problems.

It was commented that it is too expensive and time- consuming to develop a good package. It also requires much more resources for this approach of teaching to be widely used. However, developing educational software is part of a curriculum reform and in an attempt to strengthen the general education cumculum, any means with the potential to make education more personal and less passive deserves attention. Use of the computer package as an extension to classroom instruction provides a better understanding of coordination of protective devices in power systems as well as an opportunity to speed up the process of analysis so that a more realistic approach can be taken to design. This

222 IEEE TRANSACTIONS ON EDUCATION, VOL. 38, NO. 3, AUGUST 1995

teaching approach makes it possible to identify the possible mistakes which are very likely to occur and specific training programs which need to be intensified in the future. Based on the comments from the students and lecturers, it confirms that using the traditional method of teaching, such as the blackboard, it is difficult, if not impossible, to address the following topics clearly, namely: earth fault protection; directional relaying; plug setting; time multiplier setting; different types of protective devices; fault levels; highset; loading; grading margin; multiple infeed; multiple outfeed; and transformer configuration. When using this package, since the system is interactive it is very easy to change parts of the design of the input and re-examine the outputs. The effects due to the variations of these parameters which are difficult to communicate to students in the classroom, become immediately evident from the graphical display. This approach is more effective in strengthening students skills, knowledge and abilities in an academic discipline.

VIII. CONCLUSIONS By using this package the students gain knowledge on

industrial applications. The package is seen both as a good complement to the course and as a teaching aid to both the lecturer and students. Moreover, once basic computational methods have been mastered, students can put emphasis on engineering rather than spending hours in tedious calculations. This approach of teaching provides an important stimulus to the concept of independent learning in students. The present approach might also be used by practising engineers for computer-aided analyses and design purposes.

The simulation of protection systems gives students an opportunity to observe the actions of each device after they complete their protection schemes. If there is any error, the result of the simulation will show the nature of the problem. The debugging function can help the students to detect the errors they have made and know how the devices work in the system. In addition, these functions can also shorten the time for discussion and individual instruction for both the lecturer and student. The potential of a well-designed computer package is not only to strengthen the teaching and learning, but also lead to creative contributions to the educational process. This benefit is not available through traditional lectures and textbooks. In terms of technical advancement, there is new information for power engineering educators, for example, in systems where the fault contribution from machines is signifi-

make students understand the current situation of the power industry. If computer-aided instruction tools can be utilized fully, students will become more interested in the course. Thus more talented students will be attracted to power industry.

ACKNOWLEDGMENT The author would like to thank Mr. F. Ndeh-Che for his

help in completing this paper.

REFERENCES

[l] L. L. Lai, An expert system used in power system protection, Power Systems and Power Plant Control 1989, Selected papers from the IFAC Int. Symp., Seoul, Korea, 22-25 Aug. 1989, IFAC Symposia Series, 1990, no. 8, Pergamon Press, Oxford, pp. 489-494.

[2] S. J. Lee, S. H. Yoon, M. C. Yoon, and J. K. Jang, An expert system for protective relay setting of transmission systems, IEEE Trans. Power Delivery, vol. 5, no. 2, pp. 1202-1208, Apr. 1990.

[3] Conference Report, National Conference on Engineering Education and Training, IEE, London, 1981.

[4] L. L. Lai, Computer assisted learning in power system protection, Computer Education, no. 52, pp. 8-9, Computer Education Group, UK, June 1987.

[5] -, a discussion to A program of computer-aided coordination analysis for an undergraduate course in protective relaying, IEEE Trans. Power Syst., vol. 7, no. 4, p. 1549, Nov 1992.

[6] IEEE recommended practice for protection and coordination of indus- trial and commercial power systems, IEEE, Std. pp. 242, 1975.

[7] IEEE Committee Report, Computer-aided coordination of line protec- tion schemes, IEEE Truns. Power Delivery, vol. 6, no. 2, pp. 575-583, Apr. 1991.

[8] L. L. Lai and J. G. Hadwick, Computer-aided design for protection coordination in industrial power systems with the inclusion of transient phenomenq, in Proc. of the Fifteenth PICA Conference, IEEE, Canada, 1987, pp. 453459.

[9] K. McLeay, Analysing power systems using computers, Power Eng.

[lo] L. L. Lai and J. G. Hadwick, Protection coordination for industrial power systems with a consideration of transient conditions on a personal computer, in Proc. of the Ninth Power Sysfems Computation Con$, London: Butterworths, 1987, pp. 758-764.

[ l l ] A. Pahwa and T. R. Ward, Teaching power system protection with industrys cooperation, IEEE Trans. Power Sysf., vol. 7, no. 1, pp. 363-369, Feb. 1992.

[12] C. Y. Teo and T. W. Chan, Development of computer-aided assessment for distribution protection, Power Eng. J., pp. 21-27, Jan. 1990.

[13] A. K. De Sarkar and G. J. Berg, Digital simulation of three-phase induction motorts, IEEE Trans. Power Apparatus Syst., vol. PAS-89, no. 6, pp. 1031-1037, July/Aug 1970.

J., pp. 203-213, 1988.

L. L. Lai 87-SM92) was born in Hong Kong. He joined Staffordshire Polytechnic, UK (now known as Staffordshire University), as a Senior Lecturer in 1984.

cant when compared to that from the grid, the decay timi can From January to October 1987, he was an Industrial Fellow to both the GEC Alsthom Turbine Generators Ltd and GEC Alsthom Engineering

be critical in setting the relays and selecting fuses correctly. interesting aspect of the work is the Dhenomenon of a rising

Research Centre. He was also a part-time Consultant to the Central Electricity Generatine Board from 1985 to 1987. He took UD an academic wst at Citv - -

fault contribution from the d d as &e local generation faui University in 1989. In April 1991, he established the Power A d Ener& Systems Research Unit and he was the Unit Director. Since August 1993, contribution decayed in one case where discrimination based

on a constant grid fault contribution is doubtful, the analysis

that the settings would result in the unnecessary loss of the

It has been noticed that the students using this package show better performance in their test than those who selected y h is a CMered Electrical Engineer and a the same course previously. The course should be able to

the Unit was expanded as the Energy systems Research Group and B. is Head of G~OUP.

He has published over 80 technical papers in the IEEE, IEE, WAC, CIGRE and other journals and conference proceedings and travels regularly to give

seminars and workshops in Europe, Asia and the Middle East. His main research areas are in energy systems, power electronics, artificial neural networks, fuzzy logic controller, genetic algorithms and computer assisted

Member of the IEE, London.

using the more accurate time-varying grid contribution showed

grid supply 181, [lo].