grounding resistance measurement analysis of grounding system in vertical-layered soil

IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 19, NO. 4, OCTOBER 2004 1553

Grounding Resistance Measurement Analysis ofGrounding System in Vertical-Layered Soil

Rong Zeng, Member, IEEE, Jinliang He, Senior Member, IEEE, Yanqing Gao, Student Member, IEEE, Jun Zou,and Zhicheng Guan

Abstract—How to precisely measure the grounding resistance ofsubstations is the fundamental factor to guarantee the safe oper-ation of power systems. The placement rules of test electrodes forthe grounding resistance measurement of grounding system in ver-tical-layered soil were analyzed by the numerical method in thispaper. The actual demanded location of the test potential electroderespective to the true grounding resistance of grounding system indifferent measuring directions changed (in a wide range) when thegrounding system was arranged in different soil models. The testerror of 0.618 method to measure grounding resistance sometimesis very high. The test route that the test circuit is in parallel with thevertical boundary is recommended for measuring the groundingresistance of grounding system in the vertical-layered soil area. Thescientific and suitable measuring method of grounding resistance isbased on analyzing the actual soil model and the grounding systemstructure to obtain the suitable test route and choose the correctcompensated point location of the potential electrode.

Index Terms—Fall of potential method, grounding resistance,grounding system, substation, vertical-layered soil.

I. INTRODUCTION

THE GROUNDING system of a substation is a fundamentalcountermeasure to guarantee the safe operation of power

systems [1]. The grounding resistance is an important index ofgrounding systems for substations and power plants, and is alsoa parameter to measure the efficiency, safety of grounding sys-tems, and to check whether the grounding systems meet thedemand of design. Due to the nonuniformity of soil and mea-suring error of soil resistivity data and some other factors, whichcannot be considered in simulating analysis, the designed valueof grounding resistance must be checked by the field test afterthe grounding system is constructed [2], [3]. On the other hand,in order to examine the actual condition of the grounding systemof an operating substation, the grounding resistance must bemeasured periodically. The measurement of the grounding re-sistance is routine work to ensure the safe operation of powersystems in China [4].

Measuring the grounding resistance simply and precisely is abig problem in power systems [5], [6]. And correctly arrangingthe measuring circuit according to the actual soil structure isthe key to precisely measure the grounding resistance. Presentlyin China, the grounding resistance is still measured by 0.618

Manuscript received January 8, 2003; revised May 27, 2003. Paper no.TPWRD-00011-2003.

The authors are with the Department of Electrical Engineering, Tsinghua Uni-versity, Beijing 100084, China (e-mail: [email protected]; [email protected]; [email protected]; [email protected];[email protected]).

Digital Object Identifier 10.1109/TPWRD.2004.835283

method (the test potential electrode is placed at the location of0.618 , where is the distance between the groundingsystem and the test current electrode); therefore, we often findthat the grounding resistance of a grounding system measuredin one direction is very different from the result in another direc-tion. After analyzing the geological structure of soil, we foundthis condition usually exists in substations where the soil isnonuniform in the horizontal direction. For example, a 220-kVsubstation with a lake or a river in the front and a mountain be-hind, the measured results of grounding resistance in differentdirections are different. So it is very important to discuss thearrangement rule of measuring electrodes for grounding resis-tance test circuit of a grounding system in vertical-layered soil.

The actual vertical-layered soil structures vary in differentareas. In order to acquire some useful conclusions for groundingresistance measurement of substations in vertical-layered soils,several typical models of vertical-layered soil were assumed andanalyzed in this paper, and all results illustrated were simulatedones.

A professional software package was applied in the analysisof this paper, which is the CDEGS software package developedby Safe Engineering Services and Technologies Ltd., Canada(SES) [7]. Extensive scientific validation of the software usingfield tests and comparisons with analytical or published researchresults has been conducted [8].

II. PLACEMENT RULE OF POTENTIAL ELECTRODE IN

VERTICAL TWO-LAYER SOIL

In our simulation, a 100 100 square grounding grid witha grounding conductor span of 10 m in vertical-layered soil isassumed as the grounding system model. Different measuringroutes of the grounding resistance of a grounding system in ver-tical two-layer soil model are shown in Fig. 1, the resistivity

of the soil region in the left side of the vertical boundary islow, equal to 100 m, and the resistivity of the soil re-gion in the right side of the vertical boundary is high, equal to500 m. The measuring current is injected into the center ofthe grounding grid, and we assume equal to 100 m, whichis the side length of the grid. Ordinarily, the fall-of-potentialmethod is applied to measure the grounding resistance of a sub-station recommended by IEEE Std. 81-1983 [9], the apparentgrounding resistance curves in different measuring routes by thefall-of-potential method were analyzed. In our analysis, the truegrounding resistance of the grounding system is calculated bythe definition of grounding resistance, which is the ratio of thegenerated potential of the grounding system and the injected

0885-8977/04$20.00 © 2004 IEEE

1554 IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 19, NO. 4, OCTOBER 2004

Fig. 1. Measuring routes of grounding resistance of a grounding system builtin a vertical two-layer soil model.

measuring current between the grounding system and the re-mote point where the potential is zero.

As we know, when the fall-of-potential method is applied tomeasure the grounding resistance, if the soil is uniform, andthe grounding system is a hemisphere, then the location ofpotential electrode to obtain the true grounding resistance ofthe grounding system is at the point of 0.618 betweenthe grounding system and the current electrode, this point iscalled as the compensated point of the potential electrode.If the soil is nonuniform, and the grounding system is not ahemisphere, the compensated point location of the potentialelectrode would deviate 0.618 , sometimes moving to theside of the grounding system, and sometimes moving to the sideof the current electrode. The compensated point locations ofthe potential electrode in different vertical-layered soil modelswere analyzed in this paper.

A. Grounding System in Low Resistivity Soil Side

As illustrated in Fig. 1, the grounding system is arrangedin the low-resistivity (100 m) soil side and the distancebetween the center of the grounding system and the verticalboundary is . The diagram in Fig. 1 is a sectional drawing, soonly half of the grounding grid is illustrated; it is the same inFigs. 4 and 5. Five different measuring routes were consideredin our analysis. When the current electrode of the measuringcircuit is arranged in high-resistivity (500 m) soil region,three measuring routes were assumed in our analysis, thedistance between the center of the grounding system and thetest current electrode is 2 , 4 , or 8 , respectively, for thelocation 1, 2, or 3 in Fig. 1, the current measuring lead isperpendicular to the vertical boundary. And their respectiveapparent grounding resistance curves in Fig. 2 are presentedas INLOW2D, INLOW4D, and INLOW8D. When the testcurrent electrode is arranged in the soil side with low resis-tivity, the test current electrode is located in the left side of thegrounding system and is perpendicular to the vertical boundary,the distance between the center of the grounding system andthe current electrode is 8 , this measuring route is illustratedas location 4 in Fig. 1, the respective apparent groundingresistance curve in Fig. 2 is presented by INLOWLEFT. An-other discussed case is that the measuring route parallel to thevertical boundary, respective for the location 5 in Fig. 1, and

Fig. 2. Apparent grounding resistance curves when the grounding system isbuilt in the low-resistivity region of a vertical two-layer soil model.

the distance between the center of the grounding system andthe current electrode is 8 , the respective apparent groundingresistance curve in Fig. 2 is presented by PARALLEL. All ofthe apparent grounding resistance curves except curve 4 inFig. 2 have three regions: the left region is obtained when thepotential electrode P is placed at the opposite side with respectto current electrode C. The middle region is obtained whenthe potential electrode is placed between the grounding systemand the current electrode, and the right region is obtained whenthe potential electrode P is located on the same side as currentelectrode C but away from it. In fact, the middle and the rightregions of the apparent grounding resistance curve should becontinuous at the location of the current electrode, but thetest current electrode is small. When the potential probe isnear the current electrode, the respective apparent groundingresistance is very large, so the curve region with high apparentgrounding resistance near the current electrode is cut off, andthe illustrated curves are interrupted.

For the above five different measuring routes, in order to ob-tain the true grounding resistance in the field test, the requiredcompensated point locations for the potential electrode, wherethe true grounding resistance would be measured, were analyzedand shown in Table I. On the other hand, the 0.618 method isstill widely used for the measurement of grounding resistance inChina; therefore, the difference between the true grounding re-sistance and the measured one by 0.618 method was compared,and the error of the 0.618 method is the relative error ofto

(1)

where is the measured grounding resistance by 0.618method, and is the true grounding resistance of thegrounding system.

ZENG et al.: GROUNDING RESISTANCE MEASUREMENT ANALYSIS OF GROUNDING SYSTEM IN VERTICAL-LAYERED SOIL 1555

TABLE IDEMANDED COMPENSATED POINT LOCATIONS OF POTENTIAL ELECTRODE

WHEN THE GROUNDING SYSTEM IS BUILT IN THE LOW-RESISTIVITY

SIDE OF A VERTICAL TWO-LAYER SOIL

Observing the left regions of these curves in Fig. 2, if the po-tential electrode P is placed at the opposite side with respectto the current electrode C in different measuring routes, thatis to say, the current and potential electrodes are arranged in180 angle, even if the potential test lead is longer than ,the measured grounding resistance is still 15% smaller than thetrue one. The soil resistivity is low in the left side, the po-tential falls slowly. And the placed current electrode near thegrounding system leads to the potential of the grounding systembecoming smaller than the respective one when the measuringcurrent is applied between the grounding system and a remotepoint with zero potential. So the potential difference between thegrounding system and the potential electrode is forever smallerthan the potential of the grounding system relative to a remotezero-potential point, which is respective to the true groundingresistance, and is obtained when the measuring current is ap-plied between the grounding system and the remote point withzero potential.

Since the current densities in two sides of the verticalboundary are equal, and the soil resistivity in the right side ishigh, we can conclude that the potential in the right side fallsquickly from the equation (here, is the electricalfield intensity, is the current density, and is the soil resis-tivity). So, in curves INLOW2D, INLOW4D, and INLOW8D,the apparent grounding resistances in the region between thegrounding system and the current electrode increase morequickly than in uniform soil, so their intersecting points withthe true grounding resistance line move to the left side, the de-manded compensated point locations of the potential electrode(defined as the ratio of potential lead length and currentlead length ) respective to the true grounding resistanceare smaller than 0.618 as shown in Table I.

When the test current electrode is arranged in the low-re-sistivity region in the left side of the grounding system, weobserved from curve INLOWLEFT in Fig. 2 that its regionbetween the grounding system and the current electrode isvery even, so its intersecting point with the true groundingresistance line moves to the right side, that is to say, the com-pensated point location of the potential electrode respectiveto the true grounding resistance of the grounding system islarger than 0.618 .

So, for these two cases when the current electrode is arrangedin the right region of the grounding system with high resistivityor in the left region with low resistivity, we can observe thedemanded compensated point locations of the potential elec-trode to obtain the true grounding resistance highly deviate0.618 .

Fig. 3. Apparent grounding resistance curves when the grounding system isbuilt in the high-resistivity region of a vertical two-layer soil model.

When the test current lead is arranged in parallel with thevertical boundary, the demanded compensated point location ofthe potential electrode to obtain the true grounding resistance isabout 0.65 as shown by the curve PARALLEL in Fig. 2,and the measuring error of the 0.618 method is very small, it isonly 1.4%.

Observing the right region of curve INLOW2D, which is inthe right side of the current electrode in Fig. 2, it has anotherintersecting point with the true grounding resistance line, but itis far from the grounding system.

B. Grounding System in High Resistivity Soil Side

As shown in Fig. 1, when the grounding system is built inhigh-resistivity soil region, and now and are 500 mand 100 m, respectively, the distance between the center ofthe grounding system and the vertical boundary is still . Asshown in Fig. 1, when the test current is placed in location 1,location 2, and location 3, the distance between the center of thegrounding system and the current electrode is , , or ,respectively. Their respective apparent grounding resistancecurves in Fig. 3 are presented by INHIGH2D, INHIGH4D,and INHIGH8D. When the current electrode is placed in thehigh-resistivity region, which is in the left side of the groundingsystem and the current measuring lead is perpendicular tothe vertical boundary, the distance between the center of thegrounding system and the current electrode is ; this caseis illustrated as location 4 in Fig. 1, the respective apparentgrounding resistance curve in Fig. 3 is presented by INHIGH-LEFT. Another case is that the measuring lead parallels tothe vertical boundary, respective to location 5 in Fig. 1, andthe distance between the center of the grounding system andthe current electrode is , the respective apparent groundingresistance curve in Fig. 3 is presented by PARALLEL. We mustpoint out that the drawn vertical boundary in Fig. 3 is onlymeaningful for curves 1, 2, and 3.

Analyzing Fig. 3 and Table II, for all five cases of measuringroutes, when the potential electrode P is placed at the oppositeside with respect to current electrode C, the error between the


TABLE IIDEMANDED COMPENSATED POINT LOCATIONS OF POTENTIAL ELECTRODE

WHEN THE GROUNDING SYSTEM IS BUILT IN THE HIGH-RESISTIVITY

REGION OF A VERTICAL TWO-LAYER SOIL MODEL

Fig. 4. Measuring routes of grounding resistance of a grounding system builtacross the vertical boundary in a vertical two-layer soil model.

grounding resistance obtained by the 0.618 method and the trueone is small. The error is about 10% when the distance betweenthe grounding system and the potential electrode is .

From those regions between the grounding system and thecurrent electrode of three curves INHIGH2D, INHIGH4D, andINHIGH8D, we observed those curves are steep in the left sideof vertical boundary, and they have turn points in the verticalboundary, and they become even in the right side of the verticalboundary because the low resistivity in the right side leads to thecurve even. So the intersecting points, with the true groundingresistance line movinge to the right side near the current elec-trode, are larger than 0.618 .

Observing the curve INHIGHLEFT when the current elec-trode is arranged in the left high-resistivity soil region, the de-manded compensated point location of the potential electrode isbigger than 0.618 . From Table II, when the current mea-suring lead is arranged in parallel with the vertical boundary,the demanded potential electrode location is 0.66 , and themeasuring error of the 0.618 method is only 1.6%.

C. Grounding System Constructed Across the VerticalBoundary

Sometimes, a large-scale grounding system is constructedacross the vertical boundary as shown in Fig. 4. Assuming thecenter of the grounding system is on the vertical boundary,three cases were considered in our analysis. The first case isthat the current electrode of the measuring circuit is arranged inthe high-resistivity (500 m) soil side (location 1 in Fig. 4),the current measuring lead is perpendicular to the verticalboundary. The second case is that the current electrode of themeasuring circuit is arranged in the low-resistivity (100 m)

TABLE IIIDEMANDED COMPENSATED POINT LOCATIONS OF POTENTIAL ELECTRODE

WHEN THE GROUNDING SYSTEM IS BUILT ACROSS THE VERTICAL

BOUNDARY OF A VERTICAL TWO-LAYER SOIL MODEL

soil side (location 2 in Fig. 4), and the other case is that thecurrent measuring lead parallels the vertical boundary (location3 in Fig. 4). The distance between the center of the groundingsystem and the current electrode is in all three cases. Theanalyzed results were shown in Table III.

Analyzing Table III, when the current electrode is arrangedin the high-resistivity region, the demanded compensated pointlocation of the potential electrode to obtain the true groundingresistance moves to the side of the grounding system and itis 0.41 . In this case, the error of 0.618 method to mea-sure grounding resistance is very high, reaching 16.3%. Butwhen the current electrode is arranged in the low-resistivity re-gion, the demanded compensated point location of the poten-tial electrode moves to the side of the current electrode and itis 0.75 . When the current electrode is arranged along thevertical boundary, the demanded potential electrode location isclose to 0.618 because the influences of the high-resis-tivity area and the low-resistivity area counteract.

D. Discussion on 0.618 Method

From the above analysis on the compensated point location ofthe potential electrode for the grounding resistance measuringcircuit, the following conclusions can be obtained.

The measured grounding resistance by the 0.618 method hasan obvious error compared with the true grounding resistancein most cases. If the current measuring lead is short (less than

), the error reaches about 50%. Ordinarily, the measuredgrounding resistance by the 0.618 method is higher than the truegrounding resistance when the current electrode is placed in thehigh resistivity soil, and is smaller than the true grounding resis-tance when the current electrode is placed in the low-resistivitysoil region.

If the measuring lead is arranged in parallel with the verticalboundary, the measuring error of the 0.618 method is very small,and is in the permitted range of engineering.

In all measuring routes, the case that the potential electrodeis placed at the opposite side with respect to current electrodeis not recommended, due to the measuring error exceeding 10%even if the distance between the grounding system and the po-tential electrode is longer than .

III. DEMANDED LOCATIONS OF POTENTIAL ELECTRODE

IN VERTICAL THREE-LAYER SOIL MODEL

We often find substations built on a plain with mountains atits two sides, and sometimes we find substations built on the topof a mountain, and there are low resistivity regions on the twosides of the mountain. These two cases can be described by thevertical three-layer soil model as shown in Fig. 5.


Fig. 5. Grounding resistance measuring circuit for a grounding system in avertical three-layer soil model.

Fig. 6. Apparent grounding resistance curve when the grounding system isbuilt in the middle low-resistivity region of a vertical three-layer soil model.

A square grounding grid with a size of 100 100 m anda conductor span of 10 m was still assumed in our analysis.The resistivity of the high-resistivity soil is 500 m, and theresistivity of the low-resistivity soil is 100 m.

A. Grounding System Built in Middle Low-Resistivity Region

As illustrated in Fig. 5, when the grounding system is builtin the middle low-resistivity soil, and high-resistivity regionson its two sides, the distances from the center of the groundingsystem to two vertical boundaries are assumed to be (100 m).If the current electrode is placed in a high-resistivity side and thecurrent measuring lead is perpendicular to the vertical boundarywhen the distance between the grounding system and the currentelectrode is 2 , 4 , and 8 (location 1, location 2, and loca-tion 3, respectively, in Fig. 5), the respective apparent groundingresistance curves are labeled as HLH2D, HLH4D, and HLH8Din Fig. 6. When the current measuring lead with a length ofparallels the vertical boundary (location 4 in Fig. 5), the respec-tive apparent grounding resistance curve is labeled as HLHP8Din Fig. 6. The demanded compensated point locations of the po-tential electrode to obtain the true grounding resistance in dif-ferent measuring routes are illustrated in Table IV.

TABLE IVDEMANDED COMPENSATED POINT LOCATIONS OF POTENTIAL ELECTRODE

WHEN THE GROUNDING SYSTEM IS BUILT IN THE MIDDLE LOW-RESISTIVITY

REGION OF A VERTICAL THREE-LAYER SOIL MODEL

Fig. 7. Apparent grounding resistance curve when the grounding system isbuilt in the middle high-resistivity region of a vertical three-layer soil model.

TABLE VDEMANDED COMPENSATED POINT LOCATIONS OF POTENTIAL ELECTRODE

WHEN THE GROUNDING SYSTEM IS BUILT IN THE MIDDLE HIGH-RESISTIVITY

REGION OF A VERTICAL THREE-LAYER SOIL MODEL

From Fig. 6 and Table IV, the respective apparent groundingresistance curves HLH2D, HLH4D, and HLH8D (the currentelectrode is arranged in high-resistivity region) are steeper thanthe respective curve HLHP8D (the current measuring lead is inparallel with the vertical boundary); therefore, their respectivecompensated point locations of the potential electrode to ob-tain the true grounding resistance move to the direction of thegrounding system; they are smaller than 0.618 .

B. Grounding System Built in Middle High-Resistivity Region

When the grounding system is built in the middle high-re-sistivity region and there are low-resistivity regions on itstwo sides, the analyzed apparent grounding resistance curvesLHL2D, LHL4D, LHL8D, and LHLP8D, respectively, for thelocation 1, location 2, location 3, and location 4 in Fig. 5 areshown in Fig. 7, and the demanded compensated point locationsof the potential electrode are shown in Table V.


From Fig. 7 and Table V, the respective apparent groundingresistance curves LHL2D, LHL4D, and LHL8D (the currentelectrode is arranged in low-resistivity region), are flatter thanthe respective curve LHLP8D (the current measuring lead is inparallel with the vertical boundary); therefore, their respectivecompensated point locations of the potential electrode to obtainthe true grounding resistance move to the direction of the cur-rent electrode and they are larger than 0.618 .

C. Discussions on Analysis Results

Observing Figs. 6 and 7, the following conclusions for thegrounding resistance measurement of grounding system built invertical three-layer soil can be obtained.

If the potential measuring lead is arranged in the oppositedirection of the current measuring lead, even if the length of thepotential measuring lead is longer than , the error betweenthe measured grounding resistance and the true one is largerthan 10%. Especially for the case when the grounding systemis arranged in middle low-resistivity region, the respective erroris up to 25%.

Observing Tables IV and V, when the current measuring leadis in parallel with the vertical boundary, the measuring error ofthe 0.618 method is very small, especially for the case when thegrounding system is built in the middle high-resistivity region;this is similar to the conclusion from the case of vertical two-layer soil model. Therefore, it is better to arrange the measuringcircuit in parallel with the vertical boundary.

IV. CONCLUSION

The test circuit that the potential measuring lead is placed atthe opposite side with respect to the current measuring lead isnot recommended because the measured grounding resistanceis forever much smaller than the true one.

The actual demanded compensated point locations of the po-tential electrode to obtain the true grounding resistance in dif-ferent measuring directions vary widely when the groundingsystem is arranged in different soil regions of vertical-layeredsoil, not as it did in uniform soil.

The measurement error of the 0.618 method to measuregrounding resistance sometimes is very high. The placementthat the measuring circuit parallels the vertical boundary isrecommended in the vertical-layered soil area.

The scientific and suitable measuring method of groundingresistance is based on analyzing the actual soil model and thegrounding system structure to obtain the suitable measuringroute and choose the correct compensated point location of thepotential electrode.

REFERENCES

[1] IEEE Guide for Safety in AC Substation Grounding, ANSI/IEEE Std.80, 2000.

[2] H. G. Sarmiento, R. J. Fortin, and D. Mukhekar, “Substation groundimpedance: Comparative field measurements with high and low currentinjection methods,” IEEE Trans. Power App. Syst., vol. PAS-103, pp.1677–1683, July 1984.

[3] H. G. Sarmiento and R. Velazquez, “Survey of low ground electrodeimpedance measurements,” IEEE Trans. Power App. Syst., vol. PAS-102, pp. 2842–2849, Sept. 1983.

[4] “Grounding for AC Electrical Installations,” China Electrical Power In-dustry Ministry, Beijing, China, DL/T621-1997, 1997.

[5] F. P. Dawalibi and D. Mukhedkar, “Resistance measurement of largegrounding systems,” IEEE Trans. Power App. Syst., vol. PAS-98, pp.2348–2354, June 1979.

[6] S. T. Sobral, S. J. Horta, and D. Mukhedkar, “A proposal for ground mea-surement techniques in substations fed exclusively by power cables,”IEEE Trans. Power Delivery, vol. 3, pp. 1403–1409, Oct. 1988.

[7] F. P. Dawalibi and F. Donoso, “Integrated analysis software forgrounding, EMF, and EMI,” IEEE Comput. Applicat. Power, vol. 6, pp.19–24, Apr. 1993.

[8] F. Dawalibi and N. Barbeito, “Measurements and computations of theperformance of grounding systems buried in multi-layer soils,” IEEETrans. Power Delivery, vol. 9, pp. 1483–1489, Jan. 1994.

[9] Guide for Measuring Earth Resistivity, Ground Impedance, and EarthSurface Potentials of a Ground System, ANSI/IEEE Std. 81, 1983.

[10] F. Dawalibi and C. J. Blattner, “Earth resistivity measurement interpre-tation techniques,” IEEE Trans. Power App. Syst., vol. PAS-103, pp.374–382, Feb. 1984.

Rong Zeng (M’02) was born in Shanxi, China, in 1971. He received the B.Sc.,M.Eng., and Ph.D. degrees from the Department of Electrical Engineering,Tsinghua University, Beijing, China, in 1995, 1997, and 1999, respectively.

Currently, he is an Associate Professor in the Department of Electrical Engi-neering at Tsinghua University, Beijing, China, where he has been since 1999.His research interests include high-voltage technology, grounding technology,power electronics, and distribution system automation.

Jinliang He (M’02–SM’02) was born in Changsha, China, in 1966. He receivedthe B.Sc. degree in electrical engineering from Wuhan University of Hydraulicand Electrical Engineering, Wuhan, China, in 1988, the M.Sc. degree in elec-trical engineering from Chongqing University, Chongqing, China, in 1991, andthe Ph.D. degree in electrical engineering from Tsinghua University, Beijing,China, in 1994.

Currently, he is the Vice Chief of the High Voltage Research Institute atTsinghua University. He became a Lecturer in 1994 and Associate Professor in1996 in the Department of Electrical Engineering at Tsinghua University andfrom 1994 to 1997, was the Head of the High Voltage Laboratory there. From1997 to 1998, he was a Visiting Scientist with the Korea ElectrotechnologyResearch Institute, Changwon, Korea, involved in research on metal-oxidevaristors and high-voltage polymeric metal-oxide surge arresters. In 2001,he was promoted to Professor at Tsinghua University. He is the ChiefEditor of the Journal of Lightning Protection and Standardization. Hisresearch interests include overvoltages and electromagnetic compatibility(EMC) in power systems and electronic systems, grounding technology,power apparatus, dielectric material, and power distribution automation. Heis the author of five books and many technical papers.

Dr. He is a Senior Member of the China Electrotechnology Society, andMember of the International Compumag Society. He is the China representativeof IEC TC 81, the Vice Chief of China Lightning Protection StandardizationTechnology Committee, and Member of Electromagnetic Interference Protec-tion Committee and Transmission Line Committee of China Power ElectricSociety, Member of the China Surge Arrester Standardization TechnologyCommittee, and Member of the Overvoltage and Insulation CoordinationStandardization Technology Committee and Surge Arrester StandardizationTechnology Committee in the electric power industry.

Yanqing Gao (S’02) received the B.Sc. degree in 1999 from the Departmentof Electrical Engineering, Tsinghua University, Beijing, China, where he is cur-rently pursuing the Ph.D. degree.

His research interests include overvoltage analysis in power system,grounding technology, and electromagnetic compatibility (EMC).


Jun Zou was born in Wuhan, China, in 1971. He received the B.S. and M.S. de-grees in electrical engineering in 1994 and 1997, respectively, from ZhengzhouUniversity, Zhengzhou, Henan Province, China, and the Ph.D. degree in elec-trical engineering from Tsinghua University, Beijing, China, in 2001.

He became a Lecturer in the Department of Electrical Engineering, TsinghuaUniversity, in 2001. His research interests include computational electromag-netics and electromagnetic compatibility (EMC).

Zhicheng Guan was born in Jilin, China, in 1944. He received the B.Sc.,M.Eng., and Ph.D. degrees in 1970, 1981, 1984, repsectively, from the Depart-ment of Electrical Engineering, Tsinghua University, Beijing, China.

Currently, he is the Vice President of the Tsinghua University Council. From1984 to 1987, he was a Lecturer and the Director of the High Voltage Laboratoryin the Department of Electrical Engineering, Tsinghua University. From 1988 to1989, he was a Visiting Scholar at the University of Manchester Institute of Sci-ence and Technology (UMIST) Manchester, U.K. From 1989 to 1991, he was anAssociate Professor and the Director of the High Voltage Laboratory, TsinghuaUniversity, Beijing, China. In 1991, he was promoted to Professor at TsinghuaUniversity. From 1992 to 1993, he was the Head of the Department of ElectricalEngineering, Tsinghua University. From 1993 to 1994, he was the AssistantPresident of Tsinghua University, and from 1994 to 1999, he was the Vice Pres-ident of Tsinghua University. His main research interests include high-voltageinsulation and electrical discharge, composite insulators and flashover of con-taminated insulators, electrical environment technology, high–voltage measure-ment, and application of plasma and high-voltage technology in biological andenvironment engineering. He holds many titles in academic societies and is theauthor of many academic papers.

grounding resistance measurement analysis of grounding system in vertical-layered soil

Documents