Comparison of Surge Arrester Models

IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 29, NO. 1, FEBRUARY 2014 21

Comparison of Surge Arrester ModelsPablo Mourente Miguel, Member, IEEE

Abstract—This paper deals with the two most used arrestersmodels applied in digital simulations with the Alternative Tran-sients Program, the conventional, and IEEE models. It presentsa model analysis and parameter adjustment procedures to theconventional model. It also presents an application to both modelsof different types of current and voltage surges and even powerfrequency voltage, with a comparison of the results obtainedwith both models and with typical manufacturer data. Whileadjustment of the IEEE model was difficult and laborious, theconventional model presented a straightforward procedure. Theresults obtained show that there is a close agreement betweenthe two models when the surge front time is above s. Theconventional model always presents higher values for the limitingand residual voltages, and better agreement with the typicalmanufacturer data. Thus, the conventional model presents theadvantages of simplicity and more conservative results.

Index Terms—Arresters, hysteresis, impulse testing, simulation,surge protection.

I. INTRODUCTION

L IGHTNING arresters are used to protect equipment andinstallations against overvoltages. The effectiveness of an

arrester to limit an overvoltage will depend on the rate of riseof the overvoltage wave. Several models are used to simulatethe behavior of an arrester on the Alternative Transients Pro-gram (ATP), each using a different approach to represent thehysteresis effect. This paper makes a short description and com-parison of two of the most used models: the conventional modeland the IEEE model. The adjustment of the conventional modelis described and considerations are made regarding the signifi-cance of each component and the procedure of adjustment. Sim-ulation of the application of several current and voltage surgesto both models will enable a comparison between models andwith typical manufacturer data. In addition, a comparison ofthe performance under power frequency will be performed. Thecomparison between results and typical manufacturer data for a120-kV surge arrester will show the applicability of each model.

II. CONVENTIONAL SURGE ARRESTER MODEL

The modeling of a surge arrester on ATP is made with theuse of the nonlinear resistors using one of the following compo-nents: MOV92, NLRES92, or NLRES99. However, these com-ponents reproduce only the resistive part of the arrester and anyelectric circuit has inherent inductance and capacitance.

Manuscript received March 29, 2012; revised August 24, 2012, September24, 2012, and May 02, 2013; accepted August 15, 2013. Date of publicationSeptember 17, 2013; date of current version January 21, 2014. Paper no.TPWRD-00331-2012.The author is with TgDelta Engenharia e Consultoria Ltda, Rio de Janeiro,

RJ 21931-100, Brazil (e-mail: [email protected]).Digital Object Identifier 10.1109/TPWRD.2013.2279835

Fig. 1. Resistive current characteristic of a typical ZnO arrester.

A. Evaluating the Inductance of the Arrester Body

The inductance of the arrester body is estimated as beingequal to the inductance of a finite round conductor, with the di-mensions of the arrester. As stated in [1], the inductance of afinite round conductor is

(1)

where is the length of the conductor and r is the radius of theconductor.The term in (1) represents the internal inductance when

the current density on the conductor is uniform,which is the caseat low frequencies. In operation, the arrester will be submitted tovery large spectra of frequency, from power frequency to severalmegahertz during surge discharge. As the frequency increases,the skin effect phenomena forces the current density to increaseat the surface of the conductor. The penetration depth [2] ofcurrent will be given by

(2)

where is the electric resistivity, is the magnetic permeability,and f is frequency.A difficulty arises in evaluating the electric resistivity of the

ZnO blocks, which is nonlinear. This is done by taking intoaccount the information provided by the manufacturer on theresistive leakage current and on the residual voltage for a surgearrester with 120-kV rated voltage (see the Appendix).The apparent resistance is derived from the curve shown in

Fig. 1, and from this apparent resistance, the electric resistivityof ZnO blocks is estimated.Considering the ZnO blocks with 55-mm diameter and a total

height of 80 cm, the electric resistivity derives from the apparent

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22 IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 29, NO. 1, FEBRUARY 2014

Fig. 2. Apparent resistance of a ZnO arrester with 120 kV.

Fig. 3. Apparent resistivity of ZnO blocks.

resistance. Fig. 3 shows the apparent resistivity, which is currentdependent.Fig. 4 shows the penetration depth in the ZnO blocks at sev-

eral frequencies. Due to the nonlinearity of the ZnO blocks, thepenetration depth will be a function of frequency and currentmagnitude, which is given by

(3)

For frequencies below 1 MHz, the penetration depth on theZnO blocks is much larger than the radius of the blocks. Forfrequencies up to 10 MHz and with high current values, thepenetration depth is still on the same magnitude order of theZnO blocks radius.The frequency range involved in insulation coordination

studies will be below 10 MHz, since above this frequency, thecomponent amplitude is very reduced. The frequency spectrumof a standard 1.2 50- s full and chopped impulse wave andof a 10 kA–1/2 20 s are shown in Figs. 5 and 6.Thus, it may be said that during a surge discharge, current

flows in all or most of the cross section of these blocks, and theinternal inductance of the ZnO blocks is not negligible. Above10 MHz, the penetration depth will be shorter than the radius of

Fig. 4. Penetration depth in ZnO blocks.

Fig. 5. Spectrum of standard impulse, full, and chopped waves.

Fig. 6. Spectrum of 10 kA–1/2 20- s wave.

the ZnO blocks and the very-high-frequency components willbe concentrated close to the surface of the blocks.Just for comparison, the penetration depth on a copper round

conductor would be 8.6 mm at 60 Hz and 0.212 mm at 100 kHz.For an arrester with a rated voltage of 120 kV, the body in-

ductance will be

(4)

MIGUEL: COMPARISON OF SURGE ARRESTER MODELS 23

Fig. 7. Surge arrester usual installation arrangement.

It shall be noted that this figure is very close to the valueprescribed in [3], which is 1 H/m for outdoor arresters.

B. Evaluating the Inductance of the Connecting Leads

The arrester connects to the electric system, which meansthat two lead connections will be necessary: a phase lead anda ground lead. The representation of these connecting leads bylumped impedance is possible when the transit time is muchsmaller than the front time of the propagating surge, which iswritten in the form

(5)

Thus, a 6-m lead may be represented as a lumped inductanceto frequencies up to 5MHz. A grounding lead will have a lengthin the order of 3 m, meaning that this may be represented asa lumped inductance up to 10 MHz. If the overvoltage understudy presents components at higher frequencies or the leadsare longer, it will be necessary to represent the connecting leadsas transmission lines.Fig. 7 shows the usual arrangement of a surge arrester, where

the phase and grounding leads may be seen. Using 85 mm alu-minum cables on both leads, the conductor diameter will be11.79 mm. The penetration depth in an aluminum cable is givenby

(6)

The penetration depth will be 0.273 mm at 100 kHz, whichmeans that the current will be concentrated next to the surface.Thus, the internal inductance is negligible, and the inductanceof each lead will be

Phase lead

(7)

Ground lead

(8)

Fig. 8. Representation of the conventional model of the surge arrester.

C. Total Inductance on the Arrester Branch

The total inductance on the arrester branch will be the sum ofphase lead, arrester body, and ground lead inductances

(8)

Any current discharge will have to flow through this totalinductance, and the corresponding voltage drop will be addedto the voltage limited by the arrester.For frequencies above 100 kHz, which correspond to the

surge discharge regime of the arrester, the inductances of theconnecting leads will be represented only by the external induc-tance, since the skin effect will cause concentration of currentclose to the surface. For the arrester body, even consideringthe skin effect and the nonlinearity of the ZnO blocks, thepenetration depth is bigger than the blocks diameter; thus, theinternal inductance shall be considered.At frequencies on the order of the power frequency, the in-

ductance of the connecting leads will be higher than the calcu-lated values, since the internal inductance will have to be added.However, in that range of frequencies, the current rate is smalland the effect on the limiting voltage by the arrester is very smalland may be neglected.It may be said that the rule of thumb that indicates the use of

a value of 1 H/m for the connecting leads and to the arresterbody will lead to a higher inductance figure.

D. Arrester Capacitance

The arrester capacitance considered was 30 pF, based on fieldmeasurements of arresters of the same voltage class.

E. Representation of the Conventional Model

The conventional model of a surge arrester is presented inFig. 8, including the connecting leads inductances. The modelconsists of a nonlinear resistor connected in series with the ar-rester body inductance and a parallel capacitor. This model issometimes referred to as the Tominaga [4], [5] model.

III. IEEE SURGE ARRESTER MODEL

The IEEE surge arrester model is described in [6], beingformed by two nonlinear resistors (A0 and A1) connected byan RL parallel filter (R1//L1). The capacitance of the arresterbody is connected in parallel with the nonlinear resistor A0. Torepresent the extremities effects of the arrester body, another


Fig. 9. IEEE model of the surge arrester.

Fig. 10. Limiting voltage calculated with conventional and IEEE models sub-mitted to 65 kA–8 20 s current surge, showing a very slight difference be-tween both models.

RL parallel filter (R0//L0) is connected in series with thenonlinear resistor A0. Fig. 9 shows the IEEE model.The adjustment of the model parameters shall match the

residual voltages obtained for the 8 20 s discharge currents.

IV. COMPARING THE CONVENTIONAL AND IEEE MODELS

The purpose of both models is to allow the calculation of theeffect of an arrester in limiting the overvoltages and the dis-charge current. The efforts to adjust the IEEEmodel are cumber-some, since an iterative process has to be used to adjust the pa-rameters of the circuit. The conventional model presents a mucheasier process of adjustment. A comparison between the re-sults obtained with each model submitted to different incomingsurges will be presented.

A. Current Surges

With double exponential current surges applied to bothmodels, the Limiting Voltages will be compared. The term“limiting voltage” refers to the voltage drop measured from thepoint of connection of the arrester to the phase conductor tothe ground; thus, it includes the voltage drops on the conductorleads and on the arrester body. The term “residual voltage”refers to the voltage drop measured only on the arrester body.1) 65 kA–8 20 s: As may be seen in Fig. 10, the behavior

of both models is roughly the same, the conventional model pre-sented a voltage crest of 442.8 kV and the IEEEmodel presented435.4 kV, a difference of 1.7%. Fig. 11 shows the hysteresis looppresented by each model, which are practically identical.Fig. 12 presents the dissipated power and energy on both

models. Both models dissipated the same instantaneous power

Fig. 11. Hysteresis loop formed by conventional and IEEE models submittedto 65 kA–8 20 s current surge, showing a slight difference between bothmodels.

Fig. 12. Dissipated power and energy calculated with conventional and IEEEmodels submitted to 65 kA–8 20- s current surge, showing an exact overlaybetween the results obtained with both models.

Fig. 13. Limiting voltage calculated with conventional and IEEE models sub-mitted to 10 kA–4 10 s current surge, showing a very slight difference be-tween models near the crest of the limiting voltage.

and energy during this current surge. The dissipated energy is555.6 kJ (or 4.63 kJ/kV). The power and energy dissipated bythe IEEE model are the sum of the power and energy dissipatedby components A0 and A1. The component A0 dissipates morethan the component A1 due to the delay introduced by the in-ductance L1.2) 10 kA–4 10 s: Fig. 13 shows the limiting voltage of

both models when submitted to a 10 kA–4 10 s. The con-ventional model presented a voltage crest of 316.3 kV and theIEEE model presented 314.6 kV, a difference of 0.5%.3) 2 kA–1/2 2 s: As may be seen in Figs. 14 and 15, the

behavior of both models is roughly the same, with the conven-tional model presenting a slightly higher residual voltage. The


Fig. 14. Limiting voltage calculated with conventional and IEEE models sub-mitted to 2 kA–1/2 2 s current surge, showing very slight difference betweenboth models.

Fig. 15. Hysteresis loop formed by the conventional and IEEE models sub-mitted to 2 kA–1/2 2 s current surge, showing very slight difference betweenboth models.

Fig. 16. Comparison of the residual voltage informed by the manufacturerand calculated with conventional and IEEE models submitted to 10-kA currentsurges with different front times.

conventional model presented a voltage crest of 310.5 kV, andthe IEEE model presented 303.9 kV, a difference of 2.2%.It is expected that the residual voltage will increase when

the front time of the surge is reduced. Both models presentsuch behavior, as shown in Fig. 16, which is slightly morepronounced on the conventional model. Table IV presents theresidual voltage calculated from both models.

B. Voltage Surges

Double exponential voltage surges will be applied to bothmodels and the limiting voltage compared. Fig. 17 shows thecircuit used to simulate the application of the voltage surges.

TABLE IDATA USED IN THE IEEE MODEL

TABLE IILIMITING VOLTAGES CALCULATED WITH BOTH MODELS

TABLE IIIDISSIPATED ENERGY CALCULATED WITH BOTH MODELS

TABLE IVINFLUENCE OF FRONT TIME ON THE RESIDUAL VOLTAGE


Fig. 17. Circuit used to simulate the application of voltage surges.

Fig. 18. Limiting voltage and current through the arresters’ models duringthe application of full-wave 650 kV–1.2 50- s impulse, showing an exactoverlay between the results for both models.

Fig. 19. Difference between the limiting voltage calculated with both modelsduring the application of full-wave 650 kV–1.2 50- s impulse. The resultsobtained with both models are an exact overlay.

1) Full Wave 650 kV–1.2 50 s: Fig. 18 shows the lim-iting voltage obtained with the application of a standard light-ning impulse with 650 kV peak. The resulting waves are practi-cally identical, in such a manner that it is almost impossible todistinguish the limiting voltage of both models. To emphasizethe agreement of the two models, Fig. 19 shows the differencebetween the calculated limiting voltages. The bigger differencesappear in the front region, but those never exceeded 3.0 kV.2) Chopped Wave 715 kV–1.2 50 s: Fig. 20 shows the

limiting voltage of the conventional and IEEE models duringthe application of a 715-kV chopped wave impulse. Practically,there is no difference between the limiting voltages produced byboth models.3) Full Wave 650 kV–1/2 20 s: Fig. 21 shows the limiting

voltage produced by both models when submitted to a full wave650 kV–1/2 20 s.

Fig. 20. Limiting voltage during the application of chopped wave 715kV–1.2 50 s impulse, showing the same results for both models.

Fig. 21. Limiting voltage and current through the arresters’ models during theapplication of full-wave 650 kV–1/2 20- s impulse, showing a very slightdifference in the results obtained with both models.

Fig. 22. Limiting voltage during the application of chopped wave 715kV–1/2 20- s impulse, showing a very slight difference between the resultsobtained with both models.

4) Chopped Wave 715 kV–1/2 20 s: Fig. 22 shows thelimiting voltage produced by both models when submitted to achopped wave 650 kV–1/2 20 s.

C. Switching Surges

Previous simulations have shown that the differences be-tween the conventional and IEEE model arise when the signalpresents very high frequency components. When the frequencyspectrum is contained below 5 MHz, the results given by bothmodels are practically identical. To confirm this observation, aswitching surge of 350 kV–250 2500 s will be applied toboth models.Fig. 23 shows the limiting voltage calculated according to

both models, which were 263.96 kV for the conventional modeland 263.95 kV for the IEEE model. In addition, the currentthrough each arrester model is nearly identical, 871.95 A forthe conventional model and 871.8 A for the IEEE model.


Fig. 23. Limiting voltage and current through the arrester calculated withboth models during the application of 350 kV–250 2500 s switching surge,showing nearly identical results obtained with both models.

Fig. 24. Instantaneous power dissipated on each arrester calculated with bothmodels during the application of 350 kV–250 2500 s switching surge,showing an exact overlay.

Fig. 24 shows the instantaneous power dissipated by both ar-rester models. The conventional model, which has only one non-linear component, dissipates 230.16 MW. The IEEE model hastwo nonlinear components and dissipates 127.49 MW in com-ponent A0 and 102.63 MW in component A1, amounting to atotal dissipation of 230.12 MW.

D. Power Frequency

At power frequency, it is not usual to apply the arrestersmodels, at least not with this grade of complexity. However,since there are data available on the leakage current of arrestersin service, then it will be interesting to compare both modelswhen submitted to a power frequency voltage. The values ofvoltage applied to the models range from 0.925 to 1.1 times thenominal phase-earth system voltage.Figs. 25 and 26 show the leakage current through the arrester

models. The leakage current presents a level between 0.5 to 2mA, which agrees with the usual field values. The leakage cur-rent through the arrester has a resistive and a capacitive com-ponent. As the applied voltage rises, the resistive component ofthe leakage current increases and more pronounced distortionappears on the current wave.Both models presented exactly the same value for the re-

sistive component of the leakage current, as may be seen inTable VI.

E. Computing Time

Table VII shows simulation time in ATP, using the same cir-cuit and replacing only the arrester model.

Fig. 25. Leakage current through the conventional model with 1-p.u. voltage.

Fig. 26. Leakage current through the IEEE model with 1.05-p.u. voltage.

TABLE VLIMITING VOLTAGES CALCULATED WITH BOTH MODELS

TABLE VILEAKAGE CURRENTS CALCULATED WITH BOTH MODELS

TABLE VIICOMPARISON OF ATP SIMULATION TIMES USING THE SAME CIRCUIT

V. CONCLUSION

Surge arresters are used in electric systems to limit overvolt-ages, which otherwise may compromise the insulation of equip-


Fig. 27. Residual voltage versus front time to an arrester with 120 kV.

TABLE VIIITYPICAL CHARACTERISTIC DATA SUPPLIED BY THE MANUFACTURER

ment and installations. It is important to have means to eval-uate the performance of the arresters, which is done by per-forming digital simulations of the electric system. In these sim-ulations, the limiting voltages on several points of interest aredetermined. In addition, the current through the arrester and thedissipated power and energy have to be evaluated in order tochoose an arrester, which is able to operate in electric systems.The IEEEmodel necessitates that the user transform the man-

ufacturer data presented for one nonlinear resistor in data relatedto two nonlinear resistors. The conventional model uses a verysimple adjustment, the manufacturer data are directly used onthe nonlinear resistor and inductances added in series with thisnonlinear resistor. The calculation of the inductances on the ar-rester branch, as proposed here, is very simple.A comparison of the results with the simple conventional

model and the more complex IEEE model have shown that dif-ferences in the results presented by both models are significantonly when the front time of the current or voltage surge is below

s. For front times above 1 s, the results obtained are

practically identical. The departure observed in the results pre-sented by the conventional model from manufacturer data atfront times below s may be attributed to the penetrationdepth at very high frequencies being smaller than the radius ofthe ZnO blocks. Fig. 4 illustrates this. For 10 MHz, the pene-tration depth is 48 mm at 10 kA. Thus, the inductance of thearrester body, which in the adjusted parameters included the in-ternal inductance of the ZnO blocks, will be higher than the realvalue and produce a higher voltage drop.Both the conventional and IEEE model reproduce the known

behavior of presenting a higher crest value for surges with ashort-time front. A comparison with typical manufacturer-sup-plied data for the residual voltage of a surge arrester with

120 kV has shown that the IEEE model presents lowervalues, and the conventional model presented better resultsin surge front times up to 0.8 s, where this model started topresent higher values. This is an advantage, since the resultsare conservative.A comparison of both models submitted to the power fre-

quency presented exactly the same results, which were in agree-ment with the fieldmeasurements of leakage current on the sametype of arresters.

APPENDIX

Data used in this paper relate to an arrester with a ratedvoltage of 120 kV. The characteristics informed by the manu-facturer are summarized in Fig. 27 and Table VIII.

REFERENCES[1] P. M. Anderson, Analysis of Faulted Power Systems. New York:

Wiley, 1995, p. 470.[2] J. D. Kraus and K. R. Carver, Electromagnetics, 2nd ed. Tokyo,

Japan: McGraw-Hill Kogakusha, 1973, p. 406.[3] Surge Arresters—Part 4: Metal-Oxide Surge Arresters Without Gaps

for a.c. Systems,, IEC 60099-4, Ed.2.2—2009-05.[4] S. Tominaga, K. Azumi, Y. Shibuya, M. Imataki, Y. Fujiwara, and S.

Nichida, “Protective performance of metal oxide surge arrester basedon the dynamic v-i characteristics,” IEEE Trans. Power App. Syst., vol.PAS-98, no. 6, pp. 1860–1871, Nov. 1979.

[5] A. Bayadi, N. Harid, K. Zehar, and S. Belkhiat, “Simulation of metaloxide surge arrester dynamic behavior under fast transients,” presentedat the Int. Conf. Power Syst. Transients, New Orleans, LA, USA, 2003.

[6] IEEE Guide for Application of Metal-Oxide Surge Arresters for Alter-nating-Current Systems, IEEE Standard C62.22-2009, Jul. 2009.

[7] S. S. Wanderley and P. M. Miguel, “Comparação dos modelos de para-raios utilizados para simulação no ATP,” presented at the XXI Sem-inário Naciaonal de Producão e Transmissão de Energia Elétrica, Flo-rianópolis, SC, Brazil, 2011.

Pablo Mourente Miguel (M’11) was born in ElFerrol, Spain, in August 1951. He graduated inelectrical engineering from the Universidade Federaldo Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil, in1975 and received the M.Sc. and D.Sc. degrees fromthe Alberto Luiz Coimba Institute – Graduate Schooland Research in Engineering (COPPE-UFRJ) in1981 and 1984, respectively.Currently, he is a Consulting Engineer with

TgDelta Engenharia e Consultoria Ltd., Rio deJaneiro.

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Comparison of Surge Arrester Models