### Links

- Electrical Power Systems Laboratory - University of Bologna
- EMC Laboratory - EPFL
- IEEE Power Engineering Society
- IEEE Xplore
- Elsevier Sciencedirect
- International Conference on Lightning Protection - ICLP
- International Conference on Power Systems Transients - IPST
- EMTP-RV

### Recent Papers

- A. Borghetti, F. Napolitano, C. A. Nucci, M. Paolone. (2013). Effects of nearby buildings on lightning induced voltages on overhead power distribution lines. ELECTRIC POWER SYSTEMS RESEARCH. vol. 94, pp. 38 - 45 ISSN: 0378-7796.
- F. Napolitano, A. Borghetti, C. A. Nucci, F. Rachidi, M. Paolone. (2013) Use of the full-wave Finite Element Method for the numerical electromagnetic analysis of LEMP and its coupling to overhead lines. ELECTRIC POWER SYSTEMS RESEARCH. vol. 94, pp. 24 - 29 ISSN: 0378-7796.
- Other Papers...

# INTRODUCTION

**LIOV code **

The LIOV (Lightning-Induced OverVoltage) code, is a computer code which allows for the calculation of lightning-induced voltages on multiconductor lines above a lossy soil as a function of the line geometry, lightning current waveshape, return-stroke velocity, soil electrical parameters, etc. (see, e.g. [1])

The evaluation of lightning induced overvoltages is generally performed in the following way:

- the lightning return-stroke electromagnetic field change is calculated at a number of points along the line employing a lightning return-stroke model, namely a model that describes the spatial and temporal distribution of the return stroke current along the channel. To this end, the return stroke channel is generally considered as a straight, vertical antenna.

- The evaluated electromagnetic fields are used to calculate the induced overvoltages making use of a field-to-transmission line coupling model which describes the interaction between the LEMP and the line conductors.

The Modified Tranmission Line model with Exponential Decay (MTLE) [2,3] is used for the specification of the spatial-temporal distribution of current alsong the lightning return stroke channel.

For the calculation of the vertical component of the electric field, the assumption of a perfectly conducting ground was considered (this assumption has been shown to be reasonable for distances not exceeding a few kilometers or so). On the other hand, the horizontal component of the electric field is appreciably affected by the finite conductivity of the ground. This component is computed using the Cooray-Rubinstein formula [4,5]. Note that in the freely downloadable version, the line and ground are supposed to be perfect conductors.

For the evaluation of the electromagnetic coupling, the implemented model in LIOV is based on the transmission line theory and on the field-to-transmission line coupling model of Agrawal et al. [6]. The coupling equations are solved using the finite difference-time domain-technique (FDTD).

The LIOV code has been experimentally validated using a number of experimental data related to natural and triggered lightning, Nuclear Electromagnetic Pulse Simulators and reduced scale models (see [7,8] for a review).

The full version of the LIOV code takes into account a certain number of features such as frequency dependence of line parameters [9], multiconductor lines [10], leader induction effects [11], corona phenomenon [12], nonlinear components (surge protective devices) and shielding wires [13], etc.

**LIOV code and IEEE **

The LIOV code has been applied in the IEEE St 1410 [14] in combination with the Monte Carlo method in order to infer the lightning performance of a typical distribution line. The relevant procedure is described in [15,16].

**LIOV code and CIGRE**

The LIOV code has been referred in some CIGRE Technical Brochure [e.g. 17,18]. It is worth mentioning that within both frameworks (CIGRE and IEEE) the LIOV code is assumed as the ‘reference’ for lightning-induced overvoltage appraisal.

**LIOV-EMTP code**

In order to deal with distribution networks having more complex, realistic topology and configuration, the LIOV code has been interfaced with the Electromagnetic Transient Program (EMTP). The interface is described in [19-21].

[1] C.A. Nucci and F. Rachidi, "Interaction of electromagnetic fields generated by lightning with overhead electrical networks," in *The Lightning Flash*, V. Cooray, Ed. London: IEE, 2003, pp. 425-478.

[2] C. A. Nucci, C. Mazzetti, F. Rachidi, M. Ianoz, "On lightning return stroke models for LEMP calculations", *19th International Conference on Lightning Protection*, Graz, April 1988.

[3] F. Rachidi, C.A. Nucci, "On the Master, Lin, Uman, Standler and the Modified Transmission Line lightning return stroke current models", *Journal of Geophysical Research*, Vol. 95, pp. 20389-20394, Nov. 1990.

[4] M. Rubinstein, "An approximate fomula for the calculation of the horizontal electric field from lightning at close, intermediate, and long range," *IEEE Trans. on Electromagnetic Compatibility, *vol. 38, pp. 531-535, 1996 1996.

[5] V. Cooray, "Horizontal fields generated by return strokes," *Radio Science, *vol. 27, pp. 529-37, 1992; _ “Some considerations on the "Cooray-Rubinstein" formulation used in deriving the horizontal electric field of lightning return strokes over finitely conducting ground”, IEEE Trans on EMC, Vol. 44, No. 4, November 2002.

[6] A. K. Agrawal, H. J. Price, and S. H. Gurbaxani, "Transient response of multiconductor transmission lines excited by a nonuniform electromagnetic field," *IEEE Transactions on Electromagnetic Compatibility, *vol. 22, pp. 119-29, May 1980.

[7] M. Paolone, F. Rachidi, A. Borghetti, C.A. Nucci, V.A. Rakov, M.A. Uman, "Lightning Electromagnetic Field Coupling to Overhead Lines: Theory, Numerical Simulations and Experimental Validation", *IEEE Transactions on Electromagnetic Compatibility*, Vol. 51, No. 3, August2009, pp. 532-547.

[8] F. Rachidi, "A Review of Field-to-Transmission Line Coupling Models with Special Emphasis to Lightning-Induced Voltages", IEEE Transactions on Electromagnetic Compatibility, Vol 54, No. 4, pp. 898 - 911, 2012.

[9] F. Rachidi, C.A. Nucci, M. Ianoz, C. Mazzetti, "Influence of a lossy ground on lightning-induced voltages on overhead lines", *IEEE Trans. on Electromagnetic Compatibility*, Vol. 38, No. 3, August 1996.

[10] F. Rachidi, C.A. Nucci, M. Ianoz, C. Mazzetti, "Response of multiconductor power lines to nearby lightning return stroke electromagnetic fields", *IEEE Trans. on Power Delivery*, Vol. 12, pp. 1404-1411, July 1997.

[11] F. Rachidi, M. Rubinstein, C.A. Nucci, S. Guerrieri, "Voltages induced on overhead lines by dart leaders and subsequent return strokes in natural and rocket-triggered lightning", *IEEE Trans. on Electromagnetic Compatibility*, Vol. 39, No. 2, May 1997.

[12] C.A. Nucci, S. Guerrieri, M.T. Correia de Barros, F. Rachidi, "Influence of corona on the voltages induced by nearby lightning on overhead distribution lines", *IEEE Trans. on Power Delivery*, Vol. 15, No. 4, pp. 1265-1273, October 2000.

[13] M. Paolone, C.A. Nucci, E. Petrache and F. Rachidi, "Mitigation of Lightning-Induced Overvoltages in Medium Voltage Distribution Lines by Means of Periodical Grounding of Shielding Wires and of Surge Arresters: Modelling and Experimental Validation", IEEE Trans. on Power Delivery, Vol. 19, No. 1, pp. 423-431, Jan. 2004.

[14] IEEE St 1410: “IEEE Guide for Improving the Lightning Performance of Electric Power Overhead Distribution Lines” IEEE PES, New York, January 28, 2011.

[15] A. Borghetti, C.A. Nucci, “Estimation of the Frequency Distribution of Lightning-induced Voltages on an Overhead Line Above a Lossy Ground: a Sensitivity Analysis,” Proc. 24th Int. Conf. on Lightning Protection, pp. 306-313, Birmingham, UK, September 14-18, 1998.

[16] A. Borghetti, C.A. Nucci, M. Paolone, “An Improved Procedure for the Assessment of Overhead Line Indirect Lightning Performance and its Comparison with the IEEE Std. 1410 Method,” IEEE Trans on Power Delivery, vol. 22, no. 1, pp. 684 – 692, Jan 2007.

[17] CIGRE-CIRED Joint Working Group C4.402 (convener : F. Rachidi) "Protection of MV and LV Networks against Lightning. Part I: Common Topics", CIGRE Technical Brochure No 287, December 2005

[18] __ “Part II: Lightning protection of Medium Voltage Networks”, December 2010.

[19] C. A. Nucci, V. Bardazzi, R. Iorio, A. Mansoldo, and A. Porrino, "A code for the calculation of lightning-induced overvoltages and its interface with the Electromagnetic Transient program," in *22nd International Conference on Lightning Protection (ICLP)*, Budapest, Hungary, 1994.

[20] A. Borghetti, A. Gutierrez, C. A. Nucci, M. Paolone, E. Petrache, and F. Rachidi, "Lightning-induced voltages on complex distribution systems: models, advanced software tools and experimental validation," *Journal of Electrostatics, *vol. 60, pp. 163-174, 2004.

[21] F. Napolitano, A. Borghetti, C. A. Nucci, M. Paolone, F. Rachidi, and J. Mahserejian, "An advanced interface between the LIOV code and the EMTP-RV," in *29th International Conference on Lightning Protection (ICLP)*, Uppsala, Sweden, 2008.

### Multimedia section... coming soon

### Visit the tutorial subsection to learn more about the LIOV code

**Direct link to examples**:

coming soon..

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