Lightning Induced Over-voltages in Nuclear Power Plants

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Journal Title

Journal ISSN

Volume Title

Sähkötekniikan korkeakoulu | Master's thesis

Date

2018-12-17

Department

Major/Subject

Power Systems and High Voltage Engineering

Mcode

ELEC3024

Degree programme

AEE - Master’s Programme in Automation and Electrical Engineering (TS2013)

Language

en

Pages

82+8

Series

Abstract

Lightning is an important meteorological process that has vital possible effects on power systems. When a transmission tower is subjected to a lightning stroke, all the equipment in the power system is jeopardized by the induced over-voltages. This study analyzes the lightning induced over-voltages in two different nuclear power plants and proposes protection methods to keep the over-voltages under basic insulation levels of the equipment. Two standard lightning currents of 200 kA 1.2/50 μs and 20 kA 1.2/50 μs have been studied. A lightning source, transmission towers, overhead lines and a surge capacitance have been modeled for both nuclear power plants. For the first nuclear power plant, power transformers of 415/21.5 kV, 15.75/6 kV, and 6/0.4 kV and surge arresters for 400 kV, 15.75 kV, and 6 kV levels have been modeled. For the second nuclear power plant, power transformers of 415/21.5 kV, 20/6.9 kV, 6.9/0.69 kV, and 690/400 V and surge arresters for 400 kV, 20 kV, and 6.9 kV levels have been modeled properly. ATPDraw software, which is a version of EMTP, has been used for the simulations of the overall models. Several scenarios with different numbers of transmission towers, different cases with the combinations of surge arresters, and the effect of the surge capacitance have been investigated. Applicable protection methods with the surge arresters have been proposed according to basic insulation levels.

Description

Supervisor

Lehtonen, Matti

Thesis advisor

Lehtonen, Matti

Keywords

ATPDraw, basic insulation level, lightning, nuclear power plant, over-voltage, surge arrester

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