Abstract:The distribution of lightning current in the lightning protection system (LPS) and the electrical circuit of two test structures simulating residential buildings was experimentally studied at two research facilities in Florida and in Poland. In Florida, the experiments were conducted using rocket-triggered lightning, and in Poland a mobile current surge generator was employed. The soil in Florida was sandy, while in Poland it was mostly clay. Simulations of lightning current in the LPS and the electrical circuit of each of the test structures were also performed. In this paper, we present results of experiments and numerical modeling of lightning current distribution in different configurations of LPS installed on the test structures at the two sites.
We present a comparison of data obtained during testing of lightning protective system of a residential structure in rocket-triggered lightning experiment at the International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, Florida, and current surge generator experiment at Rzeszow University of Technology in Poland. Three different configurations of LPS were tested in Poland with the dc grounding resistances of the entire system 4.09 : (LPS 1a), 1.65 : (LPS 1b), and 2.88 : (LPS 2). For LPS 1a with three ground rods the value of the peak current entering the electrical circuit neutral was about 56% of the injected current peak, and for LPS 1b with two additional ground rods, each connected by a buried horizontal conductor 5 m long, was about 16%. For LPS 2 with five ground rods interconnected by a buried loop conductor this ratio was 21%. The current waveshapes in the ground rods differed from the injected current waveshapes and the current waveshapes in other parts of the test system, especially, for poorer LPS 1a. The surgegenerator results are consistent with those of triggered-lightning experiments at Camp Blanding, Florida (DeCarlo et al., 2006 [2]).
Investigations were conducted aimed on examination of frequency characteristics of middle to low voltage distribution transformer used to supply residential buildings. Two methods were used for the investigations. First, the impedances (absolute values and angles) of transformer middle and low voltage windings were measured and registered using precision LCR meter for frequency range from 20 Hz to 10 MHz. These impedance characteristics were also examined using voltage surge generator and digital oscilloscope. Registered voltage and current waveforms were denoised and transformed to frequency domain. Apart from investigation of distribution transformer the frequency characteristic of input impedances of typical household electrical appliances were examined using the LCR meter. The conducted measurements are significant part of investigations concerning the lightning and overvoltage protection of residential buildings, which are conducted at the test site belonging to Rzeszow University of Technology.
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