ZEMCH 2019 International Conference Proceedings April.2020 | Page 408
1. Introduction
There has been an increased attention to the photovoltaic systems during the last decade owing to
the many advantages. As a result, PV systems are being applicated in various places including lakes,
seas, exterior walls of buildings, and roofs as well as land. Above all, Building Integrated Photovoltaic
Systems (BIPV) replacing building finishing material with photovoltaic module has been increasing
because it has advantages in terms of economy since the site is not necessary for the installation space
compared to conventional photovoltaic systems [1‐3].
The deployment of favorable conditions across worldwide will support a wide BIPV applications
extension. Quite often the PV modules are installed on top of the existing building structure and do not
provide any additional function. That acknowledges the added effort and the extra cost of integrating
PV as part of the building envelope. BIPV systems present significant challenges with respect to energy
efficiency, reliability and availability of PV arrays. In such systems, the PV panels replace roof tops, and
other building components such as windows [4].
As the building integrated PV system is installed in buildings such as buildings in the form of the
exterior of buildings, it is possible that a reduction in the insulation performance of BIPV modules,
cables can result in an electric shock therefore electrical safety must be ensured. This risk of electric
shock may vary depending on the inverter insulation method and the electrical continuity value of the
earth [5]. In this paper, as a study for improving electrical safety in BIPV systems, we considered the
hazard of electrical safety in the BIPV systems applied non‐isolated inverter and conducted analysis
risk of electric shock through verification experiment.
2. Safety issues in BIPV systems
2.1. electrical continuity
PV facilities ground BIPV frames by using mostly building structure ground to secure electrical
safety. The structural ground means that the large metal structure in the basement of the building is
mash‐grounded using an electric pole, and is used for equipotential bonding using steel and rebars to
make the difference in potential equal to or less than several mV. IEC 62305‐3 and ʹCommon and
Integrated Ground Inspection Handlingʹ of the Korea Electric Safety Corporation require that the
electrical resistance value measured between the exposed conductive part and an extraneous
conductive part should be less than 0.2[Ω]. If electrical continuity of additional installations due to
mechanical connection problems or problems with the ground terminals due to installation of the
external system, the BIPV systems can cause potential difference in both ends when the body comes
into contact with all of the systemʹs externalities, such as the extraneous conductive parts and gas pipes
when there is an electrical continuity problem due to the installation of the external system.
2.2. Non‐isolated inveter
Conventional inverters are built with an internal transformer that synchronizes the DC voltage
with the AC output. These inverter designs include either high or low frequency transformers that
electrically isolate the AC and DC systems [6]. The main feature of its layout resides in the fact that the
presence of a ground‐fault in the DC side involves no flowing of the current on the network, thanks to
the presence of the transformer. But the disadvantage is low efficiencies and the package size is bigger
than a non‐isolated inverter. Despite its advantages in electrical safety, non‐insulated inverter systems
have been used a lot recently.
The advantages most commonly attributed to non‐isolated inverters include higher efficiency,
improved economics and increased ground‐fault sensitivity. However, these non‐isolated inverters
suffer from some drawbacks, such as a common‐mode voltage or ground leakage current issue between
the grid and PV systems [7]. In addition, since the AC and DC systems are not electrically separated,
accident currents can be passed through the inverter. In case of a DC ground‐fault, the current flows
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ZEMCH 2019 International Conference l Seoul, Korea