Modelling Neutral to Ground Voltage (NTGV) on the Educational Building

Abstract

The neutral conductors of grounded power systems are not always at zero potential with regard to the earth beneath them because of the nature of the system. This potential is also known as neutral to ground voltage (NTGV). Based on the IEEE Std 1159, the NTGV threshold should be below than 20V peak. However, due to numerous circumstances, such as the lightning strikes, high impedance of the return current path, non-linear load and grounding conditions, its magnitude tends to surpass the tolerable threshold value. Excess NTGV can lead to significant losses and safety risks for electrical consumers, such as erroneous equipment functioning and failure, frequent tripping, and electromagnetic interference. Furthermore, in order to investigate the effects and factors of high NTGV in educational building and distribution systems, a credible model must be used. The key focus of this paper is to determine the magnitude and form of the NTGV with respect to the neutral current and phase currents. Then, this paper discussed the model of the three-phase, four-wire underground cable in the educational building, comparing measurement data and simulation outcomes for the NTGV, neutral current and phase current. In this model, an XLPE cable is employed to connect the transformer and the load. The load at the educational building is constructed by combining the RL load and current sourcing. To validate the model, it is tested on two separate datasets from educational buildings. The simulation results are comparable to the measurement data. In conclusion, the purpose of determining the magnitude and form of the NTGV was met, and this model may be utilised to investigate the factors that contribute to elevated NTGV in educational buildings.