The previously developed new method for detecting poor electrical contacts in low-voltage electrical installations characterised by the TN protection system has been validated by field measurements performed in residential buildings. The method was developed by the establishment of a correlation between the measured line to earth and line to neutral short circuit loop resistances and the degree of the contact deterioration, i.e. the increase of its electrical resistance. The correlation was established by analysing the data obtained from a large number of documents related to periodic verifications of the quality of low-voltage electrical installations in industrial and administrative facilities (issued by the Laboratory for testing low-voltage electrical and lightning protection installations at the School of Electrical Engineering in Belgrade), as well as the data obtained through a large number of experiments in which the impact of poor electrical contacts on the occurrence of „hot“ spots in low-voltage electrical installations was analysed. In those experiments the influence of an incomplete overlap of the surface of the copper conductor and the contact surface at the electrical component terminal (reduction of the contact surface), a reduced pressure force between the contact surfaces of the copper conductor and the screw of the electrical component terminal (reduction of the torque), and an increased oxide layer at the point of electrical contact (old and/or corrosion-damaged contact) on electrical and thermal behaviour of electrical contacts was investigated. The developed method for detecting poor electrical contacts was applied to the verification of the quality of low-voltage electrical installations in 6 flats of old (10–60 years) residential buildings and the measurement results are presented and analysed in this paper.
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