Analysis Of Earth Leakage Circuit Breaker (ELCB) Nuisance Tripping Due To Earthing Resistance Value

Aziz, Izzatul Liyana (2018) Analysis Of Earth Leakage Circuit Breaker (ELCB) Nuisance Tripping Due To Earthing Resistance Value. Project Report. Universiti Teknikal Malaysia Melaka, Melaka, Malaysia. (Submitted)

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Abstract

Protection against leakage current is vital in low voltage system (LV) to protect humans and equipment from electric shocks and fire risk. Residual Current Device (RCD) is a protective device, which is more reliable version of earth leakage circuit breaker (ELCB) used for protection against small leakage current. This device is a current operated device which designed to disconnect the main power supply circuit whenever fault is occurred, where the measured value of phase current and neutral current is different. Also, RCD is made to be very sensitive to the residual current in order to protect equipment and personnel effectively. However, this device is prone to tripping under the non-fault condition due to the high sensitivity and some cases make the device delay to operate. This inappropriate tripping also known as nuisance tripping, where normally the nuisance tripping of RCD is influenced by the improper earthing system, high frequency from power supplied and presence of harmonics in signal waveforms. Besides, the use of resistive and inductive loads changed the behavior of RCD as the high-power consumption delayed the operation of RCD when earth fault current occurred. Hereafter, this report is provided to investigate the residual operating current and operating time of RCD behavior towards the poor earthing resistance value, where the value of resistance is higher than the standard buildings installation. The sensitivity of RCD sample used in this research is 30mA type-AC. The voltage and frequency of circuit tested for RCD sample followed the standard buildings requirement which is 240V with frequency of 50Hz. Meanwhile, the high earthing resistance value is chosen from 1kΩ to 3.5kΩ for this research. The residual operating current of RCD is measured by using current probe (Tektronix A622) and oscilloscope while the operating time of RCD is measured by using RCD Tester (KYORITSU Model 5402D). The results show earthing system with high resistance value affect the operating time of RCD, thus lead to nuisance tripping.

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