Mohamad Nur Khairul Hafizi Rohani
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Preferred name
Mohamad Nur Khairul Hafizi Rohani
Official Name
Mohamad Nur Khairul Hafizi, Rohani
Alternative Name
Hafizi Rohani, Mohamad Nur Khairul
Rohani, M. N.K.H.
Main Affiliation
Scopus Author ID
57189241581
Researcher ID
G-4075-2017

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  • Publication
    Protection Relay Setting based on Overcurrent Phenomena in Commercial Building
    ( 2024-03-01)
    Isyraq Faizzi Mohammad
    ;
    Mohamad Nur Khairul Hafizi Rohani
    ;
    Afifah Shuhada Rosmi
    ;
    Baharuddin Ismail
    ;
    Muhamad Hatta Hussain
    ;
    Abdullahi Abubakar Mas’ud
    ;
    Firdaus Muhammad-Sukki
    Nowadays, every single distribution system needs to install an appropriate relay to keep the system safe. The operational and commonly recommended relay for distribution systems is the overcurrent (OC) relay. Throughout the distribution system, the protective relay is one of the methods that can detect and protect the location according to its observation from any fault from abnormal activity. Note that time coordination between the protective equipment relay needs to be a minimum of time interruption to prevent faults occurs. The ideal setting for all coordination protection relays is necessary to protect the device against electrical failure and interference. This paper analyzes the real results data collected for the selected commercial building of an OC relay implemented in a distribution board for high voltage and low voltage downward at a commercial building. All the parameters need to be clarified first before testing has been made and measurement is carried out using the MICROTEST 860 set. Based on the analysis, it proves that according to the IEC Standard of 0.10-time multiplier Setting (TMS) is practical to be used to obtain the operation time in seconds for the current curve set. Other than that, the results show that the normal inverse curve from manual calculation results is more accurate compared to the service setting (SS) made based on the incoming setting in a real commercial building. The case study for OC relay setting is related between current injection and time-tripping, which complies with the IEC 60255-3 standard using its formula. This method was applied to determine the characteristics of the curve. Hence, this research successfully determined the proper methods for the OC relay setting for the power distribution system. Besides, the feasibility and efficiency of OC relay data transmission are tested and checked successfully to implement the measurement method in the relay coordination study.
  • Publication
    FEA-Based simulation of accelerated ageing in a power cable due to sustained partial discharge activities in a Spherical Cavity
    (Springer, 2023)
    Umar Musa
    ;
    Abdullahi A. Mati
    ;
    Abdullahi Mas'ud
    ;
    Gaddafi Sani Shehu
    ;
    Johnatan M. Rodríguez-Serna
    ;
    Saud J. Al-Shammari
    ;
    Mohamad Nur Khairul Hafizi Rohani
    ;
    Firdaus Muhammad-Sukki
    The reliability of electrical assets is greatly influenced by the quality of their insulations. Key power installations such as power cables are manufactured with polymer-based materials as part of their insulation system. However, accelerated ageing of equipment insulations due to manifestation of defect(s), and partial discharges (PDs) can offset the operation of these systems or even lead to breakdowns. In this study, a non-deterministic model to simulate the phenomenon of repetitive discharges in a spherical air-filled cavity within a practical power cable has been investigated. In addition, the work contributes to the understanding of PD behaviour and field distribution under different ageing conditions considering changes in cavity surface conductivity. First, a section of the practical XLPE cable containing the cavity is developed in 2D using COMSOL software, and a finite element analysis (FEA) of the electric field distribution within the cable insulation is performed. The magnitude of the cavity local field, that is enough to ignite a PD, is investigated. Alongside the COMSOL model, the activity of sustained internal PD is simulated in MATLAB by introducing a random sample generating factor and adjusting the model’s parameters to obtain something close to the practical results. Furthermore, the impact of continuous PD in the power cable under different cavity dimensions and surface conductivity is likewise investigated, and a phase resolved PD (PRPD) pattern is established. The result shows that the magnitude and number of PDs per cycle increase as the cavity size and its surface conductivity increase. Finally, when the cavity surface conductivity rises, the amplitude of the electric field generated by the surface charge distribution and the number of PDs per cycle approach their maximum values.