Arc flash protection of a low voltage motor control centre

Dugdale, Paul Nicholas (2014) Arc flash protection of a low voltage motor control centre. [USQ Project]


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This dissertation seeks to investigate the arc flash hazard incident energy levels throughout the section of the power network that includes the Low Voltage Motor Control Centre (MCC) P6512 at Cristal Pigment Australia’s Kemerton Plant, in Western Australia. It involved researching common industry practice for arc flash hazard studies, and following the requirements set out in the NFPA 70E (2012) and IEEE 1584 (2002) standards.

An audit of all associated plant and equipment was carried out. The power network of the plant was modelled, and a short-circuit evaluation conducted. The network’s protection was studied to establish whether it provided the necessary protection/coordination between devices. Finally, with the aid of arc flash analysis calculation software (‘Power Tools for Windows’), the arc flash study was conducted.

The result of this research has shown that the most dangerous location within the power network is the wiring (and connections) between the low voltage terminals of the MCC 22kV/415VAC supply transformer and the main Air Circuit Breaker (ACB) of the MCC. This is due to the location and type of the upstream protective device in use (i.e. a 22kV fuse upstream of the HV termination of the transformer). When calculated, the clearing time of this fuse was found to be greater than 14 seconds, by which time life could be lost and irreparable damage would occur.

It is recommended that this 22kV fuse should be replaced with a circuit breaker and relay. Calculations showed this could potentially reduce the clearing time to less than 0.75 seconds (an arc flash hazard/risk category of 3). A further recommendation would be to also incorporate an optical arc flash detection system, which could reduce this clearing time even further (to an arc flash hazard/risk category of 1).

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Item Type: USQ Project
Item Status: Live Archive
Additional Information: Bachelor of Engineering (Electrical and Electronic) project.
Faculty/School / Institute/Centre: Historic - Faculty of Health, Engineering and Sciences - School of Mechanical and Electrical Engineering (1 Jul 2013 - 31 Dec 2021)
Supervisors: Helwig, Andreas; Mace, Tim
Date Deposited: 09 Sep 2015 04:46
Last Modified: 13 Aug 2019 04:46
Uncontrolled Keywords: short circuit, incident energy, flash-protection boundary, arc flash protection, low voltage, motor
Fields of Research (2008): 09 Engineering > 0913 Mechanical Engineering > 091302 Automation and Control Engineering
09 Engineering > 0902 Automotive Engineering > 090202 Automotive Engineering Materials
09 Engineering > 0906 Electrical and Electronic Engineering > 090601 Circuits and Systems
Fields of Research (2020): 40 ENGINEERING > 4007 Control engineering, mechatronics and robotics > 400799 Control engineering, mechatronics and robotics not elsewhere classified
40 ENGINEERING > 4002 Automotive engineering > 400202 Automotive engineering materials
40 ENGINEERING > 4008 Electrical engineering > 400801 Circuits and systems

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