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Failure of electrical short circuit protection on underground diesel powered plant

failure of alternator short circuit protection
Failure of electrical short circuit protection may increase risks on underground coal loaders
The Queensland Department of Natural Resources and Mines recently released an urgent Safety Newsflash concerning a failure of electrical short circuit protection on diesel-powered plant used in underground coal mines.

Overview of Incident

 
During a routine regulatory detailed internal electrical inspection on an underground loader, it was found that the short circuit protection would not trip the alternator when the positive and negative supply cables were shorted together.
 
Further testing on other diesel vehicles revealed the same condition. Preliminary investigation has
found there to be an issue with the cable cross-sectional area and length affecting
the fault loop impedance of the circuits on the machine.
 

Things to Consider

• Do your site maintenance procedures for alternator protection devices include testing at the furthest point (worst case scenario) in the circuit?
• Has the fault loop impedance been considered in the installation of cables on underground mining equipment?
• Refer to original equipment suppliers for guidance on installation, maintenance and usage, including cable sizing and maximum cable lengths.

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