Understanding the effect your earth protection system has on the touch potentials on electrical equipment

Do you understand the effect your earth protection system has on the touch potentials on electrical equipment?

Is your protection system compliant with the step and touch potentials specified by AS/NZS4871.1:2010?

ResTech can provide you with independent consultation to help you understand and manage the risks.

Touch potential studies for mining environments

ResTech offers a systematic study on the effect of earth protection systems on touch potentials on electrical equipment.

The study considers the ‘as new’ case of high integrity earthing and the more realistic case where some degradation is present. It produces results for periods of pre-fault, fault present and after the operation of various protection equipment including fuses and contactors.

To undertake these studies, ResTech has developed a range of models that can be applied to particular mining electrical networks to study the likelihood of dangerous touch potentials in un-faulted and earth faulted scenarios. These models account for the complex interaction of multiple Variable Speed Drives and EMC filters where unexpected issues have arisen. They reflect the alternate paths taken by, and the equipment response to, fault currents of various frequencies involved with non-linear loads.

This assessment will include a report demonstrating scenarios where touch potentials are acceptable, unacceptable or uncertain.

Compliance assessment for earth protection according to AS/NZS 4871.1:2010.

AS/NZS 4871.1:2010 prescribes that earthing protection strategies in mines and quarries by “such that the level of step and touch potential and time exposed is limited to acceptable levels”. The complexity of modern mines means that ensuring compliance with this standard is not straightforward. In particular, the presence of VSDs raises the possibility of undetected earth leakage, and consequently undetected hazardous touch potentials.

Review your application of the standard with an independent assessment from ResTech.

ResTech has developed a series of tools that may be applied to provide evidence to the compliance of your earth protection system with the step and touch potential specified by AS/NZS 4871.1:2010. ResTech will consider the effect of multiple return paths in the presence of an earth fault and derive from this the best and worst case touch potentials and compare them with the limits described in the standard. ResTech can then provide an independently assessed report on earth protection compliance and offer mitigation strategies if the assessment reveals shortcomings.

For more information or to arrange an assessment please contact Heath Raftery at ResTech by email or phone 02 4033 9155.
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