Contact Voltage Calculations for LV Electrical Programs

There are two primary strategies of safety in opposition to electrical shock, the primary being termed fundamental safety which is safety in opposition to direct contact of individuals or livestock with dwell electrical elements. The second methodology of safety is fault safety which is the safety of individuals or livestock in opposition to contact with uncovered conductive elements which had been made dwell throughout a fault situation.

The contact voltage idea, which is a quite simple however essential security idea, is worried with the latter methodology. The definition of “contact voltages” is these voltages that exist between concurrently accessible uncovered and extraneous conductive elements which will result in the chance of electrical shock within the occasion of {an electrical} fault.

The American Customary NFPA 70E defines “contact potential” as a floor potential gradient distinction that may trigger present circulate from hand handy, hand to foot, or one other path, apart from foot to foot, by means of the physique. The British Customary BS 7671 doesn’t explicitly discuss with “contact voltage” however refers to safety in opposition to electrical shock.

!    Word that simply because a chunk {of electrical} tools is correctly earthed that it isn’t attainable to obtain an electrical shock throughout a fault. That is utterly incorrect.

In a accurately designed electrical set up all uncovered conductive elements which can be touched, both straight or not directly, should be earthed and bonded again to a standard earthing level similar to the principle earth bar. Throughout an earth fault, a contact voltage is developed resulting in a danger of shock which isn’t eradicated by means of earthing or bonding. It’s the function of {the electrical} safety methods throughout such an earth fault to make sure the fault is disconnected quick sufficient to make sure the contact voltage created won’t be dangerous to any individual or livestock which is uncovered.

Keep in mind the chance of hurt to an individual from publicity to the touch voltages is determined by each the voltage magnitude and the period of publicity (fault clearing time).