Tingle Volts (Stray Voltage Problems in Livestock Production & Milking Parlours)
This is a problem which causes livestock to behave erratically including reluctance to enter the parlour, stampede, low milk yeald, mastitis and reduced feed/water consumption. The risk of tingle Volts may be high on a TN-C-S (PME supply) and is relative to the distance between the distribution companies transformer and the incoming supply terminals at the farm. Problems occur due to the impedance (Ohms) of the combined neutral/earth conductor of the supply cable and the current (Amps) flowing in the neutral conductor of an unbalanced three phase load; the product of the two components being a Voltage. The magnitude of the Voltage varies relative to the current flow. Thus, the PME earthed metalwork within the parlour has a small potential difference (Voltage) above true earth (parlour floor and surrounding ground) and animals simultaneously in contact with both will be sensitive to the current flow through their bodies produced by these conditions.
One solution to this problem is to separate the milking parlour from the PME installation and effectively create a TT system within the parlour. This requires the PME earth from the main farm supply to be disconnected and made safe. The electrical distribution, of the area in question, already protected by a residual current device (RCD) is then earthed using earth electrodes.
There is a lot of information on the internet about this problem, much of it from Canadian sources; a very useful document may be found at
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