Standards New Zealand has published a new handbook on electrical installations in dairy sheds, SNZ HB 6117:2014. It provides the recommended trade practice on how to build dairy sheds that minimise stray voltage, which can disturb cows. Users of the handbook include electricians and electrical designers that help to build dairy sheds. It may also help farmers and farm vets to recognise when an electrical problem is affecting cows.
Dairy farming is an important contributor to New Zealand’s economy and the sales of dairy products overseas make up a large part of our export income. Farmers strive to keep their cows healthy and, as far as possible, happy and contented, as this has a big influence on their milk production. However, stray voltage in dairy sheds can agitate cows and impact on their milk production.
Stray voltage can be caused by faulty installation or bonding within a dairy shed. When this happens, it can cause a microshock and the cows may recoil when entering or exiting the shed. They may cause damage to themselves or the shed, or their milk production may drop by up to 30%.
How to fix problems with stray voltage in dairy sheds
The new handbook outlines how to fix problems with stray voltage in dairy sheds. It covers the correct electrical installation practices for new dairy sheds, to reduce the exposure of cows to stray voltage. It also provides recommendations for upgrading existing dairy sheds where there are problems with stray voltage.
Alan Cuthbert, chair of the committee that developed HB 6117, says this is a new document for New Zealand.
‘We initially wrote it as a technical report and issued it for public comment. The comments we received were helpful and meant we could improve the document and raise it to the level of a handbook. Once the handbook has been in use in typical installations for a short period, the committee aims to review it and convert it to a standard.’
Alan Cuthbert says the handbook allows for the alternative use of the TT system of supply, which can help to reduce stray voltage.
‘Use of the TT system is not currently permitted by the Electricity (Safety) Regulations, but this is under active consideration. If use of the TT system is approved, amendments will be required to AS/NZS 3000 to cover the particular TT system requirements.’
The committee included representatives from the Electrical Contractors’ Association of New Zealand, Electrical Safety New Zealand Inc., Electrical Workers’ Registration Board, Electricity Engineers’ Association of New Zealand Inc., Energy Safety – Ministry of Business, Innovation and Employment, Federated Farmers of New Zealand, New Zealand Electrical Institute, and New Zealand Manufacturers' and Exporters' Association.