ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades MEN System in NZ

The system here in New Zealand is a M.E.N system or Multiple Earth Neutral, standard low voltage is 230v/400v, polyphase,.

Our transmission is in the form of 220 or 110 KV for transmission, stepped to 33KV for distribution then 11KV at supply subs, 400v to roadside.

All installations have a driven earth rod or bare copper where required. And a return to the supply transformer called a "Neutral cable" , the center point of the "Star" ( I think some call these "Wye") transformer is also referenced to earth.

When wiring an installation we don’t use a ringmain i think they have in the UK, Instead a radial feed from the distribution board. With say 5-6 outlets (doubles) normally this would be run in 2.5mm2 TPS but 1.5mm2 would be suitable if cable run is kept short, fused by a 20 Amp MCB. RCD protection is not mandatory (YET) unless run out doors or in a require zone these must operate at, (Let me get this right) 30mA within 300 ms for personal protection.
Minimum earthing conductor size is 4mm2 and 16mm2 for works.
There is lot else no doubt, if you are interested let me know,
nice to see you all again
Craig :-)

~Good to hear from you Craig~

RCD @ 30 ma?, sounds like our GFPE

(Ground Fault Protection of Equipment)

RCD - residual current device.
GFI - ground fault interrupter
RCCB - residual current circuit-breaker
CBELCB - core balance earth leakage circuit breaker.
all pages in the same book i reckon, should be set to trip for an out of balance current of no more than 30 mA on this side of the pacific anyways

Cheers Craig

O App-- In your area, what is the smallest customer that can get 400Y in their home/business?

Hi Craig,

Thanks for posting the info.

It sounds as though your MEN system is equivalent to the British PME (Protective Multiple Earthing) arrangement.

Does every house have its earth bonded to the incoming neutral, or do you have other grounding/earthing systems in use as in the U.K.?

The 30mA RCD/GFI setting is common here now as well, although 100mA is also still available and installed in some cases. Do you have "split-load" panels so that some circuits can share a GFI?

TPS Tough Plastic Sheath???

"In your area, what is the smallest customer that can get 400Y in their home/business"

This could be requested by a house owner, there is no minimum size, indeed is part of the work we find ourselves doing more often, People are more inclined to have small workshops at home etc.. or heated pools, and Spa's quite common - But not Cheap!

"Does every house have its earth bonded to the incoming neutral, or do you have other grounding/earthing systems in use as in the U.K.?"
Yes every seperate installation has a removable link in the switchboard between E and N, other boards feed from that board may or may not depending on what type they are. Also the Neutral point is tied to earth at the transformer.

"Do you have "split-load" panels so that some circuits can share a GFI?"
hmmm im not sure what you mean on with one, but normally the RCDS would only feed the one circuit i.e. A run form the board bathroom Laundry etc any damp area where extra protection maybe prudent. possibly a PP outside for waterblaster etc as long as there werent too many or the run was to far.

Hope that helped
Cheers Craig

The split-load boards here are often installed now with a PME or other solidly grounded system. There's a D.P. main switch feeding a small busbar from which are tapped MCBs for lighting and sometimes other equipment. That busbar also feeds into a large (e.g. 80A, 30mA) RCD which feeds a second busbar from which are tapped MCBs for the other circuits.

The idea is that the RCD/GFI provides added protection for wall outlets etc., but the lights will stay on if it trips. More of a problem with a local-ground system as this would need two RCDs and would start getting expensive.

Do you run separate branch circuits for lights in NZ?

"Do you run separate branch circuits for lights in NZ?"
Yes all installations require at least 2 light circuits (within reason) Many require more than 2, Same principal as power outlets,
although normally wired in 1mm2 for a res. and minimum 1.5mm2 for commercial installations, as long as total load on conductors is within specifications.

Cheers Craig

Being the now standardized metric cable sizes, that sounds pretty much the same as the U.K. 5 or 6A lighting circuits can be on 1 or 1.5 sq mm cables. Many smaller old properties have only one lighting circuit, although two is the norm now that people have more in the way of wall lights, porch lights, etc. Most of Continental Europe specifies 1.5 sq. mm as the minimum cable size though.

Do you know when NZ adopted metric size cables?

Can't help with that, Has been awhile i would imagine.