Soonthon LUPKITARO(Ph.D.) Sep 19, 2010:

In strict sense, secchi=[even in single phase circuits] connect to earth/ground [what I mainly concern in JP reply to this question]. See: http://denkinyumon.web.fc2.com/denkisetsubikiki/tyuuseitenns...
In broader sense, secchi=3-phase electric system earthing/grounding/neutralizing [in the English term of this question], see: http://ja.wikipedia.org/wiki/接地; also in my English version link below [In US English, earth=: ground=: neutral line]
:)

Yuki Okada Sep 19, 2010:

It seems that you are misunderstanding what "to" means here. This means that the voltage is nominally 277 VAC *in reference to* earth. It is of course not connected to earth.

Earth (or ground) is 接地, and neutral is 中性 or ニュートラル. I studied these properly because I am an electrical engineer myself.

Soonthon LUPKITARO(Ph.D.) Sep 19, 2010:

I do not want to repeat these special Kudoz features but the selected answer is based on non-technical knowledge. As many answerers say, the wire in question cannot connect with the ground/earth: large current will flow and the circuit fails. Actual situation in this question is concerned with ground/earth line: it is the neutral line in Japanese. See 277 VAC neutral line here: http://www.3phasepower.org/3phasewiring.htm AND advice of an electrical engineer for facts. Sorry for late discussion: I was so busy.