Yes and no. Yes as grounds and neutrals leave the sub panel, there is a lack of bonding (separation/isolation). But if you travel upstream to the main panel, the 2 are bonded, typically on the bar. At this point both are typically earthed to whatever earthing system used.
Yes, very recent, when considering the age of many houses. Separation of ground and neutral was first specified in the 1999 edition of the NEC. More changes and specificity were added in 2008.
That is part of it. The other is ensuring the hots are only 120V relative to ground, and that you're neutral isn't ever floating more than a conductor's drop above your plumbing. People used to get shocked just touching their kitchen faucet and an appliance, at the same time.
The reason is to avoid a parallel current path, and ensure primary current never flows on the ground wire. Simple Kirchoff's theory, if you bond two conductors at both ends, they're effectively one conductor, and current will divide onto the two according to their proportional conductance.
Thanks for the clarification.
My friend just bought an old glass factory in Philadelphia outside of center city. PECO came to hook up the power and gave him a Scott transformer that supplied 1200V 2-phase to his building. Inside the building were huge old 2-phase step down transformers. The transformers had boiler drains to drain the dielectric oil that were right over floor drains that led to the city storm drains and into the river.They've been phasing it out (pun?) for decades, so probably either used or custom.
I just checked, and while I was right on Philadelphia (of course), Chicago was not the second city still using it. That honor goes to Hartford CT.
"Active two-phase distribution systems remain in Center City Philadelphia, where many commercial buildings are permanently wired for two-phase,[2] and in Hartford, Connecticut.[3]"
Its prevalence is nothing more than an example of historic inertia. 2-phase was popular in the very early 1900's, and Philadelphia happened to be one of the first large cities being wired at that time. By the time other major cities came on line to the same extent, the advantages of 3-phase were already known and deployed, so they got the newer/better tech. That said, even most of Philly is 3-phase, today.
Two-phase electric power - Wikipedia
en.wikipedia.org
Probably not uncommon, in any major city, at the time. Philly was built at the confluence of the Schuylkill and Delaware rivers, just as most confluences are populated by old cities, water being the primary forms of transportation and power at one time.
The Earth is the ground !! If you touch the ground wire or buss and you are better grounded - you will complete the circuit and get electrocuted.
It's possible the voltage you were feeling was induced via the antenna sticking up in the air, and not from the receiver on the television itself. TV receivers, unless miswired or malfunctioning, should not output any high voltage. But a metal stick standing 50 feet in the air probably could pick up a charge sufficient to make you mighty uncomfortable, if left ungrounded.
