[Antennas] Ground rod questions (Ground currents)

Wed Jul 1 19:21:11 EDT 2009

Chris,
Perhaps your statement is true in some states, but not in the central part
of California where I live. The neutral is NEVER carried back to the
substation; it begins at the local distribution transformer center tap,
usually labeled as the "X0" terminal. The substations transform either
70,000 or 115,000 volts (the transmission voltage) down to 12,000 volts (the
distribution voltage) which is connected to local transformers in the 50-150
kVA range for connection to residential service panels at (usually) 8 to 12
homes. The transmission and distribution lines are just three phase
conductors, without a neutral. The X0 terminals at each local transformer
are bonded to the transformer tank and to a ground rod at the transformer.
Each home is served by two "hot" conductors, often called the X1 and X2
wires, and a neutral conductor connected to the X0 lug. At each service,
the neutral conductor is bonded to the meter box, the neutral bus bar, the
ground bus bar, the interior metallic water pipe, and to a grounding
electrode. For many years, the grounding electrode was one or two driven
rods, but the standard is now a Ufer ground. The Ufer ground consists of a
bare #4 AWG copper wire that is embedded in the bottom two inches of the
concrete foundation footing. It is very effective, since the concrete
foundation is in contact with soil over a large area, and the embedded Ufer
ground wire is at least 20 feet long.
It should be noted that "110 volts" and "220 volts" have not existed in this
Nation for more than half a century, even though the terms are frequently
used by non-technical folk. The national standard nominal voltage that
utilities strive to provide is 120 +/- 5% VAC from line-to-neutral, and
either 208 or 240 VAC +/- 5% line-to-line. I mention this because many
apartment houses, condos, mobile home parks, and cluster homes are served
with three-phase power, and each residential unit is fed 120/208 VAC
single-phase power derived from two phases of the distribution transformer.
This fact may be significant for the purchaser of an electric range, clothes
dryer, or water heater. The standard large electric appliances found in
stores are designed to operate on 240 VAC, and will produce 25% less heat if
operated on 208 VAC. Most appliance manufacturers can provide a unit made
for 208 VAC operation as a special-order option- at additional cost, of
course! If a high-power linear amplifier is designed to run on 240 VAC, it
may not be capable of full power output when run on 208 VAC. One can
restore the linear amp to full power by connecting a 32-volt "boost"
transformer to bring the voltage up to 240 VAC. (You see, I finally got
back to Ham radio!)
73, Eric Lemmon WB6FLY
(and a Certified Electrical Inspector) 
-----Original Message-----
From: antennas-bounces at mailman.qth.net
[mailto:antennas-bounces at mailman.qth.net] On Behalf Of Chris Boone
Sent: Tuesday, June 30, 2009 9:16 PM
To: 'rbethman'; 'Antennas'
Cc: 'C. Whitaker'
Subject: Re: [Antennas] Ground rod questions (Ground currents)
I disagree in part...but agree with most of your post, Bob..
The Neutral or "Static" IS carried back to the substation and all the way
back to the generation station..it is PART of a single or three phase
circuit and the static ground off the 3 phase is bounded to the neutral of
the center tapped xfmr on the pole...ALL of it is tied together for
reference of the 1 phase 120V/220V....when you have 110 on one side and less
than 110 on the other (like 7V?) but showing 220 across the two hot wires
from the xfmr, you have an OPEN Neutral that can KILL and cause fires....I
had to argue with a contract crew for three hours after Umberto came through
SETX and did damage at a friend's house...funny, the company crew leader,
when he showed up, said "OH HELL, it's Boone...HE KNOWS what's wrong and YOU
guys (meaning the contract crew) have been arguing with HIM???" The crew
leader knew me for 20 yrs in the company...and I pulled my hard hat out to
make the point...took the idiot contract crew 3 hours what a single COMPANY
man would have fixed in 30 minutes!!! :)
YES, the SAFETY ground in equipment is for short circuit protection....you
can still get shocked if the neutral from the xfmr to the house opens and
the ground is still there...had that happen not too long ago (see above)...
Chris
WB5ITT
Gulf States Utilities (Now onwed by Entergy) w/Riverbend Nuclear Plant, last
1 built in the US in the 80s...so far ;) 1984-1996
Chief Engineer, KDMX/KEGL FMs and 1190AM Dallas-Fort Worth (and we used a
lot of 3 phase and single phase!)
Now with CenterPoint Energy (former Houston Lighting and Power),
2004-present
-----Original Message-----
From: antennas-bounces at mailman.qth.net
[mailto:antennas-bounces at mailman.qth.net] On Behalf Of rbethman
Sent: Tuesday, June 30, 2009 2:12 PM
To: Antennas
Cc: C. Whitaker
Subject: Re: [Antennas] Ground rod questions (Ground currents)
The three phase "Y" does NOT derive neutral from the central 
connection! That central connection IS ground.
I do NOT know where you have been involved in power generation and/or 
distribution. I sure hope you are NOT so now. The center of the "Y" 
has ALWAYS been the ground beginning at the generator. This is the way 
it IS.
Neutral wires are derived from center tapping single phases on a 
stepdown transformer otherwise known as a distribution transformer, 
located either on a power pole OR a pad mounted one in an underground 
system.
Neutrals are NOT carried as the main power distribution system going 
back to substations or generators.
ALL "Y" systems reference their phase voltage to ground, which IS the 
center of the "Y". The ground is for safety in a short circuit, NOT to 
be a safety in the event the neutral should open! That is PATENTLY false!
Suggest you consult the NEC and other applicable documents. Also 
include electrical engineering books.
I may be retired military, BUT - I am ALSO a Board certified Nuclear 
Power Plant Operator and Technician.
Bob - N0DGN
C. Whitaker wrote:
> de WB2CPN
> Perhaps we need to clarify and identify the 
> relationship between the "Neutral" wire which
> comes from the center of the 3-phase "Y" or
> the center of the single-phase transformer which 
> feeds most if not all houses and other small users, 
> and the "Ground" wire that connects to that Neutral
> wire either at the pole or at the service entrance.
> The neutral wire is to carry the current that results
> from uneven currents in the 2 hot wires, while the
> "Ground" wire is to prevent someone from being
> hurt if the neutral wire open up somewhere and 
> makes what's left of it in the house hot. Nothing 
> has any interest in noise, radio or otherwise.
> Look at this: A housetrailer neutral and ground
> wires were bonded inside the trailer. Only the
> neutral wire came to the meter, and then to the
> pole. When that neutral wire opened, (bad splice),
> everything on one side of the 220/110 feed was
> placed in series with everyting on the other side
> of the feed. The refer on one side, when it came
> on, blew heck out of the clock motor which was
> on the other side. Then, the refer had no power.
> TRIVIA
> Clete in South Central PA
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-- 
Bob - NØDGN
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