Grounding 1908

[bennie]

I purchased an electrical engineering textbook today with a copyright date of 1908. This textbook is published by the International Textbook Company.

This is the first book where I have found any reference to grounding.

The center tap of an economy coil (auto-transformer) is brought out from the winding and connected to earth(ground). This is to reduce the pressure of the line conductors to half, in relation to ground.

The 25 ohms has not appeared as of 1908.

Lightning protection is described as spark gaps.

 

[svaurez]

Re: Grounding 1908

This might help:

Hawkins Electrical Guide 1915 Volume 7
(page 1,708)

5.From time to time the resistance of these ground connections should be measured to determine their condition.The resistance of a single pipe ground in good condition has an average value of about 15 ohms.A simple and satisfactory method of keeping account of the condition of the earth connections is to divide the grounding pipes into two groups and connect each group to the 110 volt lighting circuit with an ammeter in series.

[ June 18, 2003, 12:07 AM: Message edited by: svaurez ]

 

[bennie]

Re: Grounding 1908

Now we are making progress. Thanks a lot.
Something happened between 1908 and 1915.
The textbook, I have, has a whole chapter on how to detect and clear a grounded conductor. Other than the auto-transformer there is nothing intentionally grounded.

The test method, described in your book, suggests the resistance is the entire resistance of the dirt path to the transformer.

Now I need to find out what transpired in the seven years.

 

[charlie]

Re: Grounding 1908

I know this doesn't fit the discussion; however, when I used to work on K & T and was working with a fixture or receptacle, I used a neon pocket tester to find the ungrounded conductor. I would make sure I was not grounded, hold onto one end lead of the tester and probe the wires individually with the power on (the hot ones would cause the light to faintly glow).

 

[bennie]

Re: Grounding 1908

Charlie: It does fit this discussion. In 1908, three wire Edison systems were ungrounded. All three wires were fused.
I now know why a neutral was fused. Apparently when the system was grounded later on, the neutral remained fused from the past installation.

Those 7 years are important in my research. Anyone having publications from that period please let me know.

 

[kqresq]

Re: Grounding 1908

Bennie,
The NEC Digest referenced in earlier posts is the Summer 2003 edition. The article is entitled "Solid Ground" and is written by John M. Caloggero. According to the article, the American Institute of Electrical Engineers and the Board of Fire Underwriters isssued a report in 1909 agreeing "the rules for grounding be made mandatory for conductors operating at 150 volts or less, and be made optional for conductors operating up to 250 volts between conductors and ground".

I would be happy to send you a copy of this two page article if you think it would help.
You can e-mail me at kqresq@yahoo.com for mailing instructions if you wish.
Karl

 

[bennie]

Re: Grounding 1908

Karl: Thanks very much, I sent my address by email.

Also thanks for confirming my time line. The chronology of events is important, for me to find the information I am seeking.

Who knows I may become a lektrick engine ear yet

 

[bennie]

Re: Grounding 1908

I located an engineering standard dated 1907.

This document describes the Thompson Protective Device for ungrounded transformers. This device applied a dead short across the secondary winding in the event of a primary to secondary insulation breakdown. This system was not reliable and was discontinued.

Permanent grounding of the secondary was the most effective method for overcoming the danger of the winding to winding fault.

The primary purpose of grounding the secondary, is for the reason of preventing the danger of electrocution when high tension conductors make contact with low tension.

Transient surges and lightning induced current is not mentioned. MOV's and arrestors are for this purpose.

I think there is some technical reasons for grounding, that have been corrupted through time.

 

[bennie]

Re: Grounding 1908

I also located documentation to substantiate my interpretation and definition of the Separately derived system.

On large three wire systems, where an extended network is supplied through underground cables or Edison underground tubes, the neutral is generally grounded, as the advantages of grounding outweigh the disadvantages; for small systems or for "isolated plants" it is better on the whole to keep the neutral insulated from ground.

The isolated plants later became known as a power source for a separately derived premises system.

I don't want to get bogged down on this subject now. I just couldn't resist

[ June 18, 2003, 03:47 PM: Message edited by: bennie ]

 

[bphgravity]

Re: Grounding 1908

Hello Bennie!

I also have a copy of this book and was planning on posting your last comment. My version is also 1908 and called "I.C.S. Reference Library."

I have several vintage (pre 1930's) electrical books that I will search for some grounding history.

Later this summer, I will be visting Tom Henry at his office in Orlando. He has one of the largest and complete collections of vintage and historical books on electricity and electrical wiring.

I will look through these as well for some history on grounding! I will post what I find!

 

[bennie]

Re: Grounding 1908

Bryan: Thanks for corroborating my statement.
You have the same book I am quoting. I bought it for ten dollars.

I can already see areas of possible mis-understanding in the intent, and purpose, of plugging a wire into the earth.

We are at 1909 now. I think more will be apparent as this subject progresses.

To make my point about individuals fabricating an explanation for a specific technical procedure. Did anyone hear the reason that was going around for raising the six foot, six inches to a breaker handle to six foot, seven inches, because it was determined that humans have grown one inch on the average.

I heard this at a code class, by a certified instructor. I said out loud "bovine excrement", Only I used the more popular name, and left the room.

[ June 18, 2003, 10:42 PM: Message edited by: bennie ]

 

[svaurez]

Re: Grounding 1908

More pieces to the puzzle

Standard American Electrician (1908)
In connecting a ground wire to a piping system,the wire should be sweated into a lug attached to an approved clamp,and the clamp firmly bolted to the water pipe after all rust and scale have been removed;or be soldered into a brass plug and the plug forcibly screwed into a pipe-fitting,or,where the pipes are cast iron,into a hole tapped into the pipe itself.For large stations,where connecting to underground pipes with bell and spigot joints,it is well to connect to several lengths,as the pipe joints may be of rather high resistance.
Where ground plates are used,a No.16 Stubbs' gage copper plate,about three by six feet in size,with about two feet of crushed coke or charcoal,about pea size,both under and over it,would make a ground of sufficient capacity for a moderate-sized station,and would probably answer for the ordinary substation or bank of transformers.For a large central station,a plate with considerably more area might be necessary,depending upon the other underground connections available.The ground wire should be riveted to the plate in a number of places,and soldered for its whole length.Perhaps even better than a copper plate is a cast iron plate with projecting forks,the idea of the fork being to distribute the connection to the ground over a fairly broad area,and to give a large surface contact.The ground wire can probably be best connected to such a cast-iron plate by soldering it into brass plugs screwed into holes tapped in the plate.In all cases,the joint between the plate and the ground wire should be thoroughly protected against corrosion by painting it with waterproof paint or some equivalent.

 

[bennie]

Re: Grounding 1908

svaurez: Very good article. Do you find any reference to the grounding being for lightning discharge?

 

[svaurez]

Re: Grounding 1908

No mention of lightning.There are a couple of paragraphs in another chapter on lightning arrestors.

 

[svaurez]

Re: Grounding 1908

Hawkins Electrical Guide #6 (1914)


Transformer Operation with Grounded Secondary.

The operation of a transformer with a grounded secondary has been approved by the American Institute of Electrical Engineers,and by the National Board of Fire Underwriters.
This method of operation effectually prevents a high voltage occuring upon the low tension wires in case of a breakdown or other electrical connections occuring between the primary and secondary windings.
In case of a breakdown without the secondary grounded,any one touching a part of the low tension system,such as a lamp socket,might receive the full high pressure voltage.With the low tension grounded,the fuse in the high tension circuit will blow and the fault be discovered upon replacing it.

 

[bennie]

Re: Grounding 1908

Thanks, that's what I thought.

You have answered another issue that I did not have a clue what was meant. 250.70 (1) Pipe fitting or plug used for attaching ground electrode conductor.

That section has been in the book for almost 100 years and I did not know what a pipe plug for the ground conductor was or is.

 

[bennie]

Re: Grounding 1908

To recap...I have learned how the fused neutral happened, and what is meant by pipe plugs in
250-70 (1).

That is two things, I have learned, that bothered me. Both are obsolete so big deal.

The research time is now at 1914. Secondaries are grounded (earthed). This is apparently the origin of the multi-ground distribution system.

Containing a fault in the transformer windings can be done without going to the earth.

Preventing high voltage from appearing on the service in the event of a cross with a high tension wire would possibly be reduced by the shunt effect to ground at the service. There is questions about this actually working.

 

[Ed MacLaren]

Re: Grounding 1908

I do not know when system grounding first appeared, but I am convinced that the following scenario is the reason why it was started.

On the early ungrounded systems, a person in contact with the earth would not get a shock by touching any one conductor. The only voltage to ground would be due to distributed capacitance, which would be very low, with few metal raceways in use.
The early electrical customer would get used to that situation, and become careless about touching one wire. (Sketch A)

Sounds great, but how do we ensure that a system remains ungrounded? We can’t!

Any insulation breakdown that results in a conductor coming in contact with the earth, or any object connected to the earth, will have the effect of creating a grounded system, and now a person touching the other conductor receives an unexpected shock. (Sketch B)


I don’t think it would have taken very long for the early engineers to realize that, because they couldn’t prevent the system from eventually becoming grounded, they might as well ground one of the conductors in the first place, and by grounding the neutral conductor, the maximum voltage to ground would be half the transformer voltage (in single-phase systems), or the phase voltage (in wye connected three phase systems).

Ed

 

[tom baker]

Re: Grounding 1908

the most recent issue of the NEC Digest has a review of why grounding electrical systems started. One of the reasons the mid point of a transformer is grounded is if the insulation fails it will keep the secondary voltage from reaching the primary level. I can imagine the early electrical systems had a lot of transformer failures.
It was a ground or not ground, and it took many years to get everyone to agree on grounding.

 

[bennie]

Re: Grounding 1908

Tom: My 1908 book states the same thing. Transformer insulation was and still is the weak link in a transformer. Even when oil filled.

The domestic distribution system uses the delta wye principal on all system transformers. All of the star points are connected to a common neutral. This prevents winding to winding faults from appearing on the user equipment. This connection also will carry ground fault current back to the source. This neutral/ground is a circuit conductor on the NESC side but it is not on the NEC side. Soares Grounding Book states that load current does not flow in the equipment ground, so it is not a circuit conductor. That is why it is green, with envy