- Location
- Massachusetts
Re: Electrode
Bennie where are you?
Keep it up Bennie.
Bennie where are you?
Keep it up Bennie.
Electrode
- Thread starter bennie
- Start date
- Status
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Electrode
Yep but I wouldn't want the number you have (666)
Yep but I wouldn't want the number you have (666)
- Location
- Massachusetts
Re: Electrode
Well I hope it changes with this post, if it stays 666 I will worry.
Well I hope it changes with this post, if it stays 666 I will worry.
dana1028
Senior Member
- Location
- San Francisco Bay area
Re: Electrode
I like using a Ufer, but here's a note about 'requiring' a Ufer to be used.
NEC - Formal Interpretation 78-4
Reference: Article 250.50
Question: Is it the intent of 250.50 that reinforcing steel, if used in a building footing, must be made available for grounding?
Answer: No
Issue Edition: 1978
Reference: 250-81
Issue Date: March 1980
Now having said that - does anyone know where we can get copies of Formal Interpretations to the NEC?
I know IAPMO makes available a manual of all current interpretations for the UPC, but I haven't seen any such 'manual/document' for the NEC.
[ July 10, 2003, 11:04 PM: Message edited by: dana1028 ]
I like using a Ufer, but here's a note about 'requiring' a Ufer to be used.
NEC - Formal Interpretation 78-4
Reference: Article 250.50
Question: Is it the intent of 250.50 that reinforcing steel, if used in a building footing, must be made available for grounding?
Answer: No
Issue Edition: 1978
Reference: 250-81
Issue Date: March 1980
Now having said that - does anyone know where we can get copies of Formal Interpretations to the NEC?
I know IAPMO makes available a manual of all current interpretations for the UPC, but I haven't seen any such 'manual/document' for the NEC.
[ July 10, 2003, 11:04 PM: Message edited by: dana1028 ]
roger willis
Member
- Location
- Texas
Re: Electrode
I also like using a Ufer ground. I think it is the best earth ground that you can have. I worked in Nevada for 12 years and that is the only way we could get a ground in all that sand. In fact all the areas that I worked in required it.
And good morning to all. I really enjoy this forum. I do more reading than posting.
Roger
I also like using a Ufer ground. I think it is the best earth ground that you can have. I worked in Nevada for 12 years and that is the only way we could get a ground in all that sand. In fact all the areas that I worked in required it.
And good morning to all. I really enjoy this forum. I do more reading than posting.
Roger
Re: Electrode
In 1975 I worked on a 138 KV line in the Sahara Desert in Libya. The desert sand was silica sand, not highly conductive.
The grounding was not important because there was no lightning activity in the desert.
I worked in the coldest, and hottest, places in the world. It seemed strange, that neither place had any lightning action.
In 1975 I worked on a 138 KV line in the Sahara Desert in Libya. The desert sand was silica sand, not highly conductive.
The grounding was not important because there was no lightning activity in the desert.
I worked in the coldest, and hottest, places in the world. It seemed strange, that neither place had any lightning action.
- Location
- Bremerton, Washington
Re: Electrode
Bennie where haven't you worked?
Quite a contrast from the south pole to the desert...
Bennie where haven't you worked?
Quite a contrast from the south pole to the desert...
pierre
Senior Member
- Location
- Westchester County, New York
Re: Electrode
Bennie
What about 'liquid' lightning?
Pierre
Bennie
What about 'liquid' lightning?
Pierre
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Electrode
Surges occure within a circuit be this a neutral-hot or neutral-ground or even hot-ground the most damageing is the neutral-hot but in all casses the surge protector or TVSS only has to protect the circuit that the surge is on at the time of the surge. this means if there is no ground then there will be no hot or neutral to ground surge as there will be no path for the surge to return to. there can not be any current (surge) without a full path from the source of the surge. so a TVSS will work on ungrounded systems. when there is a ground connected to a given appliance then there will be a return path for the surge. so in this case the TVSS has to have a ground to clamp down on a hot/neutral to ground surge.
Now for how surge suppressors work.
It depends on the type as some incorperate neon bulbs and others use a solid state device called a metal oxide variresistor or MOV for short. these were first produced by GE to protect the electronices of the space shuttle (no ground) and now there in everything what happens is as the voltage incresses above a threshold the resistance decresses and acts like a clamp to keep the voltage below a minimum. but if the surge last longer than a few nano seconds, like a lost neutral it will destroy the MOV and can cause a fire in doing so
Surges occure within a circuit be this a neutral-hot or neutral-ground or even hot-ground the most damageing is the neutral-hot but in all casses the surge protector or TVSS only has to protect the circuit that the surge is on at the time of the surge. this means if there is no ground then there will be no hot or neutral to ground surge as there will be no path for the surge to return to. there can not be any current (surge) without a full path from the source of the surge. so a TVSS will work on ungrounded systems. when there is a ground connected to a given appliance then there will be a return path for the surge. so in this case the TVSS has to have a ground to clamp down on a hot/neutral to ground surge.
Now for how surge suppressors work.
It depends on the type as some incorperate neon bulbs and others use a solid state device called a metal oxide variresistor or MOV for short. these were first produced by GE to protect the electronices of the space shuttle (no ground) and now there in everything what happens is as the voltage incresses above a threshold the resistance decresses and acts like a clamp to keep the voltage below a minimum. but if the surge last longer than a few nano seconds, like a lost neutral it will destroy the MOV and can cause a fire in doing so
Re: Electrode
Do not know if this is the original subject or not but surges occur in either differential mode, or common mode. Which mode depends on where the surge occurs in relation to where you are.
For instance, if lightning were to strike the utility distribution line ahead of your service transformer you would recieve a differential mode surge. This is because of your transformer. Even though the surge was between ground and phase, once going through the transformer it changes the surge from phase to neutral, and phase to phase. This is why it is important to have a class "C" device installed at the service entrance with "all modes" (phase-to-phase, phase-to-neutral, and phase-to-ground)except neutral-to-ground. N-G isn't nessecary because of the N-G bond at the service entrance.
To add to what Wayne stated there are more than just MOV type of devices. The better designed units use hybrid devices. They come with MOV's, SAD's, and gas tubes. Each have advantages over the other. SAD's (silicon avalance diodes) are extremely fast, less than 1 pico-second, but cannot handle large amounts of energy. MOV's are fast, less than 1 micro-second, and can handle fairly large amounts of energy, but are not as fast as SAD's. Gas tubes are slow, but can handle extremely large amounts of energy. When all three are combined you get the best of all, untill you install them with leads longer than 6 inches, then they are useless.
The best units out today are built into the service equipment using a "Kelvin Clamp method with no lead lengths, and use some series techniques for added protection.
Do not know if this is the original subject or not but surges occur in either differential mode, or common mode. Which mode depends on where the surge occurs in relation to where you are.
For instance, if lightning were to strike the utility distribution line ahead of your service transformer you would recieve a differential mode surge. This is because of your transformer. Even though the surge was between ground and phase, once going through the transformer it changes the surge from phase to neutral, and phase to phase. This is why it is important to have a class "C" device installed at the service entrance with "all modes" (phase-to-phase, phase-to-neutral, and phase-to-ground)except neutral-to-ground. N-G isn't nessecary because of the N-G bond at the service entrance.
To add to what Wayne stated there are more than just MOV type of devices. The better designed units use hybrid devices. They come with MOV's, SAD's, and gas tubes. Each have advantages over the other. SAD's (silicon avalance diodes) are extremely fast, less than 1 pico-second, but cannot handle large amounts of energy. MOV's are fast, less than 1 micro-second, and can handle fairly large amounts of energy, but are not as fast as SAD's. Gas tubes are slow, but can handle extremely large amounts of energy. When all three are combined you get the best of all, untill you install them with leads longer than 6 inches, then they are useless.
The best units out today are built into the service equipment using a "Kelvin Clamp method with no lead lengths, and use some series techniques for added protection.
brian john
Senior Member
- Location
- Leesburg, VA
Re: Electrode
Dereck:
What I always like to see with a TVSS installation is the manual explaining the need for short lead lenght and minimal bends, open the door of the TVSS and look at some of the hair pin turns the manufacture utilizes to accomadate the typical 10 lbs of stuff in a 5 lb box. I've question a particular manufacture sales rep regarding this issue and he said
" In the testing process we account for those conductor bends."
Well yes but wouldn't the TVSS be more efficent without these bends.
NO ANSWER
Dereck:
What I always like to see with a TVSS installation is the manual explaining the need for short lead lenght and minimal bends, open the door of the TVSS and look at some of the hair pin turns the manufacture utilizes to accomadate the typical 10 lbs of stuff in a 5 lb box. I've question a particular manufacture sales rep regarding this issue and he said
" In the testing process we account for those conductor bends."
Well yes but wouldn't the TVSS be more efficent without these bends.
NO ANSWER
pierre
Senior Member
- Location
- Westchester County, New York
Re: Electrode
When the Sads, Gas tubes and the Movs are 'doing their thing', do they dissipate to ground or not? The current has to go somewhere, if not to ground, where? My understanding is these devices shunt current to ground in their various ways. Some sources of these currents are not the 'System Source' (lightning, utility switching), so they are not going to go 'back to the system', right?
Pierre
When the Sads, Gas tubes and the Movs are 'doing their thing', do they dissipate to ground or not? The current has to go somewhere, if not to ground, where? My understanding is these devices shunt current to ground in their various ways. Some sources of these currents are not the 'System Source' (lightning, utility switching), so they are not going to go 'back to the system', right?
Pierre
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Electrode
Pierre
Transeit's are shunted always back to the source not just to ground.
this would be like shorting the positive terminal of one car battery to the negitive of another batery with out no other connection there would be no compliet circuit shunting the shurge just to ground would not do anything to a neutral/hot surge as to shortout a surge you have to lower the resistance along the path of the current.
Pierre
Transeit's are shunted always back to the source not just to ground.
this would be like shorting the positive terminal of one car battery to the negitive of another batery with out no other connection there would be no compliet circuit shunting the shurge just to ground would not do anything to a neutral/hot surge as to shortout a surge you have to lower the resistance along the path of the current.
Re: Electrode
Remember that there is only two types of transient overvoltages on the primary line. These are from capacitor switching and lightning.
There is some end user created overvoltages.
A power line lightning impulse is transmitted to the low side of the transformer, through capacitance coupling due to current flowing in one direction. This current is attempting to go to it's home in the dirt.(good song title)
An impulse, from capacitor switching, can only flow in the circuit, not to the earth.
Transients are very short duration. Voltage sags, power surges from load shedding(voltage swells) are of a longer duration, and not considered transients.
Remember that there is only two types of transient overvoltages on the primary line. These are from capacitor switching and lightning.
There is some end user created overvoltages.
A power line lightning impulse is transmitted to the low side of the transformer, through capacitance coupling due to current flowing in one direction. This current is attempting to go to it's home in the dirt.(good song title)
An impulse, from capacitor switching, can only flow in the circuit, not to the earth.
Transients are very short duration. Voltage sags, power surges from load shedding(voltage swells) are of a longer duration, and not considered transients.
Re: Electrode
Pierre, it depends on whether it is differential mode or common mode impulse. Differential mode impulses are from phase-to-phase and phase-to-neutral, no ground involved.
Common mode impulses are phase-to-ground, and sometimes neutral-to-ground if the N-G bond is upstream a considerable distance
Pierre, it depends on whether it is differential mode or common mode impulse. Differential mode impulses are from phase-to-phase and phase-to-neutral, no ground involved.
Common mode impulses are phase-to-ground, and sometimes neutral-to-ground if the N-G bond is upstream a considerable distance
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