I am writing an installation guide for Surge Arresters and TVSSs. I am getting conflicting info on how the ground is to be connected. The first is that, the SA or TVSS can be connected directly to a ground rod (Separate from the Main Dist Panel (MDP)). The second is that the Ground needs to be connected directly to the MDP through a raceway (with all the other conductors) and rely on the MDP to supply the ground return for the SA and TVSS. FYI, the box in which the protection is enclosed in hard plastic. Also, I've looked at Articles 280 and 285 of the NEC and no clear answer is present. Thanks in advance for your help.
Grounding of Surge Arresters and TVSSs
- Thread starter rgonzo
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Re: Grounding of Surge Arresters and TVSSs
I have nothing constructive to offer other than to suggest that you raise your seatback, put on your seatbelt, and put your tray table in an upright and locked position. Then hold on tight! I will watch this thread with great interest!
[ September 12, 2003, 06:08 PM: Message edited by: awwt ]
I have nothing constructive to offer other than to suggest that you raise your seatback, put on your seatbelt, and put your tray table in an upright and locked position. Then hold on tight! I will watch this thread with great interest!
[ September 12, 2003, 06:08 PM: Message edited by: awwt ]
Re: Grounding of Surge Arresters and TVSSs
Rgonzo
If you are installing a TVSS you should be aware that there are different classifications that you need to know. Class C,100 ka and higher devices, are installed at the main disconnect and are connected to the main bus thru a breaker specified by the mfg. The connection to ground is made in the main disconnect to the neutral ground connection on the neutral ground bus. The length of the cable should be as short as possible and this point is extremely important. If you are installing TVSS in sub panels they may be classified as Class B. The connection is similar to the one in the main disconnect.
Rgonzo
If you are installing a TVSS you should be aware that there are different classifications that you need to know. Class C,100 ka and higher devices, are installed at the main disconnect and are connected to the main bus thru a breaker specified by the mfg. The connection to ground is made in the main disconnect to the neutral ground connection on the neutral ground bus. The length of the cable should be as short as possible and this point is extremely important. If you are installing TVSS in sub panels they may be classified as Class B. The connection is similar to the one in the main disconnect.
Re: Grounding of Surge Arresters and TVSSs
RGONZO, first let me say you are trying to re-invent the wheel. Get yourself a copy of ANSI/IEEE C62.41, UL-1449, and NEMA LS-1. Code is not going to help you write instructions.
Short on time at the moment, more later, but ground does not have anything to do with a surge event at the entrance, and very little help downstream. By code you cannot drive a rod and have it isolated from the rest of the electrode system. One more thing before I leave you guessing, if any lead is longer than 6 inches (including ground), the TVSS device is rendered ineffective. For now get a copy of C62.41.
Here is another shocker, a TVSS is the least effective device for transient events.
RGONZO, first let me say you are trying to re-invent the wheel. Get yourself a copy of ANSI/IEEE C62.41, UL-1449, and NEMA LS-1. Code is not going to help you write instructions.
Short on time at the moment, more later, but ground does not have anything to do with a surge event at the entrance, and very little help downstream. By code you cannot drive a rod and have it isolated from the rest of the electrode system. One more thing before I leave you guessing, if any lead is longer than 6 inches (including ground), the TVSS device is rendered ineffective. For now get a copy of C62.41.
Here is another shocker, a TVSS is the least effective device for transient events.
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Re: Grounding of Surge Arresters and TVSSs
Not to stray off-topic but how do you feel a Delta TVSS differ from the MOV ones?
DELTA silicon oxide varistor
I wrote to Delta but never heard back.
Why Delta?
Delta home page
Are these things listed? They claim to take an unlimited strike.
../Wayne C.
[ September 12, 2003, 09:14 PM: Message edited by: awwt ]
dereckbc:
Not to stray off-topic but how do you feel a Delta TVSS differ from the MOV ones?
DELTA silicon oxide varistor
I wrote to Delta but never heard back.
Why Delta?
Delta home page
Are these things listed? They claim to take an unlimited strike.
../Wayne C.
[ September 12, 2003, 09:14 PM: Message edited by: awwt ]
Re: Grounding of Surge Arresters and TVSSs
[ September 12, 2003, 10:49 PM: Message edited by: dereckbc ]
Cannot compete with MOV's or SAD's IMHO. Did not like the specs for the Delta units. They used the term Joule rather than KA per mode. Here are a couple of Spec sheets and what to look for in a good TVSS. Be aware these two devices are in the 4-digit $$$$ range. http://www.atlanticscientific.com/support/pdfs/zonemasterplus.pdf http://www.geindustrial.com/products/specs/FES-133.doc
[ September 12, 2003, 10:49 PM: Message edited by: dereckbc ]
Re: Grounding of Surge Arresters and TVSSs
Since all you asked about was the ground connections I will limit myself just to that subject (hard to do). Ground has no purpose in a service entrance TVSS device other than that of any other EGC. It is just there to provide a fault path in case of accidental faults from phase to ground?.. So run your EGC with line and neutral conductors as closely grouped as possible. Use cable ties to keep grouped tightly.
There are two very good reasons why I say this.
1. According to ANSI/IEEE C62.45, 95% of all lightning strikes occur ahead of the transformer primary or input side. This means the surge on the output side of the transformer will be in the differential mode meaning between L-N on grounded systems, and L-L on un-grounded systems. This is as opposed to common mode from L-G. Any transformer provides very good Common Mode Rejection or common mode TVSS, but no differential mode protection.
2. If you do not believe #1 then consider this. At the service entrance what is the grounded conductor connected too? Hint, I will not spell it out but some of the initials are GEC or MBJ. With that in mind comes the next point.
At the service entrance there is no need for ?all mode? protector modules. All modes protectors are L-L, L-G, L-N, and N-G. All that is needed is L-N. All other modes are redundant and add extra cost. Best buy and maximum protection is L-N models with the largest modules you can afford. You can also apply this same principle to any class B devices downstream from service entrance at the output of step-down or isolation transformers for the reasons already given.
Down stream devices at sub-panels can benefit from all mode devices, but you run the ground with line and neutral conductors as you normally would. If you insist on adding an external ground to the electrode system do it from the sub-panel ground bus rather than the TVSS all mode device.
[ September 12, 2003, 11:32 PM: Message edited by: dereckbc ]
Since all you asked about was the ground connections I will limit myself just to that subject (hard to do). Ground has no purpose in a service entrance TVSS device other than that of any other EGC. It is just there to provide a fault path in case of accidental faults from phase to ground?.. So run your EGC with line and neutral conductors as closely grouped as possible. Use cable ties to keep grouped tightly.
There are two very good reasons why I say this.
1. According to ANSI/IEEE C62.45, 95% of all lightning strikes occur ahead of the transformer primary or input side. This means the surge on the output side of the transformer will be in the differential mode meaning between L-N on grounded systems, and L-L on un-grounded systems. This is as opposed to common mode from L-G. Any transformer provides very good Common Mode Rejection or common mode TVSS, but no differential mode protection.
2. If you do not believe #1 then consider this. At the service entrance what is the grounded conductor connected too? Hint, I will not spell it out but some of the initials are GEC or MBJ. With that in mind comes the next point.
At the service entrance there is no need for ?all mode? protector modules. All modes protectors are L-L, L-G, L-N, and N-G. All that is needed is L-N. All other modes are redundant and add extra cost. Best buy and maximum protection is L-N models with the largest modules you can afford. You can also apply this same principle to any class B devices downstream from service entrance at the output of step-down or isolation transformers for the reasons already given.
Down stream devices at sub-panels can benefit from all mode devices, but you run the ground with line and neutral conductors as you normally would. If you insist on adding an external ground to the electrode system do it from the sub-panel ground bus rather than the TVSS all mode device.
[ September 12, 2003, 11:32 PM: Message edited by: dereckbc ]
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