Surge arrestor
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Re: Surge arrestor
For parallel shunt types it creates a short circuit at the termianals when a prescribed voltage is reached sometimes refered to as "Clamping Voltage", then opening up after the voltage falls below a threshold voltage.
Series units just are low-pass filters (Pie Filter) that offer high impedance to fast rise-time pulses.
Stick with parallel shunt types. You can get these with filters as an option (Very expensive).
[ September 23, 2004, 04:25 PM: Message edited by: dereckbc ]
For parallel shunt types it creates a short circuit at the termianals when a prescribed voltage is reached sometimes refered to as "Clamping Voltage", then opening up after the voltage falls below a threshold voltage.
Series units just are low-pass filters (Pie Filter) that offer high impedance to fast rise-time pulses.
Stick with parallel shunt types. You can get these with filters as an option (Very expensive).
[ September 23, 2004, 04:25 PM: Message edited by: dereckbc ]
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Re: Surge arrestor
The simple ones that are typically used for home stereos, TVs, and computers are probably nothing more than a ?zener diode.? It is a device the blocks the flow of current. It is connected between hot and neutral, but does not normally allow current to flow through it. If the voltage gets to high (i.e., during a ?surge?), the device can no longer block current. It becomes a short circuit (i.e., a wire, no longer a diode), allowing a surge of current to flow back to the source. This will cause the surge current to avoid going through the equipment. The zener might survive the transient, or it may self-destruct. But the equipment downstream will not see as bad a transient, so it might survive.
The simple ones that are typically used for home stereos, TVs, and computers are probably nothing more than a ?zener diode.? It is a device the blocks the flow of current. It is connected between hot and neutral, but does not normally allow current to flow through it. If the voltage gets to high (i.e., during a ?surge?), the device can no longer block current. It becomes a short circuit (i.e., a wire, no longer a diode), allowing a surge of current to flow back to the source. This will cause the surge current to avoid going through the equipment. The zener might survive the transient, or it may self-destruct. But the equipment downstream will not see as bad a transient, so it might survive.
Re: Surge arrestor
SAD's are extremely fast, cannot handle as much power as MOV's, and expensive. Modern TVSS systems will use both MOV's and SAD's to get the advantages of both. The MOV's are used as a primary stage to handle the bulk of the power, while the SAD's are secondary stage for response time.
MOV's (metal oxide varistor). SAD's (Silicone Avalanche Diodes) are the expensive ones. Both have advantages over the other. MOV's will handle larger volumes of power (joules), inexpensive, degrade over time with repetitive use, and fairly fast.
SAD's are extremely fast, cannot handle as much power as MOV's, and expensive. Modern TVSS systems will use both MOV's and SAD's to get the advantages of both. The MOV's are used as a primary stage to handle the bulk of the power, while the SAD's are secondary stage for response time.
Re: Surge arrestor
Hello-
I'd like to pass along some real world information about surge arrestors/suppressors that you may find interesting.
Most of what you read about surge protective devices (SPDs) is unsubstantiated manufacturers hype.
One area that especially concerns me is a problem called "blind spot", click on this link and scroll down to page 6 to see the IEEE definition:
http://grouper.ieee.org/groups/spd/Reference_Desk/spd_definitions.doc
Many SPDs have a very large blind spot, well above the published clamping level of the device.
For example, we recently investigated a power quality problem for a customer. This client spent over $500.00 for a top of the line panel mounted SPD, but kept experiencing computer problems. Our PQ monitor documented transients in excess of 900v on the output side on the device. We then performed simultaneous monitoring on the input and output sides of the unit. Even though this product was rated for 330v, it was in fact providing no attenuation of transients on the mains.
I know that this is not what you were asking in your original post, but if you truly want to know "how a surge arrestor works" I would strongly recommend that you throw a PQ monitor on the unit to verify that the device really is protecting your equipment.
Good luck,
Mark
Hello-
I'd like to pass along some real world information about surge arrestors/suppressors that you may find interesting.
Most of what you read about surge protective devices (SPDs) is unsubstantiated manufacturers hype.
One area that especially concerns me is a problem called "blind spot", click on this link and scroll down to page 6 to see the IEEE definition:
http://grouper.ieee.org/groups/spd/Reference_Desk/spd_definitions.doc
Many SPDs have a very large blind spot, well above the published clamping level of the device.
For example, we recently investigated a power quality problem for a customer. This client spent over $500.00 for a top of the line panel mounted SPD, but kept experiencing computer problems. Our PQ monitor documented transients in excess of 900v on the output side on the device. We then performed simultaneous monitoring on the input and output sides of the unit. Even though this product was rated for 330v, it was in fact providing no attenuation of transients on the mains.
I know that this is not what you were asking in your original post, but if you truly want to know "how a surge arrestor works" I would strongly recommend that you throw a PQ monitor on the unit to verify that the device really is protecting your equipment.
Good luck,
Mark
Re: Surge arrestor
Mark, was it a "add-on" unit that required leads ran to a breaker? If so you have to add about 100 volts to the SVR for every inch of lead in wire.
I have found most add-on units are rendered useless by the installation. Highly reccomend integrated TVSS into the panels.
Mark, was it a "add-on" unit that required leads ran to a breaker? If so you have to add about 100 volts to the SVR for every inch of lead in wire.
I have found most add-on units are rendered useless by the installation. Highly reccomend integrated TVSS into the panels.
Re: Surge arrestor
Roger-
The problem with a blind spot being well above the published clamping level of a SPD is that the surge suppressor really isn't limiting, or clamping, the voltage to the lower level. That is, the published maximum let through voltage isn't 330v as claimed by the manufacturer, but some unknown higher value.
dereckbc-
You are correct, this is an add on unit. I am familiar with the lead length problem, but blind spot seems to be a different electrical phenomena. Over the years, I have observed this on power strip type surge suppressors as well as hard wired units. Power strip surge suppressors typically have short leads on the mov and short foil runs on the printed circuit board, yet these high voltage transients still pass.
(For those of you who might be thinking that the surge suppressors may have been at the end of its useful life- sorry. We had them checked out and they met the electrical specs of brand new units.)
I am not aware of a TVSS that can be integrated into a panel. I have seen movs wired directly into a panel, but this is not approved by the NEC or UL. If you know a mfg., could you please e-mail me?
Thanks!
Mark
Roger-
The problem with a blind spot being well above the published clamping level of a SPD is that the surge suppressor really isn't limiting, or clamping, the voltage to the lower level. That is, the published maximum let through voltage isn't 330v as claimed by the manufacturer, but some unknown higher value.
dereckbc-
You are correct, this is an add on unit. I am familiar with the lead length problem, but blind spot seems to be a different electrical phenomena. Over the years, I have observed this on power strip type surge suppressors as well as hard wired units. Power strip surge suppressors typically have short leads on the mov and short foil runs on the printed circuit board, yet these high voltage transients still pass.
(For those of you who might be thinking that the surge suppressors may have been at the end of its useful life- sorry. We had them checked out and they met the electrical specs of brand new units.)
I am not aware of a TVSS that can be integrated into a panel. I have seen movs wired directly into a panel, but this is not approved by the NEC or UL. If you know a mfg., could you please e-mail me?
Thanks!
Mark
Re: Surge arrestor
The closest thing I've seen are the ones built just like a circuit breaker and they plug directly onto the panelboard bus stabs. These don't seem to have the absorbtion rating of the larger units, but they have no leads except for the tail that goes to the neutral bus.
I put both a plug-on type and a knock out type in my 400A service hoping that the knock out one would relieve the plug-on one during a long duration surge.
The closest thing I've seen are the ones built just like a circuit breaker and they plug directly onto the panelboard bus stabs. These don't seem to have the absorbtion rating of the larger units, but they have no leads except for the tail that goes to the neutral bus.
I put both a plug-on type and a knock out type in my 400A service hoping that the knock out one would relieve the plug-on one during a long duration surge.
Re: Surge arrestor
PQtest, I do not do any type of residential design or test. Built-in TVSS is mostly the domain of commercial and industrial electrical. Many manufactures offer them.
One that I use for small regen and radio sites, and could be used for residential is here:
http://northern-tech.com/TVSS_Products/pdc_series.htm
I doubt a residential customer would spring for such a main panel, but it does give a good example of what I am talking about.
For my home I had the utility company install a TVSS at the meter. It is a collar the meter plugs into and comes with a $50K dollar gaurantee for large appliances. It does not cover electronics. For that they offer point-of-use devices, which are basically replacement receptacles with built-in SAD's connected from L-N
PQtest, I do not do any type of residential design or test. Built-in TVSS is mostly the domain of commercial and industrial electrical. Many manufactures offer them.
One that I use for small regen and radio sites, and could be used for residential is here:
http://northern-tech.com/TVSS_Products/pdc_series.htm
I doubt a residential customer would spring for such a main panel, but it does give a good example of what I am talking about.
For my home I had the utility company install a TVSS at the meter. It is a collar the meter plugs into and comes with a $50K dollar gaurantee for large appliances. It does not cover electronics. For that they offer point-of-use devices, which are basically replacement receptacles with built-in SAD's connected from L-N
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