In article , Owain writes
i.e. they want to see the blown-up kit the surge protector was supposed to be protecting.
Also, MOVs wear out - they become less and less effective with each surge they shunt to earth and eventually stop working altogether. Some of the better surge protectors have a warning lamp to tell you when this has happened.
nope
Mains connected appliances are capable of handling greater 'surges' than th= e surge protectors. They are simply pointless. Anyone with any electronics = skills can look at typical power supply front ends and see a far more effec= tive means of dealing with voltage peaks than a variable resistor across th= e mains.
Exactly how are they useful? What voltage do you believe appliances are una= ble to survive, but that MOVs eliminate? What is the source of these surges= in your opinion?
Hint: the impedance of the mains incomer is a tiny fraction of the impedanc= e of a conducting MOV
NT
That is NOT a given. its a MAY.
See wikis comments ================================================================
There are several issues to be noted regarding behavior of transient voltage surge suppressors (TVSS) incorporating MOVs under over-voltage conditions. Depending on the level of conducted current, dissipated heat
*may* be insufficient to cause failure, but *may* degrade the MOV device and reduce its life expectancy. If excessive current is conducted by a MOV, it may fail catastrophically, keeping the load connected, but now without any surge protection. A user may have no indication when the surge suppressor has failed. Under the right conditions of over-voltage and line impedance, it may be possible to cause the MOV to burst into flames[3], the root cause of many fires[4] and the main reason for NFPA?s concern resulting in UL1449 in 1986 and subsequent revisions in 1998 and 2009. Properly designed TVSS devices must not fail catastrophically, resulting in the opening of a thermal fuse or something equivalent that only disconnects MOV devices. ============================================================And MOVS are not applied between phase and earth. That would result in instant RCD operation. They are applied ACROSS phases to limit spikes on the live with respect to the neutral from e.g. disconnection of inductive loads.
That is in fact the only situation in which they do anything useful at all.
Almost nothing is permitted to go between live and earth or neutral and earth. Typically only RF suppression caps and those in themselves represent a PITA with RCDS.
mains surges were never a problem really with transformer coupled LV DC supplies. But they are capable of providing high peak currents and volategs into SMPS designs and blowing the primary rectifiers..
Eff off.
In article , The Natural Philosopher writes
Just about every maker of surge protection devices disagrees with you, as a quick google demonstrates.
Example:
Take a look inside some surge protectors that provide common mode protection then come back and tell me that again.
On Thursday, September 6, 2012 8:36:49 AM UTC-4, The Natural Philosopher wr= ote: And MOVS are not applied between phase and earth. That would result in ins= tant RCD operation.
Discussion is confused by two completely different devices that, unfortun= ately, share a same name. An effective protector is from each phase to ear= th. It never tips an RCD (or GFCI) because the protector looks like an ope= n circuit (disconnected) when a surge does not exist. =20
Effective protectors are for lightning strikes (and other lesser surges).= Effective protectors even have numbers that say it is for protection from= lightning - ie 50,000 amps.
Undersized 'profit center' protectors are for tiny surges that typically = cause no appliance damage. As others have noted, protection already inside= appliances makes that tiny surge (and that tiny protector) irrelevant. Th= ose tiny protectors are rated maybe in hundreds of joules. The surge that = can overwhelm protection already inside appliances is something like hundre= ds of thousands of joules.
A protector for appliance protection is for surges that are hundreds of t= housands of joules. Is provided by other and more responsible companies in= cluding Keison, ABB, Siemens, General Electric and others. That undersized= protector for tiny (irrelevant ) surges is often promoted with brand names= such as Belkin and Tripplite.=20 =20 An effective protector must remains functional even after direct lightning= strikes. Protectors that are catastrophically destroyed (a potential hous= e fire) or that degrade significantly are ineffective. Are profit centers = sold because it happens to have a same name even though it is a completely = different device.
An effective protector means surges, such as direct lightning strikes, do= not overwhelm protection already inside appliances. Do not even harm the p= rotector. These superior devices, that cost less money, make the 'always re= quired' connection from phase to earth. Only when a surge exists. And too= quickly to trip an RCD.
Whivh has NOTGING to do with surge arrestors sold fr domestic use downstream of an RCD.
Domestic units do not provide such protection.
Except that lightning upstream of my 11KV transformer often trips my RCD, so its hard to see how anything that acts slow enough to absorb a full lightning common mode surge, which patently DOES trip an RCD, can function effectively *without* tripping one.
In short common mode protection MUST be upstream of the RCD.
Domestic surge protection devices are NOT common mode.
partly because it's impossible to do so in a plug-in device - it needs to be designed into the premises wiring and building earthing system. By the time you're out as far as a socket outlet, the earth impedance is too high for common mode spike protection to work.
En el artículo , The Natural Philosopher escribió:
You're responding to a well-known idiot for whom Usenet is a write-only medium and who only ever responds in his own particular dogmatic fashion to posts about surge protection. He probably has a Google Alert set up to email him when a thread such as this one is started.
Search Google groups for w_tom, w_tom1, westom, westom1 AND 'surge protection' before you waste any more time on him.
En el artículo , Andrew Gabriel escribió:
According to TNP and the saintly Wikipedia, which of course is never wrong, you are incorrect. I know who I believe.
Yes. And basically who is confusing whole house protection - for which I utterly agree common mode protection is ideal and possible, if probably unnecessary - with what comes in a wall plate. which assuredly is not.
We look after some communication and radio transmission sites. On those its all down to shunting critical paths and the correct bonding.
I don't think theres one surge arrestor in any of them !...
cable management.
protection built in? I was going to add some more plugs for behind the AV unit but really I'd need them surge protected, and I'm trying to avoid having a 4-way kicking around.
They don't work effectively so don't waste your money.
On Thursday, September 6, 2012 3:26:24 PM UTC-4, tony sayer wrote: We look after some communication and radio transmission sites. On those it= s all down to shunting critical paths and the correct bonding. I don't thin= k theres one surge arrestor in any of them!
Of course. Best protection is a short wire to earth; not a protector. S= ome of the best protection has no protectors. But always has that short (l= ow impedance) connection to earth. Protectors are implemented only when an= incoming utility wire cannot connect directly to the earthing electrode. P= rotectors do not do protection. A protector is a connecting device. It co= nnects (bonds) to earth when the incoming wire cannot be earthed directly. = Many facilities have no protectors. But must always bond low impedance to = earth. Because earth ground - not a protector - does the protection.
And a lot of web sites that demonstrate that the LED that informs you that the surge protector is working perfectly is still lit when the MOVs have been removed from the circuit.
En el artículo , alan escribió:
Yes. ;-)
The "surge protection working' lamp was still illuminated on these:
You may be able to get them at the pound shops but they may also be in the unsolicited catalogues pushed through your letterbox at a price that is significantly higher. Price is often no indicator of quality
It will go where it thinks fit!, and that can be anywhere. Thats the principle of the lightning conductor to provide an as low impedance path as possible to Earth...
In a very close or direct strike if the aerial lead gets in the way then thats usually vaporised. I wish now I'd have kept some pix I had of instances like that!..
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