surge damage
- Thread starter hapihari
- Start date
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The damage occurs when any peak transient voltage is greater than the breakdown voltage of the components in the equipment. This is not necessarily when the supply actually fails or re-instates.
Does not matter if powered on or off. A surge current is electrically different (superposition) from AC power current. A surge current may even cross a millimeters gap inside a power switch. Or simply use the other AC wire to connect to earth, destructively, via an appliance.
AC mains current may cause additional damage either before power is lost or after power restoration. That additional damage often causes a circuit breaker or fuse to eventually trip.
To better understand, first appreciate what caused damage. A surge is a connection from the cloud to earth. That current must exist simultaneously out of a cloud as it is also flowing into earth. Your electronics must be in that path (have both an incoming and an outgoing path) for damage to occur. Obviously, AC power on or off makes little difference.
WTF are you on about ? Do you think surges are only caused by lightning and must be in a series path with a lightning strike ?
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Maybe they don't have pikeys stealing neutral links from substations in the US of America
Obviously, other destructive transients (electric utility switching, squirrel shorting a transformer, etc) also create the same typically destructive transients - incoming on AC mains and outgoing to earth.
These are a most common and destructive anomaly. Does not matter if the 'victim' is powered on or off. This transient can sometimes cause overstress (an appliance fails maybe a month later). So, yes, the actual harm (ie exceeding a breakdown voltage) can result in failure later. That current is electrically different from another current also on AC mains.
Lightning is a typical example of damage. Protection from those other anomalies is same protection implemented to make lightning irrelevant.
Problems with dis-connected or bouncing neutrals are probably far less common in the US as the distribution network is different from the UK.Maybe they don't have pikeys stealing neutral links from substations in the US of America
The "substation" for many US domestic supplies is often a tin can transformer on a pole supplying a few houses. 11kv ( or something like it ) is strung from pole to pole along the street to feed these tin cans. For these consumers there is no neutral link to earth as we in the UK know it.
The term "power surge" covers a lot of different events.
The supply voltage increasing from nominal 230 to a high voltage ( can be over 400 volts if there is a network cable fault ) that causes lamps to blow and heaters to burn out. Motors may over speed and be mechanically damaged and power supply unit is equipment will also be damaged
Floating neutrals which pull the CPC voltage high above ground voltage that can lead to damage to anything that has an electrical connection to true ground. ( the result of theft of neutral to ground bonds at the substation )[/quote]
A term 'surge' or 'power surge' is quite specific. From the IEEE, an overstress condition that has a duration of less than a few milliseconds. A swell is an overvoltage that can last a few cycles. You have described an overvoltage. All specifically defined by the IEEE.
But the OP was even more specific. He did not just ask about a surge. He used adjectives to further define his question.
He is not asking about an overvoltage. He even used the word "transient" - which says nothing about overvoltages created by copper theives or similar disturbances.
BTW, every consumer power system has a neutral. Better systems also earth that neutral at each subscriber connection to further make damage from some overvoltage anomalies less likely.
Meanwhile, transient power surges are currents that do damage by connecting to earth destructively inside the building. Lightning is a most commonly understood example.
redundant post deleted
I am sure the term "power surge" has been used by many spokespeople to describe events where damage has occurred to equipment as a result of . Not accurate but it seems to be a term the general public accept when something noticibly "bad" happens to thier electrical supply.
Destructive surges typically occur maybe once every seven years. But when an anomaly causes damage, then advertising has so many automatically blaming a surge. Too many even describe a blackout as a surge.
Transients occur every day. Most are only noise. Transients that are made irrelevant by protection routinely inside every appliance. The concern is a rare transient, maybe once every seven years, that might cause damage. A number even less frequent in the UK.
Our friends over the pond tend to have more of a problem with open circuit neutrals than we do. Their domestic distribution tends to be one or two houses on a transformer that is configured with a 120-0-120 secondary - ie. a three wire split phase service. Small loads (lamps, TVs etc) are connected between one hot & neutral (and hence see 120V), heavier loads like the range (cooker) are connected between the two hots and hence operate from 240V.
If the neutral is lost then two 120V loads end up in series.... now the voltage across each loads depends inversely on the load impedance hence the 240V may be split, say, 180V & 60V ..... you can guess what happens!
Several house fires in the US have been put down to surge protected power adapters getting very hot when subjected this this kind of extended overvoltage and setting light to their plastic casings.
It would have been nice to thing that these would be protected against such a failure mode, surely all it takes is a thermal link in the supply located over the surge protection components?
I had overlooked that problem.
My thoughts were directed to the loss of a neutral that affected a whole street where a high load on one phase would pull the neutral towards that phase and thus increase the phase to neutral voltage in the houses on the other phases.
I understood your concern. That failure would result in low or no voltage. Meanwhile, the other neutral failure is, well, that was also explained:
Of course that is completely irrelevant to the OP's question.
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