What's the lifetime of a mains surge protection module?

[treez]

What's the lifetime of a mains surge protection module?, ie one of the littelfuse "thermally protected varistor modules"..

Littelfuse surge protection module:
https://www.littelfuse.com/products...le/led-lighting-surge-protection-modules.aspx

...none of their literature gives an expected lifetime.
I am speaking of indoor mains use, ie commercial, industrial or domestic, but indoor.

 

[FvM]

Lifetime is given in the datasheet as number of surges handled by the device.

 

[xenos]

Depends on the surges that will have to short. How much current/energy and number

 

[treez]

Lifetime is given in the datasheet as number of surges handled by the device

Thanks but none of the individual datasheets give this...eg

Littelfuse surge protector datasheet..
https://www.littelfuse.com/~/media/...s/littelfuse_varistor_lsp10_datasheet.pdf.pdf

Depends on the surges that will have to short. How much current/energy and number

...I think you would agree with me that for any given location , this is unknown?

 

[FvM]

Number of surges is implicitely given in the Inom/Imax specification. Read the fine print.

...I think you would agree with me that for any given location , this is unknown?

Won't agree because there are at least assumptions about frequency and severity of surge events. Otherwise you can state that the lifetime is some number between one hour (or whenever the next thunderstorm hits your area) and infinity.

 

[ads-ee]

Lifetime is given in the datasheet as number of surges handled by the device

Thanks but none of the individual datasheets give this...eg

Littelfuse surge protector datasheet..
https://www.littelfuse.com/~/media/...s/littelfuse_varistor_lsp10_datasheet.pdf.pdf

Well it gives it in the Nominal Discharge Current. There is a note about the test conditions being an average value of 10,000A for 15 cycles of 8/20us pulses.

 

[D.A.(Tony)Stewart]

Only the supplier would have this data against certified test conditions.

In my day, design was chosen for both Hipot and surge protection for consumer and industrial differently, as transients 3kV or 6kV impulse , but you can check, around clause 1.5.9.2, IEC60950-1 . As I recall MOV lifespan on max rating had very few surge lifespan. Since these are cheap, many can be ganged. But we relied on line filters to attenuate spikes with MOV (fast) and gas tube with polyfuse. Each has a Joule absorption and degradation factor per strike, so that total accumulation of Joules lifetime absorption was limited and perhaps a ratio of single J discharge rating.

Not something that would work well in countries whose line voltage often exceeds 10% as better grids specify to customer. Thus series LC filter with series PTC's and shunt MOV's may be considered.

But never use gas tubes without current limiting as they act as crowbars.

 

[treez]

I cant see in the datasheet how many Inom pulses it can take for its lifetime. I can see what the inom is but not the number of transients of a lifetime...presumably its in the standards it refers to?, which cost quite a bit of money.

 

[Audioguru]

A salesman for a surge protection device manufacturer told me, "When it turns black then send it back".

 

[xenos]

A few medium energy surges, may not short or blow away the MOV but often turn them leaking (allowing continuous current between pins). This will definitely increase it's temperature.

 

[Warpspeed]

Its not a question that has a definite quantifiable answer.

If you are personally responsible for a bunch of these protection modules, I suppose the only answer would be routine testing of leakage current and keeping records.
Experience built up over time might produce a statistical picture of which locations are more surge prone, and give some indication of the various rates of degradation.

The sources of voltage transients are many and varied, and location, as well as distance from the main power entry point to the building all play a part.

 

[D.A.(Tony)Stewart]

If the mfg. cannot supply specs, then don't guess.
Choose a design that has some criteria for reliability.
E.g

 

[Warpspeed]

But how is the user supposed to guess the frequency and intensity of mains transients at a specific location ?

Only way is to do long term data logging with something like a Dranetz mains disturbance analyzer.
And then that result may only apply to one sub circuit in a large building.
And the situation could suddenly change when the factory down the road buys a new piece of really heavy duty electrical equipment.

 

[D.A.(Tony)Stewart]

You can either design to the IEC standard or customize to harsh environment to determine what level of protection your design needs or see what others do in your industry and do same or better.

 

[chuckey]

I was involved with the gas tube protection of solid state MF transmitters. The problem was that if the tube was past its sell by date, multiple transistors had to be changed in the PA module, so the local guys after a year or so, started changing the gas tubes like sweeties!
So it was arranged that after the tube was changed we subjected it to a HV insulation test, so if it struck at its spec. voltage it was returned to stock. They was no easy way to identify a failed tube we could find.
What ever spec. the manufacturers have tested these protection devices to, there is no way to know what any overload might be. Like us you have to test them and build up experience, but the testing could cost more then the value of the item being protected. In our case the costs were say, £1k for the visit and replacement of the transistors plus £500 (at least) per hour for the down time.
Frank