Lets have a look at some other capacitors

https://www.we-online.com/en/components/products/pbs/capacitors/film_capacitors/info

Go down to the FAQ at the bottom - "Can X2 caps be used in series with the mains ?"

Some applications called capacitive power supply or transformerless capacitive dropper use X2 capacitors in the input line (between mains power and the load). This use is called “in series with the mains”.
For this application, special THB X2 capacitors with explicit confirmation of this application must be used. We confirm this for certain types by specifying “Across the mains or in series with the mains” under “Application” in the data sheet. Würth Elektronik offers X2 THB film capacitors under the series WCAP-FTXH.

Seems very standards and ratings related, unless....

THB is not just some name of a series of capacitors. It stands for Temperature Humidity Bias - testing in which the capacitor life and reliability are tested under conditions of Temperature, Humidity, and Bias (applied voltage)

Yep, they are also concerned about humidity. From a manufacturer that does not make and never made paper capacitors

Wait a sec.. So to work in a capacitor/zener application, the capacitor must be one specifically made to last under THB conditions, but for plain X2 application for EMI filtering (which is definitely not any better working condition in terms of applied voltage/transients), all of that is not needed ?

EMI testing (to get certification for the product the capacitor is installed in) is performed on the 1st sample unit of the product and takes a few hours. (Assuming the unit may be powered for other testing and demonstrations before it arrives for EMI testing, make that a few months). Nobody will notice that it went missing afterwards. That is exactly as long as the EMI filter capacitors are required to last in the eyes of product manufacturers

This won't work for a capacitor which actually matters for the functioning of a product, which will result in mass warranty claims and recalls



For capacitors which design is older than some of the tests in question, yet actually last and stay in spec for the first 20 years, Rifa PME are anything but garbage

They are what they are - compact "metallised film" (assuming paper is a film) capacitors which are electrically fairly good, but have a unique other fault mechanism which is non electrical in its first stages, before it progresses into an electrical fault



The reason why old capacitors last long electrically is the low extent of process control in theirmanufacturing. Let me explain :

Life of film capacitors has a very strong relation to voltage. Life is proportional to (Vapplied/Vrated)^n, where values i seen for n = 7, 8, 10, 20 acc. to different sources (varies by film material, thickness, and individual manufacturers)

With older processes the film thickness uniformity, and risk of existence of pinholes, were not very precisely controlled. So they were made with overkill film thickness in the 1st place to guarantee that they work reliably

In PME capacitors it is also the fact that the dielectric is paper, naturally a fibrous and not very uniform material, which again results in some more margin taken in the design

All capacitors with metallised film technology (maybe except the earliest ones) have a self healing mechanism - Blowing up of metallisation around pinhole film breakdowns, allowing the capacitor to continue working after such event. In contrast, in foil capacitors every isolation breakdown is immediate full failure by shorting out

In modern capacitors the precision with which the film can be made (thickness, uniformity, cleanliness), and precision of models to estimate its life, allow to shrink it to exactly the thickness at which it will survive the rated voltage, with the self healing mechanism "ticking" just slow enough to be acceptable for an intended rated life

In most X2 capacitors nowadays the film is so thin that corona discharge around the edges of the metallization pattern (think of it, sharp edges of a metal layer of the thickness of microns-scale coating) becomes equally significant factor in the destruction of the metallization. They arent even "ticking" anymore, they just burn away continuously

The self healing mechanism really works exceptionally well if with all this, we don't see the modern capacitors explode and go up in smoke every day. But it too has its limits. Once in a while there will be a modern X2 capacitor completely melted

Yeah this is quite a stupid thing to do, but I really disagree with the statement "moron".  I have been watching this youtuber for a long time and he's one of the few who kept the original YouTube era content style. Never clickbaits, listens to viewers, has his own unique style, and keeps saying "this is just for science" and "do not attempt at home under no circumstances", check the description. Also, in regards to people saying "shut him down to protect the kids", no, it is not YouTube's job to do that, If you remember, there used to be a concept called parenting, and originally people with that role are supposed to protect their kids from exposure to potentially dangerous content.

Ah yes, another beautiful example of these damn RIFA Caps!!!  I have had problems with COUNTLESS.  I repair and restore audio amplifiers as another hobby of mine, and these capacitors are used in quite a lot of them. They are pure garbage!    Moisture gets inside of them, and then it is game over.  I had a few larger examples explode and fill the whole room with smoke, like a smoke machine! It was seriously impressive. But it created a huge oily mess to clean up afterwards, heh .I always replace these now, they are way past their prime to say the least I think they were fairly cheap when new, so they probably never were the greatest quality. 

Nothing beats a metal can capacitor that is properly sealed, I run a lot of filter and PFC capacitors from the 1950-1960's daily and have done so for countless years at this point without a single problem! ''Super-Purity Chlorinated hydrocarbon impregnation'' keeps the moisture at bay, still to this day!  Properly fused and protected, a explosion is unlikely in the event of a failure.

Old capacitors are ALWAYS better than new ones, except for paper and foil caps (and RIFA cubes like these!) that love to get electrically leaky and screw things such as tube-circuits up! I always replace those with Poly-film caps instead. But filter and PFC capacitors that are metal can types... If they are good, I keep them

I have put thousands and thousands of hours on the original filter capacitor in my daily use amplifier from 1957  

The precission frequencies were even easier to get in the past (at least here):
In the time of analog TV, the TV scan and color carrier frequencies were based on the national time standard. So once the TV got the signal, you can easily tap on either the deflection (the horizontal was the easiest to get, just one turn around the HV transformer and you got 100% insulated pulse output), or with a bit more complex mod into the PAL color carrier frequency.

With digital TV it is not that simple to extract anymore. Although once the same multiplex is broadcast synchronously using multiple transmitters, they need to be precisely synced together so the signal itself is precise (usually again locked to some national standard), it is not that simple to extract anything usable from that for a DIY calibration use.

But today the GPS is I think the easiest to get and the signal quality from these receivers is way superior (the phase noise, aka jitter) to the other methods, as the basic location function itself needs that precision. And because of the mass production, those things became very cheap...

Yes had this with several Tridonic's of this era, the first one I came across was a 1994 PC 2x16 C001 which tripped the RCD within a few minutes of being powered. Of course new caps sorted the problem and for now the electrolytic cap seems to be ok after 30 years storage.

I've had several others from the late 90's and early 2000's that I have replaced the Rifa's in too, most recently these PC 36 E011 IDC ballasts from 2002. Now I've started replacing them with a Rifa PHE 850 plastic film cap which seems to do the same job and hopefully won't degrade in storage in the same way the PME ones did.

The newest one I have come across is this EM 36 ST self testing emergency module from 2010 that had a pair of them in which had also cracked, again replaced them with some plastic film equivalents. Not sure what the purpose of them in that one was as they are not on the input end but rather around the lamp disconnection relays instead.

It is always worth opening up any Tridonic HF ballast from the 2000's or older and checking for them as its quite annoying to install the ballast and later have issues with RCD tripping due to the capacitors failing.
It seems by the mid 2000's in the new PC PRO ranges they switched to a plastic film cap similar to the ones I have started fitting as replacements for the failed PME's, but the older PC C001 and PC E011 ranges are almost certain to contain them.

@RRK
Thank you. This multimeter's limit is only 1kV peak so ignitor pulses are certainly out of range here. It seems like calibration is probably not necessary yet.

@Medved
Thank you. I had no idea these precision frequencies were so easy to get. I will definitely try that out if I need great precision.

RIFA PME capacitors are not notorious for the fact of them failing. They are "notorious" for the fact of making it visible

The most common other type of capacitor used nowadays are polyester X2 capacitors (from multiple manufacturers). Many of them last only a handful of years before failing, except they fail silently by electrically burning away the metallization on the film

Daim and Mex are some brands of plastic caps that tend to fail rather quickly. I've seen many of them which have lost their capacitance within 10 years of use. There are more. The only good thing about those, is that they don't go up in flames.

As you say, it is of the utmost importance for the engineer to check the datasheet for what applications they are suitable. Many of these are used as a series capacitive dropper. Slowly but surely they then lose capacitance and eventually cause the device to quietly fail. Philips had a major recall for their Senseo coffee machines that failed in exactly this way.
There are other capacitor types with different dielectric which are more resistant against big voltage spikes you can find on the mains. I don't know which ones. FKP, MKP, MKT...

Either way, for anyone replacing these things in lighting fixtures, get an X2 or Y2 type, and preferably a Wima, Panasonic or other good brand. I wouldn't put another Rifa PME back into it. It might last another 20-30 years which for some may be plenty, but if that fixture is sold to another person who doesn't know it, they might simply throw it away if it starts smoking.

My parents have thrown away a BEAUTIFUL kitchen mixer in my childhood because its suppression cap burnt out. They didn't know how to fix stuff and that it's not the motor that burnt out, so even if you get it to a professional repair person it would be a cheap fix, and i was 10 or so so i could take it apart but i didn't know what caused the smoke. It was a very heavy AEG machine, early 70s, very powerful. I somehow remember the chassis as being made from ceramic, but it may also have been white bakelite.

Medved :

But this problem will also exist if the power is interrupted 2 times, the first time extinguishing all HID lamps, the 2nd time stopping the motors with "unloaded" capacitors of the entire lighting installation...

Cold HID lamps have low arc voltage (can get as low as 20V for the first few seconds in an 100V-arc HPS). At this time the ballast pulls higher than normal current, at very low inductive power factor. A higher value capacitor will reduce the current draw in this stage

But there are some reasons why NOT to overcorrect the power factor this way :

1.
The purpose of power factor correction is to prevent reactive current going in the supply lines, causing unnecessary losses and loading of the power line

The problem is not only for the lighting circuit itself, but for the main feeding cables for electrical installations that power also other loads - which are already "undersized" due to diversity factor of those other loads. (The diversity factor of lighting is 1, but of entire installations can be anything like 0.5..0.7)

So it makes the most sense to optimize the capacitor value to correct the power factor as precisely as possible in the long run when the lamps are warmed up, not in the short period when they are cold

2.
The circuit conductors and circuit breakers can take some overloading for short periods, which is adequate for letting HID lamps warm up (even if it starts at 2x current, as long as it goes down fast in the first few seconds after that, and stabilizes at 1x within a few minutes)

3.
The capacitors have extremely high inrush current at the moment of connecting to the line (the first AC half cycle), which is proportional to the capacitance and circuit impedances

Higher capacitance makes the circuit require bigger switching gear (switches, contactors) to withstand this inrush, and may get close to the limits of magnetic tripping (short circuit tripping) of circuit breakers immediately at switch on, especially if "B" breakers are used (as is common in some places in Europe)



The capacitors in European gear are normally sized to correct the power factor to about 0.9L to 0.95L (L=inductive) for the condition with warmed up lamps at full power, and rounded to the nearest standard capacitor value

This in theory leaves some more capacity to go before getting to PF 1.00 or even more before 0.9C (which may be still acceptable), but probably not that much, and i wonder where the oversized capacitors actually are on this scale

It is generic problem for all paper capacitors. It is practically impossible to really prevent any moisture to seep in it, unless it e some special hermetic construction (molded plastic/epoxy cases aren't). With older vacuum tube electronic (old radio, TV, audio gear) a leaky capacitor can easily destroy the tubes, so it is often way better to just replace at least the critical ones (interstage coupling from anode to the grid of the next tube) before even attempting to power the thing up, if those capacitors are some of the paper type (paper wax, these Rifa ones,...).