I am an American living in Hungary for six months. In our living room, we have a five-bulb chandelier whose bulbs burn out too frequently. We tend to keep only 3-4 out of 5 going at a time for that reason. One week ago, my wife turned on the switch, saw a bright flash, heard a loud pop, and then experienced power outage. Two breakers had tripped; the main, as well as the one for the particular circuit. Three of the bulbs in the chandelier had burnt out simultaneously, leaving just one bulb lit. We replaced no bulbs for a week, until I had time today to replace three of the burned out bulbs, bringing the number of burning bulbs up to four. A few hours later, I turned the light on, and immediately 2/4 (brand new!) bulbs blew, and the breaker for the circuit tripped again (though thankfully not the main). What would cause this and how dangerous is it? After last week's incident, several Hungarians have told us that this is "normal" here. But the pattern of bulbs repeatedly blowing does not seem to be, and has not been addressed on these forums.
Look for light bulbs that are rated for 230-400 volts. By which I mean LED, the only technology worth spending money on in this day and age. They use electronic switching power supplies, which chop line voltage into a much lower voltage. By nature they can take a variety of voltages. You just need one that's built well enough to take 400V.
If your expensive electronics are multi-voltage, but can't handle 400V, then I would get a heavy step-down transformer, and configure it for 230V in, and 120V out. When the system faults toward 400V, the "120V" side will increase in proportion, but it won't go above 240V.
What's happening is you are losing the "neutral" wire and the it's floating around, depending on the various loads on each leg. More loads pull the neutral toward that leg's extreme.
Euro power is 3 phase "Y" (3 legs with neutral in the middle) and your apartment gets 1 or 2 legs. If you remember enough high school geometry to draw a 120 degree Y shape with 230V legs, connect the corners and you get a triangle with 400V on a side. The corners are fixed and the neutral is being dragged around inside that triangle, making your power go higher or lower depending on which corner you are at.
That is not normal. The Hungarians who say that it is -- do they live in your same building? If so, it's a problem with the building neutral and the landlord oughta just fix it. If it's in the same city or region, then the power company is terrible.
What would cause this
Overvoltage or voltage surges in the supply might be the cause.
The old-type incandescent tungsten filament bulb are probably more susceptible because they have a low resistance when cold. They usually fail at initial turn-on.
Cheaper light-bulbs can also be less resilient to overvoltage.
and how dangerous is it?
It must be a potential hazard. Other devices or appliance could conceivably overheat or burn out. It depends largely on the voltage and duration.
Televisions across town catch fire after power surge caused by theft
A power surge caused electrical appliances in dozens of homes in Bolton to catch fire on Monday.
Almost 400 properties in the Westhoughton areas of the town were cut off after a vital copper safety component, worth just £20, was stolen.
"230 volts is the normal voltage and when you lose the safety gear, that voltage can start to fluctuate and can go up to 400 volts, which is far over what most appliances can handle."