Electronics > Power/Renewable Energy/EV's

restoring power myth?


Is it true that there is a danger to electronics when the power is restored after a blackout? Everyone I know seems to think that there is a large "surge" that happens when power is restored.

What really happens?

Yeah, this happened to me recently, when the power comes back it likes to blow up MOVs. I got a whole house surge arrester after I had to replace 4 power strips and a clock and something else

I don't know why but it seems that power up has regulation problems.. it might be beneficial to keep the breakers off until you know it stabilized. at least thats what I would like my house to do but its a little pricey for a once in 20 year occur ace

and possibly it damaged appliances, i got a dehumidifier and portable AC with problems only 1 year of ownership (including the event).. not sure if it got touched by a surge or if it was just built really bad.. still need to investigate.

There is a massive surge of demand as all of the motors in things like refrigerators try to power up all at once, so you can get some pretty nasty spikes and brownouts. It really is better to shut off what you can prior to power returning just to ease the load on the system. I've never had any equipment damaged by it but why risk it?

Have you noticed the way the lights dim for an instant when an air conditioner, heat pump or in some cases even a domestic refrigerator kick on? Now imagine potentially thousands of those being switched on all at once.

We had a about a 30 second power outage and then after that our washing machine was showing a water level fault. So we called a repairman.  And he showed me how to reinitialize the system to factory start and it worked fine.  That was in the manual.  Maybe I should have looked at the manual. 


Yes there is a large inrush current surge into all the devices when the mains comes back on...charging up all the input capacitors.
This high current puts a lot of energy into the stray inductance of the mains grid wiring....when the inrush stops, the energy is still in the stray inductance, so it causes an overvoltage spike to all equipments.

If the mains grid wiring had zero stray inductance (impossible , i know), then there would  be no bad surge problem when the power gets restored to the grid.

By "grid", i mean the "national electricity supply system."


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