Does UK mains have a fault mode where a single whole mains half cycle is just absent?

When the UK mains fails, I presume it either goes off completely, or the peak value decreases? I assume that one never sees (minor) failure modes whereby everything is normal, but say a complete, single mains half cycle is absent?

This is in relation to a dimming signal technique involving signalling by use of absent mains half cycles, switched out by a transistor arrangement in the mains live (but we couldn't do it if it occurred in the mains supply system anyway)

Also please answer for European mains, USA mains, and Far Eastern mains?

Something like that was trialled to automatically operate street lighting many years ago. A detector circuit in the lamp controller looked for a brief DC offset in the mains caused by one or more missing half cycles. It think it was abandoned quickly for several reasons, primarily that it upset filter circuits and the combined effect of many (re)charging capacitors would falsely trip RCCB fuses.

These days the other reason not to do it is the number of grid tied inverters across the mains. They have to maintain perfect synchronism with the AC and instantly disconnect if a disruption in voltage or frequency occurs. I have about 2KW of PV inverters running here and even switching a fluorescent light on sometimes resets them. I live in a remote location and have already had ~25 power outages this year. They are a real pain because after power is restored it takes about 2 minutes for the inverters to analyze the mains before kicking in again.

Overlaying a higher frequency carrier with data is a far better solution for mains signalling.

Brian.

It think it was abandoned quickly for several reasons, primarily that it upset filter circuits and the combined effect of many (re)charging capacitors would falsely trip RCCB fuses.

Click to expand...

sorry I should have mentioned that we are PFC flyback and don't have caps on the primary bus.
Also, I apologise because I forgot to say we have a mains zero crossing detector and do the switching in coordination with that.
As such, we would switch the mains out exactly at the zero crossing, and switch it back in exactly at the zero crossing, so we wouldn't get ringing in LC input filters.

I would answer the question with a reference to EN61000-4-11 which requires an instrument to widthstand a half or full period voltage sag to 0 % without function loss.

Similar voltage sags can happen due to switching actions in the distribution network and particularly during lightning caused arcs in overland lines, although they are quite rare.

The frequency can vary.
Brownouts can take many forms, depending on the cause. Consider a squirrel getting fried in at a substation...
I've seen intermittent "chattering" caused by wind blowing the 230V overhead cable when there's a loose/corroded connection between the wire going along the street and the wire going to my house.

Sometimes, when demand was 'high', we used to get 'tap change' glitches that took down the power for more than a mere flicker.

The room lights would blink out, TV's picture would collapse, the VHS player would stall, and my PC would re-boot...

Not Funny.

Even worse when it happened at work and took down much of our analytical equipment. Can't just re-boot such, you have to re-do all the daily checks before picking up the pieces of 'work in progress'.

Fortunately, modern 'switched power supplies' seem able to bridge such single-cycle outages. Still, I keep promising myself a hefty UPS unit...

Once a year or more on a Friday at about 1730 Hrs, our RCD used to trip, it was caused by the local tap changer operating as the local industrial estate went home for the week end. Here in a country location we are slightly troubled by flickers on the mains. trouble is the micro controlled radio/TVs etc. reset and need switching on again!!!
Frank