Lights flickering - Page 1
Forum section: electronics / beginners

author: Grayfox
author_rank: Regular Contributor
timestamp: December 07, 2015, 11:23:59 am
content: All the lights in where I live are flicking now and then and not just the room lights, but the light in the fridge and oven too.it is not a constant flicker but a quick flick every now and then.What would be causing this?A load on the electrical system as it is summer and a lot of people are using A/C, bad power from sub station or a electrical fault in the home?

author: Psi
author_rank: Super Contributor
timestamp: December 07, 2015, 11:35:47 am
content: Any arcing on the high tension lines feeding your area will cause flicker.The arcs forming and quenching cause a voltage fluctuationHappens a lot with the 11kv lines when tree branches get too close.If the arcing is indirect there often isn't enough current to trip the breakers.A burning poll pig or substation transformer is also a possiblity

author: Lesterwyatt
author_rank: Regular Contributor
timestamp: December 08, 2015, 09:00:59 pm
content: Came across this fault once. Turned out most of the outgoing cables in the fuse box were loose in the terminals and MCBs.

author: Ian.M
author_rank: Super Contributor
timestamp: December 08, 2015, 09:10:39 pm
content: Are you in the USA or anywhere else that uses a 120V/240V split phase supply (120-0-120)?If so you urgently need to shut off the main breaker and check for an open neutral.

author: IanB
author_rank: Super Contributor
timestamp: December 08, 2015, 09:20:29 pm
content: Quote from: Grayfox on December 07, 2015, 11:23:59 amIs it a flicker, or a permanent change in brightness?An occasional change in brightness may be normal. The electricity supply typically has a voltage regulator at the main substation that uses a tap changer on the transformer to adjust to varying consumer loads. When the tap changer operates there is a small change in voltage that causes lights to suddenly go brighter or dimmer.

author: Grayfox
author_rank: Regular Contributor
timestamp: December 20, 2015, 04:20:20 am
content: The flicker stopped but then got real bad last night at midnight, when I woke up no power to the entire house.When I phoned the electrical supplier they said no outages so I checked the fuse board.No fuses blown, and got someone out.While i was cleaning the box of spider webs to make it a little easier for the sparkie I saw this.A burnt wire coming out of the service fuse, which is odd as there was no way the house hold was drawing that much current to make it blow(old one was rated to 60A) but the sparkie said sometimes they get hot and blow with age.So if anyone else has this kind of issue, check the service fuse as well as the circuit fuses.

author: RJFreeman
author_rank: Regular Contributor
timestamp: December 20, 2015, 05:14:16 am
content: Quote from: Grayfox on December 20, 2015, 04:20:20 amAn overheated wire is due to either excessive current or a bad connection. In this case the fact your fuses haven't blown, and the heating looks significantly worse at the fuse end, makes me think you had a loose/poor connection to the Fuse.

author: Grayfox
author_rank: Regular Contributor
timestamp: December 20, 2015, 05:22:41 am
content: I would say it got bloody hot, as the end connection became purplish which is normally what happens at high heatAssuming the same rules of heat oxidation apply to the contacts.

author: SeanB
author_rank: Super Contributor
timestamp: December 20, 2015, 07:11:38 am
content: Brass of the socket relaxed with time and thermal cycling, and this reduced contact pressure meant the current flow was going through a smaller area, which then heated up and this then exasperated the problem as it reduced the tension more, and the heat oxidised the copper to reduce contact area.That is why they normally use a spring steel backing spring on those terminals, and use a grease to keep them clean and corrosion free. For high voltage and reliable ones they use an oil filled housing, as that means there is no corrosion even after decades of sea exposure, with only a maintenance cycle every 5 years to check and repair outer housing corrosion. The inner side looks like new.House fuses are rarely changed so the dry contacts do not get a wipe cycle to clean them and verify the contact tension is sufficient ( means you need to use a lot of force to pull out both sides, and they do not just fall out), and the linesmen and installers rarely use the grease on them, even though it is a recommendation of the manufacturer.

author: fubar.gr
author_rank: Unknown
timestamp: December 20, 2015, 12:17:31 pm
content: Bad electrical connections stand out like a sore thumb on a thermal camera image.When I got my FLIR E4 camera, I did a quick check of the electrical panel at my workplace.This is a three pole switch for a three phase motor. The temp originally was over 50 C and I immediately turned it off. The photo was taken a couple of minutes later, hence the lower temp.And this is what the switch looked like. A disaster waiting to happen.

author: Brumby
author_rank: Unknown
timestamp: December 20, 2015, 12:49:59 pm
content: Quote from: fubar.gr on December 20, 2015, 12:17:31 pmThis is why I am looking at gettingsomethingin the way of a thermal camera. Even a Seek XR would have found this.

author: IanB
author_rank: Super Contributor
timestamp: December 20, 2015, 03:17:16 pm
content: Quote from: Brumby on December 20, 2015, 12:49:59 pmEven the Mk 1 human sensory apparatus would have found that. Just wave your hand near something vaguely warm and the heat receptors in your skin will readily detect the heat radiation. Nature invented the bolometer long before humans did.

author: fubar.gr
author_rank: Unknown
timestamp: December 20, 2015, 03:35:05 pm
content: Quote from: IanB on December 20, 2015, 03:17:16 pmActually no.50C is not hot enough to feel the heat just by waving your hand over.Even touching it can be misleading. Plastics do not conduct heat well to the human skin. Plastic at 50C doesn't feel any different than plastic at 20C