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Topic Title: Unexpected dimming of lights.
Topic Summary: Why is it happening when the load is removed?
Created On: 22 September 2017 09:43 AM
Status: Read Only
Linear : Threading : Single : Branch
 Unexpected dimming of lights.   - potential - 22 September 2017 09:43 AM  
 Unexpected dimming of lights.   - kellyselectric - 22 September 2017 12:14 PM  
 Unexpected dimming of lights.   - nad - 22 September 2017 01:00 PM  
 Unexpected dimming of lights.   - mapj1 - 23 September 2017 12:15 AM  
 Unexpected dimming of lights.   - potential - 23 September 2017 10:16 AM  
 Unexpected dimming of lights.   - mapj1 - 23 September 2017 12:32 PM  
 Unexpected dimming of lights.   - OlympusMons - 24 September 2017 02:12 PM  
 Unexpected dimming of lights.   - potential - 24 September 2017 05:41 PM  
 Unexpected dimming of lights.   - potential - 24 September 2017 05:44 PM  
 Unexpected dimming of lights.   - MWalker86 - 24 September 2017 11:10 PM  
 Unexpected dimming of lights.   - kellyselectric - 26 September 2017 12:48 PM  
 Unexpected dimming of lights.   - kellyselectric - 05 October 2017 11:12 AM  
 Unexpected dimming of lights.   - alancapon - 24 September 2017 06:11 PM  
 Unexpected dimming of lights.   - kellyselectric - 24 September 2017 07:52 PM  
 Unexpected dimming of lights.   - potential - 05 October 2017 01:57 PM  
 Unexpected dimming of lights.   - potential - 05 October 2017 02:01 PM  
 Unexpected dimming of lights.   - kellyselectric - 05 October 2017 04:41 PM  
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 22 September 2017 09:43 AM
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potential

Posts: 1642
Joined: 01 February 2007

Yesterday I encountered an electrical phenomenon that I have not experienced before.
I wonder if anyone can explain how and why it is happening?

I'll start at the beginning.
I was working in my shed at the bottom of the garden.
At the same time my wife was clearing up the garden using an electric leaf blower.
The shed is fed by a 3-core 4 mm cable approximately 30 metres long supplied from a separate MCB + RCD supply taken off the house single phase meter.
5x standard 5ft fluorescents and 2x 80-watt metal halide lamps all with conventional ballasts light the shed.
Initially my wife used an outside socket on the shed.
I noticed she was switching the blower on and off quite quickly and all the lamps in the shed were dimming momentarily every time she switched it on.
Nothing odd in that I thought but made a mental note to tell my wife it wasn't a good idea to cycle the motor so rapidly.

Then she moved further towards the house and unplugged it from the shed socket to an outside socket supplied from one of the ring finals in the house.
That ring is connected to a RCBO in a different CU but supplied from the same meter.
(The house supply cable is underground and is supplied from a small substation just down the road.)

She continued to switch the blower on and off.
This time the lights in the shed hardly dimmed at all when she switched it on, as I'd expect.

However each time she switched the blower motor off all the lamps in my shed dimmed quite markedly approximately half a second afterwards.

What would cause that to happen?
Any ideas?
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