Voltage low as 74v after blackout. What's wrong?

Forums › Home Workshop DIY › Voltage low as 74v after blackout. What's wrong?

Shin

274 posts

Ultimate Geek

#233354 12-Apr-2018 22:03

Hi

After the black out last Tuesday night and power back on Wednesday afternoon, we are only getting 70-140v from the power socket.

Our digital power metre is blinking and showing something like F10000... changes number.

We cant use refrigerator, washing machine and water pressure is very weak.

Equipment like modem or phone charger, laptop charger still works as the adaptors are free-volt however majority of electrical are not working properly and all our LED lamps are flickering.

Is it normal for many of people in Auckland now or as long as the power gets in, it should be 230v and something wrong on my house alone.

Can you give me some idea? I am at Dairy Flat area.

Cheers

Heesang

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3885 posts

Uber Geek

#1995083 12-Apr-2018 22:19

@Shin Turn off your mains switch NOW This is often caused by a failed neutral connection. A kid was killed in Australia recently

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Aredwood

3885 posts

Uber Geek

#1995084 12-Apr-2018 22:22

This can cause all of your water pipes, sink benches, appliances etc. Everything that is connected to the earth wires to become live.

Turn off your hot water cylinder power switch as well. As there are some old switchboards out there that don't have the hot water cylinder wired through the main switch.

Call your power company or an electrician in the morning.

Shin

274 posts

Ultimate Geek

#1995085 12-Apr-2018 22:22

Main at power metre?

What could cause this happen? Inside the house or outside lines?

Aredwood

3885 posts

Uber Geek

#1995087 12-Apr-2018 22:29

http://www.nzherald.co.nz/world/news/article.cfm?c_id=2&objectid=12021969

It could be your house, the cable to the street, or something wrong with the street wiring or transformer.

Either way, it is a serious safety hazard. Don't turn the power back on until the cause has been found and fixed.

Aredwood

3885 posts

Uber Geek

#1995088 12-Apr-2018 22:30

Turn it off at your internal switchboard. As the metal case of your outside meter board might be live compared to the outside ground.

Aredwood

3885 posts

Uber Geek

#1995089 12-Apr-2018 22:36

There is also a possibility that the mains voltage can also go higher than normal as well. After you have turned off the mains switch. Unplug your TV, computer, and all other electronic appliances etc.

Yes I know that no power on a cold night is annoying. But you have a serious electrical fault. And depending on exactly where it is, also a potential major fire hazard.

Aredwood

3885 posts

Uber Geek

#1995090 12-Apr-2018 22:37

@Shin Please report back with what the fault turns out to be.

Shin

274 posts

Ultimate Geek

#1995092 12-Apr-2018 22:44

Is it not a chance that the grid is over loading so I am getting low voltage?

We had no such problem before the black out and there was no flood damage. It only happen after the power back on.

I have called Vector ever since power back on but they are not answering.

Now I have switch off all except some power socket outlet to have modem run

Aredwood

3885 posts

Uber Geek

#1995093 12-Apr-2018 22:55

No it won't be the wider grid. As it operates to strict voltage tolerance levels. And it has equipment that will automatically disconnect the power is the voltage or frequency gets too low or high.

If you have overhead powerlines to your house or on the street, the problem is probably outside somewhere. But what I have said before regards safety still applies. With a low voltage fault, you have to assume extreme danger until it has either been fixed or proven safe.

As well as a safety hazard, the low voltage can also cause motors in appliances like refrigerators to overheat and burn out.

Turn the main switch off again and use mobile data for internet on your phone.

Aredwood

3885 posts

Uber Geek

#1995095 12-Apr-2018 22:57

Vector would be flooded with calls right now. If you have an Android phone, Download the Vector App. As you can use it to report faults. And see what areas still have outages.

Shin

274 posts

Ultimate Geek

#1995097 12-Apr-2018 23:07

Yes I have used App to lodge fault several times. No call or email yet.

Are there any way to know what input voltage from the street from the digital metre?

I have shut down switch on my home switch board, there is another switch from the street to digital metre.

michaelmurfy

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13163 posts

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#1995102 12-Apr-2018 23:26

Speaking from experience - switch it off at the main breaker where your meter is. Wait until you've been given the all clear from the power company.

I've had the situation where random things went live in my house before - not fun, and got an incredibly nasty shock twice from it too. Trust @Aredwood - he does know what he is talking about. My situation was caused by a loss of Neutral and everything was going to Earth after a storm. It sounds like this is the case with you also. It caused a few things to not work and lights to flicker and caused my UPS to be incredibly grumpy with me and burn out.

Be very cautious. Also, this kind of voltage is not good for even your router which may be working, but its poor power adapter won't be happy. Check your neighbours and if they've got the same fault it'll be on the street somewhere.

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Shin

274 posts

Ultimate Geek

#1995103 12-Apr-2018 23:29

@michaelmurfy thanks for your say. were the problem outside your house after the storm?

Aredwood

3885 posts

Uber Geek

#1995105 12-Apr-2018 23:33

Be very careful even touching anything near the meter box. As if the meter box is metal. It might be live compared to the ground outside. You might get electrocuted just by touching it. That is why I said to turn the power off at the internal switchboard.

In fact, if your house has metal exterior cladding, roofing, gutters, downpipes etc. Even they may be live.

If your internet is xDSL you might even get some mains current in the phone wires, and end up destroying your modem/ router.

michaelmurfy

meow
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#1995106 12-Apr-2018 23:39

@Shin In my case it was - loss of neutral from the street. Somebody from the lines company came by and fixed it up and said how lucky I was to have turned it off.

The shocks were no joke but lucky for me I knew what it was pretty quickly that was causing it and I was not fully grounded (had shoes on both times). I never want to go through that again and looking at that article I am incredibly lucky. I've had some close calls with electricity but the rule of thumb is, if your electricity supply is dodgy then just don't risk it - turn it off at the main breaker where your meter is. Don't test this theory either - it hurt like hell... The shocks I got were off the fridge and off the kitchen tap in quick succession. Furthermore, I've even gone as far as to turn off things during powercuts except things protected by a UPS as it is amazing how dirty power is when it gets first switched on after a blackout. I've had electronics fried in the past.

We're not saying it is specifically the case with you but you're best to err on the side of caution here especially dealing with something with the potential to kill.

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