Safe T Cut immediately trips

[Crossy]

Just now, sandrabbit said:

Crossy after looking at the picture I can't see an earth wire going to the safe t cut, I thought from your electrical write up and I seem to remember from downloading the manufacturers pdf that a safe t cut needs to have an earth connection?.

 

Yes, the Safe-T-Cut instructions have a ground in order to implement MEN, if your installation is TT the unit will operate just fine without it.

[sandrabbit]

Just now, Crossy said:

 

Yes, the Safe-T-Cut instructions have a ground in order to implement MEN, if your installation is TT the unit will operate just fine without it.

understood, cheers.

[Gulfsailor]

46 minutes ago, lopburi3 said:

If not too hard I would first make sure that smoking emergency light fixture is removed from system by unplugging it, not just turning breaker feeding it off.  

It's hard wired into a junction box behind a light switch. But thinking about that, I'm sure it's not grounded, because the lights aren't either. So even if things are molten to a crisp inside it, it can't trip the safe t cut without a live feed. 

[Crossy]

@Gulfsailor OK my fear about the CU wiring was unfounded, looks pretty OK.

 

Hopefully the PEA chap will score.

 

If I was doing it I would start by pulling ALL the neutrals, then with the breakers OFF (but main ON) start connecting them one by one until things trip, leave that one out and continue. At least then you would get the power back on.

 

CARE is required, I wouldn't be asking Wifey to do (but I have friends who are competent and in the area).

 

 

[Crossy]

Note, a N-E short may well cause the Safe-T-Cut to trip even with all the breakers off.

[Gulfsailor]

12 minutes ago, Crossy said:

@Gulfsailor OK my fear about the CU wiring was unfounded, looks pretty OK.

 

Hopefully the PEA chap will score.

 

If I was doing it I would start by pulling ALL the neutrals, then with the breakers OFF (but main ON) start connecting them one by one until things trip, leave that one out and continue. At least then you would get the power back on.

 

CARE is required, I wouldn't be asking Wifey to do (but I have friends who are competent and in the area).

 

 

That was my proposed plan of action as well, starting with the most likely culprit, the bottom blue one, which is from a dedicated wire on an own group I put in that goes to an outside water heater. However my gf couldn't get the screw for this  first neutral wire undone, so got pissed and now refuses to do anything else. We'll see what the PEA chap can do...

[Forkinhades]

Note, a N-E short may well cause the Safe-T-Cut to trip even with all the breakers off.

Sorry, but struggling with this, but TiT, with no current flowing how can this happen? I bow down to your superior quals of 2 degrees or more than me.

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[Forkinhades]

Xy I have sent a message to you, to discuss this, as it will be difficult for others to follow.
Thanks

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[lopburi3]

I have had it happen to me - a sump pump shorted to case and was grounded and it would trip RCCD with switch off and breaker tripped - had to remove pump wiring from circuit at on/off switch to restore that panel.  

[bankruatsteve]

Did they try the breaker off one-by-one test?

 

[Gulfsailor]

Update;

The PEA guys came, and according to my gf one of them waved some magic wand around. Then deducted something with the incoming electric was wrong. He climbed two separate poles on the road and after some sparks flying he climbed back down. Tested inside the house and all works normal again. (Apart from the blown up emergency light, an extension chord and some ceiling lights. This damage was obviously from a strong surge).

 

But I struggle to understand how anything upstream can affect my safe t cut. Could it be there was a short between live and earth at the pole, and due to the very wet ground, there was enough current flowing through the ground into my house via my earth (around 30meters away) and back out via the Neutral, resulting in a reversed earth leak? Does a safe t cut react to this reversed imbalance?

 

regardless, gf all happy again. Thanks for all the suggestion and help! And a big thank you to the PEA who so quickly came and found the problem apparently and fixed it.  

[RichCor]

15 minutes ago, Gulfsailor said:

Update;

The PEA guys came, and according to my gf one of them waved some magic wand around. Then deducted something with the incoming electric was wrong. He climbed two separate poles on the road and after some sparks flying he climbed back down. Tested inside the house and all works normal again.

[...]

But I struggle to understand how anything upstream can affect my safe t cut.

 

Possibly two phase wires, or a phase to neutral, were partially fused together on the pole, causing an Live over-voltage or a Neutral voltage imbalance condition.

 

You may want to do a quick inspect ALL of your wiring (at least the wiring you can see) and verify the insulation is still in good order and didn't melt in a flash-over event.

[Gulfsailor]

6 minutes ago, RichCor said:

 

Possibly two phase wires, or a phase to neutral, were partially fused together on the pole, causing an Live over-voltage or a Neutral voltage imbalance condition.

 

You may want to do a quick inspect ALL of your wiring (at least the wiring you can see) and verify the insulation is still in good order and didn't melt in a flash-over event.

Interesting. And explains why my gf commented a few days ago already that she thought she smelled something slightly burning in the house, but couldn't find the source. And now the different things blowing up / melting may then actually not have been from a surge, but from our Neutral becoming partly Live from another phase shorting with it on the pole. Ah well, we may never know. I'll check the wires as much as I can when I'm back. Until then I'll have no choice but to put my trust in the circuit breakers and safe t cut to keep the house from catching fire or someone getting electrocuted, regardless what happens upstream or downstream. 

[Forkinhades]

I have had it happen to me - a sump pump shorted to case and was grounded and it would trip RCCD with switch off and breaker tripped - had to remove pump wiring from circuit at on/off switch to restore that panel.  

Yes, but that is a single circuit right?

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[Forkinhades]

Update;
The PEA guys came, and according to my gf one of them waved some magic wand around. Then deducted something with the incoming electric was wrong. He climbed two separate poles on the road and after some sparks flying he climbed back down. Tested inside the house and all works normal again. (Apart from the blown up emergency light, an extension chord and some ceiling lights. This damage was obviously from a strong surge).
 
But I struggle to understand how anything upstream can affect my safe t cut. Could it be there was a short between live and earth at the pole, and due to the very wet ground, there was enough current flowing through the ground into my house via my earth (around 30meters away) and back out via the Neutral, resulting in a reversed earth leak? Does a safe t cut react to this reversed imbalance?
 
regardless, gf all happy again. Thanks for all the suggestion and help! And a big thank you to the PEA who so quickly came and found the problem apparently and fixed it.  

Nothing upstream will effect the safety-cut.

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[Crossy]

10 hours ago, Forkinhades said:

Sorry, but struggling with this, but TiT, with no current flowing how can this happen? I bow down to your superior quals of 2 degrees or more than me.

 

 

Nah, it's a phenomenon that confuses a lot of people. Think diverted neutral current.

 

The neutral is grounded at the transformer. By the time it gets to you it can be several volts above ground (Mr Ohm has a lot to answer for).

 

Now add a second ground (the N-E fault) on the cold side of the RCD.

 

A current roughly proportional to the neutral voltage and the ground resistance will flow through the neutral side of the sense coil.

 

The simple electromechanical (non electronic) RCD which most of us have will sense the differential (no current in the live) and trip.

 

EDIT Change the "would" to "should" in the previous post :) Although I'm confused as to what PEA actually did, possibly there was an overvoltage and our OP was switched to another phase. Sadly we're unlikely to ever find out. Great that it's all sorted.

[lopburi3]

8 hours ago, Forkinhades said:

Yes, but that is a single circuit right?

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It was the main breaker/RCCD on a Clipsal 7 breaker sub panel.  As I recall that shorted pump would not allow RCCD to be reset (even with all breakers off) until physically removed.  

[Gulfsailor]

A quick update as I am back home. Whatever caused the initial problem did result in quite  bit of damage. I haven't checked every appliance yet, but so far I found 4 broken extension cords, broken microwave, DVD player and emergency light. Except for the microwave they all show blown capacitors and some blown fuses. The inside of the extension cords showed a violent event took place! I'll see if I can repair some stuff by replacing the capacitors and fuses, but don't have high hopes. In the microwave the fuse is still fine though, and all small capacitors don't show anything visual. I haven't taken it apart far enough yet to check the high voltage capacitor. I guess if that one is busted it's better to just buy a new microwave, seeing the unit is about 10yrs old anyway. 

[Crossy]

It does sound like an over-voltage occurred, possibly due to an open neutral in the supply somewhere.

 

Microwaves scare me witless, the innards are more than capable of sending you into the next world even after it's been off for a while (notwithstanding bleeder resistors).

 

Entrust repair to a local.

[sandrabbit]

On ‎09‎/‎01‎/‎2017 at 5:15 AM, Crossy said:

 

Nah, it's a phenomenon that confuses a lot of people. Think diverted neutral current.

 

The neutral is grounded at the transformer. By the time it gets to you it can be several volts above ground (Mr Ohm has a lot to answer for).

 

Now add a second ground (the N-E fault) on the cold side of the RCD.

 

A current roughly proportional to the neutral voltage and the ground resistance will flow through the neutral side of the sense coil.

 

The simple electromechanical (non electronic) RCD which most of us have will sense the differential (no current in the live) and trip.

 

EDIT Change the "would" to "should" in the previous post :) Although I'm confused as to what PEA actually did, possibly there was an overvoltage and our OP was switched to another phase. Sadly we're unlikely to ever find out. Great that it's all sorted.

Possibly induced current/voltage as well. Even after more than 30 yrs in industry having worked in power generation etc the problems with grounding/earthing still surprise me. I've even had a shock off a cable which was disconnected at both ends, it must have been coiled around some live cables and acted like a current transformer.