220V-240V EUROPEAN

[fifty60]

I've seen equipment designed at these voltages intended for use in the European Union. The 220V-240V is part of a 380-415V Y supply, so the 220-240V is derived from a hot wire and a ground. The equipment had fuses for both legs of all of the branch circuits.

The neutral leg should be unfused right, since the 220-240V is derived from a hot and a neutral? Would it be possible that the neutral is not grounded? I know the NEC is not valid for EU, but not fusing grounded conductors must be a universal law of some kind...

 

[Besoeker]

I've seen equipment designed at these voltages intended for use in the European Union. The 220V-240V is part of a 380-415V Y supply, so the 220-240V is derived from a hot wire and a ground. The equipment had fuses for both legs of all of the branch circuits.

The neutral leg should be unfused right, since the 220-240V is derived from a hot and a neutral? Would it be possible that the neutral is not grounded? I know the NEC is not valid for EU, but not fusing grounded conductors must be a universal law of some kind...

The 230V is derived from live to neutral. For distribution, the neutral is normally earthed at the distribution transformer.
Unless pikies have stolen the copper.

 

[fifty60]

But then the millecents can lay some tolchocks on the malchiks if they ever viddie them in the act~~~Derived from "A Clockwork Orange---Book was based in 1960's UK

Is it common to see imported equipment with 2 branch fuses for 220-240V systems? The neutral, grounded at the supply, should not be fused right? I'm looking at a piece of equipment right now that has 2 branch fuses.

The neutral is not the only return path to ground for the phase right? On the negative portion of the AC the hot phase will will be carrying current back to ground...but wait, the hot phase is not grounded. I guess I am a little confused by what is actually going on here and what happens if the fuse on the grounded neutral blows.

I've been trying to think through the grounding of a secondary phase of a transformer. With no ground, the voltage is measured across the secondary coils, but is not referenced to grounds. Still, the voltage across the secondary is the secondary voltage. If a ground fault occurs on the secondary, and the secondary is not grounded to begin with, no extra current will flow because there is no circuit.

If the secondary is grounded, and a ground fault occurs, then there is a circuit and enough current will be drawn to blow the OCPD.

Can someone please describe what is going on grounding wise with the incoming power supply? If a single ground fault occurs on phase A, then high current is generated...where is the second ground to make the circuit on a single phase?

 

[Besoeker]

.

The neutral is not the only return path to ground for the phase right?

There is no return path to ground.
Current flows from live to neutral via the load. That's the voltage that drives it.
If there is a live to earth (ground) fault, the ground gives a return path to the neutral.

 

[GoldDigger]

Is it common to see imported equipment with 2 branch fuses for 220-240V systems? The neutral, grounded at the supply, should not be fused right? I'm looking at a piece of equipment right now that has 2 branch fuses.

If the equipment manufacturer expects it to be connected via non-polarized plugs or miswired in terms of which conductor is grounded, I can see a motive for fusing both inside the equipment.
But that potentially creates an unsafe situation in the event of a fault (the fuse in the grounded conductor opens but not the fuse in the hot conductor, for example) and is not allowed by the NEC.

 

[fifty60]

I think perhaps i try to anyalze AC using DC thinking. With DC, you need the path to ground. Current flows through the load to ground. With AC, there is not a return to ground.

With a hot and a grounded neutral, if there is a ground fault then the load is between the ground fault and the conductors leading to the main ground connections? Since the resistance is only that of the conductors between the fault and ground, there a lot of admittance and a lot of current flows.

What about between 2 hot phases and a single ground fault occurs...does a circuit need to connections to ground in order to create an overcurrent?

I've been thinking a lot about the secondary of the transformer...and how it is grounded and how the current flows through the secondary, but just can't seem to put it all together across every situation. Please feel free to correct or expand upon the above!

 

[GoldDigger]

I think perhaps i try to anyalze AC using DC thinking. With DC, you need the path to ground. Current flows through the load to ground. With AC, there is not a return to ground.

!

In a DC circuit, you normally have two wires, one plus and one minus and the minus or the plus is often also connected to ground.
In an automotive environment, you still have a two wire circuit. But the second "wire" is actually the metal of the vehicle and frame. Whether or not the frame is grounded makes no difference at all.
If the second connection of the DC circuit were really only an earth ground, the resistance would be so high that nothing would work (at least in a 12V system.)

 

[fifty60]

AC system, for example, I have a motor. If the motor enclosure is not grounded, then a single ground fault inside the enclosure will most likely not be noticed until someone touches the enclosure and creates a second path to ground. If the enclosure is grounded, then the the OCPD will trip when there is a single ground fault.

I have the enclosure grounded, there is a ground fault, i have a circuit consisting of 2 connection points to ground and the conductors in between. There is voltage across the wires from my power system. There is hi admittance between between the 2 grounded points, and the voltage will pull electrons from ground and return them to ground through the high admittance.

With only one wire to ground, there is not a low resistance return path to ground so no current flows...

I think ground faults are much more intuitive if you think in terms of Admittance rather than Resistance...But all of the key elements have to be in place, the voltage source, and 2 connections to ground...

the voltage is not the source is not the source of electron flow, but the actual enclosure is the source of the electrons, but I am not able to understand the voltage difference between the 2 ground points since they are both zero potential. How does current flow from cround connection to ground connection if there is not a potential difference. I believe the answer will have something to do with both ground points actually being a single point...

 

[GoldDigger]

AC system, for example, I have a motor. If the motor enclosure is not grounded, then a single ground fault inside the enclosure will most likely not be noticed until someone touches the enclosure and creates a second path to ground. If the enclosure is grounded, then the the OCPD will trip when there is a single ground fault.

I have the enclosure grounded, there is a ground fault, i have a circuit consisting of 2 connection points to ground and the conductors in between. There is voltage across the wires from my power system. There is hi admittance between between the 2 grounded points, and the voltage will pull electrons from ground and return them to ground through the high admittance.

With only one wire to ground, there is not a low resistance return path to ground so no current flows...

I think ground faults are much more intuitive if you think in terms of Admittance rather than Resistance...But all of the key elements have to be in place, the voltage source, and 2 connections to ground...

the voltage is not the source is not the source of electron flow, but the actual enclosure is the source of the electrons, but I am not able to understand the voltage difference between the 2 ground points since they are both zero potential. How does current flow from cround connection to ground connection if there is not a potential difference. I believe the answer will have something to do with both ground points actually being a single point...

I think one thing that you are missing is that although "the earth" is all at the same potential, simply putting an electrode into the earth will not hold the electrode at that potential if current is flowing. Instead there will be a steady (but not linear) change in voltage in the dirt as you move away from the electrode. If you have two electrodes one mile apart and a 10A current flowing, it will be impossible to measure the resulting potential drop through the dirt near the midpoint, but it will be there. Near either electrode you may see 250 volt or greater offsets from "ground".

If you put a voltmeter between the two ground rods, you will measure a voltage difference equal to the current times the sum of the resistances of the two ground electrodes.
Going back to the automotive DC analogy, the undisturbed earth (no current flowing) is all at the same potential. The undisturbed frame of the car is all at one potential. But it is much easier to make a low resistance connection to the frame than it is to make a low resistance connection to "the earth".

 

[tek9]

A lot of old british installations had fused neutrals but now the neutral is unfused,earthed at the tranny and usually at the customers installation.

 

[Besoeker]

A lot of old british installations had fused neutrals but now the neutral is unfused,earthed at the tranny and usually at the customers installation.

I'm British. Have been all my life.
Never seen a fused neutral. Nor a distribution neutral earthed anywhere other than at the distribution transformer.
But, hey, ignorant Brit strikes again.

 

[GoldDigger]

I'm British. Have been all my life.
Never seen a fused neutral. Nor a distribution neutral earthed anywhere other than at the distribution transformer.
But, hey, ignorant Brit strikes again.

The British installations that he refers to may have been installed by the British in the colonies rather than in the UK itself?

 

[mbrooke]

Fused neutral

Fused neutral

Normally in the EU union the neutral is not fused since the source is 240/415Y, with the neutral grounded solidly once at the source. The fusing may be done for several reasons: 1) the manufacturer may have been aware that the device would be used outside of the EU where 240 is a phase to phase voltage like Canada and the states.

2) older legacy power supplies in France, Spain ect were 127/220Y or 139/240Y, so any equipment would be connected phase to phase here, the neutral simply isnt drawn to the load or used.


3) Most electrical equipment intended for use in Norway has both legs fused. The reason for this is (except for the newest installs) is that Norway uses an IT system. IT is the IEC term for ungrounded. Most of Norway uses a 230 volt ungrounded system or 690 volt in the case of industrial. They are nearly identical to our 240 and 480 delta systems used in the states. The transformer is either delta or a wye where the XO is left ungrounded or grounded through a surge suppressor that keeps the XO isolated from ground unless a surge takes place such as lightning or a High voltage conductor/winding failing into the low voltage. Under normal conditions it functions exactly as the 240 volt ungrounded delta system would in the states. Hence just like in the NEC, both legs need to be fused even though they are only 230 volts and not 400.

Of note, where circuit breakers are used in Europe such as RCDs (GFCIs) the hot and neutral are broken simultaneously for safety reasons regardless of voltage or grounding . However, you mention fuses, in that case I would think that if your supply is a phase to neutral type deal one of those fuses would need to be jumpered.

 

[fifty60]

So it would be different with circuit breakers than for individual fuses? I thought the idea was to only break ungrounded conductors regardless of the type of OCPD....

 

[Rick Christopherson]

The equipment had fuses for both legs of all of the branch circuits.

First off, there is a difference between circuit protection inside the equipment versus the branch circuit feeding it. It is not uncommon to find equipment with internal OCPD on both lines because it may not be known where that equipment gets used, and whether one of the conductors will be grounded.

The requirements of the controls inside of a piece of equipment are not the same as the requirements of the circuit supplying it. For example, I am pretty sure there is no requirement to disconnect all non-grounded conductors to control an internal circuit, but that is something required for the supply circuit. While not common, technically all it takes to control a single-phase motor is to open one side of the circuit.

Furthermore, and I am NOT an expert on code, but I believe that even the NEC permits breaking the grounded conductor as long as it simultaneously opens all other current carrying conductors. (240.22). Obviously this won't be true with fuses, but again, this appears to be internal OCPD and not branch circuit OCPD.

 

[mbrooke]

So it would be different with circuit breakers than for individual fuses? I thought the idea was to only break ungrounded conductors regardless of the type of OCPD....

Yes, it is different with breakers since you simultaneously break both hots and the neutral. In a fuse situation both fuses are independent of each other, which might cause one to blow where the other one stays intact. In cases like this, I do not recommend fusing the neutral, nor does the NEC.


You don't have to break just the hot, you can break the neutral as long as you do the hot at the same time. Often it adds a layer of safety. In some cases it is even required, like in the US NEC with gas pumps. In the case of gas pumps by breaking the neutral along with the hot you eliminate a potential voltage rise, ie the neutral at the gas pump might be several volts above ground which is something that happens in all electrical installations. The elevated voltage can cause a very small spark should the neutral touch a good ground. The micro spark and few volts are not a direct hazard to people, but may ignite a fuel spill.

In the case of the EU, its done primarily in the event should a neutral connection fail feeding a building or sub panel. A broken neutral will rise to a dangerous voltage if load is connected to it as with any install. If this takes place on a feeder for a sub panel with line to neutral loads all the branch neutrals will be above ground potential. By breaking both hot and neut at the branch breaker the risk of an energized neutral is eliminated. Switching the hot does not eliminate that risk should something go wrong.

 

[GoldDigger]

In the case of the EU, its done primarily in the event should a neutral connection fail feeding a building or sub panel. A broken neutral will rise to a dangerous voltage if load is connected to it as with any install. If this takes place on a feeder for a sub panel with line to neutral loads all the branch neutrals will be above ground potential. By breaking both hot and neut at the branch breaker the risk of an energized neutral is eliminated. Switching the hot does not eliminate that risk should something go wrong.

If you view the recently posted Mike Holt video on lost neutrals, you will see that even if the loss of the neutral does not unbalance the leg voltages enough to cause immediate load damage (mainly because the ground-neutral bond is very good or the loads over the whole transformer secondary are very well balanced.
But the neutral will be offset from ground voltage far enough that random non-deliberate connections between the EGC and real earth ground (structural or piping) can actually form a low voltage arc or glowing connection that can start a fire inside a wall.

The surprise for the fire fighters was that removing the meter for just the affected residence left the ignition source active with no change at all in intensity. Cutting the neutral to the building or de-energizing the shared POCO transformer removed the current source (depending on where the neutral was lost.)

 

[mbrooke]

If you view the recently posted Mike Holt video on lost neutrals, you will see that even if the loss of the neutral does not unbalance the leg voltages enough to cause immediate load damage (mainly because the ground-neutral bond is very good or the loads over the whole transformer secondary are very well balanced.
But the neutral will be offset from ground voltage far enough that random non-deliberate connections between the EGC and real earth ground (structural or piping) can actually form a low voltage arc or glowing connection that can start a fire inside a wall.

The surprise for the fire fighters was that removing the meter for just the affected residence left the ignition source active with no change at all in intensity. Cutting the neutral to the building or de-energizing the shared POCO transformer removed the current source (depending on where the neutral was lost.)

True, some really ugly things can happen with a lost neutral. Any time current runs uncontrolled on metal frames or the like the risk of arcing or heating goes way up. Hence one reason why the EU argues for the use of RCDs. Should a neutral become grounded anywhere or a hot develops a ground fault that doesn't draw enough current to trip a breaker but enough to start a fire it trips the RCD. They are usually set to trip at 30ma. Unfortunately they still don't help should the main neutral to the building become disconnected.



BTW, Do you have a link to the video?

 

[Jraef]

Here's how it was explained to me years ago when i worked for a German company here in the US, where we made control systems for OEMs sending equipment back to Europe.

In the IEC world, there are different rules for different types of "Earthing Systems", which refer to how the Neutral, Earth and "Protected Earth" (PE) conductors are run and connected. There are some similarities to US systems, but they are not the same.

One issue is that there were different methods of enforcement of standards that existed prior to the "harmonization" that took place in 1992, leaving some countries with existing wiring that may or may not conform to standards in other countries at that time. One of THOSE issues has to do with identification of the Neutral conductor in single phase services. Italy and Spain (for the most part) had lax enforcement of that issue, meaning the wall outlets can have the N on the right or the left, you never know, and the plugs made no differentiation, they could be plugged in either way. The same held true even in hard wired single phase installations. So since 1992, an IEC standard (IEC 950) required that if equipment is intended to be connected to a single phase service anywhere in Europe, BOTH lines need to be protected (fuses or CBs) because you will not know which one is Line or Neutral.

 

[Besoeker]

Here's how it was explained to me years ago when i worked for a German company here in the US, where we made control systems for OEMs sending equipment back to Europe.

In the IEC world, there are different rules for different types of "Earthing Systems", which refer to how the Neutral, Earth and "Protected Earth" (PE) conductors are run and connected. There are some similarities to US systems, but they are not the same.

One issue is that there were different methods of enforcement of standards that existed prior to the "harmonization" that took place in 1992, leaving some countries with existing wiring that may or may not conform to standards in other countries at that time. One of THOSE issues has to do with identification of the Neutral conductor in single phase services. Italy and Spain (for the most part) had lax enforcement of that issue, meaning the wall outlets can have the N on the right or the left, you never know, and the plugs made no differentiation, they could be plugged in either way. The same held true even in hard wired single phase installations. So since 1992, an IEC standard (IEC 950) required that if equipment is intended to be connected to a single phase service anywhere in Europe, BOTH lines need to be protected (fuses or CBs) because you will not know which one is Line or Neutral.

Neutrals are not fused in UK.
And there is no ambiguity about which is live and which is neutral.