EMI line conditioner (Satic super duty) not being able to keep up

[GuruLal]

I've got 400Amp service at my home. I've got some THD (total harmonics distortion) issues in my home coming in from my variable heat pumps etc. One of the hypothesis behind why the line conditioner is not able to keep up is the presence of ground loop currents, which I've mitigated for the most part, except for a tiny bit of ground current that seems to be coming from utility side transformer ( ~ 40 mA or so) appears to come through the neutral wire and since that neutral is bonded to my ground, it then feeds into my ground wire. What is the best/cheapest way to get rid of this foreign current source from contaminating my house ground and creating field around my living space?

Aneil

 

[don_resqcapt19]

It is not possible in a code compliant way. The neutral is bonded at multiple points on the line side of your service, both at the primary and secondary voltage levels. Every connection to earth results in parallel path for neutral current.

 

[wwhitney]

It is not possible in a code compliant way.

Not possible to keep utility neutral current off all parts of the premises wiring system, but can't you sometimes isolate it to certain parts so that the rest is free of utility neutral current?

I.e. if there's a point on the wiring system where the utility source is on one side and only loads are on the other; the EGC wiring on each side only interconnects at that point and not through a parallel path; and there are no earth connections to the EGC on the load side of that point, then there should be no utility neutral current on the EGC on the load side of that point.

I imagine the hard part is that certain loads by their nature would generally require an earth-EGC connection. E.g. a metal light post in the yard. Or if you have metal water piping, any electrical water equipment like water heaters. So you might need to design the whole premises wiring system with the above goal in mind.

Cheers, Wayne

 

[GuruLal]

Not possible to keep utility neutral current off all parts of the premises wiring system, but can't you sometimes isolate it to certain parts so that the rest is free of utility neutral current?

I.e. if there's a point on the wiring system where the utility source is on one side and only loads are on the other; the EGC wiring on each side only interconnects at that point and not through a parallel path; and there are no earth connections to the EGC on the load side of that point, then there should be no utility neutral current on the EGC on the load side of that point.

I imagine the hard part is that certain loads by their nature would generally require an earth-EGC connection. E.g. a metal light post in the yard. Or if you have metal water piping, any electrical water equipment like water heaters. So you might need to design the whole premises wiring system with the above goal in mind.

Cheers, Wayne

Please explain a little bit more with simplicity. How do you isolate "certain parts"?

 

[wwhitney]

Please explain a little bit more with simplicity.

The EGC system is not intended to carry current during normal operations. But it may be earthed at multiple points throughout the premises. That puts a path in the EGC wiring in parallel with a path in the earth. When the earth is carrying some utility primary or secondary neutral current, then the EGC system will share in that current as usual with parallel paths.

So imagine you have a schematic of all the premises wiring, every conductor (including non-wire type EGCs like metal conduit and metal enclosures) and every connection, and it shows every connection to earth anywhere for any reason by any means. And rather than spreading the earth connections throughout the schematic with little ground symbols everywhere, you just have the earth as a single point on the schematic, so all earth connections extend all the way to that point.

Then if you can draw a circle around part of the schematic, not including the earth point, and there is only one EGC connection coming out of the circle, and the system is wired correctly, there will be no utility neutral current on the the EGC system within that circle. Because with the system properly wired, there will be no neutral-EGC bonds within the circle; and with only one EGC connection coming out of the circle, it will be the intentional one. There will be no earth connections within the circle, as that would show up as a second EGC connection coming out of the circle, per my stipulation that earth is represented as a single point on the schematic.

In the above I am using EGC system a bit loosely; it should include any bonding jumpers or GECs for my statement about circle drawing to be true.

Cheers, Wayne

 

[ptonsparky]

I've got 400Amp service at my home. I've got some THD (total harmonics distortion) issues in my home coming in from my variable heat pumps etc. One of the hypothesis behind why the line conditioner is not able to keep up is the presence of ground loop currents, which I've mitigated for the most part, except for a tiny bit of ground current that seems to be coming from utility side transformer ( ~ 40 mA or so) appears to come through the neutral wire and since that neutral is bonded to my ground, it then feeds into my ground wire. What is the best/cheapest way to get rid of this foreign current source from contaminating my house ground and creating field around my living space?

Aneil

What issues are you having?

 

[TwoBlocked]

Fine folks. Here's a question I've wondered about and could be the OP's dilemma. Is it true that when you are sharing the pole transformer with neighbors, and everyone is grounding to municipal water pipes; then your neighbor's neutral current can have a parallel path back to the pole transformer, through his bonding jumper, through his grounding, through the water piping, THROUGH YOUR GROUNDING, through your bonding jumper and through your neutral to the shared pole transformer?

 

[ptonsparky]

Fine folks. Here's a question I've wondered about and could be the OP's dilemma. Is it true that when you are sharing the pole transformer with neighbors, and everyone is grounding to municipal water pipes; then your neighbor's neutral current can have a parallel path back to the pole transformer, through his bonding jumper, through his grounding, through the water piping, THROUGH YOUR GROUNDING, through your bonding jumper and through your neutral to the shared pole transformer?

Yup. Current flows on all paths, not just the one(s) of least resistance.

 

[GoldDigger]

A different but related problem is seen when the Neutral to Earth Voltage (NEV) is substantially higher, in the multiple volt range.

When POCO's metallic primary neutral is compromised, the result can be a significant amount of primary current flowing through the earth electrode at each pole or other grounding point in the Multiply Grounded Neutral (MGN) network. Because the source of the primary current is at high voltage, the resistance of each earth electrode will not significantly change the current, but will result in a significant voltage offset between the earth electrode and "remote earth" where the current density is low.

The result for each customer is that the POCO neutral, connected at the transformer secondary to the same earth electrode is also offset from remote earth by as much as tens of volts. This can cause unpleasant or even hazardous voltages between EGC-connected appliance surfaces and direct earth grounds such as metallic water or drain pipes.

Only POCO can fully correct this situation by restoring the competence of their metallic neutral. But, especially in rural areas with long primary runs, they may be unwilling to immediately go to the necessary expense (since from their point of view the system still "works".)

From the customer side, one possibility is to install a whole house isolation transformer with no bond between the two neutrals (a separately derived system). If the input neutral to the transformer is bonded to the local earth grounding system but the secondary neutral is, the result will be that no stray POCO primary current will flow through the local earth grounding system.

A more affordable solution, often used at farms, and in particular dairy farms where stray voltages can drastically cut milk production, is the neutral isolator. This is installed by POCO at their pole and breaks the connection between the primary neutral (still connected to the pole earth electrode) and the secondary neutral. The result is that the only earth connection for the secondary neutral is the bond at the customer service. At this point you may be asking why you need a substantial device just to NOT make a connection. So there is more to the neutral isolator than just that. In particular a fault on the POCO side which applies primary voltage to the secondary side will result in that primary voltage trying to return through the customer's earth ground system (GES). This could be extremely dangerous because a high voltage can develop between the customer EGC and remote earth. The neutral isolator deals with this event by sensing the higher than usual offset between primary and secondary neutral and restoring the metallic connection between two neutrals, carrying the fault current. The threshold of the neutral isolator is set by POCO, and usually ranges between a maximum of about 40V and a minimum of about 10 volts. Neutral isolators are not generally used for residential consumers, where the only recognized solution for high Netural Earth Voltage (NEV) is for POCO to fix their problem.

 

[wwhitney]

This can cause unpleasant or even hazardous voltages between EGC-connected appliance surfaces and direct earth grounds such as metallic water or drain pipes.

Presumably for a residential water pipe system that was entirely metallic, this would require earth connections at two or more spatially separated points. As the metallic water entrance will be connected to the GEC, which is connected to the EGC and neutral at the electrical service. So at that point the metallic water pipe to EGC potential difference should only be that which is attributable to POCO neutral current flowing through the water pipe and the service neutral.

Cheers, Wayne

 

[ramsy]

A more affordable solution, often used at farms, and in particular dairy farms where stray voltages can drastically cut milk production, is the neutral isolator. This is installed by POCO at their pole and breaks the connection between the primary neutral

Thanks for sharing about neutral isolators.

 

[winnie]

Presumably for a residential water pipe system that was entirely metallic, this would require earth connections at two or more spatially separated points. As the metallic water entrance will be connected to the GEC, which is connected to the EGC and neutral at the electrical service. So at that point the metallic water pipe to EGC potential difference should only be that which is attributable to POCO neutral current flowing through the water pipe and the service neutral.

Cheers, Wayne

Very often, cast iron drain pipes don't get bonded to the supply pipes, and can provide the isolated ground.

I've also seen reports of people getting shocked from hose bibs, where all of the plumbing is bonded to the ground rods and neutral, but their bare feet on the ground provides the second earth 'electrode'.

Jon