Multiple conductors from source neutral point can be ok (HRG applications)

[MechEdetour]

Sorry for the click-bait-ish title, but it is true.

Most (all?) HRG systems that have resistor health monitoring, monitor the neutral circuit by installing a conductor "in parallel" with the resistor. I say with the resistor, but in reality the connection is always recommended to be as close to the source neutral point as possible so that the entire neutral circuit is monitored, and not just the resistor assembly itself.

I won't to get into the weeds of resistor health monitoring, but in the example below, one of the devices that's used to monitor the neutral circuit (and NGR - neutral ground resistor) is installed in parallel as explained above. It has very high impedance (20k ohm), so the current flowing through it at any time would be on the order of milliamps. Never ZERO of course, but damn near close.


I made this thread without really having a solid question other than: how are we able to skirt the fact that we have effectively two current paths to the source with this method of resistor health monitoring? Maybe I am playing devil's advocate here since it isn't just a wire - there is a device that is installed for a very specific purpose. Is there verbiage in any code or standard that would specifically address this type of installation? I haven't come across anything anywhere.

Maybe it's a non-issue and I'm just trying to make a mountain out of a mole hill. If so, I'll shut up and move on. I just couldn't help but wonder if anyone else asked themselves the same thing.

 

[jim dungar]

Maybe it's a non-issue and I'm just trying to make a mountain out of a mole hill

Non issue.
As you pointed out, this is a separate device not a parallel path for neutral/ground current.

I have never seem one of these items. Does this resistor health check also perform ground fault detection?

 

[MechEdetour]

Non issue.
As you pointed out, this is a separate device not a parallel path for neutral/ground current.

I have never seem one of these items. Does this resistor health check also perform ground fault detection?

Not this device specifically, but the total package yes. The complete monitoring package would consist of a CT, HRG relay (the brains), and the health monitoring device I spoke to above (aka the sensing resistor).

Ground fault detection and resistor fault detection (both open and shorted) are covered with the package. The sensing resistor only comes into play for the resistor detection part.