Corner grounded delta

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winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Another thought.. was it really a corner ground or was it an 'ungrounded' that had a fault, an improper, accidental bond at some point in the system. What has been removed since your prior checks?

I believe that this is a key question that should be amplified. Is this system supposed to be corner grounded, and has lost the bond, or was the system supposed to be ungrounded and had a ground fault making it appear corner grounded.

1) Does the system have 'ground detectors'? This might be as simple as a set of 3 lights arranged so that a ground fault on a phase will put one light out. Ground detectors are required for ungrounded systems.

2) Do you have a 'low impedance' meter that can be used to make voltage measurements? An ungrounded system that is balanced will show pretty balanced line-ground voltages, but if you test using a low impedance volt meter the line-ground voltage will drop significantly. Testing with both high and low impedance volt meters will help you diagnose this issue.

-Jon
 
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