480V 2000A Bus - Hipot

[jts1976]

Looking to hipot a run of 480V 2000A busduct, approx 200'. We don't typically hipot LV items. Trying to verify the capacity of the instrument to test the bus. Was going to connect 120V to the bus and meter milliamps using a digital multi meter. I don't know the capacitance of the DUT, and am almost positive that this instrument can't handle - it's a Megger 230425. Planning on using the formula: hipot test voltage (2000VAC )/leakage current test voltage (120VAC) * leakage current (measured in mA using the DMM) to determine the hipot current, and thereby select an instrument. The 2000VAC test voltage is based on the rule of thumb 2x RMS line voltage + 1000. NETA table 100.17 shows 1600VAC max test voltage for Nonsegregated Phase-type bus with a rated kV of 635 - it's the closest thing in the book I could find to the 480 bus that we're dealing with. Any feedback would be greatly appreciated!!

[SecondGen]

Looking to hipot a run of 480V 2000A busduct, approx 200'. We don't typically hipot LV items. Trying to verify the capacity of the instrument to test the bus. Was going to connect 120V to the bus and meter milliamps using a digital multi meter. I don't know the capacitance of the DUT, and am almost positive that this instrument can't handle - it's a Megger 230425. Planning on using the formula: hipot test voltage (2000VAC )/leakage current test voltage (120VAC) * leakage current (measured in mA using the DMM) to determine the hipot current, and thereby select an instrument. The 2000VAC test voltage is based on the rule of thumb 2x RMS line voltage + 1000. NETA table 100.17 shows 1600VAC max test voltage for Nonsegregated Phase-type bus with a rated kV of 635 - it's the closest thing in the book I could find to the 480 bus that we're dealing with. Any feedback would be greatly appreciated!!

Looking at the specs, your test set is capable of 12mA @ 4kVAC? You only need 1.6kV for the test, if you have the ability to access the equipment for the DMM test, why not just give the Megger test set a shot? If it doesn't work, try your calculation. Just bring up the voltage test really slow and make sure the current doesn't jump too high in the process, I think its worth a shot.

Megger 230425 specs:
Applied Test Voltage 0 to 4 kV, 0 to 5 kVdc
Adjustable Leakage Current Trip Level AC: 0.3 to 12 mA, DC: 0.43 to 17 mA

[jts1976]

Looking at the specs, your test set is capable of 12mA @ 4kVAC? You only need 1.6kV for the test, if you have the ability to access the equipment for the DMM test, why not just give the Megger test set a shot? If it doesn't work, try your calculation. Just bring up the voltage test really slow and make sure the current doesn't jump too high in the process, I think its worth a shot.

Megger 230425 specs:
Applied Test Voltage 0 to 4 kV, 0 to 5 kVdc
Adjustable Leakage Current Trip Level AC: 0.3 to 12 mA, DC: 0.43 to 17 mA


Thanks SecondGen. We'll be onsite tomorrow, and will megger to make sure we're getting a good reading before hipot testing. Standard insulation resistance readings from GE for LV spectra series bus is 1 Mega ohm/100' (run is approx 200'). Here's what I got from GE today:

The test parameters should be 1000vdc (phase to phase and phase to ground). When conducting, this test ensure the Busway has NO connection or contact with any potential power source.
The standard for megger readings for all busway manufactured in the US is one (1) megohm per 100 ft. The required minimum reading per 100 ft. is published In NEMA Standard BU1.1 and published by GE in the Spectra Seriesâ„¢ busway Installation Instruction DEH-40087.

I think we'll take your advice and hit it with the 230425 to see what happens. . .:D