I am currently involved in testing the power quality for a Hitachi TEM (transmission electron microscope). There have been intermittent issues for the past several months that have stumped the techs and as a result a request was made to test the quality of the supply power.

The only test I conducted thus far was a voltage test on the secondary of the Hammond step down transformer (210V:100V). Using a Fluke 1735 Power Logger we connected the meter for Single Phase + Neutral. The meter was left to record for one week. Once the time was up the meter was disconnected and the data was downloaded. There were 5 events recorded where the voltage dropped significantly for a duration of one cycle (17ms). After showing this information to the tech he was wondering if I could capture any signs of voltage on the ground conductor. He gave a brief explanation and it sounded fairly straight forward. Now, I am wondering how to set-up the Fluke Power Logger to test for this potential phenomena.

I started researching the subject of finding voltage on the ground. I am quite certain that he wants me to verify whether or not neutral to ground voltages exist. The Hammond transformer is obviously isolating the secondary from the building's power supply but the method of grounding is one that I am not entirely familiar with and possibly misunderstand. In this installation an isolated ground is brought from the building ground rod to the transformer secondary and connects to one phase. This is very different from the isolation transformers I've seen elsewhere and the one I use at home.

If anyone is familiar with the Fluke 1735 Power Logger and this form of isolation transformer's connections I would appreciate feedback regarding how to use the meter to record Neutral to Ground voltages on the secondary. I do not see any information regarding this that comes with the Fluke. I put together a diagram to give a visual idea of what I am dealing with. Thanks.

[Linked Image from i63.tinypic.com]

A malfunction at the junction