Phase Rotation Meter

[HighPotter]

Is this possible? CustomersElectrical service is to be replaced.

One type of rotation meter is used to mark rotation on the 480v 3 phase service. Phasing is marked " blue-white-red " Clockwise rotation

After customer service is replaced, the service is energized to the meter and checked with ANOTHER(different) phase rotation meter. Meter is hooked up "blue-white-red", but rotation is Counterclockwise.

The 2 primary leads to transformers were swapped, same rotation meter was hooked up " blue-white-red", and rotation was Clockwise. The customer then energized his service at the main.

It was later found out that the rotation was backwards.

Can 2 different rotation meters give you different rotation, even if you hook the "colored" leads up the same?


HP

 

[alehman]

Yes. Always use the same meter when checking rotation.
See thread238-143007

 

[waross]

My first thought is "The second Meter is reversed internally."
My second thought is "The human factor."

My last rotation meter experience. I was called in to trouble shoot an Automatic Transfer Switch. It worked on the Generator but not on the mains. The ATS had Phase Failure and Rotation Protection. Pretty simple, the transformers had been replaced and the phasing was backwards. The manager told me, "That can't be. The engineer had a rotation meter and checked it."
The Automatic Transfer Switch uses two magnetic contactors side by side. The connections on the load side are made with buss bars. The phasing on one contactor is ABC, and on the other contactor CBA. I surmise that the instead of connecting the Phase meter in one spot (Distribution Panel, or Load side of the Transfer Contactors, he checked the incommimg mains rotation at the mains contactor and then checked the generator at the generator contactor, without noticing that 8 inches away the connections were reversed.
The point is, were the phase checks done by the same person at the same place in the circuit? Was one check done at the panel and the other check done at the meter base, where the phase arrangement was not necessarily the same?
yours

 

[HighPotter]

Thanks for your responses. In this case, the Troubleman marked the rotation prior to deenergizing the service, and then a different meter was used when checking before renergizing.

Next time, the same meter will be used, regardless.

HP

 

[dpc]

There was an earlier thread that discussed phase rotation meters in some detail.

One source of possible confusion is that electrical engineers generally associated positive phase rotation with counterclockwise phasor rotation - this is the IEEE convention.

Many phase rotation meters rotate clockwise when connected with positive phase rotation.

Good idea to use the same meter for "before" and "after".