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PM5K:
It is not clear whether you are an electrician or not, and whether I should respond.
That you read 120 from one hot line to ground and thus possibly to neutral and 160 from the other hot to ground, and 277 from one hot to the other hot line implies two single phase waveforms that are 180 degrees out of phase. 120 plus 160 = 280 which is very close to 277. Your source does not appear to be a 3 phase 277/120 wye.
Normally a single phase 240/120 source is from a single center tapped secondary.
You should call the power company.
Go to your neighbor's home. Make voltage measurements there. If there is any 120 V outlet with with 160 V get the power company out immediately, and remove anything plugged into outlets with 160 V.
It would be better to make line to neutral measurements in the main panel, but your neighbors might not like you to do that.
You need to clarify your background .
Also you should go look at what the power company distribution transformer setup looks like. How many transformers, and what do the bushings and connections look like?
A 240/120 single phase system would usually (virtually always) have a single transformer with three output terminals, and for high voltage either two input insulated bushings, or one insulated bushing.
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