Monitor mains voltage for a short period of time

I would like to monitor the mains voltage of about AC 360 Vpeak for a couple of minutes.  I have a TDS 3054B oscilloscope and P6139A 10x voltage probe.  I would be grateful if someone advise me how to set up the measurement safely and correctly.  Thanks

It would be best to use a high voltage probe like P5202A with your TDS3054B for this purpose
https://www.tek.com/en/datasheet/high-voltage-differential-probes 
 

Hello,

To measure the AC 360 Vpeak mains voltage safely and accurately, you can follow these steps:

Check the measuring device's features: You already have a TDS 3054B oscilloscope and a P6139A 10x voltage probe. This is suitable for measuring the AC 360 Vpeak voltage, because this oscilloscope has a maximum voltage measurement range of 300V and the probe has a 10x division ratio.

Setting up the probe: Connect the P6139A probe to the measuring channel of the oscilloscope. Make sure that the probe is set to the correct 10x division ratio on the oscilloscope.

Proceed to measure: Connect the positive end of the probe to the point to be measured on the AC 360 Vpeak mains. Make sure that the ground connector is securely connected.

Adjust the oscilloscope settings: Adjust the voltage scale and sweep time on the oscilloscope to clearly observe the voltage wave. You can start with a scale of 500V and a sweep time of 50ms/div, then adjust accordingly https://www.tek.com/en/datasheet/high-voltage-differential-probes time calculator.

Observation and recording: Monitor the voltage wave for a few minutes and record important parameters such as peak value, frequency, waveform, etc.