Buzzing a circuit - story to experts and Engineers?

[230kv]

Buzzing a circuit through the use of a live line tool is one of the methods performed by linemen to ensure that features being worked on have been isolated.

This process touching the metal cap at the end of a live line tool to the conductor.

If the voltage is high enough to produce a buzzing sound, the circuit is considered energized.

If the buzz is not heard, the line is to be considered isolated.

Last week one of lineman crew get outage for 115kv line to do some de energized maintenance
By mistake they went to life circuit and test the line by touching the metal cap at the end of a live line tool to the conductor.
then no any buzzing sound herring.

Then they install personal ground ....the line get trip with big arc!!
The important thing to know that, this line designed as 400 kv quadruple conductor ACAR , but temporary energized as 115 kv

Did this the reason to not hearing any buzzing sound?
Did there is any standard to testing the line for this case?
Thanks