25
Determining ‘Step’ potential
‘Step’ potential is the potential difference a person
would experience between his feet as he walked across
the ground in which a fault current was flowing.
Firmly connect the instrument as follows :-
1)
Terminal 'C1' to the substation earth.
2)
Terminal ' C2' to the Current spike inserted in the
ground some distance away.
3)
Firmly connect the 'P1' and 'P2' terminals to test
spikes inserted in the ground 1 metre apart, (or the
length of a step) at positions A and B respectively.
A is nearest to the substation earth.
4)
Press the Te s t push, and take a reading in
the normal way.
Record the resistance indicated. This is the effective
resistance across the positions A and B, as seen by the
test current.
The maximum value of the current that would flow in
the earth when a fault to earth occurred at the
substation must again be known. From Ohms Law the
‘Step potential’ can be calculated.
Determining ‘Step’ potential
Содержание DET2/2
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