step & touch potential

[majan]

Dear all,

Is the step & touch potential and related earthing also applicable for an indoor buil subsation ?

thanks

 

[dpc]

Basically, yes. The environment is different, but the risks are the same.

 

[cuky2000]

Yes, the step & touch potential and related earthing apply for indoor substations.

The most usual differences are:
a) Indoor substations are smaller in area than the outdoor one creating additional challenge to achieve the desire grid resistance.

b)That the allowable step and touch potential for outdoor substation is ussually larger than indoor substation.

For instance, indoor substations usually have concrete slab floor with low resistivity (50 to 90 Ohm.m) while outdoor substation usually have crushed rock with wet resistivity of 2000 to 3000 Ohm.m.

Shoes, paint coating or insulated mat may be considered in the analysis for improve the allowable step and touch potentials in indoor substations.

 

[jghrist]

The concrete slab will have will have steel rebar which will make it almost an equipotential surface. Unless the switchgear is GIS with very high fault currents possible through the enclosure, I don't think that you need to consider touch and step potentials inside the building. You should determine what the touch potentials are to the building itself for someone standing outside.

 

[davidbeach]

I'd put a copper mesh (6" x 6" or 12" x 12" grid) into the concrete floor slab, extending out 8 to 10 feet from the gear. That mesh should be bonded to the ground bus in the gear as well as the floor rebar. The rebar ties may or may not have a good electrical connection.