# PD 55

Insulating Mat

In electrical engineering, Earth Potential Rise (EPR), also known as Ground Potential Rise (GPR) refers to the phenomenon of large current flow to the earth through earth grid impedance. The potential relative to a distant point on earth declines with distance from the source and is the highest at the point where the current enters the ground. GPR is a cause of major concern in designing of electrical substations because a high potential may be quite hazardous for the workmen and the equipment. The potential gradient (drop of voltage with distance) may be high enough that it may develop even between the workman’s two legs, or between the ground on which he is standing and a nearby metal object. Any conducting object which is connected with the earth or ground of the substation such as telephone wires, metal piping or fences may be energized even at the ground potential of the substation. This transferred potential is a great hazard to the people and equipment within and outside of the substation.


Electricals with IS: 15652 rating provided by ISI should be used for greater safety.

An antistatic floor mat or a ground mat is antistatic device which is designed to eliminate static electricity. It does so by collecting the static electricity through the conducting material embedded in it. However, the mat must be grounded (earthed) to do its job. This is done by plugging it into the grounded line with an electrical outlet. Static electricity needs to be discharged at a slow rate; therefore a resistor should be used in the grounding arrangement of the mat. However, some mats are available these days that allow you to connect an antistatic wrist strap on them.

Rubber mats are used as floor covering around electrical panels to safeguard the life and limb of the staff due to short circuits or the possible leakage of the current.

Rubber mats are commonly used in substations, power generation plants, workshops etc.

Voltage Test: The rubber mats are tested to pass the voltage test at 15000 V for one minute, without showing any warming effect or getting punctured.

Breakdown Strength:  The rubber mat should not fail at less than 40000 volts or should have breakdown strength as per the procedure outlined in IS: 2584/83.