Step and Touch Voltage Simple Explanation
When a fault occurs, fault current flows to the ground through the grounding conductor to earth. And potential gradient is established around electrical equipment on the surface and is equal to the potential difference between two points on the surface of the earth. This potential gradient may affect a person in two ways, either by step-to-step contact or by touch contact.
Step Voltage is the voltage difference between two different voltage level on the ground with 0.5 m spacing between the one-step when a person standing on the floor of the substation.
The solution of step voltage is hopping, take a little jump with both feet.
Its magnitude depends upon the fault current and soil resistivity.
Touch Voltage
Touch voltage is the potential difference between the ground potential rise of a ground grid or system and the surface potential at the point a person standing. While at the same time having a hand in contact with a ground structure.
Example: A person has 800 V at his feet, so contact with 1000 V equipment results in a 200 V touch voltage.
Step Voltage
The difference in surface potential that a person experience bridging a distance of 1 m with the feet without contacting any grounded object.
Example: A person is walking with one foot at 900 V and the other at 800 V. So, resulting in 100 V step voltage.
The level of danger increases considerably in wet weather. For example, wet asphalt or soil is a better conductor than dry ground. It has a higher resistance. Therefore, you should be as careful as possible when it is raining or swampy.
When a power line breaks or an accident at a substation, the current source is much higher than 1,000 volts. In this case, the impact radius reaches 8 meters. At higher currents, the danger zone is much greater than this value, but the current at a distance of 12-15 meters from the source is not fatal.
How to deal with step voltage:
- Stand up straight on your two feet, bringing your heels together as much as possible;
- Locate the closest path away from the potential voltage source, avoiding obstacles;
- Gently make a turn in the desired direction;
- Move away from the source with as few steps as possible;
- After leaving the danger zone, contact the emergency department immediately to eliminate the hazard.
Step and Touch Voltage Simple Explanation
