Touch Potential (TP): Key Concepts and Testing Techniques

Touch Potential (TP) is an electrical engineering and safety concept that describes the in voltage difference (potential difference) between 2 points on a conductive object when one person impacts them both at the same time. 

It is an important method for evaluating electrical systems and equipment for safety in environments where electrical faults are possible.

Touch Potential is the voltage experienced when two surfaces or sections of an object with differing electrical potentials come into contact, and this difference may provide an electric shock risk if it surpasses safe levels.

Touch Potential is an important aspect in electrical safety standards & regulations, as it assists in establishing the appropriate safety measures and insulation requirements to avoid electric shock hazards. 

Touch Potential thresholds are often substantially lower than Step Potential thresholds, which measure voltage differences when taking steps in places with varying ground potential.

What is Touch Potential (TP)?

Touch Potential is the voltage difference that occurs when a human touches 2 different conductive surfaces (or) things with varied electrical potentials. 

One of these surfaces is normally grounded, whereas the other may not be, posing a risk of electric shock.

Touch Potential is an electrical danger since it carries the possibility of electric shock. 

When a person touches 2 surfaces of different potentials & completes an electrical circuit via their body, they may be exposed to deadly quantities of electricity.

Touch Potential conditions involve electrical currents flowing through & around the person’s body, including the heart. 

This is an important concern since electrical currents traveling through the heart can interrupt its natural rhythm and even induce cardiac arrest.

To reduce the risk of Touch Potential risks, safety precautions are essential. These steps may include properly grounding 

• Equipment & structures, 
• Maintaining insulation & electrical systems, 

& ensuring that people are trained in electrical safety standards.

Touch Potential thresholds are commonly specified by safety standards & regulations in order to create safe limits for potential variations that individuals may encounter. 

These procedures help to protect workers & the general public when conditions comprising electrical equipment & systems.

Warning Signs of Touch Potential

It is possible that it will come into electrical touch potential threats as a result of the following: 

• Power lines that have fallen down

• Energized vehicles (or) tools (and/or) 

• Energized trees or tree branches that have been grounded.

Touch Potential Testing Procedure

A Touch Potential Test is an important process in electrical safety that assesses the danger of electric shock when a person contacts various conductive surfaces with varied electrical potentials. 

Here’s a step-by-step procedure to completing this test effectively.

Equipment Required

• Metal object that might be touched (Ex: equipment or structure).
• Grounding systems with E & Es leads.
• Two electrodes: one around a meter (3ft) far from the object, the other at the suspected fault position.
• Test wires (S & H leads)
• 4-Pole Ground Resistance Tester

Step-by-Step Procedure

Step-1: Connect the E & Es Leads

• Start by attaching the E lead to metal object that will be touched.
• Attach the Es lead to a single metal object. These leads will serve as reference points.

Step-2: Position the Electrodes

• Insert one electrode about 1 meter (3 feet) from the metal object.
• Connect the S lead of the ground resistance tester to the electrode.
• Insert the additional electrode in the expected position of the fault.
• Connect the H lead of the ground resistance tester to the second electrode.

Step-3: Start the Test

• Select the 4-point Ground Test Mode on the ground resistance tester.
• Begin the test and note the resistance reading produced by the tester.

Step-4: Calculate the Touch Potential Voltage

• Estimate the anticipated fault current (I). This value may change based on conditions & the characteristics of the electrical system.
• To determine the touch potential voltage (V), multiply the estimated fault current (I) by resistance reading acquired during the test.
• The formula is V = I x R

What is the Touch Voltage?

Touch voltage can be described as the potential difference between the ground potential increase of a ground grid (or) system & the surface potential at the point wherein a person stands with a hand in contact with a ground structure.

What is Step Potential?

A high-voltage condition is produced when current flows from an overhead conductor via a chain-link fence and into the earth. 

This voltage gradient is caused by the resistivity of the soil and results in a voltage difference, also referred to as a potential difference, across two points on the ground. 

Because it might result in a voltage differential between a person’s feet, this is known as a step potential.