The actual step and touch voltage level mainly depend on the ground potential rise, gpr. Progress in step and touch voltage equations of ansiieee. The fault simulation results are presented in graphical and tabular form. For example, if you are standing on energized ground, there could be a significant difference in voltage between where one foot and the other are placed, and an. For a safe design where step is the limiting condition we may assume the allowed step potential e step is equal to the fault induced step potential e s at the maximum design fault as one of the boundary conditions of the design. This allows the step and touch voltages to be measured easily and quickly and simulates the bodys electrical resistance, as per the required standards. Step potential is the voltage between two places that are a step apart on energized ground. One of the simplest methods of reducing step and touch potential hazards is to wear electric hazard shoes. Awareness of step and touch potential, caused by earth potential rise, is important for anyone working on highvoltage power transmission and distribution systems above 1 kv.
Common practice better practice measure step and touch potential. Guzman, david guillermo, touch and step potential analysis at 23. Touch and step potential criteria open electrical, 2017 one of the objectives of a safe earthing grid is to protect people against lethal electric shocks in th e event of an earth fault. Involves injecting lower level currents into the ground and measuring touch and step potentials scaling the measured potentials to values that would be encountered during a fault based on the ratio of the calculated fault current to the test current. This chapter contains safety criteria according to ieee standards, step and touch voltage criteria, reduction factor, simplified equations for mesh and step. Computation of ground grid assembly resistance, ground potential rise gpr, step, touch, and mesh voltages. A person could be at risk of injury during a fault simply by standing near the object. Understanding touch voltage potential risk due to treetoconductor contact on distribution circuits epri 1016210 principle investigators. At critical locations, such as the fence around your substation, hazardous step and touch voltages can occur.
An epr event at a site such as an electrical distribution substation may expose personnel, users or structures to hazardous voltages. If you do not understand any part of this guide, please. Step and touch potential resulting from ground potential rise gpr is well understood as a safety hazard in many situations involving energized power sources. Measuring step and touch voltages current injection method.
Identifies the maximum potentials within a userdefined area. Pdf this paper aims to calculate step and touch voltages around transmission line tower foot. Also the effect of more ring main units rmu in a radial network rn. Evaluating step and touch potential risks on earthing systems. This is must viewing for anyone who works around electrical power lines. Step potential electricity will flow from higher voltage to lower voltage. The more the gpr rise, the higher the actual step and touch voltage level.
The permissible voltage thresholds for step potential can be higher than for touch potential. Understanding step and touch potential incident prevention. This will affect ground grid spacing and depth of the grid. Insert the injector electrode at the approximate distance of the projected fault away from.
Three main techniques for mitigating step and touch potential. The difference in surface potential that could be experienced by a person bridging a distance of 1 m 3 with the feet without contacting any grounded object. Step potential calculations closely resemble another service offered by earthing services, being touch potential calculations. In a typical snt application, the transmission line is deenergized and is bonded to the tower to be safe to work on. Evaluating step and touch potential risks on earthing systems of. The open circuit handtofoot voltage during a ground fault. Progress in step and touch voltage equations of ansiieee std. Step potential is nothing the potential developed between the two feet on the ground of a man or animal when a short circuit occurs.
A person has 800 v at his feet, so contact with v equipment results in a 200 v touch voltage. Plots of touch and step voltages along a user defined path. Reducing the effect of lightning on step and touch. Step and touch potential voltage earth potential rise risk. The permissible voltage thresholds for step potential can be higher than for touch. Insert an electrode approximately 1 meter 3 ft from the object and connect the y lead to it. Protection from hazardous step and touch potentials. Due to this potential, the living body may get an electric shock. Difference in surface potential experienced by a persons feet bridging a one step distance of approximately 1 meter 3 feet without contacting any other grounded surface. The purpose of this article to focus on some less familiar but the most important safety induction like step potential or step voltage, touch potential or touch voltage.
Step and touch potentials near high voltage substation due to severe ground faults present a hazard to anyone in proximity to substation when a fault occurs. If they step on one ring while their foot is on the other ring electricity will make up to difference in voltage through the body. Awareness of step and touch potential, caused by ground potential rise, is important for anyone working on highvoltage power transmission systems. With the hgt1, step and touch voltage testing can be carried out quickly, easily and accurately, explains moritz pikisch, product manager at omicron. The current that returns through the earth can create a significant voltage gradient along the ground and between ground and conducting. Human body impedance touch voltage thresholds are related to touch current thresholds by the bodys impedance according to ohms law.
Step potential is the step voltage between the feet of a person standing near an energized grounded. Continuously monitor and alarm step and touch potentials. In any given design, the design may be limited by either step or touch considerations. It is, therefore, crucial to measure step and touch voltage at locations in and around the substation in order to ensure safety for persons and animals. Reducing step and touch potential hazards one of the simplest methods of reducing step and touch potential hazards is to wear electric hazard shoes. Methods to reduce step potential and touch potential in. Touch potential if any conductive object becomes electrically energized, it can create touch potential, which is the voltage difference between any energized object and the feet of a person in contact with it. What is step and touch potential and reducing resistance to.
Also the effect of more ring main units rmu in a radial network rn was investigated by measurement. We also try to give you some pintsize attention on basics of reducing touch potential and why power grid substation yard needs washed clean gravels or stone rather than others. This paper describes the evolution of safety criteria and the development of basic formulae for evaluation of the step and touch potentials in ac substations, from 1961 to the present time. It also explains how to act when a fault occurs in a power station inorder to overcome the pr. Progress in step and touch voltage equations of ansiieee std 80historical perspective abstract. Examples of this danger include downed power lines and. Z150221 4578 purpose of grounding grounding is one of the means of safeguarding employees and the public from injury other means include, but are not limited to, guarding. More can be learned by referring to the dedicated service page for touch potential calculations, however this page shall offer some comparison between the two. Application in touch and step potential estimations ahmad shahsiah, ph. For example, if an overhead conductor falls on a car, and a person touches that car, current could pass from the energized car through the person to the ground. Step potential is a similar concern but considers the likely volume of electricity that may be inducted through the feet and legs of a person standing within the. The voltage drop is nonlinear with respect to distance from the currents point of entry into the earth.
The value of maximum permitted touch potential has a dominant role in determining the design of the earthing grid. In step potential, electricity spreads like ripples or rings over the surface of the ground away from the point of the contact. These step and touch potential risks considered will be emanating from internal or external power system fault currents, flowing in the hv cable system earthing that are accessible to the public and utility operators. In this case the potential distribution earthing system gets electric potential that can become dangerous to persons and can transmit this danger to the other. Scalar potential at the earth surface as well as step and touch voltage distributions were computed based on field theory approach. Ever wonder how electricity flows through a machine when it contacts a line. Solutions for lightning protection, bonding, and grounding. The open circuit foottofoot voltage during a ground fault. Mitigating step and touch potential hazards is usually accomplished through one or more of the following three. Pdf study of step and touch voltages in resistivecapacitive.
Tolerable potential across 50 kg body, step voltage, no surface rock. Both these terms are very important when it comes to the bas. Pdf advanced substation grounding grid design touch. To identify the magnitude of these voltages, calculations and measurements were preformed. This potential gradient may affect a person in two ways, either by step to step contact or by touch contact. Step potential is the voltage difference between the feet of a person standing near a grounded object that becomes energized. What is step potential and reducing resistance to ground. The snt02 kit provides an easytouse method to continuously monitor and alarm step and touch potential. The maximum permitted values of step and touch potentials vary widely between the different standards.
When dry, properly rated electric hazard shoes have millions of ohms of resistance in the soles and are an excellent tool for personnel safety. Pdf this paper describes a new method and instrument for measuring touch and step voltages near a grounding system, for example in and around a. Ground potential rise, step and touch voltages during lightning. Each ring carries a different voltage as it travels into the ground. Earth potential rise earth potential rise epr is caused by electrical faults that occur at electrical substations, power plants, or highvoltage transmission lines.
Pdf a new method and instrument for touch and step voltage. The major parameters of the earthing grid design are soil resistivity. Apr 24, 2016 step potential and touch potentials are very important in substations because during ground faults all the ground current returns to the substation transformer as the substation transformer is grounded. This document provides an overview of the electrical shock. Connect the x and xv leads to the metal object that would be touched 2. Communicating with coworkers effectively, understanding step potential and touch potential, knowing. Step potential step potential is the potential difference between the feet of a person standing on the floor of the substation, with 0.
The maximum touch voltage experienced while standing within a mesh of a ground grid and touching a grounding object. Pdf assessment of step and touch voltages for different. Originally presented at the 2015 purdue underground corrosion short course, this video covers the essentials of using gradient control mats to address overv. Touch potential ppl first responder utility training. Sp aentd tuoc h potential en paynmceglre because electricity is normally invisible, you should know that it can travel through objects and spread through the ground, and even travel through the air in certain conditions. Ground grid and rod properties are remembered, and the last. The following assumptions were made for the fea step and touch potentials simulations in. Evaluating step and touch potential risks on earthing. Performance analysis of actual step and mesh voltage of. Simply drive the special ground rod about 15 feet from the tower, mount the instrument on the rod, and connect the probe to the tower using a standard hot stick. What are step potential and touch potential and step potential and touch potential calculations step potential and touch potential. Step potential is the step voltage between the feet of a person standing near an.
This video explains what is step potential and touch potential. Grounding mats for step and touch voltage protection youtube. Refinements proposed for the 1996 edition of ansiieee std 80 are presented in a broader context of the continuing development of this popular ieee guide. Grid potentials, touch voltages, and grid conductor leakage currents are provided in detail. Step potential is the voltage difference between the feet of a person near an energized, grounded. Step and touch potential resulting from ground potential rise gpr is well understood as a safety hazard in many situations involving. Chapter 6 presents the ansiieee safety criteria applicable to the substation grounding. It is equal to the difference in voltage, given by the. Touch potential touch potential is the voltage between any two points on a persons body hand to hand, shoulder to back, elbow to hip, hand to foot and so on.
Reducing ground resistance is the best way to reduce the step potential and touch potential hazard, for example if the fault current for a highvoltage line is 10 ka and the resistance to ground of the grounding system is 10ohms, then ground potential will be 100 kv. The current that returns through the earth can create a significant voltage gradient along the ground and between ground and conducting objects. Step and touch voltages and grounding potential rise ieee and. Assessment of step and touch voltages for different. Step potential is the step voltage between the feet of a person standing near an energized grounded object. Step and touch voltages and grounding potential rise ieee and iec. Particle in a 1d box reflection and transmission potential step reflection from a potential barrier introduction to barrier penetration tunneling reading and applets. Step and touch potential voltage earth potential rise. What is step potential and touch potential and calculation. Step potential and touch potential excellent explanation. Electrical step potential hazard avoidance step potential is the voltage difference between the feet of a person near an energized, grounded object. Pdf a new method and instrument for touch and step. What is not as well understood is that gpr and the associated step and touch potential can arise from deenergized lines due to electromagnetic coupling from parallel live lines. Earth potential rise is a safety issue in the coordination of power and telecommunications services.
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