Safety equipment: Delta Computer Systems’ Step and Touch (SNT) instrument continuously monitors and alarms step and touch potentials caused by ground potential rise. When used properly, the SNT can enhance the safety of transmission line crews.
The SNT-02 kit is a complete easy-to-use solution: drive the 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.
The SNT provides audible and visual alarm warnings if the probe voltage is in a dangerous range. The SNT also alarms Lost Probe Connection and Low Battery.
The SNT kit includes two hot-stick- compatible probe clamps. The clamp probe works is suited for round rods and aluminum structures. The magnetic probe works well on flat steel surfaces.
Step and Touch Potential
Step and touch potential awareness is important for anyone working on high-voltage power transmission systems. In a typical SNT application, the transmission line is de-energized and is bonded to the tower to be safe to work on. However, the transmission line itself acts as a very large antenna, and can pick up large amounts of energy which must be shunted to earth ground. And if the tower ground is faulty, a dangerous condition can result.
Step Potential: Voltage between the feet of a person
When current is flowing from the tower to the earth ground, a voltage gradient will occur based on the resistivity of the soil, resulting in a potential difference between two points on the ground. This is called a Step Potential as it can cause voltage between a person’s feet.
Touch Potential: Voltage between an energized object and feet of a person
If the ground connection between the tower and the soil is high resistance (common with some soil conditions), the tower itself, and any conductive item touching the tower, can be energized. Touch potential is the voltage between the energized object and the feet of a person in contact with the object.
Monitoring Step and Touch Potential with the SNT
As power transmission systems become increasingly complex and power corridors crowded, it becomes more common for parallel energized lines to couple energy (via electromagnetic induction) to de-energized lines. Further, with the sophisticated power control needed to manage green energy, power levels on various lines can vary dramatically during a work shift.
The SNT-02 kit provides an easy-to-use method to continuously monitor and alarm step-and-touch potential. 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.