Transcript Slide 1

This photo shows the overall lab and electrolytic tank
.
The layout of the model test probes is shown in this photo. The white probes are spaced 6 inches apart and
were used to measure the tank water resistivity at a depth of 6 inches. The black probe offset from the others
is the temporary ground rod (TGR) probe and the other three probes (spaced 0.0413 m from the TGR) are the
probes used to measure touch, step, and transfer touch potential.
This
photo
shows
the
underside
of
the
model.
The model substrate is Styrofoam which was used because of it is an insulator at
the voltages being used, it floats and provides a self-leveling substrate for the
probes and ensures consistent contact with water surface, and it is easy to work
with.
Slide 3 Continued
•
•
•
The model scale is 0.5-inch = 1 foot. This scale was chosen based on tank
dimensions and the need to simulate remote ground, the types and sizes of
grounding electrodes to be modeled, and the rim size of a 22 caliber casing which is
approximately 0.25 inches. In Phase I it was determined to use a circular metallic
plate with a radius of 8 cm for the human foot per previous research performed and
IEEE standards. This was the dimension used for the base of the test legs that were
fabricated earlier this year for field testing. The diameter of the circular metallic plate
is 0.52 foot which is very close at the 0.5-inch scale to the rim diameter of a 22
caliber casing.
The TGR probe is 2.5 inches which equates to 5 feet which is the maximum depth
that a TGR is installed at the worksite. The diameter of the #12 solid copper
conductor used to model a TGR is greater than a TGR is at 0.5 inch scale. However,
the resistivity of a TGR or probe is not sensitive to its diameter and #12 was used for
its stiffness. In further tests a wire gage that better matches the diameter of a TGR in
scale will be used but it is not expected to impact the measurements.
As noted above, the electrodes used to measure touch, step, and transfer step
voltage are 22 caliber casings set flush with the Styrofoam substrate to simulate a
person standing on grade in the vicinity of a TGR. A #12 solid copper conductor is
soldered to the inside of the casing to provide a connection point for measurements.
Shows the underside of the model from a different angle. The step voltage probes are spaced at a scaled
1 meter from one another per IEEE standards for step and touch voltage.
This photo shows one of the four probes used to measure water resistivity.
These probes are 0.25 inches because they need to be less than one-twentieth of the distance between them for
the Wenner 4-point test method. An AEMC Model 4620 was used to measure water resistivity which has varied
from about 17.0 ohm-meter to bout 19.6 ohm-meter over the past couple of weeks. The resistivity measured by
the AEMC Model 4620 was checked against measurements using a conductivity meter and Humboldt soil
resistivity box. The AEMC resistivity and conductivity meter measurements are close indicating that the AEMC
meter can be used for this purpose. The Humbolt soil box gives a higher resistivity measurement (about 20 ohmmeter) but I think this is due to the DC power supply that I am using which is too small for the purpose. I will have
a bigger DC power supply later this week that should be able to better simulate a constant current source and
hopefully resistivity measurements that are closer to the AEMC tank measurements and the conductivity meter
measurements
Another photo of the tank and model at a different angle.
Shows the probe connections and the model in the tank.
These connections will be made using screw terminals and #14 stranded CU conductor in further model testing.
Alligator clip jumpers were used for the preliminary tests because they make for an easier set up.
Photo of the equipment used to perform measurements. Fluke models 179, 335, and 189
multimeters with AEMC model 4620 in background.
THANKS TO KCPL
I want to thank Brian Flier at KCPL for providing me with transmission line parameters last week. They will be very
helpful.
NON-DESTRUCTIVE IN-SERVICE TEMPORARY GROUND JUMPER ASSEMBLY TESTING
Jeff Thomas (KU Jeff - not A. B. Chance Jeff) is doing his master's thesis on non-destructive in-service temporary
ground jumper assembly testing. We will be experimenting with methods other than resistance to detect
connection and cable problems. If anyone can lend us some TGJAs (good and bad) to experiment with we would
appreciate it.
Created by rsolwa on October 19, 2006
Last updated June 20, 2006