Advantages of the Smart Ground System

Complexities:
The measurements of soil resistivity, ground impedance, and potential gradients of the earth
introduce a number of complexities not encountered in other resistance, impedance, and
potential measurements. In some situations, it might be necessary to perform several
measurements to plot trends and analyze the situation. Stray currents and other factors can
interfere with the measurements.

With development and industrial growth adjacent to power substations, choosing a suitable pattern or location for test probes to make a resistance test is becoming increasingly difficult. The connection of overhead ground wires, buried water pipes, cable sheaths, adjacent railroad tracks, conveyor systems, and so on, can all have an effect on the electrical circuit being tested and can introduce significant errors. It should also be noted that overhead ground wires might be insulated either deliberately or by poor connections, and therefore, low-voltage tests might give answers different from actual fault tests. To improve the accuracy of the measurement for comparison with calculated values, ground impedance measurements can be performed prior to interconnection of external shield wires, metallic pipes, and other external interferences. *

*Before Startup

Noted Considerations:

• Test electrodes: Electrode/Probe resistance may be too high. Power limitations of the meter may not provide enough circulating current. Typical meters are capable of up to 250mA at 50V
  • The Smart Ground meter is capable of 500V, 15 Amperes
  • A probe performance report allows the user to determine if the resistance of the probes are too high and take corrective action, if needed.
• Stray DC & AC currents: Stray currents can seriously interfere with measurements. In either case it is best to have a measuring device capable of generating test signals that are pulsed/alternating and are different in frequency that that of stray currents.
  • Smart Ground utilizes a random pulsed signal from 0-200Hz
• Reactive component of impedance of large grounding system: grids at power frequency  Smart Ground employs a spread spectrum signal up to 2kHz, removes power frequency noise and eliminates error
  • Smart Ground employs a spread spectrum signal up to 2kHz, removes
    power frequency noise and eliminates error
• Coupling between test leads. Any voltage produced in the potential lead due to
  inductive coupling from current flowing in the current lead is directly added to the true
  voltage and produces a measurement error
  • Smart Ground test cables are shielded to mitigate coupling.
  • Test personnel are trained to properly route cables to avoid possible scenarios
•  Buried metallic objects, e.g. fences, rails & pipelines
  • The ground system editor allows for the modeling of such objects so their
    effect can be quantified.

Other Considerations:

• The grounding system to be tested must be de-energized and isolated: Not practical and
  too costly
  • Smart Ground can test on energized and connected systems. In fact, the
    electro-geometric model will include the connected network.
• Excessive lead lengths required to measure large grids. Small grids require 5x the diagonal
  distance of the grid. Larger grids require more lead length – nonlinear. Very difficult, even in
  rural areas, e.g. private property, rivers, fences, power lines
  • Smart Ground only requires 2x. Much more capable in congested industrial locations.
• Wire leads to probes can be adversely affected by electrical noise (EMI, RFI). The leads
  act as antennas. The longer the lead, the greater the effect.
  • Smart Ground leads are shorter than the typical system and are shielded.
    Hardware filters and algorithms withtin the software identify and remove noise.
• Low signal to noise ratio may result in errors: Large grids result in low resistance and low test
  signals – S/N ratio errors
  • The Smart Ground system utilizes a high power signal and filtering to minimize S/N ratio
    errors.
• The test results have unknown confidence factors – accuracy of testing are not provided.
• Minimal-to-no self-diagnostics of the test equipment.
• With the standard test meter and methodology, all you get is a number…

The standard meter and methodology is not practical, nor advisable, in this day and age due to compounding errors and unknowns.

•  Smart Ground Mitigates all problems/issues and identified in IEEE Std.81
•  Smart Ground is a recognized methodology in IEEE Std. 81 and is EPRI approved
•  All audits are reviewed by Dr. Sake Meliopoulos

Smart Ground is a design and measurement system that consists of a SG Meter, with associated probes and cables, and a laptop computer with WinIGS software. WinIGS is a software program developed to assist in the design, analysis and virtual modeling of power plant grounding systems. Existing grounding systems can be reverse engineered and tested to assess the integrity of the buried cables, steady state of the power system and compliance to safety standards. It features a wide-ranging graphical user interface that allows setting of the measurement parameters and provides detailed reports of the measurement process and the analysis results. Unlike similar software, separate modules are not required – the features and capabilities are integrated into one comprehensive package. Employed in conjunction with the Smart Ground Multimeter (SGM), WinIGS provides a powerful investigative tool to test and analyze any grounding system. The Smart Ground Multimeter (SGM) is a computer controlled multi-function instrument for grounding system measurements. It can be characterized as a combination variable frequency current source and seven channel data acquisition platform. Among its features is a high power output and the capability to filter out EMI/RFI and power frequency (60 Hz) noise. Standard ground test meters do not have these capabilities resulting in unquantified error in the reported measurements. Any calculations or software using the flawed measurements from a standard meter will then result in compounded errors in their results – garbage in, garbage out. Smart Ground is Electrical Power Research Institute (EPRI) approved and specifically included in the IEEE Std. 81, Guide for Measuring Earth Resistivity, Ground Impedance and Earth Surface Potentials of a Grounding System.

The Smart Ground Multimeter (SGM) is a computer controlled multi-function instrument for grounding system measurements. It can be characterized as a combination variable frequency
current source and seven channel data acquisition platform. Among its features is a high power output and the capability to filter out EMI/RFI and power frequency (60 Hz) noise. Standard ground test meters do not have these capabilities resulting in unquantified error in the reported measurements. Any calculations or software using the flawed measurements from a standard meter will then result in compounded errors in their results – garbage in, garbage out.

Smart Ground is Electrical Power Research Institute (EPRI) approved and specifically included
in the IEEE Std. 81, Guide for Measuring Earth Resistivity, Ground Impedance and Earth
Surface Potentials of a Grounding System.

The present version of the SGM and WinIGS software provides 10 measurement functions:
Ground System Impedance Measurement
Soil Resistivity – With multi-layer
Low Impedance/Continuity Measurement
Tower Ground Resistance
Touch Voltage Measurement
Step Voltage Measurement
Ground Mat Impedance
Transfer Voltage Measurement
Oscilloscope Function
Fall of Potential Method Measurement
Types of analysis include:
Safety Analysis – Step and Touch Voltages: Worst Fault Scenario (per IEEE Std. 80 or
IEC 479)
Steady State Analysis
Lightning Shielding Analysis
Lightning Transient Analysis