Soil Resistivity and Grounding System Testing Resistivity and Grounding System Testing ... – Visually Survey Lease Area to Determine Location ... Drive test probes into soil 0 ft; 5 ft;

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<ul><li><p>Soil Resistivity andGrounding System Testing</p><p>Roy Chip WhittenSenior Applications Engineer/Education SpecialistLyncole Grounding Solutions, LLC </p></li><li><p>What Is Grounding ?</p><p>An electrical connection , whether intentional or accidental between an electrical circuit or equipment and the earth, or to some conducting body that serves in place of the earth. </p></li><li><p>Reasons For Grounding</p><p> Personnel safety and equipment protection by providing a path to safely dissipate any unwanted charges or potentials.</p><p> Ensure equipment performance and protection</p><p> Satisfy manufacturers warranty</p></li><li><p>Electrical Protection Pyramid</p><p>RFAC Surge</p><p>Telco / DataLightning</p><p>Grounding</p></li><li><p>Resistance To Earth</p><p>20v 12v 10.6v11v16v 10.18v10.5v 10.45v</p><p>25 Ohms</p><p>0</p></li><li><p>Grounding System Components</p><p>Equipment</p></li><li><p>SoilResistivity</p><p>Basics</p></li><li><p>Soil Resistivity</p><p>Resistance of earth to current flow, measured in Ohms-Meter, between opposite faces of a cube of earth, one cubic meter in volume </p><p>Earth</p><p>1 Cubic Meter</p><p>Signal Generator</p><p>~</p></li><li><p>Soil Resistivity</p><p>Key Variable in System Design</p><p> Determines grounding system resistance Changes from Site to Site Dependent on:</p><p> Soil type Moisture Electrolytes Temperature</p></li><li><p>Soil Resistivity Comparison</p><p>Surface Soils 100 - 5,000Clay 200 - 10,000Sand and Gravel 5,000 - 100,000Surface Limestone 10,000 - 1,000,000Limestone 500 - 400,000Shale 500 - 10,000Sandstone 2,000 - 200,000Granites, Basalts, etc 100,000Decomposed Gneisses 5,000 - 50,000Slates, etc 1,000 - 10,000</p><p>Soil Type Resistivity (ohm-cm)</p></li><li><p>Effect of Moisture on Resistivity</p><p>020406080</p><p>100120140160180</p><p>0 5 10 15 20 25 30Moisture Content (% by weight)</p><p>Res</p><p>istiv</p><p>ity (o</p><p>hm-c</p><p>m) </p><p>x Th</p><p>ousa</p><p>nd</p></li><li><p>Effect of Electrolytes (Salt)on Resistivity</p></li><li><p>Effect of Temperature on Resistivity</p><p>0</p><p>50100150200250300350</p><p>68 50 40 32 14Temperature F</p><p>32</p><p>25</p><p>Res</p><p>istiv</p><p>ity (o</p><p>hm-c</p><p>m) </p><p>x Th</p><p>ousa</p><p>nd</p><p>Water Ice23</p></li><li><p>SoilResistivity</p><p>Testing</p></li><li><p>4-Pt. WENNER METHOD</p></li><li><p>Soil Resistivity Testing</p><p> Key Variable in System Design 4 Point Wenner Method</p><p> Most Accurate Multiple Depth Testing</p></li><li><p>4-Pt. Wenner Method</p><p> Visually Survey Lease Area to Determine Location and Direction For Test Not parallel to buried metallic objects Not parallel overhead power lines Sufficient straight line distance to allow for test</p><p> Minimal distance 300 feet</p></li><li><p>4-Pt. Wenner Method</p><p>15 ft 10 ft 5 ft 0 ft</p><p>C1P1P2C2</p><p>A</p></li><li><p>4-Pt. Wenner Method</p><p>Site Area</p><p>Direction of Test</p></li><li><p>Examples of 4-Point Testing</p></li><li><p>4-Pt. Wenner Method</p><p>Drive test probes into soil0 ft; 5 ft; 10 ft; 15 ft0 ft; 10 ft; 20 ft; 40 ft0 ft; 20 ft; 40 ft; 60 ft</p><p>Connect wire leads from meter to probesC1 to 0 ftP1 to 5 ftP2 to 10 ftC2 to 15 ft</p><p>C1 to 0 ftP1 to 10 ftP2 to 20 ftC2 to 30 ft</p><p>C1 to 0 ftP1 to 20 ftP2 to 40 ftC2 to 60 ft</p></li><li><p>Soil Resistivity Testing4 Point Data Interpretation</p><p> =+</p><p>+</p><p>+</p><p>41 2</p><p>42 2 2 2</p><p>ARA</p><p>A BA</p><p>A B( ) ( ) = Resistivity A = Spacing of probesB = Depth of probes R = Resistance </p><p>(reading from meter)If A&gt;20B, then = 2 AR (ohm-ft)</p><p>= 1.915 AR (ohm-m)(2 / 3.28 = 1.915 )</p></li><li><p>4-Pt. Wenner Method</p><p>Probe Spacing Meter Reading Calculated Resistivity(Feet) (Ohms) (Ohm-Meter)</p><p>5 52.00 497.90</p><p>10 19.68 370.87</p><p>15 10.16 292.00</p><p>20 6.53 250.10</p><p>30 4.30 247.04</p><p>40 10.80 827.28</p><p>60 7.40 850.26</p><p>80 5.58 855.60</p><p>100 4.44 850.26</p><p>= 1.915 AR</p></li><li><p>Typical Grounding Electrode System</p><p>Resistance Requirements</p></li><li><p>Typical Resistance Requirements</p><p> NFPA 70 NEC 25 OHMS or Two Rods</p><p> IEEE Standard 142 &amp; 1100 Equipment Dependent</p><p> Motorola Standard R-56 10 OHMS (Design Goal)</p><p> Telecommunications 5 to 10 OHMS</p><p> Emerson 3 OHMS</p><p> Essilor 3 OHMS</p><p> GE Medical Systems 2 OHMS</p></li><li><p>25 Grounding System</p><p>Lightning</p><p>Strike</p><p>18,000APotential Rise will be</p><p>~450KV at the site</p></li><li><p>5 Ohm Grounding System</p><p>Lightning</p><p>Strike</p><p>18,000APotential Rise will be</p><p>~90KV at the site</p></li><li><p>Grounding System Resistance Testing</p></li><li><p>Grounding System Testing</p><p> Why Test Grounds?</p><p> Confirm Design Spec Satisfied</p><p> Satisfy Warranty Reqs</p><p> Determine Baseline </p><p> Ensure Equip Protection &amp; Performance</p><p> Validate Construction</p></li><li><p> Two Test Methods</p><p> Fall of Potential (Three Point) Test</p><p> Clamp-on Test </p><p>Testing Methods</p></li><li><p>Required Equipment3 / 4 Pole Tester</p><p>Test KitProbesConductorTape MeasureHammer</p><p>Ground System Testing</p></li><li><p>Fall-of-Potential Method</p><p>P2 Auxiliary Voltage ElectrodeGround Rod</p><p>Under Test</p><p>Earth</p><p>C2</p><p>RemoteCurrent</p><p>ElectrodeC1P1</p><p>1 ft 10%20% 30% 40% 50%60%70%80% 90%</p><p>10 x depth of electrode</p></li><li><p>P2 Distance P2 Distance Resistance Amt. of Change( %) ( feet ) ( Ohms ) (Ohms)</p><p>1 1 ft 67.0 -10 % 10 ft 114.5 47.520 % 20 ft 119.6 5.130 % 30 ft 121.3 1.740 % 40 ft 122.2 0.950 % 50 ft 122.5 0.360 % 60 ft 123.1 0.6 70 % 70 ft 123.7 0.680 % 80 ft 126.6 2.990 % 90 ft 141.8 15.2</p><p>100 % 100 ft C2 -</p><p>Fall-of-Potential Test Results</p></li><li><p>Res</p><p>ista</p><p>nce </p><p>(ohm</p><p>s)</p><p>5565758595</p><p>105115125135145</p><p>0 10 20 30 40 50 60 70 80 90 100 P2 Probe Spacing</p><p>Fall of Potential</p><p> Why 10+ Samples? Single Point Could Be Misinterpreted Data Must Be Plotted</p><p> Visual Plateau Confirms Test Validity</p></li><li><p> #1 Reason Not Isolating System Under Test</p><p> Meter is a constant amperage meter Part of the current travels through the connection The ground system is part of a parallel network</p><p> Test Is Invalid Unless Disconnected</p><p>Fall Of Potential Test</p><p>Why Invalid?</p></li><li><p>Ground Resistance Testing Data Plot</p><p>Invalid Test Graph</p><p>Ohms </p><p>Distance (Ground-Probe)</p><p>Test With Neutral Connected</p><p>Plot For 5 Ohm Ground</p><p>Plot For 25 Ohm Ground</p><p>Plot For 100 Ohm Ground</p><p>Plot For 1000 Ohm Ground</p><p>5</p><p>15</p><p>10</p><p>20</p></li><li><p>Fall Of Potential Test</p><p>Why Invalid?</p><p> #2 Reason Insufficient Probe Spacing</p><p> Reqd to Avoid the Spheres of Influence</p></li><li><p>Spheres of Influence</p><p>Readings Not Impacted by Spheres of Influence</p><p>2025</p><p>15100500</p><p>Plateau System Resistance</p><p>Fall of Potential Test</p><p>CurrentProbe</p><p>50-100ft Spacing</p></li><li><p>Fall of Potential Test</p><p> Spacing For Current Probe? Single Electrode</p><p> Minimum 5X Length of Rod Ideal, 10X Length of Rod</p><p> 10 Foot Rod, 50-100 Feet Away 200 Foot Well, 1000-2000 Feet Away</p></li><li><p>Ground Resistance Testing</p><p>Clamp-on Resistance Testing Clamp-on Ground Resistance Meter Convenient, Quick, Easy Does Not Require Disconnecting </p><p>Equipment Measures Current on the Ground</p><p>May Read Ground Loops vs. Ground Resistance</p></li><li><p>Clamp -on Meter Operation</p><p>Current Flow</p><p>Current Flow</p><p>R = E / I??? ohms</p><p>2 Control Xformers</p></li><li><p>Service Meter</p><p>Ground Conductor</p><p>Ground Rods</p><p>3 Phase Utility Line</p><p>Induced Current Flow</p><p>Current From Other Grounds Current From Other Grounds</p><p>Clamp-On Resistance Testing Example</p></li><li><p>Clamp-On Resistance Testing Example</p><p>Rx R2R1 R3 Rn-1 Rn</p><p>VI</p><p>Rx R1</p><p>Rn-1 Rn</p></li><li><p>Neutral-GroundBond</p><p>Grounding Conductor</p><p>Clamp-On Meter Operation</p><p>???Current Flow</p><p>Utility Neutral Line</p><p>Series Loop</p><p>Parallel Paths</p></li><li><p>Current Path</p><p>Reading: &lt; 1 OhmInvalid</p><p>Invalid Clamp-on Reading</p></li><li><p>- 48vdcSwitchGear</p><p>Use Extreme Caution</p><p>Qualified Electricians Only</p><p>Clamp-On Use</p><p>Service Entrance</p></li><li><p>THANK YOU FOR YOUR ATTENTION Please enjoy the rest of your time at the</p><p>2015 BICSI Fall Conference &amp; ExhibitionRoy Chip Whitten</p><p>Senior Applications Engineer/Education SpecialistLyncole Grounding Solutions, LLC</p><p>800-962-2610 </p></li></ul>


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