Information Circular 8767 

Guide for the Construction 

of Driven-Rod Ground Beds 

By R. L. King, H. W. Hill, Jr., R. R. Bafana, and W. L. Cooley 

UNITED STATES DEPARTMENT OF THE INTERIOR 

Cecil D. Andrus, Secretary 

BUREAU OF MINES 
This publication has been cataloged as follows: 

Guide for the construction of driven-rod ground beds / by Roger 

L. King .•• ret a1.] [Washington] : U.S. Dept. of the Interior. 

Bureau of Mines. 1978. 

26 p. : ilL, diagrams; 27 cm. (Information circular· Bureau of 

Mines ; 8767) 

1. Electric currents· Grounding. 2. Electricity in mining. I. 

King, Roger L II. United States. Bureau of Mines. III. Series: 

United States. Bureau of Mines. Information circular· Bureau of 

Mines; 8767. 

TN23.U71 no. 8767 622.06173 

U.S. Dept. of the Int. Library 
CONTENTS 

Abstract. . . .. . . .. . . . . . ... . . . . . . . . . . . . . .. . . .. . . . . . . . . . . .. . . . . ... . . . . . . . . . 1 

Introduc tion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

Soil resistivity tneasure11lents.... .. .. . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . .. 3 

Ground bed resistance me"asurements .••.••.•••••...•.••..••. ·••.••· .. • •. •• 4 

Guide for design and construction....................................... 7 

Construction of a prototype ground bed.................. • • . • • • . •• • . • • . . . 7 

Conclusions ........................................... . ~................ 9 

Appendix.--Guide for construction of ground beds........................ 10 

ILLUSTRATIONS 

1. Ground bed conducting fault current during a phase-to-rai1 fault. 2 

2. Ground bed conducting lightning stroke to earth..... .••••....••.• 2 

3. Electrode arrangement for measuring earth resistivity............ 3 

4. Electrode placement for fa11-of-potentia1 measurement............ 4 

5. Effect of current electrode placement......... .••..•.. ••.•••. ••.• 5 

6. Measurement of ground bed resistance using fa11-of-potentia1 

techniq ue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . 6 

7. Fa11-of-potentia1 measurement conducted on Bureau of Mines 

A-t. 

A-2. 

A-3. 

A-4. 

A-5. 

A-6. 

1-

A-t. 

A-2. 

A-3. 

A-4. 

A-5. 

A-6. 

A-7. 

A-8. 

A-9. 

A-lO. 

A-1t. 

A-12. 

A-l3. 

ground bed .................................................... . 

Electrode arrangement for measuring earth resistivity ••.•••••.••• 

Electrode locations for variation-with-depth measurement ..•••••.• 

Measurements A and B ............................................ . 

Measurements C and D ............................................ . 

Alteration of "hollow square" configuration for a case of 

anis otropic soil .............................................. . 

Rod arrangements for resistivity tables ..•.•••.•••••••.••.••.•... 

TABLES 

Resistivity surveys for Bureau of Mines ground bed ••••••••••.•••• 

Explanation of rod types ..••.••.•••••.•..•....•..••..••..•...••.• 

Resistivity less than 20 ohm-feet .••.••.••..•.••..••••••••.••..•• 

Resistivity less than 30 ohm-feet •.••.••.•••.•.•••••••••.••.••... 

Resistivity less than 50 ohm-feet .•••••.••.••.••.•••••.•••.•••... 

Resistivity less than 70 ohm-feet ••..•..•••••••.••.••.••..•..•••. 

Resistivity less than 100 ohm-feet ••.• , .•••••••.••.••..••.•.•.••. 

Resistivity less than 200 ohm-feet ••...••••.••.••..•••.•....•..•. 

Resistivity less than 300 ohm-feet •••..•••••.•..•••••..••.•••..•. 

Resistivity less than 500 ohm-feet ..•••.•.••..••••••••...••.••.•• 

Resistivity less than 700 ohm-feet •••.••..•..••.•••.••..•..••.••. 

Resistivity less than 1,000 ohm-feet .••...•...•..•••••..•••••..•• 

Resistivity less than 2,000 ohm-feet ••.•.••.••••.••••..•..••.•.•• 

Resistivity less than 3,000 ohm-feet .•••.•..••....••..••..•••..•• 

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