2011 MF LRG New Orleans, LA

Ground Testers: Two Types

Fall-of-Potential

“Stakeless”Clamp-on method.

2011 MF LRG New Orleans, LA

Garrison MALS Deployed

MALS

Fall-of-PotentialClamp-On

Ground Testers

Yes No

2011 MF LRG New Orleans, LA

Garrison MALS

have Ground systems that can use the utility ground as a reference.

Ground Tester, Clamp-on

Ground Testers

2011 MF LRG New Orleans, LA

Deployed, Generator-Powered Complex

Deployed with no good reference ground for the clamp-on tester.

Fall-of-Potential

Ground Testers

2011 MF LRG New Orleans, LA

55

Clamp-On Ground Tester

Clamp-on Tester: How it works

Ground Meter Reading (R) = Rod Tested + Reference Ground

R

2011 MF LRG New Orleans, LA

1--------------------------

1/25 + 1/25 + 1/25R = 25 +

R = 25 + 8 = 33 ohms (meter display)

Example of Poor Ground Reference (3 rods)

Actual Resistance

Clamp-On Ground Tester

2011 MF LRG New Orleans, LA

77

Clamp-on Tester: How it works

Ground Meter Reading (R) = Rod Tested + Reference Ground

R

If Reference = ~1 ohm, then R ~ Rx

Clamp-On Ground Tester

2011 MF LRG New Orleans, LA

1--------------------------1/25ohm (x 25 rods)

R = 25 +

R = 25 + 1 = 26 ohms (meter display)

Example of Good Ground Reference (25 rods)

Actual Resistance

Clamp-On Ground Tester

2011 MF LRG New Orleans, LA

Deployed, Generator-Powered Complex

Deployed with no good reference ground for the clamp-on tester.

Fall-of-Potential

Ground Testers

2011 MF LRG New Orleans, LA

1010

Clamp-On Ground Tester: Operation

• Meter Applies Voltage• Then Reads Amperage• Calculates Resistance• Meter must create circuit

that goes through Earth

2011 MF LRG New Orleans, LA

Common Mistake: Ground loops

False Reading.Not reading Ground

Clamp-On Ground Tester

2011 MF LRG New Orleans, LA

Ground Grid or Multiple Ground Wire Connections

Jumper

Earth

Clamp-On Ground Tester

2011 MF LRG New Orleans, LA

How often do I measure grounds?

• RTCASS – ground resistance reading once a year.

• More often if ground resistance varies.

• Soil moisture affects ground resistance.

• Seasonal differences in soil moisture.

2011 MF LRG New Orleans, LA

Garrison MALS Deployed

MALS

Fall-of-PotentialClamp-On

Ground Tester Summary

Yes No

2011 MF LRG New Orleans, LA

Questions?