2011 mf lrg new orleans, la ground testers: two types fall-of- potential “stakeless” clamp-on...
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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?