LABORATORIES
3/16/2007 1LPI 2007 West Palm Beach
IEEE UpdateLPI Annual Meeting
March 16,2007William Bush
Director of Research – Power & Grounding
Panduit LabsPanduit Corp, New Lenox, IL
LABORATORIES
3/16/2007 2LPI 2007 West Palm Beach
IEEE Activity
IEEE Std 1100TM-2005
IEEE C62.72
IEEE Guide – Protecting Residential
IEEE SPDC (including 10x350 Forum)
LABORATORIES
3/16/2007 3LPI 2007 West Palm Beach
IEEE Activity - 2
IEEE papers
IEEE meeting minutes
Other
LABORATORIES
3/16/2007 4LPI 2007 West Palm Beach
Human safety first
LABORATORIES
3/16/2007 5LPI 2007 West Palm Beach
See clip
Engineers at work
From Internet; Courtesy Dilbert, Comedy Central
LABORATORIES
3/16/2007 6LPI 2007 West Palm Beach
Grounding and bonding
GroundingBonding
Grounded
Bonded
Grounded
Bonded
Grounding
Bonding
Grounded
LABORATORIES
3/16/2007 7LPI 2007 West Palm Beach
Grounding frequencies
Power system sub-harmonics and offset (dc to 60 Hz)Power system harmonics (from 120 up to 3 kHz)Analog communication circuits (from a few up to hundreds of kHz)
Single point grounding for low voltage level circuitsHigh-speed digital circuits (high kHz to GHz)
Single and multi-layer planes (common surface) on PCB
LABORATORIES
3/16/2007 8LPI 2007 West Palm Beach
Purposes of G&B
1) SafetyReduce fire hazardPrevent electric shock Avoid equipment damage
3) PerformanceControl current pathsEqualize voltage referenceReduce communication noise
2) Lightning and Surge MitigationControl transientsRemove static charge Bond between all services Equalize surge reference points
LABORATORIES
3/16/2007 9LPI 2007 West Palm Beach
Grounding myths
Myth1. Current takes the path
of least resistance
2. Ac and dc “noise”goes into the earth ground and stays there
3. Lightning never strikes twice in the same place
Fact1. Current paths are
controlled by impedance
2. Currents into the earth always return to source (lightning and static discharge are a special large-scale case)
3. Lightning strike is an independent (probability) event
LABORATORIES
3/16/2007 10LPI 2007 West Palm Beach
NFPA 70 vs. 780
LABORATORIES
3/16/2007 11LPI 2007 West Palm Beach
Special concern - headsets
LABORATORIES
3/16/2007 12LPI 2007 West Palm Beach
Ground loop
LABORATORIES
3/16/2007 13LPI 2007 West Palm Beach
Ground loop - 2
LABORATORIES
3/16/2007 14LPI 2007 West Palm Beach
Common bonding network
LABORATORIES
3/16/2007 15LPI 2007 West Palm Beach
Conducted Z variation
0
50
100
150
200
0 1 2 3 4 5 6
Frequency MHz
Impedance OHMS Inter-cabinet signal-common impedance
Ground WireGround Wire andSRG
Ref. CDC
LABORATORIES
3/16/2007 16LPI 2007 West Palm Beach
Reflection
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