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Ground Fault Circuit
Interrupters
Jonathan Potter
GE Energy Management
Industrial Solutions
Imagination at work
Purpose of GFCI’s
GFCI devices protect people from hazardous electric shock
Listed to UL 943
Breakers also comply with UL 489
GE Industrial Solutions | November 2014
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30.0
600
25.0
500
20.0
400
15.0
300
10.0
200
5.0
100
0.0
0
# of GFCI's
Electrocutions
700
19
94
19
97
20
00
35.0
19
70
19
73
19
76
19
79
19
82
19
85
19
88
19
91
GFCI's (millions)
Electrocutions Associated With Consumer
Products (US Data)
# Electrocutions
GE Industrial Solutions | November 2014
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Basic Concepts
Ground Fault / Residual Current
Electric current that flows from electrical equipment through a
human to ground.
Terms used:
UL 943:
IEC:
ground fault current
residual current
Potential causes:
• Insulation fault in the equipment.
• Wiring fault in the equipment or installation.
• Current from equipment to earth in absence of fault.
GE Industrial Solutions | November 2014
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GFCI/RCD Technology
VOLTAGE DEPENDENT (VD)
• Device with electronic detection, evaluation and/or interruption
functions, that is dependent on line supply voltage
• Differential current detection typically by current transformer
• Current interruption by electromagnetic mechanism with electrical
contacts.
VOLTAGE INDEPENDENT (VI)
• Electromechanical device in which neither detection, evaluation nor
interruption depend on line supply voltage
• Differential current detection and energy for operation typically by
current transformer
GE Industrial Solutions | November 2014
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Benefits of Voltage Dependent technology
Electronics provide features not generally available to
Voltage Independent devices :
Higher detection sensitivity
– VD devices:
max 6 mA - threshold for “let-go” current (UL 943)
– VI devices:
min 20 mA - threshold current for ventricular fibrillation, require
special manufacturing techniques
GE Industrial Solutions | November 2014
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Benefits of Voltage Dependent technology
End of life indication
• UL 943 specifies that GFCIs at end of life shall, upon conducting an
internal test, either:
– a) provide an indication that the device needs replacing, or
– b) make the device unable to deliver power.
GE Industrial Solutions | November 2014
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Benefits of Voltage Dependent technology
VI
VD
Current Level
(Milliamperes)
Probable Effect on Humans
> 2000 mA
Cardiac arrest, internal organ damage, and severe burns. Death is probable.
100-2000 mA
Ventricular fibrillation (uneven, uncoordinated pumping of the heart.) Muscular contraction and
nerve damage begins to occur. Death is likely.
>20mA
17-99 mA
Extreme pain, respiratory arrest, severe muscular contractions. Individual cannot let go. Death
is possible.
gap
6-16 mA
Painful shock, begin to lose muscular control. Commonly referred to as the freezing current or
"let-go" range.
5 mA
Slight shock felt; not painful but disturbing. Average individual can let go. However, strong
involuntary reactions to shocks in this range may lead to injuries .
1 mA
Perception level. Slight tingling sensation.
GE Industrial Solutions | November 2014
References
•NIOSH [1998]. Worker Deaths by Electrocution; A Summary of NIOSH Surveillance and Investigative Findings. Ohio: US Heath and Human Services.
•Greenwald EK [1991]. Electrical Hazards and Accidents - Their Cause and Prevention. New York: Van Nostrand Reinhold.
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How GFCI’s work
Current “Adding Machine”
L
IIn
Load
N
IOut
Differential Current Transformer
If the current out = current back, the differential current transformer shows no
output.
GE Industrial Solutions | November 2014
How GFCI’s work
Current “Adding Machine”
L1
IIN
240V
Load
L2
IOut
Differential Current Transformer
L1
IIN
N
L2
120/240V
Load
IOut
Differential Current Transformer
GE Industrial Solutions | November 2014
How GFCI’s work
Current “Adding Machine”
Under Ground Fault Conditions
Ground-Fault
IIn = 6A
L
Load
N
IOut = 5.9A
.1A
Differential Current Transformer
If I-out does not equal I-in, the differential current transformer
creates an output signal.
GE Industrial Solutions | November 2014
GFCI location requirements per US National
Electric Code 2014
In general, GFCI devices are required in wet locations
Bathrooms, Garages, Outdoors, Unfinished basements
Kitchens near countertops
Sinks – Where receptacles are installed close to the sink
Bathtubs or shower stalls - where receptacles are installed close to
the shower stall or tub
Laundry areas
Boathouses
Dishwashers
And other locations…
GE Industrial Solutions | November 2014
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Questions???
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