surge protection devices
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Surge Protection Devices. By: Stelios Ioannou George Bolos. Definition of Power Quality. Power Quality is measured at end-user side. Good power quality: any electrical device at the end-user side performs as expected and intended. - PowerPoint PPT PresentationTRANSCRIPT
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Surge Protection Devices
By: Stelios Ioannou
George Bolos
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Definition of Power Quality
• Power Quality is measured at end-user side.• Good power quality: any electrical device at the
end-user side performs as expected and intended.
• Poor power quality: If any electrical device misbehaves as a result of fluctuations in voltage waveform magnitude, frequency, harmonic distortion, symmetry, or even discontinuity in supply, then power quality is said to be “poor”.
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Main Power Quality Problems
• Voltage Sags
• Micro-Interruptions
• Long Interruptions
• Voltage Spikes
• Voltage Swells
• Voltage Unbalance
• Harmonic Distortion
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Power Quality Problems Facts
Black-outs, 0.5
Lightning Transients, 39.5
Voltage Variations, 11.0
Oscillatory Transients, 49.5
88.5% of PQ Problems are Caused due to
Transients.
Source: REO, Power Quality Facts. Online Posting: www.reo.co.uk, March 21, 2005.
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According to EPRI(Electric Power Research Institute):• In 1999 power sags, surges and transients cost
US industry over $50B in downtime.• In 2000 the figure doubled to over $100B.• In 2001 related downtime doubled again to
$200B.• By comparison, the 2 day NE USA blackout of
2003 is estimated to cost theUS economy $17B.
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Transients and AC Power
Power line transient voltage levels can be in excess of 10kV approximately compared with an office block in town which can expect levels of 3kV.
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IEEE Definitions of Transients (Std.4-1995)
Open-Circuit Voltage Waveform: - Front Time: 1.2uS ± 0.36uS-Decay Time (Duration): 50uS ± 10uS
Short-Circuit Current Waveform:
- Front Time: 8uS (+1uS, -2.5uS)- Duration: 20uS (+8uS, -4uS)
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Transients Impact On Devices
Source: Dranetz handbook of Power Quality.
Impact to Electronic Loads
Circuit Board Failure Yes ----- Yes
Data Transmit Errors Yes Yes Yes
Memory Scramble Yes Yes Yes
Hard Disk Crash Yes ----- -----
SCR Failure Yes ----- -----
Process Interrupt Yes Yes Yes
Power Supply Failure Yes ----- Yes
Program Lock Up Yes Yes Yes
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Surge Protection Devicessurge arresters, transient voltage surge
suppressors (TVSS)
– Surge Diverters– Surge Suppressors
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Technology ProfilesP
rote
cto
r
Loa
d
Power Line
Power Line
Filter
Load
Surge SuppressionSurge Diversion
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Surge Suppression Profile
Source: Zero Surge Inc., “Surge Removal Filters”. Online Posting: www.zerosurge.com, March 21, 2005.
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Surge Suppression Waveforms
Attenuated Output.
Source: Zero Surge Inc., “Surge Removal Filters”. Online Posting: www.zerosurge.com, March 21, 2005.
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Surge Diverters
V_V1
-8.0V -6.0V -4.0V -2.0V 0V 2.0V 4.0V 6.0V 8.0V-I(D2)
-100mA
-50mA
0A
50mA
100mA
Ideal V-I Clamping Characteristics.
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Surge Diverters Devices and Applications
• Zener Diodes: Ideal clamping characteristics but poor energy limitations.
• Crowbars: High energy capabilities, but power follow problem.
• Metal Oxide Varistors (MOV): low stand-by currents, high short-circuit current capabilities (α diameter) , wide range of operating voltage (α to thickness), energy is evenly distributed on the volume of the MOV.
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Surge Diverter Waveforms
MOV Clamps a 1000V Transient Voltage to 400V and a Current of 344A.
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Common Question
Q: 400 volts let-through voltage, wouldn’t that damage an electronic device operating at 120V?????
A: • 400 volts is peak value, whereas 120VRMS (170V
peak).• The duration of the let-through voltage is less
than 100 us.
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CBEBA Curve
167 us
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Comparison
Surge Diverters
• Ground Contamination.
• MOV is sacrificial element.
Surge Suppressors
• Attenuation of Data.
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Surge Protection Devices Classification And Certification
• Performance
• Reliability
• Mode of Suppression
• Underwriters Laboratories Inc. (www.ul.com)
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Performance
• Class 1 products have suppressed voltage ratings of 330 volts. Under specified test conditions, at any transient voltage level, their measured suppressed voltages are 330 volts or less.
• Class 2 products have suppressed voltage ratings of 400 volts.
• Class 3 products have ratings of 500 volts.
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Reliability
• Grade A products must be certified to have passed 1000 surges of 6000 volts and 3000 amperes without failure.
• Grade B products must pass 1000 surges of 4000 volts and 2000 amperes.
• Grade C products must pass 1000 surges of 2000 volts and 1000 amperes.
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Mode of Suppression
• Mode 1 products protect the ground by not diverting surge energy to it.
• Mode 2 products contaminate the ground wire.
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Price Range
Surge suppressors (Class A, Grade 1, Mode 1):• 7.5A: $125• 15A: $169• 20A: $249
Surge Diverters (Only Performance Data is available):• Class A: approximately $30• Class D: approximately $9.99