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.

• 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”.

Main Power Quality Problems

• Voltage Sags

• Micro-Interruptions

• Long Interruptions

• Voltage Spikes

• Voltage Swells

• Voltage Unbalance

• Harmonic Distortion

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.

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.

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.

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)

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

Surge Protection Devicessurge arresters, transient voltage surge

suppressors (TVSS)

– Surge Diverters– Surge Suppressors

Technology ProfilesP

rote

cto

r

Loa

d

Power Line

Power Line

Filter

Load

Surge SuppressionSurge Diversion

Surge Suppression Profile

Source: Zero Surge Inc., “Surge Removal Filters”. Online Posting: www.zerosurge.com, March 21, 2005.

Surge Suppression Waveforms

Attenuated Output.

Source: Zero Surge Inc., “Surge Removal Filters”. Online Posting: www.zerosurge.com, March 21, 2005.

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.

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.

Surge Diverter Waveforms

MOV Clamps a 1000V Transient Voltage to 400V and a Current of 344A.

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.

CBEBA Curve

167 us

Comparison

Surge Diverters

• Ground Contamination.

• MOV is sacrificial element.

Surge Suppressors

• Attenuation of Data.

Surge Protection Devices Classification And Certification

• Performance

• Reliability

• Mode of Suppression

• Underwriters Laboratories Inc. (www.ul.com)

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.

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.

Mode of Suppression

• Mode 1 products protect the ground by not diverting surge energy to it.

• Mode 2 products contaminate the ground wire.

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