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 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 the US 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 Impact to Electronic Loads Circuit Board Failure Yes ----- Data Transmit Errors Memory Scramble Hard Disk Crash SCR Failure Process Interrupt Power Supply Failure Program Lock Up Source: Dranetz handbook of Power Quality.

Surge Protection Devices surge arresters, transient voltage surge suppressors (TVSS) Surge Diverters Surge Suppressors

Technology Profiles Surge Suppression Surge 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.

Ideal V-I Clamping Characteristics. Surge Diverters 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 Surge Diverters (Only Performance Data is available): Class A: approximately $30 Class D: approximately $9.99