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Advanced Protection Technologies

Advanced Protection Technologies. Surge Protection Overview Prepared by: Lou Farquhar, PE, CEM, GBE VP – APT Engineering Service (800) 237-4567. APT. 26 Years Supplying Surge Protective Devices ISO 9001-2008 Quality Management System ISO 17025 evaluation by UL

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Advanced Protection Technologies

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  1. Advanced Protection Technologies Surge Protection Overview Prepared by: Lou Farquhar, PE, CEM, GBE VP – APT Engineering Service (800) 237-4567

  2. APT • 26 Years Supplying Surge Protective Devices • ISO 9001-2008 Quality Management System • ISO 17025 evaluation by UL • Power Quality Assurance magazine – PQ 50 Company • Frost & Sullivan ranked APT – Leading Supplier of Three Phase Devices • Market Engineering Customer Focus Awards • Members of UL, IEEE, NEMA standards committees

  3. What Is a Surge/Transient? High amplitude, short duration overvoltage Can be positive or negative polarity Tidbit: Transient: > two times system’s RMS voltage Noise: < two times system’s RMS voltage Transient Overvoltage – Can be thousands of volts Millionths of second 3

  4. What Causes Surges/Transients? Lightning Switching: Load Switching – utility & customer Motors, Large Loads, Faults, Fuse Operation Source Switching Smart Grid, Gensets, PV, Wind Turbine Internally generated surges: ≈70% Externally generated surges: ≈30% In outdoor environment, this ratio probably reverses 4

  5. Effects of Transient Voltages? Microelectronics Intolerant to Surges Disruption Lockups, Downtime & Interruption costs Computing glitches and errors Degradation Microelectronics Slow & continuous damage to motor insulation Destruction Failed microelectronics, ballasts, motors, controllers, etc. Maybe analogous to: ‘Water hammer’ in a plumbing system ‘Rust’ to microelectronics

  6. MOV - Metal Oxide Varistor Varistor - variable resistor Semiconductor; generally zinc oxide Connects parallel to load (not series) Thickness determines clamping voltage Diameter determines current capacity MOV symbol

  7. MOV - Metal Oxide Varistor • MOV seeks to equalize overvoltage • Voltage sensitive conductor: V = IR & I = V/R • At ‘low’ voltages: very high impedance, 109: I  0A • Above ‘threshold’ voltage: resistance approaches 0: I = high A • Current diverts through MOV as I = V/R (high V, low R) Normal voltage Overvoltage V 120V V 6000V I = = 0.12A I = = 6000A R 109 R 1 Surge Current Trivial leakage current

  8. MOV - Metal Oxide Varistor • Overvoltage diverts through MOV as current • Voltage is “clamped” or “equalized” as energy is transferred to other side of MOV(s) • MOV does not ‘absorb’ surge, however, I2R heat is retained • Bidirectional – Operates same for positive or negative surges • Creates a momentary low impedance (acting like short-circuit) to pass transient energy to earth; analogous to water heater pressure relief valve - + - +

  9. SPD Operation Load 1 Load 2 Load 3 MOV/SPD Acts as a momentary ‘short circuit’ ‘short circuit’ ≈ no overvoltage ≈ protected load After the surge, MOV/SPD automatically resets itself to high impedance state drawing no current Layman’s Terms: Visualize an ‘electronic guillotine’ that chops the head off a surge and sends it away

  10. SPD Operation Load 1 Load 2 Load 3 MOV/SPD Acts as a momentary ‘short circuit’, then resets itself after the surge ‘short circuit’ ≈ no overvoltage ≈ protected load 10

  11. SPD Connector Leads • Need short lead lengths! • NEC 285.12: “The conductors used to connect the SPD (surge arrester or TVSS) to the line or bus and to ground shall not be any longer than necessary and shall avoid unnecessary bends” • Industry typically states: Each foot of conductor adds 100 - 170V to clamping voltage • No Sharp bends or kinks • No Wire Nuts! • Right Hand Rule – can cancel inductive effects by bundling, tie-wrapping conductors together

  12. 2008 NEC Art 285 12

  13. 2011 NEC Art 285 13

  14. APT Here to Help:(800) 237-4567 • Specification Assistance • Training • Sounding Board for issues • Competitive crosses or analysis • General Help • On-Line webinar services • Forensic Testing & Analysis of failed SPDs • Etc.

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