Advanced Protection Technologies Surge Protection Overview Prepared by: Lou Farquhar, PE, CEM, GBE VP – APT Engineering Service (800) 237-4567 May 17-18, 2001 Introduction: Lou Farquhar, P.E., C.E.M. APT Engineering Sales Dept.

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 PQ50 - Handout #1 in your binder.

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 What is a transient? By IEEE definition, a transient is at least two times the system’s RMS voltage. This contrast noise which is less than two times the system’s RMS voltage. A transient is a very short duration event (microseconds) and will be a significant overvoltage or impulse on the AC sine wave. A transient is a small fraction of a 360° sine wave. Millionths of second 3 3

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% Transients tend to be caused by lightning, utility operations or internal disturbances. There are two predominant wave forms used to describe transients. One is a high-energy impulse, a rapid rise and fall. The other is a ring wave, which oscillates at high frequency as it dissipates. IEEE has developed typical waveforms to describe these events, which will be discussed later. In outdoor environment, this ratio probably reverses 4 4

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 How do transients cause damage? Transients can cause data transfer glitches as "0's"are misinterpreted as "1's" in a digital data transmission. Bad data can and has shut down operations. The overall cost of any kind of disruption is staggering. Manpower is expensive as people stand around waiting for equipment to reset. Production is lost in batch runs. Many industries require a continuous production flow or else the product must be discarded. Transients have a cumulative effect much like static discharges. One of the fundamental purposes of surge suppression is to limit voltages to microelectronic equipment such as IC chips. Chips are composed of layered silicon substrates that are permanently damaged when excessive voltage “punches-through” a silicon layer. This occurs at the micron level and is difficult to troubleshoot. The appropriate repair is to replace suspect components. A rare but worst case transient scenario is substantial destruction. This is usually caused when a component fails due to a transient and an unusual chain of events leads to catastrophic failure. 5

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 The Metal Oxide Varistor is the primary surge suppression component. MOVs are typically made of zinc oxide and are a solid-state semiconductor device. They are bi-directional and will control both positive and negative surges. MOVs come in many diameters and configurations. They are very common in automotive applications. 6

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 The Metal Oxide Varistor is the primary surge suppression component. MOVs are typically made of zinc oxide and are a solid-state semiconductor device. They are bi-directional and will control both positive and negative surges. MOVs come in many diameters and configurations. They are very common in automotive applications. Trivial leakage current Surge Current

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 - MOV reaction times are less than 1/2 nanosecond… transients occur in the microsecond range of time. MOVs sum like capacitors when installed in parallel. Resistance decreases like paralleled resistors. Paralleling MOVs increases capacity, lowering impedance at the same time. + + -

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

‘short circuit’ ≈ no overvoltage ≈ protected load 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

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

2008 NEC Art 285 12 12

2011 NEC Art 285 13 13

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