Surge Protection 2014 Presented by: Ken Pitt TPS3 Product Manager Schutzvermerk / Copyright-Vermerk Agenda • Why SPDs are necessary? • What are Surges? (causes & effects) • How does a SPD protect? • UL, NEC, IEEE standards • Applying SPDs • Installation Tips Everything is Electronic Insurance Claims 185, 789 Claims 2009 - Nearly $800 Million 2008 – Over $1 Billion in claims!! What Is a Surge/Transient? Super Bowl XLVII, February 3, 2013 “…power surge caused the outage.” - James Brown, CBS halftime crew host What Is a Surge/Transient? • High amplitude, short duration overvoltage • Can be positive or negative polarity • Can be from energized or grounded conductor Transient Overvoltage – Can be thousands of volts Millionths of second Surge Suppressors • A SPD, TVSS or Surge Suppressor will Not effectively control: • Utility “swells” lasting several cycles • Utility “sags” • Harmonics • Certain noise problems • Not a substitute for Lightning Protection System • Will not save energy or lower utility billing 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 Remember Differential Equations? Solved for steady-state solution and transient solution Math: v(t) = 3te-2t + 2t – 1 transient 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 Power Quality Tolerance Curve Equipment will tolerate 500% overvoltage for 100 s 5 x 120V = 600Vrms 600Vrms x 1.414 = 850Vpeak Goal is to reduce transient overvoltages to tolerable level – in this case 850Vpeak 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 MOV - Metal Oxide Varistor MOV seeks to equalize overvoltage diverted through MOV as current 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) MOV does not ‘absorb’ surge, however, I2R heat is retained Bidirectional – Operates same for positive or negative surges Creates a momentary short-circuit to pass transient energy to earth; analogous to water heater pressure relief valve Normal voltage V 120V I= = 0.12A R 109 Trivial leakage current Overvoltage V 6000V I= = 6000A R 1 Surge Current + + - SPD Operation Zsource Zsurge B D A SPD Operation Load 5 Load 1 Load 2 MOV/SPD Acts as a momentary ‘short circuit’ ‘short circuit’ ≈ no overvoltage ≈ protected load Load 3 Load 4 How Surges Propagate Internal or External? External SPD Internal SPD SPD/TVSS Terminology Modes of Protection • • • • • ‘Mode of Protection’ is a surge path MOVs equalize potential across either side of MOV Various ways to connect MOVs, i.e., various Modes of Protection • L-N • L-G • N-G • L-L IEEE recommends defining modes: L-N, L-G, N-G, etc. (because ‘Common Mode’ and ‘Normal Mode’ mean different things to different folks) A B C True 10-Mode Protection provides directly connected L-L MOVs = Parallel MOVs N G SPD/TVSS Terminology • Let-through voltage, clamping voltage, suppressed voltage, measured limiting voltage (measured in Vpeak) • Surge current, peak-amp current, maximum current, (measured in Apeak) • MCOV - Maximum Continuous Operating Voltage of the electrical system (measured in Vrms) Clamping or Let-Through Voltage MOV/SPD MCOV Surge Current (thru SPD) Load Surge Current vs. Fault Current Surge Current – Normal Operation - Momentary MOV/SPD Load Fault Current – Drawn by Failed SPD - Continuous MOV/SPD Load SPD fails short-circuited and draws Fault Current to be continued… SPD/MOV Failures Industry Issues – Lot of UL & NEC action MOV is a sacrificial element - will protect load or die trying Failure caused by: Sustained Overvoltage - TOV (Can be as few as 2-3 cycles) Sequence: MOV protects, fails, fails short, follow-on fault current causes MOV to catastrophically overheat Typical causes: – Loss of neutral – Missing or Loose N-G bond – Loss of phase (ungr. wye-delta) – Incorrect installation – 120V SPD on 277V system – Cross Phase with N or G – Improper application – Ungrounded or impedance ground – Genset related 19 SPD Damage from Missing N-G Bond (Three Phase) (Enter for Animation) A-N A-G B-N B-G C-N C-G The Pin represents the system’s Neutral Bonding to Ground. If N-G SPD chases L-G overvoltage If N-G Bond is NOT made, the Bond is made, the electrical system has a fixed reference to ground. system becomes Ungrounded. A-G B-G The system will not ‘move’, from instability, resonance, arcing, etc. SPD Only L-G affected, Not L-N Ground Ungrounded systems are inherently unstable. Nothing ‘holds’ or System voltages remain stable. A ground fault ‘stabilizes’ the system. If/when something happens, the system tryingand to short a Phase tofluctuate. Ground will ‘moves’ L-G voltages will The Not SPDskew will attempt to the system. I.e., L-G voltages do notfail. change. control these until the SPD’s L-G mode(s) (Enter for More Animation) 20 MOV Failure Intensity Increases With The Amount of Fault Current Drawn by the MOV MOV/SPD ‘Lower’ Fault Currents (0-20A) Time Load ‘Intermediate’ Fault Currents (20-1000A) ‘Higher’ Fault Currents (>1000A) Current 21 SPD Overcurrent Protection Flaws Cannot assume MOV to fault at low impedance, and draw enough fault current to open fuse: 1.) OCP needs low enough rating to open, and 2.) OCP needs to open before MOV ruptures MOV(s) can fail short here 500A test time Then, MOV(s) can Suppose Fuse clears here overheat & rupture (after a few cycles) before OCP clears UL 1449 THIRD Edition Combine TVSS and Surge Arresters into one UL Standard, UL 1449 3rd Edition renamed: Surge Protective Devices (SPDs) Effective: Sept 29, 2009 SPD Surge Arresters • New SPD Types: Types 1, 2, 3, 4 (& 5) • New Voltage Protection Ratings (VPRs) replace old-style Suppressed Voltage Ratings (SVRs) • New I nominal ratings • Bid Specifications become Obsolete as product evaluation & ratings change (Expensive big deal to manufacturers) TVSS UL 1449-3 & NEC Art. 285 • Changed term TVSS to SPD TVSS XX SPD Aligns with IEC, EN and international usage of term ‘Surge Protective Device’ • Old-style Surge Arrestors are now gone replaced SPD ‘Type’ classification Type 1 – 20kA or 10kA Type 2 – 20kA, 10kA, 5kA or 3kA Type 3 – 3kA Type 4 – Based on intended usage as Types 1, 2 or 3 Type 5 – Suppressor components 24 UL 1449-3 & 2011 NEC Art 285 SPD Types: Types 1, 2, 3 & 4 Based on Location within electrical distribution system Meter Svc. Disc. Panel 10m (30feet) Trans Type 1 OCP built in to SPD, more rigorous testing Type 2 Type 3 Type 4 (Component) tested to Type 1or Type 2 SPD Types UL 1449-3 I nominal Testing – In - (Nominal Discharge Current) - New Concept to USA – Originated from IEC 61643 - Duty Cycle Testing - 15 8x20 s surges through every mode of three samples used for VPR testing Type 1 – 20kA or 10kA Type 2 – 20kA, 10kA, 5kA or 3kA Type 3 – 3kA or None Type 4 – Based on intended usage as Types 1, 2 or 3 27 UL 96A Master Labeling • • Service entrance SPDs are no longer required in order to obtain Master Label certificate. Lightning Protection systems without service entrance SPDs installed will have the cautionary disclaimer added to their Master Label certificate. “At the request of the installer, surge protection may be excluded from the scope of the inspection. The Certificate specifically states this exclusion with one of the following statements, as applicable: "Surge protection was not inspected.“ "The electrical service entrance surge protection system was not inspected.“ "The communication surge protection system was not inspected." The above wording is followed by the cautionary statement: ”Surge protection devices are an integral component of a complete lightning protection system and should be provided on all incoming and exiting electric power, data, and communication services." UL 1449-3 More For Reference now that Standard is 3+ years in use Performance Test Format Changed New Testing uses Six (6) Times More Energy • As surge amplitude goes up, clamping voltage goes up too • Specs become obsolete • Need new VPRs in specs 3000A 500A Old – 6kV / 500A Suppressed Voltage Ratings (SVR) New – 6kV / 3,000A Voltage Protection Ratings (VPR) How Large are Surges? IEEE Research It takes 10kV to push a 10kA surge, 10 meters It takes 27kV to push a 10kA surge, 30 meters It takes 45kV to push a 10kA surge, 50 meters 10,000V (0.1 /m) (0.09 /m) (0.09 /m) L - slight inductance of wire ‘Inductance Police’ 10m 27,000V 30m 45,000V 50m A B C Panel Voltage becomes so high that it flashes over upstream, so surge current is not pushed Similar to shooting fire hose as hard through soda straw – won’t all go! 30 IEEE C62.41.2 - 2002 “Expected voltages and current surges” Table 4 – Scenario I tests for SPDs intended for Location Category C3 Standard tests Optional test 1.2/50µs Voltage generator 8/20µs Current generator Minimum open-circuit voltage to be applied to SPD Current to be driven through the SPDb 100kHz Ring Wave for front-of-wave response evaluation Low 6kV 3kAc 6kV High 10kV 10kA 6kV Exposure Table 3 – Standard 1.2/50 s – 8/20 s Combination Wave Expected voltages and current surges in Location Categoriesa A and Bb Single-phase modesc : L-N, L-G and [L&N]-G Polyphase modes: L-L, L-N, L-G and [L’s]-G (See Table 5 for N-G modes) Peak Valuesd Location Categorya Voltage (kV) Current (kA) Effective Impedance ( ) A 6 0.5 12f B 6 3 2 Surge Protection NEC 2011, Article 285 Page 32 NEC 2011, 285 NEC Article 285 Pertains to Low Voltage Surge Protective Devices (SPDs) Things We See That Are Worth Sharing: NEC 2011, Article 285 Nomenclature: Appropriate term is Surge Protective Device (SPD) Term TVSS is now gone. Aligns with worldwide usage of term ‘Surge’ and ‘SPD’ Unfortunately, America has a colloquial meaning for ‘Surge’, which is not consistent with the intended meaning of ‘transient overvoltage’ For example, last year’s Super Bowl was delayed by a partial power outage, not a surge. NEC 2011, Article 285 285.3: Uses Not Permitted 1.) Circuits exceeding 1kV Why: UL 1449 safety standard only applies to 1kV. Interestingly, there is no safety standard for SPDs/arrestors over 1kV and the Listing requirement in NEC 280 was removed in the 2008 NEC. 2.) On ungrounded systems, impedance grounded systems, or corner grounded delta systems unless specifically listed for use on these systems. Why: SPDs activate upon sensing higher voltages, and these power systems have no reference to ground, or different references to ground. This can (will) fail the SPD if it is not configured correctly. NEC 2011, Article 285 285.3: Uses Not Permitted 3.) Where the rating of the SPD is less than the maximum continuous phase to ground power frequency voltage available at the point of application Why: SPDs activate upon sensing higher voltages. If a 120V SPD is installed on a 277V system, the SPD will attempt to chase the overvoltage until it internally overheats and fails (within seconds). The SPD needs to be rated at sufficient voltage to prevent instantaneous failure. NEC 2011, Article 285 285.5: SPDs Need to be Listed Devices Listed to UL 1449 per NEC Informative Annex A UL 1449 Third Edition (eff. Sept 09) includes rigorous safety testing: Most ‘old-school’ arrestors are gone due to safety issues Some SPDs are not listed, or listed to inappropriate standard (IEEE standard for secondary arrestors, IEC 61643, etc.) Recognized SPDs have requirements that need fulfilled: Did not complete all the failure testing, needs fuses or specific enclosures, etc. Some are very good. Some have deficiencies so severe that they are almost impossible to overcome; intentionally sold (cheap) on the premise that no one will take the time to check. Plenty of DIN-rail mount SPDs come from overseas, with less safetyconscious IEC markings, not UL 1449 Listed. Some do not identify their specific overcurrent protection requirements. NEC 2011, Article 285 285.6: Short Circuit Current Rating (SCCR): Must be greater than or equal to available fault current Most SPDs have 100-200kA SCCRs, which is good Be Aware: Some have very low SCCRs Some require specific fuses or overcurrent protection As a generalization, UL distinguishes between fuses and breakers because fuses have a tendency to clear faster than breakers. If the SPD requires external overcurrent protection, it may have been evaluated & Listed with fuses instead of breakers. But breakers tend to end up on the job, which may not clear fast enough. NEC 2011, Article 285 285.12: Routing of Conductors Must be short and straight as possible Why: Large voltage drops at high surge currents & frequencies. Surges are Not 60Hz & 75A, but are 30,000Hz and possibly 10,000A (!!!) Because of conductor inductance (not resistance), voltage drops can be ≈50 - ≈200 volts per foot. Different physics applies. (V = - L di/dt) This hurts the performance of the SPD. Shorter wires are better. Inches matter. Need gentle bends. No sharp bends or kinks in conductors, avoid wire nuts Gently twisting conductors together like twisted pair reduces inductance SPD Types: Types 1, 2, 3 (4 & 5) Based on SPD Location within electrical distribution system (also coincides with ANSI/IEEE C62.41.2-2002 Categories C, B & A Meter Svc. Disc. Panel 10m (30feet) Trans Type 1 replaces old-school arrestors Type 1 OCP built in to SPD, more rigorous testing Type 1 may be used on load side too Type 2 Type 3 (Plug-In) Type 4 is Recognized or Component Assembly tested to Type 1 or Type 2 Type 5 is a bare component, such as MOV 40 NEC 2011, Article 285 Interesting Tidbits: SPD disconnect should not be counted as one the six disconnects (NEC 230.71(A) beginning 2005) Common to see 10-foot tap rule on SPD retrofits - NEC 240.21(B)(1). Note the inherent advantages of Type 1 SPDs in such applications because OCP is built-in. The surge industry sees a disproportionate number of SPDs fail from improper reference to ground of the power system. Specifically, if the Neutral (X0) is not bonded to Ground at the upstream transformer. See animation next slide. Surge Protection NEC 2011, Article 708 Page 45 2011 NEC Article 708 708.2 Definitions: Critical Operations Power Systems (COPS). Power systems for facilities or parts of facilities that require continuous operation for the reasons of public safety, emergency management, national security or business continuity. 708.20(D) Surge Protective Devices. Surge protective devices shall be provided at all facility distribution voltage levels. Page 46 46 Surge Protection NEC 2014, Article 700.8 Page 47 2014 NEC Article 700.8 700.8 Definitions: • Voltage surge protective devices (SPD’s) are required to be installed for all switchboards and panelboards of emergency systems. • These surge protection devices and products must be listed. Doesn’t specify ‘Type’ Reasoning Implementation of this rule could prevent damage to emergency power controls and critical electronic loads, thereby enhancing the reliability of emergency systems. 48 Manufacturing Plant Service Entrance – Applying surge protection at the incoming electrical service “Stops Surges Before They Get In.” These types of surges contain the largest surge energy warranting 300kA or more of surge current redundancy. Outside Loads – SPDs should be installed at distribution panels feeding remote warehousing, parking lot lights, etc. to prevent back feeding surges entering the main building. Lower Voltage Panels – If the facility is supplied with a higher system voltage (i.e. a 480Y/277V service), 120V panels need SPDs to condition residual surges leaving the service entrance SPD as well as any internally generated surges. Examples could be panels powering in house data center, administrative offices, or any other panels powering sensitive, electronic-rich class locations. Individual Critical Loads – Even if surge protection is applied at the previous locations, redundant protection maybe warranted for sensitive, costly equipment. This may include PLCs, CNCs, drives, control rooms, etc. Data – Security, fire alarm, and telephone systems using copper communications lines need protection especially for computers and automation control circuits. Page Selecting kA Ratings • Realistic kA Per Phase ratings: Service Entrance: 200kA-300kA per phase Distribution: 100kA-200kA per phase Point of Use: 50kA-100kA per phase kA buys redundancy - up to a point A B MOVs C MOVs Not carved in stone: Consider upsizing at critical loads, larger panels, outdoor loads, isokeraunic activity, etc. N MOVs G MOVs MOVs MOVs MOVs MOVs MOVs MOVs Consider downsizing based on value, budget, etc. • Specific Modes? L-N, L-G, N-G, L-L MOVs = Parallel MOVs Tire Tread Analogy: • Thicker the tread, the longer it lasts & harder to get a nail through • Bigger SPDs are more robust and withstand more abuse SPDs for Food and Beverage Parallel connected SPD • Service Entrance Panels • Ahead of critical loads (UPS, ATS) • Protects from large surges Series Filter • Process control panels • Broadcast transmitters • Cleans high frequency noise on the power line Data Signal • Cameras • Control wires Surge Protection Installations Supply Side • Only Type 1 Rated SPDs • SPDs are granted exceptions • Conductor sizing undefined in NEC • UL 96A recommends SPD to have I-n = 20kA • Recommend following tap rule • Not required, but good practice is to connect to a disconnect 56 Secondary Side • Type 1 or Type 2 Rated SPDs • SPDs are granted exceptions • Conductor sizing undefined in NEC • Recommend following tap rule • Not required, but good practice is to connect to a disconnect 57 How to land conductors Permissible tap connections • Accessories used to land control wire taps can be used for SPDs • Lug change out kits • Multi-Barrel lugs 58 Monitoring Features • • • • • • • Dry Contacts Surge Counter Remote Monitor NEMA Enclosure Ratings Flush mounting Interfaces N-G Voltage Detection 61 SIEMENS Here to Help Project Tracking Application Assistance Training Sounding Board for issues Competitive crosses or analysis General Help On-Line Live Support Forensic Testing & Analysis of failed SPDs Etc. 888.333.3545 kpitt@aptsurge.com