Slide 1: Generator Set Overcurrent Protection
Generator Set Overcurrent Protection PowerHour webinar series for consulting engineers Experts you trust. Excellence you count on. September 24 11:00 PDT / 13:00 CDT (1PDH issued by Cummins)
Slide 2: Welcome!
Welcome! PowerHour is designed to help our engineer partners to… • Keep up to date on products, technology, and codes and standards development • Interact with Cummins experts and gain access to ongoing technical support • Participate at your convenience, live or on-demand • Earn Professional Develo
Slide 3: Meet your panelists
Meet your panelists Cummins presenter: Cummins facilitator: High Resolution Headshot Ravi Thapa Tom Bakritzes, Application Engineer Global Sales Training Manager Cummins Inc. Cummins Inc. Your local Cummins contacts: ➢ Western Canada: Ian Lindquist (ian.Lindquist@cummins.com), Western Canada Region
Slide 4: Disclaimer
Disclaimer The views and opinions expressed in this course shall not be considered the official position of any regulatory organization and shall not be considered to be, nor be relied upon as, a Formal Interpretation. Participants are encouraged to refer to the entire text of all referenced documen
Slide 5: Course Objectives
Course Objectives Generator Set Overcurrent Protection While much attention has been placed in recent years on selective coordination and protection requirements for facilities, the premise of these requirements has been protection of the cabling and distribution system. There are unique characteris
Slide 6: Generator Set Excitation Systems
Generator Set Excitation Systems Self excited generator set - Shunt Separately excited generator set - PMG AVR From AVR Key point: Key point: AVR may not have the capability to support the Ability to provide sustained short circuit fault current long enough to clear downstream current during fault c
Slide 7: Alternator Fault Performance
Alternator Fault Performance Decrement Curve (Separately Excited) Current is a function of the AVR, Excitation I3ph, pu = 1/Xd” System and alternator electro-magnetic design. Key points: - Alternator fault current decays, not constant like fault current from a transformer - Conventional AVRs increas
Slide 8: Alternator Fault Performance
Alternator Fault Performance Decrement Curve Multipliers IEEE Std 142-2007 (Green Book) 1.7.1 “Unlike the transformer the three sequence reactances from a generator are not equal. The zero sequence reactance has the lowest value and the positive sequence reactance varies as a function of time. Thus,
Slide 9: Alternator data sheet
Alternator data sheet Alternator reactances are published using the alternator kVA rating as a base Fault current calculations need to use the same base or the reactances need to be converted to the genset kW rating base Engineers will use software packages such as SKM to demonstrate coordination on
Slide 10: Concept Check
Concept Check ___________ excited generator sets make the task of selective coordination simpler because of the ability of the excitation system to sustain a three phase fault current. a) Shunt (self) b) PMG (Separately) c) AVR (Automatic voltage regulator) d) DC 10
Slide 11: Concept Check
Concept Check ___________ excited generator sets make the task of selective coordination simpler because of the ability of the excitation system to sustain a three phase fault current. a) Shunt (self) b) PMG (Separately) c) AVR (Automatic voltage regulator) d) DC 11
Slide 12: Generator Set Response to a Fault
Generator Set Response to a Fault 3-Phase fault (conventional AVR) • Volts collapse, amps peak • Amps collapse • AVR on full • Approximately 3X rated 1-Phase fault (conventional AVR) • Volts collapse on faulted phase, amps peak • AVR on full • Amps don’t collapse on faulted phase • Genset results in
Slide 13: What is an example of an overcurrent protection device on a generator set?
What is an example of an overcurrent protection device on a generator set? 13
Slide 14: Generator Set Response to a Fault With Overcurrent Protection
Generator Set Response to a Fault With Overcurrent Protection CABLE THERMAL DAMAGE CURVE Code Requirement (NFPA 70 (2017) 445.12(A)) “Constant-voltage generators, except ac generator exciters, shall be protected from overload by inherent design, circuit breakers, fuses, GENERATOR THERMAL DAMAGE prot
Slide 15: Fault Current Characteristics
Fault Current Characteristics With Inherent Overcurrent Protection Relay Provided by most generator set manufacturers (based on generator set model and configuration) • Example of inherent generator set overcurrent protective relay: • Cummins Power Command Controls (PCC) “AmpSentry” -PCC regulates f
Slide 16: Generator Set Response to a Fault
Generator Set Response to a Fault With Inherent Overcurrent Protection 16
Slide 17: Generator Set Response to a Fault
Generator Set Response to a Fault With Inherent Overcurrent Protection Spec Note The generator set shall be provided with an overcurrent protective device that is coordinated with the alternator to prevent damage on any possible overload or overcurrent condition external to the machine. The protecti
Slide 18: Concept check
Concept check Generator set inherent overcurrent protection is capable to protect a) Generator set alternator from thermal damage b) Conductors downstream of the generator set c) Downstream distribution devices d) All of the above 18
Slide 19: Concept check
Concept check Generator set inherent overcurrent protection is capable to protect a) Generator set alternator from thermal damage b) Conductors downstream of the generator set c) Downstream distribution devices d) All of the above 19
Slide 20: NEC (2017) Requirements
NEC (2017) Requirements Overload protection of generator and conductors (Article 445.12 and 445.13) Selective coordination (Articles 700.32 & 701.27 & 708.54) Arc Energy Reduction (Article 240.87) Disconnecting Means for Generators (Article 445.18) Separation of Emergency Circuits (Article 700.10) 2
Slide 21: Overload protection of generator set and conductors
Overload protection of generator set and conductors 240.21(G) Conductors from generator terminals. Conductors from generator terminals that meet the size requirements in 445.13 shall be permitted to be protected against overload by the generator overload protective device(s) required by 445.12. 445.
Slide 22: Selective coordination
Selective coordination Selective coordination. Localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by the selection and installation of overcurrent protective devices and their ratings or settings for the full range of available overcurrent
Slide 23: Arc energy reduction 240.87
Arc energy reduction 240.87 Arc Energy Reduction. Where the highest continuous current trip setting for which the actual overcurrent device install in a circuit breaker is rated or can be adjusted is 1200 A or higher, 240.87(A) and (B) shall apply. (A) Documentation. Documentation shall be available
Slide 24: Arc energy reduction 240.87
Arc energy reduction 240.87 Arc Energy Reduction. Where the highest continuous current trip setting for which the actual overcurrent device install in a circuit breaker is rated or can be adjusted is 1200 A or higher, 240.87(A) and (B) shall apply. (A) Documentation. Documentation shall be available
Slide 25: Arc Energy Reduction 240.87
Arc Energy Reduction 240.87 Energy reduction maintenance setting (ERMS) 25
Slide 26: Arc Energy Reduction 240.87
Arc Energy Reduction 240.87 Energy reduction maintenance setting (ERMS) Spec Note The protective system provided shall not include an instantaneous trip function unless the system is operating in arc flash reducing maintenance mode per NEC 240.87 (2017) 26
Slide 27: Concept check
Concept check NEC requirements for arc energy reduction could be met with a) ERMS with local status indicator b) An instantaneous trip setting that is less than the available arcing current c) Generator set inherent protective relay with arc energy reduction functionality. d) All of the above 27
Slide 28: Concept check
Concept check NEC requirements for arc energy reduction could be met with a) ERMS with local status indicator b) An instantaneous trip setting that is less than the available arcing current c) Generator set inherent protective relay with arc energy reduction functionality. d) All of the above 28
Slide 29: Disconnecting means and shutdown of prime mover 445.18
Disconnecting means and shutdown of prime mover 445.18 (A) Disconnecting means. Generators other than cord-and-plug-connected portable shall have one or more disconnecting means. Each disconnecting means shall simultaneously open all associated ungrounded conductors. Each disconnecting means shall b
Slide 30: Disconnecting means and shutdown of prime mover 445.18
Disconnecting means and shutdown of prime mover 445.18 (A) Disconnecting means. Generators other than cord-and-plug-connected portable shall have one or more disconnecting means. Each disconnecting means shall simultaneously open all associated ungrounded conductors. Each disconnecting means shall b
Slide 31: Disconnecting means and shutdown of prime mover 445.18
Disconnecting means and shutdown of prime mover 445.18 (A) Disconnecting means. Generators other than cord-and-plug-connected portable shall have one or more disconnecting means. Each disconnecting means shall simultaneously open all associated ungrounded conductors. Each disconnecting means shall b
Slide 32: Disconnecting means and shutdown of prime mover 445.18
Disconnecting means and shutdown of prime mover 445.18 (A) Disconnecting means. Generators other than cord-and-plug-connected portable shall have one or more disconnecting means. Each disconnecting means shall simultaneously open all associated ungrounded conductors. Each disconnecting means shall b
Slide 33: Lock out tag out
Lock out tag out NFPA 70E requires that equipment must be disconnected from all sources of electrical supply • Neither the e-stop switch or a genset mounted breaker is sufficient to meet LOTO requirements Genset has two sources of electrical supply • Battery + charging system • Utility or paralleled
Slide 34: Disconnecting means and shutdown of prime mover 445.18
Disconnecting means and shutdown of prime mover 445.18 E-stop switch with lockable shroud Disconnect starter battery and lockout Spec Note Emergency stop switch shall be a red “mushroom head” pushbutton device complete with lock-out/tag-out provisions. Depressing switch shall cause the generator set
Slide 35: Separation of emergency circuits
Separation of emergency circuits NFPA70-2017 700.10 (B)(5)(c): Emergency circuits shall not originate from the same vertical switchgear section, vertical switchboard section, panelboard enclosure or individual disconnect enclosure as other circuits EMERG LEGAL REQ’D OPTION Could meet the requirement
Slide 36: Separation of emergency Circuits
Separation of emergency Circuits NFPA70-2017 700.10 (B)(5)(d): It shall be permissible to utilize single or multiple feeders to supply distribution equipment between an emergency source and the point where the combination of emergency EMERGENCY REQUIRED OPTIONAL STANDBY LEGALLY loads are separated f
Slide 37: Course Summary
Course Summary Generator Set Overcurrent Protection • Define generator excitation systems and their effect on fault current performance. • Identify basic generator set overcurrent protection requirements in order to specify the correct protection equipment. • Describe the NEC requirements for select
Slide 38: Additional Resources
Additional Resources Cummins White Papers • A Comparison of Generator Excitation Systems • Alternator Protection • Generator Protection And Disconnect Requirements • AmpSentry Overcurrent Protection and Arc Energy Reduction • Selective Coordination Standards and Design Challenges • Short Circuit and
Slide 39: Q&A
Q&A Type your questions, comments, feedback in the WebEx Q&A box. We will get to as many questions as we can We will publish consolidated FAQ along with presentation and webinar recording on powersuite.cummins.com Your local Cummins contacts: ➢ Western Canada: Ian Lindquist (ian.Lindquist@cummins.co
Slide 40: Closing
Closing Watch out for a follow-up email including:. • A Link to webinar recording and presentation • A PDH Certificate Visit powersuite.cummins.com for: • PowerHour webinar recording, presentation and FAQ archive • Other Cummins Continuing Education programs • Sizing and specification development to
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