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John Stark – Russelectric Inc.

John Stark – Russelectric Inc. Overview. Recent changes to the National Electrical Code (NEC) require the selective coordination of overcurrent protective devices at hospitals and other mission-critical facilities. .

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John Stark – Russelectric Inc.

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  1. John Stark – Russelectric Inc.

  2. Overview Recent changes to the National Electrical Code (NEC) require the selective coordination of overcurrent protective devices at hospitals and other mission-critical facilities. Transfer switches with 30-cycle closing and withstand ratings dramatically simplify designing to that requirement.

  3. Transfer Equipment in a Common Scenario Commercial Utility Power UPS Transfer Switchgear Emergency Generators Network Computer Loads UPS Batteries Air conditioning, Lighting, Mechanical, Building Loads,etc. Generator Paralleling Control Switchgear With regard to the emergency back-up and transfer scheme, it is incumbent upon engineers to select the proper equipment for the application. There are many considerations and they are becoming more with each decade.

  4. What is Selective Coordination? • Definition (Article 100 – NEC) • Localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by the choice of overcurrent protective devices and their ratings. Article 100 provides the Code definition. Here is another way to describe it: • “For the full range of possible overcurrents, the act of isolating an overloaded or faulted circuit from the remainder of the electrical system, thereby eliminating unnecessary power outages.” • The circuit causing the overcurrent is isolated by the selective operation of only that overcurrent protective device which is closest upstream to the overcurrent condition.

  5. Selective Coordination, History & Requirements Selective coordination was first required by the NEC in 1993 for elevator circuits. Amendments to the Code in 2005 and 2008 strengthened the requirements and expanded them to include emergency and legally required standby systems, as well as critical operations power systems. Selective coordination, as defined in the 2008 NEC, is the (as in previous slide)“localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by the choice of overcurrent protective devices and their ratings or settings.” It is a complicated process of coordinating the ratings and settings of overcurrent protective devices, such as circuit breakers, fuses, and ground fault protection relays, to limit overcurrent interruption (and the resultant power outages) to the affected circuit or equipment (the smallest possible section of a circuit). In other words, the only overcurrent protective device that should open is the device immediately “upstream” from the circuit/equipment experiencing an overcurrent condition.

  6. Proper Selective Coordination is becoming more and more of an engineering consideration and is being enforced by inspectors more & more often… Refer to IAEI handout “Selective coordination restricts outages to the circuit or equipment affected, ensuring reliability of electrical power.”

  7. NEC 2008 –Verbiage on Selective Coordination • NEC(2008) 700.27 Coordination: requires “Emergency system(s) overcurrent devices shall be selectively coordinated with all supply side overcurrent protective devices.” • NEC(2008) 701.18 Coordination: requires “Legally required standby system(s) overcurrent devices shall be selectively coordinated with all supply side overcurrent protective devices.” • NEC(2008) 517.26 Application of other articles: requires “The essential electrical system shall meet the requirements of Article 700.” • The overcurrent protective devices may include the following: • Molded Case Circuit Breakers • Fused devices • Insulated Case Circuit Breakers • Air Power Circuit breakers

  8. Requirements • Selective coordination requirements for life safety are not a new concept for the Code. There has been a Code requirement to coordinate selectively the over-current protective devices for elevator circuits since 1993. • Most engineers agree this is the simplest way to assure coordination, however….. • Breakers • Instantaneous circuit breakers will not coordinate properly because typically, they aren’t adjustable. Fuses More on Selective Coordination

  9. G APCB's (Air Power Circuit Breaker) are typically 30 cycle withstand devices. ICCB's (Insulated Case Circuit Breaker) are 30 cycle withstand or up to 4 Cycle Instantaneous. ATS MCCB's (Molded Case Circuit Breaker) typically instantaneous or Current Limiting Devices. One-line Utility 4000A APCB 1600A APCB 1600A APCB 800A ICCB 400A MCCB An overcurrent event (overload, short circuit, or ground fault) here should trip the 400A MCCB

  10. In the absence of other means to satisfy selective coordination, the ATS must withstand a fault or even close on potential fault to be properly coordinated. 400A MCCB G Utility 4000A APCB 1600A APCB 1600A APCB Fault on load side of ATS could see up to 30 cycles of fault current -depending on the Air Power Circuit Breaker settings that is feeding it- and could travel through the ATS and the ATS contacts. ATS ATS 800A ICCB If the 400A MCCB does not trip/clear… Selective Coordination

  11. Review of Code Requirements • Article 517 Health Care Facilities • 517.26 Application of Other Articles • Article 620 Elevators, etc • 620.62 Selective Coordination (2008) • Article 700 Emergency Systems • 700.9 (B)(5)(b), Exception • Article 701 Legally Required Standby Systems • 701.18 Coordination • Article 708 Critical Operations Power Systems • 708.54 Selective Coordination

  12. 2005 Code Adoption

  13. 2008 Code Adoption WA ME ND MT VT M I MN NH MA OR NY WI CT SD ID RI M I NJ WY PA IA NB OH DE Expected July 2010 MD IN NV IL WV Expected July 10’ UT VA CO MO KS KY CA NC Expected January 2011 TN State Adopted SC AR AZ NM OK S. Carolina Code Council adopted 2009 IRC with 2008 NEC 3/22/10 with implementation effective 1-1-11 TX GA AL MS LA State Adopted Unincorporated Areas AK FL AK HI 2008 NEC – 32 States HI, basically 2002 NEC but some islands back to 1993 NEC 2005 NEC – 8 States Local Adoption – (10) Note: Some local adoption states have earlier than 2005 adoptions in some jurisdictions Revised April 19, 2010

  14. Code Rulings In the 2008 Code Cycle there were challenges to the selective coordination requirement. Proposal 13-135 proposed the elimination of the selective coordination requirement for 700.27. The proposal was to remove the selective coordination requirement from the mandatory text and places it in a non-mandatory in a FPN (fine print note). But Code Panel 13 rejected this proposal by a vote of 9-4. To follow is their statement: • Panel 13 Statement: • “This proposal removes the selective coordination requirement from the mandatory text and places it in a non-mandatory FPN (fine print note). The requirement for selective coordination for emergency system over-current devices should remain in the mandatory text. Selective coordination increases the reliability of the emergency system. The current working of the NEC is adequate. The instantaneous portion of the time-current curve is no less important than the long time portion. Selective coordination is achievable with the equipment available now”. Then, Code Panel 20, which was responsible for the new Article 708, summed up the need for selective coordination in their statement to Comment 20-13, (which was another proposal for the deletion of the selective coordination requirement). This comment was rejected 16-0. The actual panel statement to Comment 20-13: • Panel 20 Statement: • “The overriding theme of Articles 585 (renumbered to 708) is to keep the power on for vital loads. Selective coordination is obviously essential for the continuity of service required in critical operations power systems. Selective coordination increases the reliability of the system.”

  15. Exceptions to Code RulingsRefer to IEEE handout “Selective Coordination versus Arc Flash…” page 12 There are numerous proposals being adopted by States and/or City or local governmental bodies which modify the selective coordination requirements. The most commonly heard proposals fall into two categories: 1. Allow the degree of selective coordination needed to be the responsibility of the qualified person responsible for the project. (The Commonwealth of Massachusetts was the first State to adopt such a proposal as an exception to the Articles in 700.27, 701.18 and 708.54, which require selective coordination as follows: Exception No. 2: Where the system design is under the control of a licensed professional engineer engaged in the design or maintenance of electrical installations, the selection of overcurrent protective devices shall be permitted to coordinate to the extent practicable. The design shall be documented, stamped by the professional engineer, and made available for review by the authority having jurisdiction.

  16. Arc Flash ConsiderationsRefer to IEEE handout “Selective Coordination versus Arc Flash…” page 10 This is the other side of the argument regarding the subject of Selective Coordination VS Arc Flash Considerations. The presenter will not delve into this side of the argument, as he is in the business of providing emergency power to critical facilities and therefore is in the camp of having a non-sensitive, robust type system, selectively coordinated, that facility managers want to perform well when called upon. In cases of catastrophic outages, Arc flash considerations might take a back seat to keeping as much of the facility up and running as possible and only Tripping CB’s closest to the fault. For more details on the ARC Flash concerns, and that whole side of the argument, please refer to your handout.

  17. UL 1008 Withstand Test 34.1 When tested under the conditions described in 34.2 – 34.15, a transfer switch shall withstand the designated levels of current until the over-current protective devices open or for a time as designated in 34.3. At the conclusion of the test: • The switch shall be capable of being operated by its intended means; • The fuse mentioned in 34.14 shall not open, • There shall be no breakage of the switch base to the extent that the integrity of the mounting of live parts is impaired, • The door shall be prevented by its latch, without bolt or lock installed therein, from being blown open, and deformation of the door alone is not determined to be unacceptable; • No conductor shall have pulled out of a terminal connector and there is no damage to the conductor insulation or the conductor (see 41.56); and • For a plug in or draw out unit, the point of contact is to be the same both mechanically and electrically as before the test.

  18. UL 1008 Closing Test 36.1 When tested in accordance with 36.2, a transfer switch shall comply with the requirements in 34.1(a) –(f). 36.1 Revised September 18, 1996 36.2 The sample for this test is to be that used for the withstand test. Test procedures and conditions for the closing test are to be as described in 34.3 – 34.19. The switch is to be closed on the circuit. 36.3. The test (for close on) current shall be the same as that used in the withstand test.

  19. UL 1008 Short Circuit Test History • Around 1989 UL introduced an optional 3 cycle test for any over- • current protection device. • Prior to this, manufactures could test with any over-current device. • If a manufacturer didn’t test to 3 cycles, they would be required provide a label that lists all breakers that the switch was “coordinated with”. • This requirement did not take into consideration air power circuit breakers APCB’s. Some of these breakers were 4-5 cycle devices (GE AKR and Westinghouse DS) • January 9th, 2002 UL introduced an optional short time current • rating test. • A withstand and a close and withstand test is required to get a UL short time rating. • This requirement did not take into consideration air power circuit breakers APCB’s. Some of these breakers were 4-5 cycle devices (GE AKR and Westinghouse DS)

  20. Overcurrent Protective Devices • Molded Case Circuit Breakers –MCCB (UL489) • May be Current Limiting to 200KA • Long Time Overcurrent • Instantaneous Interruption is less than 3 cycles • Fuses and Fused Devices • Current Limiting • Mostly used on 200KA circuits • Insulated Case Circuit Breakers -ICCB (UL489) • May be Current Limiting to 200KA • Instantaneous Interruption is typically less than 4 cycles • Short Time delay available (30 cycles) with Instantaneous over-ride • Low Voltage Air Power Circuit Breakers -APCB (UL1066) • May be Current Limiting to 200KA • Instantaneous Interruption is typically less than 4 cycles • Short Time delay available (30 cycles) without Instantaneous

  21. Selective Coordination - Good No overlapping fault current of individual devices. This is coordinated properly. In a perfect world this is great.

  22. Selective Coordination - BAD ATS Feeder Breaker 8 cycles to clear In this case, since it takes 8 cycles for the upstream breaker to clear the fault, a 3 cycle rated transfer switch is inadequate.

  23. What is our Competition Doing?

  24. ASCO Non UL Short Time Close & Withstand 100-400a 30k@30cycles 600-800a 42k@30cycles 1000-1200a 65k@30cycles 1600-3000a 85k@30cycles 4000a* 100k@30cycles * ATS only 6 8. With fuses only

  25. News regarding Cummins Power Generation Page 2 Mechanism (HEM), designed to ride through a fault condition undamaged and retain its capability to carry 100 percent of the rated load. Magnetic forces developed during a fault cause a typical transfer switch's contacts to blow open, producing an electrical explosion that often results in extensive internal damage to the switch, requiring replacement of contacts, arc chutes and, in some cases, the controller. In contrast, the HEM uses that same magnetic energy to hold the contacts closed during a fault, virtually eliminating arcing, contact damage and performance degradation. It can survive multiple faults of the specified magnitude - listed on the nameplate as the withstand and closing current ratings (WCR) - and continue to carry the rated current without overheating. This proprietary Cummins Power Generation technology means that there will be no costly repairs or inconvenient downtime after a fault. "Cummins Power Generation is proud to be the first manufacturer of transfer switches proven to survive a fault condition and to continue to operate at full load without repair," said Rich Scroggins, ATS product manager of Cummins Power Generation. "This ability gives consulting engineers more design flexibility in addressing requirements, and potentially to lower costs by using fewer transfer switches.“ Underwriters Laboratories (UL) is a leading safety testing and certification organization that has conducted product safety testing for nearly 115 years. On electrical products, the UL mark designates products that have been certified for safety regarding foreseeable hazards that include electric shock, fire and mechanical hazards. 2009 News Releases June 12, 2009 Cummins Power Generation Transfer Switches First With UL-Listed 30­Cycle Ratings MINNEAPOLIS, MINNESOTA – Series OHPC and CHPC PowerCommand® automatic transfer switches from Cummins Power Generation Inc. are the industry's first transfer switches to achieve UL-listed 10-cycle and 30-cycle withstand and closing (short-time) ratings. The OHPC open transition and CHPC closed transition switches demonstrated unprecedented short-time ratings of 25 kA at 10 cycles for 125 to 260-amp switches, 30 kA at 30 cycles for 300 to 600 amps, and 50 kA at 30 cycles for 800-amp switches in UL tests. The switches continued to operate safely at full load, even after testing. The UL listing provides consulting and specifying engineers independent assurance that the OHPC and CHPC transfer switches offer the industry's highest performance level, particularly for standby power systems requiring selective coordination. As defined by the 2008 edition of the National Electrical Code (NEC), selective coordination is mandatory for emergency and legally required electrical systems in buildings where life safety is paramount, including hospitals, health care facilities, emergency shelters and high-rise buildings with multiple elevators. NEC 2008 also requires selective coordination for critical operation power systems (COPS) in secure buildings such as banks, data centers, embassies and government offices. Selective coordination localizes an overcurrent condition to restrict outages to the circuit or equipment being affected. It is achieved by selecting circuit breakers and transfer switches with timing and withstand characteristics that delay or prevent faults from tripping upstream overcurrent protection devices. Selective coordination requirements are more easily satisfied by specifying OHPC or CHPC switches rather than products without UL-listed short-time ratings. The ability of CHPC and OHPC transfer switches to withstand fault current for up to 30 electric cycles (one-half second) gives the consultant the flexibility to adjust the instantaneous time delay on the ATS overcurrent protection device to prevent upstream 2breakers from tripping unnecessarily. Both transfer switches feature Cummins Power Generation's innovative High Endurance http://www.cumminspower.com/en/about/news/2009/news-2009-9/ 8/12/2009 Although Cummins Power was first to the market with some sizes, this is all they’ve published so far.

  26. Short Time 1000-1200a 65k@30cycles 1600-3000a 85k@30cycles 4000a* 100k@30cycles Power Generation * ATS only So we’ve distilled the info and put the values into a table. The OHPC open transition and CHPC closed transition switches demonstrated unprecedented short-time ratings of 25 kA at 10 cycles for 125 to 260-amp switches, 30 kA at 30 cycles for 300 to 600 amps, and 50 kA at 30 cycles for 800-amp switches in UL tests. The switches continued to operate safely at full load, even after testing. 100-400a 30k@30cycles 600-800a 42k@30cycles Only the 800a we don’t match No Mention in the press release of bypass switches

  27. EATON CUTLER HAMMER Magnum Circuit Breaker based transfer switches. First mention of 30 cycle rating but only when used with upstream fuses ?? While inconclusive as to whether these type switches carry a UL 30 cycle close and withstand rating, it doesn’t seem as if they do without the inclusion of upstream fuses.

  28. G.E. Zenith To Our Knowledge, they presently publish nothing other than 3 cycle ratings.

  29. New Russelectric 30 Cycle Automatic Transfer Switchesand Bypass Isolation Switches

  30. Back Plate Assembly BACKPLATE: -increased thickness to 1.25” -added strength and stability • SIDE BARRIER: • 5/8” thk glass polyester • Greater arc & track resistance • Excellent flame resistance • Movable contact support

  31. Movable and Arcing Contact Springs Movable Arcing Contact Current Path Blow Open Force Stationary Contact Movable Main Contact Contact Design: Blow-off vs. Blow-on Blow-Off Contact Design: - Used for Interrupting High Fault Currents - Magnetic forces push contacts open - Used for 3 cycle devices - Contact springs - only force to withstand fault

  32. Contact Design: Blow-on • - Used for withstanding High Fault Currents • - Magnetic forces from fault increase pressure on contacts • Offset hinge point allows for rotation toward contacts • for blow on effect Contact Springs Hinge Point Force Main Contact Current Path Stationary Contact

  33. Russelectric 3 Cycle Design Blow-Off Design Single Arcing Contact Multiple Contact Fingers depending on amperage Main Contact Pad material: AgWC50 – Silver Tungsten Carbide Tungsten to reduce erosion Arcing Pad Material: AgW73 – Silver Tungsten Stationary Contact Pad material: AgWC50 – Silver Tungsten Carbide Contacts Rotate on Copper Hinge Block and Pin Assembly Metal Contact Holder Contact Comparison: 3 Cycle vs. 30 Cycle

  34. 30 Cycle Design Blow-On Design Arcing Contact Designed into each main contact – Copper Multiple Contact Fingers depending on amperage Main Contact Pad material: AgWC40 – Higher Silver Contact to prevent overheating Stationary Contact Pad material: AgC4 – 96% Silver, graphite to prevent welding during withstand Flexible Braided connectors – prevents overheating and hot spots Brush Movement in Main Contacts – Cleans contact pad every operation Molded Contact Holder - Contains arc - BMC thermoset material - Withstands heat - Great arc and track resistance

  35. CROSSARM MECHANISM • Made from 1.125 Square Steel Stock • Overcenter Spring Mechanism to Latch Contacts Closed and Open Utilizes same mechanics as the 3 cycle switch – Heavier spring

  36. OPERATORS • Open Transition Switches with EMO • Reliability of Motor Operators

  37. Removal of Isolation Handle • Single Handle is for Bypass Operation • 800A Rollout Switch Cradle rolls out on Ground – not on rails

  38. Gearbox Rack-in Mechanism • Access Rack-in Shaft through door - only in Bypass Mode • Position Indicator Window - Connected - Connected – Bypassed - Test - Isolated • Gearbox needed for Increased Spring Pressure • - Must Pass the “Liz Test”

  39. Secondary Disconnect • Located on left Side of Cubicle for accessibility • Allows for Test Position • Incorporated into Side Guide-Rail

  40. Guide Plates • Used for Left to Right Alignment • Prevents Rollout Switch from jumping or shifting during fault

  41. Shutter Design (Optional) Shutter Closed (switch in test position or isolated) Shutter Open (switch racked-in)

  42. Finger Clusters • Added Spring Pressure for Clamping • Increased Contact Surface Area • Withstood 100KA for 3 Cycles and 85KA for 30 Cycles - without a scratch 2500A Cluster 800A Cluster

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