Often Overlooked Problems When Applying Automatic Transfer Switches in Institutions

1. Often Overlooked Problems When Applying Automatic Transfer Switches in Institutions David G. Loucks, P.E. DaveGLoucks@eaton.com Eaton Corporation

2. We Will Cover: • Changes Forcing Us To Rethink Our Designs • Utility • Our Facilities • Need To Improve System Reliability • Selectivity / Coordination • Withstand / Short-Time • X/R ratings • “Optional Systems” • Unique Add-On Solutions

3. Changes: Background Survey • How to Insure You Have It • How to Improve What You Have • Electrical Utility Grid reliability or lack thereof • Increased dependency in hospital on computer based devices • Aging infrastructure – capacity, reliability, maintenance cost, parts availability, safety • Arc flash • Saving money; Reducing energy consumptions

4. Changes: Background Survey • Utility Grid reliability or lack thereof • Increased dependency in hospital on computer based devices • Aging infrastructure – capacity, reliability, maintenance cost, parts availability, safety • Arc flash • Saving money; Reducing energy consumptions Important Topics, but won’t be covered today

5. Okay, So What Affects Electrical Grid Reliability? • Surge Protection and Grounding • Harmonics, Power Factor Correction & Electromagnetic interference • Back-up Power and Voltage Stabilization (Power Conditioning) • Monitoring and Diagnostic Systems (Early Warning) • Human Issues

6. During Today’s Webinar We Will Focus on This Issue • Surge Protection and Grounding • Harmonics, Power Factor Correction & Electromagnetic interference • Back-up Power and Voltage Stabilization (Power Conditioning) • Monitoring and Diagnostic Systems (Early Warning) • Human Issues

7. How To Recognize You Have a Voltage Stability Problem • Problems / Symptoms – what problems can occur • Computer reboots / lock-ups • Lights flickering • Loss of revenue • User inconvenience & rescheduling • Diagnostic equipment recalibration requirements • Lost or destroyed samples / data / research • (Medical) Increased patient suffering • Data integrity • HVAC / comfort • Safety (biohazard, falls) • Increased equipment repair costs

8. What Causes Voltage Instability? • Miscoordination of protective equipment • System overload • (Hospital) Lack of isolation panels – wet areas, gases • Utility outages / natural disaster (i.e. Northeast blackout; weather issues; lack of fuel) • Human error • Bad batteries / battery failure • Poor maintenance

9. Since our discussion deals with generators and ATS, we will cover: • Miscoordination of protective equipment • System overload • (Hospital) Lack of isolation panels – wet areas, gases • Utility outages / natural disaster (i.e. Northeast blackout; weather issues; lack of fuel) • Human error • Bad batteries / battery failure • Poor maintenance

10. TESTING STANDARDS • UL1008 ATS Standard • UL489 MCCB Standard • UL1087 MCS Standard • UL1066 PCB Standard • UL891 LV Switchboard Standard • UL1558 LV Switchgear Standard • Q.A. CERTIFICATE • 50 Operations Minimum • Internal Production Standard

11. Low Voltage Power Circuit Breakers • ANSI C37.13 IEEE Standard for Low-Voltage AC Power Circuit Breakers Used in Enclosures • ANSI C37.16 Low-Voltage Power Circuit Breakers and AC Power Circuit Protectors - Preferred Ratings, Related Requirements, and Application Recommendations • ANSI C37.17 Trip Devices for AC and General Purpose DC Low-Voltage Power Circuit Breakers

12. Healthcare: JCAHO EC.2.10.4.1 …testing each generator 12 times a year with testing intervals not less than 20 days and not more than 40 days. These tests shall be conducted for at least 30 continuous minutes under a dynamic load that is at least 30% of the nameplate rating of the generator. If diesel-powered generators do not meet the minimum exhaust gas temperatures as determined during these tests, they shall be exercised for 30 continuous minutes at the intervals described above with available EPSS load, and exercised annually with supplemental loads of • 25 percent of nameplate rating for 30 minutes, followed by • 50 percent of nameplate rating for 30 minutes, followed by • 75 percent of nameplate rating for 60 minutes for a total of two continuous hours.

13. Other Applicable Standards • NFPA 99 • “Standards for Healthcare Facilities” • NFPA 110 • “Standards for Emergency and Standard Power Systems” • IEEE 1547 Utility Interconnect Standard (NEW) • Only applies if 10 MW or smaller (if larger, custom utility review required) • Only if “Make-Before-Break” closed transition for more than 1/10 second with utility

14. Transfer Switches for Emergency Systems • NEC Article 700 • Legally required to automatically provide alternate power, within 10 seconds of power interruption, to a number of prescribed functions essential for the safety of human life

15. Transfer Switches for Legally Required Standby Systems • NEC Articles 701 • Intended to automatically supply power to selected loads (other than those classed as emergency systems) in the event of failure of the normal source • Power available 60 seconds after outage

16. Transfer Switches for Optional Standby Systems • NEC Articles 702 • Intended to supply power, either automatically or non-automatically to selected loads other than those classed as emergency or legally required standby

17. Miscoordination • Selective Coordination • Upstream and downstream breakers • Phase • Ground • ATS withstand • Magnitude • Duration • Asymmetry (X/R) • ATS short-time rating

18. Healthcare Ground Fault Protection -- NEC 517.17 • … an additional step of ground-fault protection shall be provided in the next level of feeder disconnecting means downstream toward the load. • The additional levels of ground-fault protection shall not be installed as follows: • (1) On the load side of an essential electrical system transfer switch • (2) Between the on-site generating unit(s) described in 517.35(B) and the essential electrical system transfer switch(es)

19. Healthcare Ground Fault Protection – UL 1008 Article 20 Exception No. 3: Ground-fault protection need not be provided on that side of a transfer switch intended for connection to the alternate source, provided that the transfer switch is marked in accordance with 41.50.

20. 2002 NEC 517.17 Ground-Fault Protection B) Selectivity. Ground-fault protection for operation of the service and feeder disconnecting means shall be fully selective such that the feeder device and not the service device shall open on ground faults on the load side of the feeder device. A six-cycle minimum separation between the service and feeder ground-fault tripping bands shall be provided.

21. UL 1008 - ATS Withstand and Fault Closing Ratings • Transfer switch must withstand the designated level of short-circuit current until the overcurrent protective devices open (unless integral to the design) • Test current specified in terms of the required symmetrical amperes and the power factor of the test current • Test current maintained for at least three cycles (50 ms) • Same sample used for the closing test

22. Definitions Interrupting capacity The Maximum Short Circuit Current that the Device Can Safely Interrupt • Short-time current rating Defines the Ability of the Device to Remain Closed for a Time Interval Under High Fault Current Conditions

23. NEC 517.17 Says Your Upstream Device Must Remain Closed For… B) Selectivity. Ground-fault protection for operation of the service and feeder disconnecting means shall be fully selective such that the feeder device and not the service device shall open on ground faults on the load side of the feeder device. A six-cycle minimum separation between the service and feeder ground-fault tripping bands shall be provided.

24. How Long Does UL1008 Say ATS Must Withstand Fault? UL1008 34 Withstand 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 overcurrent protective devices open or for a time as designated in 34.3. At the conclusion of the test…. 34.5 The test current is to be maintained for at least 3 cycles (50 ms). See 41.20.

25. To Achieve Selectivity, You Need To Delay Upstream Device • A six-cycle separation between service and feeder means that at any current level, the downstream device must clear the fault 6-cycles (0.1 sec) faster than the upstream device. • If the fault current is high, the downstream device might be clearing it in 0.02 seconds (~1 cycle) • That means the upstream must delay tripping for 6+1 = 7 cycles = 0.12 seconds

26. Can an ATS Withstand a Fault for 0.12 seconds? • Not if the switch is only UL1008 rated for 3-cycles. • “Houston, we have a problem…”

27. Fast Forward to 2002:New UL1008 41.20.1 Short-Time 3 Cycle ATS 41.20 A transfer switch tested for three cycles shall be marked, When protected by a circuit breaker without an adjustable short-time response only or by fuses this transfer switch is rated for use on a circuit capable of delivering not more than ____ rms symmetrical amperes, ____ volts maximum.² The value of amperes shall correspond to the symmetrical values given in 41.23. See 34.5 and 34.6. Revised 41.20 effective September 18, 1997 Short-Time Rated ATS 41.20.1 A transfer switch determined to comply with the Short-Time Current Rating Test, Section 36A, shall be marked, ²This transfer switch is intended for use with an upstream circuit breaker having a short-time rating not exceeding _______ volts at ______ amperes, for _______ cycles (seconds).² The values of amperes, and cycles (seconds) shall be as specified by the manufacturer. 41.20.1 added January 9, 2002

28. Choose Carefully • Make sure your ATS can survive 6-cycles of fault current • UL1008 ATS Standard • All are tested to 3-cycles at their withstand current • UL1008 28.1-28.6 says that ATS tested to 6 times rated current for 10 cycles • If your calculated fault current is greater than 6x ATS rating, you need an ATS with a short-time rating • May also need to review your distribution equipment • UL891 Switchboards/UL489 Devices (3-cycle rated) • UL1558 Switchgear/UL1066 Devices (30-cycle rated)

29. Power Factor

30. X/R Ratio

31. X/R Ratio - ANSI Test X/R = 0, PF = 1.0 (symmetry) X/R = 6.6, PF = 0.15 (asymmetry) Current in Per Unit 20 15 10 5 0 0 1 2 3 4 -5 -10 Time in Cycles

32. X/R Ratio - Application Data UL1008 takes these values into consideration, so ATS is okay …but when specifying generator breaker make sure you are aware of these derating factors

33. X/R Ratio - Application Data Peak Multiplication Factor Calculations Z X  R • X/R = tan  • = tan-1(X/R) • R/Z = cos  = PF • = cos-1(PF) X/R = tan(cos-1(PF)) PF = cos(tan-1(X/R))

34. LVPCB Application – Large Source KVA G Utility 4000 A PCB 1600 A PCB 1600 A PCB 1600 A ATS 800 A PCB 600 A MCB At 2500KVA I (sc) = 64,300A

35. Typical Distribution System System -- Possible Fault Locations -- Gen 1 Utility > 1000 A > 150 VLN CB1 CB2 F1 S1 S2 control logic F2 F3

36. Fault Cleared by Upstream Device Gen 1 Utility > 1000 A > 150 VLN CB1 CB2 F1 S1 S2 control logic

37. Fault Cleared by Upstream Device Gen 1 Utility > 1000 A > 150 VLN CB1 CB2 F1 S1 S2 control logic

38. Fault Cleared by Upstream Device Gen 1 Utility > 1000 A > 150 VLN CB1 CB2 F1 S1 S2 control logic

39. Fault Cleared by Upstream Device Gen 1 Utility > 1000 A > 150 VLN Trips! CB1 CB2 F1 S1 S2 control logic

40. Fault Cleared by Upstream Device Gen 1 Utility > 1000 A > 150 VLN CB1 CB2 F1 S1 S2 control logic

41. Fault Cleared by Upstream Device Gen 1 Utility > 1000 A > 150 VLN CB1 CB2 F1 S1 S2 control logic System Functioning Normally

42. Fault Moved to Load Side of ATS Gen 1 Utility > 1000 A > 150 VLN CB1 CB2 S1 S2 control logic F2

43. Fault Moved to Load Side of ATS Gen 1 Utility > 1000 A > 150 VLN CB1 CB2 S1 S2 control logic F2

44. Fault Moved to Load Side of ATS Gen 1 Utility > 1000 A > 150 VLN CB1 CB2 S1 S2 control logic F2

45. Fault Moved to Load Side of ATS Gen 1 Utility > 1000 A > 150 VLN Trips! CB1 CB2 S1 S2 control logic F2

46. Fault Moved to Load Side of ATS Gen 1 Utility > 1000 A > 150 VLN CB1 CB2 S1 S2 control logic F2

47. Fault Moved to Load Side of ATS Gen 1 Utility > 1000 A > 150 VLN CB1 CB2 S1 S2 control logic F2

48. Fault Moved to Load Side of ATS Gen 1 Utility > 1000 A > 150 VLN Trips! CB1 CB2 S1 S2 control logic F2

49. Fault Moved to Load Side of ATS Gen 1 Utility > 1000 A > 150 VLN CB1 CB2 S1 S2 control logic F2 System Functioning Normally, but after F2 fixed, CB1 and CB2 must be reset and reclosed

50. Alternate Design: Communications with Upstream Overcurrent Device Gen 1 Utility > 1000 A > 150 VLN CB1 Phase CB2 CB2 trip unit S1 S2 control logic L.O. F2