260573 Short circuit coordination study arc flash hazard analysis.pdf

Denver Museum of Nature and Science: Education and Collections Facility klipp, a professional corporation Project number 2009.104 100% Construction Documents

SHORT CIRCUIT/COORDINATION STUDY/ARC FLASH HAZARD ANALYSIS

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SECTION 260573 - SHORT CIRCUIT/COORDINATION STUDY/ARC FLASH HAZARD ANALYSIS

PART 1 - GENERAL

1.1 RELATED DOCUMENTS

A. Drawings and general provisions of the Contract, including General and Supplementary Conditions and Division 01 Specification Sections, apply to this Section.

B. American National Standards Institute

1. ANSI C57.12.10: American National Standard for Transformers - 230 kV and Below 833/958 - 8333/10 417 kVA, Single-Phase, and 750/862 - 60 000/80 000/100 000 kVA, Three-Phase w/o Load Tap Changing; and 3750/4687 - 60 000/80 000 kVA with Load Tap Changing - Safety Requirements

2. ANSI C57.12.22: American National Standard for Transformers - Pad-Mounted, Compartmental-Type, Self-Cooled, Three-Phase Distribution Transformers with High-Voltage Bushings, 2500 kVA & Smaller: High-Voltage, 34 500 GrdY/19 920 V & Below; Low Voltage, 480 V & Below - Requirements

3. ANSI C57.12.40: American National Standard for Secondary Network Transformers - Subway and Vault Types (Liquid Immersed) - Requirements

C. The Institute of Electrical and Electronics Engineers, Inc.

1. IEEE 141: Recommended Practice for Electric Power Distribution for Industrial Plants (the Red Book)

2. IEEE 241: Recommended Practice for Electric Power Distribution for Commercial Buildings (the Gray Book) (ANSI)

3. IEEE 242: Recommended Practice for Protection and Coordination of Industrial and Commercial Power Systems (the Buff Book)

4. IEEE 399: Recommended Practice for Industrial and Commercial Power Systems Analysis (the Brown Book) (ANSI)

5. IEEE 620: Guide for the Presentation of Thermal Limit Curves for Squirrel Cage Induction Machines

6. IEEE 1015: Recommended Practice for Applying Low-Voltage Circuit Breakers Used in Industrial and Commercial Power Systems (the Blue Book)

7. IEEE C37.010: Application Guide for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis (ANSI)

8. IEEE C37.20.1: IEEE Standard for Metal-Enclosed Low-Voltage Power Circuit Breaker Switchgear (ANSI)

9. IEEE C37.46: American National Standard Specifications for Power Fuses and Fuse Disconnecting (ANSI)

10. IEEE C57.12.00: General Requirements for Liquid-Immersed Distribution, Power, and Regulating Transformers (ANSI)

11. IEEE C57.96: Guide for Loading Dry-Type Distribution and Power Transformers (ANSI)



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12. IEEE 1584 – Guide for Performing Arc-Flash Hazard Calculations

D. Insulated Cable Engineers Association, Inc.

1. ICEA P-32-382: Short-Circuit Characteristics of Insulated Cable 2. ICEA P-45-482: Short-Circuit Performance of Metallic Shielding & Sheaths

E. National Electrical Manufacturers Association

1. NEMA MG 1: Motors and Generators

F. The National Fire Protection Association (NFPA)

1. NFPA 70 – National Electrical Code, latest edition 2. NFPA 70E – Standard for Electrical Safety in the Workplace

1.2 SUMMARY

A. This Section includes computer-based, fault-current and Short Circuit/Coordination Study/Arc-Flash Hazard Analysis & Arc-Flash Hazard Analysis. Protective devices shall be set based on results of the protective device coordination study.

B. The contractor shall furnish an Arc Flash Hazard Analysis Study per the requirements set forth in NFPA 70E – Standard for Electrical Safety in the Workplace. The arc flash hazard analysis shall be performed according to the IEEE std. 1584-2002 equations that are presented in NFPA 70E-2009, Annex D.

C. The scope of the studies shall include all new distribution equipment supplied by the equipment Manufacturer under this contract as well as all directly affected existing distribution equipment at the customer facility.

1.3 ACTION SUBMITTALS

A. Product Data: For computer software program to be used for studies.

B. Other Action Submittals: The following submittals shall be made after the approval process for system protective devices has been completed. Submittals shall be in both digital and hard copy form.

1. Arc-Flash and Coordination-study input data, including completed computer program input data sheets.

2. Study and Equipment Evaluation Reports. 3. Study Report. 4. Tabulation of overcurrent protective device settings. 5. Arc-Flash labels for distribution equipment. 6. Incident energy & flash protection boundary calculations. 7. One-Line diagram.



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1.4 INFORMATIONAL SUBMITTALS

A. Qualification Data: For arc flash & coordination-study specialist.

B. Product Certificates: For coordination-study and fault-current-study computer software programs, certifying compliance with IEEE 399 & IEEE 1584 Guide To Performing Arc-Flash Calculations.

1.5 MAINTENANCE MATERIAL SUBMITTAL

A. Operation and Maintenance Data: Upon completion of project, submit electronic program file on CD for operation, and maintenance manuals. In addition to items specified in Division 01 Section "Operation and Maintenance Data," include the following:

1. Current-limitation curves for fuses with current-limiting characteristics. 2. Time-current coordination curves for overcurrent devices. 3. Coordination charts and tables and related data. 4. Overcurrent device settings report. 5. Electronic copy of study & report.

1.6 QUALITY ASSURANCE

A. Studies shall use computer programs that are distributed nationally and are in wide use. Software algorithms shall comply with requirements of standards and guides specified in this Section. Manual calculations are not acceptable.

B. Coordination-Study Specialist Qualifications: An entity experienced in the application of computer software used for studies, having performed successful studies of similar magnitude on electrical distribution systems using similar devices.

1. Professional engineer, licensed in the state where Project is located, shall be responsible for the study. All elements of the study shall be performed under the direct supervision and control of engineer.

C. Comply with IEEE 242, “Recommended Practice for Protection and Coordination of Industrial and Commercial Power Systems” for short-circuit currents and coordination time intervals.

D. Comply with IEEE 399 for general study procedures.

E. Comply with IEEE 1584 – Guide for performing Arc-Flash hazard calculations.

PART 2 - PRODUCTS

2.1 COMPUTER SOFTWARE DEVELOPERS

A. Computer Software Developers: Subject to compliance with requirements, provide products by one of the following:



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1. (ETAP software) by Operation Technology, Inc.

2.2 COMPUTER SOFTWARE PROGRAM REQUIREMENTS

A. Comply with IEEE 399.

B. Analytical features of fault-current-study computer software program shall include "mandatory," "very desirable," and "desirable" features as listed in IEEE 399.

C. Computer software program shall be capable of plotting and diagramming time-current-characteristic curves as part of its output. Computer software program shall report device settings and ratings of all overcurrent protective devices and shall demonstrate selective coordination by computer-generated, time-current coordination plots.

1. Optional Features:

a. Arcing faults.

PART 3 - EXECUTION

3.1 EXAMINATION

A. Examine Project overcurrent protective device submittals for compliance with electrical distribution system arc-flash & coordination requirements and other conditions affecting performance. Devices to be coordinated are indicated on Drawings.

1. Proceed with arc-flash & coordination study only after relevant equipment submittals have been assembled. Overcurrent protective devices that have not been submitted and approved prior to coordination study may not be used in study.

3.2 POWER SYSTEM DATA

A. Gather and tabulate the following input data to support coordination study:

1. Product Data for overcurrent protective devices provided for the project and involved in overcurrent protective device coordination studies. Use equipment designation tags that are consistent with electrical distribution system diagrams, overcurrent protective device submittals, input and output data, and recommended device settings.

2. Impedance of utility service entrance. 3. Electrical Distribution System Diagram: In hard-copy and electronic-copy formats,

showing the following:

a. Circuit-breaker and fuse-current ratings and types. b. Relays and associated power and current transformer ratings and ratios. c. Transformer kilovolt amperes, primary and secondary voltages, connection type,

impedance, and X/R ratios. d. Generator kilovolt amperes, size, voltage, and source impedance.



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e. Cables: Indicate conduit material, sizes of conductors, conductor material, insulation, and length.

f. Busway ampacity and impedance. g. Motor horsepower and code letter designation according to NEMA MG 1, “Motors

and Generators”.

4. Data sheets to supplement electrical distribution system diagram, cross-referenced with tag numbers on diagram, showing the following:

a. Special load considerations, including starting inrush currents and frequent starting and stopping.

b. Transformer characteristics, including primary protective device, magnetic inrush current, and overload capability.

c. Motor full-load current, locked rotor current, service factor, starting time, type of start, and thermal-damage curve.

d. Generator thermal-damage curve. e. Time-current-characteristic curves of devices indicated to be coordinated. f. Manufacturer, frame size, interrupting rating in amperes rms symmetrical, ampere

or current sensor rating, long-time adjustment range, short-time adjustment range, and instantaneous adjustment range for circuit breakers.

g. Manufacturer and type, ampere-tap adjustment range, time-delay adjustment range, instantaneous attachment adjustment range, and current transformer ratio for overcurrent relays.

h. Unit substation, Panelboards, switchboards, ampacity, and interrupting rating in amperes rms symmetrical.

3.3 FAULT-CURRENT STUDY

A. Calculate the maximum available short-circuit current in amperes rms symmetrical at circuit-breaker positions of the electrical power distribution system. The calculation shall be for a current immediately after initiation and for a three-phase bolted short circuit at each of the following:

1. Primary switch at service medium-voltage switchgear. 2. Unit substation 3. Switchgear and switchboard bus. 4. Motor-control center. 5. Distribution panelboard. 6. Branch circuit panelboard. 7. Dimming panels.

B. Study electrical distribution system from normal and alternate power sources throughout electrical distribution system for Project. Include studies of system-switching configurations and alternate operations that could result in maximum fault conditions.

C. Calculate momentary and interrupting duties on the basis of maximum available fault current.



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D. Calculations to verify interrupting ratings of overcurrent protective devices shall comply with IEEE 241, “Recommended Practice for Electric Power Systems in Commercial Buildings” and IEEE 242.

1. Transformers:

a. ANSI C57.12.22, “American National Standard for Transformers- Pad-Mounted, Compartmental-Type, Self-Cooled Three-Phase Distribution Transformers With High-Voltage Bushings, 2500 kVA and Smaller: High Voltage, 34 500 Grd Y/19 920 Volts and Below; Low Voltage, 480 Volts and Below”.

b. IEEE C57.96, “guide for loading dry-type distribution and power transformers”.

2. Low-Voltage Circuit Breakers: IEEE 1015, “Recommended Practice for Applying Low-Voltage Circuit Breakers Used in Industrial and Commercial Power Systems” and IEEE C37.20.1, “Standard for Metal-Enclosed Low-Voltage Power Circuit Breaker Switchgear”.

3. Low-Voltage Fuses: IEEE C37.46, “High Voltage Expulsion and Current-Limiting Type Power Class Fuses and Fuse Disconnecting Switches”.

E. Study Report:

1. Show calculated X/R ratios and equipment interrupting rating (1/2-cycle) fault currents on electrical distribution system diagram.

F. Equipment Evaluation Report:

1. For 600-V overcurrent protective devices, ensure that interrupting ratings are equal to or higher than calculated 1/2-cycle symmetrical fault current.

2. For devices and equipment rated for asymmetrical fault current, apply multiplication factors listed in the standards to 1/2-cycle symmetrical fault current.

3. Verify adequacy of phase conductors at maximum three-phase bolted fault currents; verify adequacy of equipment grounding conductors and grounding electrode conductors at maximum ground-fault currents. Ensure that short-circuit withstand ratings are equal to or higher than calculated 1/2-cycle symmetrical fault current.

3.4 COORDINATION STUDY

A. The electrical contractor shall be responsible for performing the coordination study using approved computer software program. Prepare a written report using results of fault-current study. Comply with IEEE 399.

1. Calculate the maximum and minimum 1/2-cycle short-circuit currents. 2. Calculate the maximum and minimum ground-fault currents.

B. Comply with IEEE 241 recommendations for fault currents and time intervals.

C. Transformer Primary Overcurrent Protective Devices:

1. Device shall not operate in response to the following:



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a. Inrush current when first energized. b. Self-cooled, full-load current at transformer. c. Permissible transformer overloads according to IEEE C57.96 if required by

unusual loading or emergency conditions.

2. Device settings shall protect transformers according to IEEE C57.12.00, for fault currents.

D. Conductor Protection: Protect cables against damage from fault currents according to ICEA P-32-382, “Short Circuit Characteristics of Insulated Cable”, ICEA P-45-482, Short-Circuit Performance of Metallic Shielding and Sheaths” and conductor melting curves in IEEE 242. Demonstrate that equipment withstands the maximum short-circuit current for a time equivalent to the tripping time of the primary relay protection or total clearing time of the fuse. To determine temperatures that damage insulation, use curves from cable manufacturers or from listed standards indicating conductor size and short-circuit current.

E. Coordination-Study Report: Prepare a written report indicating the following results of coordination study:

1. Tabular Format of Settings Selected for Overcurrent Protective Devices:

a. Device tag. b. Relay-current transformer ratios; and tap, time-dial, and instantaneous-pickup

values. c. Circuit-breaker sensor rating; and long-time, short-time, and instantaneous

settings. d. Fuse-current rating and type. e. Ground-fault relay-pickup and time-delay settings.

2. Coordination Curves: Prepared to determine settings of overcurrent protective devices to achieve selective coordination. Graphically illustrate that adequate time separation exists between devices installed in series, including power utility company’s upstream devices. Prepare separate sets of curves for the switching schemes and for emergency periods where the power source is local generation. Show the following information:

a. Device tag. b. Voltage and current ratio for curves. c. Three-phase and single-phase damage points for each transformer. d. No damage, melting, and clearing curves for fuses. e. Cable damage curves. f. Transformer inrush points. g. Maximum fault-current cutoff point.

F. Completed data sheets for setting of overcurrent protective devices.

G. Arc Flash Hazard Analysis

1. Study

a. The arc flash hazard analysis shall be performed according to the IEEE std. 1584-2002 equations that are presented in NFPA70E-2009, Annex D.



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b. The flash projection boundary and the incident energy shall be calculated at all significant locations in the electrical distribution system (switchboards, switchgear, motor-control centers, panelboards, busway and splitters) where work could be performed on energized parts.

c. The Arch-Flash Hazard Analysis shall include all significant locations in the 13.2 Kv, 480 volt, and 208 volt systems fed from transformers equal to or greater than 30 KVA.

d. Safe working distances shall be based upon the calculated arc flash boundary considering an incident energy of 1.2 cal/cm2 .

e. The short circuit calculations and the clearing times of the phase overcurrent devices will be retrieved from the short-circuit and coordination study model. Ground overcurrent relays should not be taken into consideration when determining the clearing time when performing incident energy calculations.

f. The short-circuit calculations and the corresponding incident energy calculations for multiple system scenarios must be compared and the greatest incident energy must be uniquely reported for each equipment location. Calculations must be performed to represent the maximum and minimum contributions of fault current magnitude for all normal and emergency operation conditions. The minimum calculation will assume that the utility contribution is at a minimum and will assume a minimum motor contribution (all motors off). Conversely, the maximum calculation will assume a maximum contribution from the utility and will assume the maximum amount of motors to be operation. The incident energy calculations must consider the accumulation of energy over time when performing arc flash calculations on buses with multiple sources. Iterative calculations must take into account the changing current contributions, as the sources are interrupted or decremented with time. Fault contribution from motors and generators should be decremented as follows:

1) Fault contribution from induction motors should not be considered beyond 3-5 cycles.

2) Fault contribution from synchronous motors and generators should be decayed to match the actual decrement of each as closely as possible (e.g. contributions from permanent magnet generators will typically decay from 10 per unit to 3 per unit after 10 cycles).

g. For each equipment location with a separately enclosed main device (where there is adequate separation between the line side terminals of the main protective device and the work location), calculations for incident energy and flash protection boundary shall include both the line and load side of the main breaker.

h. When performing incident energy calculations on the line side of a main breaker the line side and load side contributions must be included in the fault calculation.

i. Mis-coordination shall be checked amongst all devices within the branch containing the immediate protective device upstream of the calculation location and the calculation shall utilize the fastest device to compute the incident energy for the corresponding location.

j. Arc-Flash calculations shall be based on actual overcurrent protective device clearing time. Maximum clearing time shall be capped at 2 seconds based on IEEE std. 1584-2002 section B.1.2. Where it is not physically possible to move outside of the flash protection boundary in less than 2 seconds during an arc flash event, a maximum clearing time based on the specific location shall be utilized.



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2. Report Shall include :

a. Arcing fault magnitude b. Protective device clearing time c. Duration of arc d. Arc-Flash boundary e. Working distance f. Incident energy g. Hazard Risk Category h. Recommendations for arc-flash energy reduction

H. Arc-Flash warning labels

1. Provide an Arc-Flash Hazard Analysis 3.5 in x 5in. thermal transfer type label of high adhesion polyester for each work location analyzed.

2. All labels will be based on recommended overcurrent device settings and will be provided after the results of the analysis have been presented to the owner and after any system changes, upgrades or modifications have been incorporated in the system.

3. The label shall include the following information, at a minimum:

a. Location designation b. Nominal voltage c. Flash protection boundary d. Hazard risk category e. Incident energy or energy range corresponding to reported Hazard risk category. f. Working distance g. PPE level h. Engineering report number, revision number and issue date.

4. Labels shall be machine printed, with no field markings. 5. Arc-Flash labels shall be provided in the following manner and all labels shall be based

on recommended overcurrent device settings.

a. For each 600, 480 and applicable 208 volt panelboard, one arc flash label shall be provided.

b. For each low voltage switchboard, one arc flash label shall be provided. c. For each switchgear, one arc flash label shall be provided. d. For medium voltage switches, one arc flash label shall be provided.

6. Labels shall be field installed by the contractor.

I. Arc Flash Training

1. The contractor of the Arc Flash Hazard Analysis shall train the owner’s qualified electrical personnel of the potential arc flash hazards associated with working on energized equipment (minimum of 4 hours). The training shall be certified for continuing education units (CEUs) by the International Association for Continuing Education Training (IACET) or equivalent.

END OF SECTION 260573