ARC Flash Assessment

194 Pages·2017·1.82 MB·English

by  Carollo Engineers, Inc.

This document is released for City of Oxnard
the purpose of information
exchange review and planning Public Works Integrated Master Plan
only under the authority of
WATER
Tracy Anne Clinton,
September 2017, State of
PROJECT MEMORANDUM 2.6
California, PE No. 48199 and
ARC FLASH ASSESSMENT
Christopher Alan Carvalho,
September 2017, State of
California, PE No. E20740 REVISED FINAL DRAFT
September 2017

2700 YGNACIO VALLEY ROAD, SUITE 300 • WALNUT CREEK, CALIFORNIA 94598 • P. 925.932.1710 • F. 925.930.0208
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PREFACE
The analysis and evaluations contained in these Project Memorandum (PM) are based on
data and information available at the time of the original date of publication,
December 2015. After development of the December 2015 Final Draft PMs, the City
continued to move forward on two concurrent aspects: 1) advancing the facilities planning
for the water, wastewater, recycled water, and stormwater facilities; and 2) developing
Updated Cost of Service (COS) Studies (Carollo, 2017) for the wastewater/collection
system and the water/distribution system. The updated 2017 COS studies contain the most
recent near-term Capital Improvement Projects (CIP). The complete updated CIP based
on the near-term and long-term projects is contained in the Brief History and
Overview of the City of Oxnard Public Works Department’s Integrated Planning
Efforts: May 2014 – August 2017 section.
At the time of this Revised PWIMP, minor edits were also incorporated into the PMs.
Minor edits included items such as table title changes and updating reports that were
completed after the December 2015 original publication date.
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City of Oxnard

Public Works Integrated Master Plan

WATER

PROJECT MEMORANDUM 2.6
ARC FLASH ASSESSMENT

TABLE OF CONTENTS

Page No.
1.0 INTRODUCTION ........................................................................................................1
1.1 Project Memorandums (PMs) Used for Reference ........................................ 1
1.2 Other Reports Used for Reference ................................................................ 1
1.3 Short Circuit Study ......................................................................................... 1
1.4 Arc Flash Study ............................................................................................. 2
2.0 SHORT CIRCUIT STUDY ..........................................................................................2
2.1 Source Data ................................................................................................... 3
2.2 Assumptions .................................................................................................. 5
2.3 One-line Diagrams ......................................................................................... 6
2.4 Short Circuit Reports ..................................................................................... 6
3.0 PROTECTIVE DEVICE COORDINATION STUDY ....................................................9
3.1 Source Data ................................................................................................... 9
3.2 Time-Current Curves ..................................................................................... 9
3.3 Coordination Results ................................................................................... 10
4.0 ARC FLASH STUDY ................................................................................................1 6
4.1 Source Data ................................................................................................. 18
4.2 Arc Flash Summary ..................................................................................... 18
4.3 Arc Flash Hazard Mitigation Techniques ..................................................... 19
4.4 Arc Flash Hazard Labels ............................................................................. 20
5.0 MISCELLANEOUS FIELD INVESTIGATION FINDINGS .........................................2 0
5.1 General ........................................................................................................ 21
5.2 Blending Station 1........................................................................................ 21
5.3 Blending Station 2........................................................................................ 22
5.4 Blending Station 3........................................................................................ 22
5.5 Blending Station 4........................................................................................ 22
5.6 Blending Station 6........................................................................................ 22
5.0 MISCELLANEOUS FIELD INVESTIGATION FINDINGS .........................................2 0

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APPENDIX A ONE LINES
APPENDIX B1 SHORT CIRCUIT STUDY (MOMENTARY DUTY SUMMARY REPORT)
APPENDIX B2 SHORT CIRCUIT STUDY (INTERRUPTING DUTY SUMMARY REPORT)
APPENDIX B3 SHORT CIRCUIT STUDY (1/2 CYCLE SHORT-CIRCUIT SUMMARY
REPORT)
APPENDIX C TIME CURRENT CURVES
APPENDIX D ARC FLASH STUDY
APPENDIX E PROTECTION SETTINGS
APPENDIX F EQUIPMENT DATA

LIST OF TABLES

Table 1 Motor and Generator Reactance Multipliers .................................................... 6
Table 2 Operational Scenarios ................................................................................... 17
Table 3 Personal Protective Equipment (PPE) ........................................................... 17

LIST OF FIGURES

Figure 1 Example One-Line Diagrams ........................................................................... 7

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Project Memorandum 2.6
ARC FLASH ASSESSMENT
1.0 INTRODUCTION
The short circuit, coordination, and arc flash hazard studies contained in this report provide
information necessary for the safe and reliable operation and maintenance of the City of
Oxnard (City) water treatment and conveyance facilities’ electrical distribution system, and
to help them meet the safety requirements of NFPA 70E and OSHA 1910.132(d).
The studies in this report were performed using ETAP power system analysis software. The
data required to build the electrical system model was obtained from a combination of field
investigation, and as-built project documentation.
1.1 Project Memorandums (PMs) Used for Reference
The recommendations outlined in this PM include background from the following other PMs:
• PM 2.1 - Water System - Background Summary.
• PM 3.8 - Wastewater System - Arc Flash Assessment.
• PM 4.4 - Recycled Water System - Arc Flash Assessment.
1.2 Other Reports Used for Reference
The following codes and standards are referenced in this PM:
• NFPA 70 National Electric Code (NEC).
• NFPA 70E Standard for Electrical Safety in the Workplace.
• IEEE Standard 242 (IEEE Buff Book) - Recommended Practice for Protection and
Coordination of Industrial and Commercial Power Systems.
• IEEE 1584 - Guide for Performing Arc Flash Hazard Calculations.
1.3 Short Circuit Study
The objective of the Short Circuit Study is to verify that the electrical distribution equipment
at all the sites is rated to withstand and interrupt the short circuit currents that could result
from a fault in the electrical distribution system.
Section 2.0 identifies equipment that is not properly rated for the available short circuit
current. Protective Device Coordination Study.
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The Protective Device Coordination Study has been performed to achieve four objectives –
sensitivity, security, selectivity, and safety. Sensitivity refers to the degree of certainty that a
device will operate correctly under a fault. Security is the degree of certainty that a device
will not operate when there is no fault condition. Selectivity means that the protective device
closest to a fault trips before any upstream devices to clear the fault, isolating the resulting
outage to the smallest amount of equipment possible. Safety primarily applies to the arc
flash hazard and requires that protective devices operate as quickly as possible to reduce
incident energy.
The results of the study show that certain protective devices are not properly coordinated
and require adjustment. Section 3.0 identifies the protective devices which are not properly
coordinated.
1.4 Arc Flash Study
The objective of the Arc Flash Study is to provide information that allows plant staff to take
appropriate precautions when working on energized electrical equipment to reduce the
potential risk of injury from an arc flash event. The results of the Short Circuit and the
Protective Device Coordination Studies are used to calculate the incident energy and
hazard boundaries based upon NFPA 70E 2015 Edition and IEEE 1584 for equipment in
the electrical distribution system. OSHA regulations require that employers perform an
assessment of the workplace to identify arc flash hazards. Specifically,
Specifically, “The employer shall assess the workplace to determine if hazards are present,
or are likely to be present, which necessitate the use of personal protective equipment
(PPE). If such hazards are present, or likely to be present, the employer shall: Select, and
have each affected employee use, the types of PPE that will protect the affected employee
from the hazards identified in the hazard assessment; communicate selection decisions to
each affected employee; and select PPE that properly fits each affected employee.” [OSHA
1910.132(d)(1)]. The arc-flash labels provided with this study will help the plant to comply
with these regulations by identifying the PPE level and arc flash boundary at each piece of
equipment.
2.0 SHORT CIRCUIT STUDY
The objective of the Short Circuit Study is to verify that the electrical distribution equipment
in the facility is rated to withstand and interrupt the available short circuit currents that could
result from a fault in the electrical distribution system in accordance with NFPA 70 National
Electric Code (NEC), Article 110 Paragraph’s 110.9 and 110.10. The study results show
that the existing electrical distribution equipment is sufficiently rated for the worst-case short
circuit current with the exceptions of the following below:
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• Blending Station 1, North Power Building:
– The feeder breaker in the Main SWBD 1 for the Meter Shop Disconnect is not
properly rated for the available fault current.
• Blending Station 1, Desalter Building:
– The short circuit current rating for the Solar Control Cabinet could not be
determined and was assumed to be 5 kA. This assumed rating is not properly
rated for the available fault current.
– The Solar Inverter Disconnect is not properly rated for the available fault
current.
• Blending Station 6:
– The AH-101 disconnect switch is not properly rated for the available fault
current.
– The CU-101 disconnect switch is not properly rated for the available fault
current.
– The HP-101 disconnect switch is not properly rated for the available fault
current.
2.1 Source Data
The results of the Short Circuit Study are completely dependent on the information in the
electrical system model. As such, every effort has been made to obtain the most up-to-date
information available for all equipment covered under the scope of the study. In the future,
when changes are made to the electrical distribution system, the system model must be
updated and a new short circuit study performed based on the updated model.
2.1.1 Utility Contribution
The following values are the available fault current at the utility service entrance, as
provided by the utility in July 2015. Both the maximum and minimum fault current levels are
incorporated into the electrical system model in order to capture the worst case arc flash
event. It is important to note that utility fault current levels can change due to numerous
variables in the utility distribution and transmission system. This is why it is undesirable to
have equipment’s short circuit rating too close to the calculated short circuit values.
Blending Station 1 (Main Water Campus), 250 S. Hayes Ave
Southern California Edison (SCE) Structure # P5600632
SCE Meter #V349N-008970
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• Available 3-Phase Fault Current: 11,900 A, X/R Ratio: 3.14.
• Available Single Line-Ground Fault: 12,800 A, X/R Ratio: 3.51.
• Nominal Voltage: 480 V.
Blending Station 1 (Main Water Campus), 251 S. Hayes Ave
Southern California Edison (SCE) Structure # P5197918
SCE Meter #V349N-009102 and # V349N-012328
• Available 3-Phase Fault Current: 19,000 A, X/R Ratio: 4.88.
• Available Single Line-Ground Fault: 19,950 A, X/R Ratio: 5.34.
• Nominal Voltage: 480 V.
Blending Station 2, 1001 Richmond Ave
Southern California Edison (SCE) Structure # 1257095E
SCE Meter #259000-076122
• Available 3-Phase Fault Current: 14,020 A, X/R Ratio: 2.35.
• Available Single Line-Ground Fault: 14,940 A, X/R Ratio: 2.45.
• Nominal Voltage: 480 V.
Blending Station 3 (Main Water Campus), 1700 Solar Ave
Southern California Edison (SCE) Structure # P5554088
SCE Meter #259000-063295
• Available 3-Phase Fault Current: 24,293 A, X/R Ratio: 5.25.
• Available Single Line-Ground Fault: 26,093 A, X/R Ratio: 5.87.
• Nominal Voltage: 480 V.
Blending Station 4 3637 N. Rose Ave
Southern California Edison (SCE) Structure # P5438424
SCE Meter #259000-062333
• Available 3-Phase Fault Current: 10,400 A, X/R Ratio: 2.28.
• Available Single Line-Ground Fault: 11,010 A, X/R Ratio: 2.35.
• Nominal Voltage: 480 V.
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