SECTION 16011 ELECTRICAL STUDIES

This spec was part of the Des Plaines, IL River WRF project that bid Feb 26, 2015.


SECTION 16011 ELECTRICAL STUDIES


PART 1 GENERAL

1.1 RELATED REQUIREMENTS

A. Applicable requirements of Division 0 and Division 1 shall govern work in this Section.

1.2 SCOPE

A. The contractor shall retain the services of an independent third party firm to perform a short circuit, study, a protective device coordination study, and arc flash study.

B. The studies shall be submitted to the Design Engineer prior to receiving final approval of the distribution equipment shop drawings and/or prior to release of equipment for manufacture. If formal completion of the studies may cause delay in equipment manufacture, approval from the Engineer may be obtained for a preliminary submittal of sufficient study data to ensure that the selection of device ratings and characteristics will be satisfactory.

C. The studies shall include all portions of the electrical distribution system from the building’s normal power source or sources down to and including the smallest adjustable trip circuit breaker in the distribution system. Normal system connections and those which result in maximum fault conditions shall be adequately covered in the study.

D. The firm should be experienced in low, and medium, voltage power system evaluations. The studies shall be performed, stamped and signed by a registered professional engineer in the State of Wisconsin or Illinois. Credentials of the individual(s) performing the study and background of the firm shall be submitted to the Engineer for approval prior to start of the work. A minimum of five (5) years experience in power system analysis is required for the individual in charge of the project.

E. The firm performing the study should demonstrate capability and experience to provide assistance during start up as required.

1.3 DATA COLLECTION FOR THE STUDIES

A. The contractor shall collect and provide the required data for preparation of the studies. The Engineer performing the system studies shall furnish the Contractor with a listing of the required data immediately after award of the contract.

B. The Contractor shall expedite collection of the data to assure completion of the studies as required for final approval of the distribution equipment shop drawings and/or prior to release of the equipment for manufacture.

C. The Contractor is warned against the use of default generic device/equipment values that are available from the analysis software. Instead, the Contractor’s study shall use project-specific device data.

1.4 SUBMITTALS

A. Third party qualifications.  Submit qualifications of individual(s) who will perform the work for approval prior to commencement of the studies.

B. Draft report.  Submit a draft of the study to Engineer for review prior to delivery of the study to the Owner.

C. Final study report.
1. Make all additions or changes as required by the reviewer.
2. Provide studies in conjunction with equipment submittals to verify equipment ratings required.
3. The results of the power system study shall be summarized in final reports.  Six
(6) bound sets of the final report shall be submitted.

D. The report shall include the following sections:
1. Field study findings.
2. Descriptions, purpose, and scope of the study.
3. Tabulations of circuit breaker, fuse and other protective device ratings versus calculated short circuit duties, and commentary regarding same.
4. Protective device time versus current coordination curves, tabulations of relay and circuit breaker trip settings, fuse selection, and commentary regarding same.
5. Fault  current  calculations  including  a  definition  of  terms  and  guide  for interpretation of computer printout.
6. Print-out of the Arc-Flash labels to be applied to all equipment identified by NFPA-70E.

1.5 POWER COMPANY APPROVAL

A. Where required, copies of the final report shall be submitted to the power company for their review and Approved copies of the report shall be submitted to the Design Engineer.

1.6 QUALITY ASSURANCE

A. Reference standards listed in the IEEE “Buff Book”, latest edition.

B. Reference the equipment requiring Arc-Flash labeling in Article 400 of NFPA-70E.

C. The short circuit study shall be performed with the aid of a computer program and shall be In accordance with the latest applicable IEEE and ANSI standards.


PART 2 PRODUCTS

A. Not used.

PART 3 EXECUTION

3.1 SHORT CIRCUIT STUDY AND PROTECTIVE DEVICE COORDINATION STUDY

A. In the short circuit study, provide calculation methods and assumptions, the base per unit quantities selected, one-line diagrams, source impedance data including power company system characteristics, typical calculations, and recommendations. Calculate short circuit interrupting and momentary (when applicable) duties for an assumed 3-phase bolted fault at each supply switchgear lineup, low voltage switchgear lineup, distribution panelboard, pertinent branch circuit panelboard, and other significant locations throughout the system. Provide a ground fault current study for the same system areas, including the associated zero sequence impedance data. Include in tabulations fault impedance, X to R ratios, asymmetry factors, motor contribution, short circuit KVA, and symmetrical and asymmetrical fault currents.

B. In the protective device coordination study, provide time-current curves graphically indicating the coordination proposed for the system, centered on conventional, full-size, log-log forms. Include with each curve sheet a complete title and one-line diagram with legend identifying the specific portion of the system covered by that particular curve sheet. Include a detailed description of each protective device identifying its type, function, manufacturer, and time-current characteristics. Tabulate recommended device tap, time dial, pickup, instantaneous, and time delay settings.

C. Include on the curve sheets power company relay and fuse characteristics, system medium-voltage equipment relay and fuse characteristics, low-voltage equipment circuit breaker trip device characteristics, pertinent transformer characteristics, pertinent transformer characteristics, pertinent motor and generator characteristics, and characteristics of other system load protective devices. Include at least all devices down to largest branch circuit and largest feeder circuit breaker in each motor control center, and main breaker in branch panelboards.

D. Include all adjustable settings for ground fault protective devices. Include manufacturing tolerance and damage bands in plotted fuse characteristics. Show transformer full load and 150, 400, or 600 percent currents, transformer magnetizing inrush, ANSI transformer withstand parameters, and significant symmetrical and asymmetrical fault currents. Terminate device characteristic curves at a point reflecting the maximum symmetrical or asymmetrical fault current to which the device is exposed.

E. Select each primary protective device required for a delta-wye connected transformer so that its characteristic or operating band is within the transformer characteristics, including a point equal to 58 percent of the ANSI withstand point to provide secondary line-to- ground fault protection. Where the primary device characteristic is not within the transformer characteristics, show a transformer damage curve. Separate transformer primary protective device characteristic curves from associated secondary device characteristics by a 16 percent current margin to provide proper coordination and protection in the event of secondary line-to-line faults. Separate medium-voltage relay characteristic curves from curves for other devices by at least a 0.4-second time margin.

F. Include complete fault calculations as specified herein for each proposed and ultimate source combination. Note that source combinations may include present and future supply circuits, large motors, or generators as noted on Drawing one-lines.

G. Utilize equipment load data for the study obtained by the Contractor from Contract Documents, including Contract Addendums issued prior to bid openings.

H. Include fault contribution of all motors in the study. Notify the Engineer in writing of circuit protective devices not property rated for fault conditions.

I. Include phase and ground coordination of the standby  generator  protective  devices. Show the generator decrement curve and damage curve along with the operating characteristic of the protective devices. Obtain the information from the generator manufacturer and include the generator actual impedance value, time constants  and current boost data in the study. Do not use typical values for the generator.

J. Evaluate proper operation of the ground relays in 4-wire distributions with more than one main service circuit breaker, or when generators are provided, and discuss the neutral grounds and ground fault current flows during a neutral to ground fault.

K. For motor control circuits, show the MCC full-load current plus symmetrical and asymmetrical of the largest motor starting current to ensure protective devices will not trip major or group operation.

3.2 ARC FLASH HAZARD ANALYSIS/STUDY

A. The arc flash hazard analysis shall be performed to the IEEE 1584 equations that are presented in NFPA70E-2004, Annex D.

B. The flash protection boundary and the incident energy shall be calculated at all significant locations in the electrical distribution system (switchgear, panelboards, busway and splitters) where work could be performed on energized parts.

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

D. When appropriate, 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.

E. 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 operating 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 operating.

F. 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 (as required per above), the line side and load side contributions must be included in the fault calculation.

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

J. Arc Flash calculations shall be based on actual overcurrent protective device clearing time. Maximum clearing time will be capped at 2 seconds based on IEEE 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.

K. The Contractor shall affix each Arc-Flash label to the appropriate equipment, following approval of the ELECTRICAL STUDIES submittal.

3.3 ELECTRICAL STUDIES OUTLINE:

Table of Contents for Des Plaines River Wastewater Treatment Facility Dryer Building:

I. Overview
II. Short Circuit Study
SC-1. Purpose
SC-2. Explanation of Data
SC-3. Assumption(s)
SC-4. Analysis of Results
SC-5. Recommendations
SC-6. DAPPER Fault Analysis Input Report
SC-7. DAPPER Fault contribution Complete Report
- WWTF Normal Operation (Generator Off)
- WWTF Emergency Operation (Generator On)


III. Protective Device Coordination Study PDC-1. Purpose
PDC-2. Explanation of Data PDC-3. Assumption(s) PDC-4. Analysis of Results PDC-5. Recommendations
PDC-6. CAPTOR Results – Existing
PDC-7. CAPTOR Results – With All Recommendations PDC-8. Example Station

IV. Arc Flash Hazard Study
ARC-1. Purpose
ARC-2. Explanation of Data ARC-3. Assumption(s) ARC-4. Analysis of Results ARC-5. Recommendations
ARC-6. SKM Arc Flash Evaluation Report – Existing
- WWTF Normal Operation (Generator Off)
- WWTF Emergency Operation (Generator On)
ARC-7. SKM Arc Flash Evaluation Report – With All Recommendations ARC-8. Print-out of all Arc-Flash Labels

V. Prioritized Recommendations and Calculations

VI.
Appendices


APP-1.
Input Data (collected from devices and equipment)

APP-2.
DAPPER One-Line Diagram – Existing

APP-3.
DAPPER One-Line Diagram – With All Recommendations

APP-4.
AutoCAD One-Line Diagram

APP-5.
SKM Protective Device Summaries – Existing

APP-6.
SKM Protective Device Summaries – With All Recommendations

3.4 FIELD SETTINGS AND IMPLEMENTATION OF APPROVED REPORT

A. The Contractor shall perform field adjustments of the protective devices as required to place the equipment in final operating condition. The settings shall be in accordance with the approved short circuit study, protective device evaluation study, and protective device coordination study.

B. Necessary field settings of devices and adjustments and minor modifications to equipment to accomplish conformance with the approved short circuit and protective device coordination study shall be carried out by the Contractor at no additional cost to the owner.

C. The Arc-Flash labels shall be applied to each piece of equipment.



END OF SECTION