City And County of San Francisco
Office Of Contract Administration
Purchasing Division
Bid Proposal No. ITSF11000455/CD
Attachment E
Switchgear and Transformers for Calaveras Dam Replacement Project
TECHNICAL SPECIFICATION FOR SHORT-CIRCUIT/ COORDINATION STUDY/
ARC FLASH HAZARD ANALYSIS
PART 1 - GENERAL
1.01
DESCRIPTIONS
A.
The Contractor shall engage the services of an electrical engineer with
qualifications specified in this attachment to conduct the short circuit/
coordination/arc flash hazard analysis study. The Contractor shall coordinate the
scope of work specified under this attachment with other trades and other work.
All equipment, materials, labor, and testing, which are not included in the services
of the electrical engineer conducting the short circuit/ coordination/arc flash
hazard analysis study shall be the responsibility of the Contractor and shall be
included in the Contractor’s base bid.
B.
The objective of the study is to determine the optimal overcurrent protective
device settings to ensure equipment will withstand fault current, to protect
electrical equipment from damage, to size and set overcurrent protection devices
such that in response to an electrical disturbance (short circuit, ground fault,
overvoltage, etc.), the minimum amount of branches of the distribution system is
removed from service, and to determine arc flash hazard, appropriate PPE and
code compliant labeling.
C.
Short circuit ratings of all equipment shall not be less than 115% of calculated
short circuit available.
D.
For purposes of clarity in this attachment, the term overcurrent protective devices
refer to relays, circuit breakers, and fuses. The short circuit/ coordination/arc
flash hazard analysis study is herein referred as the Study in this attachment. The
party conducting the Study, is herein referred to as the Study Engineer. The
Study shall include a system one-line diagram of the power system modeled with
the utility and the existing portable generator power sources. The entire study
package shall include: 1) short circuit calculation; 2) relay, circuit breaker and
fuse coordination; 3) load flow; 4) equipment evaluation; and 5) arc flash
analysis. Potential problem areas shall be identified and specific
recommendations to mitigate these problematic areas shall be included.
E.
The short circuit calculation, load flow, equipment evaluation, and arc flash
analysis studies shall include all portions of the electrical distribution system from
the normal power source and the existing portable generator power source down
to 120/208V and 120/240V panelboard and control panel level. The switching
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Bid Proposal No. ITSF11000455/CD
Attachment E
Switchgear and Transformers for Calaveras Dam Replacement Project
transient analysis, motor starting analysis, and coordination study shall include all
portions of the electrical distribution system from the normal and the existing
portable generator power sources down to the 480V power distribution equipment
level. The coordination study shall include coordination between the upper tiers
of overcurrent protective devices and the smallest adjustable trip circuit breaker in
the power distribution equipment such as switchgear, panelboard, control panel,
etc. Normal system connections and those which result in maximum fault
conditions shall be adequately covered in the five studies referenced in Article
1.01.D above.
F.
The Contractor shall perform field investigation to document as-built electrical
distribution conditions and profile. The Study Engineer shall be responsible for
all necessary research in existing drawings and specifications with respect to
existing and new electrical equipment for a complete power system analysis.
G.
The Contractor shall coordinate a minimum of two meetings between the Study
Engineer and the City Electrical Engineer through the City Representative for
purposes of conducting the preliminary short circuit, load flow, and equipment
evaluation studies. These meetings shall take place within 45 days after NTP or
award of contract.
H.
After all the electrical distribution equipment and inter-equipment conduit and
wiring runs have been installed in place, the Contractor shall refine the
preliminary short circuit, load flow, and equipment evaluation studies referenced
in Article 1.04.B of this attachment based on actual distance measure of conduit
and wiring runs and electrical distribution equipment loading, and shall submit a
final short circuit, load flow, and equipment evaluation studies for City’s review
and approval. Around this time, the two other studies referenced in Article
1.01.D shall also be completed and submitted for City’s review and approval.
After the Study Engineer has incorporated all the City comments on the five
studies referenced in Article 1.01.D, he/she shall submit the final version of the
five studies to the City for approval. The final and City approved version of these
five studies is herein referred to as the Final Study.
I.
After the overcurrent protective device settings have been set in the field per the
Final Study, and the overall electrical distribution system has been tested and
certified by the NETA testing company, the Study Engineer shall submit a copy
of the Final Study to PG&E for review and approval through the City
Representative. This is intended for protective device coordination between
utility and City owned distribution equipment.
J.
SKM Power Tools, latest version, is the only acceptable software for the power
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Bid Proposal No. ITSF11000455/CD
Attachment E
Switchgear and Transformers for Calaveras Dam Replacement Project
system studies.
K.
1.02
RELATED DOCUMENTS
A.
1.03
Overcurrent protective device setting sheets for all protective devices shall be
submitted with recommended settings documented by the Study Engineer based
on the Study. The cover sheet for this set shall be stamped and signed by a
California professional electrical engineer with current registration. Electronic file
of the settings shall also be submitted.
See attachments and appendices.
REFERENCES
A.
Institute of Electrical and Electronics Engineers, Inc. (IEEE):
1.
IEEE 141 – Recommended Practice for Electric Power Distribution and
Coordination of Industrial and Commercial Power Systems
2.
IEEE 242 – Recommended Practice for Protection and Coordination of
Industrial and Commercial Power Systems
IEEE 399 – Recommended Practice for Industrial and Commercial Power
System Analysis
3.
B.
4.
IEEE 241 – Recommended Practice for Electric Power Systems in
Commercial Buildings
5.
IEEE 1015 – Recommended Practice for Applying Low-Voltage Circuit
Breakers Used in Industrial and Commercial Power Systems
6.
IEEE 1584 – Guide for Performing Arc-Flash Hazard Calculations
American National Standards Institute (ANSI):
1.
ANSI C57.12.00 – Standard General Requirements for Liquid-Immersed
Distribution, Power, and Regulating Transformers
2.
ANSI C37.13 – Standard for Low Voltage AC Power Circuit Breakers
Used in Enclosures
3.
ANSI C37.010 – Standard Application Guide for AC High Voltage Circuit
Breakers Rated on a Symmetrical Current Basis
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Switchgear and Transformers for Calaveras Dam Replacement Project
C.
1.04
4.
ANSI C 37.41 – Standard Design Tests for High Voltage Fuses,
Distribution Enclosed Single-Pole Air Switches, Fuse Disconnecting
Switches and Accessories
5.
ANSI C37.5 – Methods for Determining the RMS Value of a Sinusoidal
Current Wave and Normal-Frequency Recovery Voltage, and for
Simplified Calculation of Fault Currents
The National Fire Protection Association (NFPA):
1.
NFPA 70 - National Electrical Code, latest edition
2.
NFPA 70E - Standard for Electrical Safety in the Workplace
SUBMITTALS
A.
Provide Study Engineer’s credentials, resume, sample reports and three
references. The three references shall confirm the equivalent system study
competency of the Study Engineer, and his/her past experience in preparing short
circuit/coordination/arc flash hazard analysis study in projects related to the
water/wastewater industry. Current contact information for the references is
required. For the reasons stated above this submittal is required within 30 days
of NTP or award of contract.
B.
Since the short-circuit study is required to confirm the ratings of the proposed
electrical distribution equipment, preliminary short circuit, load flow, and
equipment evaluation studies are required within 60 days of NTP or award of
contract. The Preliminary Report, which shall include a formal available fault
duty letter from PG & E dated after NTP, shall contain sufficient study data based
on which selection of devices and equipment is possible. The preliminary short
circuit, load flow, and equipment evaluation studies shall be prepared with
completeness and accuracy to allow the reviewer to use this Study to verify
ratings of all electrical equipment submittals.
C.
The preliminary short circuit, load flow, and equipment evaluation studies shall
go through two study report iterations. Each submittal iteration report shall be
subject to review for minimum standards and completeness, and shall include all
the sections described in Article 2.04. Additional iterations may be necessitated
by incomplete single line diagram data or use of unacceptable assumptions.
1.
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Attachment E – 1/17/2011
Study #1 shall include short circuit analysis, load flow, and equipment
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Bid Proposal No. ITSF11000455/CD
Attachment E
Switchgear and Transformers for Calaveras Dam Replacement Project
evaluation.
1.05
Study #2 shall update Study #1 to address all City review comments.
3.
See Article 1.06 for meetings held between the Study Engineer and the City
Electrical Engineer in the course of preparing Study #1 and #2.
D.
Pursuant to Article 1.01.K, the Study shall provide complete overcurrent
protective device setting sheets. Sheets shall include study recommended
overcurrent protective device settings.
E.
Pursuant to Article 1.01.H, the Study Engineer shall submit the Final Study to the
City Representative. The Final Study shall reflect not only all the changes and
revisions made to the studies by the Study Engineer, but also all the settings
implemented in the field on the circuit breakers and fuses by the Contractor, and
all the relay settings and programming performed on the relays by the
representative from the relay company.
F.
Two CD’s containing all the study work including all libraries used.
QUALIFICATIONS
A.
1.06
2.
The Study Engineer performing the coordination study shall be currently involved
in medium-and low-voltage power system analysis. The Study Engineer shall be
an electrical engineer licensed in the State of California with current registration.
He/she shall have a minimum of ten (10) years experience working in power
system analysis, and shall provide a resume, a list of projects performed,
references and three sample project reports. The Study Engineer shall have
experience conducting short circuit/coordination/arc flash hazard analysis study in
the water/wastewater industry. He/she shall be very experienced in SKM
program modeling and shall have experience working with SEL relays. Each of
the sample projects shall be presented in SKM format and shall include settings
for at least three different models of SEL relays. The Final Study referenced in
Article 1.01.H shall be stamped and signed by the Study Engineer.
MEETINGS
A.
City representatives and Study Engineer shall meet two times to plan study details
and evaluate progress for purposes of developing the preliminary short circuit,
load flow, and equipment evaluation studies.
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City And County of San Francisco
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Bid Proposal No. ITSF11000455/CD
Attachment E
Switchgear and Transformers for Calaveras Dam Replacement Project
1.
2.
Initial Meeting
a.
After the Study Engineer has completed Study #1 referenced in
Article 1.04.C.1, a meeting shall be held between the Study
Engineer and the City Electrical Engineer through the arrangement
by the City Representatives to discuss the completed Study #1.
The City Electrical Engineer shall be given four weeks advanced
time frame to review Study #1 before this initial meeting is held.
b.
Discuss City Electrical Engineer’s review comments on Study #1.
Second Meeting
a.
After the Study Engineer has completed Study #2 referenced in
Article 1.04.C.2 and incorporated the City Electrical Engineer’s
review comments on Study #1, a meeting shall be held between the
Study Engineer and the City Electrical Engineer to discuss the
completed Study #2. The City Electrical Engineer shall be given
four weeks advanced time frame to review Study #2 before this
second meeting is held.
b.
The purpose of this meeting between the Study Engineer and the
City Electrical Engineer is to finalize Study #2 so that it can be
released to the Contractor for ordering electrical distribution
equipment based on the short circuit rating recommended in the
Study.
B.
Meetings will be held at 1155 Market Street, San Francisco, CA 94103, unless
otherwise noted by the City Representative. Give three-weeks advanced notice to
the City Representative before each proposed meeting date.
C.
It is the responsibility of the Contractor to pay for all their own travel expenses.
PART 2 - PRODUCTS
2.01
DAPPER STUDIES
A.
The Study Engineer shall model the complete electrical distribution system per
single line diagrams shown in the appendices.
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Bid Proposal No. ITSF11000455/CD
Attachment E
Switchgear and Transformers for Calaveras Dam Replacement Project
2.02
B.
Load flow shall be run and results presented.
C.
Calculate short circuit interrupting and momentary (asymmetrical) duties for 3phase bolted fault, line to line fault, single line to ground fault at each medium
voltage switchgear lineup, branch circuit panelboard, and other significant
locations throughout the system. For ground fault current study include the
associated zero sequence impedance data. Include in tabulations fault impedance,
X to R ratios, asymmetrical values or factors from the manufacturer, motor
contribution, short circuit KVA, and symmetrical and asymmetrical fault currents.
D.
Include complete fault calculations as specified herein for each proposed source
combination.
E.
Use existing and proposed equipment characteristics to verify equipment ratings
required. The Contractor shall quickly gather this information for timely approval
of electrical equipment. Make all additions or changes as required by the City’s
reviewer and prepare Study #1 and #2.
F.
Include fault contribution of all motors 1 hp and larger. Smaller size motors may
be grouped.
G.
Notify the City Representative in writing of circuit protective devices and
electrical equipment not properly rated for fault conditions.
H.
Perform Equipment Evaluation studies for equipment evaluation based on
marginal/fail criteria required by the SKM Power Tools software as agreed with
the City Representative.
I.
Use actual conductor impedances and lengths. If impedances are unknown, use
typical conductor impedances from SKM for preliminary studies.
J.
Transformer design impedances and standard X/R ratios shall be used when
nameplate values are not available. Final report shall show actual impedances.
CAPTOR STUDIES
A.
In order to select proper relay, circuit breaker and fuse characteristics as required
for optimal coordination, the coordination study shall be performed for the
electrical distribution equipment described in the project. All overcurrent
protective device settings shall be based on the recommendations of the approved
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City And County of San Francisco
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Bid Proposal No. ITSF11000455/CD
Attachment E
Switchgear and Transformers for Calaveras Dam Replacement Project
Study #2. See Article 1.04.C for details.
B.
Coordination study shall include coordination between negative sequence
overcurrent elements with phase overcurrent elements. Negative sequence relay
settings shall be determined based on unbalanced fault study.
C.
Include on the curve sheets utility company short circuit contribution, mediumvoltage equipment relay characteristics, low-voltage equipment circuit breaker
trip device and fuse characteristics, pertinent transformer characteristics, pertinent
motor and existing portable generator characteristics, and characteristics of other
system components. Include all overcurrent protective devices down to those in
the 480V distribution level.
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.
F.
The coordination study shall address relay setting requirements with respect to
utility company’s protection for the respective incoming service.
G.
Provide adequate time margins between device characteristics such that selective
operation is provided, while providing proper protection.
1.
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.
2.
Separate medium-voltage relay characteristic curves from curves for other
devices by at least a 0.4-second time margin.
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City And County of San Francisco
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Bid Proposal No. ITSF11000455/CD
Attachment E
Switchgear and Transformers for Calaveras Dam Replacement Project
2.03
2.04
ARC FLASH HAZARD ANALYSIS
A.
The arc flash hazard analysis shall be performed according to the IEEE 1584
equations that are presented in NFPA70E-2009, Annex D.
B.
The flash protection boundary and the incident energy shall be calculated at all
significant locations in the electrical distribution system (switchgears,
panelboards) where work could be performed on energized parts.
C.
The Arc Flash Hazard Analysis shall include all medium voltage, 480V locations
and locations in 240 volt and 208 volt systems fed from transformers equal to or
greater than 125 kVA.
D.
Safe working distances shall be specified for calculated fault locations based on
the calculated arc flash boundary with an incident energy of 1.2 cal/cm2.
E.
The Arc Flash Hazard analysis shall include calculations for maximum and
minimum contributions of fault current magnitude. The minimum calculation
shall assume that the utility contribution is at a minimum and shall assume a
minimum motor load. Conversely, the maximum calculation shall assume a
maximum contribution from the utility and shall assume motors to be operating
under full-load conditions.
F.
Arc flash computation shall include both line and load side of main circuit breaker
calculations, where necessary.
G.
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.
PRELIMINARY STUDY REPORT
A.
Provide the following:
1.
2.
3.
4.
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Calculation methods and assumptions.
Selected base per unit quantities.
Input data report.
One-line diagram of the system being evaluated with available fault at
each bus, and interrupting rating of devices noted.
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Switchgear and Transformers for Calaveras Dam Replacement Project
5.
6.
7.
8.
B.
Calculate short-circuit momentary and interrupting duties for a three-phase bolted
fault at each:
1.
2.
3.
4.
5.
Electric utility’s supply termination point.
Medium voltage switchgear.
Existing portable generator.
Branch circuit panelboards.
At all locations where electrical equipment will be provided in the system,
including all new control panel locations.
C.
For grounded systems, provide a bolted line-to-ground fault current study for
areas as defined for the three-phase bolted fault short-circuit study.
D.
Protective Device Evaluation:
1.
2.
3.
4.
5.
2.05
Source impedance data, including electric utility system and motor fault
contribution characteristics.
Typical calculations.
Tabulations of calculated quantities.
Results, conclusions, and recommendations.
Evaluate equipment and protective devices and compare to short circuit
ratings.
Adequacy of switchgear and panelboard bus bracing to withstand shortcircuit stresses.
Adequacy of transformer windings to withstand short-circuit stresses.
Cable sizes for ability to withstand short-circuit heating.
CT sizing is appropriate for fault current and trip functions.
COMPLETE STUDY REPORT
A.
The results of the power system study shall be summarized in a complete report.
Three (3) bound copies each of Study #1 and Study #2 are required. Six (6)
bound copies of the Final Study shall be submitted.
B.
SKM crystal reports shall be used.
C.
The Studies shall include all information specified in NETA Acceptance Testing
Specifications for Electrical Power Distribution Equipment and Systems.
D.
The report shall include the following sections:
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Attachment E
Switchgear and Transformers for Calaveras Dam Replacement Project
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
E.
Descriptions, purpose, basis and scope of the study.
Executive Summary.
Recommendations for system improvements, where needed.
Load flow showing voltage drop at each bus, among other data.
Equipment evaluation.
Short circuit study.
Coordination Study.
Arc Flash Evaluation.
Input data
Two full size system complete single line diagrams in ANSI Size E
drawings. Single line diagram shall show protective device ampere
ratings and associated designations, cable size and length, transformer
kVA and voltage ratings, motor and existing portable generator kVA and
voltage ratings, and switchgear, and panel board voltage ratings and
designations.
Completed relay setting sheets.
In the protective device coordination study section, 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. Utilize 11” X 17” sized paper to
present the information on one sheet for each coordination thread.
1.
Terminate device characteristic curves at a point reflecting maximum
symmetrical or asymmetrical fault current to which device is exposed.
2.
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.
3.
Plot the following characteristics on the curve sheets, where applicable:
a.
b.
c.
d.
e.
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Attachment E – 1/17/2011
Electric utility’s protective device.
Medium voltage equipment relays.
Medium and low voltage fuses including manufacturer’s minimum
melt, total clearing, tolerance, and damage bands.
Low voltage equipment circuit breaker trip devices, including
manufacturer’s tolerance bands.
Transformer full-load current, magnetizing inrush current, and
ANSI transformer withstand parameters.
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Bid Proposal No. ITSF11000455/CD
Attachment E
Switchgear and Transformers for Calaveras Dam Replacement Project
f.
g.
h.
i.
j.
Conductor damage curves.
Ground fault protective devices.
Pertinent motor starting characteristics and motor damage points.
Pertinent existing portable generator short-circuit decrement curve
and existing portable generator damage point.
Other system load protective devices for the largest branch circuit
and the largest feeder circuit breaker in each electrical distribution
equipment such as panelboard.
F.
Arc Flash Section shall describe the calculation method used, flash protection
boundary, hazard risk category and incident energy. Also, replicas of Arc Flash
Labels for all electrical distribution gear in this project shall be included.
G.
Input Data:
1.
2.
3.
4.
5.
Utility three-phase and line-to-ground available contribution with
associated X/R ratios.
Short-circuit reactance of rotating machines with associated X/R ratios.
Cable type, construction, size, number per phase, length, impedance and
conduit type.
Transformer primary and secondary voltages, winding configurations,
kVA rating, impedance, and X/R ratio.
Reactor inductance and continuous ampere rating.
PART 3 - EXECUTION
3.01
DATA COLLECTION
A.
Contractor shall solely be responsible for providing all the information needed to
perform the power system analysis as described in this attachment to the Study
Engineer. Contractor shall coordinate with Study Engineer to provide all the
information needed by him/her.
B.
Contractor shall provide a complete set of data collection documents in the field.
C.
Contractor shall provide all data from the equipment manufacturer and
confirm/correct all pertinent data, including cable type, length and configuration.
The Contractor shall expedite collection of the data to eliminate unnecessary
delays and assure completion of the studies as required for final approval of the
distribution equipment shop drawings before release of the equipment from the
factory.
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D.
3.02
For existing equipment data the Contractor shall coordinate site visit(s) and
investigate and obtain all pertinent field data to prepare the Study. Contractor
shall engage the services of electricians, as needed, to investigate existing field
conditions.
ARC FLASH WARNING LABELS
A.
Provide a 3.5 inch x 5 inch thermal transfer type label of high adhesion polyester
for each work location analyzed.
B.
The label shall have an orange header with the wording, “WARNING, ARC
FLASH HAZARD”, or any other “DANGEROUS” sign required and shall
include the following information:
1.
2.
3.
4.
5.
6.
7.
8.
9.
Location designation.
Nominal voltage.
Flash protection boundary.
Hazard risk category.
Incident energy.
Working distance.
Engineering report number, revision number and issue date.
Labels shall be machine printed, with no field markings.
Arc flash labels shall be provided in the following manner and all labels
shall be based on recommended over current device settings.
C.
Labels shall be field installed by the Contractor under the supervision of the Study
Engineer.
D.
For the work locations not analyzed within the arc flash study such as landscape
irrigation controller panels, auxiliary relay panels and any other panels that are
powered by 120 volts, provide labels as shown below. Labels shall be a 3.5 inch
x 2 inch thermal transfer type label of high adhesion polyester. Provide a
minimum of 100 spare arc flash labels as shown below.
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3.03
DEVICE SETTING
A.
The Contractor shall be responsible for setting all overcurrent protective devices
except relays per the recommended settings from the Study, and the representative
from the relay manufacturer shall be responsible for programming/settings of all
relays. The Study Engineer is required to supervise the on site settings of all
overcurrent protective devices including the programming/ settings of all relays.
The Study Engineer shall certify that all overcurrent protective devices are set per
the Study. After the certification by the Study Engineer, the NETA testing
company in the Electrical Equipment Commissioning and Technical Support
attachment shall perform overall electrical distribution system testing and certify
the passing of the NETA test before the plant is ready for energization.
B.
Pickup and time delays for overcurrent protective devices shall not be tested at
minimum values. Test overcurrent protective devices at the final settings per the
coordination study.
END OF ATTACHMENT
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