Power System Study

General
Division 260573
Power System Study
DESIGN GUIDE
1 General
1.1 Introduction
A. This section applies to the following:
1. Short circuit analysis
2. Selective coordination analysis
3. Overcurrent protective device settings
4. Arc Flash Hazard Analysis
1.2 References
A. IEEE 141 – Recommended Practice for Electric Power Distribution and
Coordination of Industrial and Commercial Power Systems
B. IEEE 242 – Recommended Practice for Protection and Coordination of

Industrial and Commercial Power Systems
C. IEEE 399 - Recommended Practice for Industrial and Commercial

Power Systems Analysis
D. IEEE 1584 – Guide for Performing Arc-Flash Hazard Calculations
1.3 Scope
A. The Contractor shall employ the services of a skilled specialist to
perform the following studies:
Division 260573 – Power System Study Design Guide 1

September 30, 2022
Materials
1. Short Circuit Analysis including:
a. Primary side of pad mounted service transformers assuming an

infinite bus.
b. Service entrance, main and distribution switchboards, dry-type

transformers, distribution and branch circuit panels, and
associated feeders.
c. Generator system if present.
d. Building motor contributions.
2. Relay, Fuse and Circuit Breaker Coordination Study including:
a. NEC 700, 701 and 702 distribution systems.
3. Load Flow Analysis including:
a. All electrical distribution systems.
4. Arc Flash Hazard Analysis and Labeling including:
a. Primary side of pad mounted transformers.
b. All electrical distribution system busses including normal and

alternate power systems sources.
2 Materials
2.1 Computer Software
A. Software shall plot and diagram time-current characteristic curves as
part of its output.
B. Software shall report device settings and ratings of all overcurrent

protective devices.

September 30, 2022
Execution
2.2 Study Report

A. The results of the power system studies shall be summarized in a
compiled study report. Copies of the final report shall be furnished and
included in the O&M Manuals.
B. The report shall include the following sections:
1. Project description, purpose, basis and scope of the study.
2. Fault current calculations and indication that with the

recommendations included in the study, the equipment will be
properly rated and provided such that it will continue to operate
properly following a maximum fault current episode.
3. Tabulations of circuit breaker, fuse and other protective device

ratings versus calculated short circuit duties, and commentary
regarding the same.
4. Copies of manufacturer’s time-current curves for the devices

studied.
5. Protective device time versus current coordination curves. Overlay

curves to prove coordination.
6. Tabulations of relay and circuit breaker trip settings, fuse

selections, and commentary regarding the same.
7. Coordination tabulation and report indicating that with the

recommendations included in the study, the system will be
coordinated.
8. Calculations and placards required for posting relative to the Arc-

Flash study. Provide all such placards and install at each item of
equipment for the worst-case Operating Scenario.
3 Execution
3.1 Data Collection
A. The Contractor shall be responsible to obtain all required data
necessary for the required studies.

September 30, 2022
Execution
3.2 Short Circuit Analysis

A. Perform computer aided short circuit analysis using suitable software.
B. Source Impedance:
1. Assume an infinite bus on the primary side of each pad mounted

distribution transformer.
C. Determine the available 3-phase short circuit and ground fault currents
at each bus. Incorporate the motor contribution, applying motor
contribution at the appropriate locations in the system.
D. Provide a summary section evaluating the adequacy of the distribution

equipment. Make recommendations as appropriate for improvements
to the system.
E. Contractor shall provide a preliminary study prior to submission of

switchboard, panelboard, and circuit breaker product submittals.
3.3 Selective Coordination Analysis

A. Perform computer aided selective coordination analysis using suitable
software.
B. A sufficient number of computer generated log-log plots shall be

provided to indicate the degree of system protection and coordination.
Display the time-current characteristics of series connected
overcurrent devices and other pertinent system parameters.
C. A table shall be included to summarize the settings selected for the

protective devices.
D. Provide a summary section evaluating the degree of system protection

and service continuity with overcurrent devices, along with
recommendations for increasing system protection or device
coordination. Highlight areas lacking coordination.
E. Contractor shall provide a preliminary study prior to submission of

switchboard, panelboard, and circuit breaker product submittals.

September 30, 2022
Execution
3.4 Over-Current Protection Device Setting

A. Model the entire electrical distribution system and run load flow
analysis for all operating scenarios.
B. Engage a factory-authorized service representative, to set overcurrent

protective devices within equipment in accordance with the results of
the study. Provide a written report which itemizes each setting applied
to each device.
3.5 Arc-Flash Hazard Analysis

A. Provide Arc-Flash labeling for all electrical equipment on the project in
accordance with the requirements of NEC Article 110.
B. Calculate the flash protection boundary and incident energy at all

significant locations including switchgear, buses, switchboards, motor
control centers, distribution panels, panelboards, and other locations
that could require maintenance or service. Repeat calculations for
each Operating Scenario.
C. The analysis shall include all medium voltage equipment and locations
plus all 480 & 208 volt locations within the limit of the study.
D. Safe working distances shall be specified for all calculated fault

locations based on the calculated arc flash boundary incident energy in
accordance with IEEE 1584 (>1.2 cal/cm2)
E. The analysis shall include calculations for maximum and minimum

contributions of fault current magnitude originating from both line and
load side.
F. Calculations shall be based on actual overcurrent clearing protective

device clearing time with a maximum clearing time as recommended in
IEEE 1584 (<2 seconds).
G. Include a list of all required placards with all the necessary information
for each within the report.
H. Placards shall be 3.5” x 5” and shall be provided for each work location
analyzed. Each placard shall include an orange header with the
wording “WARNING, ARC FLASH HAZARD” with all recommended
information and in the configuration suggested in IEEE 1584.

September 30, 2022
Appendix
4 Appendix
4.1 Reserved for future.

September 30, 2022

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General

1. Short circuit analysis

2. Selective coordination analysis

3. Overcurrent protective device settings

4. Arc Flash Hazard Analysis

B. IEEE 242 – Recommended Practice for Protection and Coordination of

C. IEEE 399 - Recommended Practice for Industrial and Commercial

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

Division 260573 – Power System Study Design Guide 1

1. Short Circuit Analysis including:

a. Primary side of pad mounted service transformers assuming an

b. Service entrance, main and distribution switchboards, dry-type

c. Generator system if present.

d. Building motor contributions.

2. Relay, Fuse and Circuit Breaker Coordination Study including:

a. NEC 700, 701 and 702 distribution systems.

3. Load Flow Analysis including:

a. All electrical distribution systems.

4. Arc Flash Hazard Analysis and Labeling including:

a. Primary side of pad mounted transformers.

b. All electrical distribution system busses including normal and

B. Software shall report device settings and ratings of all overcurrent

Division 260573 – Power System Study Design Guide 2

2.2 Study Report

B. The report shall include the following sections:

1. Project description, purpose, basis and scope of the study.

2. Fault current calculations and indication that with the

3. Tabulations of circuit breaker, fuse and other protective device

4. Copies of manufacturer’s time-current curves for the devices

5. Protective device time versus current coordination curves. Overlay

6. Tabulations of relay and circuit breaker trip settings, fuse

7. Coordination tabulation and report indicating that with the

8. Calculations and placards required for posting relative to the Arc-

Division 260573 – Power System Study Design Guide 3

3.2 Short Circuit Analysis

1. Assume an infinite bus on the primary side of each pad mounted

D. Provide a summary section evaluating the adequacy of the distribution

E. Contractor shall provide a preliminary study prior to submission of

3.3 Selective Coordination Analysis

B. A sufficient number of computer generated log-log plots shall be

C. A table shall be included to summarize the settings selected for the

D. Provide a summary section evaluating the degree of system protection

E. Contractor shall provide a preliminary study prior to submission of

Division 260573 – Power System Study Design Guide 4

3.4 Over-Current Protection Device Setting

B. Engage a factory-authorized service representative, to set overcurrent

3.5 Arc-Flash Hazard Analysis

B. Calculate the flash protection boundary and incident energy at all

D. Safe working distances shall be specified for all calculated fault

E. The analysis shall include calculations for maximum and minimum

F. Calculations shall be based on actual overcurrent clearing protective

Division 260573 – Power System Study Design Guide 5

Division 260573 – Power System Study Design Guide 6

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