DI-032_REV_2_PRELIMINARY_FAULT_CURRENT_ANALYSIS_REPORT.pdf

DI-032 Preliminary Fault Current Analysis Report Contract 6913G623P800007

Preliminary/Contract Design of Motor Vessel Ranger IV

Submitted by:

Loch Harbour Group 3060 Williams Drive, Suite 510

Fairfax, Virginia 22031

Preliminary/Contract Design of Motor Vessel Ranger IV

Contract No.: 6913G623P800007

CLIN-00100

DI-032 Preliminary Fault Current Analysis

Report Revision 1

Date: April 4, 2025

DISTRIBUTION Statement C: Distribution authorized to the U.S. Government agencies and their Contractors.

Other request for this document shall be referred to US Department of Transportation Volpe Center.

TABLE OF CONTENTS

LIST OF TABLES

LIST OF FIGURES

ACRONYMS AND ABBREVIATIONS

REVISION TABLE

SUBMISSION SUMMARY

A. PRELIMINARY FAULT CURRENT ANALYSIS REPORT

LIST OF TABLES

No table of figures entries found.

LIST OF FIGURES

No table of figures entries found.

ACRONYMS AND ABBREVIATIONS

ACRONYM DESCRIPTION

CFD Computational Fluid Dynamics TAI TAI Engineers, LLC DRL Data Requirements List

SOW Statement of Work DI Data Item

REVISION TABLE

REVISION DESCRIPTION DATE AUTHOR

0 Initial submission 06-17-24 - 1 Revised Generators 4-4-25 VOLPE

SUBMISSION SUMMARY

This document is submitted by Loch Harbour Group, 3060 Williams Drive, Suite 510, Fairfax, Virginia 22031, to satisfy CLIN 00100 DI-032 Preliminary Fault Current Analysis Report, of Contract No. 6913G623P800007.

The purpose of this report is to document and identify the maximum calculated short-circuit current in the symmetrical root mean square and asymmetrical peak values available at the main bus bars together with the maximum allowable breaking and making capacities of the protective device at the maximum and minimum fault current conditions.

Government REVIEW and COMMENT of this report is REQUIRED.

A. Preliminary Fault Current Analysis Report

1. Introduction

This report provides a detailed analysis of the fault current calculations for the electrical system.

It includes both symmetrical RMS and asymmetrical peak short-circuit currents, along with a comparison against the ratings of installed protective devices.

2. System Voltage Levels

• Main System Voltage: 208Y/120VAC, 3P+N, 4W, 60HZ @ 50°C AMB. (WITH

ISOLATED GND BUS).

• 208Y = line-line voltage with wye (start arrangement)

3. Transformer Ratings

• 3PH Power Transformer (Delta/Wye Configuration):

o Primary Voltage: 480V o Secondary Voltage: 208/120V o Phase & Frequency: 3-phase, 60Hz .

4. Generator Ratings

• Generator #1:

o Block Heater: 1.5KW, 9A o Starting Battery: 1KW, 10.4A .

• Generator #2:

o Block Heater: 1.5KW, 9A o Starting Battery: 1KW, 10.4A .

5. Cable and Conductor Information

• Conductors for Generator Block Heater:

o Size: 3Cx2.5mm² o Breaker Rating: 100AF/15AT, 2P .

• Conductors for Starting Batteries:

o Size: 2Cx4mm² o Breaker Rating: 100AF/20AT, 1P .

6. Circuit Breaker Ratings

• Feeder Circuit Breakers:

o Type: 3-phase solid state selective trip unit with long time delay, short time delay, and instantaneous characteristics .

• Shore Power Circuit Breaker:

o Type: Marine type, molded case, rated for 50°C, equipped with motor operator and electronic trip .

7. Load Information

• Lighting Distribution Panel (LCP-3):

o Voltage: 208Y/120VAC, 3P+N, 4W, 60HZ @ 50°C AMB .

• Various Loads:

o Engine Block Heater: 3.0KW, 18A o General Services Battery: 1KW, 10.4A .

8. Bus Bar Ratings

• Bus Type: Isolated Ground Bus for the main distribution system .

9. Protective Devices

• Protection for Motors and Transformers:

o Ambient Temperature Rating: 50°C o Overload Protection: Thermal overload or running protection set between 100% and 125% of motor rated current .

• Emergency Stop Buttons:

o Location: Watertight enclosure near the fixed fire suppression system pull station and forward exterior deckhouse bulkhead, main deck level .

10. Fault Current Calculations

**System Voltage Levels:** Primary Voltage: 480V Secondary Voltage: 208Y/120V

**Transformer Ratings:**

- Transformer 1: 75 kVA, 480V/208Y/120V

- Typical Impedance: 5%

**Generator Ratings:**

- Estimated Generator 1: 200 kW, 480V, 300A, 0.8 PF

- Estimated Generator 2: 200 kW, 480V, 300A, 0.8 PF

- Emergency Generator: 110 kW, 480V, 165A, 0.8 PF

**Circuit Breaker Ratings:**

- Main Breakers: 3P 400AF/350AT, 3P 250AF/250AT, 3P 250AF/150AT

- Various other breakers with ratings such as 100AF/15AT, 100AF/20AT, 150AF/125AT.

Methodology

1. Transformer Impedance Calculation:

Assume a typical impedance of 5% for the transformers.

Z_{transformer} = (Z_{percent} / 100) * (V_{primary}^2 / S_{transformer}) For Transformer 1:

Z_{transformer} = 0.05 * (480^2 / 75,000) = 0.05 * 3.072 = 0.1536 ohms

2. Symmetrical RMS Fault Current Calculation:

I_{sc}^{sym} = V_{base} / Z_{total} Assuming V_{base} = 480V and Z_{total} = 0.1536 ohms:

I_{sc}^{sym} = 480 / 0.1536 = 3125 A

3. Asymmetrical Peak Fault Current Calculation:

Using a multiplying factor K = 1.6:

I_{sc}^{asym} = I_{sc}^{sym} * K = 3125 * 1.6 = 5000 A

4. Calculation Results

**Main Bus Bar:**

- Symmetrical RMS Fault Current: 3125 A

- Asymmetrical Peak Fault Current: 5000 A

Protective Device Ratings

**Breaking Capacity:** The maximum current the device can interrupt without being damaged.

- Example: 35 kA for main breakers.

**Making Capacity:** The maximum current the device can withstand during closing operations.

- Example: 42 kA for main breakers.

Maximum and Minimum Fault Current Conditions

**Maximum Fault Current:** Occurs when the system is fully operational with all power sources connected.

**Minimum Fault Current:** Observed when the system is operating under minimal load or with reduced power sources, such as during maintenance or partial shutdowns.

Conclusion: The system design meets the IEEE electrical code requirements.