12 Attachment 04 UFC_3_555_01n_2004.pdf

UFC 3-555-01N

16 January 2004

UNIFIED FACILITIES CRITERIA (UFC)

400 HERTZ MEDIUM

VOLTAGE

CONVERSION/DISTRIBUTION AND

LOW VOLTAGE UTILIZATION

SYSTEMS

APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED

UNIFIED FACILITIES CRITERIA (UFC)

400 HERTZ MEDIUM VOLTAGE CONVERSION/DISTRIBUTION AND LOW

VOLTAGE UTILIZATION SYSTEMS

Any copyrighted material included in this UFC is identified at its point of use.

Use of the copyrighted material apart from this UFC must have the permission of the copyright holder.

U.S. ARMY CORPS OF ENGINEERS (Preparing Activity)

NAVAL FACILITIES ENGINEERING COMMAND

AIR FORCE CIVIL ENGINEERING SUPPORT AGENCY

Record of Changes (changes indicated by \1\ ... /1/ )

Change No. Date Location

FOREWORD

The Unified Facilities Criteria (UFC) system is prescribed by MIL-STD 3007 and provides planning, design, construction, sustainment, restoration, and modernization criteria, and applies to the Military Departments, the Defense Agencies, and the DoD Field Activities in accordance with USD(AT&L) Memorandum dated 29 May 2002. UFC will be used for all DoD projects and work for other customers where appropriate. All construction outside of the United States is also governed by Status of forces Agreements (SOFA), Host Nation Funded Construction Agreements (HNFA), and in some instances, Bilateral Infrastructure Agreements (BIA.)

Therefore, the acquisition team must ensure compliance with the more stringent of the UFC, the SOFA, the HNFA, and the BIA, as applicable.

UFC are living documents and will be periodically reviewed, updated, and made available to users as part of the Services’ responsibility for providing technical criteria for military construction. Headquarters, U.S. Army Corps of Engineers (HQUSACE), Naval Facilities Engineering Command (NAVFAC), and Air Force Civil Engineer Support Agency (AFCESA) are responsible for administration of the UFC system. Defense agencies should contact the preparing service for document interpretation and improvements. Technical content of UFC is the responsibility of the cognizant DoD working group. Recommended changes with supporting rationale should be sent to the respective service proponent office by the following electronic form: Criteria Change Request (CCR). The form is also accessible from the Internet sites listed below.

UFC are effective upon issuance and are distributed only in electronic media from the following source:

• Whole Building Design Guide web site http://dod.wbdg.org/.

Hard copies of UFC printed from electronic media should be checked against the current electronic version prior to use to ensure that they are current.

AUTHORIZED BY:

DONALD L. BASHAM, P.E.

Chief, Engineering and Construction U.S. Army Corps of Engineers

DR. JAMES W WRIGHT, P.E.

Chief Engineer Naval Facilities Engineering Command

KATHLEEN I. FERGUSON, P.E.

The Deputy Civil Engineer DCS/Installations & Logistics Department of the Air Force

Dr. GET W. MOY, P.E.

Director, Installations Requirements and Management Office of the Deputy Under Secretary of Defense (Installations and Environment) http://www.wbdg.org/pdfs/ufc_implementation.pdf http://www.wbdg.org/ccb/browse_cat.php?o=29&c=4 http://dod.wbdg.org/ i

CONTENTS

Page

CHAPTER 1 INTRODUCTION

Paragraph 1-1 PURPOSE AND SCOPE ....................................................... 1-1

1-2 APPLICABILITY..................................................................... 1-1 1-3 REFERENCES ...................................................................... 1-1

APPENDIX A MIL-HDBK 1004/5, JUNE 1993.…...………..…………………… A-1

1-1

CHAPTER 1

INTRODUCTION

1-1 PURPOSE AND SCOPE. This UFC is comprised of two sections.

Chapter 1 introduces this UFC and provides a listing of references to other Tri-Service documents closely related to the subject. Appendix A contains the full text copy of the previously released Military Handbook (MIL-HDBK) on this subject. This UFC serves as criteria until such time as the full text UFC is developed from the MIL-HDBK and other sources.

This UFC provides general criteria for 400-hertz medium voltage conversion/distribution and low voltage utilization systems.

Note that this document does not constitute a detailed technical design, maintenance or operations manual, and is issued as a general guide to the considerations associated with design of economical, efficient and environmentally acceptable heating plants.

1-2 APPLICABILITY. This UFC applies to all Navy agencies and contractors preparing designs for 400 hertz medium voltage conversion/distribution and low voltage utilization systems.

1-2.1 GENERAL BUILDING REQUIREMENTS. All DoD facilities must comply with UFC 1-200-01, Design: General Building Requirements. If any conflict occurs between this UFC and UFC 1-200-01, the requirements of UFC 1-200-01 take precedence.

1-2.2 SAFETY. All DoD facilities must comply with DODINST 6055.1 and applicable Occupational Safety and Health Administration (OSHA) safety and health standards.

NOTE: All NAVY projects, must comply with OPNAVINST 5100.23 (series), Navy Occupational Safety and Health Program Manual. The most recent publication in this series can be accessed at the NAVFAC Safety web site:

www.navfac.navy.mil/safety/pub.htm. If any conflict occurs between this UFC and OPNAVINST 5100.23, the requirements of OPNAVINST 5100.23 take precedence.

1-2.3 FIRE PROTECTION. All DoD facilities must comply with UFC 3-600-01, Design: Fire Protection Engineering for Facilities. If any conflict occurs between this UFC and UFC 3-600-01, the requirements of UFC 3-600-01 take precedence.

1-2.4 ANTITERRORISM/FORCE PROTECTION. All DoD facilities must comply with UFC 4-010-01, Design: DoD Minimum Antiterrorism Standards for Buildings. If any conflict occurs between this UFC and UFC 4-010-01, the requirements of UFC 4-010-01 take precedence.

http://www.navfac.navy.mil/safety/pub.htm

A-1

APPENDIX A

MIL-HDBK 1004/5

400 HERTZ MEDIUM VOLTAGE CONVERSION/DISTRIBUTION AND LOW

VOLTAGE UTILIZATION SYSTEMS

i

INCH-POUND

MIL-HDBK-1004/5

15 June 1993

SUPERSEDING

DM-04.05

30 March 1987

MILITARY HANDBOOK

400-HERTZ MEDIUM-VOLTAGE CONVERSION/DISTRIBUTION AND

LOW-VOLTAGE UTILIZATION SYSTEMS

AMSC N/A

AREA FACR

DISTRIBUTION STATEMENT A. APPROVED FOR PUBLIC RELEASE: DISTRIBUTION IS

UNLIMITED

MIL-HDBK-1004/5

ii

ABSTRACT

Basic design guidance is presented for use by experienced architects and engineers. The contents cover 400-Hertz (Hz) electrical design considerations, such as the estimates of loads and requirements for the installation and selection of frequency conversion and electric distribution systems with a special regard to the use of centralized conversion equipment utilizing medium-voltage distribution.

iii

FOREWORD

This handbook is one of a series developed from an evaluation of facilities in the shore establishment, from surveys of the availability of new materials and construction methods, and from selection of the best design practices of the Naval Facilities Engineering Command (NAVFACENGCOM), other Government agencies, and the private sector. This handbook uses, to the maximum extent feasible, national professional society, association, and institute standards in accordance with NAVFACENGCOM policy. Deviations from these criteria should not be made without prior approval of NAVFACENGCOM Headquarters (Code 04).

Design cannot remain static any more than the naval functions it serves or the technologies it uses. Accordingly, recommendations for improvement are encouraged from within the Navy and from the private sector and should be furnished to Commanding Officer, Southern Division, Naval Facilities Engineering Command (SOUTHNAVFACENGCOM), Code 04A3, P.O. Box 10068, Charleston, SC 29411-0068; telephone (803) 743-0458.

THIS HANDBOOK SHALL NOT BE USED AS A REFERENCE DOCUMENT FOR PROCUREMENT OF

FACILITIES CONSTRUCTION. IT IS TO BE USED IN THE PURCHASE OF FACILITIES

ENGINEERING STUDIES AND DESIGN (FINAL PLANS, SPECIFICATIONS, AND COST

ESTIMATES). DO NOT REFERENCE IT IN MILITARY OR FEDERAL SPECIFICATIONS OR

OTHER PROCUREMENT DOCUMENTS.

iv

ELECTRICAL ENGINEERING CRITERIA MANUALS

Criteria Manual Title PA

MIL-HDBK-1004/1 Electrical Engineering Preliminary HQTRS Design Considerations

MIL-HDBK-1004/2 Power Distribution Systems PACDIV

MIL-HDBK-1004/3 Switchgear and Relaying HQTRS

MIL-HDBK-1004/4 Electrical Utilization Systems HQTRS

MIL-HDBK-1004/5 400-Hertz Medium Voltage Conversion/ Distribution and Low-Voltage Utilization SOUTHDIV Systems

MIL-HDBK-1004/6 Lightning Protection HQTRS

MIL-HDBK-1004/7 Wire Communication and Signal Systems HQTRS

DM-4.09 Energy Monitoring and Control HQTRS Systems (ARMY)

MIL-HDBK-1004/10 Electrical Engineering Cathodic Protection NCEL v

400-HERTZ MEDIUM-VOLTAGE

CONVERSION/DISTRIBUTION AND LOW-VOLTAGE UTILIZATION SYSTEMS

CONTENTS

Page

Section 1 INTRODUCTION

1.1 Scope

1.2 Cancellation

1.3 Policy

Section 2 GENERAL CONSIDERATIONS

2.1 Usage

2.2 Types of Systems

2.2.1 Rotary Converters

2.2.2 Solid State Converters

2.3 Distribution Systems

2.3.1 Low-Voltage Systems

2.3.2 Medium-Voltage System

2.3.3 Flight-line Electrical Distribution Set (FLEDS) . . . 3

2.4 Surveys

2.4.1 Energy Conservation

2.4.2 Economic Studies

2.5 Types of Loads

2.5.1 Aircraft

2.5.2 Avionics

2.5.3. Other Facilities

2.5.4 Special Requirements

2.6 Consideration of Systems Voltage Parameters

2.6.1 Development of Guidelines for Parameters

2.6.2 Items Affecting Design

2.6.2.1 Acceptable End-Voltage Requirements

2.6.2.2 Equipment and Cable Parameters

2.6.2.3 Unit Loads

2.6.3 Maximum Cable Length and Loads

2.6.3.1 Allowable Medium-Voltage Distribution Level

2.6.3.2 Maximum Cable Lengths

2.6.3.3 Exceeding Limiting Cable Lengths

2.6.3.4 Rationale of Maximum Cable Lengths

Section 3 DESIGN REQUIREMENTS

3.1 Design Procedures

3.1.1 Data Gathering

3.1.2 System Layout

3.1.3 Equipment Layout

3.1.4 Design Aspects

3.1.4.1 Protective Device Operation

3.1.4.2 Surge Arresters

vi

Page

3.1.4.3 Bus and Cable Material

3.1.4.4 Conduit

3.2 Medium-Voltage Distribution System Design

3.2.1 Type of Distribution

3.2.2 Practicable Distribution Area

3.2.3 Shunt Reactor Capacity

3.2.3.1 Field Adjustment

3.2.3.2 Nominal Rating Sizing

3.3 Central Plant Design

3.3.1 Reliability

3.3.2 System 60-Hertz Input Power

3.3.2.1 Primary Feeder Source

3.3.2.2 Diesel-Engine Generator Source

3.3.2.3 Transformer

3.3.3 System 400-Hertz Conversion Capacity

3.3.4 Frequency Conversion Assemblies

3.3.4.1 Motor Generator Units

3.3.4.2 Other Components

3.3.5 Feeder Distribution Center

3.3.5.1 Metering

3.3.5.2 Shunt Reactors

3.3.6 Central Plant Buildings and Other Equipment Shelters . 26

3.4 Low-Voltage Utilization System Design

3.4.1 Low-Voltage System Equipment

3.4.1.1 Utilization Service Assemblies

3.4.1.2 Fixed Service Point Units

3.4.2 Low-Voltage Cable Limitations

3.4.3 Feeder Cable Connection

3.4.4 Cable Design Requirements

Section 4 DESIGN ANALYSIS

4.1 General Requirements

4.2 Scope

4.3 Basis for Design

4.3.1 Type of System

4.3.2 400-Hertz Conversion

4.3.3 60-Hertz Input Power

4.3.3.1 Adequacy

4.3.3.2 Transformer Stations

4.3.3.3 Generator Source

4.3.4 Distribution

4.4 Design Computations

4.4.1 Capacity and Other Calculations

4.4.2 Short Circuits

4.4.2.1 400-Hertz Systems

4.4.2.2 Analysis

vii

Page

APPENDIX A: Analysis of 400-Hertz Centralized Power Distribution Systems

APPENDIX B: Analysis of 400-Hertz Low Voltage Distribution Systems

FIGURES

1 Typical 400-Hz Medium-Voltage System 1a Typical 400-Hz Low-Voltage System 1b Typical 400-Hz Low-Voltage System 1c Major Components of FLEDS 1d Examples of a Typical FLEDS System 2 Example of Central Plant/Hangar Site Plan 3 Typical 400-Hz Central Plant 4 Single Line Diagram of a 60-Hz Low-Voltage

Switchboard 5 Single Line Diagram of a Frequency Conversion Assembly 24 6 Single Line Diagram of a Feeder Distribution Center . . 25 7 Single Line Diagram of a Utilization Service Assembly . 28 8 Voltage-Drop Calculation Single Line and Formulas . . . 35 9 Voltage-Drop Calculations Using Actual Values 10 Short-Circuit Analysis A-1 5,000-Foot Feeder Cable - Case Al A-2 10,000-Foot Feeder Cable - Case A2 A-3 15,000-Foot Feeder Cable - Case A3 A-4 20,000-Foot Feeder Cable - Case A4 A-5 25,000-Foot Feeder Cable - Case A5 A-6 30,000-Foot Feeder Cable - Case A6 A-7 40,000-Foot Feeder Cable - Case A7 A-8 One-Unit Steady State Load on Feeder - Case Dl A-9 Two-Unit Steady State Load on Feeder - Case D2

A-10 Four-Unit Steady State Load on Feeder - Case D3 A-11 Six-Unit Steady State Load on Feeder - Case D4 A-12 Eight-Unit Steady State Load on Feeder - Case D5 . . . 51 A-13 Initial One-Unit Load Plus Stepped One-Unit Load . . . 51 A-14 Initial Two-Unit Load Plus Stepped One-Unit Load . . . 52

A-15 Initial Three-Unit Load Plus Stepped One-Unit Load . . 52 A-16 Initial Four-Unit Load Plus Stepped One-Unit Load . . . 53 A-17 40-Foot Service Cable - Case Bl A-18 80-Foot Service Cable - Case B2 A-19 120-Foot Service Cable - Case B3 A-20 160-Foot Service Cable - Case B4 A-21 200-Foot Service Cable - Case B5 A-22 100-Foot Service Cable Plus Aircraft Cable-Case B11 . . 60 A-23 150-Foot Service Cable Plus Aircraft Cable-Case B12 . . 61 A-24 200-Foot Service Cable Plus Aircraft Cable-Case B13 . . 61 viii

Page

A-25 250-Foot Service Cable Plus Aircraft Cable-Case B14 . . 62 A-26 300-Foot Service Cable Plus Aircraft Cable-Case B15 . . 62 A-27 100-Ampere Load Change - Case C1 A-28 150-Ampere Load Change - Case C2 A-29 200-Ampere Load Change - Case C3 A-30 250-Ampere Load Change - Case C4 A-31 Initial One-Unit Load Plus Stepped Two-Unit Load . . . 69 A-32 Initial One-Unit Load Plus Stepped Three-Unit Load . . 69 A-33 Initial Three-Unit Load Plus Stepped Two-Unit Load . . 70 A-34 Initial Three-Unit Load Plus Stepped Three-Unit Load . 70 A-35 Initial One-Unit Load Plus Induction-Motor Starting . . 71 A-36 Initial Two-Unit Load Plus Induction-Motor Starting . . 71 A-37 Initial Three-Unit Load Plus Induction-Motor Starting . 72 A-38 Initial Four-Unit Load Plus Induction-Motor Starting . 72 A-39 Comparison of Feeder-Load Capacity at Different Voltage Levels A-40 Three-Section Passive-Element Filter A-41 System Connection for One (Case 1) or Two (Case 2)

Rectifier-Type Unit Loads B-1 Simplified Circuit Diagram and Formulas B-2 Typical 400-Hz Low Voltage Distribution System B-3 Typical 400-Hz Low Voltage System B-4 400-Hz Voltage Drop Calculations

TABLES

1 400-Hertz Aircraft Loads 2 System Demand Factors 3 Frequency Conversion Assembly Parameters 4 Utilization Service Assembly Parameters 5 Cable Parameters 6 Maximum Unit Loads on Feeders 7 Maximum 400-Hertz Medium-Voltage Cable/Lengths and

Loads 8 Maximum 400-Hertz Low-Voltage Cable Lengths 9 Typical Full-Load Efficiencies 10 400-Hz Load Calculations 11 400-Hz Central Plant Sizing 12 Determination of Acceptable Utilization Connections . . 34 A-1 Feeder Cable Length Versus Loads

A-2 Voltage Drop on a 15,000-Foot Feeder Cable A-3 90-kVA Line Drop Compensator's Per-Unit Impedance . . . 56 A-4 Service Cable Lengths Versus Loads and Feeder Cable

Lengths A-5 90-kVA Line Drop Compensator's Per-Unit Voltage Increase 64 A-6 Per-Unit Impedance Values Versus Feeder-Cable Lengths . 74 ix

Page

A-7 Resonant Frequencies and Harmonic Voltages B-1 Effective A.C. Resistance and Inductance Values for

THW, RHW Copper Single Conductors at 400-Hz B-2 Effective A.C. Resistance and Inductance Values for

XHHW Copper Single Conductors at 400-Hz B-3 Effective A.C. Resistance and Inductance Values for

THHN Copper Single Conductors at 400-Hz B-4 Effective A.C. Resistance and Inductance Values for

THW, RHW Aluminum Single Conductors at 400-Hz B-5 Effective A.C. Resistance and Inductance Values for

XHHW Aluminum Single Conductors at 400-Hz B-6 Effective A.C. Resistance and Inductance Values for

THHN Aluminum Single Conductors at 400-Hz B-7 Effective A.C. Resistance and Inductance Values for

THW, RHW Copper Three Conductor Jacketed Cable at 400-Hz

B-8 Effective A.C. Resistance and Inductance Values for XHHW Copper Three Conductor Jacketed Cable at 400-Hz

B-9 Effective A.C. Resistance and Inductance Values for THHN Copper Three Conductor Jacketed Cable at 400-Hz

B-10 Effective A.C. Resistance and Inductance Values for THW, RHW Aluminum Three Conductor Jacketed Cable at 400-Hz

B-11 Effective A.C. Resistance and Inductance Values for XHHW Aluminum Three Conductor Jacketed Cable at 400-Hz

B-12 Effective A.C. Resistance and Inductance Values for THHN Aluminum Three Conductor Jacketed Cable at 400-Hz

REFERENCES

Section 1: INTRODUCTION

1.1 Scope. This handbook presents information necessary for the proper design of the 400-Hertz (Hz) conversion, distribution, and utilization systems that supply power to aircraft and avionic support equipment for aerospace electrical subsystems. Special regard is paid to systems utilizing medium-voltage distribution.

1.2 Cancellation. This military handbook, MIL-HDBK-1004/5, cancels and supersedes NAVFAC DM-4.05, 400-Hertz Medium-Voltage Conversion/Distribution and Low-Voltage Utilization Systems, dated 30 March 1987.

1.3 Policy. It is Naval Facilities Engineering Command (NAVFACENGCOM) policy to provide our customers with reliable, maintainable, energy efficient 400-Hertz Systems for selected mission essential equipment. Solid state systems are preferred to reduce utility and maintenance costs.

Section 2: GENERAL CONSIDERATIONS

2.1 Usage. Aerospace electrical equipment generally operates at an input of 400 Hz. Electrical power is supplied by aircraft generators, which normally receive their energy from the aircraft engines. Three-phase aircraft generators deliver 3,000 to 4,000 RPM, depending upon engine speed, which is synthesized into 400-Hz output voltage for distribution to aircraft equipment.

Large aircraft may have several hundred electric motors, and the use of 400 Hz provides a considerable weight saving. Three-phase, 400 Hz, open-frame units (1 to 15 horsepower in size, with speeds of 12,000 to 24,000 revolutions per minute) developed for aircraft have weights averaging 2 pounds per horsepower (0.9 kilograms per horsepower). An open, dripproof, 60 Hz, 1,800 revolutions-per-minute unit of one horsepower weighs about 40 pounds (18 kilograms). For an expanded description of aerospace electric subsystems, see Fink and Beaty, Standard Handbook for Electrical Engineers (Section 23).

2.2 Types of Systems. Systems supplying 400 Hz for ground-power operations use frequency conversion equipment to change 60-Hz input to 400-Hz output. Rotary converters (motor generator sets) or solid state converters are used for this purpose. Fixed service point units to which avionics equipment and aircraft are connected are supplied from either nearby frequency conversion assemblies over a low-voltage feeder system or from a more remotely located 400-Hz central plant using medium-voltage feeders.

2.2.1 Rotary Converters. Rotary converters or motor generator (MG) sets are used for both low and medium voltage systems. These units are usually limited to installation in industrial locations due to the high level of noise produced.

2.2.2 Solid State Converters. Solid state converters are used only for low-voltage systems. The noise levels produced by these units as compared to MG sets are substantially less. The industry trend is to replace rotary machinery with solid state converters.

2.3 Distribution Systems. Fixed service point units to which avionics equipment and aircraft are connected are supplied from either nearby frequency conversion assemblies over a low-voltage feeder system or from a more remotely located 400-Hz central plant using medium-voltage feeders.

2.3.1 Low-Voltage Systems. Generally low-voltage systems distribute voltages less than 600 volts. Because the reactance of an electric system is greater at 400 Hz than at 60 Hz, attention must be given to both circuit length and conductor size to maintain acceptable voltage regulation.

Consequently, when loads and distribution distances increase, low-voltage systems require use of excessive feeder sizes and installation of numerous local frequency conversion assemblies. When numerous local frequency conversion assemblies are used, the reliability of the system is increased. A typical, 400 Hz low-voltage system is shown on Figures 1a and 1b. Detailed requirements are provided in Appendix B.

2.3.2 Medium-Voltage System. The development of a medium-voltage system which distributes three-phase, 400-Hz electric power at 4,160 volts can provide a more economical system. A typical, 400-Hz medium-voltage system is shown on Figure 1. Detailed requirements are provided in Appendix A.

2.3.3 Flight-line Electrical Distribution Set (FLEDS). A FLEDS system may be used in conjunction with the low-voltage or medium-voltage system. The components of an individual FLED set are shown in Figure 1c. A FLED system consists of a number of FLED sets which distribute 200Y/115 volts at 400 Hz to a maximum of two aircraft per FLED set. Normally the FLED system is procured and installed by NAVAIR, therefore, certain design characteristics to support the FLED system must be obtained from NAVAIR. Examples of a typical FLED system are shown in Figure 1d.

2.4 Surveys. Before replacing existing local low-voltage systems with a central medium-voltage system, make preliminary surveys to ensure the cost effectiveness of the replacement. Generally, consider only naval and Marine Corps facilities having existing 400-Hz requirements of 500 kilovoltamperes (kVA) or more for replacement with central medium-voltage systems.

2.4.1 Energy Conservation. Full load efficiency of the motor-generator set portion of frequency conversion assemblies ranges from 73 to 88 percent, depending on the size of the sets and the type of motor drive (induction or synchronous). The use of many sets, operating underloaded, lowers efficiencies, increases energy usage and cost, and probably increases maintenance and shortens operating life.

2.4.2 Economic Studies. When preliminary surveys and studies indicate that a central system may be economically feasible, a complete life-cycle cost analysis may be necessary. Make field measurements of the actual demand loads on each existing low-voltage 400-Hz system. Determine power requirements, characteristics, and locations of all existing utilization equipment and service points. The using agency shall advise of any changes in load requirements contemplated to serve anticipated mission changes so that this information may be included in determining the capacity required for a central system.

2.5 Types of Loads. Various types of loads on naval stations and Marine Corps bases require 400-Hz electric-power input. The power factor of these loads varies from 0.8 to 1.0.

2.5.1 Aircraft. The number of each type of aircraft serviced at naval stations and Marine Corps bases determine the total demand. For computation of 400-Hz aircraft loads, use the maximum load in Table 1 with a demand factor applied to the total load as given in Table 2.

Table 1 400-Hz Aircraft Loads

Aircraft Load Type Maximum kVA

A-4E 2.7 A-6E 12.2 E-2C 86.2 ** E-6A 400 * F-4J 23.5 F-14A 17.3 F-18 18.5 P-3C 70.8 S-3A 33.9

EA-6B 17

HH-3D 16.5

SH-60B 15.5

SH-60F 15.5

EGC-130 42.3

C/MH-53E 16

* four service cables required ** two service cables required

Table 2 System Demand Factors

Number of Aircraft Demand Factor Percent

1 100 2 90 3 83 4 77 5 71 6 66

7 to 9 61 10 to 12 50 13 to 15 45 16 to 21 40 22 to 40 31 41 to 60 28 Over 60 25

2.5.2 Avionics. In addition to aircraft, other loads such as repair shops for electronic equipment, require 400-Hz electric power for maintenance and testing. Load requirement shall be provided by the using agency in such cases.

2.5.3 Other Facilities. Research, development, training,and other types of facilities may require 400-Hz distribution systems. If the using agency cannot provide load requirements, compute such loads on a watts per square foot (square meter) basis when firm loads are not available (see MIL-HDBK- 1004/1, Electrical Engineering, Preliminary Design Considerations).

2.5.4 Special Requirements. Facilities indicated in paragraphs 2.5.2 and

2.5.3 have more stringent 600-Hz power requirements than the Fixed Point Utility System (FPUS) provides. Prior to supplying these facilities from FPUS, verify that equipment installed will not be damaged by FPUS power tolerances. Use local converters for these systems.

2.6 Consideration of System Voltage Parameters. The inductive contribution to the reactance voltage drop of 400-Hz systems is roughly seven times greater than that of 60-Hz systems, which necessitates certain modifications to conventional distribution and utilization system design to compensate for the increased voltage drop. Specifications for limiting voltage drop are covered in later sections, but the following requirements apply generally to 400-Hz systems.

2.6.1 Development of Guidelines for Parameters. Voltage drop is always a concern in the design of 60-Hz systems. Give even closer attention to voltage parameters in the design of 400-Hz systems because the voltage drop is much larger. When designing 400 Hz systems, take into account the effects of varying cable lengths and connected loads.

2.6.2 Items Affecting Design. The designer must consider maximum loads and applicable cable-length limitations. Based on acceptable end-voltage requirements, determine maximum allowable cable and equipment impedances.

Methods to be used for compensation or elimination of impedance are important also. Overcompensation of voltage drop can be as bad as under compensation.

The voltage range which provides satisfactory aircraft power is the key element to an acceptable 400-Hz distribution system.

2.6.2.1 Acceptable End-Voltage Requirements. The voltage range of 108 volts minimum to 118 volts maximum specified in MIL-STD-704, Aircraft Electric Power Characteristics, is the operating voltage range of the equipment inside the aircraft. This operating voltage range takes into account a 0- to 5-volt drop in the electrical distribution system inside the aircraft. Accordingly, the full-load and no-load voltage at the interface (aircraft connection input point) should never drop below 113 volts nor rise higher than 118 volts.

These parameters also apply to the input to the FLEDS system.

2.6.2.2 Equipment and Cable Parameters. Rotary equipment and cable parameters for use by the designer are given in Tables 3, 4, and 5. Some parameters directly affect voltage drop; other parameters are provided for information only. Equipment and cable descriptions correspond to those shown on Figure 1. These values are used to determine the maximum cable lengths (e.

g., medium voltage feeders and low-voltage service circuits and aircraft cable connections), plus the permissible number of unit loads per feeder cable.

Equipment providing lower voltage-drop parameters is acceptable.

2.6.2.3 Unit Loads. The unit-load basis used herein for voltage-drop calculations is individual 100-ampere, 0.8-power-factor loads. Two 100-ampere unit loads can be supplied by a 75-kVA utilization service center.

2.6.3 Maximum Cable Length and Loads. To determine maximum cable length and loads and the effects of other system parameters, various conditions were analyzed. The analysis is included in Appendix A. Table 6 shows the maximum number of unit loads that can be connected to a medium-voltage feeder and meet minimum voltage levels at the utilization service assembly.

2.6.3.1 Allowable Medium-Voltage Distribution Level. Provide the medium-voltage distribution level of 4,160 volts. Commercial airports are using 400-Hz systems with voltages up to 2,400 volts. However, in these cases the feeder lengths (or distances) are much shorter than the feeder lengths on the systems used by the naval and Marine Corps Stations. The 2,400-volt system provides no appreciable cost savings although it requires a reduction of the maximum feeder length to one-third of that acceptable on a 4,160-volt system which serves the same load. If feeder lengths are not reduced, then the 2,400-volt system is capable of serving only one-third of the load that can be fed by a 4,160-volt system.

2.6.3.2 Maximum Cable Lengths. Normally, do not exceed cable length values given in Table 7 for medium-voltage cables and in Table 8 for low-voltage cables. The reason that only four unit loads were permitted in Table 7 is that the effects of the low-voltage cables were considered. This was not the case in Table 6. The use of four loads maximum means that the steady-state load plus the step-load can never exceed 400 amperes as shown in the step-load capability columns.

2.6.3.3 Exceeding Limiting Cable Lengths. Justify exceeding the normal cable length limits only as follows:

a) When the limitation requires another central plant, the 15,000-foot feeder cable length may be increased by 10 percent. Increases over 5 percent must be approved by the Naval Facilities Engineering Command

(NAVFACENGCOM).

b) Due to special site conditions, the aircraft cable length at such sites may be increased to 70 feet in length, only if approved by

NAVFACENGCOM.

2.6.3.4 Rationale of Maximum Cable Lengths. The essential factor in determining acceptable cable lengths is the 113-volt limitation at the aircraft interface point. Meet this limitation in the following manner:

a) Permit a steady-state voltage droop to 3,918 volts on the 4,160-volt end of the medium-voltage distribution system. Droop is defined as the absolute change in voltage between the steady-state no-load condition and the steady-state full-load condition. This equates to 113 volts on the low-voltage distribution system or 0.942 per unit volts (using base voltages of 4,160 volts and 120 volts) at the terminals of the utilization service assembly.

b) Make up for the low-voltage system droop by compensating for the low-voltage system's reactance.

Table 3 Frequency Conversion Assembly Parameters

1. Synchronous Units with Revolving Fields

Motor Generator

Power Factor 1.0 0.8 Voltage 460 volts 575 volts Frequency 60 hertz 400 hertz Full load Synchronous Unit Current 420 amperes 314 amperes Field current 8.86 amperes 26.7 amperes Current to bridge air gap 3.9 amperes 17.01 amperes No Load Field current 3.8 amperes 14.435 amperes Current to bridge air gap 3.6 amperes 14.03 amperes Number of poles 6 40 Full load rating 400 horsepower 312 kVA Synchronous speed 1,200 rpm 1,200 rpm

2. Transformer

Rating 312 kVA Voltage 575 to 4,160 volts Resistance 1 percent Reactance 5 percent Current base 313.3 to 43.3 amperes

Table 4 Utilization Service Assembly Parameters

1. Transformer

Rating 75 kVA Voltage 4,160 to 208Y/120 volts Resistance 1 percent Reactance 5.9 percent Current base 10.4 to 208 amperes

2. Line Drop Compensator

Rating 90 kVA Rating 75 kVA Voltage 208Y/120 volts Voltage 208Y/120 volts Compensation Compensation 5 percent -j.024 ohms 6 percent -j.034 ohms 6 percent -j.029 ohms 8 percent -j.046 ohms 7 percent -j.034 ohms 10 percent -j.058 ohms 8 percent -j.039 ohms 12 percent -j.069 ohms 9 percent -j.042 ohms 14 percent -j.081 ohms 12 percent -j.058 ohms 16 percent -j.092 ohms 14 percent -j.067 ohms 16 percent -j.077 ohms 18 percent -j.086 ohms 20 percent -j.096 ohms

3. Passive-Element Filter

Resistance 0.6 ohms Reactance 2.3 millihenries Capacitance 68 microfarads

Table 5 Cable Parameters

1. Medium-Voltage Feeder Cable

Size No. 2 AWG Conductors one 3-conductor Voltage rating 5 kV at a 100 percent insulation level Insulation Type EPR or XLP Cable assembly impedance values per 1,000 feet:

Resistance 0.098 ohms Inductance 101 microhenries Capacitance 0.1142 microfarads

2. Low-Voltage Service Cable

Size 4/0 AWG Conductors one 3-conductor Voltage rating 600 volts Insulation Type XHHW Cable assembly impedance values per 1,000 feet:

Resistance 0.085 ohms Inductance 70.8 microhenries Capacitance 0.0962 microfarads

Table 6 Maximum Unit Loads on Feeders (1)

Cable Length Bus 3 Number of No-Load Feet Per-Unit Volts (2) Unit Loads Volts 1-n 15,000 0.9917 One 119

0.9834 Two 118

0.9751 Three 117

0.9668 Four 116

0.9585 Five 115

0.9502 Six 114

0.942 Seven 113 (3)

10,000 0.9945 One 119.3

0.9890 Two 118.7

0.9835 Three 118.0

0.9780 Four 117.4

0.9725 Five 116.7

0.9670 Six 116.0

0.9610 Seven 115.3

Table 6 (Continued) Maximum Unit Loads on Feeders (1)

Cable Length Bus 3 Number of No-Load Feet Per-Unit Volts (2) Unit Loads Volts 1-n

0.9560 Eight 114.7

0.9505 Nine 114.0

0.9450 Ten 113.4

5,000 0.9973 One 119.6

0.9919 Three 119.0

0.9865 Five 118.4

0.9811 Seven 117.7

0.9757 Nine 117.1

0.9703 Eleven 116.4

(1) Voltage regulated on the high-voltage side (4,160 volts) of the frequency conversion transformer assembly.

(2) The utilization service center transformer per-unit base is 208/120 volts. See Appendix A for detailed analysis of the system.

(3) The underlined rows denote the maximum number of unit load wherein voltage does not drop below 113 volts.

Table 7 Maximum 400-Hertz Medium-Voltage Cable/Lengths and Loads

Individual Step Load Capability

Feeder Cable 100-Ampere, at 0.8 Power Factor Length 0.8-Power-Factor, Steady State Step Load Feet Steady State Load Addition

Unit Loads Amperes Amperes

0 400 100 300

15,000 4 200 200 300 100 400 0

Table 8 Maximum 400-Hertz Low-Voltage Cable Lengths (1)

Service Cable Length Feet Aircraft Cable Length Feet 250 60

(1) Based on a 100-ampere, 0.8-power-factor unit load.

Section 3: DESIGN REQUIREMENTS

3.1 Design Procedures. Preliminary design procedures for 400-Hz systems are the same as those for 60-Hz systems (loads, distances, etc.) so that the system design will meet project requirements.

3.1.1 Data Gathering. Determine the following data regardless of whether an entirely new installation is being designed or an existing facility is being changed or upgraded. While a new facility allows more leeway in the design approach, the available load data ordinarily will not be as precise.

Gather or design concurrently with the 400-Hz system the following data:

a) Facility electrical site plans with locations of all aircraft service points.

b) Facility electrical building plans having 400-Hz loads or used to house 400-Hz equipment.

c) Determination of all 400-Hz load specifications including both requirements for new loads and replacement or reuse of any existing 400-Hz low-voltage conversion distribution system.

d) Data on the proposed or installed 60-Hz primary distribution system.

3.1.2 System Layout. From the above data, develop a system layout which locates possible distribution line choices and pinpoints load connection points.

3.1.3 Equipment Layout. After the development of the system layout, make equipment locations based on the design aspects delineated in the following paragraphs.

3.1.4 Design Aspects. The 400-Hz system consists of the following major elements:

a) The central power plant.

b) The medium-voltage distribution system.

c) The low-voltage utilization system.

The following considerations apply to the entire 400-Hz system design.

3.1.4.1 Protective Device Operation. Always consider the thermal and magnetic characteristics for 400-Hz circuit protective devices. Operation at 400 Hz causes more heat rise in current-carrying parts than does operation at

60 Hz. There is also decreased electromagnetic pull on magnetic-trip elements. Because all current ratings of devices are affected to different degrees, consider applicable derating factors during design phase.

Check with the appropriate manufacturers to determine ratings appropriate to the equipment. Also, specially calibrate thermal and magnetic characteristics of protective devices for use on 400-Hz systems.

3.1.4.2 Surge Arresters. Provide Surge arresters for 60-Hz system protection where necessary (see MIL-HDBK-1004/2, Power Distribution Systems).

In general, the only exposed lines will be those of the 60-Hz distribution system. Therefore, provide 400-Hz protection only for devices whose insulation capability is below that provided by the 60-Hz surge protection, which will normally protect the medium-voltage 400-Hz devices. Varistors available for use with the low-voltage 400-Hz system can limit surges to about

1.7 times the peak voltage; provide where required. The using agency will furnish details of any equipment requiring other than varistor protection.

For 400-Hz electronic equipment sensitive to voltage spikes as low as 1.5 times the nominal voltage, zener-type suppressors (silicon-avalanche diodes) can limit the voltage to 1.38 per unit. Provide these zener-type suppressors normally on the equipment terminals.

3.1.4.3 Bus and Cable Material. Because of its lower resistance, use copper, except where such use is clearly impracticable. Fully justify the use of anything other than copper in the design analysis (see Section 4).

3.1.4.4 Conduit. The presence of magnetic materials in the vicinity of electric conductors increases the flux density thereby increasing resistance and inductance. Therefore, use nonmagnetic materials, such as aluminum or plastic, for all raceways. Use nonmagnetic materials, such as aluminum, bronze, or plastic, as appropriate, for cable terminations, cable clamps, and other equipment.

3.2 Medium-Voltage Distribution System Design. Because the 15,000-foot maximum feeder length dictates the number and location of acceptable central plant sites, make the layout of the medium-voltage feeder lines first.

3.2.1 Type of Distribution. Generally, use raceway systems for distribution of 400-Hz circuits. Bare, aerial 400-Hz systems are precluded because of the excessive inductance of such circuits. Overhead distribution systems using preassembled, messenger-supported, insulated cable are acceptable in areas where lightning storms are few and where aircraft clearance criteria do not apply. In areas where protection against lightning-induced surges is required, use surge arresters specifically designed for use at 400 Hz for protection of underground-to-aerial risers.

The use of 60-Hz arresters is ineffective and hazardous because of the capacitive elements of arresters. The change in frequency changes the capacitance and, therefore, disturbs the even-voltage gradients which prevent premature sparkover.

3.2.2 Practicable Distribution Area. Considering the 15,000-foot limit on the length of a medium-voltage feeder and the impracticality of straight-path feeder installations, the central plant service area is likely to be limited to a 2.5-mile radius. Therefore, site configurations permitting one central plant should serve an area up to 5 miles in diameter (see Figure 2).

Figure 2 Example of Central Plant/Hangar Site Plan

3.2.3 Shunt Reactor Capacity. Install shunt reactors on each

medium-voltage feeder to balance the capacitance of that feeder. Size the reactor so that the no-load power factor of each medium-voltage feeder, and thus the system, is close to unity. The nominal kilovoltampere reactive (kvar) rating of each reactor must be greater than its feeder cable's capacitive kvar to provide a lagging power factor, but it should not be more than 10 kvar as seen by the overall system. Indicate nominal ratings based on the maximum allowable specified capacitance of each medium-voltage feeder.

Install shunt reactors on each medium-voltage feeder as indicated on Figure 1.

3.2.3.1 Field Adjustment. Adjust the nominal indicated rating of the shunt reactor to suit the actual capacitance of the cable provided. Make field measurement of the actual capacitance after the cable is installed, and the correct shunt reactor tap can be chosen to the closest unity power factor setting.

3.2.3.2 Nominal Rating Sizing. An example of nominal shunt reactor sizing follows. If the nominal rating calculated is less than 10 kvar for a feeder, the shunt reactor may not be necessary to decrease voltage drop. However, its installation provides for capacitive discharge which increases operator safety.

System voltage (V.S-) = 4,160 volts Feeder Length = 1 mile Maximum capacitance allowed = 0.603 microfarads per mile Capacitive reactance (X.C-) = -j660 ohms at 400 hertz

Nominal rating = V.S- squared = (4,160) squared = 26.2 1,000X.C- 1,000 (660)

Required nominal rating = 26.2 kvars

3.3 Central Plant Design. A central plant is the point where the station's medium-voltage distribution system 60-Hz (in rare cases 50-Hz) input is converted to 400-Hz power for distribution by a 400-Hz feeder distribution center to the station's medium-voltage distribution system. A typical 400-Hz central plant is shown on Figure 3. Normally, the plant will be an unmanned facility.

3.3.1 Reliability. The continuous operation of the central 400-Hz medium-voltage system is extremely critical. Standby components are required at the central plant to ensure no major loss of 400-Hz electric power.

3.3.2 System 60-Hertz Input Power. The design of the 60-Hz input system is covered in this handbook only to the extent of providing necessary 400-Hz system reliability. For this reliability, two primary inputs from different feeders or electric sources of 60-Hz electric power are required at the central plant.

3.3.2.1 Primary Feeder Source. Generally, provide a prime and an alternate feeder from the installation's 60-Hz primary (medium-voltage) distribution system. An area having a 400-Hz load large enough to require a central medium-voltage system is an area with a load density which is both large and sufficiently important enough to require more than one 60-Hz primary distribution feeder.

3.3.2.2 Diesel-Engine Generator Source. Provide an emergency diesel-engine generator system (see MIL-HDBK-1004/4, Electrical Utilization Systems) as the alternative source where provision for an alternative feeder is more costly than a standby power system. Provide diesel-engine generator capacity of at least 80 percent of the frequency conversion plant's firm capacity. Frequency conversion plant firm capacity is the sum of the rated capacities of all frequency conversion assemblies, with the largest unit not operating. Where required by the activity, provide 100-percent diesel-engine generator capacity. Provide diesel-engine generator sets with both manual and automatic transfer modes which start automatically on loss of normal power. Where more than one diesel-engine generator set is provided, provide units capable of being automatically paralleled. Provide switches to permit testing of diesel-engine generators without assuming load. The most economical diesel-engine generator voltage is generally the input voltage to the frequency conversion assembly.

3.3.2.3 Transformer. Because the frequency conversion assemblies are low-voltage input devices, transformers are necessary to stepdown primary power. No facility should depend on only one transformer, since this can result in a complete shutdown of the 400-Hz system. Require duality of transformers. Each transformer's rating shall be not less than 80 percent of the frequency conversion plant's firm capacity. When transformers of the outdoor substation type (see MIL-HDBK-1004/2) are installed adjacent to the central plant as shown on Figure 3, they can be used to supply the central plant's 60-Hz low-voltage switchboard (see MIL-HDBK-1004/3, Switchgear and Relaying) as shown on Figure 4.

3.3.3 System 400-Hertz Conversion Capacity. Firm power is power which is available even under emergency conditions. Determine the firm frequency conversion capacity of the central plant by the loads served and a 15- to 20-percent additional capacity for future loads. Provide one extra unit for standby (i.e., emergency use). If the requirement for the standby unit and for future capacity necessitates more units than for the present load with maintenance backup, incremental construction may be desirable. Such planning is acceptable as long as future space and capacity provisions for ancillary devices are covered fully in the first-design stage.

3.3.4 Frequency Conversion Assemblies. Ratings as shown in Table 3 provide satisfactory operation. When frequency conversion assembly performance is combined with a properly designed distribution and utilization system, it provides 400-Hz power to aircraft loads. This meets the requirements of MIL-STD-704. Figure 5 shows a typical frequency conversion assembly.

3.3.4.1 Motor Generator Units. Use standard units manufactured to support both military and commercial airports.

a) Output voltage. The most preferable output voltage is that of the distribution system or 4,160 volts; however, this equipment is not yet commercially available. Normally, specify a 575-volt motor generator output, except when the system can reuse existing motor-generator sets that meet, or can be adapted to meet, criteria. In such cases use new motor-generator sets which match the output voltage of the existing sets.

b) Unit capacity. Normally, provide 312-kVA generators (the largest capacity now being produced as a standard by more than one manufacturer), since this size is usually the most economical and has the maximum full load efficiency (see Table 9). Use other unit capacities when adequately justified.

c) Vertical shaft construction. Vertical-shaft construction minimizes floor space requirements. A 312-kVA vertical motor-generator set, weighing as much as 6 tons (5500 kilograms), is approximately 4 feet (1.2 meters) square by 6.5 feet (1.98 meters) high. The same size horizontal unit can require a 6-foot (1.8 meters) by 7-foot (2.1 meters) floor space and can be almost as high. These areas and loads do not include the rest of the assembly requirements. Provide a clear space of at least 3 feet (0.9 meter) above the motor generator to allow for maintenance of the vertical unit.

Table 9 Typical Full-Load Efficiencies

Input Output

Efficiency Horsepower (1) Percent kVA kW 400 312 250 88 300 250 200 87 250 219 175 86 250 187 150 85 200 156 125 83 150 125 100 80 100 93.8 75 78 100 75 60 76 75 62.5 50 75

(1) Nearest standard size. Actual input horsepower may vary, depending upon the individual manufacturer.

3.3.4.2 Other Components. Figure 5 shows the other components that are provided as a part of a packaged frequency conversion unit. This ensures that units are factory designed to meet performance requirements.

a) Voltage step-up. Match the kVA of the low-to-medium-voltage step-up transformer specifically to the generator capacity. Provide voltage sensing devices on the transformer output to regulate the voltage of the motor-generator set. This regulation ensures that the voltage level at the medium-voltage bus of the 400-Hz feeder distribution center remains constant under any steady-state load condition.

b) Output disconnect. Use a vacuum contactor to disconnect the output of the unit rather than a circuit breaker, because the contactor is both smaller and less costly. In addition to overload and short-circuit protection, a contactor can provide overvoltage, undervoltage, underfrequency, and reverse-power control features, which are not available from a fused switch.

3.3.5 Feeder Distribution Center. The feeder distribution center serves as the 400-Hz medium-voltage system control point. Feed the output of all the frequency conversion assemblies into a common bus which supplies all the 400-Hz medium-voltage feeders. It serves as a point to measure 400-Hz usage and to correct the system's no-load power factor to almost unity by balancing the capacitance of each feeder cable. Figure 6 shows a typical feeder distribution center.

3.3.5.1 Metering. Normally, do not install recording type meters in an unmanned facility. If records are required, transmit them to a point where personnel are available to maintain orderly record keeping and storage.

3.3.5.2 Shunt Reactors. An example of shunt reactors sizing is shown in paragraph 3.2.3.2.

3.3.6 Central Plant Buildings and Other Equipment Shelters. The same reliability standards cited for equipment shall also apply to structures sheltering any part of the 400-Hz system or its environmental support systems.

Provide spaces around equipment for ease and convenience of testing, maintenance, serving, and equipment removal. Provide a minimum 5-foot (1.5-meter) aisle space around each frequency conversion assembly. Larger aisles may be required to allow for replacement of defective equipment. Design buildings with knockout panels for future expansion. Control mechanical systems automatically by thermostats which maintain correct temperatures under all operating conditions. Provide roof exhaust fans as required. Provide louvers and air handling units for air supply which have filters which prevent entrance of dusty air into the operating parts of the motor-generator sets (see MIL-HDBK-1003/7, Steam Power Plants - Fossil Fueled). Include other considerations normally provided for diesel-engine generators and switchgear rooms.

3.4 Low-Voltage Utilization System Design. A low-voltage utilization system extends from the utilization service assembly as shown in Figure 1 or from the solid state frequency conversion assembly as shown in Figures 1a and 1b to the parked aircraft. The layout of aircraft parking defines the location of the parked aircraft units (see MIL-HDBK-1021/2, General Concepts for Pavement Design) which will define the locations and number of utilization service assemblies or solid state frequency conversion assemblies and determine if a single, low or medium-voltage feeder is capable of supplying only one hangar, several hangars, or aprons. Integrated design with the aircraft fixed point utility systems (see MIL-HDBK-1028/6, Aircraft Fixed Point Utility Systems).

3.4.1 Low-Voltage System Equipment. In addition to a utilization service assembly as used on a medium voltage system, each low-voltage system includes the individual aircraft's supply source or fixed service point unit.

3.4.1.1 Utilization Service Assemblies. To assure satisfactory operation, provide utilization service assemblies with components as shown on Figure 7.

a) Step-down transformers. Normally, provide step-down transformers rated 75 kVA and with a three-phase 208Y/120-volt output. The terminal rating of 208Y/120 volts is consistent with the usually higher voltage rating of distribution equipment over the typical 200Y/115 volts of utilization equipment. The higher distribution voltage level allows for voltage drop between the distribution and utilization points. The load served is generally no more than two, 100-ampere, 0.8-power-factor unit loads (34.5 kVA each).