Guide Preparing Design Proposal

8/9/2019 Guide Preparing Design Proposal

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Guide toPreparing a Design Proposal

for Paralleling Customer Generation

with an Electric Utility

Published by

National Electrical Manufacturers Association

1300 North 17th StreetRosslyn, Virginia

Copyright 1998 by the National Electrical Manufacturers Association. All rights including translation intoother languages, reserved under the Universal Copyright Convention, the Berne Convention for theProtection of Literary and Artistic Works, and the International and Pan American Copyright Conventions.


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Guide to Preparing a Design Proposal for Page iParalleling Customer Generation With an Electric Utility

TABLE OF CONTENTS

THE PROCESS, PROCEDURES, AND STEPS ..........................................................................1

Introduction: A Summary of the Process ..................................................................................... 3

The Role of the System Designer ................................................................................................. 3

A Description of What is Contained Within This Guide.................................................................4

STEPS IN DEVELOPING THE PROPOSAL................................................................................7

STEP 1: IDENTIFICATION OF CUSTOMER NEEDS .................................................................9

I. System Identification.......................................................................................................9

II. System Power Capacities (enter data) .........................................................................10

III. Identify Nature of Contacts Between Customer and Utility to DateRegarding the Proposal ................................................................................................10

STEP 2: IDENTIFY UTILITY REQUIREMENTS, RESTRICTIONS, CAPABILITIES .................11I. Utility Capacity (for each service) .................................................................................11

II. Requirements and Restrictions (for each service)........................................................11

STEP 3: IDENTIFY ENGINE GENERATOR REQUIREMENTS................................................15

STEP 4: PREPARING UTILITY INTERCONNECT PROPOSAL...............................................17

I. System Description of Installation.................................................................................17

II. Configure One-Line Diagram........................................................................................17

III. Bill of Materials ............................................................................................................. 18

APPENDICES TO STEPS ONE FOUR................................................................................... 19

APPENDIX TO STEP 1: Identification of Customer Needs .......................................................21

A1-1 Importing Power/Exporting Power ................................................................................21

A1-2 Installation of Generator with Capacity Greater than Baseload, Not Designed orIntended to Export Power .............................................................................................22

A1-3 Momentary vs. Sustained Parallel Operation with Utility ..............................................22

A1-4 Ramp (or Soft Loading) vs. Immediate Loading ...........................................................23

A1-5 Peak Shaving vs. Curtailment.......................................................................................23

A1-6 Financial Consideration ...............................................................................................24

APPENDIX TO STEP 2: Identify Utility Requirements, Restrictions, Capabilities .....................25

A2-1 Typical Utility Information Required ..............................................................................25

A2-2 Utility Operating Objectives...........................................................................................25

A2-3 Secondary Distribution Circuits.....................................................................................26

A2-4 Location of Your Installation in the System...................................................................26

A2-5 User Circuit Configurations...........................................................................................26

A2-6 Primary Circuit Configurations......................................................................................27

A2-7 Responsibility of Costs Associated with Interconnection and Line Extension/LineUpgrade Considerations ...............................................................................................27


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Page ii Guide to Preparing a Design Proposal forParalleling Customer Generation With an Electric Utility

A2-8 One-Line Diagrams of Typical Installations ..................................................................27

A2-9 Summary of Considerations..........................................................................................35

APPENDIX TO STEP 3: Identify Engine Generator Requirements ........................................... 37

A3-1 Type of Generators.......................................................................................................37

A3-2 System Voltage Classes...............................................................................................38A3-3 Ground Fault Protection................................................................................................38

A3-4 Paralleling System Protection.......................................................................................41

A3-5 Prime Mover..................................................................................................................43

A3-6 Available Short-Circuit Currents....................................................................................45

A3-7 Protective Switching Devices........................................................................................45

A3-8 Kilowatt Load Control....................................................................................................46

A3-9 VAR/Power Factor Control............................................................................................46

APPENDIX TO STEP 4: Preparing Utility Interconnect Proposal ...............................................47

The Proposal .......................................................................................................................... 47

EXAMPLE...................................................................................................................................49

EXAMPLE CHECKLIST AND PROPOSAL.................................................................................51

Example Checklist.................................................................................................................. 51

STEP 1: Identification of Customer Needs Example ..............................................................51

I. System Identification......................................................................................................... 51

II. System Power Capacities (enter data) .............................................................................52

III. Identify Nature of Contacts Between Customerand Utility to Date Regarding the Proposal ......................................................................52

STEP 2: Identify Utility Requirements, Restrictions, Capabilities Example ............................ 53

I. Utility Capacity (for each service)......................................................................................53

II. Requirements and Restrictions (for each service). ........................................................... 53

STEP 3: Identify Engine Generator Requirements Example ..................................................56

Example: System Description, Operating Sequence, Scope of Work...................................59

Example: System One-Line Diagram....................................................................................59

Example: Bill of Material, Including Equipment Type and Ratings........................................61

GLOSSARY................................................................................................................................65


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Guide to Preparing a Design Proposal for Page iiiParalleling Customer Generation With an Electric Utility

National Electrical Manufacturers Association. It is illegal to resell or modify this publication.

FOREWORD

Most facility electrical systems must interface with an electric utility company grid inorder to purchase their power requirements. Providing on-site generators for back-uppower when the utility has failed will not usually alter the requirements for the interface

because the utility source is kept separate from the generator output. In the past fewyears, however, on-site generators have been employed to provide more than just back-up power. They are being operated in parallel with the utility supply to profit from theeconomic advantages of cogeneration and peak electric demand shaving. This type ofoperation requires additional consideration when designing the utility interface.

Cogeneration systems utilize the waste heat from the engine-generator to lowerboth heating fuel and electric energy usage charges. Precisely matching the heatdemand to the electric power demand on the engine generator usually requiresoperation of the generator in parallel with the serving electric utility. This allows theengine to be run at a constant output despite changes in individual electrical loads.

Peak shaving systems reduce the electric utility demand penalty charge bysupplying a portion of the facility power with the on-site generators during times of highenergy usage. Paralleling the generator with the utility during these periods simplifiesthe task of providing a constant, predictable load.

Paralleling generators with the serving utility for more than a fraction of a second isreferred to as maintained parallel operation, as opposed to the momentary paralleling ofsources for no-break transfer. This maintained parallel operation has a considerableeffect on the design of the interface with the electric utility. Whether it is needed forcogeneration, peak shaving, or graduated transitional loading and unloading of thegenerators in an emergency system, the requirements are similar. The generators

require additional protection and there must be very rapid separation of the two ACsources if one of them malfunctions. The utility company will have requirements thatmust be considered also.

The selection of the final design is usually determined by the return on investmentof the new system with consideration given not only to installed cost but also to costavoidance, reliability, etc. The proposed design may change due to further evaluationof these factors as time progresses. The purpose of this guide is to take the mysteryout of interface design for parallel operation by providing sound engineering guidelinesand also to assist the designer with the utility approval process. Careful, up-frontplanning, design, and proposal preparation are the keys to assuring successful

coordination and approval by the electric utility company.


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Page iv Guide to Preparing a Design Proposal forParalleling Customer Generation With an Electric Utility



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Guide to Preparing a Design Proposal for Page 1Paralleling Customer Generation With an Electric Utility Section 1 The Process, Procedures, and Steps


SECTION 1

THE PROCESS, PROCEDURES, AND STEPS


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Page 2 Guide to Preparing a Design Proposal forSection 1 The Process, Procedures, and Steps Paralleling Customer Generation With an Electric Utility



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Introduction: A Summary of the Process

The time span between the initial decision for parallel operation and the finalinstallation and operation acceptance can be several years. This time is spent in:

Extent 1. Communication with the user (client)

of 2. Communication with the utility company

this 3. Preliminary design, including drawings

Guide 4. Prepare the utility proposal

5. Preliminary approval by utility

6. Final design and drawing by system designer

7. Bidding, purchasing, choice of supplier

8. System design approved by utility

9. Manufacturing lead times

10. Installation

11. Testing and start up

12. Operation

Careful effort expended in the first two steps will save time and money during thefollowing steps. Proper design and attentiveness to utility company requirements willmake the remainder of the project go smoothly.

It is the intent of this publication to provide guidance to the system planner to assuresuccessful completion of the installation in a timely manner.

The Role of the System Designer

The system designer is responsible for the interface design. He also conducts muchof the communication with the electric utility company until an agreement on design isreached. He must provide a design that meets the requirements of both the facility andthe utility company.

In examining the facility, the following items must be addressed:

1. Will the generators provide back-up power if the utility fails?

2. Is the interface between the two systems located physically within the generatorcontrol switchgear?

Most utility companies have certain published requirements for intertie with on-sitegenerators. These publications are generally divided into many different design


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National Electrical Manufacturers Association. It is illegal to resell or modify this publication. National Electrical Manufacturers Association. It is illegal to resell or modify this publication.

considerations. The differences are based upon generator type and size as well as theconfiguration of the utility company's lines. Once a particular recommendation isselected to match the proposed installation, it is time to make an initial contact with theserving electric utility.

The system designer must be selective when negotiating with utility companyemployees. Few of them have the authority to approve a parallel operation/installation.It is important to identify individuals with this authority prior to beginning technicaldiscussions. All understandings and changes of any importance should be recorded andconfirmed in writing. It will serve you well to insist upon written confirmations to allmatters agreed upon.

The degree of cooperation extended by the utility company will vary, dependinggreatly upon their need for relief during peak power consumption periods. If they needadditional generation, they will be considerably easier to work with than if they do notwant customer generators on-line. Another important factor which will influence theutility company position is the thoroughness and technical competence of the systemdesigner's proposal.

A Description of What is Contained Within This Guide

This guide will take you step-by-step through the process of designing thegenerator-utility interface and gaining utility company approval. The process begins withexamining the characteristics of the utility system. You will be advised how to procurethe information and the important considerations. Satisfying the utility company'sconcerns about the safety and integrity of their system is the most important andchallenging aspect of this task. Their approval is necessary before the generator(s) canbe put on-line.

An examination of the requirements of the on-site generator system must beundertaken. The equipment requirements are heavily dependent upon the mode ofoperation desired. We will look at the two types of generators which can be employedand discuss the advantages and limitations of each, as well as generator controloptions. Prime movers will also be discussed in regard to the different types and howthey are controlled.

Once the utility system is studied and understood and the generating systemrequirements are defined, the interface design may begin. The acceptance of the designby the utility company will depend greatly upon their confidence in what the systemdesigner proposes. Their primary concern will be their ability to continue providing safe,continuous, and reliable power to their customers.

The proposal made to the utility company for parallel operation of on-site generatorsis the document by which the proposed operation and interface design are judged. Themore precise and informative it is, the better the chance of rapid and timely acceptance.Section 2 of this guide will describe in detail the necessary information which should beincluded in this proposal. Most utility companies will not even discuss potential


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acceptance of any aspect of the design until a proposal is made. The proposal istherefore the starting point for ensuing negotiations.

The guide provides a glossary of terms and definitions.


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Proposal Flow Chart

Determine

User Requirements

Determine Utility Company

Requirements

Operation

Startup

Installation

Manufacture

Systems Designer Approves

Final Approval by Utility

Supplier Prepares

Submittal to

Systems Designer

Suppliers Chosen

Suppliers Quote

Requests for Quote

Per Specifications

Final Drawings & Specifications

Prepared by System Designer

Pre-Approval

By Utility

System Designer

Draws Up Proposal

To Include One-Line Diagram

System Designer

Extent of Guide


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Guide to Preparing a Design Proposal for Page 7Paralleling Customer Generation With an Electric Utility Section 2 Steps in Developing the Proposal


SECTION 2

STEPS IN DEVELOPING THE PROPOSAL


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Page 8 Guide to Preparing a Design Proposal forSection 2 Steps in Developing the Proposal Paralleling Customer Generation With an Electric Utility



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STEP 1: Identification of Customer Needs

The first step in the process of preparing a proposal to the electrical utility for

parallel operation of on-site engine generator sets is to clearly identify the customerneeds and expectations.

Complete the following checklist (where applicable) by checking or entering data todefine the basic system operating modes that develop the basis for utilityinterconnection:

Reference material for Step 1 can be found in the Appendix to Step 1.

I. System Identification

1. Will system (check one of three below):

a. Import power only _________

b. Export power only _________

c. Import/export power _________

2. Identify source of primary power (check one):

a. On-site generator set _________

b. Utility _________

3. Identify type of user system (check one of the three situations below):

a. Momentary parallel operationwith utility (milliseconds)for block or immediate loading _________

b. Short time parallel operation (seconds)for ramp loading _________

c. Long-time parallel operation (hours)

with utility _________

4. Will the generator set be used for standby? Yes No


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II. System Power Capacities (enter data)

1. Describe proposed capacity

a. Facility peak demand kW kVA

b. Facility average load kW kVAc. Facility minimum load kW kVA

d. Emergency/standby load kW kVA

e. Proposed installed generation kW kVA

2. Describe potential future power capacity:

Is there potential for future expansion of on-site power requirements?

Yes No

If yes:

a. Future average load kW kVA

b. Future expansion generation kW kVA

III. Identify Nature of Contacts Between Customer and Utility to DateRegarding the Proposal

The user has (check appropriate box):

Yes No

1. Established appropriate

utility contacts

2. Obtained rate structures and

explored utility incentive programs

3. Initiated financial feasibility studies

4. Obtained utility

interconnection guidelines

If the answer to any of these questions is No, the system designer should initiate theaction.


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STEP 2: Identify Utility Requirements, Restrictions, Capabilities

The second step of the process involves contacting the utility to determine anyrequirements or operational restrictions that have not already been ascertained by the

customer. Some utilities have fairly specific interconnection guidelines while others havevery general ones or none at all. At this point, the published utility guidelines should beobtained. Actual requirements for the specific installation will have to be negotiated withthe utility.

Complete the following checklist by checking or entering data after meeting with theappropriate responsible utility engineering and sales personnel.


I. Utility Capacity (for each service)

1. Primary distribution voltage kV

2. Secondary service voltage kV

3. Service transformer rating kVA

4. Service transformer impedance %

5. Utility short circuit capacity MVA

6. Utility phase sequence

II. Requirements and Restrictions (for each service)

1. Service subject to:

Reclosing Yes No

Recloser timing

2. Utility/user point of connection grounding considerations:

Solidly grounded?

Resistance/reactive grounded?

Ungrounded?

3. Visible disconnect required? Yes No


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4. Required utility revenue metering:Yes No

a. Utility revenue metering

1) Import

2) Export

b. Generator revenue metering

c. Initiated financial feasibility studies

5. Required synchronizing controls:

Automatic Manual

Synchronizing Check Relay

6. Are power factor correction capacitors required for induction generatorinstallations?

Yes No N/A

7. Utility protective relay requirements at utility connection:

Utility grade required? Yes No

Check where applicable:

27 Undervoltage, primary secondary

59 Overvoltage, primary secondary

81 O Over frequency

81 U Under frequency

50/51 Overcurrent

50/51G Ground overcurrent

32 Reverse power

67 Directional overcurrent

47 Negative sequence voltage

Other


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Names of protective relay manufacturers and types acceptable to utility

8. Type of overcurrent protection on service feeder primary:

Yes No Ampacity

Fuses

Circuit breaker

Electrically operated

Drawout

9. Is any interlocking required? Yes No

If yes, describe:

10. On-site generation will be paralleled to which utility line?


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STEP 3: Identify Engine Generator Requirements

Complete the following checklist describing the on-site power generation system.Choose the elements of the one-line diagrams provided in the Appendix that best meetthe protection and control requirements determined in Steps 1-3, modifying as needed.

Add any other desired functions including all of the on-site loads to be powered by theon-site generation.


1. List generator data for number and size needed for existing, proposed, or futureinstallation.

Number Size Total

a. Existing kW kW

b. Proposed kW kW

c. Future kW kW

2. Generator type Synchronous Induction

3. Generator impedances

4. Operating voltage volts phase

5. Operating frequency Hz

6. Is generator neutral grounded? Yes No

If yes, what type? Solid Resistive Reactive

7. Type of generator grounding? Individual Common


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8. Generator protective relays required (check where applicable):

32 Reverse power(always recommended for generators operated in parallel)

40 Field loss

87G Generator differential

46 Negative sequence

47 Three-phase undervoltagephase sequence relay

27 Undervoltage relay

59 Overvoltage relay

81 Frequency relay

51V Voltage restrained

overcurrent

51G Ground overcurrent

Other

9. Prime mover data:

a. Type: Reciprocating engine Turbine Other

b. Fuel: Natural gas Diesel Other

10. Required protective device interruption capacity as determined by a

short-circuit study

11. Automatic transfer and loading control:

Yes No

a. Import/export control

b. Ramp loading control

c. Power factor VAR control


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STEP 4: Preparing Utility Interconnect Proposal

The utility interconnect proposals should include a System Description of

Installation, One-Line Diagram, and Bill of Materials, as discussed below. Some utilitiesmay require additional detail on protective relays and the on-site generator.

Reference material to Step 4 can be found in the Appendix to Step 4.

System Description of Installation

Provide a system description of installation. The description should include thelocation of the facility, type of facility, a description of the major equipment, and allproposed operating modes.

NOTE: A system consideration should include an examination of harmonic currents from loads andsources. See A3-1.2 in Appendix to Step 3.

Configure One-Line Diagram

A complete one-line diagram, in conjunction with a physical plan of the installation,should represent sufficient detail to plan and evaluate the electrical power system.Symbols commonly used in one-line diagrams are defined in IEEE 315, GraphicSymbols for Electrical and Electronic diagrams (ANSI Y32.2).

Choose the elements of the one-line diagrams provided in the Appendix that best

meets the protection and control requirements determined in Steps 1-3, modifying asneeded. Add any other desired functions including all of the on-site loads to be poweredby the on-site generation.

The following items should be shown on the one-line diagram:

1. All power sources, including power rating, voltage rating, and short circuit currentcapability

2. Size, type, ampacity, and number of all circuit conductors

3. Capacities, voltages, impedances, connections, and grounding methods oftransformers

4. Identification and quantity of protective devices

5. Instrument transformer ratios and connections

6. Type and location of surge arresters and capacitors

7. Identification of all loads

8. Proposed future additions


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Bill of Materials

Provide a complete Bill of Materials for the paralleling switchgear. The Bill ofMaterials should include numbers and types of protective devices; numbers and typesof interrupting devices; interrupting device interrupting ratings; control, metering, and

relaying transformers; meters; indicating lamps, etc.In some cases, the utility may require more detailed descriptions of protective

relays, including manufacturer and trip settings. The utility may require more detail onthe generator, including reactances and time constants in order to conduct short-circuitstudies.

Refer to Appendix 4 for an example of a utility interconnect proposal.


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Guide to Preparing a Design Proposal for Page 19Paralleling Customer Generation With an Electric Utility Appendix to Step 1


SECTION 3

APPENDICES TO STEPS ONE FOUR


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Page 20 Guide to Preparing a Design Proposal forAppendix to Step 1 Paralleling Customer Generation With an Electric Utility



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APPENDIX TO STEP 1: Identification of Customer Needs

A1-1 Importing Power/Exporting Power

In most commercial facilities, the on-site generators will be used to supplement the

power furnished by the utility company. Typically, the on-site generator capacity is notas large as the total building load and with the machines running at full load, it is stillnecessary to import power from the utility company.

Figure 1 shows a building electrical demand curve. The load on this facility has apeak of 5000 KW at about 3:00 P.M. During the off-peak hours, the load drops to 1200KW. This is considered the base load.

Figure 2 shows a 1000 KW generator paralleled to the utility. The machine is drivento the desired KW output by generator loading controls or import/export controls. Thesecontrols work in conjunction with the engine governor. Because the building base loadexceeds the output rating of the generator, there is never a chance that power will beexported to the utility from the facility.

Exporting power changes considerably the utility company's position toward theinstallation. The utility company may or may not (probably the latter) want to purchaseexcess power. Usually the protection requirements for an export-type installation willincrease as compared to an installation where the generated power never exceeds thebuilding demand.

poly

12 AM 6 AM 12 PM 6 PM 12 AM

5000

4000

3000

2000

1000

Load Profile

Demand Charge (kW)

Figure 1

Building Electrical Demand Curve


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52

52

Generator1000 kW

1000 kW

4000 kW

Utility

Load5000 kW

Figure 2

Diagram of 1000 kW Generator Parallel to the Utility

A1-2 Installation of Generator with Capacity Greater than Baseload,Not Designed or Intended to Export Power

When generator capacity is greater than baseload and no power is intended to beexported, an import/export control is required. Import/export controls require PTs andCTs on the incoming utility feed to monitor utility power levels.

A1-3 Momentary vs. Sustained Parallel Operation with Utility

Some applications require a "no-break transfer" between the utility source and theon-site generator source. This "make-before-break" operation requires that the twosources be synchronized before they are connected (paralleled). The closing of theparalleling contacts signals the immediate opening of the opposite source allowing the

two sources to be paralleled for only a brief period of time (typically 100 milliseconds).This momentary paralleling control circuit will require some type of "fail safe" circuitry toinitiate source disconnect if the paralleling operation is inadvertently extended. Mostutility companies will allow this type of operation without requiring additional protectiverelaying.

Any application requiring the sources to be paralleled more than a fraction of asecond is referred to as Sustained Paralleling. Cogeneration and peakshaving/curtailment applications requiring that the utility and generator source be


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paralleled for long periods of time fall into this sustained category. Also in this categoryare the ramping systems mentioned below. All of these systems require carefulcoordination with the utility company to determine the protective relay requirements.

A1-4 Ramp (or Soft Loading) vs. Immediate LoadingLoading or unloading the generator can be done gradually (ramped) or immediately.

Ramping the load minimizes voltage and frequency disturbances on the system.

Ramping is done by controlling the governors in a fashion that causes the fuelsetting to be increased or decreased gradually over some period of timetypically inthe range of 10 to 60 seconds. Figure 3 shows the 1000 KW load being ramped over aperiod of 30 seconds.

Immediate loading occurs when a source is disconnected without first havingramped the load to the oncoming source.

Figure 31000 kW Load Being Ramped over 30 Second Period

A1-5 Peak Shaving vs. Curtailment

Peak shaving usually refers to the process of lowering the peak (maximum) on thefacility electrical load demand curve. This can be accomplished by either shedding loadscompletely, or by supplying power with the on-site generators during peak loading timeof the day. The financial incentive is a reduction in the facility's monthly utility demandcharge.

Curtailment refers to a program set up by the utility company. The utility companyoffers a premium to the facility for assistance in reducing the utility company's peak load

Time in Seconds

1000

500

kW

10 20 30


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demand on their system. Typically, the contract between the utility company and thefacility owner states that the utility will pay a fixed sum to the facility. In return, the facilityagrees to shed or generate some specified amount of load up to a specified number oftimes per year, upon receipt of notification from the utility.

A1-6 Financial Consideration

Peak shaving reduces the facility peak electrical demand and thereby reduces thepeak demand charge from the utility company. The savings might typically be in therange of $5 to $15 per kilowatt of demand reduction. Actual savings will be negotiatedwith the utility. The costs incurred would be primarily the fuel burned. In analyzing theattractiveness of this decision to peak shave, it is necessary to compare the operatingcosts of the generators to the savings in demand charges. The attractiveness of usingon-site generators to shave facility electrical peaks will be inversely proportional to thenumber of hours a day the generators must operate. A facility with a wide peak or aconstant peak is not a good candidate for peak shaving alone due to the high operating

costs.

Cogeneration, on the other hand, provides a fuel savings to the facility by utilizingthe waste heat. This fuel saving gained by operating the on-site generators increaseswith an increase in the number of hours of use. Essentially, the cogeneration unit"earns" a fixed dollar amount per hour after making an adjustment for the increasedmaintenance costs. Therefore, the more hours the unit runs with the waste heat beingutilized, the greater are the economic benefits. The attractiveness of a cogenerationproject requires an analysis of the payback period for the capitol expended versus thepotential earnings. Good cogeneration candidates have concurrent heat and electricaldemands that are fairly constant.

Cogeneration systems will inherently provide a savings in electrical demand chargeswhich can be added to the earnings from fuel savings.


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APPENDIX TO STEP 2: Identify Utility Requirements, Restrictions,Capabilities

A2-1 Typical Utility Information Required

A typical published utility guideline will include:

1. Utility operating objectives

2. Location of your installation in the system

3. Secondary distribution circuits

4. User circuit configurations

5. Primary circuit configurations

6. Responsibility of costs associated with interconnection and line extension/lineupgrade considerations

7. One-line diagrams of typical installations

8. A listing of the design and operating guidelines

The above items typically must be applied to cogeneration and small powerproducing sources in order to meet the criteria to qualify for integration into the utilitysystem. It must be recognized that certain utility design and operating guidelines will beextremely detailed and complete, others will be less defined, and some will benonexistent in a document form. It remains the responsibility of the system designer toobtain the utility requirements, in formal written form, before proceeding with the design

and proposal of the system.

A2-2 Utility Operating Objectives

1. Minimize hazards to personnel and public.

2. Minimize the probability of damage to utility and other customer equipment.

3. Not adversely affect the quality of service to other customers.

4. Not assume responsibility for protection of the user's generators or electricalequipment.

With respect to the utility protection objectives, it is necessary to disconnect theparallel generator when trouble occurs. This is to ensure:

1. If a fault on the utility system occurs, the fault current supplied by the user'sgenerator is interrupted.

2. The possibility of reclosing into an out-of-phase isolated system composed ofthe utility compound of the utility distribution system and the user's generator isprevented.


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3. Reclosing into the user's generation system which may be out ofsynchronization or stalled is prevented.

Automatic reclosing out-of-phase with the customer's generator may cause damageto user's equipment. It is typically the responsibility of the user for the protection of his

equipment from automatic reclosing. Time of reclosure must be determined.Certain devices (relays, circuit breakers, disconnect switches, etc.) required by the

utility must be installed and placed into service before allowing parallel operation of thegeneration facilities with the utility power.

A2-3 Secondary Distribution Circuits

This is the part of the system through which the power finally reaches the majority ofutility customers. Most customers will be fed from a radial system. However, somesecondary distribution systems are interconnected to form a network to assure greaterreliability.

A2-4 Location of Your Installation in the System

The utility should be able to furnish the following data:

1. Supply voltage or voltages available

2. Point of delivery and line route

3. Billing rate or rates available

4. Options available on ownership of supply transformers

5. Space requirements for the distribution substation by the utility

6. Space required for the distribution transformer if plant is supplied at utilizationvoltage

7. Short-circuit duty at the point of delivery and system characteristics

8. Requirements for metering

9. Type of grounding on the supply system

10. Requirements for relay coordination with the utility protection system

11. Performance data on reliability of supply, as necessary

12. Amount of user generation to total utility load on feeder line

13. Size of site generation to total utility load on feeder line

A2-5 User Circuit Configurations

Cogenerators will generally either be connected directly into the utility primarydistribution circuit or into the distribution secondary circuit at low voltage (120 to 480volts). This is based on the assumed small on-site cogenerators, where the capacity of


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the generator will generally not exceed approximately twice the nominal on-siteelectrical load. Loads of this magnitude are generally required to be three phase by theutility.

A2-6 Primary Circuit ConfigurationsThe choice of location for the generator will be limited by the utility circuit available

for interconnection. In addition to the wide range of generators and distribution lines,consideration must be given to the other customers on the feeder, the types of loads,the distance from a substation, the reclosing practice, the alternate supply source, thesectionalizing devices, etc.

A2-7 Responsibility of Costs Associated with Interconnection and

Line Extension/Line Upgrade Considerations

1. The installation and maintenance costs of facilities related to the interconnection

of a customer's facility (interconnection facilities) to the utility's system, utilizingthe utility's normal standards, is typically borne by the customer.

2. The installation and maintenance costs of any line extension/line upgradefacilities, utilizing the utility's normal standards, typically are borne by thecustomer. Line extension/line upgrade facilities are defined as all facilities,exclusive of interconnection facilities, determined by the utility to be necessaryto connect the utility's system to the customer's point of delivery in order toaccept the output of the customer's generating facility. The cost of any portionof the line extension/line upgrade undertaken to serve future additionalcustomers is typically borne by the utility.

3. The customer is typically responsible for the costs of exploring the feasibility ofa project or its interconnection with the utility's system.

4. The customer is typically responsible for costs of metering, telemetering, andsafety checks.

A28 One-Line Diagrams of Typical Installations

See Figures 410 for One-Line Diagrams of typical installations.


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Figure 4

One-line Diagram:Multiple Generators Synchronous Non-Standby, Low Voltage


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Figure 5

One-Line Diagram:

Multiple Generators (Minimal System) Synchronous Non-Standby, Low Voltage


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Figure 6

One-Line Diagram:

Paralleling Utility With Recloser


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Figure 7

One-Line Diagram:

Single Generator Set Synchronous Non-Standby


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Figure 8

One-Line Diagram:

Synchronous Non-Standby, Medium Voltage


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Figure 9

One-Line Diagram:

Low Voltage Black Box-Generator Control & Protection


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Figure 10

One-Line Diagram:

High-Resistance Grounding Scheme

Using Overvoltage Relays For Activation Of Alarms


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A2-9 Summary of Considerations

1. Customer system description

2. Proposed metering device consideration

3. Proposed protective relaying consideration to provide adequateprotection for (but not limited to):

a. Faults on the customer system

b. Faults on the utility system

c. Unbalanced or single-phase conditions on the utility system

d. Backfeed of the customer(s) generator(s) into a dead utility bus

4. Typical protective devices required include (but not limited to):

a. Individual phase overcurrent trip devices

b. Undervoltage trip devices

c. Sensitive current unbalanced relays

d. Synchronizing controls (either automatic or manual)

e. Over/under frequency trip devices

5. Disconnection

a. A means of disconnection will typically be required on both sides of theutility metering and may be under the control of the utility.

b. The utility typically will have discretionary control over the utility tie-breaker

during periods of parallel operation, outages, equipment maintenance, oremergencies.


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APPENDIX TO STEP 3: Identify Engine Generator Requirements

A3-1 Type of Generators

A3-1.1 Two Types of Generators

Two types of electric generators are used for in-plant generating systems: theinduction generator and the synchronous generator. There is a vast difference in thedegree of control available from these two machines.

The induction generator is the very simplest form of electric generating machine andis used extensively for small cogeneration systems and small power systems. It consistsof a conventional induction motor, which is connected to the utility network and drivenabove its synchronous speed by a prime mover. The more mechanical power that isapplied to the induction generator's shaft, the more kilowatts are fed into the utilitynetwork.

NOTE: The induction generator works only when connected to an energized network. Theinduction generator draws VARs from the network for its own energization. Therefore, once theinduction generator is disconnected from the live network, it ceases to generate power.

The synchronous generator is used in all large generating systems and in anysystem where precise control of the electric output is essential. This machine containstwo separate sets of windings: the three-phase windings in the stator, where the electricpower is generated, and the field windings in the rotor. Precise control of the DC fieldcurrents in the rotor provides the user with complete control over the output of thesynchronous generator.

A3-1.2 Harmonics

Harmonics are integral multiples of the fundamental frequency and are caused bydevices which change the shape of the normal sine wave of voltage or currentsynchronism with the 60 hertz (50 hertz) supply. The harmonic content and magnitudeexisting in any power system is largely unpredictable and effects will vary widely."Harmonic" currents circulating within a power circuit reduce the capacity of the current-carrying equipment and increase losses without providing any useful work. Duringpreliminary meetings with the supplying utility, the anticipated harmonics analysis of thepower supply should be determined (this information coupled with that provided by themanufacturer of any equipment to be installed that generate a voltage distortion that canbe used to govern the specifications or the application of other equipment that may be

exposed to the harmonic voltage condition).Generators that were not specifically manufactured as identical units for parallel

operation by the same manufacturer are to be operated in parallel. The possibility ofexcessive circulating harmonic currents must be considered. In fact, circulatingharmonics currents, usually negligible, flow between so-called identical machinesbecause of minor manufacturing differences. Whenever one or more generators are tobe operated in parallel with the utility power source, the same circumstances exist.


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Circulating harmonic current can destroy a generator or require considerable cost intime and money to eliminate at the jobsite and yet the problem is not widely recognized.The problem is usually described as excessive third harmonic because third is usuallythe predominant harmonic generated and the popular neutral connected wye generatoris particularly susceptible to third harmonic current.

The generators must be rated for the design frequency. The generator voltagerating can be modified by an output transformer, if necessary. The compatibility ofdifferent generators with respect to differences in electrical characteristics, reactances,and harmonic content of the output voltage wave form should be examined to insurethat excessive circulating current will not flow between paralleled generators. Excessivecirculating currents can result in reduced capacity, overheating, and possible damage,and can also cause nuisance tripping of some forms of protective relaying. Allsynchronous generators are a source of harmonics. In a symmetrical three-phase ACgenerator, even numbered harmonics are not produced, but odd numbered harmonicsof a magnitude dictated by the design of the machine are evident. The 120-degree

phase relationship of a three-phase generator causes the triple series harmonics (3rd,9th, 15th, etc.) to differ from the other harmonics in that they are limited by the zero se-quence reactance of the generator and they do not cancel in the neutral connection.Other harmonics, like the fundamental frequency, cancel to zero in the neutral connec-tion and are limited by the negative sequence reactance. Negative sequence reactanceis typically larger than zero sequence reactance.

A3-1.3 Voltage Regulators

A voltage regulator ordinarily senses the generator voltage at the generatorterminals and automatically adjusts the excitation level to hold the voltage at a presetlevel. If operated in parallel with other generators, cross-current compensation is utilized

to prevent uneven reactive load division. When operating in parallel with utility,variations in utility bus voltage can cause swings in the power factor with resultantgenerator overloading or pulling out of synchronism. To eliminate this possibility, aVAR/Power Factor Controller is used in conjunction with the voltage regulator.

A3-2 System Voltage Classes

Low Voltage: A class of nominal system voltage less than 600 volts

Medium Voltage: A class of nominal system voltage equal to or greater than1000 volts and less than 15,000 volts

A3-3 Ground Fault Protection

A3-3.1 General

The majority of electrical faults involve ground.


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The ground-fault protective sensitivity can be relatively independent of continuousload current values and thereby have lower pick-up settings than phase protectivedevices.

Arcing ground faults that are not promptly detected and cleared can be extremely

destructive, however the opening of some circuits in critical applications may in itselfendanger life or property, e.g. fire-pump controls or critical hospital loads.

Refer to the National Electrical Code, NFPA 70, and local codes for Ground FaultProtection requirements.

A3-3.2 Method of Neutral Grounding

In grounding the neutral of a power system, the advantages outlined will beachieved provided attention is given to the impedance of the circuits from systemneutral to ground. This circuit is illustrated in Figure 11 for the commonly usedgrounding methods. These methods are referred to as "solid grounding," and "reactance

grounding." Note that each method is named in accordance with the nature of theexternal circuit from system neutral to ground. In each case, the impedance of thegenerator or transformer, whose neutral is grounded, is in series with the externalcircuit.

Characteristics of the various methods of system neutral grounding are given in thefollowing text and summarized in the table below in A3-3.3. Application limits and guidesfor the various methods are outlined with reference to the following:

1. Effect on development of transient overvoltages

2. Damage at the point of fault due to magnitude of ground-fault current

3. Application of standard relays and circuit interrupting devices for selectiveground-fault tripping

A power system is solidly grounded when a generator, power transformer, orgrounding transformer neutral is connected directly to the station ground or to the earthas shown in Figure 11. Because of the reactance of the grounded generator ortransformer in series with the neutral circuit, solid grounding cannot be considered azero impedance circuit.

For most solidly grounded systems and reactance grounded systems, it isnecessary for ground-fault current to be in the range of 25 to 100% of the three-phasefault current to prevent development of high transient overvoltages.


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(a) UngroundedWithout intentional connection to ground except through

potential indicating or measuring devices.

(b) Solidly Grounded (Directly Grounded)Grounded through an adequate ground connection in which

no impedance has been inserted intentionally.

(c) Resistance GroundedGrounded through impedance, the principal element of

which is resistance.

(d) Reactance GroundedGrounded through impedance, the principal element of

which is reactance.

(e) Ground-Fault NeutralizerGrounding device which provides an inductive component of

current in a ground fault that is substantially equal to, andtherefore neutralizes, the rated frequency capacitive

component of the ground.

XG = Reactance of Generator orTransformer Used for Grounding

XN = Reactance of Grounding ReactorRN = Resistance of Grounding Resistor

Figure 11

System Neutral Circuits and Methods of Grounding


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A3-3.3 System Characteristics with Various Ground Methods

Table 1

Ungrounded

Solid

Grounding Reactance Grounding Resistance Grounding

Low

ReactanceValue

High Reactance

Value Low Resistance

High

Resistance

Current forPhase-to-

ground fault

(Percent of 3-phase fault

current)

Less than 1%Varies,

may be 100%or greater

Usuallydesigned to

produce25% - 100%

5% - 25% 20%,

minimum 400 A*

Less than 1%

Transient

overvoltages

Very High Not excessive Not Excessive Very High Not Excessive NotExcessive

Automatic

Segregation ofFaulty Zone

No Yes Yes Yes Yes Yes

Remarks

Notrecommended

due toovervoltage andnon-segregation

of fault

Generally used on systems:600 volts or below, and

over 15 kV

Not Used due toexcessive

overvoltages

Generally used onindustrial systemsof 2.4 kV to 15 kV

Used whencharacteristic

s of othermethods areundesirable,

or whendesired by

user

*Lower limit for general power systems using ground-sensor relaying

A3-4 Paralleling System Protection

Protection of an electric system is a form of insurance. It pays nothing as long asthere is no fault or other emergency, but when a fault occurs, the protective devices canbe credited with reducing the extent and duration of the interruption, and the hazards ofproperty damage and personnel injury.

The power system protective devices provide the intelligence and initiate the actionwhich enables circuit switching equipment to respond to abnormal or dangerous systemconditions.

Protection of a system with paralleled sources is unique in the fact that the powersystem must be protected in a way satisfactory to two parties (the utility and the facilityowner) which may have conflicting requirements or philosophies. The design of theprotective system may therefore be a result of negotiations between engineersrepresenting both parties.

A basic premise in designing the protective relaying scheme is that the two powersystems must be separated immediately upon detecting a fault in either system. Once


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separated, the protective devices in each isolated system can act to clear the fault orremedy the malfunction accordingly.

There is no single protective relaying scheme which fits all applications or fulfills allphilosophies. The devices listed below are representative of those required in a typical

system.

Synchronizing or Synch Check Device (Device 25)

A device that operates when two AC sources are within the desired limits offrequency, phase angle, and voltage to permit or to cause the paralleling of the twosources.

Undervoltage Relay, Device 27

A relay that functions on a given value of undervoltage.

Directional Power Relay, Device 32

A device that functions on a given value of power flow in a given direction.

Loss of Field Relay, Device 40

A device that functions on a loss of generator field current.

Reverse-phase or Phase Balance Current Relay, Device 46

A relay that functions when the polyphase currents are of unbalanced or containnegative phase sequence components above a given amount.

Phase-sequence Voltage Relay, Device 47

A relay that functions upon a predetermined value of polyphase voltage in thedesired phase sequence.

Temperature Relay, Device 49

A relay that functions on excess generator temperature.

Overcurrent Relays, Devices 50-51

Relays provided to back up the directional overcurrent relay or to provide faultprotection in medium voltage systems.

Overvoltage Relay, Device 59

A relay that functions on a given value of overvoltage.

Directional Overcurrent Relays, Device 67

Relays provided to prevent back feeding a failed utility; function on a given value ofAC overcurrent flowing in a predetermined direction.


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Frequency Relay, Device 81

A relay that functions on a predetermined value of frequency (either under or overnormal system frequency) or rate of change of frequency.

Differential Relays, Device 87

Relays provided to detect faults in a given zone. When used to detect faults thatmay occur in transformers, Device 87T, a percentage differential relay, includingharmonic restraint, should be used to prevent false tripping due to magnetizing currentinrush.

A3-5 Prime Mover

A3-5.1 Types of Prime Movers

Prime movers for on-site power can be steam, gas, wind, hydro-turbines, or gas ordiesel internal combustion engines. The important considerations for prime movers are

reliability, efficiency, fuel cost and availability, and exhaust emissions.

1. Gas Turbines

The gas turbine is a popular prime mover in intermediate size installations. Heatrecovery is simple because all waste heat is in the exhaust at a convenient temperature.Gas turbines have flexibility in that they are able to quickly change to liquid petroleumfuels in an emergency. Gas turbines are reliable, long-lived, and require littlemaintenance.

2. Gas Engines

Many smaller cogeneration systems and peaking systems use internal combustion

natural gas engines. Gas engines are reliable and have long life. Heat recovery requirescollecting waste heat from both coolant and exhaust. Gas fuel without an alternate on-site supply is usually not acceptable for emergency or standby use.

There is increasing interest in digester gas or biogas as a fuel for on-site power.Digester gas consists principally of a mixture of methane (the principal component ofnatural gas) and carbon dioxide (CO2). With carburetor modifications and good filtering,gas engines run very well on this fuel. Because the supply of methane is frequentlyuncertain, many applications provide for natural gas standby fuel.

Properly functioning gas engines have a low level of hydrocarbons in the exhaust.However, the high combustion temperature can contribute to formation of oxides ofnitrogen (NOx).

3. Diesel Engines

Diesel engines are efficient fuel users. They have wide applications in emergencystandby, peaking power, and cogeneration applications. Because of relative fuel costsat the present time, diesel engines are more expensive to operate than gas engines.Maintenance and reliability are similar to gas engines. Diesel engines have a lower


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National Electrical Manufacturers Association. It is illegal to resell or modify this publication. National Electrical Manufacturers Association. It is illegal to resell or modify this publication.

initial cost than other types of prime movers due to their high production rates and thegreat number of competitive models available. A number of suppliers offer completelines of commercial diesel generator sets for all applications.

4. Hydro Turbines

Excellent hydro turbines of several types are readily available. The main drawbackof hydro turbines is the high cost of the installation.

5. Wind Turbines

Reliable wind turbines of a few hundred watts output have been built in this countryfor more than 50 years. Attempts to increase the output to present day acceptableratings of 3 to 15 kilowatt have proven to be difficult.

6. Steam Turbines

Most large industrial on-site power systems use steam turbines. These installationsresemble utility power stations. They have the advantage of increased efficiency by useof exhaust heat for industrial processes and having no transmission losses.

A3-5.2 Governing

The governing of all types of prime movers for generators has reached a high levelof development. Electronic controls with either hydraulic or electrical services canperform almost any conceivable function.

1. Droop Governor

A governor controls the fuel setting of the prime mover. The simplest form ofgovernor is a droop governor. The governor sets the no load speed or frequency (Hz) at

some figure above the rated load speed. Five percent droop is a common figure. Whenoperating alone, such a governor will produce rated frequency at rated load only. At lessthan rated load it will produce something higher. For parallel operation with a utility,such a generator set will assume full rated load. It will stay at that fixed outputregardless of load variations of the facility. Some peaking systems use this speedcontrol method.

2. Isochronous Governor

Most applications require rated frequency operation under any operating condition.Governors that perform that function are called isochronous. The fuel setting of theprime mover then becomes a function of the load, not the speed. This is the type

governor used on such applications. Many such governors have a switch to allow themto also operate in the droop mode.

3. Paralleling Considerations

When utilized with an engine generator operating in parallel with the utility, thegovernor assumes the role of a load controller. When operating as an isolated system,generator set frequency is controlled by the governor and the load is independent of anyaction taken by the governor. However, when paralleled with an infinite source such as


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a utility bus, the line frequency is dictated solely by the utility, while the governor is usedto control the load.

The precision speed governor for each prime mover must be equipped with loadsharing feature, preferably one which monitors generated watts and provides a

corrective signal to a governor input that is common to all units.

Existing governors will usually require the addition of a load-sharing module, soconsideration should be given to using identical units, especially if different manufac-turers are involved. When different units are used, field tests and modifications to matchresponse is sometimes required.

A3-6 Available Short-Circuit Currents

A3-6.1 Short-Circuit Current Calculations

Short-circuit currents introduce large amounts of destructive energy in the forms of

heat and magnetic force into a power system. Calculations should be made to ensurethat the short-circuit ratings of the equipment are adequate to handle the currentsavailable to their locations. In general, the procedure is to (1) develop a graphicalrepresentation of the systems with symbolic voltage sources and circuit impedances, (2)determine the total equivalent impedance from the source to designated points, and (3)at each point divide the voltage by the total impedance to that point to derive the short-circuit current.

A3-6.2 Sources of Fault Current

The basic sources of fault current are the power company system, generators,synchronous motors, and induction motors. The current from each source is limited by

the impedance of the machine and the impedance between the machine and the fault.

A3-7 Protective Switching Devices

1. Circuit breakers (low voltage circuit breakers and medium voltage circuitbreakers)

2. Fused switch (not to be used as a paralleling device)

3. Fuse/breaker combination

4. The role of reclosers

Automatic reclosing out-of-phase with the customer's generator may cause damageto user's equipment. Automatic reclosing by utility shall be coordinated to ensureautomatic customer separation prior to circuit reenergization. It is the responsibility ofthe user to ensure the protection of his equipment from automatic reclosing of the utility.


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A3-8 Kilowatt Load Control

A3-8.1 Soft (Ramp) Loading

Kilowatt load control is designed for use in small power plants having cogeneration,peak shaving, peak loading, or emergency power applications. This type of control isbeneficial when the plant system is isolated during part of the time and the rest of thetime it parallels the utility bus. When such a system does join the utility, this type ofcontrol enables a soft loading to (or from) the utility by controlling the power of the localplant during the time the on-site generator is paralleled with the utility. Under theseconditions, the power transferred across the tie breaker can be controlled to near zeroduring both the period before closing and the period before opening the tie breaker.

A3-8.2 Import or Export Control

A control system is required to regulate electricity imported from or exported to autility.

Controls will sense the desired import or export power reference signal set by theuser. The control will send appropriate biasing signals to the electronic governingcontrol through load-sharing lines. The governing control will adjust the prime mover'spower output in order to meet import or export requirements.

The power level reference is set by:

1. A standard potentiometer for manual reference settings

2. A motor operated potentiometer for remote adjustments

3. A transducer to interface with automatic equipment and provide usable signalsfor the import/export control.

A3-9 VAR/Power Factor Control

The power factor is defined as the ratio of real power to apparent power in a circuit.It varies from one to zero, but is generally given in percent. The power factor may beleading or lagging, depending on the direction of both the real and reactive power flows.When the reactive power component in a circuit is reduced, the total current is reduced.If the real power component does not change, as is usually true, the power factor willimprove. When the reactive power component becomes zero, the power factor will beunity or 100 percent. The VARs or the Power Factor need to be controlled whenparalleled with the utility, due to fluctuating utility voltage.


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APPENDIX TO STEP 4: Preparing Utility Interconnect Proposal

The Proposal

This guide provides guidelines to prepare a proposal for cogeneration switchgearmanufactured for a utility paralleling application. There are other standards and localcodes available that may have to be complied with for such an application. A welldesigned system will follow these guidelines and standards/codes in the selection ofmaterial and equipment.

Documentation to be included in the proposal shall include, but not be limited to, thefollowing items:

1. System description, operating sequence, scope of work

2. System one-line diagram

3. Bill of Material, including equipment type and ratings

A4-1 System Description of Installation

The description should include the location of the facility, type of facility, adescription of the major equipment and all proposed operating modes.

NOTE: The components of paralleling switchgear consist of the generator and interconnectionswitchgear. The installation of the system should not begin until the utility has approved the design.The design must comply with all applicable local codes.

A4-2 One-Line Diagram

A complete one-line or single-line diagram are defined in IEEE Standard 315,Graphic Symbols for Electrical and Electronics Diagrams (ANSI Y32-2).

The following items should be shown on any one-line diagram:

1. Power sources, including voltages and available short-circuit sources

2. Size, type, ampacity, and number of all conductors

3. Capacities, voltages, impedance, connections, and grounding methods oftransformers

4. Identification and quantity of protective devices (relays, fuses, and circuitbreakers)

5. Instrument transformer ratio and connections

6. Type and location of surge arresters and capacitors

7. Identification of all loads

8. Identification of other distribution system equipment

9. Proposed future additions


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The actual drawing should be kept as simple as possible. It is a schematic diagramand need not show geographical relationship.

A4-3 Bill of Material

The proposed Bill of Material should be based on specification to include groups,quantity, and manufacturer catalog numbers, brief descriptions and ratings, etc.

Where materials, equipment, apparatus, or other products are specified bymanufacturer by brand name and type of catalog number, such designation is toestablish standards of desired quality and style and shall be the basis of the bidproposed.

The specific relays and related equipment proposed to meet the functionalrequirements specified on the specifications should include name of manufacturers'model number, ratings, etc.


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Guide to Preparing a Design Proposal for Page 49Paralleling Customer Generation With an Electric Utility Section 4 Example


SECTION 4

EXAMPLE


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Page 50 Guide to Preparing a Design Proposal forSection 4 Example Paralleling Customer Generation With an Electric Utility



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EXAMPLE CHECKLIST AND PROPOSAL

The following is an example of a proposed system based on the following exampleworksheets for Steps 1-3.

This example is a demonstration of how to use the guide and should not be used forany other purpose. The example should not be considered a recommendation ofany particular system configuration.

Example Checklist

STEP 1: Identification of Customer Needs Example

I. System Identification

1. Will system (check one of three below):

a. Import power only X

b. Export power only _________

c. Import/export power _________

2. Identify source of primary power (check one):

a. On site generator set _________

b. Utility X

3. Identify type of user system (check one of the three situations below):

a. Momentary parallel operationwith utility (milliseconds)for block or immediate loading. _________

b. Short time parallel operation (seconds)for ramp loading. _________

c. Long-time parallel operation (hours)with utility. X

4. Will the generator set be used for standby? Yes X No ______


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II. System Power Capacities (enter data)

1. Describe proposed capacity

a. Facility peak demand 5200 kW 5800 kVA

b. Facility average load 4000 kW 4500 kVAc. Facility minimum load 1200 kW 1500 kVA

d. Emergency/standby load 3000 kW 3400 kVA

e. Proposed installed generation 5000 kW 6250 kVA

2. Describe potential future power capacity:

Is there potential for future expansion of on-site power requirements?

Yes No X

If Yes:

a. Future average load kW kVA

b. Future expansion generation kW kVA

III. Identify Nature of Contacts Between Customer and Utility to DateRegarding the Proposal

The user has (check appropriate box): Yes No

a. Established appropriate

utility contacts X

b. Obtained rate structures and

explored utility incentive programs X

c. Initiated financial feasibility studies X

d. Obtained utilityinterconnection guide-lines X


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STEP 2: Identify Utility Requirements, Restrictions, Capabilities Example

The following is an example worksheet for Step 2 of the process to Identify UtilityRequirements, Restrictions and Capabilities of the examplesystem.

This example is a demonstration of how to use the guide and should not be used forany other purpose. The example should not be considered a recommendation ofany particular system configuration.

I. Utility capacity (for each service)

1. Primary distribution voltage N/A kV

2. Secondary service voltage 4.16 kV

3. Service transformer rating N/A kVA

4. Service transformer impedance N/A %

5. Utility short circuit capacity 250 MVA

6. Utility phase sequence ABC

II. Requirements and Restrictions (for each service)

1. Service subject to:

Reclosing Yes X No

Recloser timing 45 hertz

2. Utility/user point of connection grounding considerations:

Solidly grounded? X

Resistance/reactive grounded?

Ungrounded?

3. Visible disconnect required? Yes X No


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4. Required utility revenue metering:

Yes No

a. Utility revenue metering

1) Import X

2) Export X

b. Generator revenue metering X

c. Initiated financial feasibility studies X

5. Required synchronizing controls:

Automatic X Manual

Synchronizing check relay X6. Are power factor correction capacitors required for induction generator

installations?

Yes No N/A X

7. Utility protective relay requirements at utility connection:

Utility grade required? Yes X No

Check where applicable:

27 Undervoltage, primary secondary X59 Overvoltage, primary _ secondary X

81 O Over frequency X

81 U Under frequency X

50/51 Overcurrent X

50/51G Ground overcurrent X

32 Reverse power X

67 Directional overcurrent

47 Negative sequence voltage X

Other


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Names of protective relay manufacturers and types acceptable to utility

8. Type of overcurrent protection on service feeder primary:

Yes No Ampacity

Fuses

Circuit breaker X 1200

Electrically operated X

Drawout X

9. Is any interlocking required? Yes _______ No X

If yes describe:

10. On-site generation will be paralleled to which utility line?


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STEP 3: Identify Engine Generator Requirements Example

The following is an example worksheet for Step 3 of the process to Identify Engine

Generator Requirements of the examplesystem.This example is a demonstration of how to use the guide and should no

Documents

Guide Preparing Design Proposal