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Massachusetts DTEDG Interconnection Collaborative

DG Cluster ProposalNovember 12, 2002

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What Is An Interconnect (Nomenclature)?

Basically, the interface between Distributed Generation (DG) equipment and the grid, called the Area Electrical Power System (EPS)

Load3

EPS

Customer Facility

Customer Facility

Customer Facility

Customer Facility

Customer Facility

EPS

DGLoad

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Point of Common Coupling (PCC)

Load1Customer

CustomerCustomer

CustomerCustomer

EPS EPS

Network

Radial

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DG Cluster Proposal Overview

Standardized Process and Requirements Ensure safety and reliability

Follows national standards Equipment must be certified or undergoes design review

For small generation <20MW

Differentiating By: One of three generator size thresholds Potential “impact” of generator on Electric Power

System (EPS) Type of EPS at Point Of Common Coupling (PCC)

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Process Overview

Scope of process shrinks considerably when expeditedDefines screens for certified equipment

Generator Application

>20MW?

Historic Application

Process

Interconnect Agreement

>2MW?

Expedited Application

Process Super Expedited

Application Process

Meets Screens?

Yes

Yes

Yes

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Size Threshold CategoriesLess than 10kW

Accepts utility proposal Three page application/agreement No review/payments necessary

Less than 2 MW eligible for super-expedited process

Certified equipment De minimis grid impact No connection to transmission lines

2-20MW eligible for expedited process Check for distribution and transmission impact

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10 kW To 2 MW

Units certified by UL or other NRTL against UL1741 (representing IEEE Std1547 Draft 10)2 screens for determination of no grid impact Primary screen – conservative, utility origin

100% of units that pass are OK Secondary screen - less conservative

80-99% of units are OK?

Creates presumption of acceptance

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CertificationVerifies that equipment is designed to ensure electrical protection safetyWebsite registryUL or similar NRTL describes equipment package and test resultsPosted w/ 6 week comment periodUL responds to any commentsOnce certified -- no type testing and no other equipment can be requiredAlready UL-approved equipment is grandfathered

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IEEE Std1547OverviewReferencesDefinitions and AcronymnsTechnical Specs and Requirements

General Requirements Response to Area EPS Abnormal Conditions Power Quality Islanding

Test Specifications and Requirements Interconnection Test Production Tests Interconnection Installation Evaluation Commissioning Tests Periodic Interconnection Tests

Annexes (Informative)

Flicker Information Interconnection

Tests Commissioning

Tests Bibliography

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Overall Super-ExpeditedProcess Flow

SG Submits Complete

Application

Interconnect Agreement

Passes Primary

Screens?

Yes Yes

IP Conducts Initial

Review

Passes Secondary Screens?

If Needed, IP & SG Agree To Minor Mods?

Yes

Technical Dispute

Resolution

No (IP Initiates)

IP Conducts Limited IC

Review

Meeting To Discuss

Initial Review NoNo

IP Conducts Supplemental Review (If SG

Agrees)

SGInitiates

To Expedited Process

If Needed, IP & SG

Agree To Mods?

Yes

No

Note: “SG” is Small Generator “IP” is Interconnection Provider

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Basis For ScreensCircuit size versus DG

size

DG contribution to fault

Short circuit interrupting capability limit

Three-wire and four-wire circuit criteria

Nameplate limits

Circuit impact

Fault handling, fuse desensitizing & nuisance trip

Short circuit handling

Proper connection

Single phase imbalance

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Screens – PrimaryAggregate DG capacity limited to a low percentage of the peak load of a distribution circuit (different limits for radial vs spot network vs secondary grid network)DG contribution to circuit fault current is limitedDG not allowed to cause grid protective devices to exceed 90% of their short circuit interrupting capabilityIn aggregate, DG cannot be > 10MW where transient stability limits postedInterconnection configuration-specific limits on single-phase generator hookup and capacity to avoid imbalance, overload, and possible neutral/grounding problems

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Screens – SecondaryAggregate DG capacity limited to a higher percentage of the peak load of the distribution circuitBasically the same limits on fault current contribution and short circuit interrupting impact as primary screen

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10kW-2MW Costs

Application feeAdditional surcharge for interconnection review Limited to reasonable amounts based on

size

No other costs for interconnection under Super Expedited procedures

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Dispute Resolution

Elements Technical Master Hotline ADR for non-technical disputes

IP must initiate if SG Applicant clears secondary screenGen Applicant has burden if both screens failed

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Metering

Only metering required for this agreement is that necessary to implement the interconnection

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Timing10 days to review application15 days to review screens5 days to execute IA (Interconnect Agreement)If Primary Screen failed 10 days for additional review (after

surcharge is paid) 5 days to notify applicant of results 5 days to send IA

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Interconnection Agreement

Standard form AgreementShorter form for generators <2MW Can be pre-executed

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Interconnection Application

Standard formShorter Form for generators <2MW

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2-20MW Interconnection

Includes transmission impact issuesDirect transmission interconnection as well as distributionUsed by all generator sizes for which <2MW procedures do not apply

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Basic Process

Optional scoping meeting up frontThree main components Feasibility study Impact study (if needed) Facilities study (if needed)

Patterned after Utility proposal

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Feasibility Study

Checks to see if generator has an impact distribution or transmission system load flow (unless no export) short circuit grounding

IP shall rely to extent practical on existing studiesGives generator developer idea of interconnection costs

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Transmission Impact Study

Only undertaken if Feasibility Study raises questions of transmission impactsUsually costly -- to be avoided if possibleIf no impact study needed - generator drops from queue

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Distribution Impact StudyPurpose

Identify generator design elements that protect distribution system

Assess impact of generator on distribution

No design review needed if Certified Generator meets criteria similar to 0-2MW secondary

screens (without secondary network items)

Includes Distribution load flow study Equipment interrupt rating analysis Protection coordination study System operation impact analysis

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Facilities Study

Identifies attachment facilities needed for interconnection including distribution system upgradesIf no facilities needed (customer sited generation), no study undertaken

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2-20MW Costs

To be discussedLimit interconnection costs to only those directly related to the application

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Transmission Queue

To be discussedFERC is scheduling a conference and possible NOPR on the subject

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Interconnection Agreement/Application

Forms to be developed

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Massachusetts DTEDG Interconnection Collaborative

Background

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IEEE Std 1547 General Requirements Summary

Voltage regulation inside ANSI C84.1 Range AGrounding coordinated with Area EPSSynchronize without voltage fluctuation at PCC >±5% of prevailing voltagesNetworks: Spot networks only for now

CustomerCustomer

CustomerCustomer

Customer

Feeder

NP NP

Feeder

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1547 General Requirements Summary (Continued)

DG shall not energize EPS when EPS is de-energizedDG > 250kVA (unit or aggregate at PCC) shall have provisions for monitoring DG status, real power, reactive powerWhen required by EPS, accessible, lockable, visible-break isolation device (switch) located between DG and EPS

Isolation Switch Suitable for 70kW DG

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1547 Abnormal Conditions Response Summary

Voltages outside of table below shall cause DG to cease to energize within clearing timeDetected at PCC or point of DG connection if:

Aggregate DG capacity <= 30kW Interconnect equipment certified to pass non-islanding test Aggregate DG capacity < 50% total local EPS demand AND

export of power prohibited

Voltage Range (% base voltage) Clearing Time (s)

V < 50 0.16

50 <= V < 88 2.00

110 <V < 120 1.00

V >= 120 0.16

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1547 Abnormal Conditions Response Summary (Continued)

DG <= 30 kW, frequencies shall fall in range of 59.3 to 60.5 Hz else cease to energize within 0.16 secondsDG > 30 kW

cease to energize within 0.16 seconds if >60.5 Hz cease to energize within an adjustable time delay if undervoltage in range of 59.8

to 57 Hz cease to energize within 0.16 seconds if <57.0 Hz

After a disturbance, DG reconnect only if voltage and frequency within rangeInterconnection equipment shall be designed to coordinate with EPS reclosing practices and include ability to delay reconnect up to 5 minutes

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Power Quality Summary

DG connected to single phase distribution shall not inject DC current >0.5% DG full rating“The DG shall not create objectionable flicker for other customers on the area EPS”DG harmonic injection shall not exceed:

Maximum Harmonic Current Distortion (% of current)

Harmonic Order (h)h<11 11<=h<17 17<=h<23 17<=h<23 35<=h

Percent (%) 4.0 2.0 1.5 0.6 0.3

Total Demand Distortion Maximum = 5.0%

Harmonic

Cu

rren

tD

isto

rtio

n

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Testing Requirements Summary

Five kinds of test are defined: Design test – certifies that interconnection

equipment meets the standard requirements Production test – factory test of DG’s conformance to

voltage and frequency variation limits Interconnection installation evaluation – basically a

verification that the DG and interconnection design meet the standard

Commissioning test – conducted at the facility to verify adjustable settings are correct and protective functions are operating properly

Periodic interconnection tests – A periodic test of the interconnect protection system

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Screens – Primary<5% of annual peak load on radial circuits<5% of peak load (or 50kW max) on spot networks (inverters only)Secondary grid distribution networks

induction generator or inverter not exceeding 50% of facility minimum load

<10% contribution to circuit max fault currentNot cause grid protective devices to exceed 90% of their short circuit interrupting capabilityIn aggregate, cannot be >10MW where transient stability limits postedPhase imbalance limits if single-phase and connected to center tap neutral of a 240V service<20kVA if single-phase and on a shared secondary Single-phase connection requirements<10% of line capacity if single phase and section configuration is three-phase, 4-wire or a mix

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Screens – SecondaryRadial circuits: <15% of line section design capacitySpot networks: <5% of peak load on spot networksSecondary grid networks On any network, use reverse power

protection except: if generator <50% of min facility load or

500kW

Basically same limits on fault current contribution and short circuit interrupting impact as primary screen