Transcript DG Cluster Proposal - Massachusetts Distributed Generation

Massachusetts DTE
DG Interconnection Collaborative
DG Cluster Proposal
November 12, 2002
1
What Is An Interconnect
(Nomenclature)?
Basically, the interface between Distributed
Generation (DG) equipment and the grid,
called the Area Electrical Power System (EPS)
Radial
EPS
EPS
Point of Common
Coupling (PCC)
Customer
Facility
Network
EPS
EPS
Customer
Customer
Customer
Customer
Customer
Customer
Customer
Facility
Facility
Customer
Customer
Facility
Facility
DG
Load Load
1
2
Load
3
2
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)
3
Process Overview
Generator
Application
Scope of process
shrinks
considerably when
expedited
Defines screens for
certified equipment
>20MW?
Yes
>2MW?
Yes
Historic
Application
Process
Meets
Screens?
Expedited
Application
Process
Yes
Super
Expedited
Application
Process
Interconnect
Agreement
4
Size Threshold Categories
Less 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
5
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
6
Certification
Verifies that equipment is designed to ensure
electrical protection safety
Website registry
UL or similar NRTL describes equipment package and
test results
Posted w/ 6 week comment period
UL responds to any comments
Once certified -- no type testing and no other
equipment can be required
Already UL-approved equipment is grandfathered
7
IEEE Std1547
Overview
References
Definitions and Acronymns
Technical 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
8
Overall Super-Expedited
Process Flow
SG Submits
Complete
Application
IP Conducts
Initial
Review
To Expedited
Process
IP Conducts
Supplemental
Review (If SG
Agrees)
No
If Needed,
IP & SG
Agree To
Mods?
Meeting To
Discuss
Initial Review
SG
Initiates
Technical
Dispute
Resolution
No
Passes
Secondary
Screens?
Yes
No
Passes
Primary
Screens?
Yes
IP Conducts
Limited IC
Review
Yes
No (IP Initiates)
If Needed, IP &
SG Agree To
Minor Mods?
Yes
Note:
“SG” is Small Generator
“IP” is Interconnection Provider
Interconnect
Agreement
9
Basis For Screens
Circuit impact
Circuit size versus DG size
Fault handling, fuse
desensitizing &
nuisance trip
DG contribution to fault
Short circuit
handling
Short circuit interrupting
capability limit
Proper connection
Three-wire and four-wire
circuit criteria
Nameplate limits
Single phase
imbalance
10
Screens – Primary
Aggregate 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 limited
DG not allowed to cause grid protective devices to
exceed 90% of their short circuit interrupting capability
In aggregate, DG cannot be > 10MW where transient
stability limits posted
Interconnection configuration-specific limits on singlephase generator hookup and capacity to avoid
imbalance, overload, and possible neutral/grounding
problems
11
Screens – Secondary
Aggregate DG capacity limited to a higher
percentage of the peak load of the
distribution circuit
Basically the same limits on fault current
contribution and short circuit interrupting
impact as primary screen
12
10kW-2MW Costs
Application fee
Additional surcharge for interconnection
review

Limited to reasonable amounts based on size
No other costs for interconnection under
Super Expedited procedures
13
Dispute Resolution
Elements



Technical Master
Hotline
ADR for non-technical disputes
IP must initiate if SG Applicant clears
secondary screen
Gen Applicant has burden if both screens
failed
14
Metering
Only metering required for this agreement is
that necessary to implement the
interconnection
15
Timing
10 days to review application
15 days to review screens
5 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
16
Interconnection Agreement
Standard form Agreement
Shorter form for generators <2MW
Can be pre-executed
17
Interconnection Application
Standard form
Shorter Form for generators <2MW
18
2-20MW Interconnection
Includes transmission impact issues
Direct transmission interconnection as well as
distribution
Used by all generator sizes for which <2MW
procedures do not apply
19
Basic Process
Optional scoping meeting up front
Three main components



Feasibility study
Impact study (if needed)
Facilities study (if needed)
Patterned after Utility proposal
20
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
studies
Gives generator developer idea of
interconnection costs
21
Transmission Impact Study
Only undertaken if Feasibility Study raises
questions of transmission impacts
Usually costly -- to be avoided if possible
If no impact study needed - generator drops
from queue
22
Distribution Impact Study
Purpose


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
23
Facilities Study
Identifies attachment facilities needed for
interconnection including distribution system
upgrades
If no facilities needed (customer sited
generation), no study undertaken
24
2-20MW Costs
To be discussed
Limit interconnection costs to only those
directly related to the application
25
Transmission Queue
To be discussed
FERC is scheduling a conference and possible
NOPR on the subject
26
Interconnection
Agreement/Application
Forms to be developed
27
Massachusetts DTE
DG Interconnection Collaborative
Background
28
IEEE Std 1547 General
Requirements Summary
Voltage regulation inside ANSI C84.1 Range A
Grounding coordinated with Area EPS
Synchronize without voltage fluctuation at PCC >±5%
of prevailing voltages
Networks:
 Spot networks only for now
Feeder
Feeder
NP
NP
Customer
Customer
Customer
Customer
Customer
29
1547 General Requirements
Summary (Continued)
DG shall not energize EPS when EPS is de-energized
DG > 250kVA (unit or aggregate at PCC) shall have provisions for
monitoring DG status, real power, reactive power
When required by EPS, accessible, lockable, visible-break isolation
device (switch) located between DG and EPS
Isolation Switch
Suitable for 70kW DG
30
1547 Abnormal Conditions
Response Summary
Voltages outside of table below shall cause DG to cease to
energize within clearing time
Detected 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
V >= 120
1.00
0.16
31
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 seconds
DG > 30 kW



cease to
cease to
range of
cease to
energize within 0.16 seconds if >60.5 Hz
energize within an adjustable time delay if undervoltage in
59.8 to 57 Hz
energize within 0.16 seconds if <57.0 Hz
After a disturbance, DG reconnect only if voltage and frequency
within range
Interconnection equipment shall be designed to coordinate with
EPS reclosing practices and include ability to delay reconnect up to
5 minutes
32
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)
Current
Distortion
Percent (%)
h<11 11<=h<17 17<=h<23 17<=h<23 35<=h
4.0
2.0
1.5
0.6
0.3
Total Demand Distortion Maximum = 5.0%
Harmonic
33
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
34
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 current
Not cause grid protective devices to exceed 90% of their short circuit
interrupting capability
In aggregate, cannot be >10MW where transient stability limits posted
Phase 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 threephase, 4-wire or a mix
35
Screens – Secondary
Radial circuits: <15% of line section design
capacity
Spot networks: <5% of peak load on spot
networks
Secondary 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
36