Transcript MA Utility Presentation 6.26.12
Presentation for Subcommittee Meeting on Technical Tuesday June 26
th
MA Utilities
Presenters: Neil LaBrake, Jr. and Babak Enayati – National Grid, on behalf of MA Utilities
1
Objectives for DG Technical Discussion by Utilities in MA
Interconnection Standards and Codes Technical Issues, System Modeling Studies Technical Issues, Limits on Distribution EPS (Radial) Technical Issues, Limits on Distribution EPS (Network) Technical Issues, Anti-islanding on Distribution EPS Technical Issues, Protection Requirements Technical Issues, Power System Grounding Technical Issues, Grounding Terminology Standardization of Technical Requirements in MA
2
Interconnection Standards:
Jurisdictional Tariffs, Industry Standards & Codes Jurisdictional Tariff for
MA: M.D.P.U. 1176
https://www.nationalgridus.com/non_html/Expedited%20Standard%20Interconnection/InterconnectStds_MA.pdf
Some industry standards and codes to the EPS that apply to DG interconnections
IEEE 1547
Systems” “Standard for Distributed Resources Interconnected with Electric Power
IEEE 519
“Recommended Practices and Requirements for Harmonic Control Power Systems” in Electrical
IEEE 1453
“Recommended Practice for Measurement and Limits of Voltage Flicker AC Power Systems” on
IEEE C37.90.1
“Standard Surge Withstand Capability (SWC) Tests for Relays Systems Associated with Electric Power Apparatus” and Relay
IEEE C37.90.2
“Standard Withstand Capability of Relay Systems to Radiated Electromagnetic Interference from Transceivers ”
IEEE C37.90.3
“Standard Electrostatic Discharge Tests for Protective Relays ”
UL 1741
Systems” “Inverters, Converters and Charge Controllers for Use in Independent Power
NFPA 70 “National Electrical Code” ( NEC ) NFPA 70B “Recommended Practice for Electrical Equipment Maintenance ” NFPA 70E “Standard for Electrical Safety in the Workplace”
3
Interconnection Standards:
(cont’d)
Industry Standards & Codes - NEC Codes for Installing Renewable Energy Sources
Article 690 National Electrical Code
Requirements for Photovoltaic Installations Wiring in Premises
Article 692 National Electrical Code
Requirements for Fuel Cell Installations in Premises Wiring
Article 694 National Electrical Code
Requirements for Small Wind Electric Energy System Installations in Premises Wiring
Article 705 National Electrical Code
Requirements for Interactive Installations in Premises Wiring
Inspections
are needed for safe, quality installations!
4
Interconnection Standards:
(cont’d)
Utility Reliability Standards
NERC Standard FAC-001-0 - Facility Connection Requirements
Summary:
To avoid adverse impacts on reliability, Transmission Owners must establish facility connection and performance requirements
.
items R2.1.1 through R2.1.16
Northeast Power Coordinating Council
Standard PRC-002-NPCC-01 - Disturbance Monitoring
Purpose:
Ensure that adequate disturbance data is available to facilitate Bulk Electric System event analyses. All references to equipment and facilities herein unless otherwise noted will be to Bulk Electric System (BES) elements
.
Criteria Document A-15 Equipment Criteria - Disturbance Monitoring
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Technical Issues:
System Modeling Studies
Studies will identify:
Thermal overload limit
loading conditions.
or
voltage
violations (steady state) for summer and winter peak
Sensitivity study
(steady state only) to assess the impact of the project
Recommended interconnection configurations during light load conditions
.
Identify the
impact of the project on the bulk and local power network(s)
.
with a list of system upgrades required.
Careful engineering can effectively eliminate the potentially adverse impacts that distributed resource (DR) penetration could impress on the electric delivery system, such as exposing system and customer equipment to potential damage, decrease in power quality, decrease in reliability, extended time to restoration after outage, and potential risks to public and worker safety .
The IEEE supports the following system issues that the utility industry faces with DR penetration on the local
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electric power system (EPS)
.
Technical Issues:
(
cont’d
)
System Modeling Studies
System issues include, but not limited to :
voltage, capacitor operations, voltage regulator and LTC operations.
protection coordination, feeding faults after utility protection opens, interrupting rating of devices, faults on adjacent feeders, fault detection, ground source impacts, single phase interruption on three phase line,
recloser coordination.
conductor burndown, loss of power grid, vulnerability and overvoltages due to islanding, coordination with reclosing, and system restoration and network issues.
Harmonic distortion contributions Voltage flicker Ground fault overvoltages Power system stability System reinforcement Metering
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Technical Issues:
(
cont’d
)
Limits on Distribution EPS
Radial Systems
Distribution or Transmission?
The MA SIDG applies to generators that will connect (grid tied) to the
Distribution System
(below 69kV). For
Transmission System
, apply to the Independent System Operator, ISO (New England or New York).
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Technical Issues:
(
cont’d
)
Limits on Distribution EPS - Radial
The distribution system was not designed with Distributed Generation in mind.
Large generation causes challenges
at this type of system (
i.e. protection, power regulation
…) to distribution and transmission systems.
Based on experience to date ,
upper limits are established
that represent the maximum possible DG capacity under ideal situations and assumes that there are no additional limitations as indicated by site specific system studies (
e.g., available short circuit current contributions, minimum network loading in light loading seasons, voltage regulator interactions, etc
.). When a DG facility (or aggregate DG facility) on a feeder or local EPS of a feeder is
above the limits
, these warrant further study to determine feasibility and remedial action.
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Technical Issues:
(
cont’d
)
Limits on Distribution EPS - Radial
Classification Types
for Typical DG Installation Areas on Radial Distribution Feeders
Types of Generators
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Technical Issues:
(
cont’d
)
Limits on Distribution EPS - Radial Typical Planning Limits
Distribution Feeder for DG Connection to Radial
DG installations are classified into two types - those interconnecting to the utility system on a dedicated radial feeder and those interconnecting on a non-dedicated radial feeder . When a DG (or aggregate DG) on a feeder or local EPS of a feeder is above the limits in the table , these warrant further study to determine feasibility and remedial action.
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Technical Issues:
(
cont’d
)
Limits on Distribution EPS - Radial Typical Planning Limits
Feeder -
cont’d
for DG Connection to Radial Distribution
a.
b.
c.
d.
e.
These generation capacities are on
a per-generator basis on full nameplate ratings and at unity power factor
. It should be noted, however, that the aggregate generation (sum of the total gross generation of all DG systems connected to a particular segment of the Company’s system) is considered for all points along the distribution feeder. The Company will evaluate each application before deciding on the maximum MVA allowed onto the Company’s system at a given point.
Limits apply to synchronous and induction rotating generator machines.
DG facility shall maintain power factor at the PCC in accordance with the MA SIDG; at 0.90 Power Factor leading or lagging (for Var or voltage support can also be considered within machine ratings). The
Inverter-based systems such as Photovoltaic (PV) Systems
shall be limited due to the feeder voltage regulator excessive operation. Operating issues on EPS voltage regulation occur from the effects of cloud transients on large PV systems.
Limits for 25kV and 38kV distribution class systems
determined by the utilities on a case-by-case basis.
in Massachusetts are On
single-phase radial distribution systems
, generators over 50kVA may require three-phase service. Due to the power system imbalance, these situations will be determined by the Company on a case-by-case basis.
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Technical Issues:
(
cont’d
)
Limits on Distribution EPS - Radial
DG facilities typical of synchronous generator and power factor corrected induction generator types ranging in size from 750kVA to 2.8MVA at 4 or 5kV class or from 2.5MVA to 9.0MVA at 15kV class, and installed on non-network systems
are considered for connection to express radial distribution feeders
since the light load condition on the existing feeders may not meet the acceptable norm
to avoid islanding
.
Certain other DG types will have different limits.
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Technical Issues:
(
cont’d
)
Limits on Distribution EPS - Network
The connection of customer DG facilities on networks is an emerging topic, which (i) poses some issues for the Company to maintain adequate voltage and worker safety and (ii) has the potential to cause the power flow on network feeders to shift (
i.e., reverse
) causing network protectors within the network grid to trip open.
To ensure network safety and reliability additional information will be required for the Company’s engineering analysis such as: Electric
demand profile
showing minimum load during peak generation time , Expected
generation profile
shown for a 24-hour period and typical 7-day duration , and Customer’s
complete electric service single-line diagram
up to the service point supplied by the Company’s secondary network EPS.
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Technical Issues:
(
cont’d
)
Anti-Islanding on Distribution EPS - Radial Anti-Islanding Protection
T he interconnection of all parallel generators requires safeguards for synchronization and back-feed situations. A parallel generator is
prohibited to energize a de-energized Company circuit
.
The Company uses
three main “tests”
;
any
determine if anti-islanding protection is required for exceeding minimum load issue or a protection issue or operating concern
:
1.
2.
3.
“Feeder Load versus Generation Test” “Fault Sensitivity Test” “Feeder Selectivity Test” Tips
DG Customer’s protective device coordination study demonstrates generation voltage, current, and/or frequency protection
will trip within 2.00 seconds
for the loss of the utility source.
Type-tested inverter-based
parallel generation mode,
transient overvoltage protection
operated in regulated current
is required
upon detection of an island.
When direct transfer trip (DTT) is specified for a parallel generation project, the
Company will determine
the requirements and responsibilities for equipment, installation, and communications media in the interconnection study.
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Technical Issues
:
(
cont’d
)
Protection Requirements
A parallel generator will contribute to the fault continuously, if the generator is effectively grounded .
Hence, overcurrent (OC) protection is required.
Over/Under (O/U) voltage and frequency protection can be used based on the application (
Load, Generation, etc
.) Some typical relays used to protect the DGs 51: Time Overcurrent (
Mostly for Synchronous Generators
) 51C: Voltage Controlled Overcurrent (
constant and is activated when the voltage drops below a certain limit
)
Current pickup is
27: Under Voltage 59: Over Voltage (
If the utility side of the step up transformer is Delta
) 81O/U: Over/Under Frequency
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Technical Issues :
(
cont’d
)
Power System Grounding
The generator on the Distribution EPS shall not violate the load grounding requirements and voltage limitations during ground faults on the distribution feeder. The load on the Distribution EPS always require effectively grounded system, especially during ground faults the feeder. Hence, the interconnection transformer should be configured properly.
Ungrounded B1 T1 T2 T1 Large Small T2 Small Large B1 Impedance (Reactance) Grounded Effectively Grounded Solidly Grounded 17
Technical Issues :
(
cont’d
)
Grounding Terminology
Effectively Grounded if (X T + 3X L ) / (X T + X 1SYS ) < 3 SYS T
X L
Impedance (Reactance) Grounded 18
Standardization of Technical Requirements in MA
MA DPU
The Massachusetts Standards for Interconnecting Distributed Generation [
MA SIDG
], revised in 2009 is incorporated into MA utilities’ tariffs. For example, National Grid’s tariff is
M.D.P.U. 1176
: https://www.nationalgridus.com/non_html/Expedited%20Standard%20Interconnection/InterconnectStds_MA.pdf
National Grid ESB 756 Appendix C ESB 756
is a supplement to
ESB 750 “Specifications for Electrical Installations”
and the main requirements document for parallel generation connected to National Grid facilities. An Electric System Bulletin (ESB) is a technical document within National Grid. The
ESB 750 series
are a set of information and requirements for customers taking electric service from National Grid. These are available from the National Grid website at www.nationalgridus.com/electricalspecifications .
ESB 756 Appendix C
projects [ applies to the
MA SIDG
typically 5 MWs or smaller in size and complies with tariff, M.D.P.U. 1176. Its purpose is to assist customers desiring to interconnect DG ] to National Grid’s Massachusetts distribution system for State jurisdictional projects. Technical requirements and process are contained here whereby the statutory language, agreements, etc. are located in the tariff, i.e. M.D.P.U. 1176 and referenced.
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Standardization of Technical Requirements in MA
(
cont’d
)
Other Utilities
Similar requirements will greatly assist each utility and developers, installers, and customers in their service areas with parallel generator retail service installations.
Benchmarking of some other utilities’ requirements for DG in the North East and in the US:
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Standardization of Technical Requirements in MA
(
cont’d
)
Allegheny Power (became FirstEnergy in mid-2011):
http://www.alleghenypower.com/csc/services/netmetering.asp
http://www.alleghenypower.com/csc/services/19-35%20SMALL%20GENERATORS.pdf
Central Hudson:
http://www.centralhudson.com/dg/ http://www.centralhudson.com/dg/Central%20Hudson%20Interconnection%20Requirements.pdf
http://www.centralhudson.com/dg/CHGE%20Interconnection%20Requirement%20Figures.pdf
Con Ed:
http://www.coned.com/dg/applications/applications.asp
http://www.coned.com/dg/specs_tariffs/EO-2115.pdf
NYSEG/RG&E:
http://www.nyseg.com/SuppliersAndPartners/distributedgeneration/default.html
Orange & Rockland Utilities:
http://www.oru.com/energyandsafety/distributedgeneration/ http://www.oru.com/documents/energyandsafety/DistributedGeneration/GreaterThan2000kW.pdf
PG&E (California):
Standardization of Technical Requirements in MA
(
cont’d
)
National Grid:
http://www.nationalgridus.com/non_html/shared_constr_esb756.pdf
PECO Energy:
https://www.peco.com/CustomerService/RatesandPricing/RateInformation/Documents/PDF/Self Generated%20Power/Review%20Interconnection%20Guidelines/GrayBook%20Greater%20Than%2 050kW.pdf
We Energies:
http://www.we-energies.com/pdfs/etariffs/wisconsin/ewi_custowngen.pdf
http://www.we-energies.com/business/altenergy/cogen2011guide.pdf
Indianapolis Power & Light:
http://www.iplpower.com/uploadedFiles/iplpowercom/Business/Programs_and_Services/Interconnection%2 0Requirements%20Attachment%20A%2007-08-2011.pdf
https://apps.iplpower.com/GoldBook/Goldbook.html
PSE&G:
http://www.pseg.com/business/builders/new_service/before/ http://www.pseg.com/business/builders/new_service/before/pdf/RequirementsElecSvc2005.pdf
http://www.pseg.com/business/builders/solar_developers/index.jsp
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