Alternative Power Systems

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Alternative Power Systems
Spring Semester 2005 Project
Assignment Group IV Standards for
Interconnection of small Photovoltaic and Wind
Turbine systems to the Utility grid in Mississippi
Sandhya Sankar Shravana K.
Musunuri Jimmy Mathews Graduate
Students Department of Electrical
Computer Engineering Mississippi
State University, MS 39762 Instructor
Dr. Michael S. Mazzola
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Presentation Outline

• Overview of Standards and Codes related to
  grid-interconnection of common residential PV
  and Wind systems.
• Present Interconnection trends with an insight of
  system components and functions (with reference
  to key elements of standards and codes)
• Reference Sources

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Interconnection Standards

• National
• IEEE 1547 2003 Standard for Interconnecting
  Distributed Resources with Electric Power Systems
• IEEE Std. 519 1992 IEEE recommended practices
  and requirements for harmonic control in
  electrical power systems
• PV systems
• IEEE 929 2000 Recommended Practice for
  Utility Interface of Photovoltaic (PV) Systems
  (Superceded by IEEE 1547)
• IEEE 1374 1998 IEEE guide for terrestrial
  photovoltaic power system safety
• US National Electrical Code (NEC) Article 690
  Solar Photovoltaic Systems
• Wind Turbines
• IEEE Std. 1094-1991 IEEE recommended practice
  for the electrical design and operation of wind
  farm generating stations
• IEEE P1547 2003 IEEE 929 2000 also employed
  selectively
• State
• Standardized Interconnection Requirements (SIR)
  for Mississippi State None
• Industry
• UL 1741 Inverters, Converters, and Controllers
  for Use in Independent Power Systems
• Others
• ANSI C84.1 - 1995 American National Standards
  Institute, Electric Power Systems and Equipment
  Voltage Ratings (60 Hz)
• US National Electrical Code (NEC) Article 705
  Interconnected Electric Power Production Sources

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Keypoints of standards for small systems

• Voltage Requirements
• - For normal conditions and the required
  regulation is /- 5 on a 120-volt base at the
  service entrance i.e. 114 V 126 V (ANSI
  C84.1-1995, Range A)
• -

• Frequency Requirements
• - For DR lt 30kW frequency ranges and clearing
  times are as in Table 2 (IEEE 1547-2003)

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Keypoints of standards for small systems

• Power Quality
• - DC injection current from DR interconnection
  system limited to 0.5 of full rated output
  current
• - For balanced loads, harmonic current injection
  limits into Area EPS at PCC in Table 3 (IEEE
  1547-2003)

• Harmonic Current Distortion limits (IEEE
  519-1992)
• - All generation, whether connected to
  distribution, sub-transmission or transmission
  system, is treated like utility distribution and
  is hence held to recommended practices as in
  Table 5.

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Keypoints of standards for small systems

• Power factor (IEEE 1547-2003)
• - The PV system should operate at a power factor
  gt 0.85 (lagging or leading) when output is gt 10
  of rating
• - PV inverters designed for utility-interconnecte
  d service operate close to unity power factor

IEEE 929-2000 - Current THD shall be less than 5
of the fundamental frequency current at rated
inverter output. - The inverter shut down should
occur within 10 cycles if the utility voltage
drops below by either 50 or increase above
110of its nominal value. - Islanding protection
using an anti-islanding inverter, if the utility
line voltage is between 50 and 92 of its
nominal value, the inverter should shut down in 2
seconds

• IEEE 1374-1998
• Equipment Ratings
• - Voltage ratings of the cable, switchgear, and
  overcurrent devices are based on the higher
  number of the pair (i.e., 700 V in a 350/700 V
  system)

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Keypoints of standards for small systems

• NEC Code 690
• - 690.13(A) Disconnect means shall be provided
  between photovoltaic power system output and
  other building conductors, no disconnect in
  grounded conductor
• - 690.2 DC operating voltages of 12 volts up to
  600 volts, with AC outputs from 120 V single
  phase to 480 V three phase
• - 690.2 Inverters for PV systems in sizes from
  100 W to custom designs of up to 1 MW or more
• - 690.8 Conductors and overcurrent devices to
  be sized such that over current devices shall not
  be operated continuously at more than 80

• IEEE 1094-1991
• Wind Turbine System Interconnection
  Considerations
• - Low voltage systems should connect to low
  voltage/medium voltage step-up transformers.
• - Underground cables typically used for the
  low-voltage collection system.
• - Protection concepts similar to those of utility
  and industrial systems involving the same
  voltages.

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Keypoints of standards for small systems

• UL 1741
• Power Quality
• - Utility connected DG products must meet
  minimum output power quality requirements like
  output p.f. of 0.85 or higher, harmonic
  distortion lt 5 at full output power and DC
  injection current less than 0.5 of rated output
  current.
• Miscellaneous
• - Addresses electric shock hazards, fire
  hazards, mechanical hazards, issues of utility
  compatibility and interconnection for grid-tied
  applications
• - Ratings, markings, specific DR tests for
  various technologies, protection against risks of
  injury to persons and construction.
• - Tests anti-islanding response
• - Surge withstand capability testing to be added
  in the future revision along with IEEE 1547
  requirements

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Example only-wiring setup for installation in
TVAs Green Power Switch Generation Partners
program
Suggested wiring example for illustration only.
Actual installation setup and requirements
according to Participation Agreement.
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Example only-wiring setup (contd)

• Notes
• Warning sign requirements should be adhered to.
• Blade disconnect shall be lockable, 3-pole
  disconnect.
• House main panel should accommodate conductors
  feeding from the utility and alternate power
  source disconnects. Terminations of conductors
  shall have to be double-lugged.
• Photovoltaic system shall be installed to meet
  all requirements of the NEC, including Article
  690. This system shall be inspected by the local
  authority having jurisdiction to verify code
  compliance. Photovoltaic inverter system shall
  be listed for grid interconnection by UL
  (UL1741).
• Each type of system must have its own generation
  meter.

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Additional References

• IEEE Standards
• Onaje Jackson, "General Overview of Utility
  Interactive PV Systems, Design Recommendations,
  and Code Compliance," US Virgin Islands PV/DG
  Road Show
• Andris Garsils, Interconnecting Distributed
  Generation With Utility Grids, EEI Spring
  Transmission, Distribution and Metering
  Conference, Charlotte, NC. April 2004
• Ben Kroposki, Tom Basso, Dick DeBlasio, Tying
  pre-certification to IEEE 1547, National
  Renewable Energy Laboratory, PJM Small Generation
  Interconnection Working Group, May 2004
• R. Messenger, J. Ventre, Photovoltaic Systems
  Engineering, CRC press, 2000
• Chris Larsen , Distributed Generation
  Interconnection Standards , IREC Interconnection
  Workshop, Wichita, KS October 1, 2003
• Wiring setup for TVA Green Power Switch
  Generation Partners program