Northeast Utilities Senior Design Project

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Northeast Utilities Senior Design Project
Michael A. Gargano (Overview) William H. Morrison
(Theory) Rodney Plettner (Software) Mark Pacileo
(Mapping) Advisors Rajeev Bansal and Steven Boggs
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Project Goals

• Enable NU to select substations pairs for
  immediate parallel operation
• Derive trends from project data for general
  parametric analysis
• Provide NU with analysis for future substation
  construction

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Practical Application
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Procedure

• The load-flow software will be installed on UConn
  computers
• Build a scaled version of the 115kv NU
  transmission/substation system
• The Team will conduct a load-flow analysis study
  of the 107 substations on the 115kv system

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Whats Been Done

• So far we have
• We have assimilated the 75 pages of NU data into
  Excel
• Mapped all substations onto a Connecticut site
  map
• Begun identifying possible substation pairs
  through specific parameters

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Constraints and Restrictions

• Distribution Voltages must be on the same
  per-unit base
• Transmission system must be whole and fully
  operational
• Vector distance between subs not to exceed 30
  miles
• Delta-Wye substations will not be tied
• 115 kv and 69 kv systems are one system
• No ties to other Utility Owners

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Parameters of Interest

• Current thru TRs and SRs
• Phase Angle
• Line Impedance
• Transformer Impedance
• Substation Load
• Tap Changers (on Transmission side)

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The Per-Unit System

• Makes calculations easier
• Focuses on actual changes in a system
• The system that almost all power engineers use
• If a system is a 13.6kV system and the actual
  voltage is 13.78kV, then the per-unit value is

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Examples of Per Unit Values
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Impedance

• Impedance varies with distance.
• Reactive part increases with distance
• Impedance changes depending on line
  configurations
• Due to this we have a limit of 30 miles

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Phase Angles

• The reactive elements of the network determine
  the phase angle
• Differences in phase angles between substations
  will result in a voltage differential
• If the phase angle difference is too large and
  the distribution line impedance is too low, too
  much current will flow

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Examples of Phase Angles

• Mansfield to Glenbrook
• Mansfield is 75.88
• Glenbrook is 116.44
• Difference is
• 40.56

• N. Canaan to Salisbury
• N Canaan is 99.4
• Salisbury is 98.02
• Difference is
• 1.38

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Load Flow Analysis

• Software to be used and how
• Power Flow Software
• Power System Simulator for Engineering (PSS/E)
• Designed by Power Technologies, Inc
• Used by North East Utilities
• Why not Matlab or Pspice?
• Time/Modification of data
• Not specifically designed for utility simulation

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Load Flow Analysis cont.

• Software to be used cont.
• Ordered PSS/E from PTI
• Due to security clearance we will use PSS/E at
  Uconn
• Will arrive before spring semester 2003
• How will we use the software?
• Data gathered for 115KV system
• Actual transformer, load and phase angle values
• Other various parameters
• Data evaluated graphically

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How will we use the data?

• Build power models
• Transformers
• Loads
• Tie reclosers
• Sectionalizing reclosers
• Enter actual substation parameters using GUI
  (graphical user interface)
• Run simulation on substation pairs

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After the Simulations

• Know the current through tie reclosers
• Produce a list of possible substation pairings
  for future reference by NU

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115kV Substations

• 107 NU substations
• Without restrictions 5671 combinations

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Limitations

• Substations must have same base voltage
• Vector distance must be less than or equal to 30
  miles
• Line distance approximately 10 longer because
  there is no distribution along highways
• Allowable current through a tie recloser is 50
  Amps

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Litchfield County
13.2kV Distribution Voltage
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Substation Pairs
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Conclusion

• This study will enable NU to
• Pick substation pairs for immediate parallel
  operation for particular outage situations
• Provide valuable information for future
  substation construction and location via general
  study

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