This document provides an overview and guidance for municipalities on developing microgrids. It discusses site selection factors, engaging utilities, identifying critical loads, generation sources, controls, and interconnection processes. The presentation emphasizes safety, reliability, and cost effectiveness of microgrids. Interconnection requires coordination with utilities and adherence to technical standards for both grid-connected and island modes of operation.

1. www.trcsolutions.com
April 2, 2014
Microgrids: A Guide for Municipalities

2. 2
Speakers:
Bill Moran
Senior Electrical Engineer
TRC Companies, Inc.
Joseph Debs
Project Manager, Distributed Resources
Connecticut Light and Power Co.

3. 3
Overview
 Microgrid development – where to start
 Interconnection
 Load management
 Generation sources
 Microgrid controls and operation

4. 4
Microgrid Development – Site selection
 Multiple critical facilities
 Physical location – within reasonable walking distance
 Widely spaced facilities with numerous non‐critical
sites interspersed will greatly increase cost of microgrid
 Widely spaced facilities with numerous non‐critical
sites between will greatly increase cost of microgrid
 Are all microgrid facilities within a campus, or will
power have to cross public roads?
 What does the Microgrid look like?

5. 5

6. 6

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8. 8
Microgrid Development – Site selection
 Meet with EDU/MEU
 Questions to ask:
‐ Are all of the Critical Facilities now served from the same feeder circuit?
‐ What is the primary service voltage?
‐ How difficult (expensive) will it be to isolate these facilities from the rest
of the grid?
‐ What portions of the proposed microgrid would be constructed owed
and operated by the EDU/MEU?
‐ Will other customers be affected?
‐ What are the historical electrical demand loads for the critical facilities?

9. 9
Microgrid Development –
Select Engineer/Developer
Qualifications needed:
 Prior experience in designing, building microgrid or
distributed generation projects
 Experienced working with EDU/MEU
 Must work closely with host facility and other
project stakeholders
 Well capitalized

10. 10
Microgrid Development –
Identify Critical Facility Load
Sources of information:
 Facility “demand load” information provided by EDU/MEU
 Check utility bills for “kW demand “
Consider load management:
 Are all facility loads essential, or can some be shed during
emergency conditions?
 Do all peak loads occur under the same time or weather
conditions?
 Can some loads be time‐shifted, i.e deferred to off peak
times (example: water heating, dishwashing etc.)

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Selection of Generation Sources
 Efficiency
 Environment
 Fuel Source
‐ Non‐interruptible OR
‐ 2 week supply
 Load following ability
 Voltage and frequency source
‐ Most inverter based sources not grid independent.
 Location within microgrid
‐ Central within microgrid preferable
‐ Single location preferable to scattered generators
‐ Noise and environmental concerns
‐ Thermal and other efficiency concerns.
 Total generation capacity 120% of critical facility load.

12. CT landscape and PA 12‐148
"Microgrid" means a group of interconnected loads and
distributed energy resources within clearly defined electrical
boundaries that acts as a single controllable entity with respect
to the grid and that connects and disconnects from such grid to
enable it to operate in both grid‐connected or island mode.
12

13. CT Interconnection Rules
 Collaborated efforts over the past 10 years on lessons learned
 CL&P & UI follow the same process and technical guidelines
 Guidelines approved by Public Utility Regulatory Authority
(PURA)
 Guidelines are based on the Federal Energy Regulatory
Commission (FERC) Small Generator Interconnection Process
(SGIP) model
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14. Types of Microgrid
Type 1: Campus Style Microgrid
In this configuration the electrical distribution infrastructure is
owned and operated by a single or multiple entities (owner /
operator) and does not include islanding of any of the Electrical
Distribution Company assets.
– The generator has the ability to island with no interface
with the utility Electrical Distribution Company
14

15. Campus style Microgrid
CB

16. Type of Microgrid
Type 2: Microgrid with Utility Owned Distribution Facilities:
In this configuration a portion of the Electrical Distribution
Company assets along with selected loads are intentionally
interconnected with dedicated generation supplying the loads.
– The generator will need to coordinate with the EDC
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17. Microgrid with Utility Owned Distribution Facilities:
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18. The Interconnection Process
 Scope:
‐ Scoping Meeting
‐ Review for grid connected mode(Normal Interconnection
process)
‐ Review of operational procedure (Joint Operation)
‐ Review in Island mode will include Protection, voltage,
frequency & short circuit impact
‐ Design Electrical distribution system to support Microgrid
‐ Design of communication system (SCADA)
 Timelines: Depends on complexity of project
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19. Review of operational procedure
 A detailed Operation procedure is required and must consider
the following:
‐ Operation in grid connected mode
‐ Operation in island mode
‐ Reconnect to the grid (under direction of EDC)
‐ Interlocks (Mechanical and Electrical)
‐ Protective Functions in grid and Island mode
 Refer to Attachment C for additional information
19

20. Additional Considerations
 Manual vs. Automatic operation
 Operation and Ownership of grid isolation device(s)
 Electrical Distribution Company operating procedures
 Maintenance
 Cost of upgrades of EDC Facilities (development , installation
and operation of Microgrid
 Real time communication with EDC (SCADA) if needed
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21. Basic Understanding
 Understanding limitation and possible delays associated
with restoration of normal power
 Understanding that EDC role is to serve all customers needs
including non Microgrid customers, Microgrid should not
impact other customers
 Upgrades material and practices must be consistent with
EDC standard practices to facilitate restoration efforts in
event of equipment failure
 Define methodology to initiate an island mode
 Define methodology to return to normal operation
21

22. Successful Application Components
Application
 Guidelines
 Fee
 Complete Application
 Application Signature
 Insurance
 Technical data sheets
 Number of inverters / Generation
 Utility account and/or meter number
 Ownership
‐ Property
‐ Third party ownership of generator
22

23. Successful Application Components
Technical
 Exhibit B of the Guidelines
 Electrical One‐Line diagram with standard symbols and labels
 Timely communication and data transfer
 Receive contingent approval prior to construction
 Disconnect switch
 Compliance with meter and service requirements
 Detailed sequence of operation and test plan
 Provide detailed relaying information
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24. Typical One Line
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25. 25
One‐Line Electrical Diagram
 Must be prepared and stamped by a Connecticut Licensed
Professional Engineer
 Requirements specified in RFP Attachment C
‐ ANSI/IEEE standard symbols
‐ Point(s) of common coupling shown
‐ Location and type of isolation switch shown
‐ All protective relay functions shown
‐ Transformer grounding shown
‐ Transformer impedances shown
‐ Meters and metering connections shown

26. Pillars of a Successful Interconnection
Safety
Reliability Cost
Successful
Interconnection
26

27. 27
Island Operation
Voltage control
 System voltage must be maintained by generators
 ANSI c84‐1
 Motor starting
 Multiple generator VAR load sharing.
 Transfer off/on grid.
‐ Voltage matching
‐ Synchronization

28. 28
Island Operation
Control System Frequency
 Frequency vs. load control.
‐ Grid Parallel: control generator load
‐ Islanded: control system frequency
‐ Isochronous
‐ Droop
‐ Isochronous load sharing
‐ Load following ability – ramp rate
‐ Parallel generator operation
‐ Effect of uncontrolled renewable sources

29. 29
Characteristics of Different Generator Types
 Synchronous
‐ Voltage and current source
‐ Grid parallel or independent
 Induction
‐ Current source
‐ No reactive power (VAR) capability
‐ Can not operate grid independent
 Inverter
‐ Current source
‐ Voltage source/self‐commutating
‐ UL 1741 compliance
‐ Includes anti‐islanding provisions

30. 30
Characteristics of Different Generator Types
Prime mover types
 Diesel engine
 Gaseous fueled reciprocating (Otto cycle)
‐ Rich burn
‐ Lean burn
 Gas turbine
 Fuel cell
 Inverter – PV, Wind etc.
 Other
‐ Steam turbine
‐ Hydro

31. 31
Characteristics of Different Generator Types
Ramp Rate (Load acceptance)
 Load – unload speed
 Diesel ‐ 100% block load capable
 Inverter with storage – block load capable
 Gas turbine 100‐200 kW/second for MW size units
 Fuel cells 3‐10 kW/second
 Lean burn gas recip. 2‐3 kW/sec. (small units)
 Rich burn gas recip. ‐ near block load
‐ 50% ‐ 100% well tolerated depending on manufacturer

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Ways to mitigate slow ramp rates
 Load bank
‐ Inefficient
 Storage
‐ Efficient
‐ More effective use of generating capacity
‐ Expensive
‐ Can reduce spinning reserve requirements.
 Base load vs. peaking units
‐ Slow ramping units operate at nearly constant load
‐ Load following done by generators with rapid response
capability
‐ Example: base load fuel cells with diesels used for load
following

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Microgrid Controls
Operation when grid connected
 Frequency controlled by grid
 Voltage controlled by grid
 Reactive power (VAR) demand supplied by grid
 Distributed generation controlled to maintain desired power output
(kW)
 Higher available fault current

35. 35
Microgrid Controls
Islanded Operation
 System voltage and frequency controlled by microgrid generation
 All instantaneous load peaks must be carried by microgrid
generation
 All VAR demand must be met by microgrid generation
‐ Motor starting is a consideration
‐ Elevators
‐ Air conditioning equipment
‐ Refrigeration/ industrial loads.
‐ Inverters have little ability to handle VAR demand
‐ Synchronous generators best able to provide reserve VARs

36. 36
Microgrid Controls
Islanded Operation
 Frequency must be controlled by generation
 Microgrid must be able to absorb swings in load
 Ramp rate of generators becomes an issue
 How is load shared among multiple generators?
 Isochronous vs. droop governing
 Lower available fault current
‐ Will likely require different settings for protective relays
‐ Different short circuit coordination requirements
‐ Potentially greater arc‐flash requirements

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Microgrid Controls
Load management
 Spinning reserve
 120% of facility load
 Load peak reduction
‐ Shedding of less critical loads
‐ Load shifting
‐ Load shedding response ‐ instantaneous (3‐5 cycles)
 Contingency management
 Partial generator loss
‐ Must reduce load immediately to less than 100% of on‐line
generation to avoid blackout
‐ Building EMS systems can not react fast enough to reduce load

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Microgrid Controls
Transition control
 Grid Parallel to Island Operation
‐ Grid tie circuit breaker trips open
‐ Excess load shed if spinning generators have less capacity than
load. (high speed load shed)
‐ All generators switch from load control to frequency control
‐ All generators switch from power factor control to voltage
control
‐ Additional generation brought on‐line if needed.
‐ Previously shed loads can be restored, if microgrid has full
generation capacity

40. 40
Microgrid Controls
Transition control
 Island Operation to Grid Parallel
‐ Generators adjust to match grid voltage
‐ Microgrid frequency and phase angle adjusted to match grid
‐ Grid tie circuit breaker closed
‐ Generators switch to load (output) control
‐ Generators switch from voltage to power factor control
‐ Excess generation can be shut down according to normal
operating schedule
‐ Any non‐critical loads shed during island operation can be
restored

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43. 43
Conclusion
Microgrid Development
 Identify Facilities to be served
 Consult with EDC/MEU for feasibility
 Identify Facility loads
 Seek developer/engineer
Design
 Design interconnection and physical layout of Microgrid
 Select and locate appropriate generation sources
 Configure load management controls
 Obtain Interconnection Agreement

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Conclusion
Construction
 Purchase and install generation equipment
 EDC/MEU to construct system modifications to serve microgrid.
 Construct customer owned distribution and interconnection.
Testing and Commissioning
 Electrical testing
 Approval to energize
 Performance testing
 Environmental (air) testing
 Islanding demonstration
Operations
 Generation in operation
 Operations management in place
 Routine maintained scheduled.
 Annual reports

45. Questions?
Bill Moran, TRC Companies, Inc.
P: 774‐235‐2602 | E: wmoran@trcsolutions.com
www.trcsolutions.com
DEEP Microgrid program
E: DEEP.Energy Bureau@ct.gov
Joe Debs, Connecticut Light and Power Co.
P: 860‐665‐5616 | E: joseph.debs@nu.com
Pat Healy, United Illuminating Co.
P: (203) 926‐5257 | E: Pat.Healey@uinet.com