© 2015 Electric Power Research Institute, Inc. All rights reserved.
Dr. Arindam Maitra, EPRI
September 8, 2016
Microgrid Design
Considerations
Part 3 of 3
2
© 2015 Electric Power Research Institute, Inc. All rights reserved.
Outline – Microgrid Design and Analysis Tutorial
Part II
Time Topics
14:30-15:00
15:30-17:30
Design analysis• Needs and Key Interconnection Issues (Arindam Maitra)
Design analysis (cont.)• Methods and Tools
• Case Studies
#1: Renewable Rich Microgrids - Protection Case Studies
(Mohamed El Khatib)
#2: Rural radial
#3: Secondary n/w
17:00-17:30 Q&A
17:30 Adjourn
3© 2015 Electric Power Research Institute, Inc. All rights reserved.
Microgrids
Optimization of microgrid design is challenging and
inherently contains many unknowns…
Regulatory Issues
Costs
Value of Resiliency
System Design
Challenges
Engineering Studies
4© 2015 Electric Power Research Institute, Inc. All rights reserved.
Integrating Customer DER with Utility Assets
Distribution Transformer
Energy Storage*
Micro Grid Controller/ DERMS*
Customer
Assets
Utility Assets
Isolating Device*
Integrate
d Grid
SCADA/DMS/Enterprise
*New assets
5
© 2015 Electric Power Research Institute, Inc. All rights reserved.
Microgrid Types
Commercial/Industrial Microgrids: Built with the goal of reducing demand and costs
during normal operation, although the operation of critical functions during outages is
also important, especially for data centers.
Community/City/Utility and Network Microgrids: Improve reliability of critical
infrastructure, deferred asset investment, emission and energy policy targets and also
promote community participation.
University Campus Microgrids: Meet the high reliability needs for research labs,
campus housing, large heating and cooling demands at large cost reduction
opportunities, and lower emission targets. Most campuses already have DG resources,
with microgrid technology linking them together. They are usually large and may be
involved with selling excess power to the grid. Some of these facilities typically serve
as emergency shelters for surrounding communities during extreme events
Public Institutional Microgrids: Improve reliability and lower energy consumptions at
facilities impacting public health and safety, including hospitals, police and fire stations,
sewage treatment plants, schools, public transport systems, and correctional facilities.
Additional requirement of uninterrupted electrical and thermal service increases
attractiveness of CHP-based district energy solutions
6
© 2015 Electric Power Research Institute, Inc. All rights reserved.
Microgrid Types
Military Microgrids: Military microgrids focus on high reliability for mission-critical loads,
strong needs for cyber and physical security, DoD energy cost reduction, and
greenhouse gas emission reduction goals at the operating bases.
Rural Microgrid Communities: Remote microgrid communities are typically connected
to rural distribution system where it is prohibitive due to the distance or a physical
barrier to bring in new transmission service for backup. Many already use diesel
generation. They microgrids offer best candidate to incorporate renewable energy,
improve system reliability targets, and defer investment and reduce supply chain risk.
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Microgrid Configurations Depending on Location and Purpose
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Micro-grid: Operating as an “Island” Isolated from the
Bulk Supply
Utility
Source
“Islanded” Facility
DG
Trip
Signal
Circuit Breaker Isolating Device
– when open the system
operates as micro-grid
Islanding Control
(opens/closes breaker as needed to
facilitate independent operation –
must provide synchronization)
Electrical Island
DG Able to Carry Load on
Island and Provide Proper
Voltage and Frequency
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Utility System
Interface Breaker
Utility Substation
Building
Load
Building
Load
Building
Load
Building
Load
Building
Load
13.2 kV Feeder
“Islanded” campus area
during utility system outages
DG trip settings for DG coordinated to allow
utility system interface breaker to trip during
utility faults so that stable transition to
islanded state is achieved for the campus
without interruption of DG service
“Islanding” for Reliability Enhancement
D
G
D
G
10© 2015 Electric Power Research Institute, Inc. All rights reserved.
Distribution
Transformer
Utility System
Primary (13.2 kV)
50 KVA
Inverter
Utility System
Interface &
Controller (Synchronization, fault
protection, islanding
detection, etc.)
Power System
Secondary
(120/240 V)
Charge
Regulator
Energy
Storage
Isolating
Device
Heat
Distribution
DC Bus
Thermal
Storage
House 1 House 2 House 3
House 4 House 5 House 6
Fuel
Cell
A Six Home Microgrid
11© 2015 Electric Power Research Institute, Inc. All rights reserved.
Utility
Source
INVERTER
Utility System Interface
& Protection Control
Energy
Storage
Building
Thermal
Loads
Heat
Recovery
Rectification
and Filtering
20 kW
Wind
Energy
Source
Circuit
Breaker
Circuit
Breaker
Status/control
signals paths to/from
electrical loads
Status/control signal
paths to/from thermal
loads
Master
System
Controller
Building
Electrical
Loads
200 kW
Fuel Cell
DC Bus
AC BusServes as Isolation Point
for Micro-grid mode of
operation
A Single Building
Multiple Sources, Storage, and Heat Recovery
Charge/Discharge
Regulator
12© 2015 Electric Power Research Institute, Inc. All rights reserved.
A Campus Microgrid System
Utility System
Primary Connection
(13.2 kV)
Utility System Interface Control(Synchronization, fault
protection, islanding detection, etc.)
Campus Owned
Distribution (13.2 kV)
Isolating Device (opens
during micro-grid mode)
Heat Distribution
Academic Building A
Dormitory B Administrative
Building
Dormitory A
Student
Union
Academic
Building B
To Other
Campus
Loads
500 kVA 500 kVA 300 kVA
75 kVA
800 kVA
300
kVA
Generator
Step Up
Transformer
GenGenGen
Generator
Protection
and Control
Paralleling Bus (4.8 kV)
Voltage
Regulator
Heat Distribution
1.75
MVA
1.75
MVA1.75
MVA
Heat Recovered
from ICE Units
Load
control
Communication & Control Signal Path
13© 2015 Electric Power Research Institute, Inc. All rights reserved.
Microgrid Design Parameters
Number of customers served
Physical length of circuits and types of loads to be served
Voltage levels to be used
Feeder configuration (looped, networked, radial)
Types of distributed energy resources utilized
AC or DC microgrid
Heat-recovery options
Desired power quality and reliability levels
Methods of control and protection
Controllers
Urban Utility
Microgrids
Rural Utility
Microgrids
Non-Utility Microgrids
Remote / Island
Microgrids
Application Downtown
Areas
Planned
Islanding
Load Support
Commercial /
Industrial Clusters
University Campus
Residential
Development
Remote
Communities
and Loads
Geographical
Islands
Main Drivers
Improved Reliability;
Outage Management;
Renewable and CHP Integration
Reliability and
Power Quality
Enhancement;
Energy Efficiency;
Electrification of
Remote Areas
Benefits
Improved Reliability;
Fuel Diversity;
Congestion Management;
Greenhouse Gas Reduction;
Upgrade Deferral;
Ancillary Services
Premium Power
Quality;
CHP Integration;
Demand Response
Management
Supply
Availability
Integration of
Renewables
Grid-
Connected Primary Mode of Operation
Primary Mode of
Operation Never
Intentional
Islanding
Nearby faults or System
Disturbances
Approaching Storms
Nearby faults or
System Disturbances
Times of Peak
Energy Prices
Approaching Storms
Always Islanded
Source: Johan Driesen and Farid Katiraei, “Design for Distributed Energy Resources,” IEEE Power & Energy Magazine,
May/June 2008
14© 2015 Electric Power Research Institute, Inc. All rights reserved.
Microgrid Design Elements
• Are DERs able to regulate the voltage and
frequency within the island?
• Any issues with parallel grid operation?
• How is re-synchronization checked
against criteria such as out-of-phase, large
change in voltage?
Need a microgrid controller
• Are the fault contributions from
DERs sufficient to allow
satisfactory operation of
protection systems?
• Are existing protection schemes
adequate?
Plan, design, operate, control, monitor and optimize seamlessly
Microgrids
15© 2015 Electric Power Research Institute, Inc. All rights reserved.
Microgrid Detailed Technical Design
Microgrid Project Objectives
Design Basis and Rationale
Performance Criteria
Site Descriptions
• Electrical & Thermal Needs• Generation Assets
• Critical Load Needs• Power Distribution Equip.
DER & Microgrid Controller
Codes & Standards
Control NeedsCommunication Needs
16© 2015 Electric Power Research Institute, Inc. All rights reserved.
DER Characterization
Renewables
Solar Photovoltaics
Solar Thermal
Wind
Fossil Fuels Tech
Boiler
Fuel Cell
Microturbine
NG Genset
Diesel (backup)
Energy Storage
Electrical (Power, Energy)
Thermal (Chiller, Refrig.)
Thermal Tech
Heat Pump
CHP
HVACR
Solar Thermal
Other
Electric Vehicles
Electric Storage
• Aggregate capacity of all units (kwh)
• Maximum charge rate
(fraction of total capacity charge in one hour)
• Maximum discharge rate
(fraction of total capacity discharge per hour)
• Minimum state of charge
• Charge efficiency
• Discharge efficiency
• Decay/self-discharge (fraction of total capacity per
hour)
----------------------------------
• Fixed cost ($)
• Variable Cost ($/kw or $/kwh)
• Lifetime (years)
• O&M fixed costs ($/year)
Solar Photovoltaics
• # of modules
• Module rating (kW DC)
• Module Size (m2)
• Efficiency (%)
• Inverter size (kW AC)
• Total land area (m2)
----------------------------------
• Capital cost ($)
• Lifetime (years)
• O&M fixed costs ($/year)
• O&M variable costs ($/year/kW)
Microturbine
• Max Power (kW)
• Sprint capacity (% of power)
• # of sprint hours (hours)
• Fuel type
• Efficiency (ratio)
• CHP capable? (yes/no)
• Alpha (power to heat ratio)
• NOx emissions rate (kg/hr)
• Maximum annual operating hours (hours)
• Minimum loading (% of power)
----------------------------------
• Capital cost ($)
• Lifetime (years)
• O&M fixed costs ($/year)
• O&M variable costs ($/year/unit)
• NOx treatment costs ($/kg)
Electric Vehicles
• Multiple locations
• Min connect/disconnect SOC
• Max charge hours
• Battery size
• Efficiency
• Decay
• etc.
t
Connect
Disconnect
SOC
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Variable Distributed Energy Assets within Microgrid
Sourc
e: P
NN
L
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Key Considerations in Design for Energy Storage
Standby Power Loss
– Storage is primarily needed
when the microgrid is islanded
– Standby power loss will reduce
the efficiency of the microgrid
• Response time
– For seamless transition, response
time must be very fast
– This is more than just battery
response time – communications
latency and control functions also
play a role
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Isochronous / Droop Modes of Operation
Isochronous - Isochronous control mode means that the frequency (and voltage) of the electricity generated is held constant, and there is zero generator droop.
Droop Control Mode - strategy commonly applied to generators for frequency control (and occasionally voltage control) to allow parallel generator operation (e.g. load sharing).
For grid-tied microgrids – all the DG and storage resources operate in droop mode and the utility is the isochronous generator reference.
For off-grid microgrids – one generating unit is designated to run in isochronous mode and all other follow in droop mode. Larger units and higher inertia prime movers are normally the reference machine. PV inverters are nearly always operating in droop mode. Battery inverters may operate either way when generating.
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Controller Integration
Source: EPRI DOE SHINES Project
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Microgrid Technical Challenges : Protection
Not enough short-circuit current in Microgrid mode for
protection to sense and operate
– Voltage-based protection was recommended : No
need for multiple settings group to support grid or
islanded operation
May require additional equipment and change in
protection settings.
Insulation coordination could be an issue
Microgrid operation may result in loss of effective ground
reference
Keeping protection scheme simple translates into improved
dependability as well as much simpler analysis in the event of
misoperation
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For a small microgrid: need to understand the load Daily, from hourly to cycles in single family residence Knoxville, TN
8.0 kWmax
85.1 kWh
44% Load factor
10.7 kWmax
85.1 kWh
33%
26.2 kWmax
85.1 kWh
14%
14.8 kWmax
85.1 kWh
24%
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PQ Enhancements Possible
Instant Islanding to mitigate campus interruptions caused by feeder faults
Proactive islanding due to “expected” feeder interruption or voltage sag (e.g. approaching lightning storm)
Partial voltage sag mitigation by means of DG voltage support during fault!
Improved local voltage flicker and regulation due to lower impedance of power system
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Low Voltage Ride-Through
No low voltage ride-through requirements in the current IEEE
Std1547-2003 version (or the amendments)
A full revision of the 1547 is under way – inclusion of ride-through
requirements is considered
The CA Rule 21 ride-through requirements will likely inform the IEEE
Std 1547 ride-through requirements
The inverter must stop
producing power but be ready
to produce power again if the
voltage starts to normalize
before the inverter is allowed
to trip
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Dynamic Models and Controls
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Micro-Grid Switching - MV vs LV
Typical Main Switch
Jn. Box
12 kV
12 kV
Service
Xfmr
12 kV/
208V
MV-CB
From Utility
Building
Load
Point Of
Control
JC12 kV
Service
Xfmr
12 kV/
208V
MV-CB
LV-CB
Point Of
Control
Building
Load
LV-CB
Building
PV
Typical Main Switch 12 kV
From Utility
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Micro-Grid Switching at MV Level
Approach:
Circuit breakers are available only at 12kV main
ring. No 12kV circuit breakers downstream.
Each circuit breaker controls a group of
transformers/buildings.
Control is at the group level. No individual
control at building level
Consequences:
Switching OFF a transformer on 12kV side
disconnects both building loads and connected
PV. This results in loss of generation (PV on non
critical buildings) when resources are needed
during islanded operation.
This design necessitates permanently assigning
buildings as critical and non-critical. It is not
possible to reassign them later.
12KV switching could cause high transformer
inrush currents during black start. Mitigating
equipment may be required if storage inverters
are not able to handle this high inrush current.
Typical Main Switch
Jn. Box
12 kV
12 kV
Service
Xfmr
12 kV/
208V
MV-CB
From Utility
Building
Load
Point Of
Control
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Micro-Grid Switching at LV
Approach:
Control is shifted to the Low Voltage side.
Transformers are connected to buildings through
Low Voltage distribution boards.
This creates the ability to separately control loads
and generation within the buildings.
Consequences:
No loss of generation (PV on non critical
buildings) when loads are disconnected during
islanded operation.
Ability to reassign buildings as critical / non-
critical as and when needed.
As loads are disconnected from the LV side it is
possible to reestablish the MV ring through soft
start with all transformers connected. This could
reduce inrush current significantly.
JC12 kV
Service
Xfmr
12 kV/
208V
MV-CB
LV-CB
Point Of
Control
Building
Load
LV-CB
Building
PV
Typical Main Switch 12 kV
From Utility
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Transformer inrush current and its impact
Inrush current during the energizing could be much higher than
the full rated current. It is short lived – a few cycles only.
Inrush currents can be as high as 6 and 18 times the rated
current. Magnitude of inrush current depends on several factors –
e.g.
– Primary voltage
– Transformer saturation curve
– Short circuit capacity of the network – lower the short circuit level, lower
the inrush current
Impact
– Inrush currents are reactive and can cause voltage drops
– Inrush currents do not normally pose any challenge in grid connected
mode as rotary generators are designed to handle these high currents
– However inverters are not designed to carry these. Typically they can
handle up to 2 to 3 times their rated current but not more.
30© 2015 Electric Power Research Institute, Inc. All rights reserved.
Transformer Energizing: Equivalent Circuit
The short-circuit strength of the circuit determines the
magnitude of the inrush current during transformer energizing.
𝑣𝑠 𝑡 = 𝑍𝑠𝑖 𝑡 + 𝑋𝑙𝑘𝑖 𝑡 +𝜕l(𝑖, 𝑡)
𝜕𝑖(𝑡)
𝜕𝑖(𝑡)
𝜕𝑡
In a strong system, 𝑍𝑠 is small. The inrush current 𝑖 𝑡 will be larger.
In a weak system, 𝑍𝑠 is large. The inrush current 𝑖 𝑡 will be smaller.
l(𝑖, 𝑡) = the total magnetic flux linkage
𝑖 𝑡 = inrush current when energized
In differential equation:
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Transformer Core Saturation Characteristics: I-V
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Transformer Energizing: Full-Voltage Energizing
With a Typical Saturation Curve
Transformer is unloaded energized at bus full voltage. Short-
circuit strength is x
1.5 MVA, 12.47 kV/480V, 5.07% (for now - Ygnd Ygnd)
Rated transformer current = 70 Arms = 98 ApkShort-circuit capacity at 12.47 kV bus = 300 MVA Short-circuit capacity at 12.47 kV bus = 30 MVA
4.6x
3.5x
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Transformer Energizing: Full-Voltage Energizing
With a Very Flat Saturation Curve
Transformer is unloaded energized at bus full voltage.
1.5 MVA, 12.47 kV/480V, 5.07% (for now - Ygnd Ygnd)
Rated transformer current = 70 Arms = 98 ApkShort-circuit capacity at 12.47 kV bus = 300 MVA Short-circuit capacity at 12.47 kV bus = 30 MVA
20x
9x
34© 2015 Electric Power Research Institute, Inc. All rights reserved.
Design Analysis
volt
age
time
limits
unacceptableovervoltage
Cu
rren
t
Impedance
Relay desensitization
Wat
ts
Impedance
Load Only
Load and PV
Ener
gy
Time
unserved energy
Energy exceedingnormal
Design Analysis Approach
Load Analysis
Protection & Reliability
DER Sizing & Design
Distribution System Modeling, Simulation & Optimization
Microgrid Controller Architecture & Design
case by case look needed
Location √no impact
Location XPotential risk
• Steady State load flow• System Dynamic• Harmonics• Flicker• Controls• Operation seq.• Fault Current• Black Start
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Data Collection Modeling Impact StudiesCommissioning
& Operation
Microgrid Design Analysis
o Model validation
o Real time ops &
monitoring
o Network models•Load types
•DER types
•Operation
o Protection info
o Scenarios
o Model validation
o Grid impact
o Steady state
o Fault analysis
o Protection
o Stability studies
36© 2015 Electric Power Research Institute, Inc. All rights reserved.
Key interests
• Is the micro grid gen(s) is enough to support the islanded load?
• Verify compliance to planning & voltage stability requirements
Load flow
• Is existing protection adequate?
• If not, try various options
Protection analysis
• Events (loss of large load, load step & fault clearing capabilities)
• Fault Ride Through capabilities of various inverter-based DERs
Dynamic studies
37© 2015 Electric Power Research Institute, Inc. All rights reserved.
Detailed Design Analysis – Tools Source: LBNL Paper LBNL-6708E
Need to apply a consistent modeling
framework
Allow existing models to feed new analysis
PSCAD/EMTP-RV/MATLAB DesignBase
DIGSILENT
PSS/SINCAL
CYMDIST
SynerGEE
Transient Dynamic
Time-Series
Analysis/Slow
Dynamics
Time-Series
Analysis/SS
Steps
Steady State
All
OpenDSS/Grid Lab D/DEW
Microseconds Milliseconds Seconds Minutes Hours Days
A variety of MC capabilities
requires a variety of models to
understand
• Performance
• Grid interaction
• System Protection Scheme
Impact
38© 2015 Electric Power Research Institute, Inc. All rights reserved.
Available Tools
Software Tool Affiliated Org. Tool Type
CYMDIST CYME International T&D Inc. Planning and simulation of distribution networks,
including load flow, short-circuit, and network optimization analysis.
DER-CAM Lawrence Berkeley National Laboratory (LBNL)
Techno-economic tool for microgrid design and operation.
DesignBase Power Analytics Broad platform for electrical system design, simulation, and optimization.
EMTP-RV POWERSYS Solutions Power system transients simulation, load flow, harmonics.
EUROSTAG Tractebel Engineering GDF Suez
Power system dynamics simulation; full range of
transient, mid- and long-term stability; steady-state load flow computation.
GridLAB-D Pacific Northwest National Laboratory (PNNL)
Distribution system simulation and analysis.
HOMER Homer Energy LLC, National
Renewable Energy Laboratory (NREL)
Techno-economic tool for microgrid design and operation.
OpenDSS Electric Power Research Institute (EPRI)
Distribution system simulation and analysis.
PowerFactory DIgSILENT GmbH Power system analysis tool for load flow and
harmonics in transmission, distribution, and industrial networks.
PSCAD Manitoba HVDC Research Center
Power system transient simulation, load flow simulation.
PSS/E Siemens Power Technologies International (Siemens PTI)
Load flow, dynamic analysis, and harmonic analysis of utility and industrial networks.
39© 2015 Electric Power Research Institute, Inc. All rights reserved.
Simulation Tools - Comparison
Power
Flow,
balanced
Power Flow,
unbalanced
Short
Circuit
Relay
Coordination
Arc
Flash
Harmonic
Analysis
Transient
Analysis
Dynamic
Analysis
Quasi Steady-
State Analysis
EMTP-RV,
Simulink,
PSCAD
Aspen, Cape
DesignBase,
PowerFactory
PSLF, PSS/E
OpenDSS
GridLAB-D
Best choice
Can be done, but not preferred choice
Cannot be done
Tool
Study
40© 2015 Electric Power Research Institute, Inc. All rights reserved.
Case # 1:Protection Case Studies
(Mohamed El Khatib)
Renewable Based Microgrids
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Case # 2: Rural Radial Community
(Arindam Maitra)
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Case Study: Two Remote Rural Communities
3.25MW of Load
6.5MW of DG
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One-line diagram of the 34.5-kV
34.5 KVExisting
Recloser
Existing
Recloser 34.5 KV
Plant Load: 5MW
Wind plant : 6.6 MW
Plant Load: 1MW
4.8 KV
Plant Load: 1.8MW
Sync DG:
0.416 MW
R55 R173
Wind Turbine: Type 2 induction generator with rotor resistor control.
This type of turbine needs a stiff transmission grid and a strong synchronous source for stable
operation and can introduce oscillations if it remains connected during islanded operation.
They require external reactive support to maintain voltage, which is typically provided by static
or/and dynamic compensation
44© 2015 Electric Power Research Institute, Inc. All rights reserved.
Case Study: Reliability Assessments In Rural Areas of
New York
Microgrid 1
34.5 KVExisting
Reclosure
Existing
Reclosure
Proposed
PQ Meter
Proposed
Reclosure 34.5 KV
Plant Load: 5MW
Wind plant : 6.6 MW
Plant Load: 1MW
4.8 KV
Plant Load: 1.8MW
Sync DG:
0.416 MW
Proposed
Reclosure
Proposed
2 MWHR Energy
Storage
Proposed
1 MWHR Energy
Storage
Fault Exposure Scenario #1
Microgrid 2
34.5 KVExisting
Reclosure
Existing
Reclosure
Proposed
Reclosure 34.5 KV
Plant Load: 5MW
Wind plant : 6.6 MW
Plant Load: 1MW
Plant Load: 1.8MW
Proposed
Reclosure
Proposed
2 MWHR Energy
Storage
Proposed
1 MWHR Energy
Storage
Fault Exposure Scenario #2
Proposed
PQ Meter
Sync DG:
0.416 MW
4.8 KV
Electricity customers in rural areas
of NY have been experiencing
power outages lasting 10 hours &
longer, which far exceeds the
Customer Average Interruption
Duration Index (CAIDI) targets
Average statewide CAIDI target is
~ 2 hours
This problem is due, in part, to the
fact that many remote areas of
New York State are fed radially
and have only a single
transmission or sub-transmission
supply line that feeds these areas
45© 2015 Electric Power Research Institute, Inc. All rights reserved.
Design Study
Rural electrification in areas with otherwise poor reliability is the key driver to evaluate microgrid as a possible solution
– Many remote communities are situated in locations without a backup transmission or sub-transmission connection
– Restoration time is quite high
– Microgrids can play a role in reducing fault investigation time, shorter outage duration and lower costs for first responders
– Operating remote communities as a microgrid
Complete transition from grid-connected operation to micro-grid operation within 15 minutes following the loss of the supply line
Supply at least 50% of the customers in the Wethersfield and 50% customers in Orangeville area for at least (8) hrs
46© 2015 Electric Power Research Institute, Inc. All rights reserved.
Case Study: Focus Areas
−Define the Modes of Operations – Based on a permanent fault location
on 34.5 kV supply line and system protection requirements, different microgrid
scenarios are identified. Additional equipment or changes in the circuit
configuration to facilitate stable operation of the microgrids is proposed
−System Protection Study – Identify the required enhancements to
protections system for the area under study during microgrid conditions.
− A high-level protection system design (relay types, communication needs, etc.) that
are needed to accommodate normal and microgrid operation
−Fault Location Study – Develop improved fault locating algorithms for a
utility-supplied distribution circuit
− Emphasis was on 34.5 kV line and underlying 4.8 kV system as well to evaluate the
possible local microgrid effects at the 4.8 kV side.
− Develop improved fault locating algorithms in PSCAD
−
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Possible Microgrid Configurations
Microgrid “OW”: both circuits
operate as a unified microgrid
Microgrid “W”: Circuit operates as
a standalone microgrid
Microgrid “O”: Circuit operates as
a standalone microgrid
48© 2015 Electric Power Research Institute, Inc. All rights reserved.
Technical Limitations with Current Protection
Fault Condition # 1:
– Grid Connected Mode:
For a permanent fault between
Attica and Orangeville, recloser
R55 will open. Since R55 is the
only upstream recloser both
circuits with be out of service
Need for local generation
Important to isolate the fault
– EPRI proposes a new recloser
at Exchange St Rd P122. This
will allow Orangeville and
Wethersfield to be served as
microgrid (“OW”) with energy
storage while the fault is being
cleared
Microgrid 1
34.5 KVExisting
Reclosure
Existing
Reclosure
Proposed
PQ Meter
Proposed
Reclosure 34.5 KV
Plant Load: 5MW
Wind plant : 6.6 MW
Plant Load: 1MW
4.8 KV
Plant Load: 1.8MW
Sync DG:
0.416 MW
Proposed
Reclosure
Proposed
2 MWHR Energy
Storage
Proposed
1 MWHR Energy
Storage
Fault Exposure Scenario #1
49© 2015 Electric Power Research Institute, Inc. All rights reserved.
Technical Limitations with Current Protection System
(cont.)
Fault Condition # 2:
– Grid Connected Mode:
Permanent fault between recloser R173 and Wethersfield, recloser R173 will open to save Wetherfield
Isolate the 4.8KV system in Wethersfield to prevent back feed from Wind farm (& Energy storage system proposed as part of the microgrid mode)
In this scenario, Orangeville and Boxler plant remain connected to the Attica substation in “grid-tie” mode.
– EPRI proposes a new recloser at J197/J199. Wethersfield will operate as a standalone microgrid (“W”)
34.5 KVExisting
Reclosure
Existing
Reclosure
Proposed
Reclosure 34.5 KV
Plant Load: 5MW
Wind plant : 6.6 MW
Plant Load: 1MW
Plant Load: 1.8MW
Proposed
Reclosure
Proposed
2 MWHR Energy
Storage
Proposed
1 MWHR Energy
Storage
Fault Exposure Scenario #2
Proposed
PQ Meter
Sync DG:
0.416 MW
4.8 KV
Microgrid W
50© 2015 Electric Power Research Institute, Inc. All rights reserved.
Attica 34.5kV
R55
Boxler Farm
2.5MVA
34.5kV:4.8kV
500kVA
Wind Farm
Wethersfield
Beckwith M-3410A
R122 (new)
R199 (new)
X
storage
battery 1
New relay
Y
storage
battery 2
R173 (Form 6)
3 - set of 3 wye-gnd
connected VTs
3
1 – single VT
11
3
1
Orangeville Tap
51© 2015 Electric Power Research Institute, Inc. All rights reserved.
R55
Boxler Farm
500kVA
Wind Farm
Wethersfield
R122
R199
X
Y
R173
Scenario - permanent fault between R55 and R122
X
Permanent fault occurs here
open
closed
in reclosing
cycle
Orangeville Tap
52© 2015 Electric Power Research Institute, Inc. All rights reserved.
R55
Boxler Farm
500kVA
Wind Farm
Wethersfield
R122
R199
X
Y
R173
Scenario - permanent fault between R55 and R122
X
open
closed
• X and Y opened by 34.5kV voltage protection before first reclose of R55
• R55 in reclosing cycle
in reclosing
cycle
Orangeville Tap
53© 2015 Electric Power Research Institute, Inc. All rights reserved.
R55
Boxler Farm
500kVA
Wind Farm
Wethersfield
R122
R199
X
Y
R173
Scenario - permanent fault between R55 and R122
X
open
closed
• R55 locks out
in reclosing
cycle
Orangeville Tap
54© 2015 Electric Power Research Institute, Inc. All rights reserved.
R55
Boxler Farm
500kVA
Wind Farm
Wethersfield
R122
R199
X
Y
R173
Scenario - permanent fault between R55 and R122
X
open
closed
• R122, R173, and R199 open
in reclosing
cycle
Orangeville Tap
55© 2015 Electric Power Research Institute, Inc. All rights reserved.
R55
Boxler Farm
500kVA
Wind Farm
Wethersfield
R122
R199
X
Y
R173
Scenario - permanent fault between R55 and R122
X
open
closed
• Both battery systems come back online and close X & Y
in reclosing
cycle
Orangeville Tap
56© 2015 Electric Power Research Institute, Inc. All rights reserved.
R55
Boxler Farm
500kVA
Wind Farm
Wethersfield
R122
R199
X
Y
R173
Scenario - permanent fault between R55 and R122
X
open
closed
• R199 will close using hot bus – dead line
in reclosing
cycle
Orangeville Tap
57© 2015 Electric Power Research Institute, Inc. All rights reserved.
R55
Boxler Farm
500kVA
Wind Farm
Wethersfield
R122
R199
X
Y
R173
Scenario - permanent fault between R55 and R122
X
open
closed
• R173 will close using sync-check
• Complete island established
in reclosing
cycle
Orangeville Tap
58© 2015 Electric Power Research Institute, Inc. All rights reserved.
R55
Boxler Farm
500kVA
Wind Farm
Wethersfield
R122
R199
X
Y
R173
Scenario - permanent fault between R55 and R122
open
closed
• Fault is removed and R55 manually closed
in reclosing
cycle
Orangeville Tap
59© 2015 Electric Power Research Institute, Inc. All rights reserved.
R55
Boxler Farm
500kVA
Wind Farm
Wethersfield
R122
R199
X
Y
R173
Scenario - permanent fault between R55 and R122
open
closed
• R122 closes sync-check
• System normal
in reclosing
cycle
Orangeville Tap
60© 2015 Electric Power Research Institute, Inc. All rights reserved.
Recommendations - Protections
• 34.5kV protection and control of micro grid scheme is voltage based
• Voltage protection disconnects energy storage batteries prior to entering
microgrid operation
• Voltage protection detects and clears 34.5kV faults that occur during microgrid
operation
• Ferroresonance suppression is prudent for 34.5kV wye-grounded VTs
as well as using VTs with high saturation knee point (e.g. 2.0 per unit)
• Low voltage current based protection (e.g. 4.8kV feeders) will have to be
evaluated based on energy storage devices capability to source fault current
or alternative protection should be investigated – not addressed in this section
• Setting and reclosing setting changes needed on R55 and R173 as well as the
additional protection & control described in this section for microgrid operation
61© 2015 Electric Power Research Institute, Inc. All rights reserved.
Proposed Protection, Monitoring, & Control
Modifications
1.12 mi
AtticaSTA. 12
34.5 kV
Attica PrisonSTA.
Orangeville STA. 1934.5 kV
R55
J192
Boxler Farm480V, 416 kW
6.3 mi 0.2 mi 6.1 mi Vestas TAP34.5 kV
0.1
mi
Wethersfield STA. 23 34.5 kV
R122 R173
R1
99
4.0
mi
PQ48V
PQ48B
WNY Wind Corp. 6.6 MW
Thevenin equivalent source for
Attica substation
Orangeville STA. 194.8 kV
Wethersfield STA. 23 4.8 kV
Attica Prison
Wethersfield 4.8-kV circuit and load
Orangeville 4.8-kV circuit and load
Boxler DG4.8 kV
62© 2015 Electric Power Research Institute, Inc. All rights reserved.
34.5 KVExisting
recloser
Existing
recloser
Proposed
PQ Meter
Proposed
recloser 34.5 KV
Plant Load: 5MW
Wind plant : 6.6 MW
Plant Load: 1MW
4.8 KV
Plant Load: 1.8MW
Sync DG:
0.416 MW
Proposed
recloser
Proposed
2 MWHR Energy
Storage
Proposed
1 MWHR Energy
Storage
Microgrid OW –
Orangeville & Wethersfield
Proposed System Level Modifications – Energy Storage
System
• 2 Separate ES systems proposed.
− Closer to the Loads at Orangville and Wethersfield
− Valid for independent operations of Orangville and
Wethersfield
− Smaller Systems are more reliable
63© 2015 Electric Power Research Institute, Inc. All rights reserved.
Fault Location Analysis
Number of
events
Monitor Samples/cycle Voltage level Actual Fault
location
Circuit
model
Data useful for
fault location
12 R55 4 34.5 kV Unknown ASPEN
OneLiner
Yes
10 R173 16 Limited
1.12 mi
AtticaSTA. 12
34.5 kV
Attica PrisonSTA.
Orangeville STA. 1934.5 kV
R55
J192
Boxler Farm480V, 416 kW
6.3 mi 0.2 mi 6.1 mi Vestas TAP34.5 kV
0.1
mi
Wethersfield STA. 23 34.5 kV
R122 R173
R1
99
4.0
mi
PQ48V
PQ48B
WNY Wind Corp. 6.6 MW
Thevenin equivalent source for
Attica substation
Orangeville STA. 194.8 kV
Wethersfield STA. 23 4.8 kV
Attica Prison
Wethersfield 4.8-kV circuit and load
Orangeville 4.8-kV circuit and load
SEL PG10Cooper Form
Type 6
64© 2015 Electric Power Research Institute, Inc. All rights reserved.
Line Exposed to Faults in Grid Connected Mode
Scenario G1: Multiple single line-to-ground faults applied in Line Section 1, between reclosers R55 and R122
Scenario G2: Multiple single line-to-ground faults applied in Line Section 2, between reclosers R173 and R199
Scenario G3: Multiple line-to-line faults applied in Line Section 3, between PQ48V and PQ48B
1.2 mi
AtticaSTA. 12
34.5 kV
Attica PrisonSTA.
Orangeville STA. 1934.5 kV
R55
J192
Boxler Farm480V, 416 kW
6.3 mi 0.2 mi 6.1 mi Vestas TAP34.5 kV
0.1
mi
Wethersfield STA. 23 34.5 kV
R122 R173
R1
99
4.0
mi
PQ48V
PQ48B
WNY Wind Corp. 6.6 MW
Thevenin equivalent source for
Attica substation
Orangeville STA. 194.8 kV
Wethersfield STA. 23 4.8 kV
Attica Prison
Wethersfield 4.8-kV circuit and load
Orangeville 4.8-kV circuit and load
Boxler DG4.8 kV
L i n e S e c t i o n 1 L i n e S e c t i o n 2
Line
Section
3
65© 2015 Electric Power Research Institute, Inc. All rights reserved.
Line Exposed to Faults in Microgrid Operation
Scenario OW1: Multiple line-to-line faults applied in Line Section 2, between reclosers R173 and R199 (in
Microgrid OW operation)
Scenario OW2: Multiple line-to-line faults applied in Line Section 3, between PQ48V and PQ48B (in Microgrid
OW operation)
Scenario O1: Multiple line-to-line faults applied in Line Section 3, between PQ48V and PQ48B (in Microgrid O
operation)
“Microgrid O”“Microgrid OW”
Line Sectio
n 3
Orangeville STA. 1934.5 kV
J192
Boxler Farm480V, 416 kW
0.2 mi 6.1 mi Vestas TAP34.5 kV
0.1
mi
R122 R173
4.0
mi
PQ48V
PQ48B
Orangeville STA. 194.8 kV
Orangeville 4.8-kV circuit and load
Boxler DG4.8 kV
OrangevilleEnergy Storage
Wethersfield STA. 23 34.5 kV
R1
99
Wethersfield STA. 23 4.8 kV
Wethersfield 4.8-kV circuit and load Wethersfield
Energy Storage
L i n e S e c t i o n 2
Line Sectio
n 3
Boxler Farm480V, 416 kW
4.0
mi
PQ48V
PQ48B
Orangeville STA. 194.8 kV
Orangeville 4.8-kV circuit and load
Boxler DG4.8 kV
OrangevilleEnergy Storage
66© 2015 Electric Power Research Institute, Inc. All rights reserved.
Fault Location Algorithms Applied in “Grid Connected” Mode
1.12 mi
AtticaSTA. 12
34.5 kV
Attica PrisonSTA.
Orangeville STA. 1934.5 kV
R55
J192
Boxler Farm480V, 416 kW
6.3 mi 0.2 mi 6.1 mi Vestas TAP34.5 kV
0.1
mi
Wethersfield STA. 23 34.5 kV
R122 R173R
19
9
4.0
mi
PQ48V
PQ48B
WNY Wind Corp. 6.6 MW
Thevenin equivalent source for
Attica substation
Orangeville STA. 194.8 kV
Wethersfield STA. 23 4.8 kV
Attica Prison
Wethersfield 4.8-kV circuit and load
Orangeville 4.8-kV circuit and load
Line Section 1 Line Section 2
Lin
e S
ec
tio
n 3
Scenario Algorithms to be Applied during SLG Faults
Line Section 1 One-ended methods (R55) Simple reactance, Takagi, Novosel et al.
Two-ended method (R55, R122) Two-terminal negative-sequence
Line Section 2 One-ended methods (R173) Simple reactance, Takagi, Novosel et al.
Line Section 3 One-ended methods (PQ48B) Simple reactance, Takagi, Eriksson
Two-ended methods (PQ48B, PQ48V) Two-terminal negative-sequence
67© 2015 Electric Power Research Institute, Inc. All rights reserved.
Case # 3: Secondary Network
(Arindam Maitra)
68© 2015 Electric Power Research Institute, Inc. All rights reserved.
Case Study #3: Secondary Network
Models developed in
OpenDSS, EMTP-RV, &
Power Factory
Microgeneration types: CHP
behind inverter and PV
Scenario tested: Small-scale
Distributed CHP units (small
synchronous machine
behind an inverter) + small
scale PV
69© 2015 Electric Power Research Institute, Inc. All rights reserved.
One Line Diagram
70© 2015 Electric Power Research Institute, Inc. All rights reserved.
Scenarios
1. Small-scale Distributed CHP units
(small synchronous machine behind
an inverter) + small scale PV
2. Small-scale Distributed CHP units
(small synchronous machine behind
an inverter) + small scale PV +
small scale distributed storage
3. Large-scale Central CHP unit (large
synchronous machine) + small
scale PV
4. Large-scale Central CHP unit (large
synchronous machine) + small
scale PV + Large-scale central
storage
5. 100% Large CHP unit (large
synchronous machine)
6. 100% Large CHP unit (large
synchronous machine behind an
inverter)
VS8360(44X_VS8360)
10
38
4(4
4X
_1
03
84
) M1049(44X_M1049)
BLDG 7(5917.44X_10384)
kVA = 314.794
M1047(44X_M1047)
10385(44X_10385)
BLDG 5(5829.44X_10385)
kVA = 182.114
M1
04
8(4
4X
_M
10
48
)
BLDG 6(5877.44X_M1048)
kVA = 222.239
BC3998(44X_BC3998)
VS4007(44X_VS4007)
VS3998(44X_VS3998)
0.05 MVA 0.05 MVA 0.05 MVA
0.025 MVA
303 Vernon Ave(5916.44X_BC3998)
kVA = 310.728
0.025 MVA
303 Vernon Ave(5766.44X_BC3998)
kVA = 140.5
0.3 MVA 0.3 MVA 0.3 MVA
0.15 MVA 0.15 MVA
Inverter
Inv
ert
er
Inverter Inverter
Inv
erte
r
Inverter Inverter Inverter
Inv
ert
er In
ve
rter
71© 2015 Electric Power Research Institute, Inc. All rights reserved.
Assumptions
The LV system is solidly grounded via a dedicated ground link at:
– Distribution supply transformer LV (transformers are Delta-Wye, directly
connected to ground on the secondary side)
– Each LV generator (generators are Y connected to ground)
– LV network protection vaults
System impedance to ground is maintained at less than 5 ohms
as specified by Client
The DERs are assumed:
– 3-phase YN connected and the neutral is solidly grounded
– Provide up to 1.8 per unit fault current
– Can sustainably provide fault current, including earth fault current until
fault is cleared or isolated
72© 2015 Electric Power Research Institute, Inc. All rights reserved.
General philosophy used
Determine the required level of selectivity for different fault scenarios. Generally, this
can be determined by considering the impact to the customers for different grid faults.
Group parallel cables connecting common LV nodes together into single ’branches’
Split the Microgrid into separate regions/zones which with appropriate protection
grading will achieve the desired selectivity.
Ensure LV grid relays protecting branches directly connected to customers trip first to
remove the fault from the remaining healthy grid as quickly as possible
Ensure some time delay between tripping of customer branches and any
interconnector circuits connecting together main LV nodes
Ensure customer relays trip last to ensure healthy generation remains in service post
fault
73© 2015 Electric Power Research Institute, Inc. All rights reserved.
High selectivity protection zones
74© 2015 Electric Power Research Institute, Inc. All rights reserved.
Grid Connected Mode – Summer Peak Steady
State Branch Currents and Bus Voltages
74
Line IDFrom
BusTo Bus
Current
(A)
Loading
(%)
sec_6643_1
10385 M1047
143 17%
sec_6643_2 143 17%
sec_6644_1 159 20%
sec_6644_2 159 20%
sec_6645_1
M1047 M1048
129 16%
sec_6645_2 129 16%
sec_6646_1 115 14%
sec_6646_2 115 14%
sec_6646_3 115 14%
sec_6649_1
M1048 10384
213 25%
sec_6649_2 213 25%
sec_6650_1 239 29%
sec_6651_1 M1049 10384 0 0%
sec_6751_1
M1048BC399
8
249 29%
sec_6751_2 249 29%
sec_6751_3 249 29%
sec_6751_4 249 29%
sec_6754_1
VS8360 M1048
244 29%
sec_6754_2 244 29%
sec_6754_3 244 29%
sec_6754_4 244 29%
Bus IDPhase A
(pu)
Phase B
(pu)
Phase C
(pu)
M1048 0.98 0.98 0.98
10384 0.96 0.96 0.96
10385 0.97 0.97 0.97
BC3998 0.99 0.99 0.99
M1049 0.96 0.96 0.96
M1047 0.97 0.97 0.97
VS8360 0.98 0.98 0.98
VS4007 0.99 0.99 0.99
VS3998 0.99 0.99 0.99
75© 2015 Electric Power Research Institute, Inc. All rights reserved.
Summer Peak Steady State and Fault Induced Bus Voltages –
Grid Connected & Islanded
75
Bus ID
Summer Load Fault @ 10384 Fault @ BC3998 Fault @ M1048
Phase
A
Phase
B
Phase
C
Phase
A
Phase
B
Phase
C
Phase
A
Phase
B
Phase
C
Phase
A
Phase
B
Phase
C
M1048 1.00 1.00 1.00 0.13 0.13 0.13 0.05 0.05 0.05 0.00 0.00 0.00
10384 1.00 1.00 1.00 0.00 0.00 0.00 0.09 0.09 0.09 0.05 0.05 0.05
10385 1.01 1.01 1.01 0.15 0.15 0.15 0.07 0.07 0.07 0.03 0.03 0.03
BC3998 1.00 1.00 1.00 0.14 0.14 0.14 0.00 0.00 0.00 0.02 0.02 0.02
M1047 1.00 1.00 1.00 0.14 0.14 0.14 0.06 0.06 0.06 0.01 0.01 0.01
VS8360 1.00 1.00 1.00 0.13 0.13 0.13 0.05 0.05 0.05 0.00 0.00 0.00
VS4007 1.00 1.00 1.00 0.14 0.14 0.14 0.00 0.00 0.00 0.02 0.02 0.02
VS3998 1.00 1.00 1.00 0.14 0.14 0.14 0.00 0.00 0.00 0.02 0.02 0.02
Bus ID
Summer Load Fault @ 10384 Fault @ BC3998 Fault @ M1048
Phase
A
Phase
B
Phase
C
Phase
A
Phase
B
Phase
C
Phase
A
Phase
B
Phase
C
Phase
A
Phas
e B
Phas
e C
M1048 0.98 0.98 0.98 0.69 0.69 0.69 0.37 0.37 0.37 0.00 0.00 0.00
10384 0.98 0.98 0.98 0.00 0.00 0.00 0.66 0.66 0.66 0.47 0.47 0.47
10385 0.99 0.99 0.99 0.79 0.79 0.79 0.59 0.59 0.59 0.35 0.35 0.35
BC3998 0.98 0.98 0.98 0.79 0.79 0.79 0.00 0.00 0.00 0.32 0.32 0.32
M1047 0.99 0.99 0.99 0.74 0.74 0.74 0.48 0.48 0.48 0.17 0.17 0.17
VS8360 0.99 0.99 0.99 0.73 0.73 0.73 0.46 0.46 0.46 0.14 0.14 0.14
VS4007 0.99 0.99 0.99 0.86 0.86 0.86 0.33 0.33 0.33 0.55 0.55 0.55
VS3998 0.99 0.99 0.99 0.80 0.80 0.80 0.04 0.04 0.04 0.35 0.35 0.35
When islanded
the bus voltages
are close to zero
and inadequate
for fault location
determination
In grid connected
mode the bus
voltages of un-
faulted buses are
non-zero
76© 2015 Electric Power Research Institute, Inc. All rights reserved.
Changes from Grid Connected Mode to Islanded Mode in
Summer Peak Steady State and Fault Induced Phase A Branch
Currents
Line ID From Bus To BusSummer
LoadFault @ 10384
Fault @
BC3998Fault @ M1048
sec_6643_1
10385 M1047
78% -75% -87% -92%
sec_6643_2 78% -75% -87% -92%
sec_6644_1 78% -75% -87% -92%
sec_6644_2 78% -75% -87% -92%
sec_6645_1
M1047 M1048
78% -75% -87% -92%
sec_6645_2 78% -75% -87% -92%
sec_6646_1 78% -75% -87% -92%
sec_6646_2 78% -75% -87% -92%
sec_6646_3 78% -75% -87% -92%
sec_6649_1
M1048 10384
-31% -82% -85% -90%
sec_6649_2 -31% -82% -85% -90%
sec_6650_1 -31% -82% -85% -90%
sec_6751_1
M1048 BC3998
279% -86% -88% -95%
sec_6751_2 279% -86% -88% -95%
sec_6751_3 279% -86% -88% -95%
sec_6751_4 279% -86% -88% -95%
Total Fault Current at the Fault Location (%) -89% -93% -93%
When islanded
line loading
increases for
most line
sections
When islanded
fault currents
decrease for all
3-phase faults
77© 2015 Electric Power Research Institute, Inc. All rights reserved.
Modeling Existing Protection
Used representative curves Curve in power factory
Typical TCC for a
current-limiting fuse
78© 2015 Electric Power Research Institute, Inc. All rights reserved.
Findings and recommendations: Current-Limiting Protection
Normally the Current limiter (CL) fuse will “melt” when the
current in the fuse element exceeds the current specified by
the fuse’s melt characteristic.
No enough fault currents from the inverter based gens;
hence there is no compliance to protection standards and
performance metrics during island mode
Clearly, this type of protection in utilizing current limiters isn’t
sufficient
Another set of protection strategies need to be adopted
79© 2015 Electric Power Research Institute, Inc. All rights reserved.
Small-scale Distributed CHP units (small
synchronous machine behind an inverter) + small
scale PV
79
• The overcurrent modules and circuit breakers tip-times
depend on the fault-current amplitude
• The appropriate directional modules were set to trip
slightly after the overcurrent models
Circuit breakers
Directional-
Overcurrent
80© 2015 Electric Power Research Institute, Inc. All rights reserved.
3 Phase Fault @ 10384
80
81© 2015 Electric Power Research Institute, Inc. All rights reserved.
3 Phase Fault @ 10384
81
1. D/O module between 10384 and M1048 trips on overcurrent
2. Circuit breaker at 10384 PCC trips on overcurrent
1
2
82© 2015 Electric Power Research Institute, Inc. All rights reserved.
3 Phase Fault @ 10384
82
Isolated
Loads and generators at bus 10384 are
isolated
83© 2015 Electric Power Research Institute, Inc. All rights reserved.
3 Phase Fault @ 10384
83
After fault is cleared bus voltages
recover to normal values
84© 2015 Electric Power Research Institute, Inc. All rights reserved.
1 Phase Fault @ 10384
84
85© 2015 Electric Power Research Institute, Inc. All rights reserved.
1 Phase Fault @ 10384
85
1. D/O module between 10384 and M1048 trips on overcurrent
2. Circuit breaker at 10384 PCC trips on overcurrent
1
2
86© 2015 Electric Power Research Institute, Inc. All rights reserved.
1 Phase Fault @ 10384
86
Isolated
Loads and generators at bus 10384 are
isolated
87© 2015 Electric Power Research Institute, Inc. All rights reserved.
1 Phase Fault @ 10384
87
After fault is cleared bus voltages
recover to normal values
88© 2015 Electric Power Research Institute, Inc. All rights reserved.
1 Phase Fault (46.6 mΩ) @ 10384
88
89© 2015 Electric Power Research Institute, Inc. All rights reserved.
1 Phase Fault (46.6 mΩ) @ 10384
89
1. D/O module between 10384 and M1048 trips on overcurrent
2. Circuit breaker at 10384 PCC trips on overcurrent
1
2
90© 2015 Electric Power Research Institute, Inc. All rights reserved.
1 Phase Fault (46.6 mΩ) @ 10384
90
Isolated
Loads and generators at bus 10384 are
isolated
91© 2015 Electric Power Research Institute, Inc. All rights reserved.
1 Phase Fault (46.6 mΩ) @ 10384
91
After fault is cleared bus voltages
recover to normal values
92© 2015 Electric Power Research Institute, Inc. All rights reserved.
Phase-Phase Fault @ 10384
92
93© 2015 Electric Power Research Institute, Inc. All rights reserved.
Phase-Phase Fault @ 10384
93
1. D/O module between 10384 and M1048 trips on overcurrent
2. Circuit breaker at 10384 PCC trips on overcurrent
2
1
94© 2015 Electric Power Research Institute, Inc. All rights reserved.
Phase-Phase Fault @ 10384
94
Isolated
Loads and generators at bus 10384 are
isolated
95© 2015 Electric Power Research Institute, Inc. All rights reserved.
Phase-Phase Fault @ 10384
95
After fault is cleared bus voltages
recover to normal values
96© 2015 Electric Power Research Institute, Inc. All rights reserved.
Phase-Phase-Ground Fault @ 10384
96
97© 2015 Electric Power Research Institute, Inc. All rights reserved.
Phase-Phase-Ground Fault @ 10384
97
1. D/O module between 10384 and M1048 trips on overcurrent
2. Circuit breaker at 10384 PCC trips on overcurrent
2
1
98© 2015 Electric Power Research Institute, Inc. All rights reserved.
Phase-Phase-Ground Fault @ 10384
98
Isolated
Loads and generators at bus 10384 are
isolated
99© 2015 Electric Power Research Institute, Inc. All rights reserved.
Phase-Phase-Ground Fault @ 10384
99
After fault is cleared bus voltages
recover to normal values
100© 2015 Electric Power Research Institute, Inc. All rights reserved.
3 Phase Fault @ M1048
100
101© 2015 Electric Power Research Institute, Inc. All rights reserved.
3 Phase Fault @ M1048
101
1. D/O module between 10384 and M1048 trips on directional
2. D/O module between BC3998 and M1048 trips on directional
3. D/O module between M1047 and M1048 trips on overcurrent
4. Circuit breaker at M1048 PCC trips on overcurrent
1
2
3
4
102© 2015 Electric Power Research Institute, Inc. All rights reserved.
3 Phase Fault @ M1048
102
Isolated
Loads and generators at all buses are
isolated
Isolated Isolated
Isolated
103© 2015 Electric Power Research Institute, Inc. All rights reserved.
3 Phase Fault @ M1048
103
After fault is cleared bus voltages:
1. at 10385 and M1048 are elevated
2. at BC3998 are bellow normal
values
3. at 10384 recover to normal values
104© 2015 Electric Power Research Institute, Inc. All rights reserved.
3 Phase Fault @ BC3998
104
105© 2015 Electric Power Research Institute, Inc. All rights reserved.
3 Phase Fault @ BC3998
105
1. D/O module between BC3998 and M1048 trips on
overcurrent
2. Circuit breaker at BC3998 PCC trips on
overcurrent
1
2
106© 2015 Electric Power Research Institute, Inc. All rights reserved.
3 Phase Fault @ BC3998
106
Loads and generators at bus BC3998
are isolated
Isolated
107© 2015 Electric Power Research Institute, Inc. All rights reserved.
3 Phase Fault @ BC3998
107
After fault is cleared bus voltages:
1. at 10384, 10385 and M1048 are
elevated
2. at BC3998 are bellow normal
values
108© 2015 Electric Power Research Institute, Inc. All rights reserved.
3 Phase Fault @ 10385
108
109© 2015 Electric Power Research Institute, Inc. All rights reserved.
3 Phase Fault @ 10385
109
1. D/O module between 10385 and M1048 trips on
directional
2. Circuit breaker at 10384 PCC trips on overcurrent
1
2
110© 2015 Electric Power Research Institute, Inc. All rights reserved.
3 Phase Fault @ 10385
110
Loads and generators at bus 10385 are
isolated
Isolated
111© 2015 Electric Power Research Institute, Inc. All rights reserved.
3 Phase Fault @ 10385
111
After fault is cleared bus voltages:
1. at 10385 are elevated
2. at 10384, M1048, and BC3998 are
bellow normal values
112© 2015 Electric Power Research Institute, Inc. All rights reserved.
Summary
“Microgrids” brings many technical needs: Good PSA tools available
No one-size fits all protection scheme works for all microgrids
Action planContinue testing various protection schemes
Level of dynamic studies details depends on so many
factors i.e. gen types, operation philosophy etc.
Best protection scheme depends on microgrid objective
• Network
• Objective
• Scenarios
• Modeling
Grid requirements
Controllability
Monitoring
Reliability
113© 2015 Electric Power Research Institute, Inc. All rights reserved.
Together…Shaping the Future of Electricity