generation transmission distribution...
TRANSCRIPT
“Smart Grid “ – Where We Are Today?
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Meliha B. Selak, P. Eng.IEEE PES DLP [email protected]
2014 IEEE ISGT‐Asia, Kuala Lumpur ‐ 22nd May 2014
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Generation
Transmission
Distribution
Load
Power System Transmission
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P1 P2
Vr 0
L2L1
PtVs
For power balanceP1+P2=L1+L2
For power flowPt = P1‐L1 = L2‐P2 Vs x Vr x Sin(q)
XL
Power Transfer
• Electrical Behavior of Transmission Line‐[dV/dx]=[Z][I] ‐[dI/dx] = jω[C][V]
• Series impedance matrix [Z]
ikik
iiciiii
LjZLjRZ
LjRZ
)()(
Transmission Line Model
jba
P
rhL
i
ioii
2ln
2
jdcdDL
ik
ikoik
'
ln2
j o
oP
Transmission Line Inductance
.)(,)()(Z
,2
ii
'
ikikik
iiii
c
ii
c
ii
o
o
ik
ik
i
i
cii
LRcjdjdcjZLjRajbRjbajR
Ddrhf
fR
a.c. resistance of conductor i,
angular frequency,
frequency in Hz,
average height above ground of conductor i,
radius of conductor i,
direct distance between conductors i and k,
distance between conductor i and image
at complex depth of conductor k,
earth resistivity,
earth permeability.
Formula Quantities
Building Complex Power Systems
• Power system is very complex and is built to satisfy increasing demand of electrical power supply
• The trend in electric power production is toward an interconnected network of transmission lines linking generators and load into large integrated system
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Power System Operation
• Operation of an electrical power systems involves continues electromechanical and electromagnetic distribution of energy.
• During normal operation the system behavior is presented by voltage and current pasors in frequency domain.
• During system disturbances the circuit components have higher stress, resulting in excessive currents or voltage variations that cause power system transients.
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Power System Studies
• Steady State Study• Dynamic State Simulation• Transient Simulation
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• Steady StateShort Circuit Fault LevelEquipment Selection (isolation level) Reference for Protection Settings
• Dynamic State SimulationSpeed of the fault clearing time
• Transients SimulationTripping Priority regarding to:
Overvoltage's conditions and Power Quality (harmonics)
Simulations Outputs
Power System Disturbances and Faults• Inadequate supply equipment
Result of inadequate planning or unexpected rapid load demand Exceeding supply capability results in load losses
• Many blackouts caused by operating systems too close to stability limits
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Protection Duties13
• Protection system or relay must detect the fault and signal circuit breaker to isolate the fault reliably and as fast as possible.
Relaying Fundamentals
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Example reaches and time coordination15
Stepped Distance16
• Note: NOT communications assisted, but good background for other schemes
Z1aZ1b
Z2a
Z2b
Adding large generating units
• With adding large generating units of high capacity to the power grid endangers the normal operation of power system and might lead to outages and system collapse.
• The convention power system protection schemes, designed to detect the fault and signal circuit breaker to isolate the fault reliably and as fast as possible, but cannot prevent from the system collapse.
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Telecommunications infrastructure
Nowadays, the modernized networks and telecommunications infrastructure together with Intelligent Electronic Devices (IED), and allow optimizing the existing electrical power system operation.
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Intelligent Electronic Devices (IED)
IEDs which are used now widely for Power System Protection allow us an implementation of almost all the functionalities needed to protect and control the power system components more efficiently:
• Fundamental protections (Over Current, Over Voltage, Over Frequency, Distance, Differential Protections)
• Breaker Failure protection (BFPN)• Autoreclose (AR)• Automatic switching of protection settings • Overload protection• Wide area special protection schemes (SPS) or remedial action scheme (RAS)• Synchronized Phasor Measurement
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Wide area special protection schemesWide area special protection schemes (SPS) or remedial action scheme (RAS) are designed to detect the system conditions that can cause
• instability• overload
• voltage collapse
• Prevent propagation of disturbances for severe system emergencies caused by un‐planned operating conditions
• Last line of defense to improve system security and prevent disturbance propagation ‐ Could help better utilize system margins
• Stabilize System for Equipment Outages, N‐2 or beyond
• Initiate pre‐planned separation of the power system
• Prevent overloading of the lines
• Arrest voltage decline
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Synchronized Phasor Measurement
Two key elements of synchronized phasor measurement are • data that are provided• how that data are referenced
Synchronized phasor measurement system requires a high-precision timing reference (Global Positioning Satellite Clock system) to synchronize all devises across a system-now available from monitors called phasor measurement units (PMUs)
Voltage waveforms from remote measurement units are compared on real-time basis. This capability is used to:
• evaluate system conditions• compered them to the system model• facilitates analysis in system-wide disturbances• system operation• control• generation dispatch
Permissive Overreaching Transfer Trip
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Sending Permissive Trip = “fault is in front of me” Received Permissive Trip + local Zone 2 = local trip
Z1aZ1b
Z2a
Z2b
Why communication assisted line protection?
• Speed, speed, speed…• Selectivity problem (ie: is the fault between the two
ends of the line?)• Adding communications allows cooperation between
both line terminals, which improves speed by improving selectivity
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Distribution system is designed to serve radial load. (Power flows from higher voltage levels down to customers)
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Power Distribution System
Distribution Protection25
• Relay characteristics are plotted on a time current characteristic (TCC) diagram.
• Non directional protection is needed because of radial system configuration
G GGeneration
Transmission
DistributionLoads
Demand
Traditional one-way supply system
G
Generation
G
Bi-directional supply system
Supply
Generation
Generation
Transmission
Distribution
Loads
Interconnections
Electrical Power System Today
Concerns related to the distribution system operation and planning
With DG increases, Distribution Systems are becoming more like transmission system:
• double or multiple feed circuits having significant changes in operation will have to accommodate bi‐directional power flows
• safety of public and equipmentas the network was not designed to accommodate larger numbers of DG
• protection system becomes more complex due to changes in system behavior and power flow under short‐circuit conditions
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Need for directional protection
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1 3 42
F1R1 faster than R2
F2R2 faster than R1
Distribution Systems Today
Today, the power distribution systems are designed to provide participating customers a new level of choice and control over their energy use through advanced technology, with the goals of empowering customers to:
• save energy• increasing electric service reliability• improving response to power outages.
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Distribution Systems Today
• Advanced communications technologies• Smart meters• Devices for electrical system automation• Energy management tools
ALL provide the significant benefits for energy customers.
The new global communications platforms support the future innovation:• wide and local area networks• telecommunications services• voice services• video conferencing
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