Transcript Cascading Outage in Power System

DETECTION OF MAJOR DISTURBANCES AND
OPTIMIZATION OF TRANSMISSION LINE
PROTECTIVE RELAYING OPERATIONS USING
NEURAL NETWORKS
CESAR RINCON
LOUISIANA STATE UNIVERSITY
Outline
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Introduction
Background
Proposed Solutions
Detailed Algorithm and Data Needed
Next Step
Discuss
Several major blackouts worldwide
Introduction
• Cascading outages:
– Catastrophic economic and social impacts
– Lots of them occurred recently
– Increased research interests due to the lack of
effective analysis tools
• Objectives
– To understand the phenomenon
– To develop and apply new techniques and tools
US Northeastern 1965
Cascading outage case study
Aug 14, 2003 Northeastern Blackout Example
• Stage 1: slow steady state progress
12-14:14pm, several lines and 1 gen outage;
15:05-15:41pm, 3 FE 345KV lines outage;
15:39-15:59pm, collapse of 138KV system;
Load shedding of 1000MW at 15:41pm or 1500MW at 16:05pm could
have prevented the blackout
16:05pm, trigger event: outage of Sammis-Star line;
16:05-16:09pm, 2 345KV & 138KV lines outages;
• Stage 2: fast transient progress
16:09-16:10pm, multiple power plants tripped;
16:10-16:13pm, fully cascade in neighboring areas
Cascade Sequence
1) 4:06
2) 4:08:57
3) 4:10:37
4) 4:10:38.6
Cascade Sequence (cont.)
5) 4:10:39
6) 4:10:44
7) 4:10:45
8) 4:13
Interaction between system-wide and local levels
• Local disturbances to system security
– 12-14:14pm, Reduced security although secure
– 15:05-15:41pm, 3 line outages, “N-1” insecure
• System security to local disturbances
– 15:39-15:59pm, collapse of 138-KV system
– 16:05pm, Sammis-Star outage due to overload and low voltage
• Local disturbances to system security
– Sammis-Star outage triggered cascading outage
• Possible good interactions
– Load shedding at 15:41pm or 16:05pm
– Backup relay not trip at power swing and overload, give time to other
controllers and system operators
Outline
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Introduction
Background
Proposed Solutions
Detailed Algorithm and Data Needed
Next Step
Discuss
Background
Typical Cascading Blackout
Triggering
Events
Typical
Characteristics
Blackout
Faults Happened
Frequency Change
Protection Relay
Operations
Power Swing
Impacts
On System
Trip Lines
Overload...
System Isolated
Trip Generators
Generator Reject
Trip Transformers
Voltage Collapse
Trip Loads...
Load Shed...
Causes
Non-technical factors:
• Change in operating procedures due to deregulation
• Aging infrastructure and lack of investment while the
stress on the system is increased
• Inadequate personnel training for new operating
conditions
Conclusion:
• More investment and better tools are needed
Causes (cont.)
Technical factors:
• Reduced operating margins
• Increased system complexity
• More difficult protection setting coordination
• Inadequate traditional security analysis
• Lack of understanding of the cascades and availability of
effective support tools
Conclusion:
• Understanding and preventing cascades is a challenging
problem
Relay Operations
Problems:
Relay operation is a major contributing factor. So
monitoring relay operation and extracting information
are very important. Only aiming at relay behaviors
under the situation when multi-events (frequency
change, voltage change…) happened simultaneously.
• Dependability
• Security
Background
Impacts:
• Local Level
Relay operations can be assessed by real time
monitoring tool;
Fault analysis and classification tool can also be
implemented;
• System Level
Improve situational awareness of system operator
under dynamic disturbance situation;
Provide reference of decision-making for system
operator under emergent situation
Cascading Blackouts vs Time
Preconditions
Triggering
Events
Slow
Progression
Fast
Progression
Final
Blackout
t
Prevent blackout by acting
as early as possible
The slow pace in the
Initial stages allows the
time for remedial actions
An Example: Tripped elements vs time
(from Aug. 14, 2003 blackout final report)
Outline
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Introduction
Background
Proposed Solutions
Detailed Algorithm and Data Needed
Next Step
Discuss
Our Solution:
Local
Algorithm
Interaction between Locallevel and System-level
System
Algorithm
System Algorithm
System Monitoring
and Control
Local Monitoring
and Control
System Status
Real-time Fault Analysis
Security Analysis
Local Monitoring
Routine-based
Event-based
Synchronized Sampling
Disturbance Report
Security Control
Relay Operation Monitoring
Steady-State
Transient Stability
Measurements
Neural Network
Control
Event Tree Analysis
Measurements
Power System and Protection System
Control
Use of Local Information at the System
Level
• Know exact local disturbance information in real-time
• Obtain local diagnostic support and predict future events (i.e.,
line overload, relay misoperation)
• Make better control decision based on correct local
information
• Evaluate system security and take actions to preserve it
Benefits: Help operators have good situational awareness
Provide operators with decision-making support
Use of System Information at the Local Level
• Identify threatening contingencies
• Identify vulnerable parts (lines and relays) and initiate local
tool for careful monitoring
• Block relay misoperation during extreme conditions or make
correction after system-wide analysis
• Find and store emergency control means ready for expected
contingencies
• Find emergency control means for real time unexpected
events
Benefits: Effective interaction between system and local
actions and operator decision making support
Interactive scheme procedures
Step 1: Routine security analysis performed by the system tool: (a) decides
security level and finds vulnerable elements, then sends monitoring command
to the local tool; (b) identifies critical contingencies, and starts associated
control schemes to find the control means for those expected events.
Step 2: Local monitoring performed by the local tool: (a) starts analysis when
disturbance occurs; (b) if it finds relay misoperation, it makes correction or
receives system control command for better control; (c) reports disturbance
information and analysis result to the system tool.
Step 3: Event-based security analysis performed by the system tool: (a) if it finds a
match with expected event, activates the emergency control; (b) if it does not
find a match, analyzes if the system is secure or not; (c) if it is not, finds new
emergency control and activates it.
Step 4: Update information and go to Step 1.
Graphic Demonstration
System Level
Routine-based
Security Analysis
System Status
& Monitoring
command
Substation Level
Local
Monitoring Tool
Substation 1
Candidate
control means
Expected
Selected
control means
Unexpected
Event-based
Security Analysis
Disturbance
Report
Local
Monitoring Tool
Substation 2
Local
Monitoring Tool
Substation n
Outline
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Introduction
Background
Proposed Solutions
Detailed Algorithm and Data Needed
Next Step
Discuss
System Monitoring and Control
System-wide monitoring and control
Steady state control scheme
Steady state control scheme (cont.)
• Evaluation by vulnerability index (VI) and security margin
index (MI)
• Identification of the vulnerable parts
• Prediction of successive events
• Steady state control by network contribution factor
(NCF), generator distribution factor (GDF), load
distribution factor (LDF), selected minimum load
shedding (SMLS) and final control means
• Verified by AC load flow
Transient stability control scheme (cont.)
• Potential energy boundary surface (PEBS) method
• Analytical sensitivity of the transient energy margin
• Stability control classification: admittance-based control
(ABC) and generator-input-based control (GIBC)
• For each control, to calculate the energy margin variance,
and find control means to make energy margin positive
• Verified by time-domain simulation method
Transient stability control scheme
Transient stability control scheme (cont.)
• Potential energy boundary surface (PEBS) method
• Analytical sensitivity of the transient energy margin
• Stability control classification: admittance-based control
(ABC) and generator-input-based control (GIBC)
• For each control, to calculate the energy margin variance,
and find control means to make energy margin positive
• Verified by time-domain simulation method
Data Needed –PSS/E
Purpose: Power Flow Analysis
• Power Flow Raw Data File (*.raw)
• Slider Binary Data File (*.sld)
Purpose: Fault Analysi
• Sequence Impedance Data File (*.seq)
Data Needed –PSS/E
Purpose: Contingencies Analysis
• Subsystem Description Data File (*.sub)
• Monitored Element Data File (*.mon)
• Contingency Description Data File (*.con)
• LoadThrowover Data Files (*.thr)
Purpose: System Dynamic Analysis
• Dynamics Data File (*.dyr)
• Machine Impedance Data File (*rwm)
Fault Calculation and Analysis
Read Power Flow Raw Data
Build Positive-sequence Network
*.raw
Power Flow Raw Data Files
Add Zero-sequence and Negativesequence Network to Work Space
*.seq
Sequence Impedance Data File
Save Fault Analysis Data from
Work Space
*.sav
Saved Case Data File
Pre-fault Steady State Analysis
Fault Analysis according to Fault
Data File
Output Data File and Analysis
*.out
Channel Output Data File
Dynamic Stability Analysis
Read Save Fault Analysis Data
(Including Zero-sequence and
Negative-sequence Network)
*.sav
Saved Case Data File
Convert Loads and Generators
*.rwm
Machine Impedance Data Files
Read Dynamics Model Data
*.dyr
Dynamics Model Data Files
Perform Dynamic Stability
Analysis
Output Data File and Analysis
*.out
Channel Output Data File
Local Monitoring and Control
Local monitoring and control
SSFD and NNFDC
Synchronized Sampling based Fault Diagnosis
Fault Detection Feature
• Short Line Model
• Long Line Model
When no internal fault, those features equal to zero; When
there is an internal fault, those features are related to fault
current
Synchronized Sampling based Fault Diagnosis
What we need :
Synchronized Sampling based fault diagnosis provides a
very high accuracy in fault detection and location. Not
depend on any assumptions about system operating
conditions, fault resistance, fault waveforms, etc.
We need synchronized raw samples of voltage and
current from both ends of transmission line under
specified sampling rate.
Sources of data:
Relays, PMU, DFR, synchronized with GPS
Neural Network Based Fault Diagnosis and Classification
Overall Scheme
Training and Testing Process
x1
xN
Va
x8*N
Vb
Vc
3V0
Ia
Ib
Ic
3I0
Input Pattern (using normalized raw samples)
Pattern Space
(2-D demo)
Training (Self-Organized Clustering Technique)
Testing (Fuzzy K-nearest neighbor classifier)
Neural Network Based Fault Diagnosis and Classification
What we need :
Neural Network based approach provides a more
accurate fault detection and classification by using
the same data inputs as distance relay.
We need ample enough raw samples of current and
voltage under different situations to finish and verify
the training and testing process. Once the neural
network is well trained, it is capable for online use.
Sources of data:
Can be share with synchronized sampling based
approach.
Event Tree Analysis
t
Example: Event Tree for No-fault Condition
Node
Scenarios
Reference Action
1
No fault in preset zones
Keep monitoring
2
Relay does not detect a fault
Stand by
3
Relay detects a fault and initiates a
trip signal
Check the defects in relay algorithm and
settings
4
Trip signal blocked by the other
device in the system
5
Trip signal failed to be blocked
10
6
Circuit breaker opened by a trip
signal
11
7
Circuit breaker fails to open
8
Autoreclosing succeeds to restore
the line
9
Autoreclosing fails to restore the
line
10
Breaker failure protection trips all
the breakers at the substation
11
No Breaker failure protection or it
doesn’t work
2
4
1
8
3
6
9
5
7
Root node - initial event
Action node - correct action
Action node - incorrect action,
cannot be solved real-time
Action node - incorrect action,
may be solved realtime
Outcome node - improper
Outcome node - proper
Check communication channel
Send blocking Signal if necessary
Check the breaker circuit.
Send reclosing signal to the breaker
Check the circuit of the breaker failure
protection.
Event Tree Analysis
What we need :
Event Tree Analysis provides an efficient way for real
time observation of relay operations and an effective
local disturbance diagnostic support.
According to the characteristics of generic design for
event tree, the number of event trees is finite.
However, it need much work to set up the system. It is
feasible.
Sources of data:
Relay trip signal, circuit breaker contact signal.
Outline
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Introduction
Background
Proposed Solutions
Detailed Algorithm and Data Needed
Next Step
Discuss
Implementation
• Obtain the raw synchronized data from Relays, PMUs
and DFRs;
• Starts local fault analysis when disturbance occurs using
NNFDC and SSFL Tools;
• Monitoring and analyzing relay operations;
• Reports disturbance information and analysis to the
Central.
Algorithm Description
System Modeling
Relay Testing
Digital Simulator
Computer
Signal Waveform
Relay Monitoring
Switching Status
Fault Detection
Setting
Fault Classification
Report
Voltage, Current
Trip Signal
Distance Relay
Scenario Demonstration
Data Library
Relay Setting
Relays
Relay Operation
DFRs
Data of
Collection
Monitoring
Software
Synchronized
sampling data
PMUs
Measurement
System
Monitoring Procedure
Monitoring
Software
Relay
Operations
ETA
Fault Analysis
N
Potential Fault?
Internal
Fault?
Relay
Operations
Decision
Y
Y
NNFDC
SSFL
SSFDC
Relay Operation:
•Misoperation
•Un-intended Operation
•Failure Operation
Outline
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Introduction
Background
Proposed Solutions
Detailed Algorithm and Data Needed
Next Step
Discuss
Thank You!!!
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