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Nisheeth Singh, EPCC9, June 2007 1 von 36
Reality Check: On-line SE and Application of Wide Area Measurementsin Future EMS systems
Nisheeth Singh and Walter Sattinger
EPCC9, 11 to 13 June 2007
Nisheeth Singh, EPCC9, June 12, 2007, Ullensveng 2 von 36
State Estimation, Reality Check
• Overview
• Factors influencing quality of SE results
• Practical Examples
• Future Challenges
Wide Area Management, apps in EMS
• WAM in State Estimation and Monitoring
• WAM in Postmortem
• Improvement in Modelling
• Applications
Nisheeth Singh, EPCC9, June 12, 2007, Ullensveng 3 von 36
State Estimation Process
Overview / Error Sources / Examples/Challenges
Get Static Network
Model
Get Dynamic
information from
Scada
Preprocessing of
dynamic and static
data
Topology
Processing
State estimation
algorithm including
Bad Data Detection
and suppression
Postprocessing of
results
Second Pass
Estimation for
nonobservable
network
Nisheeth Singh, EPCC9, June 12, 2007, Ullensveng 4 von 36
Sources of errors in State Estimation Process in real world
Overview / Error Sources / Examples/Challenges
• Modelling inaccuracies
• Measurement Errors
• Parameter related errors
• Observability related errors
Nisheeth Singh, EPCC9, June 12, 2007, Ullensveng 5 von 36
Modelling inaccuracies in State Estimation Process
Overview / Error Sources / Examples/Challenges
•Modelling of the network
•Dynamic network Behaviour
•Modelling of physical / equivalent Elements
•Incorrect Modelling of dynamic elements
•Incomplete Network modelling
•Inconsistency in SCADA and network model
Nisheeth Singh, EPCC9, June 12, 2007, Ullensveng 6 von 36
Modelling inaccuracies : Network Modelling
1
103
102
101
4
32
403
402
401
303
302
301
203
202
201
Nisheeth Singh, EPCC9, June 12, 2007, Ullensveng 7 von 36
Modelling inaccuracies : Wrong Network Modelling
Nisheeth Singh, EPCC9, June 2007 8 von 36
49.85
49.9
49.95
50
50.05
49.85
49.9
49.95
50
50.05
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
50.00
50.05
50.10
49.95
49.85
49.90
Fre
quency
[Hz]
49.85
49.9
49.95
50
50.05
Schedule
Change [G
W]
0
1
2
3
4
5
Modelling inaccuracies: Dynamic Network behaviour
Nisheeth Singh, EPCC9, June 12, 2007, Ullensveng 9 von 36
Modelling inaccuracies: Modelling of Physical / equivalent elements
Nisheeth Singh, EPCC9, June 12, 2007, Ullensveng 10 von 36
Modelling inaccuracies in State Estimation Process
•Incorrect Modelling of dynamic elements
•Incomplete Network modelling
•Inconsistency in SCADA and network model
Nisheeth Singh, EPCC9, June 12, 2007, Ullensveng 11 von 36
Measurement Errors in State EstimationProcess
• Error in Sign of Measurement
• Wrong Process Point Reference
• Time Skew over measurements
• Inherent errors in Measurement System
Nisheeth Singh, EPCC9, June 12, 2007, Ullensveng 12 von 36
Measurement Errors: Error in Sign of Measurement
Generation and load with correct flow sign,
net flow out of node 200 MW
MW
MVAr
Kv
400 MW
100 MVAr
220 Kv
MW
MVAr
Kv
200 MW
80 MVAr
220 Kv
MW
MVAr
Kv
MW
MVAr
Kv
MW
MVAr
Kv
MW
MVAr
Kv
MW
MVAr
Kv
Generation and load with incorrect flow sign,
net flow out of node 600 MW
MW
MVAr
Kv
400 MW
100 MVAr
220 Kv
MW
MVAr
Kv
200 MW
80 MVAr
220 Kv
MW
MVAr
Kv
MW
MVAr
Kv
MW
MVAr
Kv
MW
MVAr
Kv
MW
MVAr
Kv
Nisheeth Singh, EPCC9, June 12, 2007, Ullensveng 13 von 36
Measurement Errors: Time Skew over measurements
Ceuta
Nisheeth Singh, EPCC9, June 12, 2007, Ullensveng 14 von 36
Measurement Errors: Inherent errors in Measurement
MW
MVAr
Kv
MW
MVAr
Kv
MW
MVAr
Kv
398 kV 400 kV 402 kV
Voltage Measurements
at same node could be
Upto 1% different.
Causing a significant
error in Reactive power
Nisheeth Singh, EPCC9, June 12, 2007, Ullensveng 15 von 36
Parameter related errors in State EstimationProcess
• Transformer Tap Steps
• Accuracy of Parameters
• Wrong parameters
• Parameters requiring Special care
Nisheeth Singh, EPCC9, June 12, 2007, Ullensveng 16 von 36
Parameter related errors: Transformer Tap Steps
Overview / Error Sources / Examples/Challenges
2
3
-3
-2
-1
0
1
Actual Taps on
HV Winding
-2
-3
3
2
1
0
-1
Taps in wrong
Sequence on HV
Winding
2
3
-3
-2-1
0
1
Taps Modelled on
Wrong Winding
Nisheeth Singh, EPCC9, June 12, 2007, Ullensveng 17 von 36
Parameter related errors: Accuracy of Parameters
• Accuracy of Parameters
• Change in parameters over time
• Change in parameters due to ambient conditions
• Accuracy in factory measurements
Nisheeth Singh, EPCC9, June 12, 2007, Ullensveng 18 von 36
Parameter related errors: Wrong Parameters
Actual CT Ratio
1000: 5 amps
Wrongly given CT
Ratio 1000:1
amps
Actual Power 1000 MW Measured Power 200 MW
Nisheeth Singh, EPCC9, June 12, 2007, Ullensveng 19 von 36
Parameter related errors: Parameters requiring Special care
Some parameters require special treatment such as
• Very Short lines and cables
• Lines with different physical segments
• Equivalent impedance (Near zero or negative)
Nisheeth Singh, EPCC9, June 12, 2007, Ullensveng 20 von 36
Observability related errors in State EstimationProcess
• Data Exchange with partners
• Data Exchange with Substation Control
• Temporary Unavailability of measurements
• Local Observability in power plants
• Low Redundancy in Measurements
Nisheeth Singh, EPCC9, June 12, 2007, Ullensveng 21 von 36
Observability related errors: Data Exchange with partners
Nisheeth Singh, EPCC9, June 12, 2007, Ullensveng 22 von 36
Observability related errors: temporary / local Oberservability
• Loss of data from Substation Control
•Temporary Unavailability of measurements
• Local Observability in power plants
• Low Redundancy in Measurements
Nisheeth Singh, EPCC9, June 12, 2007, Ullensveng 23 von 36
Future Challenges
• Use of SE results in Historical database
• Display of SE results on Graphical Interface
• Phase Angle Measurements in SE
• Standardisation in Data Modelling and exchange
Nisheeth Singh, EPCC9, June 12, 2007, Ullensveng 24 von 36
Loading
Contour after
Calculations
Nisheeth Singh, EPCC9, June 12, 2007, Ullensveng 25 von 36
System State form SE Results
Vulnerable
Back to Normal
Nisheeth Singh, EPCC9, June 12, 2007, Ullensveng 26 von 36
Wide area Monitoring
