OPERATIONAL EXPERIENCE WITH STATE ESTIMATION AT HYDRO-QUÉBEC
S. Lefebvre, J. Prévost, J.C. Rizzi, P. Ye (IREQ)
B. Lambert, H. Horisberger (TransÉnergie)
2
Network description
Main network• Generation
Installed capacity of around 38 000 MW
Over 95% of the generation is hydro (soon 4000 MW of wind!)
Asynchronous with the rest of North America
• Transmission735 & 315 kV AC systems
Multi Terminal DC line 450 kV (over 1000 km)
4 back to back DC Terminals (soon 5!)
• Sub transmission230, 161, 120 & 69 kV AC systems
3
Network Description (next …)
735 kV Grid Components
• 11000 km of lines (charging around 33 000 MVAR)• Series capacitors: 12 000 MVAR• Switched inductors: 25 000 MVAR• Switched capacitors: 13 000 MVAR• SVC & SC: -3800 – 5800 MVAR
Characteristics• Operation constrained by stability and voltage limits
(almost no thermal limit)• Generally operated well under the SIL
(lines switching can even be used for voltage control)• Ramping rate becoming more and more important ( 200 MW/Min.)
(may even cause voltage control difficulties)• Corona effect may suddenly become important
(may reach over 2 times the thermal losses: e.g. 1000 MW)
4
Current status of system control
Hydro Quebec EMS/SCADA control centers One Provincial control center (EMS) and one back up center
• Responsible of the bulk transmission grid (735 to 315 kV)• Main Functions: - Data acquisition
- Automatic Generation Control- Economic Dispatch- Security Analysis- Exchange management- Outage Management- Voltage control
Seven regional control centers (SCADA)• Responsible of the sub transmission grid (230 kV to 69 kV)• Main Functions: - SCADA (for the full HQ’s network)
- Outage Management• Operations are usually triggered by operators from the provincial center
and then are executed by operators at the regional centers
5
State estimation experience
LASER0
In-house product P and QV decoupled algorithm Model: 735 kV network
LASER1
Commercial product: ABB In house simple pre-processing topology error function
LASER2
Commercial product: SNC (formerly CAE) In house elaborate pre-processing topology error function
6
State estimation latest development at HQ’s
Archiving system In-house product Main functions:
- Static network model (CIM/XML) saved after each DB update
- Dynamic raw input/output of SE function saved at each RTS run
- Power flow case (IEEE) saved after each RTS run
Matlab SE toolbox In-house product Main functions:
- Real time snapshot handling - Sub network extraction (by substation or voltage level)- Measurement system analysis (redundancy, identification of critical meas.)- SE algorithms (WLS, Huber, DWLS) - Cases modification & comparison- Parameter estimation - Monte Carlo simulations (evaluation of the solution sensitivity & precision)
7
State estimation latest development at HQ’s (next …)
Reporter In-house product Main goal: Identification of topology and measurement errors
Robust approach (no false alarm) Operate on a continuous base (24/7) Independent of SE solution (convergence, false rejected meas., …) Based on a heuristic approach: a set of rules, combinatorial
analysis and iterative processing Takes advantage of previous network & telemetry data (Hn-1, Zn-1)
Filtering reporting capability (already know bad modeling, …) Historical reporting capability (error, start & end time, frequency, …)
Others reporting possibility (performance index degradation, …) Web & email reporting (used by the support engineer team)
8
SE model
Equipment Actual
dimensions
Load points 532 Series cap 42 Substations 281 Generators 348 Transformers 551 Sync comp 9 SVC 13 Shunt reactors/cap 250 Measurements 4900 Breakers/switches /isolators
5012
Lines 562
Near half of switches are breakers that are 100% telemetered
The other half is reconfigu- ring switches and only 70% are telemetered.
Thus over 750 switches are based on a manual entry
Moreover not all switch are modeled. By example maintenance switches are rarely modeled
9
SE measurements and their redundancy
kV mP+0J mQ+0J mV n m/2n m/nP m/nQV
7XX 231 231 178 79 4.1 2.9 5.2
3XX 403 403 240 140 3.7 2.9 4.6
2XX 224 224 142 88 3.4 2.5 4.2
1XX 523 523 367 222 3.2 2.4 4.0
06X 44 44 12 19 2.6 2.3 2.9
01X 308 308 302 307 1.5 1.0 2.0
All 1733 1733 1241 855 2.8 2.0 3.5
m: number of measurements n: number of states
The 735 transmission grid model has a very good redundancy (4.1).
The sub-transmission grid model has a lower redundancy (2.6)
QV redundancy (3.5) is much higher than its P counterpart (2.0)
10
SE problems
Topology error Originate mainly from maintenance work Bad series switch status (bus split/merge more diffcult to identify) Bad shunt switch status (more diffcult to identify)
Q-V model more complex, more sensitive and less accurate than P- model A important quantity of reactive (accuracy can become a problem) A lot of elements (Serie cap, reactors, SVC, …)
Weather dependant parameters Corrona effect (from almost 0 to 2 times thermal losses) Temperature (from -40 celcius to +40 celcius -> 30% of errror)
11
SE model is never exact
Inequality constraint cannot be model (ex: power limit, …) Mutual effect cannot modeled (ex: on double circuit Z11~ 5%*Z1) Complex equipments (DC, SVC, …) generally can only be
modeled as simple injection Variable system parameters as affected by temperature and
humidity are generally not considered (ex: corona loss , …) Three-windings transformer generally modeled as two-windings Constant LTC Transformer impedance often used Isolation switches and/or breaker not always modeled
(represented only in their normal position) Small load not always modeled (auxiliary service) Network modification (ex: new line) not always in sync with the
model Transmission line parameters calculation often based on typical
values (height, span, sag)
12
SE measurements is never exact
Manual entry inaccuracy (switch status, …) Presence of time skew
(ex: 25s. between provincial and the regional centers)(ex: manual entry can be delay by several minutes)
Measurement dependency (V, I, P, Q) Presence of dead bands in the acquisition chain Measurement bias (e.g. in CCVT) Presence of unbalance (zero and negative sequence) Use of phase measurements vs sequence (direct)
measurements Variable standard deviation (= f(burden))
13
SE solution quality
2( )
1
m
M W ii
J r
2TJ M N
100* M
T
JJ
Relative Performance index (%)
14
SE usage (example 1)
Wrong manual entry
Topology error detection:
905 -1 VOLT 735 744.2 749.3 14.2 -0.7 0-J 735 0.0 0.0 0.0 0.0 JAC CAR LINE L7018 CP 1023.0 -189.0 40.1 -118.3 EW XFR2 T1 735 -40.1 118.3 906 -1 VOLT 735 743.6 740.9 25.0 0.4 0-J 735 0.0 0.0 0.0 0.0 CHAMO LINE L7026 CP -864.0 -24.0 -243.9 -82.0 EW MICOUA LNSX L7019 CP -822.0 -111.0 -478.4 -143.9 EW XFR2 T2 735 722.3 226.0 907 -1 VOLT 735 731.7 23.9 0-J 735 0.0 0.0 0.0 0.0 MICOUA LINE L7019 -478.5 -298.4 S-D CXC15010 478.4 298.4
REJETE
TELE
L7018
T1 T2
L7019 L7026
CXC15
Side effect
Topology error
15
SE usage (example 2)
L3019
L3098
Bo
ucherville
Bo
ut-de-l’île
Z1
Z2
Z3
Z4
Double circuit of short length, modeled as equal lengthbut in reality not exactly the same length
Parameter validation:
MEASURED AND ESTIMATED VALUES (2004/01/15 17:19)
I D Zmeas. Zest. rw
Z1p 4.33 -435.5 -407.7 -6.42*
Z2p 4.33 -410.5 -407.7 0.65
Z3p 4.33 427.9 408.7 4.43*
Z4p 4.33 409.5 408.7 0.18
* rejected measurement
16
SE usage (example 3)
7011
70317032
7006
702370087007
7053
7026
7084
7090
7 07
9
70487049
7009
7014
7034
LG2
Chissibi
NémiscauAbitibiLa Vérendrye
Grand Brulé
Chénier
Tilly
Le MoyneAlbanelChibougamau
ChamouchouaneJacquesCartier
MicouaSaguenay
Laurentides
LévisNicolet
Hertel
Boucherville
Duvernay
CarignanChâteauguay
ManicouaganAppalache
Des Cantons
Arnaud
7060
70897088
706170627063
704 6
708270817080
709470937092
7045
7016
70447047
7042
7 03 8
7 03 6
7002
7017
702 0
7019
7004
7018
7028
70297005
7097
7095
70247025 7085
7086
7057
705470557056
7059
70707069
707870777076
7027
Montérégie
7035
7052
Montagnais
ChurchillFalls
7033 7051
LimiteBaie James Sud
LimiteBaie James Nord
Limite Sud
LimiteManic-Québec
LimiteChurchill-Manic
Radisson
70
10
70
96
7011
70317032
7006
702370087007
7053
7026
7084
7090
7 07
9
70487049
7009
7014
7034
LG2
Chissibi
NémiscauAbitibiLa Vérendrye
Grand Brulé
Chénier
Tilly
Le MoyneAlbanelChibougamau
ChamouchouaneJacquesCartier
MicouaSaguenay
Laurentides
LévisNicolet
Hertel
Boucherville
Duvernay
CarignanChâteauguay
ManicouaganAppalache
Des Cantons
Arnaud
7060
70897088
706170627063
704 6
708270817080
709470937092
7045
7016
70447047
7042
7 03 8
7 03 6
7002
7017
702 0
7019
7004
7018
7028
70297005
7097
7095
70247025 7085
7086
7057
705470557056
7059
70707069
707870777076
7027
Montérégie
7035
7052
Montagnais
ChurchillFalls
7033 7051
LimiteBaie James Sud
LimiteBaie James Nord
Limite Sud
LimiteManic-Québec
LimiteChurchill-Manic
Radisson
70
10
70
96
7011
70317032
7006
702370087007
7053
7026
7084
7090
7 07
9
70487049
7009
7014
7034
LG2
Chissibi
NémiscauAbitibiLa Vérendrye
Grand Brulé
Chénier
Tilly
Le MoyneAlbanelChibougamau
ChamouchouaneJacquesCartier
MicouaSaguenay
Laurentides
LévisNicolet
Hertel
Boucherville
Duvernay
CarignanChâteauguay
ManicouaganAppalache
Des Cantons
Arnaud
7060
70897088
706170627063
704 6
708270817080
709470937092
7045
7016
70447047
7042
7 03 8
7 03 6
7002
7017
702 0
7019
7004
7018
7028
70297005
7097
7095
70247025 7085
7086
7057
705470557056
7059
70707069
707870777076
7027
Montérégie
7035
7052
Montagnais
ChurchillFalls
7033 7051
LimiteBaie James Sud
LimiteBaie James Nord
Limite Sud
LimiteManic-Québec
LimiteChurchill-Manic
Radisson
70
10
70
96
7011
70317032
7006
702370087007
7053
7026
7084
7090
7 07
9
70487049
7009
7014
7034
LG2
Chissibi
NémiscauAbitibiLa Vérendrye
Grand Brulé
Chénier
Tilly
Le MoyneAlbanelChibougamau
ChamouchouaneJacquesCartier
MicouaSaguenay
Laurentides
LévisNicolet
Hertel
Boucherville
Duvernay
CarignanChâteauguay
ManicouaganAppalache
Des Cantons
Arnaud
7060
70897088
706170627063
704 6
708270817080
709470937092
7045
7016
70447047
7042
7 03 8
7 03 6
7002
7017
702 0
7019
7004
7018
7028
70297005
7097
7095
70247025 7085
7086
7057
705470557056
7059
70707069
707870777076
7027
Montérégie
7035
7052
Montagnais
ChurchillFalls
7033 7051
LimiteBaie James Sud
LimiteBaie James Nord
Limite Sud
LimiteManic-Québec
LimiteChurchill-Manic
Radisson
70
10
70
96
« Limite sud » flow evaluation:Measurements accuracy: 3=360 MWEstimates accuracy: 3= 120 MWCan increase the margin by 240 MW!!!
Accurary improvement:
Flow735: meas/ est> 3
17
Corona evaluation & minimization:
Average: 8 MW loss reduction (1%)
Improved by voltage control (low & flat)
SE usage (example 4)
18
SE usage (example 5)
-20
0
20
40
60
80
100ja
n-01-06_0004
jan-13-06_1734
jan-27-06_2309
feb-11-06_0224
feb-23-06_1639
mar-08-06_0639
mar-20-06_1754
may-08-06_1529
may-21-06_0224
jun-02-06_0914
jun-14-06_2339
jun-30-06_1554
jul-13-06_0419
jul-28-06_1334
aug-29-06_1414
sep-13-06_0034
sep-25-06_2029
oct-11-06_0014
oct-30-06_0629
nov-11-06_2129
nov-27-06_0809
dec-13-06_0504
dec-26-06_0839
Temps
Pertes eco
no
misées
Average: 33 MW loss reduction (4%)
Improved by voltage control (high & flat)
Loss evaluation & minimization:
19
Conclusion
Need for SE Technology that can handle more appropriately practical issues Adding more measurements is not always the solution
(although useful) SE does not only provide states (X) but also a model (H)
So, even if PMU may help, it will not solve all problems Model & errors/inaccuracies cannot be avoided
So, model should not be considered as “hard constraint” (at least for parameters like R & G, and may be even X for LTC!)
All information available should be used (inequality constraint, setpoint, previous data (Zn-1, Hn-1), quality (manual, telem., …),tag
Electrical topology (not necessary physical) error detection, identification and correction function should be de facto available
Sudden quality change (residues, rejected meas., …) should trigger a validation mechanism
20
Conclusion
Need for SE support tools Quality indexes evaluation (standard indexes will also be nice!) Measurements analysis (critical meas., local redundancy, …) Model analysis (parameter estimation, sensitivity, …) Solution analysis (estimate accuracy, robustness in regard of
meas. loss, …) Visualization tools for analysis and debugging (ex:3D diagram
showing residues, biases, rejected meas.) Model validation tools (modification, solutions comparator, …)
Improved SE solution quality will increase its role Transmission optimization (LM, DSA, …) Market operation (ED, …)
21
Questions ?
22
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Hydro-Québec TransÉnergieControl centers architecture
Provincial / areaControl Center
Power plant /Transmission
substation
Sub transmissionsubstation
RegionalControl Center
7
Phone
ICCP
IEC 60870-5
DNP3
DNP3
Distributionfeeder
Distributioncontrol center
MODBUS ..
Phone
Proprietary
24
Limit violations
Switching advices
Networksolution
Telemetry
Hydro-Québec TransÉnergieProvincial control center (main information functions & information flows)
Regional controlcenters
SCADA
State estimationLimit service
Power flowoptimization
frequencycontrol
Setpoints
Snapshot
Remote terminalunits
Contingencyanalysis
Flow limitsATCs
Controlorder
The real-time sequence (RTS) of the network analysis tools
runs every minute
(500 full AC contingencies, 5 min)