1. No category

OPERATIONAL EXPERIENCE WITH STATE
ESTIMATION AT HYDRO-QUÉBEC
S. Lefebvre, J. Prévost, J.C. Rizzi, P. Ye (IREQ)
B. Lambert, H. Horisberger (TransÉnergie)
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
•
Transmission
735 & 315 kV AC systems
Multi Terminal DC line 450 kV (over 1000 km)
4 back to back DC Terminals (soon 5!)
•
Sub transmission
230, 161, 120 & 69 kV AC systems
2
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)
3
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
4
State estimation experience
 LASER0

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In-house product
Pd 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
5
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)
6
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)
7
SE model
Equipment
Load points
Series cap
Substations
Generators
Transformers
Sync comp
SVC
Shunt reactors/cap
Measurements
Breakers/switches
/isolators
Lines
Actual
dimensions
Near half of switches are
breakers that are 100%
telemetered
532
42
281
348
551
9
13
250
4900
5012
The other half is reconfiguring 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
562
8
SE measurements and their redundancy
kV mP+0J mQ+0J
mV
n
m/2n m/nPd 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
1733 1733 1241 855
2.8
2.0
3.5
All
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 Pd
counterpart (2.0)
9
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-d 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)
10
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)
11
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 (s = f(burden))
12
SE solution quality
JT  M  2 N
m
J M   rW (i ) 2
i 1
Relative Performance index (%)  100* J M
13
JT
SE usage (example 1)
Topology error detection:
Side effect
L7018
L7019 L7026
CXC15
905
-1 VOLT
0-J
JAC CAR LINE
XFR2
906 -1 VOLT
0-J
CHAMO
LINE
MICOUA
LNSX
XFR2
907 -1 VOLT
0-J
MICOUA
LINE
S-D
735
735
L7018
T1
735
735
735
L7026
L7019
T2
735
735
735
L7019
CXC15010
CP
744.2
0.0
1023.0
0.0
-189.0
CP
CP
743.6
0.0
-864.0
-822.0
0.0
-24.0
-111.0
0.0
0.0
749.3
0.0
40.1
-40.1
740.9
0.0
-243.9
-478.4
722.3
731.7
0.0
-478.5
478.4
14.2
0.0
-118.3
118.3
25.0
0.0
-82.0
-143.9
226.0
23.9
0.0
-298.4
298.4
-0.7
EW
T1
0.4
T2
EW
EW
REJETE
Topology error
Wrong manual entry
14
TELE
SE usage (example 2)
Parameter validation:
Z1
Z3
L3098
Z2
Z4
Boucherville
Bout-de-l’île
L3019
MEASURED AND ESTIMATED VALUES (2004/01/15 17:19)
ID s
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
Double circuit of short length, modeled as equal length
but in reality not exactly the same length
15
SE usage (example 3)
Accurary improvement:
Chénier
La Vérendrye
7044
7047
7045
Némiscau
7082
7081
7080
Radisson
7063
7062
7061
LG2
7089
7088
Grand Brulé
7024
7025
7017
7009
Duvernay
Jacques
Chamouchouane
Cartier
7018
7078
7077
7076
Micoua
7034
7028
Nicolet
Lévis
7005
7035
7006
7049
7097
7096
7027
7011
Limite
Manic-Québec
7010
7036
7038
Laurentides
Montérégie
Le Moyne
7004
Limite Sud
7048
7070
7069
Chibougamau Albanel
Saguenay
Tilly
7056
7055
7054
7019
Boucherville
Hertel
7057
7059
7086
7085
7084
7026
Carignan
7014
7020
7002
Châteauguay
7060
7079
7016
Chissibi
Limite
Baie James Nord
7090
7046
Limite
Baie James Sud
7042
Flow735: smeas/ sest> 3
Abitibi
7094
7093
7092
7007
7008
7023
Arnaud
Montagnais
7031
7032
7033
7029
7095
Appalache
Manicouagan
Des Cantons
« Limite sud » flow evaluation:
Measurements accuracy: 3s =360 MW
Estimates accuracy: 3s = 120 MW
Can increase the margin by 240 MW!!!
16
Churchill
Falls
7053
7052
7051
Limite
Churchill-Manic
SE usage (example 4)
Corona evaluation & minimization:
Average: 8 MW loss reduction (1%)
Improved by voltage control (low & flat)
17
18
Te mps
Average: 33 MW loss reduction (4%)
Improved by voltage control (high & flat)
dec-26-06_0839
dec-13-06_0504
nov-27-06_0809
nov-11-06_2129
oct-30-06_0629
oct-11-06_0014
sep-25-06_2029
sep-13-06_0034
aug-29-06_1414
jul-28-06_1334
jul-13-06_0419
jun-30-06_1554
jun-14-06_2339
jun-02-06_0914
may-21-06_0224
may-08-06_1529
mar-20-06_1754
mar-08-06_0639
feb-23-06_1639
feb-11-06_0224
jan-27-06_2309
jan-13-06_1734
jan-01-06_0004
Pertes economisées
SE usage (example 5)
Loss evaluation & minimization:
100
80
60
40
20
0
-20
Conclusion
 Need for SE Technology that can handle more
appropriately practical issues

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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
19
Conclusion
 Need for SE support tools



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
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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, …)

20
Questions ?
21
22
Hydro-Québec TransÉnergie
Control centers architecture
Provincial / area
Control Center
Phone
IEC 60870-5
ICCP
Regional
Control Center
DNP3
Power plant /
Transmission
substation
7
DNP3
Sub transmission
substation
Proprietary
Distribution
control center
23
MODBUS ..
Phone
Distribution
feeder
Hydro-Québec TransÉnergie
Provincial control center
(main information functions & information flows)
Flow limits
ATCs

Limit violations
Switching advices
Power flow
optimization
Control
order
Limit service
State estimation
Network
solution
Contingency
analysis
Snapshot
frequency
control
SCADA

Setpoints
Telemetry
Regional control
centers
Remote terminal
units
24
The real-time sequence (RTS)
of the network analysis tools
runs every minute
(500 full AC contingencies, 5 min)