OPERATIONAL EXPERIENCE WITH STATE ESTIMATION AT HYDRO-QUÉBEC S. Lefebvre, J. Prévost, J.C. Rizzi, P. Ye (IREQ) B. Lambert, H. Horisberger (TransÉnergie)

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


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


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


Grand Brulé

Chénier

Tilly



MicouaSaguenay

Laurentides

LévisNicolet

Hertel

Boucherville

Duvernay



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



Limite Sud

LimiteManic-Québec


Radisson

70

10

70

96

7011

70317032

7006

702370087007

7053

7026

7084

7090

7 07

9

70487049

7009

7014

7034

LG2

Chissibi


Grand Brulé

Chénier

Tilly



MicouaSaguenay

Laurentides

LévisNicolet

Hertel

Boucherville

Duvernay



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



Limite Sud

LimiteManic-Québec


Radisson

70

10

70

96

7011

70317032

7006

702370087007

7053

7026

7084

7090

7 07

9

70487049

7009

7014

7034

LG2

Chissibi


Grand Brulé

Chénier

Tilly



MicouaSaguenay

Laurentides

LévisNicolet

Hertel

Boucherville

Duvernay



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



Limite Sud

LimiteManic-Québec


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)


18


-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

23

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)

Documents

OPERATIONAL EXPERIENCE WITH STATE ESTIMATION AT HYDRO-QUÉBEC S. Lefebvre, J. Prévost, J.C. Rizzi, P. Ye (IREQ) B. Lambert, H. Horisberger (TransÉnergie)