Gestionnaire du Réseau de Transport d'electricité On line security assessment based on probabilistic approach and data mining P. Panciatici, S. Henry EPCC, June 2007
EPCC, June 2007 2 An example : Operating rules against voltage collapse in the southeast region of France (PACA) Context Statistical method. consistency check of samplings Results and conclusions Improvement : base cases selection
Context: PACA area EPCC, June 2007 3 PACA: Area with potential problems of voltage collapse vers MONTRICHER vers VALENCE SERRE-BARBIN vers CHAMPAGNIER BRIANCON vers PRATCLAUX L ARGENTIERE MONTPEZAT LOGI CRUAS-MEYSSE COULANGE S- GRISOLLES BOUDEYRE PIED-DE-BORNE NEUF SERRE-PONCON CHÂTEAU-NEUF-DU-RHONE CURBANS LAFIGERE TRICASTIN PIERRELATTE TRICASTIN BOLLENE BARJAC PHENIX SISTERON VIRADEL L ARDOISE VALABRES S ST AUBAN BANCAIRON vers CAMPOROSSO T vers ST-VICTOR LA MOTTE CASTILLON ROQUEBILLIERE TERRADOU BROC-CARROSD ITALIE T AVIGNON ORAISON LA CHAUDANNE MENTON MOUISSONNES A GANGES AG ARAMON A ROUMOULES LINGOSTIERE TRINITER L JONQUIERES ASSV CHATEAURENARD STE TULLE P. DE GRASSE RISSO CAGNES/MER ST-CESAIRE BEAUCAIRE P. D ORGON STE CROIX MOUGINSM E T.S. QUINSON A L BOUTRE Nice ROQUEROUSSE ST ESTEVE S TRANS vers TAMAREAU RASSUENST CHAMAS vers ST-CHRISTOL PALUN FEUILLANE ROGNAC VINS CABAN SEPTEME LAVERA Réaltor ARENC RENAIRES ENCO-DEBOTTE DARSE BELLE DE NEOULES MARTIGUES-PONTEAU MAI MAZARGUES RABATAU COUDON VALLAT Marseille L ESCAILLON Toulon Assess the collapse risk in real time Groupe Ligne 400 kv Ligne 225 kv Nice area is nearly an antenna (few interconnections) Unbalanced : generation (west) and load (east) Operating rules usable in real time allowing the prevention of voltage collapse in PACA
EPCC, June 2007 4 A rule to assess if a situation is acceptable (first rule in 1997) 400 kv Voltage (Réaltor) > 390 kv Acceptable situation AND Reactive Generation (hydro plants in Durance+Verdon) < 400 Mvar Simple and clear criteria Used in real time AND Regional Reactive Import < 260 Mvar REFUSE Decrease of the imposed generation Economy: ~ 1 M per year OK
Base case Random samplings Build of the situations EPCC, June 2007 5 General method Optimal Power Flow Selection of realistic situations Set of situations Situation probabilities Contingency simulations Margin computations Statistical analysis Decision trees Operating rules Measure of consequences Characterisation of situations
Build of the situations EPCC, June 2007 6 Base case: created from a snapshot (winter peak) The samplings carried out for each situation are: line and transformer unavailabilities load level of the area production (in the area and surrounding areas)
Random samplings EPCC, June 2007 7 Topology: Max. of 1 unavailable device (transformer or line in the area) Load level: [4500 MW ; 8000 MW] in the area Generation : availability of regional units surrounding areas units remote units Busbar configuration in 2 important substations in Roquerousse: two nodes in 50 % of the cases in Sisteron : two nodes when generation of Durance valley is high and load level low. Noise on some parameters : (α,β), Qmax, Vc of voltage control pilot points
EPCC, June 2007 8 Initial point determination The initial point is determined with an Optimal Power Flow: generation start-up (with respect of unit samplings) voltage profile in the area ( Vmin,Vmax) We suppress from the set, the situations for which the OPF doesn't converge or converge with: load shedding an amont of Mvar added larger than 150 Mvar Corresponding cases are mainly due to unrealistic samplings (no correlation taken into account)
EPCC, June 2007 9 Description of the set of situations initial situations Total Number of situations 30.000 kept situations after OPF Total Number of situations 13.636 this emphasizes the need for the generation of a large number of initial situations
Base case Random samplings Build of the situations EPCC, June 2007 10 Consistency check of samplings Optimal Power Flow Selection of realistic situations Set of simulated situations Data base of snapshots Comparison of statistics on some important variables Consistent? NO
A priori Important variables EPCC, June 2007 11 vers MONTRICHER vers PRATCLAUX vers ST-VICTOR PIED-DE-BORNE LAFIGERE GANGES vers TAMAREAU MONTPEZAT CRUAS-MEYSSE VIRADEL BOUDEYRE BARJAC LOGIS-NEUF CHÂTEAU-NEUF-DU-RHONE PIERRELATTE TRICASTIN BOLLENE PHENIX L ARDOISE LA MOTTE TERRADOU TAVE AVIGNON MOUISSONNES AGASSE L ARAMON S CHATEAURENARD JONQUIERES ST-CESAIRE BEAUCAIRE P. D ORGON vers ST-CHRISTOL TRICASTIN vers VALENCE COULANGE vers CHAMPAGNIER CURBANS L ARGENTIERE GRISOLLES BOUTRE ROQUEROUSSE ST ESTEVE TRANS RASSUEN ST CHAMAS PALUN FEUILLANE ROGNAC VINS CABAN REALTOR RENAIRES LAVERA SEPTEME ARENC ENCO-DEBOTTE DARSE BELLE DE MAI NEOULES MARTIGUES-PONTEAU MAZARGUES RABATAU COUDON VALLAT L ESCAILLON SERRE-BARBIN BRIANCON SERRE-PONCON SISTERON VALABRES ST ST AUBAN DALMAS vers CAMPOROSSO BANCAIRON CASTILLON ROQUEBILLIERE ITALIE BROC-CARROS ORAISON LA CHAUDANNE MENTON ROUMOULES LINGOSTIERE TRINITE-VICTOR STE TULLE P. DE GRASSE RISSO CAGNES/MER T.S. STE CROIX MOUGINS QUINSON Voltage in «REALTOR», Flows on «TAVEL- REALTOR» lines
Distribution of a variable EPCC, June 2007 12 1 1 0,9 0,9 0,8 0,8 0,7 0,7 0,6 0,6 0,5 0,5 0,4 0,4 0,3 0,3 0,2 0,2 0,1 0,1 0 0 97 97 98 98 99 99 100 100 101 101 102 102 103 104 103 actual actual simulated Consistent if = similar distributions with more extreme values for simulated cases
Base case Random samplings Build of the situations EPCC, June 2007 13 General method Optimal Power Flow Selection of realistic situations Set of situations Contingency simulations Margin computations
Margin computation find the maximum stress (load increase) that the system can whistand after a contingency EPCC, June 2007 14 Initial load level + max stress Initial load level + (max stress/2) Not OK OK Initial load level OK t
EPCC, June 2007 15 Margin computation stop criteria : OLTC blocking threshold voltage unstability a margin computation is carried out on each kept scenario
Situation classification EPCC, June 2007 16 each situation can be characterised as acceptable or unacceptable toward the voltage collapse risk using the computed margin (load increase) acceptable margin > 200 MW unacceptable margin 200 MW in the set Number margin 200 MW 2093 margin > 200 MW 24.507 % base 9 % 91 %
What rule? EPCC, June 2007 17 predict as best as possible if a situation is acceptable or unacceptable toward voltage collapse risk REFUSE it must be based on variables available in real time in the control room based on pre-contingency values simple and clear OK
Rule efficiency EPCC, June 2007 18 ND = number non detection rate of unacceptable situations classified as number of unacceptable situations acceptable false alarm rate FA = number of acceptables situations classified as number of acceptable situations unacceptable PACA cost(fa) cost(nd) ND 0 AND min(fa)
Possible attributes EPCC, June 2007 19 Build of the rules using the following simple attributes, easily available in the control room : active and reactive loads in the area active and reactive generations in the area and in surrounding areas (individually or aggregated by zone) active and reactive flows of area lines (400 kv and 225 kv) North/South and West/East active and reactive flows Regional Reactive importations 400 kv and 225 kv voltages in the area availability of some generators network topology
Most efficient attributes EPCC, June 2007 20 Regional Reactive import (threshold 300-400 Mvar) Reactive reserve in the area (450 Mvar) Reactive generation of valleys Durance-Verdon (300 Mvar) Active flows on Tavel-Realtor (1800 MW)
Main rules EPCC, June 2007 21 Rule Criteria ND FA R1 Reactive import PACA < 300 Mvar 0,3 % 46 % R2 R3 R4 R5 Reactive import PACA < 350 Mvar Reactive import PACA < 400 Mvar Reactive import PACA < 350 Mvar Q_Durance_Verdon < 160 Mvar Reactive reserve PACA > 450 Mvar P_Tavel_Réaltor < 1840 MW V400_Réaltor > 398 kv 0,04 % 0,04 % 0,14 % 0,04 % 40 % 51 % 65 % 58 % R6 Current rule Reactive import PACA < 350 Mvar Reactive import PACA < 260 Mvar Q_Durance_Verdon < 170 Mvar Q_Durance_Verdon < 400 Mvar V400_Réaltor > 390 kv 0,04 % 0,04 % 59 % 53 % Reduced rule Reactive import PACA < 260 Mvar 0,04 % 53 % ND 0,3 % R1 0,2 % R4 0,1 % R2 R3 R6 0 % RA R5 0 % 20 % 40 % 60 % 80 % 100 % FA
EPCC, June 2007 22 First rule (1997) Acceptable situation Voltage 400 kv (Réaltor) > 390 kv AND Reactive_Production (Durance+Verdon) < 400 Mvar AND Reactive import PACA < 260 Mvar ND = 0,04 % FA = 53 % efficient rule: low ND but highly conservative: high FA
EPCC, June 2007 23 Decision tree example : first rule (1997)
EPCC, June 2007 24 Some conclusions Voltage attributes are not efficient Composite attributes are very interesting Current rule is satisfying but conservative. A large number of cases are eliminated after OPF Large modifications are needed to build situations from the base case and could lead to unrealistic states. Active nodal loads are obtained from the global load by a poor proportional law, Reactive nodal loads are obtained keeping the power factor constant.
EPCC, June 2007 25 Proposed improvement : base cases selection For each sample Select some important variables Snapshots Choose the «nearest» snapshot based on the selected variables Base Case (could be different for each sample) The approach is promising, definition of the nearest snapshot?