RTE France

7/28/2019 RTE France

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Gestionnairedu Rseau de Transport d'Electricit

2008 IEEE PES General Meeting: Panel on Best Practices in State Estimation

Experiences and practices on State Estimation in

RTE (French Transmission System Operator)

Patrick Panciatici (RTE), Yacine Hassaine (RTE)


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2008 IEEE PES General Meeting: Panel on Best Practices in State Estimation, 2

Presentation of SE in RTE

RTE operates the whole French transmission system : (400kV to 63kV, 2500

substations, 100300 km of circuits and 1150 transformers), 7 regional control

centers and 1 National

State Estimation provides input for all networks analysis

Measurements are received every 10 s.

An event is sent, when the status of a switching device changes.

Which kind of measurements ?Active and reactive power flows on branches,

Active and reactive powers on load and generators,

Voltage magnitudes in substation on busbars,

Internal substation current measurements and tap positions are not transmitted.

Coherent stateMeasurements, Topology

Electrical characteristics

State

Estimation


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Snapshot Generation : Consistency between topology and measurements

A new status may arrive before measurements affected by the switching, this could lead

to an incoherent state between topology and measurements and to a problem in state

estimation.

To minimize the probability of occurrence of this problem, we apply a very important and

classical rule to generate a snapshot

We wait 20s to generate a snapshot after the reception of the last switching device

status.

A snapshot is generated after 1mn even if the condition isnt fulfilled


t t+10

Measurements (t)

Measurements (t+10)

switching

Inconsistent

Snapshot


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Observability :

A numerical observability is used, with a decoupled Jacobian matrix.

better numerical robustness in SE

Critical pseudo-measurements are added in unobservable areas to restore

observability.

no effect on estimated states

The EHV network is more observable than HV network.

pair measurement s ( P,Q) in EHV sometimes not in HV

The percentage of observable nodes varies from 80% to 92%.





Computing algorithms :

For real time : A classical L2 cost function is minimized using Gauss-Newton

algorithm

For off line data validation : A M-estimation function is minimized using a trust

region method based on Luvember-Marquardt algorithm.

Estimation of OLTC taps, there are two steps :

First step : ratios of transformers are considered as continuous variables

Second step : ratios are fixed to the nearest discrete value

For each node, the estimated nodal injection is dispatched among loads and

generators

Maximum values are taken into account

If the estimated nodal injection is greater than the total of maximum values, a fictitious

load is created to balance the s stem.




Bad data detection :

Detection of bad data is based on a 2 test.

If2 test fails, we use normalized residuals to detect bad data

an iterative process deletes one by one bad data and reruns a SE (maximum 10 iterations)

This approach suppose that only measurement may be contaminated by bad

data. This hypothesis is not always satisfied, in this case robust state estimation

helps to find the problem.

We define two kind of robustness:Numerical robustness, it deals with the reduction of divergence

Trust region method

Bad data robustness, which reduce the bad data effect.

M-estimator rather L2 estimator




Visualization

The same tool in :

Real time

Study mode.

we can load a snapshot (green :

observable, red : unobservable)

For each substation, a comparison is

possible between :

Estimated state

Measured state

Figure : The EHV network of RTE (study mode)




Visualization :

Figure 2 : 400kV substation , measured state Figure 3 : 400kV substation , estimated state


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Use of SE in RTE

a. Real time operations :

State estimation builds a coherent state before any contingency analysis.

b. Building of reference base cases :

From 2 to 4 reference cases per day are built, which are used to build forecast casesfor operational planning , for ATC computation, .

We developed a collaborative process between our 7 regional control centers and

our national control center

Building of reference base cases : principles


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Initialization by National Control Center

Import snapshot of Region 1

EHV-HV

Import snapshot of Region 7 EHV-

HV

Merging of 7 regional snapshots (EHV-

HV)

Export state of Region 1 EHV(National)-

HV(regional)

Export state of Region 7 EHV(National)-

HV(regional)

manual validation

(Region 1)

manual validation

(Region 7)

Merging of 7 regional corrected states

(EHV-HV)

Final manual validation by NCC (EHV-HV)

Export final corrected state of Region 1

EHV(National)-HV(regional)

Export final corrected state of Region 7

EHV(National)-HV(regional)

.

.

Building of reference base cases : principles


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Manual Validation based on quality criteria

SE quality criteria :

Number of iterations or divergenceNumber of unobservable nodesRate of redundancyNumber of fictitious loadsPossible inconsistencies between topology and measurementsNumber of critical measurementsNumber of bad data

A change of one these criteria requires an analysis

A global quality index based on these criteria is given to each

reference base case.


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Building of reference base cases : Work Flow monitoring


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Most important challenges

We need to have more coordination between European TSOs, an

European network model is mandatory Hierarchical SE.

The robustness of state estimation :

Still a challenging subject No substation internal measurements transmitted => difficult to detect an erroron topology

A state estimation running at the substation level could improve the situation. Ensuring the consistency between topology and measurements, full coherent

state transmitted (status of switching devices and measurements for example

each 1 sec.).

To improve the measurement system, the worst stage must be

improved first.In our case the first limiting factor is the LAN at substation level ( old protocol

using 8 bits for measurements).

RTE France

Documents

Transcript of RTE France