Method and device for detecting electrical arcing in a photovoltaic installation

Patent metadata

Field	Value
Publication number	US-10027279-B2
Application number	US-201414767628-A
Country	US
Kind code	B2
Filing date	Feb 21, 2014
Priority date	Feb 22, 2013
Publication date	Jul 17, 2018
Grant date	Jul 17, 2018

Abstract

Method for detecting an electric arc in a photovoltaic installation, which includes measurement (E6) of voltage values at at least one site of the electrical circuit of the photovoltaic installation; digitization (E8) of the measured voltage values so as to form voltage data; formation (E11) of a window of n recent digitized voltage data; computation (E12) of a test value associated with the said window of the n voltage data; analysis (E13) of a test vector comprising m test values associated with m recent windows generating a quantity arising from this analysis representative of a risk of electric arc; comparison (E15) of this quantity arising with at least one threshold so as to deduce therefrom the presence or otherwise of an electric arc within the photovoltaic installation.

First claim

The invention claimed is:

1. Method for making a photovoltaic installation safe by detecting an electric arc in the photovoltaic installation, comprising:
measuring voltage values at at least one site of the electrical circuit of the photovoltaic installation;
digitizing the measured voltage values so as to form voltage data;
forming a window of n recent digitized voltage data;
computing a test value associated with the window of the n voltage data;
analyzing a test vector comprising m test values associated with m recent windows generating a quantity arising from this analysis representative of a risk of electric arc;
comparing the quantity arising with at least one threshold so as to deduce therefrom a presence or otherwise of an electric arc within the photovoltaic installation, and
if it is estimated that an electric arc exists within the photovoltaic installation, intervening automatically on an electrical circuit of the photovoltaic installation so as to make the photovoltaic installation safe,
wherein the computing of the test value associated with the window of the n voltage data comprises one of the following computations:
computation of a difference between a most recent datum and an oldest datum of the window or computation of a difference between a second most recent datum and a penultimate oldest datum of the window, or computation of any other difference between a more recent datum or a mean of a few more recent data of the window and an older datum or a mean of a few older data of the window; or
computation of a ratio between a more recent datum or a mean of more recent data of the window and an older datum or a mean of older data of the window, and
wherein the computing of the test value associated with the window of the n voltage data comprises performing a comparison of a result of the difference computation or of the ratio between a more recent datum or a mean of more recent data of the window and an older datum or a mean of older data of the window with one or more thresholds and assigning a predefined test value as a function of the comparison.

2. The method according to claim 1 , wherein the forming the window of n digitized voltage data consists in adding a newly digitized datum to the previously formed window and in eliminating an old datum from the window.

3. The method according to claim 2 , wherein the analyzing of the test vector comprises a sum of the test values or a computation of statistical type on the test values of the test vector, so as to obtain as result a quantity representative of a risk of the presence of electric arc.

4. The method according to claim 3 , comprising comparing the quantity with a first threshold so as to deduce therefrom the presence or otherwise of an electric arc of series type and comparing this quantity with a second threshold of opposite sign with respect to the first threshold so as to deduce therefrom the presence or otherwise of an electric arc of parallel type.

5. The method according to claim 1 , wherein the analyzing of the test vector comprises a sum of the test values or a computation of statistical type on the test values of the test vector, so as to obtain as result a quantity representative of a risk of the presence of electric arc.

6. The method according to claim 5 , comprising comparing the quantity with a first threshold so as to deduce therefrom the presence or otherwise of an electric arc of series type and comparing this quantity with a second threshold of opposite sign with respect to the first threshold so as to deduce therefrom the presence or otherwise of an electric arc of parallel type.

7. The method according to claim 5 , wherein the computation of statistical type is a calculation of a mean or a median.

8. The method according to claim 1 , comprising repeating the following actions at each new voltage measurement:
forming a new window by deletion of the oldest voltage datum of the previous window and addition of the most recent voltage datum;
computing the test value of the new window;
devising a new test vector, in which the test value associated with the oldest window is eliminated and the new test value is added; and then
detecting the presence or otherwise of an electric arc on the basis of the new test vector,
if no electric arc is detected, performing an iteration of the previous actions on the basis of a new voltage measurement.

9. The method according to claim 8 , comprising storing the voltage data of the window and the test values of the test vector at each iteration.

10. The method according to claim 8 , comprising detecting the presence or otherwise of an electric arc in real time.

11. The method according to claim 1 , comprising combining the detecting of an electric arc in the photovoltaic installation on the basis of one and the same voltage measurement for two windows comprising a different number of data.

12. The method according to claim 1 , comprising a voltage measurement at a sampling frequency lying between 50 kHz and 10 MHz.

13. Safety device for a photovoltaic installation, comprising:
one or more voltage measurement sensor(s),
a processing unit, and
a communication link linking the one or more voltage measurement sensor(s) and the processing unit,
the processing unit comprising an analogue-digital converter for digitizing the measurements received by the voltage measurement sensor(s), and
an intervention device which operates to make the installation safe in case of electrical arcing, wherein the processing unit is linked to the intervention device so as to be able to communicate with the intervention device,
wherein the processing unit is configured to implement a method for detecting an electric arc in the photovoltaic installation comprising:
measuring voltage values at at least one site of the electrical circuit of the photovoltaic installation;
digitizing the measured voltage values so as to form voltage data;
forming a window of n recent digitized voltage data;
computing a test value associated with the said window of the n voltage data;
analyzing a test vector comprising m test values associated with m recent windows generating a quantity arising from this analysis representative of a risk of electric arc;
comparing the quantity arising with at least one threshold so as to deduce therefrom a presence or otherwise of an electric arc within the photovoltaic installation, and
if it is estimated that an electric arc exists within the photovoltaic installation, instructing automatically the intervention device to intervene on an electrical circuit of the photovoltaic installation so as to make the photovoltaic installation safe,
wherein the computing of the test value associated with the window of the n voltage data comprises one of the following computations:
computation of a difference between a most recent datum and an oldest datum of the window or computation of a difference between a second most recent datum and a penultimate oldest datum of the window, or computation of any other difference between a more recent datum or a mean of a few more recent data of the window and an older datum or a mean of a few older data of the window; or
computation of a ratio between a more recent datum or a mean of more recent data of the window and an older datum or a mean of older data of the window, and
wherein the computing of the test value associated with the window of the n voltage data comprises performing a comparison of a result of the difference computation or of the ratio between a more recent datum or a mean of more recent data of the window and an older datum or a mean of older data of the window with one or m

Assignees

• Commissariat Energie Atomique
• Socomec Sa

Inventors

• Lespinats Sylvain
• Chaintreuil Nicolas
• Kern Christian
• Plissonnier Alexandre

Classifications

• H02H1/0023

  sensing non electrical parameters, e.g. by optical, pneumatic, thermal or sonic sensors · CPC title

• H02H7/20

  for electronic equipment (for converters H02H7/10; for electric measuring instruments G01R1/36; for DC voltage or current semiconductor regulators G05F1/569; for amplifiers H03F1/52; for electronic switching circuits H03K17/08) · CPC title

• G01R31/1263

  of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation · CPC title

• H02S50/10 Primary

  Testing of PV devices, e.g. of PV modules or single PV cells (testing of semiconductor devices during manufacturing {H10P74/00}) · CPC title

• Y02E10/50

  Photovoltaic [PV] energy · CPC title