(12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (19) World Intellectual Property Organization International Bureau (10) International Publication Number (43) International Publication Date WO 2011/026874 A3 10 March 2011 (10.03.2011) P O P C T

(51) International Patent Classification: (74) Agent: REHBERG HUPPE + PARTNER; Nikolausber- G01R 31/40 (2006.01) ger Weg 62, 37073 Gottingen (DE). (21) International Application Number: (81) Designated States (unless otherwise indicated, for every PCT/EP2010/062829 kind of national protection available): AE, AG, AL, AM, AO, AT, AU, AZ, BA, BB, BG, BH, BR, BW, BY, BZ, (22) International Filing Date: CA, CH, CL, CN, CO, CR, CU, CZ, DE, DK, DM, DO, 1 September 2010 (01 .09.2010) DZ, EC, EE, EG, ES, FI, GB, GD, GE, GH, GM, GT, HN, (25) Filing Language: English HR, HU, ID, IL, IN, IS, JP, KE, KG, KM, KN, KP, KR, KZ, LA, LC, LK, LR, LS, LT, LU, LY, MA, MD, ME, (26) Publication Language: English MG, MK, MN, MW, MX, MY, MZ, NA, NG, NI, NO, NZ, (30) Priority Data: OM, PE, PG, PH, PL, PT, RO, RS, RU, SC, SD, SE, SG, 09169281 .4 2 September 2009 (02.09.2009) EP SK, SL, SM, ST, SV, SY, TH, TJ, TM, TN, TR, TT, TZ, UA, UG, US, UZ, VC, VN, ZA, ZM, ZW. (71) Applicant (for all designated States except US): SMA SOLAR TECHNOLOGY AG [DE/DE]; Sonnenallee 1, (84) Designated States (unless otherwise indicated, for every 34266 (DE). kind of regional protection available): ARIPO (BW, GH, GM, KE, LR, LS, MW, MZ, NA, SD, SL, SZ, TZ, UG, (72) Inventors; and ZM, ZW), Eurasian (AM, AZ, BY, KG, KZ, MD, RU, TJ, (75) Inventors/Applicants (for US only): BETTENWORT, TM), European (AL, AT, BE, BG, CH, CY, CZ, DE, DK, Gerd [DE/DE]; ElfbuchenstraBe 2, 341 19 (DE). EE, ES, FI, FR, GB, GR, HR, HU, IE, IS, IT, LT, LU, LV, KLEIN, Jens [DE/DE]; Nonnenstieg 34, 37075 Gottingen MC, MK, MT, NL, NO, PL, PT, RO, SE, SI, SK, SM, TR), (DE). SCHAFER, Marc [DE/DE]; Am Bachfeld 4, 34233 OAPI (BF, BJ, CF, CG, CI, CM, GA, GN, GQ, GW, ML, Fuldatal (DE). FISCHER, Jochen [DE/DE]; Holzweg 68, MR, NE, SN, TD, TG). 34255 (DE). FREES, Wolfgang [DE/DE]; Published: BaunsbergstraBe 22, 3413 1 Kassel (DE). VICTOR, Mat¬ thias [DE/DE]; Am Eichberg 20, 34266 Niestetal (DE). — with international search report (Art. 21(3))

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(54) Title: STRING FAILURE MONITORING (57) Abstract: A method of monitoring a plurality of strings (1) of a photovoltaic system (4) connected to a power inverter (3) comprises the steps of: measuring current values of currents which flow from the individual strings (1) to the power inverter (3); determining a reference cur rent value from each plurality of contemporaneously meas ured current values; standardising the current values to the reference current value determined for the respective plural ity of contemporaneously measured current values; and ana lysing long-term courses of the standardised current values of the currents which have flowed from the individual strings (1) within representative time periods by comparison with comparison values established for the individual strings (1). The step of analysing comprises: updating the comparison values using the standardised currents such that a long-term alteration of the standardised current values of one individual strings (1) in an direction results in an altera tion of the comparison value established for that same one of the individual strings (1) in the same direction; determin ing differences between the standardised current values and the updated comparison values; continuously calculating a 00 sum of the differences determined for each individual string (1); continuously comparing the sum with a limit value for the respective individual string (1); and indicating a failure o Fig. 1 of an individual string, if the sum exceeds the limit value. o w o 2011/026874 A3 1I 11 II I 1 Illlll I III III I II Hill III II before the expiration of the time limit for amending the e P ' Internationa searc^report^ claims and to be republished in the event of receipt of " amendments (Rule 48.2(h)) A . CLASSIFICATION O F SUBJECT MATTER INV. G01R31/40 ADD.

According to International Patent Classification (IPC) o r t o both national classification and IPC

B . FIELDS SEARCHED Minimum documentation searched (classification system followed by classification symbols) G01R

Documentation searched other than minimum documentation to the extent that such documents are included in the fields searched

Electronic data base consulted during the international search (name of data base and, where practicable, search terms used)

EPO-Internal , WPI Data, INSPEC

C . DOCUMENTS CONSIDERED T O B E RELEVANT

Category* Citation of document, with indication, where appropriate, of the relevant passages Relevant to claim No.

EP 0 677 749 A (CANON KK [ P] ) 1-17 18 October 1995 (1995-10-18) ci ted i n the appl i cati on col umn 10, l i ne 36 - col umn 11 , l i ne 50; f i gures 1,6, 12

EP 1 223 431 A (OTRONIC GMBH & CO KG [DE] ) 1-17 17 July 2002 (2002-07-17) paragraph [0009] ; f i gure 1

US 2004/056648 Al (MATSUYAMA JINSH0 [ P] ) 25 March 2004 (2004-03-25) paragraphs [0135] , [0136] ; f i gure 4

□ Further documents are listed in the continuation of Box C . See patent family annex.

* Special categories of cited documents : "T" later document published after the international filing date o r priority date and not in conflict with the application but cited to understand "A" document defining the general state of the art which is not considered the principle o r theory underlying the invention to be of particular relevance "E" earlier application o r patent but published o n o r after the international "X" document of particular relevance; the claimed invention cannot be filing date considered novel o r cannot b e considered to involve a n inventive "L" documentwhich may throw doubts o n priority claim(s) orwhich is step when the document is taken alone cited to establish the publication date of another citation o r other "Y" document of particular relevance; the claimed invention cannot be special reason (as specified) considered to involve a n inventive step when the document is "O" document referring to a n oral disclosure, use, exhibition o r other combined with one o r more other such documents, such combination means being obvious to a person skilled in the art "P" document published prior to the international filing date but later than the priority date claimed "&" document member of the same patent family

Date of the actual completion of the international search Date of mailing of the international search report

13 February 2013 22/02/2013

Name and mailing address of the ISA/ Authorized officer European Patent Office, P.B. 5818 Patentlaan 2 N L - 2280 HV Rijswijk Tel. (+31-70) 340-2040, Fax: (+31-70) 340-3016 Kol l , Hermann Patent document Publication Patent family Publication cited in search report date member(s) date

EP 0677749 A 18-10-1995 CN 1124847 A 19-06-1996 EP 0677749 A2 18-10-1995 P 2874156 B2 24-03-1999 P 7334767 A 22-12-1995

EP 1223431 A 17 -07 -2002 NONE

US 2004056648 Al 25 -03 -2004 J P 2004134748 A 3 -04 -2004 US 2004056648 Al 25 -03 -2004