AU2010101074B4 - Arc Detection In Photovoltaic DC Circuits - Google Patents

Arc Detection In Photovoltaic DC Circuits Download PDF

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Publication number
AU2010101074B4
AU2010101074B4 AU2010101074A AU2010101074A AU2010101074B4 AU 2010101074 B4 AU2010101074 B4 AU 2010101074B4 AU 2010101074 A AU2010101074 A AU 2010101074A AU 2010101074 A AU2010101074 A AU 2010101074A AU 2010101074 B4 AU2010101074 B4 AU 2010101074B4
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signal
frequency range
circuit
method
predetermined
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AU2010101074A
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AU2010101074A4 (en
Inventor
Len Wallace
Luke Williams
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SOLAR DEVELOPMENTS Pty Ltd
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SOLAR DEVELOPMENTS Pty Ltd
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Publication of AU2010101074B4 publication Critical patent/AU2010101074B4/en
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Classifications

    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02HEMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H1/00Details of emergency protective circuit arrangements
    • H02H1/0007Details of emergency protective circuit arrangements concerning the detecting means
    • H02H1/0015Using arc detectors
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00Energy generation through renewable energy sources
    • Y02E10/50Photovoltaic [PV] energy
    • Y02E10/56Power conversion electric or electronic aspects

Description

P/001009 Regulation 3.28 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION FOR AN INNOVATION PATENT Invention Title: ARC DETECTION IN PHOTOVOLTAIC DC CIRCUITS The invention is described in the following statement together with the best method of performing it known to us: Our Reference: 106006 - 2 ARC DETECTION IN PHOTOVOLTAIC DC CIRCUITS The present invention relates to DC circuits and, more particularly to the detection of arcing in solar panel electrical circuitry. BACKGROUND Conventionally, arc detection in electronic circuits has relied on monitoring and evaluating anomalous high frequency signals in these circuits. While detection of 10 characteristic high frequencies has appeared to work particularly in AC circuits, the method is difficult to use and is less effective in DC circuits, and particularly so in DC circuits of solar panels It is an object of the present invention to address or 15 at least ameliorate some of the above disadvantages. Notes 1. The term "comprising" (and grammatical variations thereof) is used in this specification in the inclusive 20 sense of "having" or "including", and not in the exclusive sense of "consisting only of". 2. The above discussion of the prior art in the Background of the invention, is not an admission that any information discussed therein is citable prior art or 25 part of the common general knowledge of persons skilled in the art in any country.

-.3 BRIEF DESCRIPTION OF INVENTION Accordingly, in one broad form of the invention there is provided a method of detecting an electrical arc arising in 5 a solar modular array; said method comprising a. Monitoring for a time-varying electrical signal appearing in said array b. Filtering from said time-varying electrical signal a predetermined frequency range of said 10 time varying signal thereby to provide a sensed time varying signal c. Setting an alarm condition when said sensed time varying signal contains frequency components in said predetermined frequency range which vary in 15 a predetermined magnitude from reference frequency components in said predetermined frequency range Preferably said predetermined frequency range is a low frequency range. 20 Preferably said predetermined frequency range lies in the range 10 Hz to 1000 Hz. Preferably said low frequency range lies in the range 80 Hz to 150 Hz.

Preferably the amplitude of said frequency components vary proportionally to the length of an arc occurring as a fault condition in said array. In a further broad form of the invention there is provided 5 a method of detecting arcing in a DC circuit; said method includes the step of monitoring an anomalous signal within a predetermined low frequency range within said circuit. Preferably said low frequency range lies between 70 and 90HZ. 10 Preferably said low frequency range lies between 90 and 110HZ. Preferably said low frequency range lies between 110 and 150HZ. In yet a further broad form of the invention there is 15 provided an apparatus for detecting arcing in a DC circuit of a photovoltaic array; said apparatus including; (a) a signal discriminator module, (b) a signal conditioning module, (c) an alarm level comparator module, 20 (d) an alarm circuit, and wherein a detected low frequency signal in said circuit between 80 and 150HZ triggers an alarm condition.

- 5 BRIEF DESCRXPTXON OF DRAWINGS Embodiments of the present invention will now be described with reference to the accompanying drawings 5 wherein: Figure 1 is a perspective view of an exemplary solar panel installation on the roof of a dwelling as has now become common in at least the developed world to which embodiments of the present invention may be applied, 10 F'igure 2 is an exemplary solar module array interconnection schematic diagram indicating a typical interconnection arrangement as may be utilised in the array of Figure 1, Figure 3 is a block diagram of a DC arc detector in 15 accordance with a first preferred embodiment of the present invention suitable for use with the arrangement of Figure 2. 20 DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS With reference to Fig. 1 a photovoltaic array of solar panels 10 is typically mounted to a roof or other supporting surface 12. The Direct Current (DC) generated by 25 the array may be fed to a battery storage system (not - 6 shown) or fed directly through appropriate metering and DC/AC inversion, to a mains electricity grid. With reference to Figure 2, a solar module 20 is illustrated in schematic form comprising, in this instance, 5 a plurality of solar modules 21 connected in series groupings 22, 23, 24 (in order to provide the required voltage) and thence connected in parallel to positive bus 25 and negative bus 26 as illustrated (to provide the required current capacity). Individual modules deliver 10 voltage around 30 volts and a maximum current of around 5 amps in best lighting conditions. As previously stated, the current delivery capacity, particularly of the individual modules has a defined upper limit (the effect of internal resistance is quite high) with the behavioural result that 15 even under fault conditions where the module is feeding into a short circuit the current output is severely limited but may well be enough to cause sufficient heating to create a fire hazard whilst not being sufficient to cause fuses or like conventional circuit over current protection 20 to trip or blow. It is important from both a safety aspect as well as efficiency, that any arcing in the DC circuit is detected as soon as possible and an alarm condition generated. Arcing may of course lead to a dangerous fire condition. 25 When an arc is present in the circuit, the voltage is typically between 100 and 500V DC. Should an arc develop, the panels will continue to generate the voltage and current needed to maintain the arc indefinitely while the panels are exposed to sunlight. The danger then lies in the possible breakage of the wiring at the arc, leading to a 5 potential fire ignition condition. Experimentation by the present applicants has shown that an arcing condition in such a circuit is indicated if a low frequency component is superimposed on the high voltage current of the DC supply. These experiments have 10 further shown that this low frequency signal generally lies between 80 and 150HZ. Moreover, it can be shown that the frequency varies in proportion (though not linearly) with the length of the arc. It is noted that the nature of an arc in the circuit 15 of a photovoltaic array differs from that of an arc condition in a normal DC circuit. This difference stems from the fact that the current is substantially constant (given a substantially constant sunlight level). By contrast, in normal DC circuits, when an arc condition 20 develops, from the moment the arcing commences, the current rises as the arc reduces the impedance in the circuit. This difference in the arc characteristic and the associated low frequency system has allowed the design of a monitoring system specific to photovoltaic panels. 25 Figure 3 illustrates in schematic diagram form a DC arc detector circuit 30 in accordance with a first - 8 embodiment of the present invention. The detector 30 is arranged, in this instance, to connect across the positive bus 25 and the negative bus 26 (refer Figure 2) . It may also be arranged to connect across a portion of circuit 5 containing solar modules in respect of which it is desired to detect an internal arcing condition or the like. The detector 30 expects to receive a time varying electrical signal 31 appearing on the bus 25, 26. The high frequency portions of signal 31 are filtered thereof via high 10 frequency bypass filter 32. The relatively low frequency portions thereof are passed via low pass filter 33 thereby to provide a sensed time varying signal 34. Under fault conditions, it is expected that signal 34 will contain low frequency components 35 of amplitude A and frequency F. 15 Level limiter 36 may limit the amplitudes of at least some of the components 35. A signal discriminator 37 and signal conditioner 38 further process the sensed time varying signal 34 and present it to a comparator 39 which compares the frequency components and their amplitudes in the sensed 20 time varying signal 34 with reference components 40. A predetermined comparison difference is recognised as an alarm condition and an alarm signal 41, in this event, is sent to alarm circuit 42. The alarm circuit 42 acts to signal alarm conditions or actuation conditions, for 25 example, to cause an alarm sound or an alarm light; signal over a communications network to a remote monitoring station; cause disconnection or other rectification action on the solar module array 20. The above describes only some embodiments of the present invention and modifications, obvious to those $ skilled in the art, can be made thereto without departing from the scope of the present invention.

Claims (5)

1. A method of detecting an electrical arc arising in a solar modular array; said method comprising 5 a. Monitoring for a time-varying electrical signal appearing in said array b. Filtering from said time-varying electrical signal a predetermined frequency range of said 10 time varying signal thereby to provide a sensed time varying signal c. Setting an alarm condition when said sensed time varying signal contains frequency components in said predetermined frequency range which vary in 15 a predetermined magnitude from reference frequency components in said predetermined frequency range
2. The method of claim 1 wherein said predetermined frequency range is a low frequency range. 20
3. The method of claim 2 wherein said predetermined frequency range lies in the range 10 Hz to 1000 Hz.
4. A method of detecting arcing in a DC circuit; said method includes the step of monitoring an anomalous signal within a predetermined low frequency range 25 within said circuit.
5. Apparatus for detecting arcing in a DC circuit of a photovoltaic array; said apparatus including: (e) a signal discriminator module, (f) a signal conditioning module, 5 (g) an alarm level comparator module, (h) an alarm circuit, and wherein a detected low frequency signal in said circuit between 80 and 200HZ triggers an alarm condition.
AU2010101074A 2010-10-01 2010-10-01 Arc Detection In Photovoltaic DC Circuits Ceased AU2010101074B4 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2010101074A AU2010101074B4 (en) 2010-10-01 2010-10-01 Arc Detection In Photovoltaic DC Circuits

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Application Number Priority Date Filing Date Title
AU2010101074A AU2010101074B4 (en) 2010-10-01 2010-10-01 Arc Detection In Photovoltaic DC Circuits

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AU2010101074A4 AU2010101074A4 (en) 2010-11-04
AU2010101074B4 true AU2010101074B4 (en) 2011-01-27

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Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9853443B2 (en) * 2014-06-26 2017-12-26 Solantro Semiconductor Corp. ARC fault detection and extinguishing

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5327071A (en) * 1991-11-05 1994-07-05 The United States Of America As Represented By The Administrator Of The National Aeronautics & Space Administration Microprocessor control of multiple peak power tracking DC/DC converters for use with solar cell arrays
US6362629B1 (en) * 1997-08-14 2002-03-26 Hendry Mechanical Works Electric arc monitoring systems
US20030066555A1 (en) * 2000-12-04 2003-04-10 Hui Ron Shu Yuen Maximum power tracking technique for solar panels
US20080147335A1 (en) * 2006-12-06 2008-06-19 Meir Adest Monitoring of distributed power harvesting systems using dc power sources

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5327071A (en) * 1991-11-05 1994-07-05 The United States Of America As Represented By The Administrator Of The National Aeronautics & Space Administration Microprocessor control of multiple peak power tracking DC/DC converters for use with solar cell arrays
US6362629B1 (en) * 1997-08-14 2002-03-26 Hendry Mechanical Works Electric arc monitoring systems
US20030066555A1 (en) * 2000-12-04 2003-04-10 Hui Ron Shu Yuen Maximum power tracking technique for solar panels
US20080147335A1 (en) * 2006-12-06 2008-06-19 Meir Adest Monitoring of distributed power harvesting systems using dc power sources

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