With the continuous increase in installed capacity of solar photovoltaic power generation, the protection of photovoltaic arrays has received increasing attention. It is understood that IEC62548 Ed. The CDV (Chairman's voting paper) of 1.0 "Installation and safety requirements for photovoltaic PV generators" has been voted on September 16, 2011 and its CCDV (Draft Circulated as The Committee Draft with Vote is also planned to be released in July this year by the IEC Central Office. That is, the key technical content has been determined and the official standard is expected to be released in the second half of 2012 or 2013. In addition, the photovoltaic fuse standard IEC 60269-6 Ed. A further revision of 1 is also in progress. The birth of the new standard and the revision of the existing standards all reflect the latest technical requirements and reflect the advanced nature. It is worth the attention of engineering and technical personnel to ensure that the selection design is more reasonable and reliable.
IEC 62548 covers all PV generators with power above 50W and open circuit voltage above 30V. The overcurrent protection involved in the IEC62548 standard is summarized as follows:
1. The need for over-current protection: Overcurrents may occur in photovoltaic arrays where short-circuits occur in the photovoltaic panel, photovoltaic junction box, or in the wiring portion of the photovoltaic panel, and where ground faults occur in the PV array wiring. The fault current in the photovoltaic system cannot be disconnected from the PV array of the over-current protection device, and arcing may occur. For photovoltaic panels and related equipment manufacturers that require over-current protection, protection shall be provided according to their requirements. If the dealer does not specify overcurrent protection, the overcurrent protection must be set in accordance with the requirements of the IEC 62548 standard.
In the photovoltaic fuse standard IEC 60269-6, it is also proposed that the return current generated by the failure of the photovoltaic inverter is within the rated breaking capacity of the photovoltaic fuse, and the photovoltaic fuse can also provide protection against the array cable and the photovoltaic panel. Damage.
2. Selection of over-current protection fuse-links and fuse holders: The lower the temperature, the greater the open-circuit voltage of the photovoltaic panel. Taking into account this feature, the maximum voltage of the PV arrays, PV arrays, PV arrays and photovoltaic panels should be based on the installation site The expected minimum temperature is corrected according to the instructions of the photovoltaic panel manufacturer. If the photovoltaic panel manufacturer does not provide a correction method, the maximum voltage of the photovoltaic array should be determined in accordance with the standard requirements. The correction factors specified in the IEC62548 standard are as follows.
The maximum voltage correction coefficient of single-crystal silicon and polycrystalline silicon photovoltaic panels applied to photovoltaic array protection fuses shall meet the following requirements:
a. The rated voltage is greater than or equal to the maximum voltage obtained from the photovoltaic panel manufacturer's instructions or the above table according to the expected minimum temperature at the installation site;
b. DC fuse body;
c. Rated breaking capacity not less than the fault current from the PV array, and other connected power sources such as batteries, generators, and the grid, if any;
d. Models that conform to IEC60269-6 and are suitable for PV over-current and short-circuit protection.
The fuse support used in PV array protection should meet the following requirements:
a. The rated voltage is greater than or equal to the maximum voltage obtained from the photovoltaic panel manufacturer's instructions or the above table according to the expected minimum temperature at the installation site;
b. Rated current greater than or equal to the rated current of the corresponding fuse body;
c. The protection level suits the installation site and is not lower than IP 2X.
3. The selection of the rated current of the over-current protection fuse-links and the installation position requirements, etc. For the protection of the PV string, the fuse should be installed at the position where the PV string wires are connected to the PV array sub-array wires, such as the sub-array confluence box and other PV combiner box positions. The negative electrode position must be installed as shown in the schematic diagram of the following photovoltaic system. The rated current of the fuse-link shall be within the range of 1.4-2.4 ISC-MOD. ISC-MOD refers to the short-circuit current of the photovoltaic panel or photovoltaic string under the standard test conditions and is the specification value specified by the manufacturer of the photovoltaic panel on the product nameplate. It should be noted here that for some photovoltaic panels, the ISC_MOD is higher than the nominal value in the first few weeks or months before the work.
For the protection of PV arrays, the fuses should be installed at the positions where the PV array wires are connected to the PV array wires, such as the photovoltaic array box and other PV connection box positions, and the positive and negative electrode positions must be installed. For example, the following photovoltaic system diagram As shown. The rated current of the fuse-link shall be within the range of 1.25-2.4 ISC S-ARRAY, which refers to the short-circuit current of the PV array under standard test conditions, which is equal to n times the PV string short-circuit current ISC_MOD, n Is the number of photovoltaic strings in parallel in the subarray.
For the protection of the entire PV array, the fuse should be installed at the connection position of the PV array wire and the application circuit wire. It is generally installed between the battery and the battery pack and the charge controller, and is installed as close to the battery position as possible. For example, the following diagram of the PV system As shown, it is used to protect the system and wires to prevent the inflow of fault currents from photovoltaic arrays or other connected power sources, such as batteries or battery packs, at other locations. If the fuse link rating is close to the lower limit selected, then the PV array wires are Both the charging controller and the controller provide protection. At this time, the PV array wire between the PV array and the charging and charging controller does not need to be provided with protection. Similarly, both the positive and negative electrodes need to be installed. The rated current of the fuse link in this position shall be in the range of 1.25-2.4 ISC ARRAY, which refers to the short-circuit current of the PV array under standard test conditions, which is equal to N times the photovoltaic string short-circuit current ISC_MOD. N is the array The total number of photovoltaic strings that are juxtaposed. For large rated currents, there may not be a corresponding fuse specification. Overcurrent protection relays and other overcurrent protection devices are usually used.
Given that the relevant IEC 62548 standards have been basically determined and the IEC 60269-6 standard itself needs to be improved, the IEC has now revised the IEC 60269-6 fuse for photovoltaic system protection published in 2010. The revised manuscript (CD) has been issued to all member countries. The most important changes include two points. One is to modify the rated fuse current and the predetermined non-fuse current of the rated fuse whose rated current is 32 A or less (including 32 A). The fuse link is originally required. When the 1.45 times of the rated current is passed, the fuse shall be blown within 1 hour, and if 1.13 times of the rated current is passed, it shall not be blown within 1 hour. After modification, it shall be blown within 1 hour and pass through 1.35 times of the rated current. 1.05 times the rated current should not be blown within 1 hour. After modification, the IEC specification and the UL specification are almost identical for photovoltaic fuses with rated currents up to 32A. Another point is that in its Appendix BB [Guidelines for Photovoltaic Fuse Protection Photovoltaic Module Strings and Photovoltaic Arrays], a guideline for the selection of the rated current value of the fuse body has been added. Its content is the overcurrent protection rating in the above-mentioned IEC 62548 standard. Current selection method, etc.
The changes in the standards reflect two issues that need attention: First, the design of photovoltaic panels for solar photovoltaic systems will generally not exceed 11A, and the current rating of the fuses that are commonly used in the convergence box of PV systems will not exceed the 20A, the most widely used is in the range of 8-15A, so it belongs to the range of its agreed-upon current and the parameters of the specified non-fuse current to be adjusted. In other words, fuses for protection of photovoltaic strings in the combiner box are required to be disconnected under a smaller fault current condition. The original requirement is that when the fault current is 1.45 times the rated current value of the fuse-link, the fuse-link should be Disconnected within 1 hour, now the IEC hopes that the fault current is 1.35 times of its rated current value, the fuse-link will be broken in one hour, so that the protection of the photovoltaic panel will be more effective, of course, the fuse-link It put forward higher requirements. Therefore, in terms of protection effectiveness and reliability, the fuses in the combiner box should give priority to those cut-off fuses that can be blown within one hour when the current is 1.35 times the rated current value. Now these requirements are higher. The products certified by third-party safety agencies such as UL are PV-xA10 from BUSSMANN and HC10PV from HOLLYLAND.
In order to achieve safer and more reliable protection, in addition to preferentially selecting fuses with a lower agreed-to-fuse current, the choice of the size of the fuse link rating is another issue that must be considered. For fuses used in photovoltaic string protection, UL standards The NFPA 70TM National Electrical Code No. 690 “Solar-PV System†states that the rated current of this fuse-link should be greater than or equal to 1.56Isc. Isc is the maximum short-circuit current at the lowest temperature of the PV string. Here, the fuse-link specification is the UL standard. Photovoltaic fuse-links. For IEC-standard photovoltaic fuse-links, the IEC did not previously have relevant standards for specific regulations. The author of this article proposed that the rated current of IEC photovoltaic fuse-links be selected according to 1.42 Isc, and published in the "Solar Energy" period of 2011.09 "PV array protection "Selection analysis using fuses" article. Now the IEC62548 standard puts forward the safety requirements for photovoltaic array overcurrent protection and makes detailed regulations. Thus, there is a clear guideline for the application of IEC-standard photovoltaic fuses, which will greatly benefit the general use of photovoltaics. The design engineer of the system designs for reference and ensures that the selection design is more reasonable and reliable.
IEC 62548 covers all PV generators with power above 50W and open circuit voltage above 30V. The overcurrent protection involved in the IEC62548 standard is summarized as follows:
1. The need for over-current protection: Overcurrents may occur in photovoltaic arrays where short-circuits occur in the photovoltaic panel, photovoltaic junction box, or in the wiring portion of the photovoltaic panel, and where ground faults occur in the PV array wiring. The fault current in the photovoltaic system cannot be disconnected from the PV array of the over-current protection device, and arcing may occur. For photovoltaic panels and related equipment manufacturers that require over-current protection, protection shall be provided according to their requirements. If the dealer does not specify overcurrent protection, the overcurrent protection must be set in accordance with the requirements of the IEC 62548 standard.
In the photovoltaic fuse standard IEC 60269-6, it is also proposed that the return current generated by the failure of the photovoltaic inverter is within the rated breaking capacity of the photovoltaic fuse, and the photovoltaic fuse can also provide protection against the array cable and the photovoltaic panel. Damage.
2. Selection of over-current protection fuse-links and fuse holders: The lower the temperature, the greater the open-circuit voltage of the photovoltaic panel. Taking into account this feature, the maximum voltage of the PV arrays, PV arrays, PV arrays and photovoltaic panels should be based on the installation site The expected minimum temperature is corrected according to the instructions of the photovoltaic panel manufacturer. If the photovoltaic panel manufacturer does not provide a correction method, the maximum voltage of the photovoltaic array should be determined in accordance with the standard requirements. The correction factors specified in the IEC62548 standard are as follows.
The maximum voltage correction coefficient of single-crystal silicon and polycrystalline silicon photovoltaic panels applied to photovoltaic array protection fuses shall meet the following requirements:
a. The rated voltage is greater than or equal to the maximum voltage obtained from the photovoltaic panel manufacturer's instructions or the above table according to the expected minimum temperature at the installation site;
b. DC fuse body;
c. Rated breaking capacity not less than the fault current from the PV array, and other connected power sources such as batteries, generators, and the grid, if any;
d. Models that conform to IEC60269-6 and are suitable for PV over-current and short-circuit protection.
The fuse support used in PV array protection should meet the following requirements:
a. The rated voltage is greater than or equal to the maximum voltage obtained from the photovoltaic panel manufacturer's instructions or the above table according to the expected minimum temperature at the installation site;
b. Rated current greater than or equal to the rated current of the corresponding fuse body;
c. The protection level suits the installation site and is not lower than IP 2X.
3. The selection of the rated current of the over-current protection fuse-links and the installation position requirements, etc. For the protection of the PV string, the fuse should be installed at the position where the PV string wires are connected to the PV array sub-array wires, such as the sub-array confluence box and other PV combiner box positions. The negative electrode position must be installed as shown in the schematic diagram of the following photovoltaic system. The rated current of the fuse-link shall be within the range of 1.4-2.4 ISC-MOD. ISC-MOD refers to the short-circuit current of the photovoltaic panel or photovoltaic string under the standard test conditions and is the specification value specified by the manufacturer of the photovoltaic panel on the product nameplate. It should be noted here that for some photovoltaic panels, the ISC_MOD is higher than the nominal value in the first few weeks or months before the work.
For the protection of PV arrays, the fuses should be installed at the positions where the PV array wires are connected to the PV array wires, such as the photovoltaic array box and other PV connection box positions, and the positive and negative electrode positions must be installed. For example, the following photovoltaic system diagram As shown. The rated current of the fuse-link shall be within the range of 1.25-2.4 ISC S-ARRAY, which refers to the short-circuit current of the PV array under standard test conditions, which is equal to n times the PV string short-circuit current ISC_MOD, n Is the number of photovoltaic strings in parallel in the subarray.
For the protection of the entire PV array, the fuse should be installed at the connection position of the PV array wire and the application circuit wire. It is generally installed between the battery and the battery pack and the charge controller, and is installed as close to the battery position as possible. For example, the following diagram of the PV system As shown, it is used to protect the system and wires to prevent the inflow of fault currents from photovoltaic arrays or other connected power sources, such as batteries or battery packs, at other locations. If the fuse link rating is close to the lower limit selected, then the PV array wires are Both the charging controller and the controller provide protection. At this time, the PV array wire between the PV array and the charging and charging controller does not need to be provided with protection. Similarly, both the positive and negative electrodes need to be installed. The rated current of the fuse link in this position shall be in the range of 1.25-2.4 ISC ARRAY, which refers to the short-circuit current of the PV array under standard test conditions, which is equal to N times the photovoltaic string short-circuit current ISC_MOD. N is the array The total number of photovoltaic strings that are juxtaposed. For large rated currents, there may not be a corresponding fuse specification. Overcurrent protection relays and other overcurrent protection devices are usually used.
Given that the relevant IEC 62548 standards have been basically determined and the IEC 60269-6 standard itself needs to be improved, the IEC has now revised the IEC 60269-6 fuse for photovoltaic system protection published in 2010. The revised manuscript (CD) has been issued to all member countries. The most important changes include two points. One is to modify the rated fuse current and the predetermined non-fuse current of the rated fuse whose rated current is 32 A or less (including 32 A). The fuse link is originally required. When the 1.45 times of the rated current is passed, the fuse shall be blown within 1 hour, and if 1.13 times of the rated current is passed, it shall not be blown within 1 hour. After modification, it shall be blown within 1 hour and pass through 1.35 times of the rated current. 1.05 times the rated current should not be blown within 1 hour. After modification, the IEC specification and the UL specification are almost identical for photovoltaic fuses with rated currents up to 32A. Another point is that in its Appendix BB [Guidelines for Photovoltaic Fuse Protection Photovoltaic Module Strings and Photovoltaic Arrays], a guideline for the selection of the rated current value of the fuse body has been added. Its content is the overcurrent protection rating in the above-mentioned IEC 62548 standard. Current selection method, etc.
The changes in the standards reflect two issues that need attention: First, the design of photovoltaic panels for solar photovoltaic systems will generally not exceed 11A, and the current rating of the fuses that are commonly used in the convergence box of PV systems will not exceed the 20A, the most widely used is in the range of 8-15A, so it belongs to the range of its agreed-upon current and the parameters of the specified non-fuse current to be adjusted. In other words, fuses for protection of photovoltaic strings in the combiner box are required to be disconnected under a smaller fault current condition. The original requirement is that when the fault current is 1.45 times the rated current value of the fuse-link, the fuse-link should be Disconnected within 1 hour, now the IEC hopes that the fault current is 1.35 times of its rated current value, the fuse-link will be broken in one hour, so that the protection of the photovoltaic panel will be more effective, of course, the fuse-link It put forward higher requirements. Therefore, in terms of protection effectiveness and reliability, the fuses in the combiner box should give priority to those cut-off fuses that can be blown within one hour when the current is 1.35 times the rated current value. Now these requirements are higher. The products certified by third-party safety agencies such as UL are PV-xA10 from BUSSMANN and HC10PV from HOLLYLAND.
In order to achieve safer and more reliable protection, in addition to preferentially selecting fuses with a lower agreed-to-fuse current, the choice of the size of the fuse link rating is another issue that must be considered. For fuses used in photovoltaic string protection, UL standards The NFPA 70TM National Electrical Code No. 690 “Solar-PV System†states that the rated current of this fuse-link should be greater than or equal to 1.56Isc. Isc is the maximum short-circuit current at the lowest temperature of the PV string. Here, the fuse-link specification is the UL standard. Photovoltaic fuse-links. For IEC-standard photovoltaic fuse-links, the IEC did not previously have relevant standards for specific regulations. The author of this article proposed that the rated current of IEC photovoltaic fuse-links be selected according to 1.42 Isc, and published in the "Solar Energy" period of 2011.09 "PV array protection "Selection analysis using fuses" article. Now the IEC62548 standard puts forward the safety requirements for photovoltaic array overcurrent protection and makes detailed regulations. Thus, there is a clear guideline for the application of IEC-standard photovoltaic fuses, which will greatly benefit the general use of photovoltaics. The design engineer of the system designs for reference and ensures that the selection design is more reasonable and reliable.
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