1.1 该测试方法提供了一个程序，用于确定光伏（PV）模块承受与常见故障条件相关的周期性“热点”加热的长期影响的能力，如严重开裂或不匹配的电池、单点开路故障（例如互连故障）、部分（或不均匀）遮蔽或脏污。这种影响通常包括焊料熔化或封装的劣化，但在严重情况下可能发展为PV模块和周围材料的燃烧。 1.2 电池有两种方式会导致热点问题:要么是通过高电阻使电路中有大电阻，要么是通过低电阻区域（分流器）使局部区域有大电流。该测试方法选择两种类型的细胞进行应力测试。 1.3 此测试方法不确定合格或不合格等级。 可接受或不可接受结果的确定超出了本试验方法的范围。 1.4 以国际单位制表示的数值应视为标准。本标准中不包括其他计量单位。 1.5 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的使用者有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.6 本国际标准是根据世界贸易组织技术性贸易壁垒委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。 ===意义和用途====== 4.1 旨在将太阳辐射能安全转换为有用电力的光伏模块或系统的设计必须考虑到在运行过程中模块部分遮蔽的可能性。该测试方法描述了一种程序，用于验证模块的设计和构造是否在正常安装和使用过程中提供了充分的保护，以防止热点的潜在有害影响。 4.2 本试验方法描述了一种程序，用于确定模块提供内部缺陷保护的能力，这些内部缺陷可能导致电绝缘损失或燃烧危险。 4.3 当模块的工作电流超过减少的短路电流时，模块会出现热点加热( 我 SC )指有阴影或有缺陷的细胞或细胞组。当这种情况发生时，受影响的电池或电池组被迫反向偏置，必须消耗功率，这可能会导致过热。 注1: 正确使用旁路二极管可以防止发生热点损坏。 4.4 图1 说明了一系列单元格的模块中的热点效应，其中一个单元格 Y ，被部分遮蔽。年消耗的电功率 Y 等于模块电流和两端产生的反向电压的乘积 Y .对于任何辐照度水平，当 Y 等于剩余电压产生的电压( s -1） 模块中的电池，当模块短路时功耗达到最大值。如所示 图1 通过在 Y 具有( s -1） 细胞。 图1 热点效应 4.5 旁路二极管（如果存在），如中所示 图2 ，当模块中的串联串处于反向偏置时开始导通，从而限制了- 输出单元格。 图2 旁路二极管效应 注2: 如果模块不包含旁路二极管，在安装旁路二极管之前，请查看制造商的说明，查看是否建议最大数量的串联模块。如果建议的最大模块数量大于一个，则应使用该数量的串联模块进行热点测试。为了方便起见，可以用恒流电源代替附加模块，以保持指定的电流。 4.6 太阳能电池的反向特性可能变化很大。电池可以在反向性能受电压限制的情况下具有高分流电阻，或者在反向性能受到电流限制的情况中具有低分流电阻。这些类型的细胞中的每一种都可能出现热点问题，但方式不同。 4.6.1 低分流电阻电池: 4.6.1.1 最坏的情况是，当整个单元格（或很大一部分）被遮蔽时，会出现遮蔽条件。 4.6.1.2 通常低分流电阻的电池是这样的，因为局部分流。在这种情况下，由于大量电流在小面积内流动，因此会发生热点加热。因为这是一种局部现象，所以这种类型的电池的性能有很大的分散性。当反向偏置时，具有最低分流电阻的电池在过高温度下工作的可能性很高。 4.6.1.3 由于加热是局部的，低分流电阻电池的热点故障发生得很快。 4.6.2 高分流电阻电池: 4.6.2.1 当小区的一小部分被遮蔽时，会出现最坏的遮蔽条件。 4.6.2.2 高分流电阻电池限制了电路的反向电流，因此会发热。具有最高分流电阻的单元将具有最高的功率耗散。 4.6.2.3 由于电池的整个区域加热均匀，因此电池可能需要很长时间才能加热到造成损坏的程度。 4.6.2.4 高分流电阻单元定义了模块电路中对旁路二极管的需求，其性能特性决定了每个二极管可以保护的单元数量。 4.7 主要的技术问题是如何识别最高和最低的分流电阻单元，然后如何确定这些单元的最坏情况阴影。如果旁路二极管是可拆卸的，则可以通过反向偏置电池串并使用红外相机观察热点来识别具有局部分流的电池。如果模块电路是可访问的，则可以直接监测通过阴影电池的电流。然而，许多PV模块没有可拆卸的二极管或可接近的电路。因此，需要一种可以在这些模块上使用的非侵入性方法。 4.8 所选择的方法是基于对每个单元依次阴影的模块取一组I-V曲线。 图3 显示了样本模块的I-V曲线的结果集。当具有最低分流电阻的单元被遮蔽时，在二极管导通的点处获得具有最高漏电流的曲线。当具有最高分流电阻的单元被遮蔽时，在二极管导通的点处获得具有最低漏电流的曲线。 图3 完全遮蔽不同电池的模块I-V特性 4.9 如果要测试的模块具有并行字符串，则必须分别测试每个字符串。 4.10 该测试方法可作为一系列鉴定测试的一部分，包括性能测量和功能要求的演示。该测试方法的用户有责任规定物理或电气退化的最低验收标准。

1.1 This test method provides a procedure to determine the ability of a photovoltaic (PV) module to endure the long-term effects of periodic “hot spot” heating associated with common fault conditions such as severely cracked or mismatched cells, single-point open circuit failures (for example, interconnect failures), partial (or nonuniform) shadowing, or soiling. Such effects typically include solder melting or deterioration of the encapsulation, but in severe cases could progress to combustion of the PV module and surrounding materials. 1.2 There are two ways that cells can cause a hot spot problem: either by having a high resistance so that there is a large resistance in the circuit, or by having a low resistance area (shunt) such that there is a high current flow in a localized region. This test method selects cells of both types to be stressed. 1.3 This test method does not establish pass or fail levels. The determination of acceptable or unacceptable results is beyond the scope of this test method. 1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 4.1 The design of a photovoltaic module or system intended to provide safe conversion of the sun's radiant energy into useful electricity must take into consideration the possibility of partial shadowing of the module(s) during operation. This test method describes a procedure for verifying that the design and construction of the module provides adequate protection against the potential harmful effects of hot spots during normal installation and use. 4.2 This test method describes a procedure for determining the ability of the module to provide protection from internal defects which could cause loss of electrical insulation or combustion hazards. 4.3 Hot spot heating occurs in a module when its operating current exceeds the reduced short-circuit current ( I SC ) of a shadowed or faulty cell or group of cells. When such a condition occurs, the affected cell or group of cells is forced into reverse bias and must dissipate power, which can cause overheating. Note 1: The correct use of bypass diodes can prevent hot spot damage from occurring. 4.4 Fig. 1 illustrates the hot spot effect in a module of a series string of cells, one of which, cell Y , is partially shadowed. The amount of electrical power dissipated in Y is equal to the product of the module current and the reverse voltage developed across Y . For any irradiance level, when the reverse voltage across Y is equal to the voltage generated by the remaining ( s -1) cells in the module, power dissipation is at a maximum when the module is short-circuited. This is shown in Fig. 1 by the shaded rectangle constructed at the intersection of the reverse I-V characteristic of Y with the image of the forward I-V characteristic of the ( s -1) cells. FIG. 1 Hot Spot Effect 4.5 Bypass diodes, if present, as shown in Fig. 2 , begin conducting when a series-connected string in a module is in reverse bias, thereby limiting the power dissipation in the reduced-output cell. FIG. 2 Bypass Diode Effect Note 2: If the module does not contain bypass diodes, check the manufacturer’s instructions to see if a maximum number of series modules is recommended before installing bypass diodes. If the maximum number of modules recommended is greater than one, the hot spot test should be performed with that number of modules in series. For convenience, a constant current power supply may be substituted for the additional modules to maintain the specified current. 4.6 The reverse characteristics of solar cells can vary considerably. Cells can have either high shunt resistance where the reverse performance is voltage-limited or have low shunt resistance where the reverse performance is current-limited. Each of these types of cells can suffer hot spot problems, but in different ways. 4.6.1 Low Shunt Resistance Cells: 4.6.1.1 The worst case shadowing conditions occur when the whole cell (or a large fraction) is shadowed. 4.6.1.2 Often low shunt resistance cells are this way because of localized shunts. In this case hot spot heating occurs because a large amount of current flows in a small area. Because this is a localized phenomenon, there is a great deal of scatter in performance of this type of cell. Cells with the lowest shunt resistance have a high likelihood of operating at excessively high temperatures when reverse biased. 4.6.1.3 Because the heating is localized, hot spot failures of low shunt resistance cells occur quickly. 4.6.2 High Shunt Resistance Cells: 4.6.2.1 The worst-case shadowing conditions occur when a small fraction of the cell is shadowed. 4.6.2.2 High shunt resistance cells limit the reverse current flow of the circuit and therefore heat up. The cell with the highest shunt resistance will have the highest power dissipation. 4.6.2.3 Because the heating is uniform over the whole area of the cell, it can take a long time for the cell to heat to the point of causing damage. 4.6.2.4 High shunt resistance cells define the need for bypass diodes in the module’s circuit, and their performance characteristics determine the number of cells that can be protected by each diode. 4.7 The major technical issue is how to identify the highest and lowest shunt resistance cells and then how to determine the worst-case shadowing for those cells. If the bypass diodes are removable, cells with localized shunts can be identified by reverse biasing the cell string and using an IR camera to observe hot spots. If the module circuit is accessible the current flow through the shadowed cell can be monitored directly. However, many PV modules do not have removable diodes or accessible electric circuits. Therefore a non-intrusive method is needed that can be utilized on those modules. 4.8 The selected approach is based on taking a set of I-V curves for a module with each cell shadowed in turn. Fig. 3 shows the resultant set of I-V curves for a sample module. The curve with the highest leakage current at the point where the diode turns on was taken when the cell with the lowest shunt resistance was shadowed. The curve with the lowest leakage current at the point where the diode turns on was taken when the cell with the highest shunt resistance was shadowed. FIG. 3 Module I-V Characteristics with Different Cells Totally Shadowed 4.9 If the module to be tested has parallel strings, each string must be tested separately. 4.10 This test method may be specified as part of a series of qualification tests including performance measurements and demonstration of functional requirements. It is the responsibility of the user of this test method to specify the minimum acceptance criteria for physical or electrical degradation.