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ASTM E2481-12

Standard Test Method for Hot Spot Protection Testing of Photovoltaic Modules

Automaticky přeložený název:

Standardní zkušební metoda pro Hot Spot ochranu testování fotovoltaických modulů

NORMA vydána dne 1.12.2012

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Provedení	PDF - okamžité stažení - 1 761.10 Kč Tištěné - 1 761.10 Kč
Dostupnost	SKLADEM
Cena	1 761.10 Kč bez DPH
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Informace o normě:

Označení normy: ASTM E2481-12
Poznámka: NEPLATNÁ
Datum vydání normy: 1.12.2012
Kód zboží: NS-45405
Počet stran: 5
Přibližná hmotnost: 15 g (0.03 liber)
Země: Americká technická norma
Kategorie: Technické normy ASTM

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Kategorie - podobné normy:

Technika sluneční energie

Anotace textu normy ASTM E2481-12 :

Keywords:
solar, energy, photovoltaics, modules, electrical testing, hot spot, ICS Number Code 27.160 (Solar energy engineering)

Doplňující informace

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 (Isc) 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.

4.4 Fig. 1 illustrates the hot-spot effect in a module of a series string of cells, one of which, cell 4.5 By-pass diodes, if present, as shown in 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. 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.

1. Scope

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 non-uniform) 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 and health practices and determine the applicability of regulatory limitations prior to use.

2. Referenced Documents

E772-15(2021)	Standard Terminology of Solar Energy Conversion
E927-19	Standard Classification for Solar Simulators for Electrical Performance Testing of Photovoltaic Devices
E1036-15(2019)	Standard Test Methods for Electrical Performance of Nonconcentrator Terrestrial Photovoltaic Modules and Arrays Using Reference Cells
E1799-12(2023)	Standard Practice for Visual Inspections of Photovoltaic Modules
E1802-12(2023)	Standard Test Methods for Wet Insulation Integrity Testing of Photovoltaic Modules