ASTM E2481-12

Standard Test Method for Hot Spot Protection Testing of Photovoltaic Modules

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.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 By-pass 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 EffectNote 2—If the modul...
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.

General Information

• Status: Historical
• Publication Date: 30-Nov-2012
• ICS: 27.160 - Solar energy engineering
• Technical Committee: E44 - Solar, Geothermal and Other Alternative Energy Sources
• Drafting Committee: E44.09 - Photovoltaic Electric Power Conversion

Relations

• Replaces: ASTM E2481-08 - Standard Test Method for Hot Spot Protection Testing of Photovoltaic Modules
• Effective Date: 01-Dec-2012
• Referred By: ASTM E2908-12(2023) - Standard Guide for Fire Prevention for Photovoltaic Panels, Modules, and Systems
• Effective Date: 01-Dec-2012

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: E2481 − 12
Standard Test Method for
1
Hot Spot Protection Testing of Photovoltaic Modules
This standard is issued under the fixed designation E2481; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope E1036 Test Methods for Electrical Performance of Noncon-
centrator Terrestrial Photovoltaic Modules and Arrays
1.1 This test method provides a procedure to determine the
Using Reference Cells
ability of a photovoltaic (PV) module to endure the long-term
E1799 Practice for Visual Inspections of Photovoltaic Mod-
effects of periodic “hot spot” heating associated with common
ules
fault conditions such as severely cracked or mismatched cells,
E1802 Test Methods for Wet Insulation Integrity Testing of
single-point open circuit failures (for example, interconnect
Photovoltaic Modules
failures), partial (or non-uniform) shadowing or soiling. Such
effects typically include solder melting or deterioration of the
3. Terminology
encapsulation, but in severe cases could progress to combus-
3.1 Definitions—definitions of terms used in this test
tion of the PV module and surrounding materials.
method may be found in Terminology E772.
1.2 There are two ways that cells can cause a hot spot
3.2 Definitions of Terms Specific to This Standard:
problem; either by having a high resistance so that there is a
3.2.1 hot spot—aconditionthatoccurs,usuallyasaresultof
large resistance in the circuit, or by having a low resistance
shadowing, when a solar cell or group of cells is forced into
area (shunt) such that there is a high-current flow in a localized
reverse bias and must dissipate power, which can result in
region. This test method selects cells of both types to be
abnormally high cell temperatures.
stressed.
4. Significance and Use
1.3 This test method does not establish pass or fail levels.
The determination of acceptable or unacceptable results is
4.1 The design of a photovoltaic module or system intended
beyond the scope of this test method. to provide safe conversion of the sun’s radiant energy into
useful electricity must take into consideration the possibility of
1.4 The values stated in SI units are to be regarded as
partial shadowing of the module(s) during operation. This test
standard. No other units of measurement are included in this
method describes a procedure for verifying that the design and
standard.
construction of the module provides adequate protection
1.5 This standard does not purport to address all of the
against the potential harmful effects of hot spots during normal
safety concerns, if any, associated with its use. It is the
installation and use.
responsibility of the user of this standard to establish appro-
4.2 This test method describes a procedure for determining
priate safety and health practices and determine the applica-
the ability of the module to provide protection from internal
bility of regulatory limitations prior to use.
defects which could cause loss of electrical insulation or
2. Referenced Documents
combustion hazards.
2
2.1 ASTM Standards: 4.3 Hot-spot heating occurs in a module when its operating
E772 Terminology of Solar Energy Conversion
current exceeds the reduced short-circuit current (Isc) of a
E927 Specification for Solar Simulation for Photovoltaic shadowed or faulty cell or group of cells. When such a
Testing
condition occurs, the affected cell or group of cells is forced
into reverse bias and must dissipate power, which can cause
overheating.
1
This test method is under the jurisdiction of ASTM Committee E44 on Solar,
Geothermal and OtherAlternative Energy Sources and is the direct responsibility of
NOTE 1—The correct use of bypass diodes can prevent hot spot damage
Subcommittee E44.09 on Photovoltaic Electric Power Conversion.
from occurring.
Current edition approved Dec. 1, 2012. Published December 2012. Originally
4.4 Fig. 1 illustrates the hot-spot effect in a module of a
approved in 2006. Last previous edition approved in 2008 as E2481-08. DOI:
10.1520/E2481-12.
series string of cells, one of which, cell Y, is partially
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
shadowed. The amount of electrical power dissipated in Y is
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
equal to the product of the module current and the reverse
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. voltage developed across Y. For any irradiance level, when the
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United State
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E2481 − 08 E2481 − 12
Standard Test Method for
1
Hot Spot Protection Testing of Photovoltaic Modules
This standard is issued under the fixed designation E2481; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
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
2
2.1 ASTM Standards:
E772 Terminology of Solar Energy Conversion
E927 Specification for Solar Simulation for Photovoltaic Testing
E1036 Test Methods for Electrical Performance of Nonconcentrator Terrestrial Photovoltaic Modules and Arrays Using
Reference Cells
3
E1328 Terminology Relating to Photovoltaic Solar Energy Conversion (Withdrawn 2012)
E1799 Practice for Visual Inspections of Photovoltaic Modules
E1802 Test Methods for Wet Insulation Integrity Testing of Photovoltaic Modules
3. Terminology
3.1 Definitions—definitions of terms used in this test method may be found in Terminology E772 and Terminology E1328.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 hot spot—a condition that occurs, usually as a result of shadowing, when a solar cell or group of cells is forced into reverse
bias and must dissipate power, which can result in abnormally high cell temperatures.
4. 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.
1
This test method is under the jurisdiction of ASTM Committee E44 on Solar, Geothermal and Other Alternative Energy Sources and is the direct responsibility of
Subcommittee E44.09 on Photovoltaic Electric Power Conversion.
Current edition approved Nov. 1, 2008Dec. 1, 2012. Published December 2008December 2012. Originally approved in 2006. Last previous edition approved in 20062008
as E2481-06.-08. DOI: 10.1520/E2481-08.10.1520/E2481-12.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

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E2481 − 12
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 co
...