SAFETY OF PHOTOVOLTAIC MODULES – AN OVERVIEW OF THE SIGNIFICANT
CHANGES RESULTING FROM MAINTENANCE OF IEC 61730 SERIES
Bengt Jaeckel1, Guido Volberg2a, Joerg Althaus2b, Gerhard Kleiss3, Peter Seidel4, Markus Beck5 and Arnd Roth6
1
UL International GmbH, Admiral-Rosendahl-Strasse 9, 63263 Neu-Isenburg (Zeppelinheim), Germany
2a
TÜV Rheinland LGA Products GmbH, Am Grauen Stein, 51105 Köln, Germany
2b
TÜV Rheinland Energie und Umwelt GmbH, Am Grauen Stein, 51105 Köln, Germany
3
SolarWorld AG, Martin-Luther-King-Straße 24, 53175 Bonn, Germany
4
First Solar GmbH, Rheinstraße 4, 55116 Mainz, Germany
5
Siva Power, 2387 Bering Drive, San Jose, CA 95131, United States
6
VDE Prüf- und Zertifizierungsinstitut GmbH, Merianstraße 28, 63069 Offenbach, Germany
ABSTRACT:
Since release of Edition 1 of IEC 61730 series the photovoltaic industry has experienced rapid growth and undergone
a large number of changes. As a result, during the past two years Working Group 2 (WG2) of the technical committee
for Solar Photovoltaic Energy Systems (TC82) of the International Electrotechnical Commission (IEC) invested a
considerable effort in updating the governing PV module safety standards to respond to PV industry needs as well as
reflect technological changes and advances.
In particular, with the revision of IEC 61730 a need to reflect the current understanding of low voltage DC (up to
1,500V d.c.) components and materials used in the construction of PV modules arouse. This includes permitting new
materials and new designs while at the same time complying with international horizontal standards that need to be
met in order to comply with governing national electric codes.
Part 1 of IEC 61730 addresses the minimum requirements for module design while Part 2 deals with the required tests
protocols and test sequences. New tests have been added to Part 2 of Edition 2 as the material requirements
necessitate the confirmation of their properties during PV module operation.
This paper explains the most crucial changes to Edition 1 of IEC 61730 series and shows that most PV modules on
the market today already fulfill the requirements of the second edition. In this context it is important to understand the
concepts of component approvals, insulation coordination, protection against electric shock, overvoltage category,
protection class, material group and pollution degree as well as the resulting voltage limitation conjunction to
minimum clearances (cl) and creepage distances (cr) and distance through insulation (dti) for cemented joints.
Keywords: IEC, IEC 61730, safety, insulation coordination, protection against electric shock, protection class,
pollution degree, cemented joint
1.
INTRODUCTION
In 2013 the globally installed photovoltaic (PV) capacity
reached the 100 GWp milestone. While distributed
generation (DG) of small (≈1 kW - 20 kW) roof top PV
systems still constitutes a significant market share, the
trend in today’s PV systems is to medium (≈100 kW - 1
MW) and increasingly large-scale (> 1MW) installations.
With average PV module sales prices decreasing to the
≈$US0.70/Wp level balance of system (BOS) costs
constitute a far larger portion than in the past. In
particular, labor and cabling dominate BOS costs driving
system designs to increasingly higher system voltages –
in the 1,000 V - 1,500 V range. Higher voltages further
reduce electrical system losses. Such high DC voltages
constitute new challenges for PV system component
designs and materials that need to be addressed in the
relevant standards. As such, maintenance of the pertinent
standards needs to assure compliance with state-of-the-art
knowledge and best practices.
2.
HISTORIC BACKGROUND
The first international standard governing minimum
construction requirements for the safety of photovoltaic
(PV) modules, IEC 61730 Ed. 1, was published in 2004.
Prior national standards were based on commonly
observed field failure modes – most prominently from the
JPL Block Buys I-V (1975-1981) [1], [2]. The main focus
was on crystalline PV modules with solar cells of
typically 500µm thickness. Out of the JPL blocks, UL
1703, and standards specific to several regional
certification laboratories Edition 1 of IEC 61730 was
developed to supplement the type approval standards IEC
61215 and IEC 61646 [3].
The following list summarizes the most important steps
during the development of both standards [1], [2].
1975-1981: JPL ‘Block Buys’ I-V (c-Si)
1986: 1st Edition of UL 1703
1981-1991: ESTI – EU Specifications 501-503
1990: SERI IQT modifications for TF (a-Si)
1993: 2nd Edition of UL 1703
1995-2000: IEEE 1262 – for all PV technologies, a
hybrid between IQT and IEC 61215
2002: 3rd Edition of UL 1703
2004: IEC 61730-1 Edition 1 published
2004: IEC 61730-2 Edition 1 published
2008: Edition 2 of IEC 61730-1 initialized (IEC
document 82/536/MCR)
2012: IEC 61730-1 Edition 1.1 published with reference
corrections and implementation of Amendment 1
2013: ETF-9 decision sheet (DSH 1051) for cemented
joints
Both parts of the IEC 61730 standard series work in
conjunction. Part 1 states the construction and component
requirements for individual applications while Part 2
contains all testing requirements to verify the materials
used and manufacturing processes result in a safe PV
module. A large portion of the related accelerated stress
tests are similar or identical to those from IEC 61215 and
IEC 61646. The rationale of this approach is rooted in the
fact that failure modes and requirements are similar for
both performance and safety aspects. However, IEC
61730 focuses primarily on the safety aspects related to
protection against electric shock as well as fire hazard.
Over the past decade PV module technology changed
significantly, hence, a comprehensive correlation cannot
always be established between past observed field
failures for older module constructions to failures in
accelerated stress tests for newer module types.
To this effect, the newly introduced tests and test
sequences in Edition 2 aim to better represent outdoor
failures with the main focus on assuring the PV module
design is safe.
3.
MOTIVATION
Over the past several years TC 82 WG 2 spend a
significant effort on updating the IEC 61730 series.
Amendments and decision sheets were issued to correct
the most pressing issues. However, the fundamental
problems were not completely resolved. The objective
was to address the latter in a new edition of the standard.
To this end a dedicated project team was formed in 2013
with the task to thoroughly revise and update the standard
and to bring it to the voting stage (CDV) within 2 years.
The following objectives were set:
Align the PV safety standard and its
requirements with horizontal IEC standards
Full implementation of 1,500V system voltage
requirements
Updates related to technology and material
advances such as cemented joints
4.
TERMS AND DEFINITIONS
The new standard series of IEC 61730 requires numerous
key definitions and a detailed understanding of electro
technical horizontal standards. To better comprehend the
underlying concepts of IEC 61730 Ed. 2 the paragraph
below lists several essential definitions. Further detail can
be found in the Terms and Definitions clauses of the
upcoming IEC 61215 Ed.3 and IEC 61730 Ed.2 series.
Distance through Insulation (dti): The distances through
insulation that are required for supplementary, double or
reinforced insulation. Thickness depends on several
parameters and distances are stated in Tables 3 and 4 of
the most recent IEC 61730-1 draft.
Basic insulation: Insulation of hazardous-live-parts which
provides basic protection against electric shock.
Double insulation: Insulation comprising both basic
insulation and supplementary insulation.
Functional insulation: Insulation that is necessary for the
proper functioning of the equipment.
Reinforced insulation: Insulation of hazardous-live-parts
which provides a degree of protection against electric
shock equivalent to double insulation. Reinforced
insulation may comprise several layers that cannot be
tested separately as basic insulation or supplementary
insulation.
Solid insulation: Solid insulating material interposed
between two conductive parts or between conductive
parts and outer accessible parts or surfaces.
Clearances distance (cl): The shortest distance through air
between two conductive parts, or between a conductive
part and an accessible surface.
Creepage distances (cr): The shortest distance along the
surface of the insulating material between two conductive
live parts or between conductive live parts and accessible
parts.
5.
CONCEPTS
FROM
STANDARDS
HORIZONTAL
For over a century the different technical committees
(TC) within IEC have developed a series of fundamental
horizontal standards that apply to several TCs. IEC
defines a horizontal standard as follows:
“Standard on fundamental principles, concepts,
terminology or technical characteristics, relevant to a
number of technical committees and of crucial
importance to ensure the coherence of the corpus of
standardization documents. “
Horizontal standards are assigned by the Standardization
Management Board (SMB) with the purpose of:
Ensuring the coherence of the corpus of
standardization documents,
Avoiding duplication of work and contradictory
requirements,
and are part of IEC Guide 108 “Guidelines for ensuring
the coherency of IEC publications – Application of
horizontal standards” [4].
The next paragraphs review the most important and
fundamental concepts from the horizontal standards that
have to be applied to PV as well.
a. Concept of Insulation Coordination
Insulation coordination was introduced in power system
to arrange the electrical insulation levels of different
components in the electrical power system in such a
manner that the failure of insulators, when occurring, is
confined to the place where it would result in the least
damage of the system and is easy to repair and replace.
This leads to a probability of failure study of all
insulating parts to find the weakest insulation point
nearest to the power source. I.e. the aim of insulation
coordination is to reduce the risk of failure to an
economically and operationally acceptable level of cost
and disturbance of normal operation caused by insulation
failure.
The IEC 60664 series defines and uses the concepts of
insulation coordination [5], [6], [7]. The respective IEC
definition of Insulation coordination is as follows:
Insulation co-ordination [IEV 604-03-08]: The selection
of the electric strength of equipment in relation to the
voltages which can appear on the system for which the
equipment is intended, and taking into account the
service environment and the characteristics of the
available protective devices.
Subsequently the following aspects are essential:
1. What are the voltages that can occur?
! Overvoltages
2. The intended use of the equipment – here the
PV module.
3. Environment and serviceability of the
equipment.
b. Overvoltage Category
The overvoltage category is defined in IEC 60664-1
clause 4.3.3.2 [5]. The concept of overvoltage categories
is used for equipment energized directly from the low
voltage mains. The overvoltage categories have a
probabilistic implication rather than the meaning of
physical attenuation of the transient overvoltage
downstream in the installation.
An overvoltage category is a measure which defines a
condition concerning the transient overvoltage.
Categories I, II, III, and IV are applied for equipment
used in low voltage systems; PV installations need to
comply with these requirements.
Category IV: Equipment for use at the origin of the
installation, e.g. electricity meters.
Category III: Equipment for use in fixed installations and
for cases where the reliability and the availability of the
equipment is subject to special requirements, e.g.
equipment for industrial use with permanent connection
to the fixed installation and that includes PV system.
Category II: Equipment that is energy-consuming
equipment and supplied with power from the fixed
installation. Examples of such equipment are appliances
or other loads within a household. If such equipment is
subjected to special requirements with regard to
reliability and availability, overvoltage category III
applies.
Category I: Equipment for connection to circuits in which
measures are taken to limit transient overvoltage to an
appropriately low level. These measures shall ensure that
the temporary overvoltage that could occur are
sufficiently limited so that their peak value does not
exceed the relevant rated impulse voltage. Equipment of
overvoltage category I cannot be directly connected to
the supply mains. Examples are computer mice or
keyboards.
Overvoltage in general is a voltage in a circuit or part of
it, when it is raised above its upper design limit. The
conditions may be hazardous, but this will depend on the
overvoltage event duration. The overvoltage event can be
transient, a voltage spike, or permanent, leading to a
power surge.
As per the definitions above from IEC 60664 and with
agreement of TC 109 (Insulation co-ordination for lowvoltage equipment) PV modules are Overvoltage
Category III equipment.
c. Concept of Classes: IEC 61140
Protection against electrical shock is achieved by a
combination of the constructional arrangements for the
equipment and device, together with the method of
installation.
Four classes are defined per IEC 61140 [8] and Table 1
below provides a brief overview. For an easier correlation
to application classes used in Edition 1 of IEC 61730 the
table also contains the descriptions from Edition 1.
The fundamental idea behind the classes is to categorize
electronic equipment with respect to their protection
means against electric shock. The following short
definitions introduce the concept which is important for
the understanding of classes in the new edition of IEC
61730-1.
Class 0: Equipment comes with basic insulation as
provision for basic protection and with no provisions for
fault protection.
Class I: Equipment with basic insulation as provision for
basic protection and protective bonding as provision for
fault protection. Exposed-conductive-parts of the
equipment shall be connected to the protective
equipotential bonding terminal.
Class II: Equipment with basic insulation as provision for
basic protection, and supplementary insulation as
provision for fault protection, or alternatively in which
basic and fault protection are provided by reinforced
insulation. Class II equipment must be marked with the
graphical symbol no. 5172 of IEC 60417 (double square)
[9].
Class III: Equipment relying on limitation of voltage to
ELV (extra-low voltage) values as provision for basic
protection and with no provision for fault protection.
Equipment must be designed for a maximum nominal
voltage not exceeding 50 V a.c. or 120 V d.c.. Typically
Class III equipment must be marked with the graphical
symbol no. 5180 of IEC 60417.
How to apply this concept to PV modules:
Modules of Class 0: Class 0 modules have individual
and/or system level electrical outputs at hazardous levels
of voltage, current and power. These modules are
provided with basic insulation only as provision for basic
protection and with no provisions for fault protection. All
conductive components that are not separated from
hazardous live parts by at least basic insulation shall be
treated as if they are hazardous live parts. Due to the
limited safety features of Class 0 modules the application
is limited to areas with restricted access that are protected
from public access by fences or other measures
preventing general access. Such modules are only to be
accessed by persons knowledgeable of the inherent
hazards associated with their use and failure modes.
Accessible conductive parts on a Class 0 module are
intended to be earthed or considered to be at hazardous
potential.
Modules of Class I: These will not be covered in the next
edition of IEC 61730-1. Class I equipment needs special
installation measures for electrically safe operation, the
latter being outside the scope of IEC 61730.
Modules of Class II: Class II modules may have
individual and/or system level electrical outputs at
hazardous levels of voltage, current and power. The
modules must provide outputs with basic insulation as
basic protection, and supplementary insulation as
precaution for fault protection, alternatively reinforced
insulation as basic and supplementary insulation.
Accessible conductive parts must be separated from
hazardous live parts by double or reinforced insulation, or
designed with constructional measures which provide
comparable protection. These modules are intended for
installation where general user access is anticipated. This
can be any kind of PV installation from a standard rooftop application to large MW-type PV power plants (e.g.
access by O&M teams – not necessarily electricians).
Modules of Class III: Representative modules and
series/parallel connections thereof are not allowed to
have electrical ratings greater than 35 V DC, 240 W, and
8 A Isc when tested under standard test conditions. Based
upon the inherently limited electrical output capability of
Class III modules their use, misuse, and failure are
unlikely to result in a risk of electric shock or fire.
Consequently, there are no requirements for construction
or insulation beyond functional insulation. These
modules are intended for installation where general user
access and contact to uninsulated parts is anticipated, e.g.
consumer electronics. These modules are not intended for
use in parallel with other modules or energy sources
unless the combination provides protection from back
feed current and overvoltage protection.
Table 1: Application of equipment in a low-voltage installation from IEC 61140 Table 1 and correlation to
IEC 61730-1 edition 1
Class of
equipment
Class 0
Equipment marking or
instructions
- Only for use in nonconducting
environment; or
- Protected by electrical
separation
Marking of the protective
bonding terminal with
symbol no. 5019 of
IEC 60417
Class I
Conditions for connection of
the equipment
to the installation
Application class
(IEC 61730-1 ed.1)
Description from
IEC 61730-1 ed. 1
B
Application in
restricted access
area
Connect this terminal to the
protective-equipotential
bonding
of the installation
Special installation
measures required
Special installation
measures required
No reliance on installation
protective measures
A
Application in nonrestricted access
area
Connect only to SELV or
PELV systems
C
No restrictions for
protection against
electric shock
Non-conducting environment
Electrical separation provided
for each equipment
individually
or letters PE, or color
combination green/yellow
Marking with symbol no.
5172 of IEC 60417
Class II
Marking with symbol no.
5180 of
IEC 60417
Class III
d. Concept of pollution degree (IEC 60664-1
Clause 4.6)
The micro-environment determines the effect of pollution
on the insulation. The macro-environment, however, has
to be taken into account when considering the microenvironment.
Means may be provided to reduce pollution at the
insulation under consideration by effective use of
enclosures, encapsulation or hermetic sealing. Such
means to reduce pollution may not be effective when the
equipment is subject to condensation. Small clearances
can be bridged completely by pollutants such as solid
particles, dust and water and therefore minimum
clearances are specified where pollution may be present
in the micro-environment.
Generally pollution will become conductive in the
presence of humidity or water. Pollution caused by
contaminated water, soot, metal or carbon dust is
inherently conductive.
To design the product with the required clearance and
creepage distances the micro-climate must be assessed.
Based on present pollutions in the application minimum
requirement for insulation exist. IEC 60664-1 sates four
degrees of pollutions:
Pollution degree 1: No pollution or only dry, nonconductive pollution occurs. The pollution has no
influence.
Pollution degree 2: Only non-conductive pollution occurs
except that occasionally a temporary conductivity caused
by condensation is to be expected.
Pollution degree 3: Conductive pollution occurs or dry
non-conductive pollution occurs which becomes
conductive due to condensation which is to be expected.
Pollution degree 4: Continuous conductivity occurs due
to conductive dust, rain or other wet conditions.
The dimensions for creepage distance cannot be specified
where permanently conductive pollution is present
(pollution degree 4). For temporarily conductive
pollution (pollution degree 3), the surface of the
insulation may be designed to avoid a continuous path of
conductive pollution, e.g. by means of ribs and grooves.
Assessing the micro-climate of PV modules:
PV modules are exposed to a variety of climates with
very different temperature, humidity, rain and irradiance
levels. Based on the definition of pollution degree from
IEC 60664-1 and the knowledge of their installation
location PV modules should be generally considered to
be in a pollution degree 3 micro-environment. This
assessment should result in a very safe PV module due to
the extreme required spacing. Comparing the latter to
requirements for 1,000V system voltage in Edition 1
would nearly quadruple the spacing. Thus, the challenge
is to design PV modules enabling the reduction in
pollution degree.
In case of enclosures having a degree of protection higher
and including IP55 the pollution degree can be directly
reduced to 2 for such components (e.g. inside a PV
module junction box).
For parts enclosed or encapsulated to provide protection
against ingress of dust and moisture, and satisfying the
relevant requirements according to Annex C of IEC
61730-1 Ed. 2, pollution degree 1 or 2 might be readily
applicable to PV modules. Annex C outlines the
application of coatings as an option to reduce pollution
degree. Coatings are commonly used to protect materials
against corrosion. Thin coating layers can also enclose
live parts, but the applicable pollution degree for a
specific live part depends on the coating. E.g. a
permissible coating can encapsulate live parts in such
way that no pollution (dust, moisture) will affect spacing.
Compliance to requirements of Annex D also reduces the
micro environment to pollution degree 1.
e.
Concept of Material group from IEC
60664-1 clause 4.8
IEC 60664-1 [5] defines four material groups as follows:
•
material group I: 600 ≤ CTI; PLC=0
•
material group II: 400 ≤ CTI < 600; PLC=1
•
material group IIIa: 175 ≤ CTI < 400;
•
material group IIIb: 100 ≤ CTI < 175. PLC=4
CTI (comparative tracking index) is determined in
accordance to IEC 60112 [10] using solution A. The CTI
compares the performance of various insulating materials
under test conditions to form tracks or show tracking
induced by high voltages. CTI gives a qualitative
comparison and in the case of insulating materials having
a tendency to form tracks, it also gives a quantitative
comparison. UL746A [11] uses a PLC classification at 0
to 5.
For glass, ceramics or other inorganic insulating
materials which do not track, creepage distances need not
be greater than their associated clearance for the purpose
of insulation coordination.
Based on CTI material test materials are classified into
the different groups and can used appropriately in a PV
module. Materials used today in photovoltaic typically
fall within material groups I and II. For some time now
UL 1703 requires a CTI >250 (PLC=2).
f. Concept of Cemented joints
A new and important concept is that of cemented joints
or parts. The fundamental idea behind the latter is to
reduce spacing while still maintaining insulation
requirements to build a product that does not cause the
risk of electrical shock or represents a fire hazard.
The new edition of IEC 61730 includes this concept as
Annex D and supersedes the ETF-9 decision sheet (DSH
1051) for such joints. The standard clearly states
requirements and a test sequence to test material
combinations for compliance.
Adhesive joints within PV modules are considered
cemented joints and are acceptable as equivalent to
reinforced insulation under consideration of distances
through cemented joints per Tables 3 and 4 of IEC 61730
Edition 2. The following requirements apply:
1. Passing the required tests for qualification as
defined by IEC 61730-2 such as Lap shear test
(MST 36).
2. Electrical and mechanical TI or RTI or RTE
thermal rating for the electrically insulating
adhesive/sealant shall be the higher than 90°C
and the maximal determined module
temperature during temperature test (MST 21).
3. Test voltages for dielectric strength are
increased by a factor of 1.35x.
4. The electrically insulating adhesive/sealant
shall have a volume resistivity of greater than
50 x 106 Ω-cm (dry) and greater than 10 x 106
Ω-cm (wet), with volume resistivity as
measured via ASTM D257IEC 62788-1-2 and
wet/dry conditioning defined as per section 14
of UL 746C.
After the tests there shall be neither cracks nor voids in
the insulating compounds which either by themselves or
in combination reduce the distances through the
cemented joint below the required values.
6.
MAJOR CHANGES
This chapter highlights the most important changes of
IEC 617130 Ed. 2 Part 1 and Part 2.
a. Modifications to IEC 61730 Part 1
Changes to Part 1 bring the standard into compliance
with IEC horizontal standards:
As described previously, IEC provides rules and
definitions for electronic equipment and devices to
protect the user from harm caused by electric shock or
fire hazard. Horizontal standards form the basis for
insulation coordination and must be applied were ever
possible. In contrast to this concept, Edition 1 of IEC
61730-1 was based on best practices from module
manufacturing of the 90’s, no longer applicable today.
Back then modules were primarily assembled via manual
processes as opposed to today’s automated high volume
manufacturing methods. Further cost reduction was
achieved via changes to the materials employed in
module construction. New materials have been
introduced and/or thinner/less material is used.
The insulation requirements for PV modules are now
clearly defined and are based on materials properties (!
material groups, section 5e), location of installation (!
pollution degree ! section 5d) and installation type (!
Class ! section 5c).
While the new standard indeed appears more complex it
draws on the established horizontal standards, complies
with IEC regulations, enables innovative new ways to
apply advanced materials and construction methods, and
can lead to lower costs via reduced spacing.
The following example provides a comparison between
Edition 1 and 2. Two scenarios are discussed: First, a
formally application class A module; now a Class II
module and second, a formally application class B
module; now a Class 0 module. All details are
summarized in Table 2. The same scheme can be applied
for all other options. Note, the example does not use the
concept of cemented joints, but it should be apparent
from the prior discussion that the latter allows further
reduction of spacing.
All materials to be used for insulation have a CTI rating
of >600 and therefor fall under the Material Group I
(MG=I). Based on the installation site and the required
Class (e.g. by national electric code – for this example
Class II) it is assumed that the insulation system must be
treated as pollution degree II (PD=II). Table 3 of Edition
2 provides all spacing requirements. The resulting
module will have a live part – outer surface (touchable) –
spacing of 10mm which is slightly larger than today. But
if it can be proven that the encapsulation system of live
parts reduced the pollution degree to PD=I the spacing
could be reduced to 6.4mm, lower than today.
Table 2: Comparison of two modules classes designed for a system voltage of 1,000V and the impact of
edition 2 on spacing. (PD=Pollution Degree, MG=Material Group)
Application Class /
Class
Requirements of
polymeric materials
serving as support
for live parts
Thickness of
Backsheet/Frontsheet
Clearance
Creepage
Spacing live part to
outer surface
Edition 1
Edition 1
Edition 2
Edition 2
Where to find in
Edition 2
Class A
Class B
II
0
Table 1
Based on
UL746A
Based on
UL746A
CTI>600 for
MG=I
CTI>600 for
MG=I
Section 5.3
CTI>250
(Usys<600V)
Not defined,
results from
partial
discharge
test
8.4mm
(Table 4 in
edition 1)
Section 5.3
CTI>250
(Usys<600V)
Not defined,
results from
partial
discharge
test
4.2mm
(Table 4 in
edition 1)
Annex B
Section 2.1.4.1.
Material groups
V-1
V-1
0.15mm
0.15mm
Table 3 and 4,
1b) Thickness in thin
layers
14.0mm
8.0mm
Table 3 and 4,
1a) Live parts and outer
accessible surfaces
Not defined
and
differently
interpreted
Not defined
and
differently
interpreted
8.4mm
4.2mm
6.4mm for
PD=1
10.0mm for
PD=2 and
MG=I
6.4mm
(PD=1)
or
10.0mm
(PD=2)
3.2mm for
PD=1
5.0mm for
PD=2 and
MG=I
3.2mm
(PD=1)
or
5.0mm
(PD=2)
Another important change to Ed. 2 of IEC 61730-1is the
requirement of component approvals, in particular for
junction boxes, connectors and lead wires.
Junction boxes will be required to be in
compliance with IEC 62790 (82/876/FDIS,
close to publication).
Connectors will be required to be in
compliance with IEC 62852 (82/878/FDIS,
close to publication).
Lead wires will be required to be in compliance
with EN 50618 (FprEN 50618:2014-07, close
to publication – later scheduled to be replaced
by IEC 62930, 20/1492/CD).
The above component approval requirements mirror
standards from other industries of electrical products, and
going forward will simplify the module approval process
as well as assure ease of comparison. In fact, the PV
industry at large is likely already prepared for these new
requirements as similar testing protocols from third
parties were used for years in the absence of such
component standards. It will, however, be necessary for
module manufacturers to request the required component
approvals from their respective suppliers or where this is
not possible switch to approved components.
-
-
-
-
b.
Modifications to IEC 61730 Part 2
The following list gives a brief summary of the changes
made to Part 2 of IEC 61730:
Table 3 and 4,
1a) Live parts and outer
accessible surfaces
MST 05 Durability of markings: Checks for
readability of the markings on the PV module before
and after stress tests.
MST 06 Sharp edge test: All accessible modules
surfaces should be smooth and pose no risk for
injury; verified via test.
MST 13 Continuity test of equipotential bonding:
Test renamed to better reflect its purpose.
MST 23 Fire Test: new reference, also see Appendix
of IEC 61730-2 Ed. 2.
MST 24 Ignitability test: This new test determines the
ignitability of PV modules by direct small flame
impingement under zero impressed irradiance using
vertically oriented test specimens and is based on ISO
11925-2. This is important for all polymeric materials
used in a PV laminate.
MST 33 Screw connections test: Any screw
connection in the module should remain secure. Tests
described in MST 33 look for proper material design,
installation and tightness of screws.
MST 35 Peel test: The purpose of this test is to
provide confidence regarding the durability of the
adhesion between different layers of the photovoltaic
module stack.
MST 36 Lap shear strength test: The purpose of this
test is to provide confidence regarding the durability
of the adhesion between rigid-to-rigid bonded
assemblies (e.g. glass/glass modules) for cemented
joints of the photovoltaic module stack.
-
MST 37 Materials creep test: Validates that the
materials used in the module will not show creep or
lose adhesion when operated at the highest
temperatures that modules normally experience in the
field. In particular the test determines possible creep
between the following interfaces:
o frontsheet to backsheet
o frontsheet or backsheet to directly attached
mounting system (e.g. back rail)
o junction box to backsheet respectively frontsheet
The implementation of new tests is the result of changes
in module manufacturing as well as requirements from
horizontal standards implemented in Part 1 of IEC 61730
Edition 2. Consequently the test flow has been updated
and Figure 1 shows the test flow as of September 2014.
The latest revision includes all comments from national
committees (NCs) that were received based on the draft
distributed to all NCs for the IEC TC 82 WG 2 2014
spring meeting.
7.
SUMMARY
A significant amount of work has been invested in
developing Edition 2 of IEC 61730 over the course of the
past 6 years. Several drafts have been created, modified
or withdrawn. Simultaneously, the fast price reduction of
PV modules not only raised concerns about their quality,
but also about their safety. To better define safety
relevant parameters and to comply with IEC regulation to
use horizontal standards the current draft was developed
employing the concepts of insulation coordination,
Classes, pollution degree and material groups. These new
concepts result in a larger parameter space for PV module
design, but unambiguously state safety relevant
boundaries.
The new material requirements lead to new test
requirements, addressed in Part 2. As opposed to Edition
1, Part 1 of Ed. 2 no longer contains test requirements.
The current draft will be discussed at the 2014 fall
meeting of TC 82 WG2 and it is expected that the final
document can be submitted to IEC central office as CDV
by the end of the year.
8.
REFERENCES
[1] Ross, R. G., et al, “Engineering Sciences and
Reliability”, JPL - Flat-Plate Solar Array Project
(1986)
[2] Osterwald, C. R., et al, “History of Accelerated and
Qualification Testing of Terrestrial Photographic
Modules: A Literature Review”, Progress in
Photovoltaics: Research and Applications, 17 (2009),
11-33
[3] Jaeckel, B., et al, “Combined standard for PV module
design qualification and type approval: New IEC
61215 – series”, 29th European Photovoltaic Solar
Energy Conference – Amsterdam (2014)
[4] IEC Guide 108 “Guidelines for ensuring the
coherency of IEC publications – Application of
horizontal standards.”
[5] IEC 60664-1: Insulation coordination for equipment
within low-voltage systems – Part 1: Principles,
requirements and tests
[6] IEC/TR 60664-2-1: Insulation coordination for
equipment within low-voltage systems – Part 1:
Principles, requirements and tests
[7] IEC 60664-3: Insulation coordination for equipment
within low-voltage systems – Part 3: Use of coating,
potting or molding for protection against pollution
[8] IEC 61140:2001, Protection against electric shock –
Common aspects for installation and Equipment with
Amendment 1 (2004)
[9] IEC 60417: Graphical symbols for use on equipment
–Symbol originals
[10] IEC 60112:2003, Method for the determination of the
proof and the comparative tracking indices of solid
insulating materials
[11] UL 746C: Polymeric Material- Use in Electrical
Equipment Evaluations
Figure 1: IEC 61730-2 Test flow.