IEC TS 62257-7-1:2010

IEC/TS 62257-7-1 ®
Edition 2.0 2010-09
TECHNICAL
SPECIFICATION
colour
inside
Recommendations for small renewable energy and hybrid systems for rural
electrification –
Part 7-1: Generators – Photovoltaic generators

IEC/TS 62257-7-1:2010(E)
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IEC/TS 62257-7-1 ®
Edition 2.0 2010-09
TECHNICAL
SPECIFICATION
colour
inside
Recommendations for small renewable energy and hybrid systems for rural
electrification –
Part 7-1: Generators – Photovoltaic generators

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
XC
ICS 27.160 ISBN 978-2-88912-177-9
– 2 – TS 62257-7-1 © IEC:2010(E)
CONTENTS
FOREWORD.6
INTRODUCTION.8
1 Scope.9
2 Normative references .9
3 Terms and definitions .11
4 Design.17
4.1 Electrical design.17
4.1.1 General .17
4.1.2 Earthing system of a IES or a CES including a PV array.18
4.1.3 Extra low voltage segmentation .20
4.1.4 Earthing system.20
4.1.5 Architectures .28
4.1.6 Series-parallel configuration .32
4.1.7 Batteries in systems .32
4.1.8 Considerations due to prospective fault conditions within a PV array.32
4.1.9 Considerations due to operating temperature .32
4.1.10 Component voltage ratings .33
4.1.11 Performance issues .33
4.2 Mechanical design.34
4.2.1 General .34
4.2.2 Thermal aspects .34
4.2.3 Mechanical loads on PV structures .34
4.2.4 Wind.34
4.2.5 Material accumulation on PV array .34
4.2.6 Corrosion .34
5 Safety issues.35
5.1 General .35
5.2 Protection against electric shock and fire .35
5.3 Protection against overcurrent.35
5.3.1 General .35
5.3.2 Overcurrent protection requirements for PV strings .35
5.3.3 Discrimination.36
5.3.4 Overcurrent protection sizing.36
5.3.5 Overcurrent protection location.37
5.4 Protection against effects of lightning and over-voltage .38
5.4.1 General .38
5.4.2 Protection against direct stroke from lightning .38
5.4.3 Protection against over-voltage .39
6 Selection and erection of electrical equipment.40
6.1 Component requirements .40
6.1.1 PV modules .40
6.1.2 PV array and PV sub-array junction boxes.40
6.1.3 Switching devices.40
6.1.4 Cables.41
6.1.5 Protection devices and cables sizing process .43
6.1.6 Plugs, sockets and couplers .44

TS 62257-7-1 © IEC:2010(E) – 3 –
6.1.7 Fuses .44
6.1.8 By-pass diodes.44
6.1.9 Blocking diodes .45
6.2 Location and installation requirements .45
6.2.1 Disconnecting means .45
6.2.2 PV array production optimization .47
6.2.3 Array voltage .48
6.2.4 Wiring system.48
6.2.5 Surge protective devices .51
6.2.6 Earthing arrangement, protective conductors.51
7 Acceptance .51
7.1 General .51
7.2 Conformance with system general specification.51
7.3 Wiring and installation integrity.51
7.3.1 Compliance with wiring standards.51
7.3.2 Compliance with this standard .51
7.4 Open circuit voltage .51
7.4.1 General .51
7.4.2 Procedure.52
7.5 Open circuit voltage measurements for PV arrays with a large number of
strings .52
7.5.1 General .52
7.5.2 Procedure.52
7.5.3 PV arrays and sub-arrays measurement .52
7.6 Short circuit current measurements .53
7.6.1 General .53
7.6.2 Procedure.53
7.7 Commissioning records .54
8 Operation/maintenance .55
8.1 General .55
8.2 Safety .55
8.3 Operation and maintenance procedures .55
9 Replacement .56
10 Marking and documentation.56
10.1 Equipment marking.56
10.2 Requirements for signs.56
10.3 Labelling of PV array and PV sub-array junction boxes.56
10.4 Labelling of disconnection devices .56
10.4.1 General .56
10.4.2 PV array disconnecting device.56
10.5 Fire emergency information signs.56
10.5.1 General .56
10.6 Documentation .57
Annex A (informative) Examples of commissioning records.58
Annex B (informative) Example of maintenance schedule .61
Annex C (informative) Replacement.63
Annex D (informative) Examples of signs.64
Annex E (informative) Case studies .65

– 4 – TS 62257-7-1 © IEC:2010(E)
Annex F (informative) Double switching in PV array.75
Bibliography.81

Figure 1 – General functional configuration of a PV system .18
Figure 2 – Configuration A – PV alone IES P < 500 W – without inverter – d < 15 m .24
Figure 3 – Configuration G – PV alone IES P < 500 W – without inverter – d > 15 m.24
Figure 4 – Configuration B – PV alone IES P < 500 W – with inverter – d < 15 m .25
Figure 5 – Configuration H – PV alone IES P < 500 W – with inverter – d > 15 m.25
Figure 6 – Configuration C and E – PV alone IES or CES – P < 500 W – with inverter –
d < 15 m .26
Figure 7 – Configuration I and K – PV alone IES or CES – P < 500 W – with inverter –
d > 15 m .26
Figure 8 – Configuration D and F – Hybrid IES or CES – PV generator + inverter and
other generator – d < 15 m.27
Figure 9 – Configuration J and L – Hybrid IES or CES – PV generator + inverter and
other generator – d > 15 m.28
Figure 10 – PV array diagram – single string case .29
Figure 11 – PV array diagram – multi-string case.30
Figure 12 – PV array diagram – multi-string case with array divided into sub-arrays .31
Figure 13 – Needs for overcurrent protection in PV strings .36
Figure 14 – Blocking diode implementation (example).45
Figure 15 – PV string wiring with minimum loop area .49
Figure D.1 – Example of sign required on PV array junction box (10.3) .64
Figure D.2 – Example of sign required adjacent to PV array main switch (10.4.2) .64
Figure D.3 – Example of fire emergency information sign required in main building
switchboard (10.5.1) .64
Figure F.1 – Floating PV array operating at maximum power point.76
Figure F.2 – Floating PV array with single earth fault .77
Figure F.3 – Floating PV array with double earth fault.78
Figure F.4 – Floating PV array with double earth fault.79

Table 1 – Voltage domains for PV arrays .9
Table 2 – Functions fulfilled by the technical room .18
Table 3 – PV system earthing configurations – distance “d” < 15 m.22
Table 4 – PV system earthing configurations – distance “d” > 15 m.23
Table 5 – Requirements for location of overcurrent protective devices according to the
earth configuration.38
Table 6 – Current rating of PV array circuits .42
Table 7 – Disconnecting means requirements in PV array installations .46
Table 8 – Location of disconnection devices according to system configuration, where
required .46
Table A.1 – Verification of PV array general ratings and technical specifications .58
Table A.2 – Verification of compliance with the requirements of IEC 62257-7-1 .59
Case 1: ELV PV array with number of parallel strings < 3 – No battery .65
Case 2: ELV PV array with number of parallel strings < 3 – With battery.67

TS 62257-7-1 © IEC:2010(E) – 5 –
Case 3: ELV array with number of parallel strings > 3 – No battery .69
Case 4: ELV array with number of parallel strings ≥ 3 – With battery .71
Case 5: ELV array with number of parallel strings ≥ 3 – 2 sub arrays – With battery .73

– 6 – TS 62257-7-1 © IEC:2010(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RECOMMENDATIONS FOR SMALL RENEWABLE ENERGY AND
HYBRID SYSTEMS FOR RURAL ELECTRIFICATION –

Part 7-1: Generators –
Photovoltaic generators
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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6) All users should ensure that they have the latest edition of this publication.
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
The main task of IEC technical committees is to prepare International Standards. In
exceptional circumstances, a technical committee may propose the publication of a technical
specification when
– the required support cannot be obtained for the publication of an International Standard,
despite repeated efforts, or
– the subject is still under technical development or where, for any other reason, there is the
future but no immediate possibility of an agreement on an International Standard.
Technical specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC 62257-7-1, which is a technical specification, has been prepared by IEC technical
committee 82: Solar photovoltaic energy systems.

TS 62257-7-1 © IEC:2010(E) – 7 –
This second edition cancels and replaces the first edition issued in 2006 and constitutes a
technical revision.
The main technical changes with regard to the previous edition are the following:
– This new version is focused on small PV generators up to 100 kW .
p
– Case studies are provided.
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
82/583/DTS 82/604/RVC
Full information on the voting for the approval of this technical specification can be found in
the report on voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of the IEC 62257 series, published under the general title, Recommendations
for small renewable energy and hybrid systems for rural electrification can be found on the
IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be be
• transformed into an International standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual edition of this document may be issued at a later date.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 8 – TS 62257-7-1 © IEC:2010(E)
INTRODUCTION
The IEC 62257 series of publications intends to provide to different players involved in rural
electrification projects (such as project implementers, project contractors, project supervisors,
installers, etc.) documents for the setting-up of renewable energy and hybrid systems with
a.c. voltage below 500 V, d.c. voltage below 750 V and power below 100 kVA.
These publications provide recommendations for
– choosing the right system for the right place;
– designing the system;
– operating and maintaining the system.
These publications are focused only on rural electrification concentrated in, but not specific
to, developing countries. They must not be considered as all-inclusive of rural electrification.
The publications try to promote the use of renewable energies in rural electrification. They do
not deal with clean mechanism developments at this time (CO emission, carbon credit, etc.).
Further developments in this field could be introduced in future steps.
This consistent set of publications is best considered as a whole, with different parts
corresponding to items for the safety and sustainability of systems at the lowest possible life-
cycle cost. One of the main objectives of the series is to provide the minimum sufficient
requirements relevant to the field of application, i.e. for small renewable energy and hybrid
off-grid systems.
The purpose of IEC 62257-7-1 is to propose a technical specification for the design and
building of small PV generators (e.g. up to 100 kW ) used in rural electrification.
p
Numerous experts of TC 82 have expressed the opinion that the first edition of IEC/TS 62257-
7-1 is far more general than just the PV array for rural electrification but can also be used for
big PV arrays in big PV power stations.
Therefore it is now necessary to develop a second edition more dedicated and more specific
to rural electrification. It is the purpose of this second edition to specify the general
requirements for the design and the safety of PV generator used in decentralized rural
electrification systems.
TS 62257-7-1 © IEC:2010(E) – 9 –
RECOMMENDATIONS FOR SMALL RENEWABLE ENERGY AND
HYBRID SYSTEMS FOR RURAL ELECTRIFICATION –

Part 7-1: Generators –
Photovoltaic generators
1 Scope
This part of IEC 62257 specifies the general requirements for the design and safety of
generators used in decentralized rural electrification systems.
The earthing systems of the exposed conductive parts and neutral earthing systems which are
considered in this technical specification are those specified in IEC 62257 series for IES (see
IEC 62257-9-3 and IEC 62257-9-4) and CES (IEC 62257-9-2).
This technical specification contains requirements for ELV and LV PV arrays (see Table 1).
Particular attention must be paid to voltage level, as this is important for safety reasons and
has an influence on protective measures and on the skill and ability level of people operating
the systems.
Table 1 – Voltage domains for PV arrays
Voltage domain Voltage
V
Alternating current Smoothed direct current
ELV
U ≤ 50 V U ≤ 120 V
n oc
LV
50 V < U ≤ 1 000 V 120 V < U ≤ 1 500 V
n oc
NOTE ELV limits are provided by IEC 61201.

For the sake of completeness, this technical specification gives requirements for d.c. voltages
below and above 120 V.
The aim is to provide safety and fire protection requirements for:
− uninformed persons, including owner(s)/occupier(s) and users of the premises where
photovoltaic arrays are installed;
− informed workers (e.g. electricians) working on these systems; and
− emergency workers (for example fire fighters).
For installation of PV arrays see IEC 60364-7-712.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60050-811:1991, International Electrotechnical Vocabulary (IEV) – Chapter 811: Electric
traction
– 10 – TS 62257-7-1 © IEC:2010(E)
IEC 60287 (all parts), Electric cables – Calculation of the current rating
IEC 60364 (all parts), Low-voltage electrical installations
IEC 60364-4-41, Low-voltage electrical installations – Part 4-41: Protection for safety –
Protection against electric shock
IEC 60364-5-54, Electrical installations of buildings – Part 5-54: Selection and erection of
electrical equipment – Earthing arrangements, protective conductors and protective bonding
conductors
IEC 60364-7-712:2002, Electrical installations of buildings – Part 7-712: Requirements for
special installations or locations – Solar photovoltaic (PV) power supply systems
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 61140, Protection against electric shock – Common aspects for installation and
equipment
IEC 61215, Crystalline silicon terrestrial photovoltaic (PV) modules − Design qualification and
type approval
IEC 61643-12, Low voltage surge protective devices − Part 12: Surge protective devices
connected to low voltage power distribution systems − Selection and application principles
IEC 61646, Thin−film terrestrial photovoltaic (PV) modules − Design qualification and type
approval
IEC 61730 (all parts), Photovoltaic (PV) module safety qualification
IEC 62257-1, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 1: General introduction to rural electrification
IEC 62257-5, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 5: Protection against electrical hazards
IEC 62257-6, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 6: Acceptance, operation, maintenance and replacement
IEC 62257-9-1, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 9-1: Micropower systems
IEC 62257-9-2, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 9-2: Microgrids
IEC 62257-9-3, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 9-3: Integrated system – User interface
IEC 62257-9-4, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 9-4: Integrated system – User installation
IEC 62305-2, Protection against lightning – Part 2: Risk management
IEC 62305-3, Protection against lightning – Part 3: Physical damage to structures and life
hazard
TS 62257-7-1 © IEC:2010(E) – 11 –
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
available, readily
capable of being reached for inspection, maintenance or repairs without necessitating the
dismantling of structural parts, cupboards, benches or the like
3.2
blocking diode
diode connected in series to module(s), panel(s), sub-arrays and array(s) to block reverse
current into such module(s), panel(s), sub-array(s) and array(s)
3.3
bypass diode
diode connected across one or more cells in the forward current direction to allow the module
current to bypass shaded or broken cells to prevent hot spot or hot cell damage resulting from
the reverse voltage biasing from the other cells in that module
3.4
cable
assembly of one or more conductors and/or optical fibres, with a protective covering and
possibly filling, insulating and protective material
3.5
cable core
the conductor with its insulation but not including any mechanical protective covering
3.6
CES
Collective electrification system
3.7
shield (of a cable)
a surrounding earthed metallic layer to confine the electric field within the cable and/or to
protect the cable from external electrical influence
NOTE Metallic sheaths, armour and earthed concentric conductors may also serve as shields.
[IEC 60050-461:1984, 461-03-04]
3.8
class I equipment
equipment in which protection against electric shock does not rely on basic insulation only,
but which includes an additional safety precaution in that accessible conductive parts are
connected to the protective earthing conductor in the fixed wiring of the electrical installation
in such a way that accessible parts cannot become live in the event of a failure of the basic
insulation
NOTE 1 Class I equipment may have parts with double insulation or parts operating at SELV.
NOTE 2 For equipment intended for use with a flexible cord or cable, this provision includes a protective earthing
conductor as part of the flexible cord or cable.
3.9
class II equipment
equipment in which protection against electric shock does not rely on basic insulation only,
but in which additional safety precautions such as double insulation or reinforced insulation

– 12 – TS 62257-7-1 © IEC:2010(E)
are provided, there being no provision for protective earthing or reliance upon installation
conditions. Such equipment may be one of the following types:
− equipment having durable and substantially continuous enclosures of insulating material
which envelops all metal parts, with the exception of small parts, such as nameplates,
screws and rivets, which are isolated from live parts by insulation at least equivalent to
reinforced insulation. Such equipment is called insulation-encased Class II equipment;
− equipment having a substantially continuous metal enclosure, in which double insulation is
used throughout, except for those parts where reinforced insulation is used, because the
application of double insulation is manifestly impracticable. Such equipment is called
metal-encased Class II equipment;
− equipment that is a combination of the types described in items (a) and (b)
NOTE 1 The enclosure of insulation-encased Class II equipment may form part of the whole of the supplementary
insulation or of the reinforced insulation.
NOTE 2 If the equipment with double insulation or reinforced insulation throughout has an earthing terminal or
earthing contact, it is considered to be of Class I construction.
NOTE 3 Class II equipment may be provided with means for maintaining the continuity of protective circuits,
insulated from accessible conductive parts by double insulation or reinforced insulation.
NOTE 4 Class II equipment may have parts operating at SELV.
3.10
class III equipment
equipment in which protection against electric shock relies on supply at SELV and in which
voltages higher than those of SELV are not generated
NOTE Equipment intended to be operated at SELV and which have internal circuits that operate at a voltage other
than SELV are not included in the classification and are subject to additional requirements.
3.11
double insulation
insulation comprising both basic insulation and supplementary insulation
[IEC 60050-195:1998, 195-06-08]
3.12
earthing
a protection against electric shocks
3.13
extra-low voltage
ELV
voltage not exceeding the relevant voltage limit of band I specified in IEC 60449
[IEC 60050-826:2004, 826-12-30]
NOTE 1 See also IEC 61201.
NOTE 2 Voltage not exceeding 50 V a.c. and 120 V d.c. ripple free are considered to be ELV.
3.14
HMPS
hybrid micropower system: micropower system including generators from different
technologies
3.15
IES
Individual electrification system

TS 62257-7-1 © IEC:2010(E) – 13 –
3.16
I
MOD_REVERSE
the current a module can withstand in the reverse direction to normal without damage to the
module. This rating is obtained from the manufacturer at expected operating conditions
NOTE 1 This current rating does not relate to bypass diode rating. The module reverse current is the current
flowing through the PV cells in the reverse direction to normal current.
NOTE 2 A typical figure for crystalline silicon modules is between 2 and 2,6 times the normal short circuit current
rating ISC MOD.
3.17
I
SC MOD
the short circuit current of a PV module or PV string at Standard Test Conditions (STC), as
specified by the manufacturer in the product specification plate
NOTE As PV strings are a group of PV modules connected in series, the short circuit current of a string is equal
to I .
SC MOD
3.18
I
SC S-ARRAY
the short circuit current of a PV sub-array at Standard Test Conditions (STC), and equal to:
I = I × S
SC S-ARRAY SC STC MOD SA
where S is the number of parallel-connected PV strings in the PV sub-array
SA
3.19
I
SC ARRAY
the short circuit current of the PV array at Standard Test Conditions, and is equal to:
I = I × S
SC ARRAY SC STC MOD A
where S is the total number of parallel-connected PV strings in the PV array
A
3.20
junction box
closed or protected connecting device allowing making of one or several junctions
[IEC 60050-442:1998, 442-08-03]
3.21
live part
conductor or conductive part intended to be energized in normal operation, including a neutral
conductor, but by convention not a PEN conductor or PEM conductor or PEL conductor
NOTE This concept does not necessarily imply a risk of electric shock.
[IEC 60050-195:1998, 195-02-19]
3.22
PEL conductor
conductor combining the functions of both a protective earthing conductor and a line
conductor
[IEC 60050-195:1998, 195-02-14]

– 14 – TS 62257-7-1 © IEC:2010(E)
3.23
protected extra-low voltage
PELV
an extra-low voltage system which is not electrically separated from earth, but which
otherwise satisfies all the requirements for SELV
3.24
PEM conductor
conductor combining the functions of both a protective earthing conductor and a midpoint
conductor
[IEC 60050-195:1998, 195-02-13]
3.25
PEN conductor
conductor combining the functions of both a protective earthing conductor and a neutral
conductor
[IEC 60050-195:1998, 195-02-12]
3.26
power conditioning unit
PCU
a system that converts the electrical power delivered by the PV array into the appropriate
frequency and/or voltage values to be delivered to the load, or stored in a battery or injected
into the electricity grid
3.27
power conditioning unit, isolated
a power conditioning unit where there is electrical separation between the input and output
circuits (e.g. by means of an isolation transformer)
3.28
power conditioning unit, non-isolated
a power conditioning unit where there is no electrical separation between the input and output
circuits
3.29
PV array
a) a mechanically integrated assembly of modules or panels and support structure that forms
a d.c. electricity-producing unit. An array does not include foundation, tracking apparatus,
thermal control, and other such components
[IEC 61836:2007, 3.3.45 a) ]
b) a mechanically and electrically integrated assembly of PV modules, and other necessary
components, to form a d.c. power supply unit
[IEC 60364-7-712:2002, 712.3.4]
NOTE A PV array may consist of a single PV module, a single PV string, or several parallel-connected strings, or
several parallel-connected PV sub-arrays and their associated electrical components. For the purposes of this
standard the boundary of a PV array is the output side of the PV array disconnecting device. Two or more PV
arrays, which are not interconnected in parallel on the generation side of the power conditioning unit, shall be
considered as independent PV arrays.
3.30
PV array cable
the output cable of a PV array that connects the PV array junction box to the PV array
disconnecting device
TS 62257-7-1 © IEC:2010(E) – 15 –
3.31
PV array, earthed
a PV array where one of the poles of the d.c. output circuit is electrically bonded to earth
3.32
PV array, unearthed
a PV array where none of the poles of the d.c. output circuit is electrically bonded to earth
3.33
PV array, floating
a PV array where none of the poles of the d.c. output circuit is electrically bonded to earth and
connected to an application circuit which is either unearthed or double isolated
3.34
PV array, isolated
a PV array where there is at least a simple electrical separation between the PV array output
circuit (d.c. side) and the a.c. system
NOTE A simple electrical separation of power circuits is usually achieved by means of a power transformer.
3.35
PV array junction box
a junction box where all strings of any array are connected
[IEC 60364-7-712:2002, 712.3.5, modified]
3.36
PV array voltage
the PV array voltage is considered to be equal to V under worst case conditions
OC ARRAY
NOTE The open circuit voltage is dependent on the cell temperature and technology.
3.37
PV cell
a) the basic unit of photovoltaic conversion, a semiconductor device that can convert light
directly into electrical energy;
b) the basic photovoltaic device [see IEC 60904-3]
NOTE The preferred term is "solar photovoltaic cell" or "photovoltaic cell", colloquially referred to as a "solar cell".
3.38
PV module
the smallest complete environmentally protected assembly of interconnected cells
[IEC 60904-3]
NOTE Colloquially referred to as a "solar module".
3.39
PV module junction box
an enclosure affixed to a PV module, where the electrical connections to the PV module are
made
3.40
PV string
a circuit of series-connected modules

– 16 – TS 62257-7-1 © IEC:2010(E)
3.41
PV string cable
a cable connecting the modules in a PV string, or connecting the string to a junction box or to
the d.c. terminals of the power conditioning unit
3.42
PV sub-array
the portion of an array that can be considered as a unit
3.43
PV sub-array cable
the output cable of a PV sub-array that carries only the output current of its associated sub-
array in normal operation, and that connects the PV sub-array with the other PV sub-arrays
that constitute the PV array
NOTE PV sub-array cables are only relevant for PV arrays that are divided into sub-arrays (see Figure 7 for
clarification).
3.44
PV sub-array junction box
an enclosure where all the PV strings of a PV sub-array are electrically connected in parallel
and where protection devices may be located if necessary (see Figure 7)
NOTE PV sub-array junction boxes are only relevant for PV arrays that are divided into sub-arrays.
3.45
reinforced insulation
insulation of hazardous-live-parts which provides a degree of protection against electric shock
equivalent to double insulation
NOTE Reinforced insulation may comprise several layers which cannot be tested singly as basic insulation or
supplementary insulation.
[IEC 60050-195:1998, 195-06-09]
3.46
supplementary insulation
independent insulation applied in addition to basic insulation, for fault protection
[IEC 60050-195:1998, 195-06-07]
3.47
simple separation
separation between electric circuits or betwee
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