IEC TS 62738:2018

Ground-mounted photovoltaic power plants - Design guidelines and recommendations

IEC TS 62738:2018(E) sets out general guidelines and recommendations for the design and installation of ground-mounted photovoltaic (PV) power plants. A PV power plant is defined within this document as a grid-connected, ground-mounted system comprising multiple PV arrays and interconnected directly to a utility’s medium voltage or high voltage grid. Additional criteria is that PV power plants are restricted from access by non-qualified persons and are continuously monitored for safety and protection, either by on-site personnel or by active remote monitoring. Technical areas addressed are those that largely distinguish PV power plants from smaller, more conventional installations, including ground mounted array configurations, cable routing methods, cable selection, overcurrent protection strategies, equipotential bonding over large geographical areas, and equipment considerations. Safety and design requirements are referenced to the applicable requirements of IEC 62548 to address distinct differences relative to the design requirements for residential, commercial and other non-power plant applications.

General Information

• Status: Published
• Publication Date: 14-Aug-2018
• ICS: 27.160 - Solar energy engineering
• Technical Committee: TC 82 - Solar photovoltaic energy systems
• Drafting Committee: WG 3 - TC 82/WG 3
• Current Stage: PPUB - Publication issued
• Start Date: 15-Aug-2018
• Completion Date: 26-Oct-2025

Standards Content (Sample)

IEC TS 62738 ®
Edition 1.0 2018-08
TECHNICAL
SPECIFICATION
colour
inside
Ground-mounted photovoltaic power plants – Design guidelines and
recommendations
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IEC TS 62738 ®
Edition 1.0 2018-08
TECHNICAL
SPECIFICATION
colour
inside
Ground-mounted photovoltaic power plants – Design guidelines and

recommendations
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160 ISBN 978-2-8322-5909-2

– 2 – IEC TS 62738:2018 © IEC 2018
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 11
4 Compliance with IEC 62548 . 11
5 PV array system configuration . 12
5.1 General . 12
5.2 Earthing configurations . 12
5.2.1 General . 12
5.2.2 Use of un-earthed d.c. circuits . 12
5.2.3 Use of high-ohmic earthed d.c. circuits . 12
5.2.4 Use of functionally earthed d.c. circuits. 12
5.3 Array electrical diagrams . 12
5.3.1 General . 12
5.3.2 Multiple sub-array configurations . 13
5.3.3 Single array configuration . 15
5.3.4 Combiner boxes and string wiring harnesses . 16
5.3.5 Series-parallel configuration . 16
5.4 Energy storage in PV power plants . 17
5.5 Array physical configurations . 17
5.5.1 Fixed tilt arrays . 17
5.5.2 Adjustable tilt arrays . 17
5.5.3 Single axis tracking arrays . 18
5.5.4 Two-axis tracking arrays . 18
5.5.5 Concentrating PV arrays . 18
5.5.6 Central inverter configurations . 18
5.5.7 String or module inverter configurations . 19
5.6 Mechanical design . 20
5.6.1 Mechanical loads on PV structures . 20
5.6.2 Wind . 20
5.6.3 Snow . 20
5.6.4 Thermal expansion . 20
5.6.5 Flooding . 20
5.6.6 Seismic activity . 21
5.6.7 Corrosion . 21
5.6.8 Access. 21
6 Safety issues . 21
6.1 General . 21
6.2 Restricted access . 22
6.2.1 General . 22
6.2.2 Access to components . 22
6.3 Protection against overcurrent . 22
6.3.1 DC overcurrent protection devices . 22
6.3.2 Requirement for string overcurrent protection . 22
6.3.3 String overcurrent protection sizing. 22

6.3.4 PV sub-array and array overcurrent protection . 23
6.4 Protection against the effects of insulation faults . 24
6.5 Protection against effects of lightning and overvoltage . 24
6.5.1 Lightning protection . 24
6.5.2 Protection against overvoltage . 26
6.6 Protection against fire . 26
6.6.1 Earth-fault protection . 26
6.6.2 Protection against arcing currents. 26
7 Selection and erection of electrical equipment . 26
7.1 General . 26
7.2 PV array design voltage . 27
7.2.1 PV array maximum voltage . 27
7.2.2 Considerations due to inverter MPPT voltage window . 27
7.2.3 Considerations due to inverter efficiency . 27
7.3 Component requirements . 27
7.3.1 General . 27
7.3.2 PV combiner boxes . 28
7.3.3 Disconnectors and switch-disconnectors . 29
7.3.4 Cables . 30
7.3.5 Trackers . 37
8 Acceptance. 37
8.1 General . 37
8.2 Monitoring . 37
8.3 Commissioning tests . 37
8.4 Preliminary performance acceptance test . 37
8.5 Final performance acceptance test. 37
9 Maintenance . 38
10 Marking and documentation . 38
10.1 General . 38
10.2 Labelling and identification . 38
10.2.1 General . 38
10.2.2 Labelling of disconnection devices and combiner boxes . 38
10.3 Documentation . 38
11 Medium and high voltage a.c. systems . 39
11.1 General . 39
11.2 Selection of a.c. collection system voltage . 39
11.3 Collection system configurations . 39
11.3.1 General . 39
11.3.2 Radial systems . 39
11.3.3 Loop systems . 40
11.4 Medium or high voltage transformers . 40
11.4.1 Transformer types . 40
11.4.2 Installation . 40
11.4.3 Protection . 41
11.5 Medium or high voltage switchgear and stations . 41
11.5.1 General . 41
11.5.2 Switchgear specifications . 41
11.6 Medium voltage cable . 41

– 4 – IEC TS 62738:2018 © IEC 2018
11.7 Utility interface . 42
12 Auxiliary power systems . 42
13 Communications systems . 42
13.1 General . 42
13.2 Data sampling speed requirements . 42
Annex A (informative) Inverter application considerations in PV power plants . 43
A.1 Advantages and disadvantages of central inverters . 43
A.2 Advantages and disadvantages of string inverters . 43
A.3 Issues affecting inverter size . 44
A.3.1 PV array output . 44
A.3.2 Inverter ratings . 44
A.3.3 Inverter output control requirements . 44
A.3.4 PV power to inverter power ratio (PVIR) . 44
Bibliography . 46

Figure 1 – PV array diagram – multiple parallel string case with array divided into sub-
arrays . 13
Figure 2 – PV array example using a PCE with multiple MPPT d.c. inputs. 14
Figure 3 – PV array using a PCE with multiple d.c. inputs internally connected to a
common d.c. bus . 15
Figure 4 – PV array diagram – multiple parallel string example . 16
Figure 5 – Example power plant with fixed tilt array . 17
Figure 6 – Example layout of power plant central inverter based array . 19
Figure 7 – Example layout of power plant with string inverters . 20
Figure 8 – Example ground plan for equipotential bonding of a PV array field . 25
Figure 9 – Example of above-ground cable tray configurations for PV plants . 32
Figure 10 – Example trench diagram with cables in ducts . 34
Figure 11 – Example trench diagram with direct buried d.c. and communication cables . 35
Figure 12 – Example trench diagram with direct buried medium voltage a.c. and
communication cables . 36

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
GROUND-MOUNTED PHOTOVOLTAIC POWER PLANTS –
DESIGN GUIDELINES AND RECOMMENDATIONS

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
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Technical specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC TS 62738, which is a technical specification, has been prepared by IEC technical
committee 82: Solar photovoltaic energy systems.

– 6 – IEC TS 62738:2018 © IEC 2018
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
82/1291/DTS 82/1374/RVDTS
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 document has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until
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related to the specific publication. At this date, the publication will be
• transformed into an International standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
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INTRODUCTION
This document sets out general guidelines and recommendations for the design and
installation of utility scale ground-mounted photovoltaic (PV) power plants. The focus is
largely on design aspects that differ from those of conventional residential and commercial PV
systems. Power plants are a significant and growing component of the PV market, yet design
methodologies range considerably, partly due to the fact that systems are not accessible to
the public or non-qualified personnel. Overall guidelines are still needed to ensure safe,
reliable, and productive systems.

– 8 – IEC TS 62738:2018 © IEC 2018
GROUND-MOUNTED PHOTOVOLTAIC POWER PLANTS –
DESIGN GUIDELINES AND RECOMMENDATIONS

1 Scope
This document sets out general guidelines and recommendations for the design and
installation of ground-mounted photovoltaic (PV) power plants. A PV power plant is defined
within this document as a grid-connected, ground-mounted system comprising multiple PV
arrays and interconnected directly to a utility’s medium voltage or high voltage grid. Additional
criteria is that PV power plants are restricted from access by non-qualified persons and are
continuously monitored for safety and protection, either by on-site personnel or by active
remote monitoring. Technical areas addressed are those that largely distinguish PV power
plants from smaller, more conventional installations, including ground mounted array
configurations, cable routing methods, cable selection, overcurrent protection strategies,
equipotential bonding over large geographical areas, and equipment considerations.
Safety and design requirements are referenced to the applicable requirements of IEC 62548
to address distinct differences relative to the design requirements for residential, commercial
and other non-power plant applications. In general, existing standards are referenced
wherever possible for uniformity. Emphasis is placed on systems employing d.c. string based
systems using large scale central inverters or 3-phase string inverters, but relevant sections
are also applicable to systems employing a.c. modules or d.c./d.c. converters. Medium
voltage transformers, switchgear, collection systems, substations, utility interconnection,
auxiliary loads, energy storage systems, and communication services are addressed, but
discussion is mostly limited to recommended references to other standards and requirements.
Rooftop-mounted systems, building integrated PV (BIPV) and building applied PV (BAPV) are
not included in the scope of this document. The principles of restricted-access power plants
are not compatible with systems on buildings, which are used for purposes other than power
generation.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements 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 60076-1, Power transformers – Part 1: General
IEC 60076-2, Power transformers – Part 2: Temperature rise for liquid-immersed transformers
IEC 60076-3, Power transformers – Part 3: Insulation levels, dielectric tests and external
clearances in air
IEC 60076-4, Power transformers – Part 4: Guide to the lightning impulse and switching
impulse testing – Power transformers and reactors
IEC 60076-5, Power transformers – Part 5: Ability to withstand short-circuit
IEC 60076-7, Power transformers – Part 7: Loading guide for mineral-oil-immersed power
transformers
IEC 60085, Electrical insulation – Thermal evaluation and designation
IEC 60137, Insulated bushings for alternating voltages above 1000 V
IEC 60183, Guidance for the selection of high-voltage A.C. cable systems
IEC 60228, Conductors of insulated cables
IEC 60255-21-3, Electrical relays – Part 21: Vibration, shock, bump and seismic tests on
measuring relays and protection equipment – Section 3: Seismic tests
IEC 60296, Fluids for electrotechnical applications – Unused mineral insulating oils for
transformers and switchgear
IEC 60364-5-52, Low-voltage electrical installations – Part 5-52: Selection and erection of
electrical equipment – Wiring systems
IEC 60364-5-54, Low-voltage electrical installations – Part 5-54: Selection and erection of
electrical equipment – Earthing arrangements and protective conductors
IEC 60502-1, Power cables with extruded insulation and their accessories for rated voltages
from 1 kV (Um = 1,2 kV) up to 30 kV (Um = 36 kV) – Part 1: Cables for rated voltages of 1 kV
((Um = 1,2 kV) and 3 kV (Um = 3,6 kV)
IEC 60502-2, Power cables with extruded insulation and their accessories for rated voltages
from 1 kV (Um = 1,2 kV) up to 30 kV (Um = 36 kV) – Part 2: Cables for rated voltages from
6 kV (Um = 7,2 kV) up to 30 kV (Um = 36 kV)
IEC 60853 (all parts), Calculation of the cyclic and emergency current rating of cables
IEC 60870-5-104, Telecontrol equipment and systems – Part 5-104: Transmission protocols –
Network access for IEC 60870-5-101 using standard transport profiles
IEC TR 60890, A method of temperature-rise verification of low-voltage switchgear and
controlgear assemblies by calculation
IEC 60947-3:2008, Low-voltage switchgear and controlgear – Part 3: Switches, disconnectors,
switch-disconnectors and fuse-combination units

IEC 60947-3:2008/AMD1:2012
IEC 60947-3:2008/AMD2:2015
IEC 61000-4-2, Electromagnetic compatibility (EMC) – Part 4-2: Testing and measurement
techniques – Electrostatic discharge immunity test
IEC 61215-2, Terrestrial photovoltaic (PV) modules – Design qualification and type approval –
Part 2: Test procedures
IEC 61238-1 (all parts), Compression and mechanical connectors for power cables
IEC 61427-2, Secondary cells and batteries for renewable energy storage – General
requirements and methods of test – Part 2: On-grid applications
IEC 61439-1, Low-voltage switchgear and controlgear assemblies – Part 1: General rules

– 10 – IEC TS 62738:2018 © IEC 2018
IEC 61439-2, Low-voltage switchgear and controlgear assemblies – Part 2: Power switchgear
and controlgear assemblies
IEC 61643-32, Low-voltage surge protective devices – Part 32: Surge protective devices
connected to the d.c. side of photovoltaic installations – Selection and application principles
IEC 61724-1, Photovoltaic system performance – Part 1: Monitoring
IEC TS 61724-2, Photovoltaic system performance – Part 2: Capacity evaluation method
IEC TS 61724-3, Photovoltaic system performance – Part 3: Energy evaluation method
IEC 61850 (all parts), Communication networks and systems for power utility automation
IEC 61936-1, Power installations exceeding 1 kV a.c. – Part 1: Common rules
IEC 62109-1, Safety of power converters for use in photovoltaic power systems – Part 1:
General requirements
IEC 62109-2, Safety of power converters for use in photovoltaic power systems – Part 2:
Particular requirements for inverters
IEC 62271-1, High-voltage switchgear and controlgear – Part 1: Common specifications for
alternating current switchgear and controlgear
IEC 62271-100, High-voltage switchgear and controlgear – Part 100: Alternating current
circuit-breakers
IEC 62271-102, High-voltage switchgear and controlgear – Part 102: Alternating current
disconnectors and earthing switches
IEC 62271-103, High-voltage switchgear and controlgear – Part 103: Switches for rated
voltages above 1 kV up to and including 52 kV
IEC 62271-200, High-voltage switchgear and controlgear – Part 200: AC metal-enclosed
switchgear and controlgear for rated voltages above 1 kV and up to and including 52 kV
IEC TS 62271-210, High-voltage switchgear and controlgear – Part 210: Seismic qualification
for metal enclosed and solid-insulation enclosed switchgear and controlgear assemblies for
rated voltages above 1 kV and up to and including 52 kV
IEC TR 62271-300, High-voltage switchgear and controlgear – Part 300: Seismic qualification
of alternating current circuit-breakers
IEC 62305-2, Protection against lightning – Part 2: Risk management
IEC 62446-1, Photovoltaic (PV) systems – Requirements for testing, documentation and
maintenance – Part 1: Grid connected systems – Documentation, commissioning tests and
inspection
IEC 62446-2, Photovoltaic (PV) systems – Requirements for testing, documentation and
maintenance – Part 2: Grid connected systems – Maintenance of PV systems (to be
published)
IEC 62548:2016, Photovoltaic (PV) arrays – Design requirements

IEC 62817, Photovoltaic systems – Design qualification of solar trackers
IEC 62852, Connectors for DC-application in photovoltaic systems – Safety requirements and
tests
EN 50539-11, Low-voltage surge protective devices – Surge protective devices for specific
application including d.c. – Part 11: Requirements and tests for SPDs in photovoltaic
applications
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 62548 as well as
the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
PV power plant
grid-connected, ground-mounted PV system comprising multiple PV arrays and
interconnected directly to a utility’s medium voltage or high voltage grid
Note 1 to entry: Additional criteria are that PV power plants are restricted from access by non-qualified personnel
and are continuously monitored for safety and protection, either by on-site personnel or by active remote
monitoring.
3.2
electrically skilled person
person with relevant education and experience to enable him or her to perceive risks and to
avoid hazards which electricity can create
3.3
electrically instructed person
person adequately advised or supervised by electrically skilled persons to enable him or her
to perceive risks and to avoid hazards which electricity can create
3.4
ordinary person
person who is neither a skilled person nor an instructed person
3.5
string wiring harness
cable assembly that aggregates the output of multiple PV string conductors along a single
main conductor
Note 1 to entry: The harness may or may not include fusing on the individual string conductors. The wiring
harness typically does not include a disconnect device in line.
4 Compliance with IEC 62548
The design, erection and verification of PV power plants as defined in this document should
generally comply with the requirements of IEC 62548 and its references to the IEC 60364
series.
– 12 – IEC TS 62738:2018 © IEC 2018
Specific exceptions and variations to the requirements of IEC 62548 called out in this
document are permissible due to the restricted access conditions placed on PV power plants.
5 PV array system configuration
5.1 General
This clause discusses PV array earthing, control, layout and mechanical configurations found
in PV power plants.
5.2 Earthing configurations
5.2.1 General
Considerations for earthing a PV array are addressed in this clause. The requirements of
manufacturers of PV modules and manufacturers of power conversion equipment (PCE) to
which the PV array is connected shall be taken into account in determining the allowable or
required system earthing arrangements.
5.2.2 Use of un-earthed d.c. circuits
When installed with a residual current monitoring system and/or with isolation resistance
detection, PV systems with un-earthed d.c. arrays offer robust earth fault protection. A failure
in any cable (positive or negative), causing a short circuit from the cable to an earthed surface
results only in a shift of the array voltage reference from a floating state to an
earth-referenced state. It does not create a closed circuit for fault current to flow, and
therefore does not present a fire hazard. Un-earthed d.c. circuits are also a requirement
where simple separation or isolation from an earthed a.c. system is not provided by the
inverter or a transformer.
5.2.3 Use of high-ohmic earthed d.c. circuits
High-ohmic earthed systems may be used in plants where operators want to achieve some of
the benefits of an un-earthed or floating system while still maintaining an array voltage
reference to ground to prevent potential induced degradation (PID). Resistance values are set
to limit fault current to a target level (below 300 mA for example) in case of a hard fault
occurring on the unreferenced d.c. circuit pole. This significantly reduces the arcing and fire
causing currents that can occur with grounded systems, specifically those without
supplemental high-sensitive ground fault detection.
5.2.4 Use of functionally earthed d.c. circuits
Protective earthing of any of the conductors of the PV array is not permitted. Earthing of one
of the conductors of the PV array for functional reasons is allowed through internal
connections inherent in the PCE or other earth fault protective device if designed and
qualified for this configuration. Functionally earthed d.c. array based systems are sometimes
used to prevent module PID.
5.3 Array electrical diagrams
5.3.1 General
Figure 1 through Figure 4 show the typical array electrical configurations for PV power plants.
Typical power plants employ multiple array-PCE “blocks” resembling the configurations shown
in Figure 1 through Figure 3. Power plants may also employ string inverter configurations as
shown in Figure 4, or module level micro-inverters.

5.3.2 Multiple sub-array configurations
PV arrays in power plants are most often configured with multiple sub-arrays. The sub-arrays
are connected to large central inverters having multiple d.c. inputs, as shown in Figure 2 and
Figure 3, or to PCEs with a single d.c. input via a separate PV array combiner box (refer to
Figure 1). Overcurrent protection and cable sizing within the various sections of the PV
array(s) are dependent on the limiting of any back-fed currents from the PCE and from
parallel connected arrays.
PV array
PV sub-array
P P P
V V V
PV string
cable PV array overcurrent
PV sub-array
P P P
protection device if
V V V
cable
required
(a)
P P P
V V V
P P P
V V V +
Power
PV string
Conversion
combiner box
-
Equipment
PV array
cable
(b)
PV array
Switch-disconnector
P P P
V V V
PV array
PV sub-array
combiner box
disconnection
devices
PV sub-array
PV string
overcurrent
cable
devices
P P P
V V V
(a)
P P P
V V V
P P P
V V V
PV string
combiner box
To other
sub-arrays
Key
Elements that are not required in all cases
Enclosure
Boundary of system or sub-system

IEC
SOURCE: IEC 62548
a) Overcurrent protection devices where required see 6.3.
b) In some systems the PV array cable may not exist and all the PV strings or PV sub-arrays may be terminated
in a combiner box immediately adjacent to or inside the power conversion equipment.
Figure 1 – PV array diagram – multiple parallel
string case with array divided into sub-arrays

– 14 – IEC TS 62738:2018 © IEC 2018
PV section #1
P P P
V V V
PV array
switch-disconnectors
P P P
V V V PCE with multiple MPPT inputs
P P P
V V V
P P P
V V V
d.c. input 1
MPPT 1
d.c. input 2
MPPT 2
P P P d.c. input 3
V V V
MPPT 3
P P P
V V V
Overcurrent protection
P P P
V V V
P P P
Key
V V V
Elements that are not required in all cases
Enclosure
PV section #2
Boundary of system or sub-system
PV Section #3
IEC
SOURCE: IEC 62548
Figure 2 – PV array example using a PCE with multiple MPPT d.c. inputs

PV section #1
P P P
V V V
PV array
Switch-disconnectors
PCE with multiple inputs
P P P
V V V
Common Bus
P P P
V V V
P P P
V V V
P P P
V V V
P P P
V V V
Overcurrent protection
if required
P P P
V V V
P P P
V V V
PV section #2
PV Section #3
IEC
SOURCE: IEC 62548
Figure 3 – PV array using a PCE with multiple d.c. inputs internally
connected to a common d.c. bus
5.3.3 Single array configuration
A single array PCE configuration is shown in Figure 4. This configuration generally applies for
string or small central inverter applications (see also Annex A).

– 16 – IEC TS 62738:2018 © IEC 2018
PV array
PV string overcurrent
protection device if
applicable
(b)
PV string disconnector
if applicable
PV array overcurrent
protection device if
PV PV PV
applicable
(b)
+
Power
PV string
Conversion
cable
PV PV PV -
Equipment
PV array
cable
PV PV PV
(c)
PV PV PV
PV array
Switch-disconnector
PV string combiner
box
PV module PV string
Bypass diode
(a)
Key
Elements that are not required in all cases
Enclosure
Boundary of system or sub-system

IEC
SOURCE: IEC 62548
a) If required bypass diodes are generally incorporated as standard elements of the PV modules by
manufacturers.
b) Overcurrent protection devices where required see 6.3.
c) In some systems the PV array cable may not exist and all the PV strings or PV sub-arrays may be terminated
in a combiner box immediately adjacent to or inside the power conversion equipment.
Figure 4 – PV array diagram – multiple parallel string example
5.3.4 Combiner boxes and string wiring harnesses
Figure 1 through Figure 4 depict typical configurations that include string combiner boxes.
String wire combining functions may also be achieved with string wiring harnesses, which
utilize connectors to aggregate multiple strings along a main conductor. The purpose is to
reduce balance of system components and cost for systems with large numbers of parallel
(especially low-current) strings. The harness main conductors are combined in a sub-array
combiner box with larger fuses (e.g. 20 A to 30 A).
5.3.5 Series-parallel configuration
Deviations to the IEC 62548 requirement for uniform module string lengths are permitted
under engineering supervision if string voltage control devices are employed, such as module
or sub-string d.c. optimizers or converters. Any alternate string configuration shall conform to

the limitations and requirements defined by the device manufacturers as part of their product
installation instructions.
5.4 Energy storage in PV power plants
Energy storage systems incorporating batteries or other storage technologies may be used in
PV power plants to address control or supplemental power requirements by customers,
utilities or network operators. The requirements for energy storage battery systems are not
addressed in this document. These systems tend to be coupled to the PV generators on the
a.c. side, i.e. on the medium or high-voltage network, and therefore do not directly impact the
d.c. array designs. For more information, refer to IEC 61427-2 and future IEC 60364-5-57.
5.5 Array physical configurations
5.5.1 Fixed tilt arrays
Fixed tilt arrays use structures that orient PV modules at an azimuth and tilt angle that is fixed
year-round (see example in Figure 5). Arrays are fixed typically at the site latitude angle +/-
up to 20° to optimize annual generation, but may be tilted at other angles to achieve specific
performance and cost objectives. For example, lower tilt angles in the 5° to 20° range are
sometimes used to reduce wind loading and mounting structure cost, to allow a higher power
density of the plant, or to increase summer energy production if there are tariff incentives to
do so. Lower tilt angles may result in higher soiling losses depending on site conditions and
therefore should be a consideration. Time of day (TOD) incentives may also warrant orienting
the arrays at an azimuth angle other than due south (or north in the southern hemisphere).
Designs should consider the impact of module shading using suitable engineering analysis.
IEC
Figure 5 – Example power plant with fixed tilt array
5.5.2 Adjustable tilt arrays
Adjustable tilt arrays are essentially fixed tilt arrays that can be manually adjusted once or
more per year. The most typical adjustable tilt array uses a higher angle tilt setting for winter
months and a lower angle tilt setting for summer months. The use of adjustable tilt arrays has
historically been uncommon in PV power plants, but more recently there has been an increase
in their use in markets and regions with low
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