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: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• 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
• Completion Date: 15-Aug-2018

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 .
...