TCVN 11855-1:2017 Photovoltaic (PV) systems in Vietnam:

Requirements for testing, documentation and maintenance – Part 1: Grid connected systems – Documentation, commissioning tests and inspection.

solar audit vietnam IEC-62446 TCVN-11855

Solar power systems are reliable and require minimum maintenance. There are no moving parts and technology is robust and proven over long time. However, regular inspection is recommended once a year. This is to maintain safety and high efficiency to earn profit from investment. Find out more below.

For residential solar rooftop systems, the solar audit usually consists of site visit with visual inspection and basic electrical testing. Possibly includes thermal scan and washing of solar panels.

However, for large scale commercial solar rooftop and solar park, it requires much more extensive solar inspection procedure following the industry standard IEC 62446-1 (or in Vietnam equivalent: TCVN 11855-1:2017). 

What is solar inspection and audit?
Suntiki inspection solar farm
IEC 62446 on requirements for solar audit and inspection

The standard IEC 62446-1 Photovoltaic (PV) systems defines the minimum inspection criteria and documentation expected for safe operations of grid connected solar power system.

The equivalent technical standard in Vietnam is: TCVN 11855-1:2017 hệ thống quang điện (PV) – yêu cầu thử nghiệm, tài liệu và bảo trì – phần 1: hệ thống nối lưới – tài liệu, thử nghiệm nghiệm thu và kiểm tra

Does my solar energy system need solar inspection?

All solar energy system require regular maintenance check to make sure the solar power system operate in a safe way. However, regular maintenance check is less stringent than solar inspection in accordance with IEC 62446. The industry practice is residential solar power only need regular maintenance check while solar park and C&I commercial rooftop solar is recommended to have solar inspection IEC 62446.

What is the difference between normal maintenance check and solar inspection following IEC 62446?

Small pv system:
only need basic inspection!

Small solar power systems – only basic maintenance check is required. It includes a site visit, inspecting inverter, solar panels, structure, wires and others. This activity is usually limited to visual inspection and basic electrical tests. Also, some contractors offer washing and cleaning the solar panels. However, the documentation is less demanding and maintenance check tasks vary depending on company. This is suitable for small size photovoltaic systems such as residential solar. The reason for limited process is that small system is easier to inspect because it contains only a small number of components to check. And it saves time for the owner also who normally need to be in the house when inspector comes.

Large commercial pv:
Recommend full IEC 62446!

Large commercial systems is recommended for full solar inspection IEC 62446. Here you get a detailed report of the solar energy system condition. There are possibly thousands of components in a large system. Performing ad-hoc inspection can take a lot of time and may not be high quality. But the IEC standard can help to minimize the human error and maximise the inspection efficiency. Performing this work require personnel who are experienced and trained. It requires technical tools, demand extensive field testing, later expert analysis using technical software and possibly return to site again for more testing. Usually the following equipment is needed: special infrared drones, IR camera to evaluate the IV curve, insulation resistance tester, test solar cell with temperature sensor, PV string tester, Pdetector kit etc etc… This is suitable for solar park or commercial rooftop solar systems.

Which type of inspection/ maintenance is currently performed for my solar power system?

You should receive a report after your contractor performs site inspection. That report should contain similar check activities as our Suntiki IEC inspection report. If you have any question about the report you have received, you can always call a solar inspection company to ask for second opinion of the report.

What are the activities in solar inspection? In practice this means inspecting 3 important areas:

  1. Solar panel and related.
  2. Inverter, connection and related.
  3. Low, medium and high voltage equipment, station, switchgear and related (35kV, 110kV/22kV).

Some of the inspection components include:

solar inspection parts

Thermal Inspection: for effective visual inspection of thousands of solar panels. Possibly reaching to areas not easily accessible.

Thermal inspection

Visual Inspection: Test AC and DC circuits, earthing connection, polarity test, open voltage measurements, test to string configurations ….

Electrical testing (iv curve): technical analysis of IV curves.

Visual and electrical inspection
electrical testing and IV curve analysis

Performance testing (pv cell): analysis of actual solar energy production compared to PV test cell installed in same conditions as the system.

solar cell test unit
solar audit documentation requirement

Documentation: Technical analysis, risk mitigation/ repair plan.

We carry out a detailed technical inspection of solar power plant, which includes a comprehensive assessment of the technical condition of individual elements of the photovoltaic system (including solar modules, inverters, control panels, batteries and transformers). Quality control of a solar power plant is carried out under normal operating conditions under load and usually does not require extensive shutdown of equipment. We provide a detailed technical report with an expert opinion and suggestions for troubleshooting. We recommend conducting a scheduled technical inspection of solar power plants twice a year.

Special tools allow us to easily inspect your solar panels and pinpoint a large number of problems. The inclusion of thermal imaging checks in the planned maintenance of the solar plants will help the plant to work safer and increase its overall efficiency. Such an analysis is advisable to obtain more accurate information on the state of the solar modules at your solar power plant.

Solar inspection benefits

Solar inspection – why need the audit? A technical solar inspection will bring the following benefits:

Increase safety. Reduce fire risk. Reduce DC arc risks.

Increase investment profit. Maximise solar power energy production. Reduce electricity bill.

Prevent high cost equipment breakdowns.

Managing warranty claims with equipment suppliers.

+25 years exposed to sun, rain and storms:

Commercial solar energy systems are used for at least 25 years and more. They contain solar panels and wires that are exposed to all weather elements. Damages from the sun’s UV light, corrosion from the rain, physical damages from record windspeed storms, damages from rodents, substandard and reckless installation prioritise schedule more than quality are just a few issues on a long list. You can read more about fire protection standards here.

Equipment degrade over time, but how much?

It is well known any equipment loses its original efficiency over time. And so, when we see reduced pv production or increased electricity bill, how can we know if this is the expected performance or if something is wrong? Technical inspection and audit can provide accurate analysis of real state of operation for solar power plant and commercial rooftop installations C&I.

Lack of photovoltaic technical standard in new industry:

In fact, Vietnam solar energy industry is still very new and until now there are very few technical standards that EPC contractors must follow. And yet Vietnam has installed a record of 19,400 MWp by 2020 to become the ASEAN top installer.

Example where Solar Audit is needed:

In most cases, solar audit will increase the performance of solar power project. However, while accidents are very rare, the solar audit can prevent accidents, fires, building collapse and other quality issues. An extreme example is the Gia Lai solar energy system that caught fire and media attention in 09/2020. A rooftop solar system with 60 solar panels caught fire on the rooftop of Gia Lai Electricity Joint Stock Company.

The head of firefighting department suspect the issue is DC arc discharge from one of the 50 DC wire connections.

Who needs IEC 62446?

House owners – small system – only basic maintenance is needed. 

Property owners with large scale C&I solar panels on rooftop need full IEC-62446

PPA and DPPA investors need full IEC-62446.

  • Owners of solar park or C&I solar commercial rooftops. Not typical for small size residential solar energy projects (but residentials need regular maintenance checks!)
  • Renewable energy investors that manage solar DPPA.
    • Current operating projects:
      • a technical inspection can safeguard the investment and increase customer satisfaction that brings more business.
      • It can also attract potential buyers of the project, thereby releasing cashflow for new opportunities.
      • Prospecting potential pv projects to buy. A solar audit will help determine the operational efficiency of the system before we make an investment.

About the standard IEC 62446 – Technical standard for solar inspection.

IEC 62446-1:2016 Photovoltaic (PV) systems – Requirements for testing, documentation and maintenance – Part 1: Grid connected systems – Documentation, commissioning tests and inspection.

IEC 62446 defines the minimal information and documentation required to be handed over to a customer following the installation of a grid connected PV system.

This standard also describes the minimum commissioning tests, inspection criteria and documentation expected to verify the safe installation and correct operation of the system. The document can also be used for periodic retesting.

It is for use by system designers and installers of grid connected solar PV systems as a template to provide effective documentation to a customer. Include a wide range of system test and inspection regimes to encompass larger and more complex PV systems.

This standard is composed into 2 main parts:

  • System documentation requirements (Clause 4) – This clause details the information that shall be provided, as a minimum, within the documentation provided to the customer following the installation of a grid connected PV system.
  • Verification (Clause 5) – This clause provides the information expected to be provided following initial (or periodic) verification of an installed system. It includes requirements for inspection and testing.

The equivalent standard used for Vietnam is:

Tiêu chuẩn quốc gia TCVN 11855-1:2017 hệ thống quang điện (pv) – yêu cầu thử nghiệm, tài liệu và bảo trì – phần 1: hệ thống nối lưới – tài liệu, thử nghiệm nghiệm thu và kiểm tra

Document Content:


Vị trí:


Công suất điện:


loại/ công nghệ:


Công ty:


Số tài liệu.
































Technical Inspection/ Solar Audit Report

following IEC 62446-1/ TCVN 11855-1:2017





Suntiki Partnership:

Suntiki is

certified REC installer.

Suntiki is

certified distributor.

German brand.


Taiwan brand.

Suntiki in the news …










A: Suntiki Solar Verification Certificate:


PV system verification certificate:

ð      Initial verification.

ð      Periodic verification.







Test Date:


Description of installation:


Rated power: kW DC




Circuits tested:



Contractor’s name and


IEC 60364-6 inspection report reference:


IEC 60364-6 test report reference:


PV array inspection report reference:


PV array test report reference:




I/we being the person(s) responsible for the design, construction, inspection and testing of the electrical installation (as indicated by the signature(s) below), particulars of which are described above, having exercised reasonable skill and care when carrying out the design, construction, inspection and testing, herby certify that the said work for which I/we have been responsible is, to the best of my/our knowledge and belief, in accordance with ………………………………………………..




The extent of liability of the signatory(s) is limited to the work described above:





Next inspection recommended after not more than:






B: Suntiki Solar Inspection Report:

PV system inspection report:

ð      Initial verification.

ð      Periodic verification.














Circuits tested:






The entire system has been inspected to the requirements of IEC 60364-6 and an inspection report to meet the requirements of IEC 60364-6 is attached.


DC system – General


  • The DC  system  has  been  designed,  specified  and  installed  to  the  requirements  of IEC 60364 and IEC TS 62548:2016.
  • The maximum PV array voltage is suitable for the array location.
  • All system components and mounting structures have been selected and erected to withstand the expected external influences such as wind, snow, temperature and corrosion.
  • Roof fixings and cable entries are weatherproof (where applicable).


DC system – Protection against electric shock


  • Protective measure provided by extra low voltage (SELV / PELV) – yes / no.
  • Protection by use of class II or equivalent insulation adopted on the DC side – yes / no.
  • PV string and array cables have been selected and erected so as to minimize the risk of earth faults and short-circuits. Typically achieved by the use of cables with protective and reinforced insulation (often termed “double insulated”) – yes / no.


DC system – Protection against the effects of insulation faults


  • Galvanic separation in place inside the inverter or on the AC side – yes / no.
  • Functional earthing of any DC conductor – yes / no.
  • PV Array Earth Insulation Resistance detection and alarm system  is  installed  – to the requirements of IEC TS 62548:2016.
  • PV Array Earth Residual Current Monitoring detection and alarm system is installed – to the requirements of IEC TS 62548:2016.


DC system – Protection against overcurrent


  • For systems without string overcurrent protective device:
    • IMOD_MAX_OCPR (the module maximum series fuse rating) is greater than the possible reverse current;
    • string cables are sized  to accommodate the maximum  combined fault current from parallel strings.
  • For systems with string overcurrent protective device:
    • string overcurrent   protective   devices   are   fitted   and   correctly   specified   to   the requirements of IEC TS 62548:2016.
  • For systems with array / sub-array overcurrent protective devices:
    • overcurrent protective devices are fitted and correctly specified to the requirements of IEC TS 62548:2016.
  • For systems where the inverter(s) can produce a DC back-feed into the PV array circuits:
    • any back-feed current is lower than both the module maximum fuse rating and the string cable ampere rating.


DC system – Earthing and bonding arrangements


  • Where the PV system includes functional earthing of one of the DC conductors:
    • the functional earth connection has been specified and installed to the requirements of IEC TS 62548:2016.
  • Where a PV system has a direct connection to earth on the DC side:
    • A functional earth fault interrupter is provided to the requirements of IEC TS 62548:2016.
  • Array frame bonding arrangements have been specified and installed to the requirements of IEC TS 62548:2016.
  • Where protective earthing and/or equipotential bonding conductors are installed:
    • they are parallel to, and bundled with, the DC cables.


DC system – Protection against the effects of lightning and overvoltage


  • To minimize voltages induced by lightning, the area of all wiring loops has been kept as small as possible.
  • Measures are in place to protect long cables (e.g. screening or the use of SPDs).
  • Where SPDs are fitted, they have been installed to the requirements of IEC TS 62548:2016.


DC system – Selection and erection of electrical equipment


  • The PV modules are rated for the maximum possible DC system voltage.
  • All DC components are rated for continuous operation at DC and at the maximum possible DC system voltage and current as defined in IEC TS 62548:2016.
  • Wiring systems  have  been  selected  and  erected  to  withstand  the  expected  external influences such as wind, ice formation, temperature, UV and solar radiation.
  • Means of isolation and disconnection have been provided for the PV array strings and PV sub-arrays – to the requirements of IEC TS 62548:2016.
  • A DC switch disconnector is fitted to the DC side of the inverter to the requirements of IEC TS 62548:2016.
  • If blocking diodes are fitted, their reverse voltage rating is at least 2 x Voc (stc) of the PV string in which they are fitted (see IEC TS 62548:2016).
  • Plug and  socket connectors  mated  together  are  of  the same type  and  from  the same manufacturer and comply with the requirements of IEC TS 62548:2016.


AC system


  • A means of isolating the inverter has been provided on the AC side.
  • All isolation and switching devices have been connected such that PV installation is wired to the “load” side and the public supply to the “source” side.
  • The inverter operational parameters have been programmed to local regulations.
  • Where an RCD is installed to the AC circuit feeding an inverter, the RCD type has been verified to   ensure   it   has    been    selected    according    to    the    requirements    of IEC TS 62548:2016.


Labelling and identification


  • All circuits, protective devices, switches and terminals suitably labelled to the requirements of IEC 60364 and IEC TS 62548:2016.
  • All DC junction boxes (PV generator and PV array boxes) carry a warning label indicating that active parts inside the boxes are fed from a  PV array and may still be live after isolation from the PV inverter and public supply.
  • Means of isolation on the AC side is clearly labelled.
  • Dual supply warning labels are fitted at point of interconnection.
  • A single line wiring diagram is displayed on site.
  • Installer details are displayed on site.
  • Shutdown procedures are displayed on site.
  • Emergency procedures are displayed on site (where relevant).
  • All signs and labels are suitably affixed and durable.







C: Suntiki Solar PV Array Test Report:

PV array test report:

ð      Initial verification.

ð      Periodic verification.





Description of work under test








Test instruments:




String reference




















Array parameters (as specified)

Voc (stc)







Isc (stc)







String overcurrent protective device








Rating (A)







DC rating (V)







Capacity (kA)







String Wiring








Phase (mm2)







Earth (mm2)







String test

Voc (V)







Isc (A)














Polarity check








Array insulation resistance

Test voltage (V)







Pos – Earth (MΩ)







Neg – Earth (MΩ)







Earth continuity (where fitted)








Array isolator

Rating (A)







Rating (V)














Functional check








Make and model







Serial number







Functioning OK











About Us

CT TNHH Suntiki Solar is a solar energy company based in Vietnam. We consult, survey, engineer and install rooftop solar panel systems for residential, commercial, industrial such as factories, farms, villas, industrial parks and others.