Solar Power Plant Inspection Service

Our inspection performed so far

Inspected power plants: 319

< 2MW	180 sites
2MW-10MW	38 sites
10MW-50MW	73 sites
50MW-100MW	15 sites
> 100MW	13 sites

*As of December 31, 2023. Some power plants have been inspected several times.

Service Outline

Provides inspection services on site at the same level as solar panel manufacturers

We provide various performance/safety tests including insulation resistance measurement, ground resistance measurement as well as string I-V inspection, EL inspection, and IR inspection using thermography.

We provide services of pre-operation voluntary test and pre-operation self check, mandated by revision of FIT scheme in 2023 for solar plants of 10kW – 2,000kW.

Through partnership with cooperating companies, we also cover integrated O&M services including regular safety checks performed every month or year.

Total services covering DC to AC

Covered by NPC

Completion test

Pre-operation voluntary inspection

Pre-opereation self check

Performance/Safety

I-V characteristic inspection

Voc measurement
Grounding resistance measurement
Disconnection check

Visual check

Insulation resistance check

Ground fault resistance test

EL inspection

IR inspection

Safety

Monthly check

Regular check

Annual check

Introducing our integrated inspections/maintenance service of solar power plants
(5 min. 51 sec. with sound)

Advantages of NPC

Providing our unique analysis ability and detailed reports
Superb on-site flexibility based on a number of inspection performances
Good cost performance through nationwide network
Proposing a wide variety of inspections covering DC to AC

Main inspections

I-V inspection Use of “Rakit,” our multi-functional high-speed I-V measurement system, shortens inspection time and saves power loss to the minimum level. Highly accurate analysis results will be automatically provided through the data conversion under STC (temperature: 25℃, irradiance: 1,000W/m²).
On-site EL/PL inspection Use of “EPTiF,” our original EL/PL inspection machine enables us to perform EL/PL inspections during daytime without removing panels. It provides detailed inspection in an easy and safe manner, identifying all the defects and their causes from micro-cracks to disconnection and PID.
IR inspection (by thermography) Temperature measurement by IR using the high-resolution thermographic camera (E75) by FLIR identifies faulty panels with hot spots, etc. Efficient IR inspection using a drone is also available.
Other inspections Using “DCFT,” DC safety inspection device for solar panels, we check ground fault resistance, break in electric path, bypass diode disconnection, etc. and identifies faulty panels in a short time. We also provide visual check required at pre-operation voluntary inspection, insulation resistance measurement, ground resistance measurement, dielectric strength test. Efficient barcode reading is also available, utilizing our experience.

NPC Original Maintenance Service

According to our customer's needs, we provide various inspection/maintenance services.

Case study

Spot inspection ■Capacity : approx. 4MW / 3 years after installation ■Inspection： I-V inspection, EL inspection, report ■Result: significant power decline found in approx. 70 strings I-V data. As a result of EL inspection afterwards, PID occurrence was detected and dozens of panels were exchanged.
Completion inspection (Pre-operation voluntary inspection) ■Capacity：approx. 20MW ■Inspection： I-V inspection, Voc/polarity check, report ■Result： disconnection of interconnectors/connectors and faulty soldering were found in approx. 70 strings I-V data and dozens of panels were exchanged.
Completion inspection (Pre-operation voluntary inspection) ■Capacity：over 50MW ■Inspection： Insulation resistance measurement, ground resistance measurement, dielectric strength test, I-V inspection, bar code reading, report
Regular maintenance ■Capacity: 100kW rooftop system ■Inspections: 3-month regular check (visual check, insulation resistance measurement, Insulation resistance measurement, ground resistance measurement, report) Annual check (regular check, safety check using “DCFT,” report)

Maintenance Service Flow

Inquiry
Obtaining power plant information
(spec of panels and junction boxes, connection block diagram, panel distribution drawing, etc.)
Proposal of estimates
On-site inspection
Providing analysis report

Case Study

Matsuyama Foundation for Culture and Sports Promotion

Outline of the solar system

Start of operation: 2001
Location: Matsuyama Outdoor Activity Center, Matsuyama city, Ehime Prefecture
Number of panels: more than 400 panels deployed on the ground and rooftop, respectively
Generation capacity: 100kW

Purpose of inspection

We inspected the system to confirm if it was operating in a sound condition after more than 15 years (at the time of the inspection) of operation, both in the view of safety and performance. If any problems were found, we were to identify the causes.

Contents of inspection

We performed visual inspection, Voc measurement, disconnection test, ground fault resistance test, I-V inspection, and IR inspection using thermography camera in one day.

Result of inspections

We found panels with melting backsheets, disconnection and broken glass, hotspots, and electrical insulation failure. We issued a report stating each problem and the considered causes, and secured safety by disconnecting the panel strings with insulation failure. We also replaced the disconnected panels with new ones.

The panels installed on the rooftop were estimated to have caused high resistance and open bypass circuit, considering the significantly lower FF compared with those on the ground. As they were installed on the rooftop, where dissipation of excess heat was limited, we recommended the customer to remove the panels to avoid a fire risk. As a result, the whole rooftop system was moved away. As to the ground-mounted system, all the defective panels were exchanged to good-quality panels and secured safety. Since then, the system has continued to generate power without any problem. The customer asked us to perform regular inspections and maintains the soundness and safety of the system.

Customer's voice - reviewing our inspections

"When we found abnormal operation of the rooftop solar system, we asked NPC for inspections of our solar systems. As a result, several defects including damage by heat were found. To secure safety, we removed all the panels installed on the rooftop.

Since NPC provided us with appropriate proposals from a series of inspections to the actions in the future, we were able to solve the problem quickly. We thrive to operate the Outdoor Center safely and comfortably by performing safety check of the ground-mounted panels at the regular inspections."

Examples of Solar Power Plants Inspected So Far

Company J Site: Yamaguchi Pref. Capacity: Approx. 2MW	Company J Site: Yamaguchi Pref. Capacity: Approx. 9MW	Kikuno Co., Ltd. Site: Ehime Pref. Capacity: 844.48kW
Company J Site: Yamaguchi Pref. Capacity: Approx. 15MW	Chudenko Site: Hiroshima Pref. Capacity: 15kW	Kishiro Co., Ltd. Site: Ehime Pref. Capacity: 2.19MW
Lixil Site: Kumamoto Pref. Capacity: 3.75MW	Matsuyama Kanko Golf Site: Ehime Pref. Capacity: 1.43MW	Company A Site: Shiga Pref. Capacity: approx. 1MW
Mirait Technologies Site: Chiba Pref. Capacity: 32MW	JFE Technos Site: Tochigi Pref. Capacity: 13MW	JXTG Energy Site: Kagawa Pref. Capacity: 1.4MW
JXTG Energy Site: Ehime Pref. Capacity: 1.1MW	JXTG Energy Site: Ehime Pref. Capacity: 1.4MW	JXTG Energy Site: Ibaraki Pref. Capacity: 2.0MW
JXTG Energy Site: Akita Pref. Capacity: 2.4MW