Development of Maintenance and Management Guidelines for New Solar Power Generation Systems

On December 28, 2016, the technical document "Maintenance and Management Guidelines for Solar Power Generation Systems" jointly produced by the Japan Electric Machinery Industry Association (JEMA) and the Solar Power Generation Association (JPEA) was published.
According to the IEC (International Electrotechnical Commission) standards, the basic safety requirements, maintenance items, and inspection methods for solar power generation systems below 1500V DC have been compiled.

This guideline specifies the inspection of bypass diodes.

Usage of bypass diode tester FT4310

Suitable for maintenance of photovoltaic power generation systems. A bypass diode tester that can detect open circuit faults (OPEN)/short circuit faults (SHORT) without shading during the day. At the same time, introduce some measurements taken on site.

Can be used as a detection tool for bypass diode open/short circuit inspection without shading in sunlight

Utilizing the newly developed technology of HiOKI, it can perform bypass diode open/short circuit inspection without shading in sunlight. Inspections can also be conducted at night.
*Short circuit faults can only be checked during the day.

Open circuit/fault detection of bypass diodes can be performed in the battery string of the junction box

Due to the ability to perform simple inspections in the battery string of the junction box, there is no need to climb up the roof, greatly improving work efficiency.
*Measure the battery string as the measurement object after being disconnected from the system.

Complete all measurements in one inspection

Simply align the knob with "BPD TEST" and press the switch to measure the required items for fault diagnosis and display them all at once. One battery string can be measured within 2 seconds.
RBPR: bypass resistance Voc: open circuit voltage value Isc+α 1: measured current value Isc: short-circuit current value determination: whether there is an open circuit in the bypass diode (the RBPR value can also be determined when the comparator is set)

GENNECT Cross

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Notify through sound and light in case of abnormalities

Notify abnormal situations through buzzing sounds and red lights.
Example: When an open circuit fault occurs, use BPD TEST mode RBPR: display "Open (opn)".

Short circuit fault inspection - equipped with high-precision voltmeter

If the bypass diode experiences a short circuit fault, the solar cell will be unable to generate electricity, resulting in a decrease in output voltage (around 10V). By detecting this difference, short-circuit faults or mismatch losses of the bypass diode can be identified.
In order to detect the difference in 10V voltage in the 1000V system, a high-precision DC voltmeter is installed. If the "Voc mode" specially designed for open circuit voltage measurement is used, the voltage difference will be displayed within 1 second and the short-circuit fault will be determined.

Convenient attachments

The neck hanging carrying bag eliminates the worry of instruments falling off and provides accurate measurements without any burden on both hands
The test line with a switch does not require operation on the host due to the presence of a switch for holding, and it also comes with a small light for illumination

[Reference] Problems caused by faults in bypass diodes

Normal: When some parts of the solar panel experience hot spot effect (including fault conditions), current flows through the bypass to prevent a decrease in power generation efficiency.
Short circuit fault: If a short circuit fault occurs, the generated current forms a loop and cannot generate power, resulting in a decrease in power generation efficiency.
Open circuit fault: If an open circuit fault occurs, the forced flow of current through the problematic battery cell due to the hot spot effect may cause heat generation, which may lead to fire and other hazards.

[Reference] The impact of FT4310 on battery strings

Under sunlight, even if the open circuit detection of the bypass diode can be carried out, if it causes damage to the solar cell, this detection is meaningless. Therefore, we fully consider the impact that the battery string will be affected during measurement.
To use FT4310, simply press the measurement switch to first measure Isc (short-circuit current) and apply a voltage that allows it to flow through the current value plus 1A.
JIS requires that the bypass diode can withstand a current of 1.25 times the rated short-circuit current flowing through the module for 1 hour. FT4310 controls the constant current and adds a short time of less than 5ms. Through these designs, the battery string will not be affected by I-V measurements or insulation resistance measurements after a short circuit.
It will not damage the solar panel at all and can be used with confidence.