Some electric facilities are 'consumables'
Q: The use of products manufactured overseas is increasing rapidly in mega solar power plants in Japan, and the speed of deterioration in the future poses a serious risk, according to some experts.
Oyama: Based on my experience of handling solar power plants for many years, I believe many of the panels manufactured and sold by domestic manufacturers before the start of the FIT scheme are generating power satisfactorily after 20 years.
However, it is unknown whether the solar panels installed in large volumes at domestic solar power plants after the start of the FIT scheme are as reliable as those manufactured before the start of the FIT scheme. I think it is possible that a decline in the power generation amount exceeding the aging deterioration guaranteed by manufacturers (linear guarantee) will become apparent in the future.
Q: What are the key points in inspection and maintenance of grid connection equipment and PV inverters?
Oyama: Special attention, which is different from the attention paid to panels, is required for inspection and maintenance of grid connection equipment and PV inverters. The loss of the overall power generation amount is limited when a few of the panels develop problems, but if a problem occurs in the grid connection equipment, all the power is lost. In case of PV inverter failure, the power generated by all the panels connected to the PV inverter is lost.
In addition, caution is required for connection equipment and PV inverters as they are precision "electric facilities" and contain consumables with a service life of five to ten years.
In the case of PV inverters, fans and filters will surely deteriorate. If deteriorated parts are left unattended, unexpected operation stoppages, including those due to activation of the safety system caused by temperature rises, will occur. Toshiba Mitsubishi-Electric Industrial Systems Corp (TMEIC), for example, recommends detailed inspections at an interval of five years, in addition to the annual inspections, and fans and filters are replaced during the detailed inspections.
In respect to facilities in operation for more than five years, West O&M entrusts detailed inspections of the sites owned by the group to TMEIC. We also adopt the same stance for sites owned by customers.
Q: What are the cautions regarding grid connection equipment?
Oyama: Based on my 40-year experience in security management of grid connection equipment such as cubicles, arresters (lightning arresters) that prevent intrusion of abnormal current due to lightning need to be checked periodically to prevent accidents caused by the failure of such arresters.
This is my personal view, but recent lightning strikes have been stronger compared with those in the past, and cases of failure to prevent intrusion of abnormal current into sites due to deterioration of arresters are increasing.
High pressure vacuum circuit breakers (VCBs) should also be checked periodically for leakage of vacuum air and replaced without fail in case the measured value is lower than the standard value.
Steady "preventive maintenance" is more important for PV inverters and grid connection equipment than for solar panels, because the impact of their failure is more substantial.