The installation of a solar power plant involves significant amount of DC cables and the wiring methods are usually different as compared to traditional AC wiring methods. The DC electricity generated through the arrays is fed through the inverter which convert it in to AC electricity and finally the AC electricity is stepped up to inject in to the grid at an appropriate voltage level. The successful commissioning of a solar plant needs a detailed ev
aluation of both AC side as well as the DC side of the solar plant.
The PV panels are typically current limiting devices and does not produce enough current to operate the over current relays/fuses. Due to this property of PV systems many times the leakage current remains undetected and can be hazardous to the operating staff and at times can also lead to fire in the system. The undetected leakage current also leads to the significant losses in the PV system and becomes a major reason for the energy leakage in the system. Hence the PV system installation needs to be safe and needs to be tested through a proper commissioning process which is generally missing in most of the large installations. The commissioning needs to be done by any third party so that an independent verification of the system performance can be done.
There is no Indian code for the solar PV installation however there are international codes and standards which needs to be followed to check the installation as a part of the commissioning process. Installation of DC wiring can be done as per the IEC 62446 which sets out the minimum requirements for PV system documentation, commissioning tests, and inspection. The standard sets out the information and documentation that should be provided as a part of final commissioning of the project. If the PV project installation follow the specified codes and standards, this ensures that the PV panels and electrical supply connections have been wired up correctly, the electrical insulation is good, the protective earth connection is as it should be, and there has been no damage to cables during installation.
IEC 62446 sets a number of testing criteria, including the polarity of DC cables, a voltage test for the open circuit and current test for a short circuit, irradiance, an insulation test, and operational and functional tests. Different PV electrical tests require different test instrumentation – typically including an earth continuity and insulation resistance tester‚ a multimeter, and DC clampmeter. Using such an array of instruments can be cumbersome and time consuming, which has led to the introduction of a new generation of integrated testers capable of performing all of the tests required by IEC 62446.
If the installation and commissioning of the solar project is proper and the care has been take on the issues highlighted above, there is no reason that the plant is underperforming.