Commissioning should prove three main criteria:
• The power plant is structurally and electrically safe.
• The power plant is sufficiently robust (structurally and electrically) to operate for the specified project lifetime.
• The power plant operates as designed and performs as expected.
Commissioning tests are normally split into three groups:
• Visual acceptance tests. These tests take place before any systems are energised and consist of a detailed visual inspection of all significant aspects of the plant.
• Pre-connection acceptance tests. These include an open circuit voltage test and short circuit current test. These tests must take place before grid connection.
• Post-connection acceptance test. Once the plant is connected to the grid, a DC current test should be carried out. Thereafter, the performance ratio of the plant is measured and compared with the value stated in the contract. An availability test, usually over a period of 5 days, should also be carried out.
Operations and Maintenance
Compared to most other power generating technologies, PV plants have low maintenance and servicing requirements. However, suitable maintenance of a PV plant is essential to optimise energy yield and maximise the life of the system.
Maintenance consists of:
• Scheduled or preventative maintenance – planned in advance and aimed to prevent faults from occurring, as well as to keep the plant operating at its optimum level.
• Unscheduled maintenance – carried out in response to failures. Scheduled maintenance typically includes:
• Module cleaning.
• Checking module connection integrity.
• Checking junction / string combiner boxes.
• Thermographic detection of faults.
• Inverter servicing.
• Inspecting mechanical integrity of mounting structures.
• Vegetation control.
• Routine balance of plant servicing / inspection.
Common unscheduled maintenance requirements include:
• Tightening cable connections that have loosened.
• Replacing blown fuses.
• Repairing lightning damage.
• Repairing equipment damaged by intruders or during module cleaning.
• Rectifying supervisory control and data acquisition (SCADA) faults.