Energetica India Magazine: september 2020

SOLAR POWER But in this plant, these connections are not done as per correct label number. Rather, the positive and negative termi- nals from the same array were connect- ed to different label numbers in the SCB as shown in figure 2. In this scenario, one could argue that the connection is ok because all the arrays are connected in parallel. But what could go wrong? Imagine you need to disconnect array 1 from the sys- tem (in figure 2). If the O&M team will re - move the connector no. 1 from both pos- itive & negative sides of SCB, they will be under the impression that the array 1 has been disconnected. But this will not be true, since the connections were not right in the first place. The above figure doesn’t justify the com - plexity of the issue. Imagine there are 16 or 32 strings in the SCB and all the connections are mixed-up. It will take you an ample amount of time to debug these connections. And imagine doing that in adverse times like during array faults, which can cause delay and can also lead to SCB damage. Our team observed that this problem ex - isted in almost all of the SCBs in a 50 MWp plant. Which compels us to think of the frustration of the O&M team in times of fault rectification in the plant! %loading) can be drawn by calculating inverter efficiency at multiple time-inter - vals and any abnormality in this curve can directly indicate the inverter’s perfor- mance. Similarly energy efficiency tells the average efficiency of the inverter for a certain time period.. • Loss Analysis: This includes the anal- ysis of many different types of losses like shading loss, IAM loss, soiling loss, temperature loss, mismatch loss, mod- ule degradation loss, DC-AC ohmic loss, auxiliary consumption, transformer loss, system unavailability loss and transmis- sion line loss. • SCB and string analysis: SCB and string data analysis is also often ne- glected. Either the solar plant does not have string/SCB level monitoring or even in case monitoring is present, there are high chances that no analytics is done on this data. Not only string/SCB level mon- itoring is helpful in indicating any string/ SCB faults in real time for quick debug- ging, but also if this data is analyzed after proper normalization, it can even predict the underperforming strings/SCBs.. • WMS analysis: WMS is one of the most crucial instruments installed in solar plants. A weather monitoring station can be immensely helpful in monitoring the performance of any solar power plant. This instrument is installed to monitor important parameters like GHI & POA (Plane of Array) irradiation, ambient & module temperature, relative humidity, wind speed & direction, rain accumula- tion, etc. O&M activities often multifolds when un- predictable events like natural disasters, theft, fire, equipment damage, series of failures, deterioration due to design faults, or even new design modifications required due to regulatory changes, etc. occur. Other additional maintenance re- sponsibilities include module cleaning, vegetation control, general site mainte- nance, waste disposal, drainage, build- ing maintenance, on-site measurements, etc. Even though there are so many steps taken to maintain the performance of the plant, we have observed many issues on-site. The reasons may be ignorance, insufficient information availability, or miscommunication on-site. Whatever the reason, it directly hampers the perfor- mance of the plant. We are sharing one such case study below: Wrong connection of PV array in the SCB In a plant of 50 MW, we recently observed that there were wrong connections of PV arrays in the SCBs which made the main- tenance of specific PV arrays a tedious task. Brief background : In a SCB, strings are terminated usually via a connector (shown by numbers in the below figure) which contains a label of the string con- nected. So both positive & negative ter- mination of the PV array / string is to be done as per correct label numbers (Figure 1). 59 energetica INDIA- September_2020