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Troubleshooting is a systematic method of investigating the cause of system problems and determining the best solution. Problem diagnoses begin with observations and measurements of the overall system. Through a process of confirming or eliminating factors, the investigation narrows to subsystems or specific components until the cause of a problem is found. The focus of troubleshooting is on remedying the cause, not the symptoms, of a problem. While identifying symptoms is a critical first step in determining the specific cause of a problem, there may be several contributing factors. For example, a dead battery is a common symptom. While the individual battery may fail solely due to the end of its useful life, aggravating circumstances could also be preventing the battery from charging. This includes factors that disrupt the energy balance of the system, such as excessive loads or a reduction in array output. If the battery is replaced without eliminating contributing factors, the problem of undercharge and pre mature failure may affect other batteries. Many possibilities must be investigated to prevent a misdiagnosis or partial diagnosis of the actual problem, as failure to correct the underlying problem results in wasted time and money. Troubleshooting Levels Troubleshooting procedures are designed to identify malfunctions by examining the system at progressively narrower levels. A trouble shooting level is the depth of examination into the equipment or processes that compose a system. Troubleshooting levels are very similar for all electrical systems, even though they may be named differently. For PV systems, the appropriate levels are the system level, subsystem level, component level, and element level. System Level. The system level encompasses the entire PV and power-distribution system, sometimes including the on-site loads. Systems may be isolated or may interface with other related systems. For example, a stand-alone PY system is a self-contained electrical system. A utility-interactive system, however, interacts with the utility grid. Even though the utility grid is much larger in scale, it’s considered a parallel system. Subsystem Level. The system is broken down into functional areas called subsystems. Subsystems may include many components, but they are all related to a particular function within the system, such as producing and controlling DC power. The subsystem level includes the energy production, storage, conditioning, distribution, and consumption functions. These functions correspond to the array, battery bank, inverter (or power conditioning unit), distribution panel, and loads, respectively. Each subsystem also includes all the auxiliary equipment related to the safe and efficient operation of that subsystem. For example, besides the batteries, the energy-storage subsystem includes the charge controller, disconnects, fuses, conductors, electrolyte containment, and ventilation devices. --22. The system level includes all the components of a PV system. ELEMENT LEVEL (PV CELL) COMPONENT LEVEL (PV MODULE) LEVEL; SYSTEM LEVEL (PV SYSTEM) --23. PV subsystems are divided by the components involved in energy production, storage, processing or conditioning, distribution, and consumption. PV Subsystems; ENERGY SUBSYSTEM Troubleshooting loss of performance from modules can include making electrical measurements at the junction-box terminals. The number and types of subsystems will depend on the system configuration. For example, interactive-only systems don’t include an energy-storage subsystem. Also, some systems may include multiple subsystems of the same type. For example, a very large system may have multiple arrays, each feeding a separate inverter. Or, a system may include both a DC power-distribution subsystem for DC loads and an AC power-distribution subsystem for AC loads. Component Level. The component level includes the discrete pieces of equipment that are acquired and installed individually to make up subsystems. This includes modules, disconnects, inverters, charge controllers, batteries, and loads. Each component performs a specific task by itself, such as opening a circuit, processing power, or storing a certain amount of energy. Element Level. Within the components are smaller elements. Individually, these elements are too small or too specialized to be useful in any way other than as a part of a component. For example, a PY cell is an element within a module component. A PV cell is not easily used by itself because it’s extremely fragile and a system would require hundreds or thousands of cells to produce an appreciable amount of power. A PV cell must be combined with other cells and additional elements (such as conductors, glass, and frames) to form a module component, the smallest practical PY unit for building a PV system. The distinction between the component and element levels can sometimes be unclear. For example, battery cells are considered components if they are large individual units, but they are considered elements if they are inseparable parts of a battery, which is then a component of the battery-bank subsystem. Fuses can sometimes be considered components and other times be considered elements, especially when they operate from within other components such as inverters. Some elements, such as fuses, circuit breakers, surge suppressors, and diodes, are easily field-serviceable, but many are not. When elements are not reasonably serviceable, the entire component may need to be replaced, even if only one small element is faulty. For this reason, field troubleshooting does not always reach the element level. For example, if an impact damages a module, it’s not worth while to disassemble the module and identify the individual broken cells since the module will still need to be replaced. For only certain components, such as inverters, is it cost effective to troubleshoot at the element level, and troubleshooting of this sort is not usually performed by field technicians. When found to be faulty during component-level troubleshooting, these components are usually sent to the manufacturer for service. Depending on the design of the component, subassemblies or circuit boards with a faulty element may be replaced to remedy the problem. Troubleshooting Procedures While troubleshooting at progressively more detailed levels, a systematic procedure is followed to determine the cause of the problem. While specific troubleshooting procedures will vary according to the type of system and equipment involved, a general strategy guides the overall troubleshooting process in a logical and efficient manner. Observation. The first step in troubleshooting is to identify the symptoms of a problem. Some problems may be obvious, while others may be noticed only during inspections and maintenance activities or when comparing the system performance with past experience of its normal operation. Therefore, some problems may be discernable only by the system owner! operator, who is most familiar with the system. For example, system output will normally fall during cloudy weather, but if output falls more than past experience predicts or fails to return to higher output later, a problem exists. Observation involves determining which part of the system is not working properly and observing the conditions that may have contributed to the cause. This includes obvious problems such as broken or burned equipment, water intrusion, and blown fuses. All equipment with monitoring, such as inverters and charge controllers, should be checked for error or fault indicators. Some indicators will provide very detailed information. Observation also includes attention to more subtle clues, such as any recent changes in the load requirements, maintenance plan, or weather patterns. If a problem is creating a hazard to persons or equipment, it may be necessary to immediately shut down the entire system. However, as some troubleshooting tasks, such as taking electrical measurements, require certain components or the entire system to be operating, extreme caution must be exercised when restarting the system. As with maintenance and testing tasks, all proper safety precautions should be followed. Research. Research involves gathering all the relevant system documentation together, particularly equipment manuals, and finding information about normal operating parameters, specifications, compatibilities, maintenance requirements, precautions, and error codes. Some manuals include trouble shooting instructions or flow charts that may help narrow the cause of the problem. If the system includes a data-acquisition system, past records can be used to look for unusual events or patterns in the measured parameters. Researching the maintenance log and troubleshooting reports for any previous symptoms or related problems can also help uncover the cause or at least suggest a line of investigation. Troubleshooting Levels --- The troubleshooting levels are important at the observation step in the troubleshooting process. The problem may be system-wide with an obvious cause, such as an unexplained low system output, which requires troubleshooting to begin at the system level. Further steps in the troubleshooting process will help narrow the cause of the problem down to the subsystems or individual components causing the problem. Alternatively, the problem may be relatively localized and the troubleshooter can begin observing the symptoms at the more focused levels. However, it may also be necessary to return to the overall system level if the cause of the problem cannot be determined. The chosen focus may have been an incorrect assumption. Ultimately, the troubleshooter makes a judgment about where to begin trouble shooting in order to find the cause of the problem quickly and efficiently. Investigation. Through observation and re search, the problem typically becomes well understood. The aim of investigation is to determine the root cause of the problem. For example, a blown fuse is easily fixed by replacing the fuse. However, an underlying problem caused the fuse to blow. Unless the cause is identified and addressed, the new fuse will likely blow relatively quickly. An investigation would seek to determine the cause of the overcurrent, so that the underlying problem could be remedied. Investigation is conducted primarily through inspection and testing. The causes that are the most likely and require the simplest remedies should be investigated first. These include damage from physical impacts, worn insulation, excessive heat or cold, electrical arcing, smoke, or fire. Portable test instruments are used to take electrical measurements at various points in the circuits to trace the locations of voltage drops, phantom loads, short circuits, and open circuits. Temperature measurements check for overheating equipment. Troubleshooting Flow Charts: Most equipment manuals include troubleshooting flow charts or procedures, which narrow the possible causes of a problem by following a specific set of instructions. It may be necessary to replicate the conditions associated with the symptoms of the problem. In order to determine which conditions contribute to the problem, conditions should be tested and eliminated, preferably one by one. A systematic investigation should gradually eliminate certain subsystems and components until the cause is isolated. Remediation. When the cause is discovered, it can be remedied, fixing the problem. This usually involves repairing or replacing components, re-terminating or tightening connections, or replacing damaged conductors. If the problem occurs during or soon after the system commissioning, there may be an inherent flaw in the design of the system, requiring more extensive remediation. Occasionally, the cause of the problem turns out to be minor enough that the remedy is not a high priority. That is, if the problem is not a safety issue and causes only a minor inconvenience, the owner may choose to live with it, especially if the estimated costs to remedy the problem are high. Still, the issue should be monitored and fully documented in case the problem worsens. Documentation. When troubleshooting has successfully identified the cause of the problem, it’s important to document the results. Troubleshooting reports should describe the problem, the steps taken to determine the cause of the problem, and the repair that eliminated or reduced the cause. This includes the symptoms, the equipment manuals consulted, the test instruments used, the measurements taken, and a detailed description of the remedy. Troubleshooting reports may also include recommendations for preventive maintenance to avoid a recurrence of the problem. These records should be kept with all the other system documentation so that they can be reviewed again as needed during future troubleshooting. 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