5 grounding and leakage alerts to check that can lead to reduced power generation

When power generation is low, the first causes that come to mind are weather, shading, dirty panels, and equipment failures. However, at some sites, alerts related to grounding, ground faults, leakage currents, or insulation degradation can provide clues to a drop in power generation. Poor grounding or deteriorating insulation may not immediately manifest as a major generation stoppage, but can lead to equipment protective actions, output shutdowns, alarms from grid‑interconnection devices, or decisions to halt operation during inspections, and thus become factors that reduce power generation.

Particularly in solar power generation systems, numerous wiring, junction boxes, mounting racks, power conditioners, and grounding conductors are installed outdoors. Because there are many factors that affect electrical insulation—rain, humidity, condensation, vegetation, animals, ultraviolet light, temperature changes, damage during installation, and so on—when checking for low power output it is important not to look only at generation performance but also to confirm the presence of grounding and leakage alerts and the conditions under which they occurred.

However, checks related to grounding, earth faults, leakage current, and insulation deterioration require strict attention to safety. You can infer causes from the content of alerts, but on-site measurements, operation of breakers/switches, inspections inside panels, and insulation resistance testing should be performed by qualified personnel or specialists who understand the equipment specifications and safety procedures. In this article, we explain five perspectives on grounding and leakage alerts as checkpoints for practitioners to use when organizing reports, monitoring screens, inspection records, and on-site conditions during periods of low power generation.

Table of Contents

• Clarify the relationship between decreased power generation and grounding/earth-leakage alerts

• Check 1 Cross-check the alert occurrence time with the time period of decreased power generation

• Check 2: Examine the relationship between rainy weather, humidity, condensation, and leakage alerts

• Check 3: Divide the degradation range by string-level or circuit-level

• Check 4: Verify the inspection records for grounding conductors, mounting racks, and around panels.

• Check 5: Track post-recovery power output and recurrence trends

• Establish operational procedures to ensure grounding and leakage alerts are not overlooked.

• Summary Safely isolate the causes of low power generation

Organize the relationship between reduced power generation and grounding/earth-leakage alerts

Low power generation is not necessarily caused by a single factor. Some days have low solar irradiance, and there are seasons when shadows are long. Dirt on the panel surface, overgrown vegetation, shutdown of the power conditioner, communication failures, output control, and grid-side issues can all overlap and appear together. Among these, grounding and leakage alerts are important signals related to safety, and are items you should check early as potential causes of reduced power generation.

Grounding plays an important role in properly connecting the metal parts of equipment and electrical devices to earth, reducing the risk of electric shock and equipment damage. On the other hand, leakage current and earth faults can refer to conditions in which current flows through unintended paths. In photovoltaic systems, the scope to check tends to be wide, including DC-side cables, junction boxes, panel backside wiring, AC-side equipment, terminal blocks inside panels, and areas around grounding conductors. When an alert is issued, the system may perform protective actions, the affected circuit may stop, or part of the operation may be halted for inspection, which can make the power output appear lower.

One thing to be careful of is not to immediately conclude that a grounding or leakage alert indicates a serious fault at a specific location. In reality, there are multiple possible causes, such as temporary moisture, ingress of rainwater, damage to wiring, loose terminals, condensation inside panels, effects from vegetation or animals, measurement conditions, and detection conditions on the sensor side. Also, even if an alert is displayed in the monitoring system, the issue may already have been resolved on site, or conversely, although it may appear to be resolved, a tendency for recurrence may remain.

When investigating low power generation, first check whether the drop in output is occurring across the entire installation or is concentrated in certain circuits or specific power conditioners. Then cross-check the timing of grounding and leakage alerts, their duration, where they occurred, recovery history, weather conditions, and inspection records. Rather than looking only at the generation figures, arranging alert information chronologically makes it easier to see the background behind the decline.

Information about grounding and earth leakage should be handled separately for safety checks and root-cause investigation. If the decision to restore power generation takes precedence, there is a risk of downplaying the significance of alerts. Abnormalities related to grounding and leakage can affect worker safety, equipment protection, fire risk, and equipment lifespan. Rather than aiming solely to recover generation output, it is necessary to prioritize safe shutdown, verification, recording, and sharing information with the responsible specialists.

Check 1 Cross-check the alert occurrence time with the period of reduced power generation

When checking grounding and leakage alerts, the first things you should look at are when the alert occurred and how power generation changed during that period. If you only look at the end result of low power generation, it is difficult to determine whether the cause was the weather, equipment shutdown, or an electrical fault. However, overlaying the alert time on the generation graph makes it easier to clarify the relationship with the drop in generation.

For example, if the system was generating normally in the morning but the output suddenly drops from a certain time and an earth-leakage-related alert occurs just before or at the same time, a protective operation or shutdown of the affected equipment may be related to the reduction in power output. On the other hand, if the power output has been generally low since the morning and an alert occurs only once in the evening, the primary cause may be elsewhere, and the alert may be secondary information.

When evaluating changes in power generation, it is important not to rely solely on daily totals. Daily generation is heavily influenced by weather and solar irradiance. To assess the relationship with ground-fault/earth-leakage alerts, where possible review time-of-day generation, output by power conditioner, per-string monitoring values, and the alert history in chronological order. In particular, changes in output before and after an alert provide useful clues.

If there is a sudden drop, consider the possibility that the equipment has stopped. If a gradual decline continues, consider deterioration of insulation, partial circuit faults, or the influence of environmental conditions. However, you cannot definitively identify earth leakage or grounding faults from the shape of the power-generation graph alone. Treat it only as an initial indicator to decide whether on-site inspection or measurement is necessary.

Also check how long the alert persists. The priority of response changes depending on whether it occurs only briefly and recovers on its own, repeats multiple times, or remains uncleared. Even a temporary alert, if it repeats only during rain or in the early morning, may indicate a relationship with moisture or condensation. Recording the timing of the drop in power generation and the pattern of repetition makes it easier to explain reproducibility during inspection.

Also, it is important to verify that the timestamps on the monitoring screen and the on-site records are not offset. Depending on the settings of communication equipment or monitoring devices, differences can occur in how recorded times are handled. When reconciling inspection reports, monitoring logs, weather data, electricity sales statements, and on-site work reports, a mismatch in time references can lead to incorrect cause attribution. For analysis of days with low power generation, the basic practice is to align and view the data on the same time axis.

Even when the alert time coincides with a drop in power generation, it is important not to rush recovery operations. Grounding and leakage alerts relate to safety, and repeatedly re‑energizing or continuing operation without identifying the cause can allow risks to be overlooked. As operational personnel, organize the time of occurrence, how the generation dropped, the affected equipment, and the recovery status, and record them as information that makes it easier for specialists to make a judgment.

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Check 2: Observe the relationship between rainy weather, humidity, condensation, and leakage alerts

One thing to check carefully when you receive grounding or leakage alerts on a solar power system is their relationship with weather and humidity. Outdoor equipment is vulnerable to rain and humidity, and locations that may not show problems during clear weather can experience deterioration in insulation during rainy periods or times when morning dew forms. If a leakage alert appears on a day with low power generation, check not only the weather on that day but also whether it rained the previous day, nighttime humidity levels, morning condensation, and the presence of snow or frost.

It is natural for power generation to be lower during rainy weather, but if certain equipment stops only on rainy days, alerts occur on the morning after rain, or the drop in output is greater than that of surrounding equipment even on cloudy days, you should suspect factors other than mere insufficient solar irradiance. In particular, junction boxes, cable connection points, the waterproofing of switchboards, conduit risers, wiring behind panels, and connector areas are locations prone to moisture and should be inspected.

Condensation is another factor that is easy to overlook. During periods with large temperature differences between day and night, or in high-humidity environments, condensation can form inside panels and equipment. If an alert appears only in the morning and then naturally clears during the day, the symptoms may be temporarily disappearing because rising temperatures dry the moisture. In such cases, abnormalities are difficult to detect with inspections conducted only during the daytime, so recording the environmental conditions at the time the condensation occurs is helpful.

You should also check for the effects of vegetation, fallen leaves, and sediment. Where cables are close to the ground or covered by grass, moisture tends to accumulate. Fallen leaves and mud can obstruct drainage and cause water to pool around connection points. At solar power plants, shadows and dirt often attract attention as causes of reduced output, but the same vegetation and drainage problems can also contribute to leakage risk.

When examining the relationship with rainy weather or humidity, it is important not to simply conclude “generation was low because it rained.” A drop in generation on rainy days can be normal, but by checking alarm occurrences, shutdowns of specific circuits, time to recovery, and differences with neighboring installations, you can narrow down the likelihood of an anomaly. In particular, if a specific installation shows a much larger drop than other installations in the same area and under the same solar irradiance conditions, check whether there are factors that cannot be explained by weather alone.

In inspection records, it is useful to note not only the presence or absence of alerts but also the weather, temperature, humidity, rainfall trends, muddy conditions on site, water droplets inside the panel, wetness around wiring, drainage conditions, and so on. When taking photos, don’t just photograph the equipment; compose shots so the situation can be read later—show locations where water tends to collect, cable routing, contact with vegetation, the underside and back of the panel, etc.—as this helps with subsequent root‑cause investigations.

However, when inspecting equipment or electrical panels that are wet, you must be aware of the risk of electric shock and short circuits. On-site personnel should not attempt to handle them themselves; after conducting safety checks, deciding whether to shut down, and defining the scope of work, they should hand the task over to specialist personnel. The more urgent it is to quickly resolve a low power output condition, the more cautiously inspections of electrical equipment should be carried out in rainy weather.

Check 3: Differentiate the range of degradation by string unit or circuit unit

To determine whether a grounding or leakage alert is related to a drop in power generation, it is important to examine the scope of the decline. Looking only at the total generation of the entire system does not reveal whether the anomaly affects the whole system or is limited to certain circuits. In photovoltaic systems, separating and checking generation data and fault histories by units such as panels, strings, junction boxes, power conditioners, and AC-side equipment makes it easier to pinpoint the cause.

For example, even if the facility's total power generation appears to be low, in reality only one power conditioner may have stopped. In such a case, the overall generation may look like only a partial decrease, but the output of the affected unit can be greatly reduced. If a leakage alert is linked to that unit, you can prioritize checking its relationship to the drop in generation.

On the other hand, if all the power conditioners are similarly low, candidates include weather, output control, grid-side conditions, overall settings, or problems with shared equipment. Even if grounding/leakage alerts appear on some units, that alone does not necessarily explain an overall drop. To avoid incorrectly concluding the cause of reduced generation, it is necessary to check whether the area of reduction matches the area with alerts.

If string-level monitoring is available, you can examine things in greater detail. If there are trends such as only a specific string showing low current values, only the circuits under a particular junction box being unstable, or only some circuits dropping out during rainy weather, it becomes easier to narrow down targets for on-site inspection. However, because string-monitoring values are also affected by measurement conditions and solar irradiance conditions, it is important to compare circuits with the same azimuth, the same tilt, and similar installation conditions.

When isolating the range of degradation, comparing it with a normal circuit is effective. Even if it is difficult to judge by looking only at the circuit with low power output, comparing it with an adjacent circuit under the same conditions makes it easier to detect abnormalities. Information such as only one circuit showing an output drop at the same time of day, only a particular circuit recovering slowly after rain, or alert histories concentrated in specific locations provides clues for prioritizing on-site inspections.

Also, when isolating at the circuit level, cross-checking with single-line wiring diagrams and equipment layout drawings is indispensable. If the names on the monitoring screen, the names on the on-site panels, the circuit numbers on the drawings, and the entries in the inspection reports do not match, there is a risk of misidentifying the location of an anomaly. When equipment has been in operation for a long time, renovations, additions, wiring changes, and name changes may have been carried out. To correctly assess the relationship between decreased power generation and alerts, it is necessary to align the names in the data with the actual physical equipment on site.

On-site measurements must always be performed in accordance with safety procedures. Insulation resistance measurements and circuit isolation can be hazardous if the measurement conditions, effects on equipment, outage scope, and re-energization procedures are not understood. Field personnel should identify which circuits have concentrated alerts, which areas are experiencing reduced power output, and the time periods when these occur, and prepare materials so that specialists can investigate safely.

Check 4: Verify the inspection records for grounding conductors, mounting racks, and the area around panels

When checking grounding and leakage alerts, not only monitoring data but also on-site inspection records are important. Grounding conductors, mounting racks, around panels, cable fastening points, terminals, conduits, and connection points can change condition over time. When investigating causes of low power generation, it is important to review whether minor abnormalities noted in past inspections might be related to the current alert.

Around grounding conductors, items to check include loosened connections, corrosion, broken wires, detachment, unclear labeling, and burial by soil or vegetation. Even if there are no obvious external abnormalities, connections may have deteriorated or restoration checks after repair work may have been insufficient. Grounding is an area that is not easily visible from routine power-generation graphs, but because it relates to equipment protection and safety, record-based management is important.

The area around the mounting structures should also be inspected. Mounting structures for solar panels are installed over wide areas and are exposed to wind, rain, temperature changes, and ground conditions. If the connections of the mounting structures or metal components deteriorate, the continuity of grounding and protective functions may be affected. In particular, ground subsidence, soil erosion, contact during grass-cutting work, gnawing by animals, and deterioration of cable supports are factors that should be checked as potential causes of electrical anomalies.

Around the panel, items to check include water ingress, deterioration of gaskets, how well the doors close, the condition of ventilation openings, cable entry points, discoloration of terminals, unusual odors, and signs of insect or small animal intrusion. Abnormalities inside the panel can easily lead to power generation stoppages or alerts and may be related to reductions in power output. However, inspecting inside the panel involves risks, so it should not be opened casually; responses must follow the equipment management rules.

When reading inspection records, verify not only whether abnormalities were present but also what actions were taken after they were pointed out. Check whether items marked as "under observation" have remained for an extended period, whether repaired locations have experienced recurrence, or whether multiple issues have been reported in the same area—this makes it easier to infer a connection with the current decline in power generation. Sites that were previously noted for rainwater intrusion or reduced insulation and that are triggering alerts again during rainfall should be prioritized for inspection.

Also, checks related to grounding and earth leakage can significantly influence later determinations depending on the quality of photographs and numerical records. When an inquiry is received that power generation is low, if past inspection photos are too close so the location cannot be identified, circuit numbers are not visible, measurement conditions are unclear, or there are no post-improvement photos, investigating the cause will take longer. From the routine inspection stage, it is important to keep records of where, when, under what conditions, and how checks were performed.

To connect inspection records with power generation data, unifying on-site names is also indispensable. If drawings, monitoring screens, panel labels, and inspection reports use different names, it becomes difficult to determine which piece of equipment an alert refers to. In investigations into reduced power output, mismatched names can lead to rework. Records of grounding conductors and the areas around panels should be maintained not merely as archival materials but as practical working documents for tracing causes when anomalies occur.

Check 5 Track power generation and recurrence trends after recovery

After a ground-fault or leakage alert appears, even if it initially seems to have been resolved, it is important not to stop checking there. Even if the low power output appears to have been resolved, the same alert may recur, it may reappear only during rainy weather, or output may become unstable during specific time periods. By tracking post-recovery power generation and the alert history, it becomes easier to determine whether the root cause has been fundamentally fixed or whether the symptoms have only temporarily disappeared.

After recovery, verify that the power output of the affected equipment and circuits has returned to its normal range. What matters here is not merely whether power is being generated, but whether there is anything unusual compared with circuits under the same conditions or with past performance. Even if output returns after an alert is cleared, if it remains lower than before or is slow to ramp up despite sunlight, there may still be issues that require further verification.

The period for observing recurrence trends varies depending on the conditions that caused them. If an alert occurred during rainy weather, you need to check the conditions on the next rainy day or on mornings with high humidity. If an alert occurs during high temperatures, you need to monitor the time periods when temperatures rise. If an alert occurred after specific work, verify it together with the work history, such as repairs, grass cutting, cleaning, or equipment modifications. Understanding the recurrence conditions makes it easier to determine inspection timing and priority areas.

In investigating the causes of reduced power generation, comparing conditions before and after recovery is extremely important. By examining data in sequence—before the alert, during the alert, immediately after recovery, several days later, and after the next rainfall—you can confirm the effectiveness of the remediation. If generation does not recover sufficiently despite restoration work, consider the possibility that causes other than grounding or leakage coexist. For example, even if equipment that was partially shut down by a leakage alert is restored, generation may not return as expected if another circuit still has shading, soiling, or equipment degradation.

Also, in post-restoration records it is important to document what was checked and the basis for the decision to restore service. The mere fact that an alert disappeared does not allow for comparison if the same problem occurs later. Organizing the inspection date and time, weather, scope of shutdown, checked locations, measurement conditions, repair details, restoration time, and the trend in power generation after restoration will speed up decision-making next time. In facility management, leaving records that can reveal recurrence is more valuable than considering a response complete after a single action.

Consultations about low power generation tend to require urgent responses because of concerns about the amount of electricity sold and operational revenue. However, when grounding or leakage alerts are involved, it's necessary to consider not only the short-term resumption of generation but also safety and measures to prevent recurrence. If recurring alerts are left unaddressed, not only will reductions in power generation recur, but the effort required for inspections, downtime, and the burden of coordination among stakeholders will also increase.

Systematizing follow-up after recovery makes it easier to determine whether an anomaly is transient or persistent. If you record in monthly reports and maintenance inspection reports the number of grounding/leakage alerts, the time periods when they occurred, the affected equipment, recovery status, and whether they recurred, it becomes easier to explain the background of reduced power generation. It is important to keep these as documents that can track changes in equipment condition, rather than as records of one-off responses.

Establish an operational framework to ensure grounding and leakage alerts are not overlooked

To quickly identify the cause of low power generation, an operational system that ensures grounding and leakage alerts are not routinely overlooked is necessary. Alerts are not only important at the moment they occur; they also serve as records for tracing the causes of subsequent decreases in power generation. Even if an alert shown on the monitoring screen is checked on the spot, if no record is kept or the actions taken are not shared, decision-making will be delayed when the same problem recurs.

First, it is important to organize the classification of alerts. Even alerts that look similar—such as grounding, earth leakage, ground faults, decreased insulation, equipment shutdowns, communication failures, and grid abnormalities—can have different meanings. Some are directly related to a drop in power generation, while others remain merely monitoring indications. Operational staff do not need to make every technical judgment themselves, but you should decide which alerts should be prioritized for safety checks and which staff members they should be shared with.

Next, clarify the initial response when an alert occurs. If the person who confirms a low power generation state has decided in advance who to contact, what information to collect, and how far to inspect, on-site responses will be more consistent. For alerts related to grounding or leakage, it is also important to avoid taking casual on-site actions. Even if there is a desire to restore generation quickly, operating procedures should prioritize expert judgment for safety-related alerts.

How information is shared is also important. If the alert occurrence time, the affected equipment, changes in power output, the weather, past similar alerts, recent work history, on-site photos, and inspection records can be shared as a single, coherent timeline, stakeholders can make decisions more quickly. Conversely, if only the power output graph, only the alert screen, or only on-site photos are shared separately, it becomes harder to see the connections to the cause. The lower the power output, the more important it is to compile information in chronological order.

It is effective to include checks that can lead to grounding or earth‑leakage alerts in daily inspection items. Water ingress around the electrical panel, damaged wiring, sagging cables, contact with vegetation, signs of animal intrusion, abnormalities at terminals, the appearance of grounding conductors, and changes around the mounting structure can all appear as signs before a decline in power generation occurs. If you record these points from the same perspective at each inspection, it becomes easier to compare differences with past records when an abnormality occurs.

Also, judging a decline in power generation requires a baseline of normal conditions. Without knowing each installation’s typical generation patterns, seasonal tendencies, weather-related fluctuations, and differences between equipment, it becomes difficult to determine how large a decline should be considered abnormal. When a grounding or leakage alert is issued, having the usual generation levels and past alert history organized also makes it easier to set response priorities.

The purpose of establishing an operational framework is not to have on-site personnel resolve every anomaly on their own. Rather, it is to avoid dangerous work, quickly gather the necessary information, and create a situation in which specialists can make safe decisions. For the issue of low power generation, having a system that can appropriately handle grounding and leakage alerts reduces rework in root-cause investigations and makes it easier to prevent prolonged generation losses while maintaining equipment safety.

Summary: Safely isolate the causes of low power output

When checking grounding and leakage alerts that can lead to reduced power output, it is important to look comprehensively not only at the power output figures but also at the alert occurrence time, the weather, the extent of the drop, inspection records, and the trend after recovery. The cause of low power output is not necessarily a single factor; the grounding/leakage alert may be the primary cause, or it may overlap with other factors. Avoid rushing to a conclusion; making judgments by aligning the timeline with on-site information is the quickest way to reduce rework in practice.

First, cross-check the time the alert occurred with the period of reduced power generation. By checking whether the output dropped at the same time as the alert or whether there is a time lag between the decrease and the alert, you can clarify their relationship. Next, check for connections with rain, humidity, and condensation. Outdoor equipment can experience temporary deterioration of insulation due to moisture, and symptoms may appear only in the early morning or after rain.

Furthermore, it is important to isolate the scope of the decline at the string level or circuit level. Abnormalities that cannot be detected from the total power generation of the entire installation are easier to find when examined by equipment or by circuit. At the same time, check the inspection records for grounding conductors, racking, and around the panels, and review whether past findings or repair histories are linked to the current alert. After restoration, track not only whether generation has returned but also whether there are any signs of recurrence.

Confirmations regarding grounding and leakage are directly linked to safety, so on-site measurements and operations require careful handling by specialized personnel. The role of operational staff is not to force a determination of the cause, but to clarify the relationship between decreases in power generation and alerts and to correctly share the necessary information. If alert histories, power generation data, weather information, inspection photos, and work records are all available, it becomes easier to investigate the cause.

To avoid leaving a low power generation condition unattended, a system that links daily monitoring and inspection records is indispensable. Grounding and leakage alerts are not merely warning displays but important signs to prompt an early review of equipment safety and generation losses. By understanding the normal values for each piece of equipment and establishing a system that enables time-series checks during abnormalities, you can isolate the causes of reduced power generation more safely and more quickly.

If you want to continuously manage declines in power output from solar PV systems, it's important to create an environment that can handle on-site conditions, inspection records, alert histories, and generation data together. Information that affects both safety and generation—such as grounding and leakage alerts—should be organized in a format that is easy to share among stakeholders, because the easier it is to share, the more consistent the quality of response will be. To avoid overlooking causes of low generation and to efficiently proceed from on-site checks to recording, sharing, and improvement, it is essential to link routine inspections, monitoring data, and reports, and to establish a management system that allows immediate access to the information needed during anomalies.