5 checks for communication errors and data loss that cause reduced power generation

When you suspect low power output, the usual culprits are dirty panels, shading, equipment failures, wiring faults, and weather conditions. However, in practice, even when the generation equipment itself shows no major abnormalities, communication errors or data gaps can make output appear low or delay the detection of problems, allowing actual losses to expand.

In particular, in industrial solar power generation facilities, on-site generation equipment, measurement instruments, monitoring devices, communication lines, management interfaces, and report data are connected via multiple routes. As a result, if communication is interrupted at any point, there can be a discrepancy between the actual power output and the power output displayed on the screen. To correctly determine the cause of low power output, it is essential not only to inspect the generation equipment but also to check the flow of data itself.

In this article, we summarize five viewpoints that field staff should check regarding communication errors and data loss that lead to reduced power generation. Use this as a framework to distinguish whether low power generation is caused by equipment faults, data anomalies, or a combination of both.

Table of Contents

• Organize the relationship between communication errors and decreased power generation.

• Check the difference between the power generation on the monitoring screen and the on-site measurement.

• Cross-check the time periods of data loss with the time periods of reduced power generation.

• Check the status of the communication lines and measuring instruments.

• Verify delays in detection caused by alerts not being sent.

• Review the aggregated values and reported figures after data recovery

• Summary

Clarifying the Relationship Between Communication Errors and Reduced Power Generation

When power output is low, the first thing to clarify is whether a communication error is actually reducing the power output itself, or whether the output only appears low. If you begin inspections without making this distinction, you may proceed to unnecessary replacement decisions even though the on-site equipment has no major faults, or conversely overlook a real decline in generation by attributing it to a communications problem.

In solar power generation systems, the amount of electricity generated is typically recorded by on-site metering equipment, and that data is sent via communication devices to monitoring screens and management systems. If communication is interrupted along this chain, phenomena can occur such as the generation appearing as zero on the screen, values not being updated for a certain period, gaps in historical data, or daily and monthly totals appearing lower than they actually are. In such cases, even though the generation equipment is operating, the generation may appear low because the data are not being received.

On the other hand, communication errors can sometimes be involved in actual losses. For example, if an anomaly cannot be detected by remote monitoring, responses to stopped equipment or circuits that are in a disconnected state may be delayed. Even when the drop in power generation itself is due to equipment shutdowns or grid-side conditions, discovery can be delayed by communication errors, resulting in a longer loss period. In such cases, communication errors, while not the direct cause of reduced generation, become a factor that enlarges the losses.

Furthermore, for some equipment, control and measurement information may depend on the communication path. It is not the same for all equipment, but if control information, status monitoring, alarm signals, or the acquisition of measured values are not performed correctly, it can hinder understanding of operating conditions and decisions about recovery. Therefore, it is important not to dismiss communication errors as merely display issues, but to verify what impact they have on overall operations.

When consulted about low power generation, first distinguish whether the generation performance for the period in question is genuinely low or only appears low on the monitoring screen. Then cross-check the on-site cumulative energy, the measurement instruments’ records, equipment operation history, the monitoring screen’s update times, and the conditions used to produce daily and monthly reports. Conducting this initial review makes it easier to decide whether to prioritize an on-site inspection or to first check the communication paths and data processing.

What you should pay particular attention to is that some systems automatically fill in past data after communications are restored, while others leave gaps unfilled. If data were stored locally during the communication outage, the generation figures may be reflected after restoration. However, depending on storage capacity, settings, and the length of the outage, past data may not be fully recovered. Therefore, even if power generation was shown as low at the time the communication error occurred, you need to check how the subsequent aggregated values changed.

Verify the difference between the power generation displayed on the monitoring screen and the on-site measured values

When suspecting communication errors or data loss, the most basic check is to compare the power generation shown on the monitoring screen with the on-site measured values. If you judge generation to be low by looking only at the monitoring screen, you may misinterpret communication or aggregation problems as equipment failures. Conversely, if you look only at the on-site measurements and conclude there is no problem, there is a risk that the management-side records and reported values will remain incorrect.

What should be checked on-site are the accumulated energy values held by the power generation equipment and measuring instruments, the instantaneous generated power, operating status, fault history, shutdown history, and so on. If the values displayed on the monitoring screen differ significantly from the values shown locally, there may be a problem somewhere in the communication route, data acquisition interval, aggregation processing, unit settings, or time settings. It is not simply a case of communication being cut off; data may be arriving but not being imported as the correct item.

When comparing, it is important to look at the same time, the same units, and the same scope. For example, on-site measurements may be device-level power output, while the monitoring screen may show aggregated values for the entire plant. Also, the on-site display may show instantaneous values, whereas the monitoring screen may show averages or cumulative/totals over fixed intervals. If you compare without understanding these differences, you may mistake normal discrepancies for anomalies.

When comparing daily power generation, we look not only at the current day but also at the previous day, the previous week, and days with similar weather. If there is a communication error, generation for a single day may be displayed as extremely low. In some cases the system was actually generating during the day, but gaps in the monitoring data for a period cause the daily report’s generation figure to be low. In such cases, checking how much the on-site cumulative reading has increased since the previous day makes it easier to confirm whether generation actually occurred.

Also, in facilities with multiple power generation devices, compare not only the total generated power but also the values for each device. If only a specific device shows low generation and, at the same time, only that device's communication is unstable, measurement or communication problems are suspected. Conversely, if the communication status is normal but only a specific device's generation remains consistently low, other causes such as shading, soiling, circuit abnormalities, or device malfunctions should be considered.

When checking discrepancies between the monitoring screen and on-site measurements, it is important not to regard the values shown on the screen as correct without question. The monitoring screen is convenient, but it only receives and displays on-site data. If there is a problem in any of the stages—acquisition of raw data, communication, conversion, aggregation, or display—the numbers you see may differ from reality. Before concluding that power generation is low, you need to confirm that the data have been correctly delivered, correctly aggregated, and correctly displayed.

Cross-check the time periods of missing data with the time periods of reduced power generation

When investigating low power generation from the perspective of communication errors or data loss, overlay the periods when data loss occurred with the periods of reduced power generation. The mere presence of missing data alone does not allow you to determine a relationship with reduced power generation. Cross-check the times of missing data, their duration, frequency of occurrence, and the pattern of power decline to see what relationship exists.

If data are missing during daytime power-generation hours, the power generation shown in daily and monthly reports may be calculated as lower. In particular, if data around noon on sunny days are largely missing, the displayed impact relative to the actual generation can be significant. On the other hand, if data are missing at night, the aggregated generation totals may not be greatly affected. In other words, it is important not only whether there are gaps, but whether those gaps occur during the hours when generation is occurring.

Pay attention to the pattern of missing data. If short missing segments repeat at regular intervals, possible causes include unstable communication lines, measurement device restarts, or inconsistent data transmission interval settings. If missing data occurs continuously for an extended period, power outages, communication equipment shutdowns, line failures, power loss of on-site devices, or configuration changes may be involved. Also check whether the missing data occurs only on specific days or at the same time each day.

If data are missing at the same time every day, suspect periodic factors such as network congestion, device processing timing, power supply conditions, and the temperature environment. For example, communication devices can become unstable during daytime periods when the temperature inside the panel rises. Also, if the power for communication devices or measurement instruments depends on a particular power circuit, the condition of that circuit can cause data acquisition to become unstable.

When you overlay generation graphs with records of data gaps, it becomes easier to tell whether a drop in generation is caused by an actual shutdown or by a display-related data gap. Even if the generation on the graph suddenly falls to zero, if the equipment operation logs for that period are normal and the on-site cumulative meter readings are still increasing, the likelihood of a data gap is higher. Conversely, if the generation is zero and there are simultaneous equipment stop logs or error records, it can be regarded as an actual shutdown.

Also, care is required when reflecting time periods of missing data in monthly aggregates. Even short-duration gaps can produce noticeable differences in monthly reported values if they are concentrated during periods of high power generation. In particular, if similar gaps persist over multiple days, there is a risk the facility will be evaluated as having lower generation than it actually produced. Before assessing the performance of the facility, it is necessary to account for the impact of missing data.

When checking for missing data, record not only whether data are missing but also which time period, which device, and which items are missing. Whether only the generated power is missing, multiple values such as voltage and current are missing simultaneously, or device status signals are also missing changes how you assess the cause. If multiple items are missing at the same time, a problem with the entire communication path is suspected; if only specific items are missing, measurement settings or data conversion issues should also be considered.

Check the status of communication lines and measurement equipment

If communication errors or data loss are suspected, check not only the communication line but also the condition of the on-site measuring instruments and communication equipment. Various factors can underlie an indication of low power generation, such as intermittent line disconnections, unstable power supply, device reboots, configuration mismatches, time drift, and insufficient storage capacity. Even if the screen displays a communication abnormality, the cause is not necessarily the external line alone.

The first thing to check is the power status of the communication devices and measurement instruments. If the power is unstable, the devices may repeatedly reboot and data may be interrupted. Monitoring devices for power generation equipment are often installed in outdoor panels or inside on-site equipment, and can be affected by temperature, humidity, condensation, dust, cable degradation, loosened terminals, and similar factors. Even if the power indicator appears normal, communication can be interrupted by momentary voltage drops or poor contacts, so check both the appearance and the history.

Next, check the connection status of the communication link. When the link is completely down it is easy to detect, but in practice intermittent disconnections can be harder to confirm. Because the screen updates occasionally and may look normal at a glance, small data losses can accumulate and affect the accuracy of daily and monthly reports. If you can check signal strength, connection history, the number of reconnections, and the logs of the communication equipment, cross-reference them with the periods when power generation is displayed as low.

The configuration of measurement equipment is also important. Even if communication is functioning normally, incorrect settings—such as the types of values collected from generation equipment, acquisition interval, units, scaling (multiplier), handling of cumulative values, or the date-changeover time—will prevent generation output from being aggregated correctly. For example, if the acquisition interval is too long, short-term fluctuations are difficult to capture. If the multiplier setting is wrong, the reported generation may appear lower than it actually is. If the clock setting is incorrect, generation may be recorded on a different day.

Time discrepancies are an easily overlooked item to check. If the clocks on on-site equipment, communication devices, monitoring screens, or the reporting side are out of sync, comparisons of generated power will not be accurate. Especially for aggregations that span days or when viewing graphs at regular intervals, time discrepancies can cause misidentification of the periods of reduced generation. It is important to verify that the day you judged to have low generation is not shifted from the day on which the data were actually recorded.

Also, if the on-site equipment has a mechanism to temporarily store data, check the storage capacity and retention period. If communication is interrupted but data remains on-site, it may be transmitted in bulk after restoration. However, if the outage continues for a long time or the storage capacity is exceeded, some data may be lost. In this case, after restoration the power generation may only partially recover, or the missing data may remain.

When checking communication lines and measuring equipment, on-site work records are also useful. Compare the dates of activities such as equipment inspections, work inside panels, replacement of communication devices, configuration changes, power outage work, mowing, or cleaning with the dates when data loss occurred. Temporary power shutdowns during work, touching communication cables, or changing settings can later appear as data loss. Rather than looking at days with low generation in isolation, checking what was done on-site before and after those days makes it easier to narrow down the cause.

Verify delayed detection due to alerts not being sent

When communication errors or data loss contribute to reduced power output, a particular concern is delayed detection caused by alerts not being sent. Even if a power generation asset actually stops or experiences an anomaly, if communication is interrupted that information may not reach the operators. As a result, the time until the anomaly is noticed can be extended, and the loss of generated power can become larger.

In remote monitoring, mechanisms are sometimes used to notify conditions such as equipment stoppage, occurrence of anomalies, decreased power generation, and communication interruptions. However, notifications are only delivered after the on-site equipment captures the condition, the communication device transmits the data, and the management system evaluates the conditions. If any of these steps fail, an abnormality that should have been reported may not be delivered. If a period of low power generation persisted for a long time without any notification, it is necessary to check the notification criteria and the communication status.

When verifying delayed detection, separate and organize the time the anomaly actually occurred, the time it was reflected on the monitoring screen, the time the person responsible became aware, the time on-site response began, and the time recovery was completed. Treating these as a single timestamp makes it impossible to determine where the delay occurred. For example, if equipment stopped in the morning but notifications did not arrive until the evening, the primary cause of the reduced power generation is the equipment stoppage, while the factor that increased the losses is the delayed notification.

We also review whether the notification conditions match the actual situation. Even settings that notify when power generation falls below a certain threshold can generate too many alerts in cloudy or rainy weather, so the conditions may be set too loosely. As a result, it can become harder to receive notifications when a genuine abnormality occurs. Conversely, if the condition for notifying communication outages is set too short, minor interruptions increase the number of alerts and important abnormalities can be overlooked. It is important to adjust notification conditions to match on-site operations so they are neither excessive nor insufficient.

Even if there is a mechanism that notifies of a communication outage itself, that notification is not necessarily received reliably. The notification of a communication outage can be delayed because communications are down. In addition, due to changes in notification settings, personnel reassignments, restrictions on receiving emails or messages, or holiday response arrangements, notifications may be generated but not actually seen in practice. When low power generation persists, it is necessary to check not only for technical communication errors but also for operational issues.

To prevent missed alerts, it is effective to have a daily checking mechanism rather than relying solely on abnormal power generation notifications. For example, regularly checking the previous day’s generation, comparing with similarly sized facilities, confirming whether generation seems inconsistent with the weather, and checking communication status makes it easier to notice anomalies even if notifications are missed. In particular, when low generation continues for several days, do not assume there is no problem just because no notification has arrived; it is important to verify actual performance data and on-site conditions.

At facilities with communication errors, the reliability of alerts themselves can decline. When notifications fail to arrive, arrive late, arrive in batches after recovery, or the same notification is repeated, it becomes difficult for the staff in charge to make decisions. If such conditions persist, important anomalies can become buried and responses may be delayed. To prevent a decrease in power generation, it is necessary not only to ensure the performance of the generation equipment but also to stabilize the communications and notification systems that enable early detection of anomalies.

Review aggregated and reported values after data recovery

After communication errors or data loss occur, it is important not to consider the matter resolved simply when communications are restored, but to review the aggregated values and reported figures. Even if the monitoring screen begins updating again, the data for the missing period may not have been correctly filled in. An assessment that generation was low can change after re-aggregation following recovery.

First, confirm whether the generation for the missing period was later reflected. For systems that transmit data stored locally after recovery, daily generation that initially appeared low may be corrected later. In that case, what was judged as a generation drop may actually have been unreflected data. Conversely, if the data for the missing period does not return even after recovery, you should consider corrections or annotations using on-site cumulative readings or other records.

Numbers used in daily reports, monthly reports, management ledgers, internal reports, and customer-facing reports are not necessarily updated at the same time as the values displayed on the monitoring screen. Even if the screen has been backfilled, reports that have already been issued may still contain outdated aggregated values. If data are backfilled after issuing a report indicating low power generation, you need to record which reported value should be treated as the official value and which periods experienced communication outages.

When reviewing aggregated values, pay attention not only to power generation but also to related indicators such as equipment utilization rate, the difference from expected generation, abnormal downtime, and estimated losses. If the underlying data for power generation are missing, these indicators can also become inaccurate as a result. In particular, when evaluating low generation as an equipment performance issue, including apparent declines caused by data gaps can lead to misguided improvement decisions.

Also, it is important to clarify the method of data imputation. Whether missing values are back-calculated from on-site cumulative totals, estimated from surrounding values, or treated as missing and annotated will change the meaning of the report. Treating estimated values as if they were measured values makes later explanations difficult. When investigating the causes of low power generation, it is essential to distinguish and manage measured values, imputed values, estimated values, and missing values.

In installations that experience repeated communication errors, monthly and annual evaluations can be affected. Even short-term data losses, when accumulated, can cause differences in annual power generation estimates. When analyzing a declining trend in power generation, comparing months with many communication losses and months with few under the same conditions can lead to conclusions that differ from the actual condition of the equipment. When reviewing power generation trends, you should also verify the data completeness for each period.

When reviewing reported figures, explaining them to stakeholders is also important. Separate and explain whether the low-looking generation output was caused by communication loss, whether generation was actually low and discovery was delayed by communication errors, or whether both were involved. Without this clarification, facility managers, maintenance personnel, management, and customers will have mismatched understandings. It is important not just to correct the numbers, but to be in a position to explain why those numbers occurred.

Summary

When power output is low, communication errors and data loss are checks that are easily overlooked. Even if the generation equipment itself is functioning normally, interrupted communications, missing data, or incorrect aggregation can make the output appear lower. Also, even when equipment has actually stopped or is malfunctioning, communication errors can prevent notifications from being delivered, delaying detection and allowing losses to escalate.

What's important is not to attribute a decline in power generation solely to equipment failure. Compare the generation shown on the monitoring screen with on-site measurements, correlate the periods of missing data with the periods of generation decline, and check the status of communication lines and measurement devices. Furthermore, confirm whether alerts were correctly sent and whether aggregated and reported values were properly reviewed after communications were restored; this makes it easier to isolate the cause.

The issue of low power generation needs to be examined from both the on-site phenomena and the numbers shown on the management dashboard. By separating and organizing whether the site is generating power but the data are not being received, whether generation has actually stopped, or whether it took a long time to notice the drop in generation, you can reduce unnecessary inspections and incorrect judgments.

In daily operations, a system that lets you check communication status, data loss, on-site measurements, power generation trends, and notification history together is useful. To detect declines in power generation quickly and correctly isolate their causes, it is essential not only to inspect equipment but also to maintain the reliability of records and data.

If you want to continuously monitor the condition of power generation equipment and reduce oversights caused by communication errors or missing data, it is important not to rely solely on the numerical values on the monitoring screen but to combine on-site verification with data management. To promptly identify the causes of low power output, verify the consistency of inspection records, monitoring information, communication logs, and reported values, and establish an operational framework that preserves the basis for decisions.