1. What is SPD degradation?
SPD degradation can be understood as the gradual decline in performance of the protection components inside an SPD. When newly installed, an SPD has a certain surge current handling capability and protection level, allowing it to act quickly when a surge occurs and clamp overvoltage within what the equipment can withstand. But as lightning strikes and surge impacts keep occurring, the internal components of the SPD undergo performance changes. In the short term, it may not have completely failed; in the long term, its protection capability may already have declined. The most troublesome aspect of such changes is that they are not necessarily as obvious as a breaker tripping, nor are they necessarily detected in time by manual inspection.
2. Why do SPDs degrade?
SPD degradation usually comes from three sources. The first is lightning strike impact. High-energy surges from strong strikes can cause significant stress on the SPD. The second is surge accumulation. Many sites do not necessarily experience direct lightning strikes frequently, but long-term small surges, switching overvoltages, and induced impacts gradually consume SPD lifespan. The third is environmental aging. Temperature, humidity, dust, corrosion, loose terminals, and other factors also affect the SPD's long-term reliability. Therefore, an SPD is not limited to 'good' and 'bad' states; in between there is a process of gradual degradation and rising risk. Fig. 2: The three main sources of SPD degradation
3. What risks does SPD degradation bring?
Degradation first affects protection capability. When an SPD's protection capability declines, the residual voltage actually seen at the equipment side may rise, making sensitive equipment more vulnerable to surges. In scenarios with many communications, power, control, monitoring, and automation devices, this risk deserves special attention. More importantly, without event records and status data, it is hard to explain after equipment damage: was there a lightning strike before the damage? Had the SPD already degraded? Was the grounding status normal? This is the traceability problem traditional lightning protection often encounters. Fig. 3: The risk chain after SPD degradation
4. Why is it hard for traditional inspection to detect degradation in time?
Traditional inspection and periodic testing are valuable, but they reflect the status at a single moment. Passing on the test day does not guarantee passing after every subsequent strike and surge. The problem at many sites is not 'no testing at all,' but that the testing frequency cannot cover randomly occurring strikes and surges. If an SPD degrades between two inspections and the site has no online status monitoring, the risk can remain invisible for a long time. Fig. 4: Why is it hard for traditional inspection to detect degradation in time?
5. How does digital lightning protection judge SPD status?
The core of digital lightning protection is not simply adding a display module, but building a data system for SPD status and lightning protection events. At least four categories of information need to be recorded: lightning strike and surge events, the SPD's own status, associated status such as grounding and environment, and alarm handling and O&M records. In this way, the site no longer just sees a 'tripped or not' result, but can combine events, statuses, and trends to judge whether risk is rising. From a management perspective, the value of online SPD monitoring is upgrading the lightning protection system from a single test result to a long-term operational archive. Fig. 5: How does digital lightning protection judge SPD status?
6. How does FEXLINK understand SPD health archives?
FEXLINK believes that online SPD monitoring should not stop at 'seeing a status' but should form a traceable health archive. This archive should record what the SPD has experienced, its current status, how the risk trend is changing, and whether an alarm and O&M closed loop has been formed. With this data, lightning protection O&M can move from 'a periodic glance' to 'timely handling when risk changes.' This is also the long-term value of digital lightning protection: enabling the lightning protection system to continuously produce data and making risk status manageable. Fig. 6: Four questions for judging whether an SPD is effective
Conclusion: SPDs need not just installation records, but health archives
SPDs degrade — this is a normal engineering fact. The real question is not whether SPDs age, but whether the degradation process is visible, whether rising risk can be detected, and whether O&M handling has a basis. Traditional lightning protection values 'whether it is installed'; digital lightning protection focuses on 'whether it is still effective.' In the future, lightning protection systems need to move from equipment lists to status archives, and from human experience to data-based judgment. FEXLINK will continue to share content on smart lightning protection, early electrical safety warning, digital power distribution, energy supervision, and industrial IoT. FEXLINK: redefining energy efficiency and electrical safety with data. FEXLINK the Power.
Key points
Definition: Many people still understand an SPD as 'a lightning arrester installed in the distribution cabinet.' Core principle: But an SPD is not a component that remains effective forever once installed. Over long-term operation, it continuously endures lightning strike impacts, switching overvoltages, induced surges, and environmental influences. Applicable scenarios: Communication base stations, wind farms, photovoltaic power stations, data centers, charging stations, park power distribution, and other scenarios requiring continuous operation, online safety, and asset protection. FEXLINK capabilities: FEXLINK builds long-term operational data archives around digital lightning protection, including lightning strike events, surge impacts, SPD status, grounding status, anomaly alarms, maintenance records, and risk trends, so that the lightning protection system continuously produces safety data.
Frequently Asked Questions
What is the core content of the article 'Why Do SPDs Degrade? How Do You Tell Whether They Are Still Effective?' Many people still understand an SPD as 'a lightning arrester installed in the distribution cabinet.' FEXLINK builds long-term operational data archives around digital lightning protection, upgrading the lightning protection system from 'device existence' to 'visible status.'
