I. Lightning Protection Requirement Analysis for Photovoltaic Power Stations Photovoltaic power stations feature large footprints, module arrays exposed outdoors, long DC collection lines and complex grounding systems, making lightning protection a key factor in determining their operating life and power generation efficiency. According to GB 50057-2010 'Code for design protection of structures against lightning' and IEC 61643-11 'Low-voltage surge protective devices - Part 11: Surge protective devices connected to low-voltage power systems - Requirements and test methods', T1+T2 level surge protective devices shall be configured on the DC side of photovoltaic power stations, with the continuous operating voltage Ucpv not lower than 1.2 times the module open-circuit voltage Voc, and the voltage protection level Up lower than the impulse withstand voltage Uw of the protected equipment. A 50MW photovoltaic power station in northwest China is located in a high lightning area with more than 40 thunderstorm days per year, featuring a 1000V DC-side system and a string current of 16A, with combiner boxes having 16 built-in string inputs, raising clear requirements for intelligent, monitorable and maintainable SPDs.
II. FSS Smart Surge Protective Device Selection and Parameters The FEXLINK FSS smart surge protective device is a flagship all-element SPD product with 8 built-in sensor groups, integrating acquisition, measurement, transmission and intelligence in one. In this case, the selection parameters are as follows: nominal discharge current In=20kA (8/20us), maximum discharge current Imax=40kA, voltage protection level Up≤1.5kV, continuous operating voltage Ucpv=1000V DC, response time ≤25ns; configured with 4 temperature sensors (NTC type, 0-150°C with ±1°C accuracy), 3 channels of leakage current monitoring (0-2mA range with 10uA accuracy), 1 channel of lightning strike counting (maximum 9999 counts) and 1 channel of voltage monitoring. The FSS supports dual OLED/digital tube displays, has a built-in fuzzy algorithm for degradation analysis and life estimation, and can upload the 8 groups of sensor data to CW edge computing gateways via RS485/MODBUS-RTU. The product complies with four standards: IEC 61643-11, IEC 61643-21, GB/T 18802.1 and GB/T 18802.21.
III. Combiner Box Monitoring Deployment Scheme The 50MW power station deploys a total of 320 combiner boxes, with each combiner box configured with 2 FSS units (1 for the DC positive pole and 1 for the negative pole), 1 ESM smart lightning protection monitoring terminal and 1 FR three-point method ground resistance monitoring module. The FSS uploads data through dual 4-20mA analog and RS485 digital channels, ensuring local display even when communication is interrupted; the ESM serves as the combiner-box-level data aggregation node, collecting 16 channels of string current, voltage and temperature data through the CAN bus with a sampling period of 100 ms; the FR monitors the combiner box ground resistance in real time with ±2% accuracy in the 10Ω-200Ω range, triggering a local alarm when the ground resistance exceeds the design value (4Ω). All devices are aggregated through the RS485 bus to one CW edge computing gateway shared by every 8 combiner boxes, with a total of 40 CW gateways deployed, and data is uploaded to FEXLINK Cloud for big data analysis.
IV. String-Level Data Acquisition and Anti-Reverse-Power Strategy Traditional photovoltaic power station monitoring stops at the combiner box level, making string-level faults (single-string mismatch, hot spots, PID degradation) difficult to detect early. In this case, FEXLINK pushed the monitoring granularity down to the string level: one ESM is configured for every 16 strings, collecting the four elements of string current (I), voltage (V), temperature (T) and status (S) in real time, with current sampling accuracy of 0.5 class and voltage accuracy of 0.2 class. The CW edge computing gateway has 60+ built-in edge AI algorithms that can identify string mismatch (alarm when difference >5%), hot spot effects (alarm when temperature difference >10°C), PID degradation (insulation resistance
V. Lightning Data and O&M Benefit Analysis In 12 months of operation, the system recorded 387 lightning strike events in total, including 5 strikes exceeding Imax (40kA) that triggered SPD operation alarms; FSS leakage current monitoring found that the leakage current of 3 devices exceeded the 1mA warning threshold, and on-site inspection confirmed degradation, so they were replaced in advance, avoiding inverter damage caused by SPD failure; FR ground resistance monitoring detected corrosion and degradation of 2 grounding grids (rising from 2.1Ω to 6.8Ω), which were repaired in a timely manner, eliminating the high-resistance lightning-attracting risk. After the system became stable, O&M inspection efficiency improved by 60%, unplanned downtime caused by lightning decreased by 73% year-on-year, and a cumulative power generation loss of about 820,000 kWh was recovered in 12 months. Calculated at the local PV feed-in tariff of 0.35 RMB/kWh, the direct economic benefit is about 287,000 RMB, with an investment payback period of 11 months.
VI. Industry Standards and Compliance Implementation This case fully complies with the following standards: GB 50057-2010 'Code for design protection of structures against lightning', GB/T 50064-2014 'Code for design of overvoltage protection and insulation coordination for AC electrical installations', IEC 61643-11 'Low-voltage surge protective devices', IEC 61643-21 'Surge protective devices connected to telecommunications and signalling networks', GB/T 18802.1 'Low-voltage surge protective devices - Part 1: Surge protective devices connected to low-voltage power distribution systems - Requirements and tests', GB/T 19964 'Technical requirements for connecting photovoltaic power station to power system', and GB/T 50797 'Code for design of photovoltaic power station'. FEXLINK's 408 national standard rules are built into the CW edge computing gateway, which automatically generates compliance reports covering 15 key indicators such as operating values, operating time, leakage current and ground resistance after every lightning strike event, for review by power regulatory authorities. The four products FSS, ESM, FR and CW have all passed CE/CCC certification, and the reliability and compliance of the full-stack solution have been verified in actual deployments in 200+ customer projects.
Key Takeaways Definition: The deployment practice of smart surge protective devices (SPD) in photovoltaic power station monitoring refers to an engineering scheme that installs SPDs with online monitoring capability in a graded manner at PV combiner boxes, on the DC side and the AC side, achieving lightning strike event recording, leakage current detection, life warning and string-level data acquisition. Core principle: Based on IEC 61643 and GB/T 18802 standards, Type 1/Type 2 SPDs are deployed on the DC side and AC side of photovoltaic power stations respectively; intelligent monitoring modules collect parameters such as SPD leakage current, temperature and lightning strike count in real time, uploading them to edge gateways and cloud platforms via RS485/MODBUS to achieve SPD degradation trend analysis and life estimation. Applicable scenarios: Applicable to centralized photovoltaic power stations, distributed rooftop PV, and PV-storage integrated power stations requiring lightning protection and string-level monitoring, covering combiner boxes, inverter front ends, DC cabinets and AC distribution cabinets. FEXLINK capabilities: FEXLINK provides the FSS smart surge protective device, FS surge protective device monitor, ESX intelligent edge computing gateway and FEXLINK Cloud PV monitoring platform, supporting all-element SPD status sensing, string-level data acquisition and anti-reverse-power strategies, with deployments completed in projects such as a 50MW photovoltaic power station in northwest China.
FAQ Frequently Asked Questions
What is the deployment practice of smart surge protective devices in photovoltaic power station monitoring? The deployment practice of smart surge protective devices (SPD) in photovoltaic power station monitoring refers to an engineering scheme that installs SPDs with online monitoring capability in a graded manner at PV combiner boxes, on the DC side and the AC side, achieving lightning strike event recording, leakage current detection, life warning and string-level data acquisition.
What is the core principle of the deployment practice of smart surge protective devices in photovoltaic power station monitoring? Based on IEC 61643 and GB/T 18802 standards, Type 1/Type 2 SPDs are deployed on the DC side and AC side of photovoltaic power stations respectively; intelligent monitoring modules collect parameters such as SPD leakage current, temperature and lightning strike count in real time, uploading them to edge gateways and cloud platforms via RS485/MODBUS to achieve SPD degradation trend analysis and life estimation.
