GoodWe AFCI Technology Verification

Author: Jonas

2023-09-12 14:05

 

Photovoltaic systems have seen tremendous growth globally as a source of clean, renewable energy. However, electrical fires remain a safety concern. PV systems operate at high DC voltages, and degraded connections, damaged PV modules, and faulty wiring can all lead to electrical arcing faults.

Arcing occurs when electricity jumps a gap between two conductors. This generates high heat that can melt insulation and surrounding materials. Undetected arcs can quickly lead to fires. Historical data shows arcing faults account for the majority of PV fires.

Standard overcurrent protection devices are ineffective at detecting arc faults, since the current is often below the trip threshold. To address this safety gap, arc-fault circuit interrupter (AFCI) technology has been introduced into the latest National Electrical Code (NEC) requirements for rooftop PV systems.

AFCIs can detect the unique electrical signatures of arcing by monitoring current and voltage patterns. When an arc fault is detected, the AFCI will disconnect the PV system from the grid quickly enough to prevent a fire. AFCIs provide a crucial protection layer for rooftop PV safety.

As AFCI adoption increases, it is important for PV installers and consumers to understand how this technology works to prevent fires, comply with code, and uphold best safety practices for PV systems.

 

GoodWe AFCI Technology

GoodWe has gone through a journey of continuous innovation and progress to develop AFCI technology, starting from developing conventional arc fault circuit interrupters to intelligent AFCI devices with advanced algorithms and comprehensive arc detection capabilities. Through years of technical accumulation and experience in Photovoltaics, GoodWe third generation of AFCI was developed, aiming to provide the most optimized solutions.

To stay at the cutting edge of technology and industry trends, GoodWe constantly improves core technologies by following latest IEC & UL standards, closely monitoring the market’s needs, and even envisioning future innovations. By rapidly developing knowledge and solutions ahead of the curve, GoodWe ensures continuity of optimized services and the highest safety levels of PV systems.

To accurately evaluate the performance level of GoodWe AFCI technology, TÜV Rheinland established a verification team to conduct a comprehensive validation and evaluation of related technologies under the commission by GoodWe. The evaluation process of the verification team flow is as shown following:

• Evaluation of Application Demands and Technical Solutions

GoodWe mainly applies the AFCI technology to residential and C&I photovoltaic power generation system products, with clear application scenarios and application demand for related scenarios in policies and standards.

Therefore, GoodWe has proposed corresponding technical indicators and developed solutions as described in Section 3 above. Through the review, the verification team has made the following conclusion: The technical solutions proposed by GoodWe exceed the technical market standard to deal with DC arc faults. The AFCI solution developed by GoodWe provides sufficient hardware and software support for the realization of the proposed technical indicators, and will be tested and verified in the next test and verification phase.

• Performance Verification

Based on the technical indicators developed by GoodWe and the safety classification evaluation requirements aforesaid, the verification team has established the laboratory and on-site test solution with reference to the existing international standards.

 

Performance Verification

Test serial No.	Minimum Iarc (A)	Impp (A)	Vmpp (V)	Voc (V)	Clearance (mm)
1	2.5	3.0	312.0	480.0	0.8
2	7.0	8.0	318.0	490.0	0.8
3	14.0	16.0	318.0	490.0	1.1
4	7.0	8.5	607.0	810.0	2.5
5	18	30.0	318.0	490.0	1.1

Notes:

1. The series arcing is simulated at three points: the starting point of the PV input positive electrode, the middle position of the component and the end of the PV input negative electrode in each test;

2. The characteristics of two types of frame technology modules are simulated at each testing point for testing;

3. All tests are carried out in the analog line with a length of 200 m;

4. The tests above are carried out on two types of inverters with AFCI function: DNS G3 (residential single-phase series inverter) and SMT US (commercial three-phase series inverter), respectively, simulating residential and commercial application scenarios. The test serial number 5 is only conducted on SMT US series;

5. The tests above are completed in the laboratory using the testing equipment such as photovoltaic array simulator, coupling network, line simula- tion network and arc generator.

 

According to the test solution above, the test verification results are as follows through multiple repeated tests:

• AFCI Performance Test and Verification Result

Performance indicator	Result
Test arc type	DC series arc
Arc test range	PV input, output ends and middle of modules
Max. test cable length	200m
Max. input current	30A
Arc test energy	<300J
Shut-downtime	<500ms
Arc test accuracy	100%

 

Conclusion

Based on the results of the technical evaluation and test, the following comprehensive conclusion can be made:

1.       GoodWe’s AFCI technology has technical advancement, superior indicators and reliable and stable performance in the actual test,

2.       The AFCI meets the performance indicator requirements of current mainstream standards such as US NEC 2020 and UL1699B, with some indicators exceeding the standard requirements,

3.       GoodWe’s photovoltaic string inverter integrated with the AFCI function can effectively prevent arc hazards and related fires, and reduce property losses.

 

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