TIDUEZ9B July   2022  – April 2023

 

  1.   Description
  2.   Resources
  3.   Features
  4.   Applications
  5.   5
  6. 1System Description
    1. 1.1 Isolated Current Measurement
    2. 1.2 Band-Pass Filter
    3. 1.3 Analog-to-Digital Conversion
    4. 1.4 Arc Detection Algorithm
    5. 1.5 Key System Specifications
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Current Transformer Circuit
      2. 2.2.2 Analog Band-Pass Filter
      3. 2.2.3 Analog-to-Digital Conversion
      4. 2.2.4 Power Supply
      5. 2.2.5 Debugging and Status Indication Options
    3. 2.3 Highlighted Products
      1. 2.3.1 TPS259474
      2. 2.3.2 TPS562202
      3. 2.3.3 TPS745
      4. 2.3.4 OPAx322
      5. 2.3.5 ADS8363
      6. 2.3.6 REF5025
      7. 2.3.7 TMDSCNCD280049C
  8. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware and Software Requirements
      1. 3.1.1 Hardware
      2. 3.1.2 Software
        1. 3.1.2.1 Arc Detection Theory
        2. 3.1.2.2 Software Implementation
    2. 3.2 Test Setup
      1. 3.2.1 ControlCARD Configuration
      2. 3.2.2 Setup for Hardware and Software Validation
      3. 3.2.3 Setup for Arc Testing
    3. 3.3 Test Results
      1. 3.3.1 Test Results of Hardware and Software Validation
      2. 3.3.2 Testing With Arcs
  9. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 BOM
    2. 4.2 Tools and Software
    3. 4.3 Support Resources
    4. 4.4 Trademarks
  10. 5About the Author
  11. 6Revision History

1 System Description

With the increasing amount of solar installations, safety concerns get ever more important. Arcing between high-voltage lines must be detected and the solar string must be de-energized to prevent hazards like electrical shock or fire. Therefore, standards like UL 1699B demand arc-fault protection circuits for all solar systems with rated voltages below 1500 V. This reference design is intended to show a possible implementation for an analog front end for such arc detection purposes. The design does not fulfill the UL 1699B standard by itself.

DC arcing causes an AC noise current in the cabling between a PV string, which is present in a wide spectrum up to several MHz. In this design, a frequency range of 30 kHz to 100 kHz is selected for the arc detection. This range can be restricted further by modifying the band-pass filter or the software, to avoid frequencies with known noise, like the switching frequency of the solar inverter. The signal chain consists of the following parts:

  • Isolated current measurement
  • Band-pass filter
  • Analog-to-digital conversion
  • Arc detection algorithm