Arc-Fault Protection in PV: Practical Notes for 1000V/1500V Strings

Source: Dev.to

Introduction

High‑voltage PV strings (1000 V and 1500 V) improve system efficiency, but they also make fault management more critical. One of the key issues in these installations is arc faults, which can occur at connectors, cable damage points, or degraded terminations. Unlike short circuits, a series arc may persist without a dramatic increase in current, making it harder to detect.

Arc Faults in High‑Voltage PV Strings

• Location of occurrence: connectors, damaged cable sections, degraded terminations.
• Behavior: A series arc can continue to conduct without a large current spike, unlike a typical short circuit.
• Impact: Persistent arcs can cause localized heating, equipment damage, and fire hazards if not detected promptly.

Standards and Test Methods

Arc‑fault detection standards and test methods are essential for ensuring reliable protection. Many engineers reference IEC 63027, which outlines DC arc detection and interruption concepts for PV systems.

AFCI as Complementary Protection

• Not a replacement: AFCI devices should not be considered replacements for fuses, MCBs, or SPDs.
• Additional layer: They provide an extra protection layer targeting “difficult” faults that over‑current devices may not clear quickly.

Evaluating an AFCI Combiner Solution

When selecting an AFCI combiner, consider the following factors:

1. System voltage rating – ensure compatibility with 1000 V or 1500 V strings.
2. String count – verify the device can handle the number of strings in the installation.
3. Expected string current – confirm the AFCI’s current rating meets the design requirements.
4. Trip mechanism – understand whether the unit trips via a contactor or a breaker.
5. Labeling and documentation – plan clear labeling and maintain as‑built documentation to support operation and maintenance (O&M).