Protection Against Ground Faults for Photovoltaic Applications

Introduction

Protection against ground faults in photovoltaic applications is provided by:

• insulation monitoring devices

• overcurrent ground fault protection

Double Ground Faults

To break a fault current at the operational photovoltaic system voltage, a minimum number of poles must be working in series. The minimum number of poles is a function of the system voltage and voltage rating per pole of the protective device (circuit breaker or switch-disconnector).

Under certain conditions, a double ground fault can occur in photovoltaic systems that are isolated from ground. If an initial ground fault (initial isolation breakdown to ground) exists, without being detected and cleared, a second fault (second isolation breakdown to ground) can lead to a double fault.

Depending on the location of the faults, it is possible that a subset number of the required poles only be involved in the interruption of the fault. Not designed for this situation, property damage or personal injury may occur.

To prevent such double fault scenarios, it is therefore imperative to detect the initial isolation breakdown (first fault) using an isolation monitoring system and clear without delay the initial isolation breakdown to reduce the risk of double fault.