Two Common Faults and Solutions in Residual Current Circuit Breaker Applications.

Residual Current Circuit Breaker (RCCB) Technical Guide

An RCCB is an automatic switching device that trips when leakage current exceeds a preset threshold. Common types include:

Voltage-operated RCCBs: Used in unearthed low-voltage systems (transformer neutral ungrounded). Detects ground potential rise during faults.

Current-operated RCCBs: For earthed systems, subdivided into:

Electromagnetic type

Electronic type
These detect leakage current via zero-sequence current transformers (ZCT).

Common RCCB Faults & Solutions

Fault 1: Immediate Tripping After Activation

Incorrect ZCT wiring: Ensure all phase conductors + neutral pass through ZCT in same direction.

Mixed protected/unprotected circuits: Isolate circuits with/without RCCB protection.

Line-to-ground loads: Eliminate unauthorized live-to-earth connections.

Neutral grounding conflict: Remove duplicate neutral grounding points.

Defective unit: Replace RCCB if internal fault confirmed.

Fault 2: Nuisance Tripping

Overvoltage transients:

Install time-delay/voltage-surge resistant RCCB

Add RC snubber circuits or surge suppressors

EM interference: Relocate RCCB away from high-power equipment.

Ground loop currents:

In parallel transformers: Remove redundant grounding

For parallel feeders: Operate circuits separately

Degraded neutral insulation: Address insulation faults causing imbalance currents.

Improper grounding: Eliminate neutral re-grounding.

Overload/short circuit: Adjust protection settings if integrated with MCB functions.

Note: All corrective actions should comply with IEC 61009 standards for RCCB installations.