Overview

The IRMS (Insulation Resistance Monitoring System), often referred to as the Megger function, is used to measure insulation resistance of the series lighting circuit. This feature is available on CCR models equipped with IRMS capability. It allows operators to evaluate the integrity of the airfield lighting loop without external test equipment.

Purpose

The IRMS function measures insulation resistance between the series circuit and ground. It is used to detect ground faults, insulation degradation, cable damage, and moisture intrusion. Low insulation resistance may indicate developing failures in the field circuit.

How It Works

When activated, the CCR injects a test voltage onto the series circuit. The system measures leakage current. The calculated resistance value is displayed on the DCMU. The test is separate from normal current regulation.

Manual vs Automatic Operation

IRMS may be configured to operate manually (initiated by operator) or automatically (periodic monitoring, if enabled). Automatic monitoring may generate warnings or alarms when resistance drops below configured thresholds.

For more details see: Configuring Automatic Megger Tests (IRMS)

For more details see: Performing a Manual Megger (IRMS) Test

When to Use IRMS

Use IRMS when troubleshooting ground faults, performing preventative maintenance, verifying circuit integrity after repairs, or investigating intermittent faults. IRMS provides insulation condition data without disconnecting the field circuit.

Important Considerations

IRMS is not a replacement for external megger testing when required by maintenance procedures. The CCR must be properly configured for IRMS operation. Not all CCR models include IRMS capability.

Safety Reminder

The IRMS test applies voltage to the series circuit. Ensure personnel are clear of the field circuit before initiating a test. Always follow site safety procedures when performing insulation resistance testing.

Related Articles:
Adjusting IRMS Warning and Alarm Thresholds
Interpreting Megger (IRMS) Results

Airport Lighting Company | Type L-828, Type L-829 Ferroresonant Constant Current Regulator