Recloser Classification 2025: Interrupting Mediums & Controls

TECHNICAL GUIDE: RECLOSER CLASSIFICATION BY INTERRUPTING MEDIUM & CONTROLS (2025)

1. Classification by Interrupting Medium

Understanding the interrupting medium is essential as it dictates the Operations & Maintenance (O&M) schedule and the equipment’s lifecycle. The shift from oil to vacuum technology represents the most significant evolution in medium-voltage distribution equipment.

A. Oil Interrupters

This is the traditional technology where oil serves a dual critical role:

• Function: It is used to quench the electric arc generated during circuit interruption AND acts as the basic insulation medium.
• Mechanism: Some reclosers with hydraulic controls utilize the pressure of this same oil for timing and counting functions.
• Operational Drawback: Oil degrades over time and with the frequency of interruptions. This necessitates regular oil sampling, filtration, or replacement, resulting in higher O&M costs and potential environmental hazards from leakage.

B. Vacuum Interrupters

This is the modern industry standard for medium-voltage distribution.

• Speed: Provides fast, low-energy arc interruption (typically within 1-3 cycles).
• Longevity: Contact and interrupter life far exceeds that of oil media, often lasting the life of the pole mechanism.
• Safety: Minimizes fire risks associated with oil pressure buildup.
• Mechanical: Reduces mechanical stress on moving parts due to shorter travel distances.

Insulation Note: While the arc is quenched in a vacuum bottle, the external insulation medium (ensuring phase-to-phase and phase-to-ground isolation) can vary:

• Oil
• Air
• Epoxy (Solid Dielectric) – Current trend for maintenance-free operation.

2. Control Systems

The control unit is the “brain” of the recloser, determining grid reliability.

Electronic Controls

Electronic controls have been widely deployed since the mid-1980s (e.g., the Eaton Form 7 series) and remain prevalent in many grids today.

Technical Features:

• Offer programmable protection settings (overcurrent, earth fault, sensitive earth fault).
• Event logging capabilities to assist in post-fault analysis.
• Integration with SCADA for Smart Grid automation and remote switching.

Current Status: While many electronic controls from the 80s and 90s are still operational, the industry is shifting toward microprocessor-based relays for advanced diagnostics, though the fundamental electronic logic remains valid.

3. Quick Technical Comparison Table

4. Operational Recommendations (Actionable Steps)

If you manage a grid containing both technologies, implement the following:

• For Oil Reclosers: Establish a strict maintenance schedule (every 6-12 months) to test dielectric breakdown voltage and oil levels.
• For Vacuum Reclosers: Focus inspection on the mechanical linkage and the external insulation (bushings/tank), as the vacuum bottle itself rarely fails.
• Upgrade Strategy: If you are using legacy hydraulic controls, consider a Control Retrofit. You can upgrade to an electronic control (like the Form 7 or newer) to gain remote monitoring capabilities without replacing the entire recloser tank.