RC Overvoltage Absorption Cabinet

Opening Every switching operation of a vacuum circuit breaker releases a steep-front voltage surge that can reach three to four times the system peak. On 6–35 kV networks this surge attacks motor windings, transformer insulation and cable terminations long before any protective relay reacts. The RC Absorption Cabinet places a series resistor-capacitor branch across each phase at the point where the surge is generated, so the overvoltage is clipped and damped at source instead of travelling down the feeder.

How it works
Each phase carries a purpose-built power capacitor in series with a damping resistor. The capacitor slows the rate of rise of the recovery voltage and caps the surge amplitude; the resistor absorbs the high-frequency energy and suppresses reignition, which is what turns a single restrike into a destructive overvoltage cascade. A bleeder resistor discharges the capacitor to a safe level after de-energising, a high-voltage fuse clears any internal short circuit, and an optional voltage transformer gives a live indication of the branch. A door-mounted intelligent controller keeps the enclosure free of condensation, the most common cause of surface flashover in outdoor installations.

Construction
2.0 mm galvanised steel sheet, CNC bent and welded, polyester powder coated (RAL 7035 standard, other colours on request)
Segregated HV compartment, hinged front door with lock and stainless hardware
Overhead HV bushing for cable or bar entry; louvred ventilation with insect mesh; earthing terminal and lifting lugs
A3 wiring diagram pocket bonded inside the door; phase-marked (R/Y/B or L1/L2/L3) capacitor stacks on insulated supports
Indoor IP30 / outdoor IP54–IP65 versions; anti-condensation heater and controller standard on outdoor units
Key features
Series RC branch per phase - clips switching and restriking overvoltage at the breaker outlet
Low-inductance internal layout, short leads, minimal loop area for a fast response
Self-healing metallised film capacitors with internal fuse protection
Non-inductive damping resistors rated for the full discharge duty cycle
HV fuse per phase plus bleeder resistor for safe maintenance
Optional PT / live-line indication and discharge counter
Intelligent temperature-humidity controller with digital display
Bolted, modular cabinets - single unit or multi-cabinet bank for wider feeders

750

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