Switchgear Monitoring System — Fiber Optic Temperature, Partial Discharge & Arc Detection Solutions

The six most critical monitoring parameters for medium-voltage and high-voltage switchgear are: (1) Temperature at busbar joints, circuit breaker contacts, and cable terminations; (2) Partial discharge activity indicating insulation degradation; (3) Arc flash — optical and current-based detection; (4) SF6 gas density in gas-insulated switchgear; (5) Busbar primary conductor thermal loading; and (6) Circuit breaker mechanical and electrical health via coil current and contact travel analysis.

FJINNO's fluorescent fiber optic sensors use a rare-earth doped crystal at the fiber tip. The crystal's fluorescence decay rate changes with temperature, and this optical signal is transmitted through a dielectric glass fiber to the monitoring unit. Because no electrical components exist at the measurement point, the sensor operates with complete immunity to electromagnetic interference — making it the only continuously accurate temperature sensing technology suitable for use inside energized high-voltage switchgear enclosures.

Partial discharge (PD) is a localized electrical discharge that occurs at defects in insulation — voids, cracks, or contamination — without fully bridging the gap between conductors. PD activity produces measurable electromagnetic pulses and acoustic emissions months or years before the insulation fails completely. Online PD monitoring detects and trends this activity continuously, providing an extended intervention window that enables planned maintenance before catastrophic insulation breakdown and arc flash.

For a standard MV switchgear cubicle, FJINNO recommends 6–9 monitoring points distributed across three zones: 3 sensors on incoming busbar connections, 3 on circuit breaker terminals (line and load side), and 3 on outgoing cable terminations. Additional sensors are recommended for bus couplers and voltage transformer compartments. A 12-panel assembly typically requires 36–72 total sensor points depending on bus configuration and redundancy requirements.

GIS (Gas Insulated Switchgear) uses SF6 gas as the insulating medium in sealed metal enclosures — monitoring priorities are SF6 gas density, UHF partial discharge inside the enclosure, and temperature at accessible connection points. AIS (Air Insulated Switchgear) uses open-air insulation with larger physical clearances — monitoring priorities are busbar hot spot detection, arc flash protection, and TEV/HFCT partial discharge at exposed insulators and cable terminations.

Sensor installation requires a scheduled outage for safety — typically 2–4 hours per cubicle. However, once installed, the fiber optic monitoring system operates continuously for 20+ years with no maintenance access required. The sensors are maintenance-free and require no battery replacement, recalibration, or periodic servicing — making the installation outage a one-time event with decades of continuous protection as the return.

Yes. FJINNO operates its own manufacturing facility and offers full OEM and ODM services for switchgear manufacturers, EPC contractors, and regional distributors. Custom configurations include: probe length and tip style, channel count, enclosure design, communication protocol, software branding, and multilingual documentation. Contact our engineering team with your switchgear specifications for a custom solution proposal.