Sensors - PA
⚡ Closed Toroid (CBCT)
A closed toroid
is a solid, one‑piece core‑balance current transformer (CBCT)
used with Vigirex
and other ELRs to detect earth‑leakage current with maximum sensitivity and accuracy.
All live conductors (L1, L2, L3, N) must pass through the toroid; the earth conductor must not.
🟦 What a Closed Toroid Is
- Solid magnetic core — no hinge, no split.
- High‑accuracy CBCT — ideal for low‑level leakage detection.
- Used with Vigirex relays — feeds residual‑current signal to the ELR.
🟧 Why Closed Toroids Matter
- Highest sensitivity — stable detection down to low mA.
- Best accuracy — continuous magnetic path = minimal error.
- Reduced nuisance tripping — essential for selective schemes.
- Robust in harsh systems — handles harmonics, high currents, long cables.
🟨 Closed vs Split‑Core (Quick View)
| Feature | Closed Toroid | Split‑Core |
|---|---|---|
| Accuracy | Very high | Lower |
| Sensitivity | Excellent | Moderate |
| Installation | Requires cable disconnection | Clamp‑on, easier |
| Industrial use | Preferred | Retrofit / temporary |
🟩 Installation Rules (Critical)
- All phases + neutral through CT
- Earth conductor outside CT
- Correct polarity(P1 → load)
- No downstream N‑E bond
- One circuit per toroid
Violations cause false trips or failure to trip.
🟫 Typical Sizes
- 30–80 mm — small feeders
- 120–200 mm — MCCBs
- 300 mm+ — busbars / large cables
Rule of thumb: use the smallest diameter that fits → higher sensitivity.
⭐ One‑line summary
A closed toroid is the high‑accuracy CBCT preferred for Vigirex ELR systems, delivering the most stable and sensitive earth‑fault detection for industrial and commercial LV feeders.
