If the Ground Wire Is Cut, Will the Circuit Breaker Trip?

A Practical MCCB Q&A Guide — Powered by SSPD

Q1: If the ground wire is cut, will the MCCB trip?

Short answer: Not necessarily.
A molded case circuit breaker (MCCB) does not rely on the ground wire to trip. It trips when:

• Overcurrent occurs (thermal protection)

• Short-circuit occurs (magnetic protection)

• Accessories detect a fault (e.g., shunt trip, undervoltage trip)

So if the ground wire is cut, the MCCB may still trip, but only when a live-to-neutral or live-to-live fault occurs.
A ground wire mainly provides a safe path for leakage or fault current. If it is cut, the fault current cannot be safely guided to ground, which increases danger but doesn’t stop MCCB from operating.

Q2: When will an MCCB trip if the ground wire is broken?

Even with a broken ground wire, an MCCB will still trip in these situations:

✔ Short circuit between phase conductors

The magnetic trip reacts instantly (2–3 ms).

✔ Overload on the load side

Thermal trip protects the device from overheating.

✔ Direct contact between phase and neutral

This still generates enough fault current for tripping.

However, what becomes dangerous is this:

✘ Leakage to a metal enclosure may NOT generate enough current to trip.

Without a ground wire, the enclosure stays energized (live), and the MCCB will not detect it.
This is why grounding is essential in LV power distribution systems.

Q3: What does SSPD recommend for proper protection?

As a manufacturer deeply engaged in global low-voltage electrical protection, SSPD recommends a three-layer safety approach:

1. MCCB Overcurrent Protection

SSPD CEZC / CNSX / CVS / CNS series MCCB provide:

• 18–55 kA breaking capacity

• Thermal–magnetic or electronic trip units

• High mechanical endurance

• Full compatibility with global LV systems

• OEM/ODM customization for panel builders and OEM manufacturers

2. Reliable Grounding System

Always ensure the grounding path is:

• Low impedance

• Properly bonded

• Tested periodically (earth resistance < 1–5 Ω depending on local standard)

3. Add an RCCB or Earth Leakage Module (ELCB)

For leakage and electric shock protection, SSPD supports external coordination with:

• RCCB

• RCBO

• Leakage modules designed for MCCB integration (upon request)

With these combined, even if the grounding system fails, leakage protection can still operate.

Q4: How does SSPD MCCB behave during a ground fault?

Case A: Ground wire is intact

Leakage current flows safely to earth →
Fault current rises →
MCCB trips rapidly.

Case B: Ground wire is cut

Leakage current has no path to earth, so:

• The enclosure becomes live

• Fault current is low

• MCCB may not trip

• The risk of electric shock increases significantly

This is why SSPD strongly recommends periodic grounding inspection for all customers in the Middle East, Africa, and Southeast Asia—especially in humid, dusty, or outdoor environments.

Q5: What makes SSPD MCCB a safe choice for your electrical system?

SSPD MCCBs are engineered for reliability in harsh global markets:

🔶 High-quality copper contacts

Ensures stable breaking performance even under high ambient temperatures.

🔶 Precise tripping characteristics

Each unit undergoes full calibration and final trip testing.

🔶 Wide accessory options

• Shunt trip (MX)

• Undervoltage release (MN)

• Auxiliary contacts (OF/SD)

• Rotary handle

• Motorized operation modules

🔶 Customized solutions for panel builders

SSPD supports OEM branding, customized printing, and engineering coordination for switchgear manufacturers.

Q6: What should you do if you suspect the ground wire is broken?

SSPD recommends the following steps:

1. Immediately stop using the equipment.

2. Use a multimeter to check continuity of the PE line.

3. Perform an insulation resistance test (≥1 MΩ recommended).

4. Inspect terminal blocks and grounding bars in the MCC panel.

5. Replace oxidized or loose terminals.

6. If needed, contact an SSPD field engineer or local partner.

Remember:

MCCB can protect your system, but it cannot replace grounding protection.

Final Summary

Need MCCB Solutions or OEM Customization?

SSPD has 30+ years of manufacturing expertise, exporting to 80+ countries.

📩 Contact SSPD: [email protected]
🌍 Website: www.shendianele.com