The neutral conductor is often misunderstood. Some claim it is never live, while others insist it always carries electricity. Both views stem from confusion around what “live” truly means. In reality, even under normal operation, the neutral conductor can be energized. Although it is grounded at the transformer’s neutral point, as long as current flows in the circuit, there will be voltage present across portions of the line. A conductor with current and voltage is, by definition, live.
Not shocking a person does not necessarily mean it has no electricity. A dry-cell battery may not injure someone on contact, but it still stores energy. Similarly, the neutral line in daily use typically feels “safe,” but under fault conditions, it can become as dangerous as the phase conductor.
When the Neutral Becomes Dangerous
A particularly hazardous situation arises when the neutral conductor is broken. If the neutral line is interrupted while loads remain connected, that section of the line can rise to phase potential—commonly 220 V. The connected equipment may appear off, such as a lamp not lighting, yet the neutral point carries lethal voltage. Touching it in this state can cause accidents.
Voltage can exist without a closed loop, but current requires continuity. Thus, when the neutral breaks, current stops, but dangerous voltage still lingers. Misjudging this condition is a frequent cause of injury and equipment failure.
Eight Key Measures to Prevent Neutral Hazards
1. Maintain Balanced Three-Phase Loads
Keep the imbalance within 20%. Excessive imbalance increases voltage loss and power wastage, while also stressing the neutral conductor.
2. Ensure Reliable Connection to the Transformer Neutral Point
Connections must be tight and corrosion-free. For aluminum conductors larger than 16 mm², compression terminals should be used instead of crude wrapping methods, as oxidation quickly undermines conductivity.
3. Prohibit Fuses on the Neutral Conductor in Three-Phase Four-Wire Systems
Installing a fuse risks an unintended neutral break. If it blows, single-phase devices may receive overvoltage, causing damage or fire. For single-phase circuits, however, dual-pole switches with fuses on both phase and neutral are required to ensure safety during maintenance and fault conditions.
4. Maintain Qualified Grounding Resistance
The grounding resistance at the transformer’s neutral point must meet regulatory limits—typically ≤4 Ω for systems above 100 kV and ≤10 Ω below 100 kV. Routine inspection and tightening of grounding bolts are essential.
5. Provide Adequate Neutral Conductor Size and Strength
The neutral should be at least 50–60% of the phase conductor’s cross-section, strong enough to withstand both mechanical and electrical stress. Avoid splices where possible; if unavoidable, joints must be properly executed.
6. Employ Repeated Grounding at Distribution Boxes
Supplementary grounding reduces potential rise during faults. Without it, fault voltage can exceed 150 V—enough to cause fatal shock. With repeated grounding, the same condition may reduce fault voltage to less than 5 V, greatly lowering risk.
7. Prevent Misconnections of Phase and Neutral Conductors
Cross-connection can elevate single-phase loads to 380 V, burning out appliances or motors. In severe cases, it can cause equipment failure due to phase loss or overvoltage stress.
8. Minimize Connectors, Switches, and Terminals on the Neutral Line
Every additional joint raises the likelihood of poor contact and accidental disconnection. Keep the neutral line continuous and robust, with minimal interruptions.
Conclusion
In three-phase four-wire systems, the neutral conductor is far from harmless. A broken or poorly maintained neutral line can carry high voltage, leading to equipment damage and personal injury. Preventive measures such as balanced loads, strong connections, proper grounding, and protective devices like residual-current breakers are indispensable. By treating the neutral conductor with the same caution as the phase conductor, both safety and system reliability can be secured.