What Is a Neutral Point?

The term ‘neutral point’ is officially defined within the IEC 60050-195-2021 as:

common point of a star-connected polyphase system.

60050-195-2021

The term “neutral” used in the requirements and recommendations of international standards, is not this term is defined in the International Electrotechnical Vocabulary or in IEC standards and other documents. It has been replaced in IEC documents by the term “neutral point”, the definition of which has a significant drawback.

As defined by the International Electrotechnical Vocabulary, there is only one neutral point, that of the power supply that supplies the AC electrical system with electricity. Therefore, the term “neutral” should be defined in relation to AC electrical equipment.

The term “neutral” is widely used in international regulatory and legal documentation to refer to a specific live part of a power supply, usually the common live part of a multi-phase AC power source. The neutral is, for example, the common winding terminal of a three-phase generator or transformer connected in a star connection. In a single-phase power supply, the neutral is the middle live part, for example, the middle winding terminal of a single-phase transformer or generator. This live part may be earthed or isolated from earth.

What Electrical Equipment Has Neutrals?

Some types of AC electrical equipment have neutrals, for example: three-phase transformers, generators and electric motors whose windings are connected in star, three-phase electric heaters whose heating elements are also connected in star. A three-phase electrical system may contain dozens, hundreds, or thousands of electrical products with neutrals.

In addition to power supplies, various two- and three-phase AC electrical equipment, the live parts of which are star-connected, can have a neutral. The most common type of such electrical equipment is three-phase electric motors.

You can find neutrals in Figure 1 below (as an example).

TT-system-figure-31f1-iec-60364-1 neutral included
Figure 1. TT system 3-phase, 4-wire with the neutral conductor throughout the distribution system (the figure shows the neutral of the power supply)

The term ‘isolated neutral’ is sometimes used incorrectly in the regulations. If the windings of a three-phase generator or transformer are connected in a delta connection, the power supply has no neutral. The live parts of a single-phase power supply with a single winding, such as the terminals of a single-phase generator, are also not neutral. Therefore, in low-voltage AC electrical systems with a so-called isolated neutral, there may be no neutral as such. In these cases it is more correct to refer to the live parts of the power supply being isolated from the earth.

FAQ

Is Neutral Same as Ground?

No, neutral is not the same as ground. Ground refers to a direct connection to the earth, while neutral is simply a current carrying conductor. In fact, in some electrical systems, neutral is intentionally grounded so that if there is a break in the insulation of a hot wire, the current will have a path to flow through back to the transformer. However, even in these cases, the two terms are not interchangeable.

Does the Neutral Wire Carry Current?

Yes, the neutral wire carries current. The current in the neutral wire is equal to the sum of the currents in the other wires. This is because the voltage in the neutral wire is the same as the voltage in the other wires. The current in the neutral wire is used to cancel out the current in the other wires. This is how power is conserved.

What Does a Neutral Wire Do?

Neutral wires are used to connect the different parts of an electrical circuit together. The purpose of a neutral wire is to provide a path for the electricity to flow back to the ground if there is an overload or short circuit. Without a neutral wire, the electricity would have nowhere to go and could cause a fire.

The neutral wire carries currents back to the transformer or power plant where the electricity originated. This is why it’s important to have a well-grounded electrical system: if there were ever a break or fault in the neutral wire, all of the current would be diverted into the earth, causing a dangerous situation.

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