Electrical wire color code for three-phase applications provides a standard means of identifying individual wires. Three-phase supply uses either four or five wires. The configuration uses three live lines, a ground wire, and a neutral wire at times. In this article, we will review what the three-phase wire color code is, its benefits, and frequently asked questions on the concept.
What is the Three Phase Wire Color Code?
Wire color codes vary according to the region in line with the governing standard. One color in a certain region could have a different implication in another region. Even within the same region/standard there could be a variety in color codes between single phase and three phase, as well as between high and low voltage.
Thus, it is necessary to be abreast with whatever standard in use to avoid the catastrophic effects of misconnection. For example, In the USA, the National Electric Code (NEC) is different for low voltage (120/208/240V) and high voltage (277/480V) as the table shows.
|Green/Green with yellow stripe/bare wire
|Green/Green with yellow stripe/bare wire
Another common wire color code for three-phase systems is that of the International Electrotechnical Commission, more commonly known as IEC. Most of Europe abides by this code and the table below contains the code details.
Benefits of Wire Color Code
Generally, buildings have electricity coming in at one point before distribution to other parts using a series of wires. Each of these wires serves a function in the circuit, and a color code ensures accurate connection, even in a three-phase application where it can easily get confusing. Some of the benefits of color coding are as follows:
- Decreases the risk of property damage because of wrong connections.
- Reduces downtime that comes for outages and damage to equipment when there is misplacement in connections.
- Repairs are expensive whenever wires are misconnected. Color code helps eliminate this, especially in complex circuits like in three-phase applications.
- The overall system is safer with color coding in use.
Frequently Asked Questions
This section addresses some of the common questions regarding three-phase wire color code.
What colors are wires for three-phase?
The colors for three-phase wires vary according to regional codes or standards. Moreover, the figure below shows some of these common standards.
What is the color code for 240V three-phase?
240V is considered as a low-voltage supply in the USA and has a different color code from high voltage supply. Colors for 240V are black, red, blue, white, and green for line 1, line 2, line 3, neutral, and ground respectively. On the other hand, for 240V single phase, the colors are brown, blue, and green/yellow (bi-colored) for live, neutral, and earth respectively.
What happens if phase and neutral are reversed?
Connecting the phase and neutral reverses the outlet polarity and thereby creates a hazard. Because it causes electricity to flow out of the outlet even though the switch is off. As a result, any appliance connected to such an outlet could shock an unsuspecting user.
What happens if the neutral and ground touch?
Ideally, all three phases of the power supply should be balanced, but that is not the case on most occasions. Thus, the need for a neutral line to return unbalanced load current to the distribution transformer. Typically, this current is minimal, but in abnormal scenarios there could be high level of imbalance, leading to significant current. On the other hand, the ground line offers the least resistance amongst others and removes fault currents from the circuit.
So, if the neutral and the earth touch, current will follow the path of least resistance, which is the earth. As a result, the earth takes more current than intended and no longer protect users from electric shock. This particularly holds true if the phase imbalance is high. This is something that color codes aim to eliminate in three phase systems where multiple wires make the system prone to wrong connection.
How many wires does three-phase have?
The number of wires on a three-phase system depends on the type of configuration in use. Moreover, there are two basic types of three phase configurations: wye and delta.
A delta configuration requires only three wires for transmission. The wye configuration often has a fourth, neutral wire that connects to the earth at the distribution transformer. Each of these configurations refer to the supply, because in a building there is always a ground/earth wire.