Optimizing 3-Phase Power: Bus Bar Replacement Project at Port of Lake Charles

• ENGRstudent
In summary, the speaker is an Electrical Engineering major working on an internship at the Port of Lake Charles. The Port has recently fired its board of directors and the speaker is now trying to pick up the pieces. They are currently working on a bus bar replacement project and are considering either using 1500 amp bars with one feed point or 700 amp bars with two feed points. The speaker has two questions regarding this project, including the required rating for the power feeds and the amount of current needed at each feed point. They also mention that more information about the loads may be necessary to fully answer their questions.
ENGRstudent
Hey guys, I'm an Electrical Engineering major @ McNeese State University in Lake Charles, Louisiana. I only have 60 hours toward my B.S., so forgive me if my questions are too stupid.

I'm currently working on my internship at the Port of Lake Charles. The Port has recently fired its old board of directors because of shady legal dealings and poor management, and we're having to pick up the pieces they left behind, including abysmal record keeping and few blueprints to speak of, so I'll give you as much information as I can come up with. I think I've figured out most of the basic stuff already, but enough background. . .

I'm working on a bus bar replacement project. We have right now 2 runs of 3-phase 1500 amp bus bar (3 current carrying bars and 1 ground) that draw no more than 400 amps @ 480 V under full load. The bars are 700 ft. long and fed at one end by 3 #750 MCM in 4" rigid metal conduit with 1 ground wire (not sure of ground wire's size, can find out if necessary).

We're looking at replacing the existing bus bar with either more 1500 amp bar with the single feed point on the end, or possibly going with 700 amp bar and using 2 feed points to compensate for lower ampacity.

We would need to run another 700 ft. of conduit from the substation to the local disconnect box to the second feed point. My question is two-fold:

1) To run 3 more power feeds, do they have to be rated for 400 A/480 V each all the way out to 700 ft., or since the total load is 400 A, would each wire be rated for 133 A instead (400/3 wires = 133.33)?

2) If we have one feed point at one end, and another feed point at the other end, and we need 400 amps of net current at each end of bar, does each feed point need to be pumping in 400 amps, or does each feed point need to be 200 amps?

You haven't explained enough about the loads to answer your question. Since you're using bars rather than cables, it might be that you tap off load at intermediate points.

p.s. Lake Charles is a great place for Cajun food.

What is 3-phase power?

3-phase power is a type of electrical power distribution system that uses three alternating current (AC) circuits with different phases. It is commonly used in industrial and commercial settings due to its ability to deliver more power with less wiring compared to a single-phase system.

How is 3-phase power different from single-phase power?

In single-phase power, there is only one AC circuit, while in 3-phase power, there are three separate AC circuits with different phases. This results in a more balanced and efficient distribution of power, allowing for higher power output and less strain on the system.

What are the advantages of using 3-phase power?

One of the main advantages of 3-phase power is its ability to deliver more power with less wiring. It also produces a more stable and reliable power supply compared to single-phase power. Additionally, 3-phase power is more efficient and can handle larger loads, making it ideal for industrial and commercial use.

How is 3-phase power generated?

3-phase power is generated by three separate power sources that are out of phase with each other by 120 degrees. These sources are then combined to form a 3-phase power supply. This is typically done by using a generator or transformer.

Can residential buildings use 3-phase power?

While most residential buildings in the United States use single-phase power, some larger homes or high-end appliances may require 3-phase power. However, it is not common for residential buildings to have 3-phase power due to the higher cost and complexity of installation.

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