what are the conciquencies of connecting two three phase source in parallel?

Question

electrical generation system

Answer 1

1. They are out of sync.
2. They don't have the same reference point.

1. Even though they have 3 phase each, those 3 phases might be just a bit more or less out of phase with each other and you would have 6 phases instead of 3.

2. Reference point. A hospital was fed from 2 different power companies. The difference between the 2 created a voltage difference. One might have been 130V and the other maybe 120V. That left a difference of 10V. Plus, their return to ground also effects the voltage. One might have a good ground, where the other might not have a good ground.

Answer 2

Let's get this right, shall we? Paralleling 2 or more 3 phase sources are done all of the time in power generation systems. No phase adjusters, or capacitors, nor resistors or anything else is needed. 3 phase generators are built pretty much the same. There is a device commonly known as a "phase clock" which is used to compare the operation of 2 generators (more properly-alternators). When the 2 are phased correctly, the switch gear switches are closed and the 2 "generators are now on line, and supplying power to the power grid. This happens all of the time, everywhere, at power stations to add power capacity, or to take a "generator" off line. The prime movers, the power device driving the "generator" is able to vary in speed to match up with other 'generators" already in use. If they are not in phase, and the switch is operated, BANG! You'll either blow something up, literally, shut down both generators, destroy one or more transformers, put X number of consumers in the dark, or do all the above.

Answer 3

If they are of the same voltage and frequency you can combine them in parallel by inserting phase shifters. All tubines at any generator house combine, so do the distribution grid switching stations.