This thread is devoid of all speculation, conjecture, theory, guessing, bluffing, etc, that we have seen lately. All, including PtPs, are invited to participate:

Two 100MW, 60Hz power plants, a 1/2 mile apart, are to be interconnected in a substation located midway between them via an SF6 circuit breaker. But, they were previously connected together by another circuitous route some 100 miles long. The questions, should you decide to take on the task, are:

1) Would you close the breaker!

2) If yes, why?

3) If no, why not?

Regards, Phil Corso

 

>1) Would you close the breaker!
>
>2) If yes, why?
>
>3) If no, why not?
>
>Regards, Phil Corso

I am not sure how to picture this in one line diagram and I am an operator. I assume that there are no generator breakers and both generators are synchronized via a breaker in GIS to the grid. If that is the case I think you can close the breakers if you match the voltage, phase angle and frequency either side of the open GIS breaker. Generator voltage has be higher then line(grid) voltage. waiting for all interesting inputs, thanks Phil for starting this thread.

 

Sardar9... good start. Reur attempt to "picture" the situation, imagine a 100 mile loop, which is "open" at the substation between the two plants.

Here is hint No. 1, "A wave of any frequency is still a wave!"

Phil

 

Sorry, Sadar9... Hint No. 1 should have read, "A SINE-wave... !

Phil

 

I minimize voltage difference then I just close it. Synchronizing is not required since their sin waves are already in phase.

 

I minimize voltage difference then I just close it. Synchronizing is not
required since their sin waves are already in phase.

HUH?

 

Nam & Bob... both of you are wrong!

Hint 2: The generators are, indeed, synchronized!

Phil

 

Sorry Bob... I did not see your response, "HUH?" I guess that was directed at Nam!

Phil

 

> But, they were previously connected together by another circuitous route some 100 miles long.

I am not sure about the above sentence, they were or they have been? if that is the case, I will not close the breaker because its paralleled through other breaker.

it will increase the fault current to double!

Sunil

 

Sunil... to clarify your understanding, they were and still are, connected via the 100-mile circuit.

Hint No. 3: phase-to-phase voltage magnitudes are equal!

 

Now it becomes very tricky. Voltages are equal. They are in phase. I'm supposed the area they serve have already linked the two generators.

If we close the breaker then we make another loop. This is not the answer. Just to get the correct configuration the system of interest.

 

Nam... No, you do not make a second loop!

Hint No. 4: Closing the breaker just closes the loop!

Phil

 

Hi Phil,

My thoughts:
1. The impedance of the 100 mile transmission line is different to one that is just 1/2 a mile long. You cannot close the breaker without matching the impedance of the the new interconnection.

2. There will be reflections in the loop which will cause some problems.

Not being an electrical engineer, I may be way off the mark here.
Look forward to reading the solution.

Regards
Sumeet

 

Sumeet... A1) No! A2) No!

Hint no. 5: Read Hint No.1 again!

Phil

 

Gentlepeople... don't quit so soon!

To simplfy problem, here is Hint No. 6:

Isolate one of the two generating plants, so that the entire 100 mile line is served from a single generating plant.

Beware The Ides of March, Phil Corso

 

> To simplfy problem, here is Hint No. 6:

> Isolate one of the two generating plants, so that the entire 100 mile line
> is served from a single generating plant.

If you synchronize the second one, then two generating plants serve the 100miles load center. That is normal. If you close breaker one of the units to serve the nearer load center I supposed that is still normal.

Can we close the second breaker? How to close the second breaker? Having no clue yet.

 

Nam… whether or not the second generator is on line is incidental. Only one is necessary to solve the puzzle.

Phil

 

To those who are interested in learning the solution to the Electrical Power Transmission puzzle, contact me off-list!

Phil (cepsicon[at]AOL[dot]com)

 

Let me try to get this right

1. You MUST NOT close the breaker.

2. Reason being, let me phrase it as simple as possible so that most people can comprehend it. Although both of the generators are indeed synchronized by the line "far far away", AC sine waves nevertheless goes up and down. This means a person must NOT close the breaker without the sync check relay. This function is important because the breaker can only be closed when the sine waves of both "running" and "incoming" are matched. Although the voltage (RMS or Vpp) and frequency are indeed the same for both generators running in sync, any person without the assistance of a oscilloscope or sync check relay would not be able determine when both sine waves are the same at the same point.

I hope I'm correct. Please correct me if I'm not.

 

SD... you are on track. Ignoring charging-current and OVH line-impedance both ends are indeed at the same frequency and voltage.

However, one of the parameters the Sync-Check relay measures IS NOT within limits.

BTW, because of the high number of negative PtP responses aimed at my posts the answer to the puzzle will only be revealed by direct contact with me:

cepsicon[at]AOL[dot]com