Turbo Generator Loss of Excitation

The generator's electrical operating characteristic (power or impedance, plotted on a complex plane), can represent the normal and abnormal conditions of the generator as various areas on the plane. Loss of excitation causes a "movement" of the operating point into an undesirable area of the plane. That's where the relay's "impedance circle" setpoints come into play. When the operating point moves into the circle, it is entering a condition the relay is set to detect, and cause a corrective action.

Here's a YouTube video that may help you picture it:

https://www.youtube.com/watch?v=A0GYe2FQmxE

Hello peter,

Thanx for your comment. I already seen this video. I know details about loss of protection. Please read my problem. My question was about different things.

Perhaps this paper will help.

http://store.gedigitalenergy.com/FAQ/Documents/489/GER-3183.pdf

Also look at this.

http://scholar.utc.edu/cgi/viewcontent.cgi?article=1672&context=theses

This has good information.

https://www.slideshare.net/mmuralintpc/loss-of-excitation

Peter already answered the question. I am just extending it:

The criteria is given by arctan(y/x), as y/x is slope (impedances: imaginary/real), and arctan converts slope to angle. This is correct only when x > 0, so the quotient is defined and the angle lies between −π/2 and π/2.

" Developed by a Chinese company "

About the only thing that were really ever developed by Chinese companies are fire crackers and chairman mao jackets.

Other than that, every thing else they make, is a copy of someone else's work.

I got a problem like this before.

A 60 MW, 3000 RPM steam turbine generator with a Chinese made yuchai engine （ could not remember the exact model name） went into motoring and the protection system failed to catch it (DC failure). The machine was tripped manually and the it was resynchronized. But the generator vibrations shot up.
The machine was stopped and the generator and the turbine bearings were inspected and found ok. It was then restarted and the vibrations were found to increase with the excitation. On tripping the excitation, the vibration went down immediately obviously indicating electrical issues.

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