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Participant

Join Date: Feb 2015
Posts: 3

Turbo Generator Loss of Excitation

10/23/2017 12:37 PM

Hello all,

I have seen that many a times "generator loss of excitation" topic has been discussed.

I am curious about the loss of excitation scheme. In our 170MVA steam turbine generator, we used NARI relay. This relay was developed by chinese company. Here is some thing which is much difficult for me to understand.

I want to be more cleared about above equation. How they write this? I am uploading full PDF about loss of excitation protection.

If here someone clear, please share his opinion.

https://drive.google.com/open?id=0B5kf1Ih65AU1Yzg2Vk95ekVORU0

here I shared the file about LOE scheme.

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Pathfinder Tags: LOE Loss_of_Excitation
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Guru

Join Date: May 2010
Location: Liverpool, NY
Posts: 860
Good Answers: 116
#1

Re: Turbo Generator Loss of Excitation

10/23/2017 2:20 PM

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

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Participant

Join Date: Feb 2015
Posts: 3
#2
In reply to #1

Re: Turbo Generator Loss of Excitation

10/23/2017 2:26 PM

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.

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Guru

Join Date: Apr 2010
Posts: 5760
Good Answers: 578
#3

Re: Turbo Generator Loss of Excitation

10/23/2017 6:22 PM
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Active Contributor

Join Date: May 2017
Posts: 20
#4

Re: Turbo Generator Loss of Excitation

10/24/2017 11:23 AM

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.

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Guru

Join Date: Oct 2014
Location: Hemet, Land of milk and honey.
Posts: 1224
Good Answers: 23
#5

Re: Turbo Generator Loss of Excitation

10/24/2017 12:13 PM

" 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.

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Participant

Join Date: Nov 2017
Posts: 3
#6

Re: Turbo Generator Loss of Excitation

11/02/2017 4:22 AM

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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Jose1 (1); niaziel (1); PeterT (1); Rixter (1); shelleyvector (1); tonyhemet (1)

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