dear sir,

myself laxmi, i'm professional to power sector. please solve my problems. my tg capacity is 12 megawatt. when my generation is 11mw, import is 1mw at that mean time if grid breaker got tripped then my TG breaker got tipped to over frequency fault where as load of app. 10mw is avail. so plz lead me to a right solution by which i can save my TG from above problem. tg make-tdps, turbine make - siemens, abb rem-545 for generator protection, woodward-505 governer panel for turbine.

regards,
laxmikanta

 

I'm going to take a stab at this, but it's a long shot.

You seem to be saying that when your tg gets separated from the grid that it is tripping on over frequency even though there is 10 MW of load available.

If the 505 remains in Droop Speed Control mode when the grid breaker opens and doesn't (or can't) switch to Isochronous Speed Control, then it's very possible that the speed will increase and the unit may trip on over frequency.

It's been a long time since I've worked on a 505, but I think on some of them you can use a discrete contact input to switch the 505 from Droop- to Isochronous Speed Control when the grid breaker opens. So, you'd need to find a contact (best if it were from the grid breaker itself) that changes state when the grid breaker opens, and as soon as the grid breaker opens.

You'll need to ensure that the 505 can indeed operate in Isochronous Speed Control, and that it can be switched from Droop- to Isochronous by a discrete contact input. And that Isochronous Speed Control is properly set up for your machine.

If this isn't what you're looking for, then I don't understand the problem. Simply changing the protective relay setting is not the proper solution, though it's been done at many, many, too many sites around the world, and that does not make it the correct thing to do, either.

Best of luck!

 

Laxmikanta... if the prime-mover's output matched the generator load (ignoring losses) the system should not have sped up! The question to ask, then, is what caused the energy input to increase rotational speed (frequency) so that the over-frequency relay tripped?

A good start to your investigation is to confirm the sequence of events you "observed" via recorded parameters?

Regards, Phil Corso