What is the necessity for adding Power system stabilizer (PSS) in EX2100 (GE Excitation system)? In addition to EX2100, what PSS is specifically doing?

 

Sinu ... is the PSS proposed by the machine supplier, or is it an edict from your Regional Reliability entity?

Regards,
Phil Corso

 

Here's a good description of what a PSS does:
http://www.powerapps.org/PAES_PowerSSApps.aspx

If I understand correctly, they dampen low frequency oscillations in the voltage of the power grid, by providing a command to the voltage regulator.

They are required in North America for machines of a certain size. I'm not sure about anywhere else. Any single generator does not *need* a PSS, but without them being on the majority of generators, the grid would be unstable. We had a failed PSS on a 500MW generator (coal fired) and the unit continued to operate with no issues.

 

It was proposed by supplier and it is a part of package. It was not added based on region/location of site.

 

Am ready to accept "that it is dampening low frequency oscillations by signalling AVR". I hope same thing can be done by excitation system also. In that case, what is the need of this?

 

The PSS is an additional function of the AVR. It provides damping to the oscillations in the electrical power in the range of 0.2Hz to 3Hz. The parameters that have to be set depend on the parameters of the generator, the transfer function of the AVR and the impedance of the system.

In the EX2100 this function is already implemented (in some older AVR you have to provide an external PSS). You can connect or disconnect the function whenever you want, but if it going to be activated, a precalibration study should be done to define the settings.

The unit is nearly always able to run without the PSS, unless great oscilation of the frequency specified appears.

I hope I have been helpful

 

vinu,

The EX2100 is an "AVR" (Automatic Voltage Regulator), or, also called an "exciter," or "exciter regulator.

In the past, GE offered PSSs as an optional piece of equipment to their exciter regulators. Now with the EX2100 the PSS functionality is "built-in" to the EX2100 software, and can be enabled or disabled.

I would venture an experienced, scientific guess that to enable the PSS functionality if it wasn't purchased with the original equipment supply that GE or the packager offering the equipment will want an additional sum of money (moulah, dinero, bucks) to enable the software after performing the required system analysis to determine the necessary configuration parameters to meet the desired criteria for the system at your site and with the system your turbine-generator is synchronized with.

Thanks to Sebastian Rebord for the excellent explanation of the purpose of the PSS!

 

The PSS provides damping of Rotor frequency oscillations in various ranges of frequency from 0.05 hertz to 5 Hertz. The addition of this software functionality in a machine should be undertake by carrying software simulations of the Generator performance. The PSS functionality will degrade voltage performance of the AVR but will provide better stability performance of the machine. This is usually a requirement of the electricity regulators to ensure system stability.