Dynamic Stability Analysis Required? 1

[ThePunisher]

Hi all,

If our plant is only 600V and is off-grid and supplied solely by 3 x 1200 kW Natural Gas Turbine Driven Generators at 600 V operating at 2 out of three at normal operations, do we need to perform dynamic or transient stability? All our motor loads are induction motors and large ones have VFDs.

I was under the impression that we need stability analysis if we have in-plant synchronous generators (or synchronous motors) connected in parallel with grid. Or, if we have in-plant generators (off-grid), interacting with in-plant synchronous motors

 

[davidbeach]

May not matter from a compliance standpoint, but do you want to operate with your eyes open or shut?

 

[ThePunisher]

HI David, I was not able to include "NO", let me re-word...

I was under the impression that we need stability analysis if we have NO in-plant synchronous generators (or synchronous motors) connected in parallel with grid. Or, if we have NO in-plant synchronous motors, interacting with in-plant generators (off-grid)

 

[ThePunisher]

Or probably the dynamic stability is needed between the two or three generators in parallel?

 

[juleselec]

Very unlikely that transient (rotor angle) stability in the traditional sense of the term will be a problem for you, particularly if the GTGs are all identical and there are no synchronous motors in the system. Critical fault clearing times are most likely to be very high as identical GTGs will swing together. However, you may want to run time-domain simulations to analyse things such as frequency stability (e.g. on trip of one GTG, will under-frequency protection relays activate? What are the appropriate setpoints? etc) and motor starting.