Dear gentlemen:

Actually I am working in a private power plant (steam turbine Generator) which produced power and steam to petrochemical plant
Generator load max = 120MW
Frequency = 60Hz
GIS 110Kv

We are connected to the grid with two line 110Kv.

During the last three months we observed that there is something strange, our Steam turbine generator are in Load limiter mode and we faced some perturbation that the of the five STG changed around 4MW each that is mean 16MW total and this change only fluctuation for a couple of seconds and then it normalized.

After investigation I found that only the excitation current of all STG’s changed in the same time and then we have this fluctuation in load but there was no changes in steam flow or Governor valves opening or also frequency.

For your information, the partner have a synchronous motor which consume around 20MW, and during changeover of mol sieve bed there was also changes in the (MAC) synchronous motor load but not a big fluctuation.

My question is why all generators load changed for a short period of time while we are on load limiter mode, and what are the causes.

Thanks

 

Is the MVA remaining constant with the VARS and MWs changing?

 

There is a small changes in VAR (from 45MVAR to 44.86MVAR) and the Apparent power There is a changes, but The excitation current was decreased for all generators.

 

Dear

I checked the excitation current it was decreased a little bit decreased during MW increase which is for me strange and also power factor is the same

 

What was happening to the frequency during this event?

The power produced by a generator is directly proportional to the amount of torque being applied to the generator by the prime mover driving the generator.

However, if the frequency is fluctuating when load control is selected that could be causing a problem. You say a very large motor was changing load at the same time. If the grid frequency was also unstable at the same time, and if the load limiter was active that could explain the problems you are describing.

But, really, there's a lot of information we don't know about your site and how it's controlled and operated so it's very difficult to say for sure exactly what happened.

 

What is the THD (total harmonic distortion)?

 

I have a similar experience in regard to this please hiw can I solve this problem...my engine is 3.5mega if running on high loaded of 2.5mega it will suddenly dropped to 600kw which it will begin to fluctuate until we reduce or it can off on its own..the AFR Stepper will go bellow the condition

 

A synchronous electric generator is a device for converting mechanical power in the form of torque to amperes--in the same way an electric motor is a device for converting amperes into mechanical power in the form of torque.

So, if the output of the generator suddenly drops that means the torque input to the generator from its prime mover (reciprocating engine, or turbine (gas or steam or hydro turbine) suddenly dropped.

Many people think that the exciter, sometimes called an AVR, (the component that controls the voltage of the synchronous generator) can have a large impact on the generator output (specifically, the amperes). But, that can only really happen at low loads, not at the loads you are describing. (This is primarily because when the generator voltage drops significantly there are protective relays that will operate to protect the generator by tripping the machine.) So, it's almost impossible for the exciter to be the cause.

Which leaves the prime mover control system--including the control valve(s). We don't know what kind of prime mover your generator is driven by so we can't really comment or offer any specific advice or solutions at this time. Except to say that--based on the information provided--it would appear the problem is related to either the prime mover control system or the valve(s) used to control the energy flow-rate into the generator's prime mover.

Best of luck!