Emergency Diesel Generator in Parallel with Normal System.

When we put our generator with system in parallel, after that we increased the share load on generator up to 246KVA, actual Rated Capacity is 1600KVA. After some time we found high current (1573A) rise on main ACB which is up stream CB for Emergency bus and also in coming ACB for Emergency Bus same time.

But actual load on system was only 530A. (This one is included with bus B which one normal up stream and Emergency Bus C). Its means on Bus B (normal) 300A, and Bus C (Emergency) 230A.

So can anyone explain me why this sudden shoot of current happened on system?

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Abdul... what were the corresponding V, kW, kVAr, and pf, readings?

Regards, Phil

 

Abdul, keep in mind that an emergency generator is not normally intended to be operated in parallel with a grid. Due to this it will have its own fixed settings for governor speed, and terminal voltage and their respective droop settings.

If one attempts to synchronise such gensets to the grid, it the grid frequency/voltage is below the settings of the emergency generator, then the generator will try to adapt output to reach its nominal values.

In you situation it seems that after you synchronised your generator to the grid, either the grid frequency or the grid voltage dropped slightly (we do not know which parameter as you did not specify whether the high generator current was contributing to real or reactive power or both) and so the generator tried to compensate for this. This has nothing to do with your internal loads as these remained the same as you stated. Your generator was actually exporting power to the grid. Mind you if the grid voltage/frequency increased above your generator settings, then the generator would have unloaded (you would have seen a generator load less that you internal load), and in the worst of cases the generator would trip by reverse power.

We do not know whether you have enough instrumentation (namely import/export real/reactive power meters on the incomer from the grid), but if you have, these will easily show what I explained above.

One final question, why are you operating you emergency generator in parallel with the grid? Was there a change in operating philosophy, possibly dictated by financial considerations?