DROOP

In an electrical context a simple explanation can be found here : http://en.wikipedia.org/wiki/Voltage_droop

when a generator is put in parallel and synchronised to the other generator which already running at full load,then there is a "speed droop" meaning frequency/load mismatch of the two generators which gives rise to reverse power condition.

Droop in a simple term, is either, generator voltage droop or speed droop. Voltage droop is the drop of no-load rated voltage to full load voltage. For Example, its 480VAC no-load voltage may drop to 470VAC when loaded depending on the droop setting of generator AVR. Speed droop is for the generator speed or frequency. Depending on the setting of governor/speed controller, You may have 61HZ at no-load and drop to 60HZ when loaded. These two droop setting of generator are important in parallel operation of two or more generators. The load sharing capabilities of generators depend on its droop characteristics.

Something that happens after a long session at the pub?

DROOP is defined as the ratio of variation of VOLTAGE (In the Elec. Circuit) from NO-LOAD VOLTAGE to FULL LOAD VOLTAGE i.e.(Vno-load - Vfullload) x 100 /Vno-load %

DROOP is defined as the ratio of variation SPEED (in the Mech.Field - Prime Movers) from NO-LOAD SPEED to FULL LOAD SPEED i.e. (Nnoload - Nfullload) x 100/Nnoload %

BOTH DROOPs i.e. for Electrical - VOLTAGE DROOP as well as Mechanical - Prime Movers,SPPED DROOP IS VERY ESSENTIAL for SYNCHRONISING THE SYSTEM, for PARALLEL OPERATION.

DHAYANANDHAN.S