Hi Kuncoro,

One of easiest way to find the answer of all or any of your question can find from google, try to type "droop mode" then hit the enter it will show you the relevant information pertaining this issue, but of course anybody are most welcome to give you the definition of all of these. what i am trying to say is if you are not in hurry and can wait for some member to give you the definition

kind regards

Roman

You have the definition, so you could have a look at this Woodward paper in order to have a clear understanding of the principles.

http://www.woodward.com/pubs/download.cfm?link=/PDF/IC/26260.PDF

here are some if you need more deatils send your e-mail id

CRM

DEFINITIONS.0 DEFINITIONS

3.1 Speed Governing System.1 Speed Governing System:

A speed governing system consists of a speed governor and fuel metering device which controls the fuel supply to the engine. The speed governing system senses speed and perhaps load, and meters the engine fuel supply such that speed tends to remain constant or to vary with load in a predetermined manner.

3.1.1 Speed Governor. The speed governor includes those elements which are directly responsive to speed and/or load and which position or influence the action of a fuel metering device to maintain the operating speed. When operating in parallel with an independent power source such as the utility company, the governor will act to regulate load.

3.1.2 Fuel Metering Device. A fuel metering device is an element directly or indirectly positioned by the speed governor; e.g., variable displacement pumps, fuel metering pumps, carburetors and other devices that meter fuel into the combustion system.

3.1.3 Speed Changer (Speed Setting Device). A speed changer is an element by means of which the speed governing system can be adjusted to change the speed (frequency) of the generator set under conditions of single unit, isolated load operation, or to change the power output under conditions of parallel operation with an independent power source.

3.2 Overspeed Protection System.2 Overspeed Protection System. An overspeed protection system is a group of devices which sense speed and shut off fuel, ignition or air flow when the speed exceeds maximum speed. It should operate completely independently from the speed governing system. It should require manual reset before the engine can be restarted.

3.3 Rated Speed.3 Rated Speed. Rated speed is the speed of the prime mover output shaft which provides desired generator set frequency.

3.4 Steady State Operating Conditions.4 Steady State Operating Conditions. Steady state operating conditions exist when the engine generator unit is functioning without any influences that are variable; e.g., load changes, BTU of fuel, ambient air temperature or humidity.

3.5 Steady State Speed.5 Steady State Speed. Steady state speed is the mean governed speed when the engine generator unit is functioning with steady state operating conditions.

3.6 Steady State Speed Band.6 Steady State Speed Band. The steady state speed band is the magnitude of the variation in speed, excluding system influence, when the engine generator unit is operating isolated and under steady state conditions with a sustained load. It is expressed as a percentage of rated speed.

NOTE: When the total magnitude of variation in engine generator speed with the speed governing system inoperative is zero, the steady state speed band is a result of the speed governor and is used to determine the stability of the system.

NOTE: When the total magnitude of variation in engine generator speed with the speed governing system inoperative is not zero, the steady state speed band is not wholly produced by the speed governor and, therefore, may not be used in total magnitude to determine the stability of a system.

3.7 Speed Regulation (Droop).7 Speed Regulation (Droop). Speed regulation is the speed change with increase in power output of the prime mover. It is expressed as the percentage change in speed corresponding to the change from zero to full power output.

3.8 Isochronous (Zero Droop) Speed Governing.8 Isochronous (Zero Droop) Speed Governing. Isochronous speed governing is a method of controlling speed in which the steady state speed is independent of load or fuel control position. It may be thought of as a zero droop.

3.9 Stall Torque of the Governor Output.9 Stall Torque of the Governor Output. Stall torque is net torque produced by the speed governor mechanism in the increasing fuel direction to any given output position. Since the fuel control mechanism may be working against a restoring force (such as a spring) in the decreasing fuel direction, the stall torque rating is defined to be the resulting maximum net torque in the increasing fuel direction.

3.10 Work.10 Work. Work is the torque multiplied by the angular travel in radians if the governor output is rotary. It is force multiplied by linear distance traveled if the governor output is linear.

3.11 Parallel Operation.11 Parallel Operation. Parallel operation exists when an engine generator unit is operating with its generator connected to an electric power system in common with generators of other prime mover generator units.

3.12 Isochronous Load Sharing.12 Isochronous Load Sharing. Isochronous load sharing is the ability of two or more governed systems loaded in parallel to share the load proportionally while operating isochronously.

3.13 Speed Transient Response.13 Speed Transient Response. Transient response is a measure of the change in speed of the generator set as a result of sudden changes in load, the magnitude of which should be specified. It is measured in percentage change in generator frequency or speed as the result of specified load changes. A typical specification for a naturally aspirated system might be in the range of 2-6% frequency change as the result of a 100% change in load, depending upon system factors (Ref. Section 5.3).

3.14 Recovery Time.14 Recovery Time. Recovery time is the time required for the engine generator frequency or speed to recover to within the specified steady state speed band as a result of a specified change in load (Ref. Section 5.3).

Droop mode: The generator governor has a slight "droop" in rpm when loaded so it is able to share the load with other generators.

Isochronous mode: The generator has no change in rpm when loaded.A governor that keeps the speed of a prime mover constant at all loads. Also known as astatic governor.

Base loading: The generator supplies power at a continuous output level. The varying part of the load profile is supplied by other sources.

Load sharing: In the case of two generators paralled together they both share the load imposed equally. Whether it goes up or down.

Spinning Reserve: Is a generator that is connected to the grid but is not taking much load as it is on line to take up sudden block loads that occur, or increased demand over normal.

Many good articles on the web about load sharing and droop control that talk about how it operates in "Islanded" or isolated systems as well as grid connected systems.

Try Google and see what pops up.

Electric generators use governor control systems to control frequency. The governor system senses the generator output frequency (shaft speed) and initiates a djustments to the mechanical input power of the generator to increase or decrease the generator's speed as required.A generator governor will not maintain the system's desired frequency (50Hz or 60Hz). Instead the governor resists change and attempts to resist frequency acceralation or frequency decay.

ISOCHRONOUS (FLAT-LINE) GENERATOR RESPONSE

A governor that maintains set frequency (50HZ or 60HZ) for all load levels would be called an 'Isochronous' governor. If the frequency should change even a small amount, the governor would try to adjust generation untill frequency is returned to the set value i.e 50HZ or 60Hz.

In actual practice, an isochronouse govenor characteristic is rare. Isochronous generators tend to be unstable and go into speed oscillations during sudden load changes. They continually make minor corrections in search of their set frequency. In interconnection, this fights with other generators on isochronous control.

Isochronous control is also termed zero-dropping control.

GOVERNOR DROOP

This droop mode is the one used by utility generators. As the system frequency increases, the governor will reduce generator output but will stabilize at a higher frequency than was initially held. When the power frequency decreases, the governor will increase generation but will stabilize at a lower frequency than initially held. Droop settings allow many genrators to operate in parallel and not fighting one another for load changes and is usually expressed as a percentage. E.G a 5% droop setting dose not imply that we normally operate the generator from 58.5 to 61.5 HZ. Droop only describes how much the generator will react when confronted with frequencies different from set values. Droop settings force generators to make load changes that are proportional to their MW capabilities.

DROOP AND SPINNING RESERVE.

A generator's governor may detect a frequency excursion and direct its unit to make a generation change, but the unit can only contribute what it is capable of. If a unit is already at full load (no spinning reserve), it can not contribute more generation to frequency decline. Governors can only adjust unit output if there is room within the unit's capability to do so ( unit with spinning reserve i.e not running at full load). The governor can only move the unit down its droop curve if there is spinning reserve capability available. In addition, generators have limitations how rapidly they can adjust generation levels (called the unit ramp rates). The plant operators must maintain unit pressure and temperatures with in certain limits.

Thats a little bit thourough explanation of governor modes but the others Base load and load sharing are fine with the previours discussers.

Hope this helps