PP58 Rev B

Page 1 of 3 COPYRIGHT, 2009 GE PACKAGED POWER, L.P., ALL RIGHTS RESERVED. THIS DRAWING IS THE PROPRIETARY AND/OR CONFIDENTIAL PROPERTY OF GE

PACKAGED POWER, L.P., AND IS LOANED IN STRICT CONFIDENCE WITH THE UNDERSTANDING THAT IT WILL NOT BE REPRODUCED NOR USED FOR ANY PURPOSE

EXCEPT THAT FOR WHICH IT IS LOANED. IT SHALL BE IMMEDIATELY RETURNED ON DEMAND, AND IS SUBJECT TO ALL OTHER TERMS AND CONDITIONS OF ANY WRITTEN AGREEMENT OR PURCHASE ORDER WHICH INCORPORATES OR RELATES TO THIS DRAWING.

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LM6000 PG Full Load Rejection Guidelines

Introduction

The LM6000PG gas turbine unit is capable and designed to accommodate partial and full load rejections and stay on line without trip; however, GE does not encourage for load rejection tests be performed on the gas turbine unit. Even though the gas turbine drive train and controls are designed robust to handle full load rejections, the results cannot be guaranteed due to many variables that are outside of GE AEP’s control. These variables include fuel/water supply and treatment systems, generator switchgear, plant auxiliary power connections / reliability, utility main electrical feeder / GSU interface, plant control systems, and air inlet filter DP’s. GE Aero can offer a detailed description of load rejections, and guidelines to consider when load rejection tests are used to test control system dynamics. Description

The LM6000 PG engine is a (2) shaft design, which is air coupled from the HP to LP rotor. The LP rotor is connected to the electric generator via mechanical gearbox. Gas turbine engine running speed from the LP is 3930 at synchronous idle and the mechanical gearbox reduces speed to 3000/3600 (Ratio 1.309/1.0847) for 50/60 Hz respectively. The LP rotor overspeed set point on the engine have been configured for optimum to allow the LM6000 engine / generator train to overshoot in speed and at the same time maintain mechanical protection. These set points allow for the engine and generator coupled components to overshoot in speed, but stay below the shutdown level. The overspeed set point on the LP rotor drive is 4650 RPM and has been designed to maintain the GT on line and not trip during full load rejection. This LP overspeed set point also ensures that the generator speed stays below its maximum running speed of 4320 RPM for 50 and 60 Hz applications via the mechanical coupled gearbox. Other special features are incorporated into the controls to accommodate load rejections. Two of these features are:

1. The water injection control system has an embedded sequence to ensure the engine does not flameout during a load transient. When the generator circuit breaker opens, the controls rapidly ramp the water flow to a minimum rate (300 pph/s), closes the water supply valve nearest to the engine, then opens the manifold drain valve open for (2) seconds, then re-closes the drain valve. This

GE Energy Aero Energy Division

Position Paper #58

Rev B

October 13, 2009

16415 Jacintoport Blvd

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PP58 Rev B

Page 2 of 3 COPYRIGHT, 2009 GE PACKAGED POWER, L.P., ALL RIGHTS RESERVED. THIS DRAWING IS THE PROPRIETARY AND/OR CONFIDENTIAL PROPERTY OF GE

PACKAGED POWER, L.P., AND IS LOANED IN STRICT CONFIDENCE WITH THE UNDERSTANDING THAT IT WILL NOT BE REPRODUCED NOR USED FOR ANY PURPOSE

EXCEPT THAT FOR WHICH IT IS LOANED. IT SHALL BE IMMEDIATELY RETURNED ON DEMAND, AND IS SUBJECT TO ALL OTHER TERMS AND CONDITIONS OF ANY WRITTEN AGREEMENT OR PURCHASE ORDER WHICH INCORPORATES OR RELATES TO THIS DRAWING.

feature will remove entrapped volume of water in the manifold, thus prevent quenching of flame in the engine combustor during engine transients.

2. The generator protection system 81O device (over-frequency protection) has a

recommended set point of 62 Hz @ 5 seconds which only initiates an alarm, therefore does not trip the generator breaker open or initiate a shutdown. This allows the generator to overshoot in speed successfully within the allowable limits, and still maintain plant auxiliary load bus connectivity.

The actual amount of overshoot in speed that occurs during load transients are determined from the magnitude of load rejection, inertia of drive train and base load that is present on the bus from result of plant auxiliary systems. Typically, plant auxiliary loads remain connected to the gas turbine generator set bus when the utility breaker opens. These plant auxiliary loads help reduce the gas turbine speed overshoot as they apply a negative force to the total overshoot applied to the engine train, thereby reducing the total amount of overshoot as opposed to having zero plant auxiliary load during the event. Expected transient speed results from full load rejection are shown in Figure 1 for both 50 and 60 Hz applications.

Conclusion

Performing load rejection tests on the LM products are not recommended. If it is determined that a load rejection test is required then it’s recommended that partial load rejections on the gas turbine unit are performed starting at 5 MW, then increased in 5 MW steps until the desired load magnitude has been accomplished. This will test and prove plant dynamics are sufficient to handle smaller upsets first before moving to higher magnitudes. Repeated attempts of load rejection tests should be held to a minimum. In no way does GE Aero encourage that load rejection tests should be attempted, but through the guidelines called out in this paper adequate direction can be determined when and if the need arrives.

PP58 Rev B

Page 3 of 3

COPYRIGHT, 2009 GE PACKAGED POWER, L.P., ALL RIGHTS RESERVED. THIS DRAWING IS THE PROPRIETARY AND/OR CONFIDENTIAL PROPERTY OF GE PACKAGED POWER, L.P., AND IS LOANED IN STRICT CONFIDENCE WITH

THE UNDERSTANDING THAT IT WILL NOT BE REPRODUCED NOR USED FOR ANY PURPOSE EXCEPT THAT FOR WHICH IT IS LOANED. IT SHALL BE IMMEDIATELY RETURNED ON DEMAND, AND IS SUBJECT TO ALL OTHER TERMS AND CONDITIONS OF ANY WRITTEN AGREEMENT OR PURCHASE ORDER WHICH INCORPORATES OR RELATES TO THIS DRAWING.

Figure 1 - LM6000 PG LP Rotor 50/60 Hz Estimated Full Load Rejection