H4-KH-27-D uxiliary coolingType Speed of the high speed shaft Helical speed reducers H4

Flender/Flender Gear Units/Helical speed reducers H4

ion, Power Engineers performed very thorough analysis of the settings applied for the MGS relay protection scheme. As part of this study, the settings were again reviewed for accuracy and they were also compared to the settings in the field. 4.1 Single Line with Protection for MGS #1 and #2 For the following discussion please refer to drawing -M4A -0-0. 4.2 Overexcitation (Volts/Hz ) Protection - 2 Overexcitation occurs when the flux density in the machine exceeds its rating. Overexcitation can lead to severe overheating of transformers and generators causing damage and eventual insulation breakdown. Overexcitation protection is not provided by the Alstom ABB Combiflex protective relay package, howev er, /HZ limiter is included as part of the excitation package. The SEL -3G relay incorporate this function and is set as follows: Stage 1: 1% with 6 seconds delay. Stage 2: 1% with 6 seconds delay. The above settings are consistent with the IEE C3.1- 2 guidelines. 4.3 Reverse Power - 3 Reverse Power, or anti -motoring protection is provided to protect the prime mover against damage. When the prime mover loses power (.. steam flow) and the generator is still connected to the grid, the generator will act as motor, driving the prime move . This condition can cause severe damage to the prime mover quite rapidly. Reverse Power protection is provided by the Alstom ABB Combiflex protective relay package as well as the SEL -3G protective relay. Reverse Power setting is 4 kW for 1 seconds . These settings are based on the manufacturers recommendations. The above settings are consistent with the IEEE C3.1 -2 guidelines. 4.4 Loss of Excitation - 4 Loss of Excitation occurs when the field supplied to the generator rotor is removed, bu the generator continues to run. In this case, the synchronous generator will act as an induction generator. During these conditions, the generator stator winding can overheat causing severe damage to