2006 IEEE/PES Transmission & Distribution Conference and Exposition: Latin America, 2006
This paper is about the evaluation of a stator roundness of hydrogenerators in some of the EDELCA... more This paper is about the evaluation of a stator roundness of hydrogenerators in some of the EDELCA´s hydroelectric complexes in Venezuela. Large hydrogenerators frequently have several parallel groups on stator windings. These generators also have a neutral unbalance current and a phase unbalance current protection. During the operation of these units, high values of current unbalance between neutrals/groups in parallel per phase were found, reaching alarm and sometimes trip values causing the shut down of operation of the generators. Complete vibration measurements of units were performed and normal values were found; all vibration measurements taken on bearings and static parts had acceptable values. In addition air-gap and displacement of stator bases were measured during operating conditions and it was found that some of the sliding bases that were suppose to slide in the radial direction during heating expansions and contractions were stacked, not allowing the stator to keep its round shape for the operation. Due to magnetic unbalance caused by a non uniform air-gap, the effect on the rotor structure was investigated on a generator of 250 MVA at Macagua Power Plant using the Finite Elements Method. As a conclusion of this study, limits for stator roundness were established to avoid fatigue on rotor spider structure as a consequence of the cycling forces caused on the rotor structure at the rotating speed frequency.
2006 IEEE/PES Transmission & Distribution Conference and Exposition: Latin America, 2006
This paper is about the evaluation of a stator roundness of hydrogenerators in some of the EDELCA... more This paper is about the evaluation of a stator roundness of hydrogenerators in some of the EDELCA´s hydroelectric complexes in Venezuela. Large hydrogenerators frequently have several parallel groups on stator windings. These generators also have a neutral unbalance current and a phase unbalance current protection. During the operation of these units, high values of current unbalance between neutrals/groups in parallel per phase were found, reaching alarm and sometimes trip values causing the shut down of operation of the generators. Complete vibration measurements of units were performed and normal values were found; all vibration measurements taken on bearings and static parts had acceptable values. In addition air-gap and displacement of stator bases were measured during operating conditions and it was found that some of the sliding bases that were suppose to slide in the radial direction during heating expansions and contractions were stacked, not allowing the stator to keep its round shape for the operation. Due to magnetic unbalance caused by a non uniform air-gap, the effect on the rotor structure was investigated on a generator of 250 MVA at Macagua Power Plant using the Finite Elements Method. As a conclusion of this study, limits for stator roundness were established to avoid fatigue on rotor spider structure as a consequence of the cycling forces caused on the rotor structure at the rotating speed frequency.
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Papers by Carlos Azuaje