Campos Magneticos En Cables

EMPALMES CRUZADOS EN EQUIPOS BES
Presentador: Jaime Valbuena Baker Hughes Technical Support

OBJETIVO
Explicación básica de los campos magnéticos en conductores. Efectos de campos magnéticos en cables planos trifásicos para equipos BES de 1 solo conductor. Solución para evitar des-balances de corriente en cables planos trifásicos de 1 solo conductor en equipos de bombeo electrosumergible,(BES).

10.2.4 Balancing Flat Cable Phase Currents. API P1018sv1 61899
Flat electric-motor cable has unbalanced series impedance, which causes current unbalance in electric submersible pump (ESP) motors. When flat cable is required, current unbalance can be minimized by rotating the cable connections to find the combination that produces the least unbalance. However, it should be noted thatcurrents entering the cable at the surface are not necessarily the same as the currents entering the submerged motor. High and unequal shunt admittance can produce a zerosequence current, causing a downhole current unbalance that is not reflected at the surface. Groundedneutral wye-connected power transformers will create that condition. Common practice tries to maximize run life by using anungrounded power source. Two faults must then occur before operation ceases. The ungrounded power source prevents flow of zero sequence current, thereby minimizing unbalance problems. Even if the transformer neutral is not grounded, having one phase grounded downhole will also allow some zero sequence current. Therefore, before rotating phases to balance currents, it is necessary to ensure that no phaseconductor is grounded. Since the motor is connected to the end of the cable, it is not possible to measure individual phase insulation resistance directly. The motor effectively shorts the three-phase conductors together. All three-phases will have essentially the same resistance to ground readings. On ungrounded secondary systems, the quality of each phase-insulation system can be determined bymeasuring individual phase-to-ground voltages. If each voltage reading is within 10% of the overall average, then rotating the phases to achieve minimum current unbalance can be beneficial. The three possible cable-to-motor-starter connections can be compared for minimum current unbalance. All three conductors must be rotated in sequence to avoid reversing the direction of motor rotation. Theunbalanced series impedance of the cable can then be optimally connected to offset unbalances in input voltage and produce minimum unbalance in motor currents

PROBLEMA PLANTEADO
Desbalances de corriente. Limitaciones para incrementar frecuencia. Perdidas de producción. Perdidas económicas.

Efecto Magnético
Toda corriente eléctrica produce un campo magnético. Cuanto mayor sea la intensidad de lacorriente eléctrica que recorre un conductor mas elevado será el campo magnético que genere. Cuando una corriente viaja por un conductor (cable), genera a su alrededor un efecto no visible llamado campo Electromagnético

Intensidad del campo magnético
β= µ* I* 2¶ * d

Regla de la mano derecha para campo Magnético ( β )
Aplicación de la regla de la mano derecha, los dedos alrededor delconductor indican el sentido del campo magnético y el dedo índice el sentido de la corriente

Fuerza Magnética (Fm)
Andre-Marie Ampere noto que: La fuerza entre dos largas corrientes rectas y paralelas era inversamente proporcional a la distancia entre ellas y proporcional a la intensidad de la corriente que pasaba por cada una. Fm = I * β * L * sen φ

Fuerza Magnética entre dos conductoresUna forma fácil de ver el efecto para los que no demandan matemáticas: (esta no es la fórmula básica). Dadas dos cortas corrientes paralelas I1 e I2, fluyendo en segmentos de hilo de longitudes L1 y L2 y separados por una distancia R, la fórmula básica nos proporciona la fuerza entre ellas como proporcional a:

I1 I2 L1L1/R2

Fuerza Magnética entre dos conductores
La experimentación con...