Pau Casals Torrens

The influence of the self-excited induction machine into the electrical grid under instability situation - Real case measurement

The three phase induction machine is used in the mainly part of the industry and it requires reactive power from the grid to start and function. The reactive power consumption is economically fined so the industries install capacitors in parallel with the motors and loads. The bank capacitor, gives this reactive power to the machine in order to improve the cos f factor in the installation. When a fault appears in the grid, this machine gives the active power to the fault, but when the overcurrent relay sets the fault, the induction machine is already with inertia with electromagnetic and mechanic specific parameters that originate a non-controlled islanding mode and it provides the power to the loads on this feeder. Even though several works are published within the islanding detection, the islanding operation about the induction machine as a generator in power wind energy applications, nevertheless in the following we show the motor perspective. The stability of the system in the time period between the relay opening and the fast reconnection is out of control, so a complete study a about the electric magnitudes, voltage and reactive power , active power and frequency and the angle stability is needed. In this paper we show a real case that appears in a distribution Medium Voltage (MV) radial network in Spain in a 25 kV feeder and we summarize the voltage /current wave form and the frequency oscillation.

Comparative analysis of cold ironing rules

The current paper pretends to offer a global vision about the actual situation of the regulations and requirements applied to High Voltage Shore Connection (HVSC) systems, also known as cold ironing. To develop the entire study, the following Classification Societies rules have been consulted: ABS High Voltage Shore Connections; BVHigh-Voltage Shore Connection System; DNV-Electrical Shore Connections; DNV-GLRules for classification of ships; LLOYD’S REGISTER-Rules and regulations for the classification of ships and RINA-Rules for the classification of ships. In the way to accomplish the proposed objective, the mentioned rules have been compared including all the specific aspects and regulations related with “the shore side” of the entire installation. These requirements are also compared with the international standard ISO/IEC/IEEE 80005-1 High Voltage Shore Connection Systems and show the grade of accuracy provided by each Classification Society against that standard. Finally, the results of the comparison show that many of the studied rules focus their rules just on the ship side of the installation or just provide some general recommendations for the shore side. According to that, the shore side is considered such as not part of the ship and consequently is not considered in their rules.

Online detection of partial discharges in medium and high voltage cable accessories by acoustic emissions

The acoustic waves caused by partial discharges inside a dielectric can be detected by sensors of acoustic emissions (EA) and analyzed in the time domain. The experimental results that are presented, demonstrate the capability of online detection of these sensors, in the vicinity of a cable, splice or terminal accessory. The EA sensors are immune to electromagnetic interference, are a non-destructive detection method and guarantee galvanic decoupling from the voltage network; This technique of detection of partial discharges can be applied as a test method for preventive or predictive maintenance (maintenance based on the condition), in equipment or installations of medium and high voltage in service and represents an alternative to electrical detection systems, conventional or not, which continue to be based on the detection of current pulses.

IDENTIFICACIÓN DE DEFECTOS EN CABLES DE MEDIA TENSIÓN APLICANDO MÉTODOS MULTIVARIABLES

Las descargas parciales en cables de media y alta tension tienden a degradar el aislamiento, provocando danos irreparables a medio y largo plazo, por lo que su pronta deteccion y localizacion es especialmente interesante. Este articulo hace la diagnosis e identificacion de cables de media tension tipo XLPE mediante la adquisicion de pulsos de descargas parciales. Para ello se utiliza un detector estandar de descargas parciales. A continuacion los datos adquiridos se procesan via transformada rapida de Fourier y mediante la aplicacion de metodos multivaribles de extraccion de caracteristicas, es decir analisis de componentes principales (ACP) y analisis de variables canonicas (AVC). Posteriormente se aplica el clasificador k vecinos mas cercanos (kVC). Los datos experimentales aportados evidencian que el sistema propuesto de identificacion es sencillo, preciso y requiere de muy poco tiempo para clasificar una muestra desconocida.