consists of a series of tests to perform on computers to verify their status. The work is preventive in nature, but also includes predictive maintenance, and in some cases a corrective.
Predictive maintenance involved when the team performing the tests, you get to know their current status and can then check the status or anticipate future posibles fallas. El mantenimiento preventivo sistemático se realiza generalmente con línea desenergizada, pero existen algunas técnicas que se pueden aplicar sin necesidad de desenergizar la línea. En la mayoría de las industrias el mantenimiento programado se efectúa en días en los que la producción puede ser interrumpida, pero en el caso del servicio eléctrico, ya que su continuidad no puede ser interrumpida, estos trabajos se programan en días en los que el consumo de energía eléctrica es menor que los demás, lo que ocurre generalmente los fines de semana. También existen disposiciones de subestaciones que permiten que algunos equipos puedan ser desenergizados para trabajos de mantenimiento, sin que esto implique the power outage, but still require coordination with those responsible for operation. Predictive maintenance techniques applied in substations, based on recommendations of international standards (IEC-76, IEC-72), are detailed below.
thermographic inspection .- Used by the use of infrared thermo-vision cameras to locate defects by heating, particularly in parts of contact switches, terminals and clamps for connecting the equipment, with reference to the ambient temperature and other healthy phase. It is implemented by a sweep of all electrical connections in a park and can record the temperature distribution in a
equipment housed in normal conditions of service arrangements.
voltage measurement step and touch .- The electrical installations are produced circumstantial, earth fault currents generated by potential elevations of the land, which can become dangerous for people who work there . To ensure that these potentials are not dangerous, the rules define the maximum allowable voltage and method of measurement of step and touch voltage, injection of current in the grounding network. It also establishes the need to measure tensions that can be transferred out of the substation and the determination of the diffusion resistance of a substation grounding, newly built or in operation, to verify its condition over time.
contact resistance measurement .- The electrical characteristics of a contact, switching elements, depend on the number of interruptions and the cumulative arc energy, and that cause the wear of its components, pressure loss contact and the presence of impurities in particular insulation film deposited on the surface. Also, the stresses produced during the failure, action wind and vibration during the maneuvers, worsen the mechanical properties of the connection points of equipment. The control of the value of electrical resistance at the junctions of conductors forming an electrical circuit, to determine the maximum intensity that can flow through them, without exceeding the limits allowed heating for each type of material making up the union .
- dynamic resistance switches .- Due to the design of the contacts in some switches, which have main contacts and arc, is used during the performance of the displacement curve of the same, to continuously record the voltage drop in the cutting chamber at the beginning and end of the opening and closing.
- dynamic resistance of load tap changers .- An important part of the failures in power transformers caused by the aging of the contacts of the load tap changer (CTC). State inspection of the contacts of the selector is laborious because of its location. It is applying a new method to diagnose the state of the sliding contacts during the switching process by preventing the disassembly for inspection, based on obtaining the oscillogram corresponding to the change in intensity due to the influence of the value of resistance occurring during each feeding switching voltage regulation (resistance switching contact and the corresponding winding.)
winding resistance measurement .- The electrical resistance of the winding of the transformer windings is altered by the existence of short circuits between windings, thermal defects in their isolation by deficiencies in the contacts of the regulator in charge of the transformer. The control of the value of this resistance facilitates the maintenance decision making, especially in interventions for failure. Measures
operating times .- One of the main measures performed in the maintenance of electrical control switches or pneumatic and especially switches, is to control own time required in performing closing and opening. The control of these values \u200b\u200ballows the necessary adjustments to ensure proper operation of equipment and allows you to schedule the review necessary to adequately replace parts and components.
- Sync switch between cameras .- The measurement of time to maneuver in each of the chambers of the switch allows to know the level achieved by the contacts sync, both linearly (between cutting chambers of each phase ) and transverse (entre fases) facilitando una información complementaria del balance de energías en la maniobra.
- Tiempo de reposición de energía del mando de accionamiento del interruptor.- En interruptores con mando a resortes se mide el tiempo de carga de resortes para poder asegurar que las maniobras son realizadas en condiciones óptimas. En mandos neumáticos es necesario verificar la actuación de los presostatos. Cuando los tiempos obtenidos difieran o presenten desviaciones significativas con respecto a los valores de referencia, se procederá a la revisión de los sistemas de carga: motores, compresores, conducciones, conexiones eléctricas, tensión, etc.
- graphic analysis of displacement of contacts in switches .- The diagnostic method used to determine the mechanical condition of a switch is based on obtaining graphical displacement curves of main contacts during maneuvers closing, opening and closing on missing. Graphic analysis conducted in the facility and whose interpretation is amply supported by the use of remote diagnostic, we obtain the following parameters:
- Total stroke (traveling) .- Value defined by the difference from the initial position before the start of the maneuver, until the final position at the end of the maneuver.
- contacts .- Penetration distance in the opening of the main contact between the closed position and the electrical isolation of contacts.
- opening and closing speed .- intervals are measured in the displacement graph indicated by the manufacturer: arc zone in the opening and the closing prearco.
- Damping, overtravel and bounce .- The discussed in the relevant areas of the chart, looked at whether the damping is correct and there is no sobrerrecorridos, ni rebotes en número y amplitud excesivos.
Gráficos de consumo de bobinas y motores.- El control del consumo en las bobinas de apertura contribuye al conocimiento del estado de los sistemas eléctricos y mecánicos del interruptor, obteniéndose normalmente del registro gráfico de la intensidad realizado simultáneamente con el registro de desplazamiento de contactos, tiempos de maniobra, y tensión de alimentación en bornas del armario de mando. El registro del consumo del motor facilita una información complementaria a la del tiempo de reposición de energía del mando en interruptores y sirve
igualmente para controlar el comportamiento del disconnectors control during maneuvers. Measure
pollution deposited on insulators .- These measures seek to determine when the contamination deposited on the insulator can reach a dangerous value, taking into account not only the type of pollutant, but the atmospheric and geographical substation. To do this, you can take successive samples of deposited pollution and predict their evolution, which is not always easy, or measuring the number and extent of surface discharges by appropriate equipment, which information is processed and continuously recorded by PC .
Measure leakage current arrester .- ZnO arresters are subjected during service to the influence of different voltage, switching both temporal and atmospheric aging components and can cause it to malfunction. Evaluation of ZnO arresters can be made from the measurement and control of the resistive component of leakage current through them permanently during normal service.
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