Extent accuracy class voltage transformers .- Although over time, accurate measurement transformers can be altered, in Capacitive voltage transformers variations occur more frequently in the transformation ratio due to the change in the value of the capacity of the capacitors that form the voltage divider. The determination of error ratio and angle is done by comparing the voltage measurements registered, with another transformer used as a standard.
insulating oil analysis .- insulating oils are essential components of a large number of electrical equipment including transformers and power measurement. Assessing the state of the insulating oil in service is made according to the following rates of control: appearance and color, water content, neutralization index, dielectric loss factor and breakdown voltage, as well as quantity of particles by size are recorded.
Analysis of dissolved gases in oil .- One of the diagnostic methods providing an advance indication of abnormalities in their functional behavior and to determine the measures to be taken before the team suffered major damage is based on gas chromatographic analysis of insulating oil breakdown from overheating of certain points of the transformer or electric shock inside. Depending on the temperature of the hot spot of the discharge energy, the rates at which different gases are produced by decomposition are different. The effect of the thermal or electrical insulating oils lead to the following decomposition gases: hydrogen, methane, ethane, ethylene, acetylene, carbon monoxide and carbon dioxide, oxygen and nitrogen. Determining the content of each gas, the overall assessment and the relationship between the concentrations of different gases and their evolution, one can know not only the existence of a defect, but also the same type and importance. More recently, the above analysis is accompanied with the assessment of the concentration of furfulaldehído derivatives, resulting from thermal degradation of cellulose embedded in solid insulation transformer.
Noise and Vibration Measurements .- These measures are useful for detecting incipient failures in equipment containing moving mechanical parts subject to vibration or friction with fluid, alternating magnetic fields, etc.
electrical insulation measures .- The electrical insulation of HV equipment consisting of oil, porcelain, paper, resins, SF6 gas, etc., Are susceptible to aging over time and conditions of service leading to a progressive loss of their dielectric properties, which requires the control of its evolution. This control is carried out by using the techniques listed here:
- Insulation resistance measurement DC .- Mainly measurement of surface conductivity of the insulation and is used in the detection of imminent failure. Facilitates the decision for immediate intervention, as well as knowledge of the long-term trend of progressive deterioration, the overall estimate of the isolation level actually exists.
- voltage measurement of resorption of oil-paper insulation .- The effect of polarization of a dielectric when subjected to stress and measure the insulation breakdown voltage determined at the previous time load curve polarization spectrum. This test is used to determine the degree of aging of insulating paper impregnated with oil, influenced by moisture content, temperature and absorption of breakdown products.
- dielectric measurement and capacity .- The measure of power factor or loss tangent of the angle in solid and liquid insulators can detect the presence of an effect, although there are layers of insulation in good state in series with the faulty, allowing the measurement to isolate the effect of external insulation. The variation in the ability of an insulation test the existence of conditions abnormalities as the presence of moisture condenser sections shorted or interrupted. Shield ground fault, deformation of windings in power transformers and capacitors deficiencies voltage sharing among others.
- partial discharge measurement .- aging isolates manifested sometimes by the presence of high frequency discharges whose route bypasses, only partially, the insulation between conductors. Contributes to this important addition to the surge, the temperature rise of the computer. The measurement of partial discharge, which has long been an essential part of the qualification tests Electrical and therefore is highly developed in the laboratory, you may incur as errors in adjusting to camp, if not eliminate interfering signals. This technique is used today mainly in the maintenance of transformers, power cables and substations encapsulated SF6. Existing techniques can be classified according to the measured magnitudes and the training unit used, such as measurement of the intensity apparent grounding in the dominant frequency band (featuring inductive sensor for detection), power measurement arc (thermal sensors installed in isolates of SF6) and acoustic detections.
- Measure the excitation current in power transformers .- Measurement of the excitation current at reduced voltage can be used in field to locate certain defects in insulation sheet core structure and magnetic failure of the insulation between turns of the winding and shortcomings of the switching voltage regulator.
- Measure the leakage reactance in power transformers .- The value of the reactance losses often referred to short-circuit impedance testing laboratory, is sensitive to the change of geometry shaped by the flow lines, and field measurement, using low voltage, pede reveal movements and deformations of the windings, open or short circuits between turns.
- response to different frequencies windings .- The transformer winding is formed by a distribution of resistance, inductance and capacitance has a very definite response amplitude and phase, the frequency changes low voltage. Registration and comparison of these responses to different banks often allows detection of variations in the distance between turns and winding deformations.
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