Psti (Short-Term Flicker Severity) and Plti (Long-Term Flicker Severity) are indices used to measure the impact of voltage fluctuations on lighting systems. These values are crucial for assessing the quality of electrical power, particularly in terms of how these fluctuations may cause visible flicker in lighting, which can be disturbing to humans.
Transposing Pst and Plt values from LV to HV often results in a decrease because higher voltage levels tend to have better regulation and lower impedance. This means that the same level of disturbance at LV will have a reduced impact when measured at HV, leading to lower flicker severity indices.
Impedance is generally higher at lower voltage levels, which can amplify voltage fluctuations and result in higher Psti and Plti values. At higher voltage levels, the impedance is lower, which helps to dampen these fluctuations, thereby reducing the flicker severity indices.
Transposing Pst and Plt values from LV to HV typically involves mathematical models that account for the differences in impedance, load characteristics, and network topology. These models aim to predict how voltage fluctuations at LV would manifest if they were to occur at HV, allowing for more accurate assessment and planning.
Decreased Psti and Plti values at HV indicate better power quality, as there is less flicker and disturbance in the electrical system. This can lead to improved performance of electrical devices, reduced wear and tear, and a more stable supply of electricity. It also helps in complying with regulatory standards for power quality.