Mutual Coupling Compensation Techniques Used for Distance Protection of Parallel Lines

When a distance relay protects a transmission line located on a dual circuit tower, a coupling effect will occur between the two circuits. Transposition of the circuits can reduce the mutual impedances, but this does not cater to the zero-sequence mutual coupling impedance during earth faults. As a result, the impedance measured by a distance relay under phase-to-earth fault conditions in these circumstances will not represent the correct impedance to the fault point unless these effects are taken into account. On multi-circuit lines, primarily if they operate in parallel, a zero-sequence mutual coupling should be considered when calculating settings for distance protection function. A 220 kV parallel line sharing the same tower was analysed using DigSilent Power Factory in the simulations. Phase-to-earth faults in different configurations were analysed on this system, and the reach of the protection relay was then estimated for operation. The results confirm how a protection relay can overreach and underreach in a distance protection scheme due to the influence of mutual coupling.

Research on coupling effects of actuator and round window membrane on reverse stimulation of human cochlea

An active actuator of a middle-ear implant coupled to the round window membrane (RWM), which transmits vibration to the cochlea, has been used to compensate for hearing loss in patients. However, various factors affect the coupling condition between the actuator and the RWM, resulting in coupling leakage. In this study, a coupling impedance model of the human ear and the actuator was used to investigate the effect of inefficient coupling during reverse stimulation. First, the three-port circuit network model of the actuator was coupled with the acoustic impedance model of human ear reverse sound transmission. Meanwhile, the inefficient coupling impedance was estimated. Then, the effect of the actuator’s coupling on reverse stimulation was studied by comparing the reverse pressure transfer function. Furthermore, the inefficient coupling’s influence in the ear with middle-ear disorder was also investigated by simulating two typical forms of middle-ear disorder: otosclerosis and ossicular chain disarticulation. The results show that the change of the inefficient coupling impedance plays a significant role during reverse stimulation. Inefficient coupling of the actuator and the RWM deteriorates the cochlear response of reverse stimulation over the entire frequency range. Additionally, the coupling effect of the actuator does not change the influence tendency of middle-ear disorder on reverse stimulation’s performance, but changes the response amplitude of the reverse stimulation.