Sangmu Lee

Analysis on the shielding effect by metallic pipe line against electromagnetic induced voltage

The induced voltages are measured to verify whether there is a shielding effect by a metal pipeline like a gas or water provision against electromagnetic induction emitted from power line onto communication line. We installed the first pipeline, 300m, with a telecommunication cable and measured induced voltages. And then we installed again the second pipeline and measured the voltages. There was a around 20% shielding effect by the first pipeline and 30% shielding effect by the second pipeline together against the usual induced voltage, 3V in this experiment case, on the communication cable. We see that there would be a shielding effect by pipeline against electromagnetic induction from this result and could apply into the effectiveness of protection measures.

Characteristics of the Voltages between the Communication Lines and Ground Induced by the Adjacent Artificial High-Voltage or Current ELF Source

The measurements were performed to verify experimentally that the voltage arising on a telecommunication line by a power line is due to the induction phenomena because there has been an opinion that the arising voltage on a telecommunication line is not by induction, but by other causality. The voltage appeared on the telecommunication line by way of an electric field or magnetic field generated by the source apparatus that had been artificially made to provide intentional constant high-voltage or current in ELF, that is, 60 ㎐ as an emulated commercial power.

Transmission characteristic of electromagnetic wave between the ground and the air

When an electromagnetic wave comes into the ground from the air, it drops vertically from an incident point. Vice versa, an electromagnetic wave directs 45° from an incident point when it transmits into the air from the ground. The direction of transmission from the ground to the air has an useful meaning in that a sort of cavity phenomenon occurs in the area of just right over the source in the ground due to its obliqueness. This means that the effect of electromagnetic field decreases in that area. When an interference to another source in the air is analyzed, this phenomenon is worthwhile to be considered.

Transmission characteristic of electromagnetic wave from the earth into the air

This paper presents a basic idea to connect an electromagnetic wave propagation between the air and the earth. When an electromagnetic wave escapes into the air from the earth, its refraction angle rapidly approaches 45° right after a very small incidence degree in the case of ELF wave frequency. As the wave frequency increases, the refraction angle exponentially approaches 90° which means the direction of propagation follows the earth surface. This phenomenon has an useful meaning to lessen an interference from a buried source.

Statistical analysis on screening effects in urban areas against the electromagnetic induction from electrified railway lines

We have performed the field measurement to analyze the screening effects from the electricity feeder in electrified railway to telecommunication line in 30 urban areas and 30 rural areas for 3 years. After measurement we normalized the environmental parameters such as parallel distance, separation distance and soil resistivity in different areas to make a comparative study in same condition. Then we classified the data into 2 groups as an urban data group and a rural data group having 30 measurement places respectively. We analyzed each data group statistically and comparatively using the peak values at the time of passing through the measurement place to guarantee the objectivity and reliability of screening effects in these areas As a result of analysis by applying a statistical method, the comparative ratio of induced voltages between urban area and rural area appear from 0.275 to 0.847 as a probability density function in the 95% confidence interval.

Shielding effect by a metallic pipe against electromagnetic interference with ELF from high speed railway system

An experiment has been practised to demonstrate that a metallic pipe could have a shielding effect to electromagnetic interference by an ELF source generated from a traction system. There are two major variables in this experiment. They are the separate distances between a pipeline and a telecommunication line and also between the terminal grounds of them. It has been seen that the shielding effect increases when the two variables mentioned above decrease. A metallic pipe can have a shielding effect. From this result of experiment, it is assuemd that an urban area might have an environmental shielding effect by many buried facilities like gas/water provisions.

Experimental Verification of Induction Phenomenon on Telecommunication Lines by Applying Its Occurrence Mechanisms Using an Artificial ELF Source Generator

In this paper, an electromagnetic induction on a telecommunication line by the distribution line of a power provision system or a feeder line of an electrified railway system has been verified through experiments. The basic cause of induction occurrence by these practical power provision systems is the returning current through the earth. This principle has been confirmed by the experiments documented in this paper which implemented these mechanisms to incur an induction. Experimental methods were used to produce the returning current through the earth. The experiment to find a relationship between inducing strength and the distance between the two phase lines in a power provision line has also been included to confirm that, when the distance is enlarged, the induction effect increases as the crossnullification effect of magnetic fluxes decreases. An experiment for the existence of a shielding effect by another conduction length material has been addedas a protection measure against the induction.