Electromagnetic Interference (EMI)
Definition: "Degradation of the performance of a piece of equipment, transmission channel, or system caused by an electromagnetic disturbance." (ANSI C63.14, 1992; IEC 60050(161), 1990)
What We Do: Metatech provides analysis services for the various EM disturbances and their effects, including combined effects on systems, subsystems and equipment.
Example: The Forbes Magnetic Storm Data Project
Metatech has been working since 1991 in an ongoing program to study magnetic storm effects on power and communications lines. The objective of the Forbes magnetic storm project was to understand the relationship between geomagnetic field fluctuations and the resulting electric fields which couple to long lines. Metatech supplied the measurement equipment and data analysis, and Minnesota Power provided access to the Forbes facility (a high voltage power substation located in northern Minnesota).
The Forbes facility is unique in that it has two insulated communications lines available that are oriented in approximately N/S and E/W directions and are about 60 km in length. Given the line resistances and the load parameters, we can compute the average electric field over the length of the line from the measured current. The experiment also provided a measurement of the geomagnetically induced current (GIC) on the neutral of a 500-kV power line originating 500 km north of Forbes near Winnipeg, Canada. A 3-axis fluxgate magnetometer was used to measure the geomagnetic field variations at the Forbes facility at a sample rate of 1 sample every 2 seconds.