Interference From UHVDC Power Line on Geomagnetic Observation and its Correction

A correction system for geomagnetic observation against interference from the UHVDC power line is developed. The system could offer accurate calculation of interference value and, thus, realize the real-time correction in the Z component observation of the geomagnetic field. Based on the 3-D current magnetic-field calculation model of the dc power line, in which the towers as points and the tower spans as line segments, the calculation equation of the pace current magnetic-field vector projected on the direction of the Z component vector is acquired to calculate the interference value from the power line. Using Microsoft Visual Basic 6.0, the system receives the values of imbalance current on the UHVDC power line and geomagnetic Z component observation through the PC serial port. Consequently the real-time calculation of interference value on the Z component from the power line is realized. Then, the actual geomagnetic observation curve is acquired. During the live debugging period of $\pm$ 800~kV Xiangjiaba—Shanghai UHVDC power line, the high accuracy of the correction system is verified by the joint experiment of the current observation in converter stations and the indoor/infield geomagnetic observation.