Challenges in Estimating Amplification of Background Harmonic Voltage Distortion

Modification of existing harmonics is more complex and can occur when new elements are added to the system. This may involve a shunt connection at a busbar or a point-to-point connection between two busbars, such as the introduction of a new cable circuit. For shunt connections, the change in voltage can be estimated using impedance ratios before and after the connection, relying solely on passive network data without requiring knowledge of harmonic sources. For point-to-point connections, utilities often use a similar approach based on the assumption that distortion behaves as a Thevenin equivalent behind system impedance.

However, because both nodes are already part of the network, multiple flow paths can exist, which increases the likelihood of estimation errors.

This paper examines these errors in detail using two network models: the IEEE 39-bus system and a larger transmission system based on real-world data. Random emission sources are introduced to create background distortion at selected points of interest. The analysis compares estimation accuracy for both connection types and provides recommendations on when background amplification methods can be reliably applied.