Study of electromagnetic interference on distribution conductors from parallel transmission line and practical mitigation solutions

The transmission line is normally built off-road due to the right of way requirements, while the distribution line is normally built on the road allowance because distribution customers are served from the road allowance. In order to connect remote renewable resources to transmission system in the vicinity, tens of kilometers of high voltage tap line is usually required. To minimize the cost and other issues in land and right of way acquisition, renewable energy developers prefer to use the existing structures jointly and route their HV tap line along the existing right of way. When HV tap line is overbuilt to share the same narrow right of way with distribution lines, it will induce voltages and currents on both phase and neutral conductors of existing distribution lines. Excessive induced voltage and current on distribution neutral and phase conductors may occur during normal operation, fault, and transient conditions of the transmission system. Detailed electromagnetic interference studies shall be conducted to assess the impact of overbuilt or parallel transmission line on the distribution system. This paper will discuss the phenomena of electromagnetic interference generated from HV tap line to the parallel distribution lines. Different practical mitigation solutions will be presented as well.