Modeling power transformers for the design of SWER line coupling networks

Abstract

Many countries use Single Wire Earth Return Power (SWER) lines for providing power to customers in rural areas. These SWER lines can be up to 300 km long. For Smart Grid applications and power quality assurance on SWER lines, a communication system is required. Power Line Communications (PLC) signals in the 9 to 95 kHz CENELEC-A frequency band are the most economical means for providing this communication on SWER lines. To inject the PLC signals on the typical 19.1 kV SWER line, a low cost coupler is required. The behavior of SWER line power transformers at PLC frequencies is critical for the design of this coupling network. This paper describes the development of a wide frequency band model for SWER line power transformers and uses this model for the design of coupler networks. A novel technique is used to match the transformer model to measurements. This model matching technique and the resulting transformer model are also applicable to other power transformers.