Advantages of Paralleling Transformers at Industrial Sites with a Communication-based Paralleling Method

To address the increase in load at industrial facilities, an additional transformer can be added and paralleled with the existing transformer. When the transformers are equipped with On-load Tap Changers (OLTC), the loads should be balanced between the paralleled transformers to avoid circulating current and resulting heating due to overloading of one of the transformers. Classic circulating current and circulating reactive current paralleling methods have been used successfully for many years at industrial sites and electric power utilities. The circulating current and circulating reactive current methods of paralleling use paralleling balancing current transformers and their associated current loops with complex wiring from many breaker status contacts between the paralleled transformers. This additional paralleling equipment and most of the wiring between the transformers and breakers required by the circulating current and delta VAr methods can be eliminated with a communication-based Peer-to-Peer paralleling method. This paper describes the basic concepts of paralleling transformers and provides a detailed description of the communication-based paralleling scheme. This method consists of using a high-speed Peer-to-Peer communication link to implement a paralleling scheme for two or more transformers. The information passed between the transformer controls is communicated via Ethernet-based IEC 61850 Generic Object Oriented Substation Event (GOOSE) messaging protocol. This paper will discuss the advantages of using the communication-based paralleling scheme.