###### Abstract
R-SV/R-GOOSE messages send monitoring/protection data across a communication network from one IED to several IEDs at once via the use of IP-multicast technologies. Recent studies proposed IP-multicast frameworks and algorithms [3,4] for R-SV/R-GOOSE exchange over a communication network. However, the proposed solutions consider an IP network dedicated to multicast communication. Therefore, utility companies have to make additional investment to implement such a communication network, which is an issue for any business. Experiments with 3G and 4G technologies [5,6] indicate that one cost-effective solution would be to utilize cellular communication in which the existing IP infrastructure can be utilized for data communication in smart grid wide-area applications [7,8]. This will also align with the concept of the smart city which utilizes the Internet to improve quality of life [9]. The ICT infrastructure provides connectivity between smart devices and distributed databases applying for Internet of Things and Artificial Intelligence applications. Cellular Internet has a delay, which may affect the real-time requirements of wide-area applications. Therefore, it is essential to ensure that the communication characteristics satisfy the application requirements. Wide-area applications, particularly wide-area protection solutions for the grid, have special requirements such as extremely high availability and low latency. These make the design of such protection systems non-trivial. However, recent developments in the cellular technology enabled [10,11] these technologies to be applied in mission-critical protection systems as well. Advanced cellular technology can now provide high-performance IP-based communication with low latency for data exchange in wide-area applications. This communication must be secure since a public networking infrastructure is used for the R-SV/R-GOOSE communication, which means that critical data may be exposed to cybersecurity threats. Recent research [10, 11, 12, 13, 14, 15] has already begun to address the use of 5G communication in smart grid applications and analysis delay of IEC61850-based communication. However, previous works did not investigate multicast communication over the Internet accessing by public 5G communication. This paper introduces architectural solutions for this purpose and experiments the proposed architectures for measuring the delay of time-synchronized R-GOOSE messages while cybersecurity solutions are also designed. In [10], the authors investigate 5G communication performance for line-differential protection. In [11], the authors study 5G network for distribution grid protection and fault location applications by focusing on the line-differential, inter-trip protection, and virtual fault passage indication. The authors of [12] discuss 5G technology as an enabler for smart grid applications, and later authors analyze 5G communication for microgrid adaptive protection schemes [13]. While use of 5G is reviewed for various protection applications in [10, 11, 12, 13], the authors did not study 5G communication for Logic Selectivity and Loss-of-Main protection schemes. The authors of [10, 11, 14, 15] analyzed 5G communication delay for time-critical protection and substation automation systems, but they did not measure the delay of multicast R-GOOSE messages communicating over the public Wide Area Network (WAN). Moreover, in [10; 11; 14; 15], authors measured communication delay by using single time sever for time synchronization which necessitates sender and receiver devices to be located in the same place, and in case of [14] even in the same machine. Their time synchronization approach cannot be used for measuring communication delay when the sender and receiver are in two different locations. Furthermore, while authors mentioned about communication security, they did not discuss details of cybersecurity mechanisms that can be applied for securing multicast R-SV/R-GOOSE messages.