Modelling the IEC 61850 and DNP3 Protocol Using OPNET in an Electrical Substation Communication Network

Communication protocols are a composite of supervisory control and data acquisition (SCADA) and they are used by the devices connected on the SCADA network. In this paper the distributed network protocol (DNP3) and International Electrotechnical Commission IEC 61850 communication protocols were modelled in OPNET. The simulation of DNP3 and IEC 61850 communication protocol is done in different scenarios and the traffic behavior is analyzed. The DNP3 protocol is modelled as the medium protocol of communication during the maintenance of a 400kV Transformer at an Electrical Substation. Its network traffic behavior is then analyzed for this operation. The IEC 61850 protocol is then used as a medium of communication in the same Electrical Substation communication network (SCN) when a faulty backbone switch is present. In this scenario the network traffic behavior is again analyzed. The DNP3 simulation during the maintenance of the 400 kV Transformer shows that the model is working since the throughput is consistent without dropped packets at the Substation RTU end and the 400kV Transformer IED end. The IEC 61850 simulation when a faulty backbone switch is present shows that the model is working in this scenario since the throughput is again consistent. When the IEC 61850 protocol is modelled on the SCN, the time delay is 80 μs during normal operation and with a faulty switch the delay is 100 μs for this protocol. This shows that for the IEC 61850 model the time delay increases when there is a faulty backbone switch but not exceedingly since there is a backup switch in the structure. In the DNP3 model during the maintenance of the 400kV Transformer the time delay is approximately 160 μs. The IEC 61850 protocol performs approximately twice as fast as the DNP3 protocol during normal operation in an SCN.

I. Introduction

Supervisory Control and data acquisition (SCADA) involves the control and observation of the running equipment to perform the functions of parameter adjustment, measurement, data acquisition and equipment control [1] . SCADA system is used at an Electrical Substation to monitor alarms, analogue messages such as voltage levels and to open and close breakers remotely. This paper analyzes the traffic characteristics in different operational scenarios when two communication protocols commonly used in SCADA systems namely IEC 61850 and DNP3 are applied over an Electrical Substation grid. DNP3 is an open source protocol used in the SCADA System [2] .