Industrial case study of an IEC 61850 standard compatible and synchronised tripping circuit monitor for electric substations

Intelligent Electronic Devices (IEDs) and communication network are core components of modern Substation Automation System (SAS) to implement substation control, protection and monitoring tasks. In recent years, substation communication standard IEC 61850 has been well accepted by transmission and distribution network service providers due to the great benefits of lowered installation, maintenance and engineering costs. In the meantime, there are still a large number of legacy protection relays, which are not capable of establishing the needed communication under the IEC 61850 standard, remain in service in electricity substations. In order to unify the protection and control equipment during substation expansion or network augmentation, the electricity utilities tend to replace the legacy protection relays with numerical IEDs. Such replacement process is likely to reduce the economic value of substation asset because the legacy protection equipment are still reliable and able to meet all protection and control requirements in the substation, especially in substations located in harsh environments. Hence, it is necessary to provide a communication interface to maintain or raise the economic value of the existing substation under expansion or network augmentation. This paper presents a new Tripping Circuit Monitor (TCM) that acts as the communication interface between the legacy and modern systems. The TCM device accurately translates substation event information into a binary data representation using nonintrusive current transducers. The data is then transmitted using Generic Object Oriented Substation Event (GOOSE) message format onto local Ethernet network to communicate with other IEDs for control and protection applications. In addition, the TCM is capable of implementing IEEE 1588-2008 standard to provide a highly synchronised time-stamp value for each translated binary input/output (I/O) data within sub-microsecond accuracy. Test results of this circuit are presented to demonstrate reliability, cost-effectiveness and nonintrusive features of this novel approach.