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Line current differential (LCD) protection is traditionally considered to be highly dependable and secure. However, the increasing penetration of converter interfaced sources (CIS) (e.g. wind, PV, HVDC systems, etc.) could significantly reduce the system fault level and change the fault characteristics, thus presenting challenges to the reliable operation of LCD protection. In this paper, the impact of the integration of CIS on LCD performance is investigated comprehensively. Analytical expressions representing LCD relay operation in the presence of converter-driven fault currents and weak infeed conditions have been developed. A test network, comprising of a CIS model equipped with a typical converter fault-ride through strategy that is compliant with the GB Grid Code, has been built in a Real-Time Digital Simulator (RTDS). Simulations of LCD performance for different fault and system conditions are performed and presented. It is demonstrated that the dependability of the LCD relay can be compromised during internal phase-to-phase faults. The results also show that with the synchronous generation being displaced by CIS, the increasing CIS penetration and fault contribution from the CIS can lead to an increased phase angle difference between the fault currents contributed from the two ends of the protected line, which will increase the risk of the compromised protection performance.

This paper reports on the use of modern packet-based communications technologies to dependably support system-critical services. Such services include current differential protection, secure time distribution, and coordinated wide-area control applications. The challenges and subtleties encountered in the migration to packet networks will be explained, using evidence from extensive validation tests at three laboratories. Based on this experience, the paper therefore will provide a clear, comprehensive, and practical guide to the application of packet technologies and networks for power system applications. In particular, the paper examines integrating legacy protection devices, the impact of long-range communications using microwave transmission, and future applications involving native packet-based devices such as Phasor Measurement Units (PMUs), through a demonstration of fast-acting frequency control.

Railway electricity networks are characterised by different power quality (PQ) phenomena from those of transmission and distribution electricity grids Trains are mobile and continuously interact with overhead contact line and other trains, exchanging power during acceleration, coasting and notably during regenerative braking This producer consumer behaviour of the locomotive with the rest of the system deteriorates the PQ of the railway grid.

The emerging needs and advantages of prioritizing remedial frequency control measures closer to the source of an imbalance event, i.e., to achieve targeted local frequency response, have recently been actively discussed in literature. This paper proposes the use of data driven approach to complement and enhance the robustness of one such decentralized targeted local primary frequency control. The methodology and implementation of the proposed approach is demonstrated by means of a case study on a reduced five area dynamic model of Great Britain power system and its performance verified by means of real-time simulations.

The rising penetration of intermittent energy resources is increasing the need for more diverse electrical energy resources that are able to support ancillary services. Demand side management (DSM) has a significant potential to fulfil this role, but several challenges are still impeding the wide-scale integration of DSM. One of the major challenges is ensuring the performance of the networks that enable communications between control centres and the end DSM resources. This study presents an analysis of all communications networks that typically participate in the activation of DSM, and provides an estimate for the overall latency that these networks incur. The most significant sources of delay from each of the components of the communications network are identified which allows the most critical aspects to be determined. This analysis, therefore, offers a detailed evaluation of the performance of DSM resources in the scope of providing real-time ancillary services. It is shown that, using available communications technologies, DSM can be used to provide primary frequency support services. In some cases, neighbourhood area networks may add significant delay, requiring careful choice of the technologies deployed.

This paper reports on the requirements and performance of the conventional IEEE C37.94 and emerging IEC 61850 protocols for delivering current differential protection over and IP/MPLS network. Several configurations and parameters are investigated, and the paper highlights the key differences.

In the UK, the Capacity to Customers (C2C) project is underway to determine the potential benefits of increased interconnection in distribution systems, combined with demand side response technology. Managed contracts with customers, i.e., the agreement that certain loads are interruptible following system faults, allows distribution circuits to be loaded beyond the limits presently required for security of supply. This potentially permits load growth but avoids the cost and environmental impact of conventional network reinforcement. This paper provides the results of electrical system modelling to quantify the benefits of the C2C operation, using actual circuit data and typical load distributions. Based upon simulations of these circuits, it is shown that increased interconnection generally leads to minor improvements in electrical losses and system voltage. By connecting managed (i.e., interruptible) loads, circuits typically can be loaded significantly further than the present practice in the UK—an average increase of 66% for radial operation and 74% for interconnected systems.