Increasing shares of renewable energy sources in power systems worldwide have led to increased renewable curtailment due to network and/or stability limitations. Energy storage systems, both stationary and mobile, are widely proposed as a promising solution for reducing such curtailment. The paper presents a detailed analysis of renewable energy curtailment, taking the case study of a future Irish grid scenario, to identify the prospects of transportable energy storage systems (TESS). A combined unit commitment optimal power flow formulation has been developed to evaluate the locational curtailment from all renewable sources. The study establishes a baseline understanding of the locations and durations of renewable curtailment, providing insights on short-term/long-term TESS relocation, along with short/long distance movement possibilities, paving the way for optimal sizing and management of TESS units.

Dynamic line rating (DLR) systems are recognized as a cost-effective and socially accepted asset for relieving network congestion and uprating existing transmission systems, based upon accessing additional weather-dependent capacity of overhead lines. Although direct and indirect DLR methods are available, utilization of indirect weather-based approaches, that is, sensors are not installed on the conductor, are of increasing interest due to fast installation times, that is, no requirement for line outages and lower capital costs, with achievable potential for wide-area implementation. An extensive review is presented on the components and requirements of such systems, including weather stations, forecasting models, downscaling and DLR calculations, overhead line and conductor thermal models, and communication platforms. In addition, the features of practical instances of these systems are briefly reviewed. Moreover, a systematic approach is introduced for statistical evaluation of the high-level DLR potential across an entire region, as well as an assessment of the line-level DLR ampacities within an electrical grid, based on (weather forecasting) reanalysis data. The proposed methodology can disclose available additional capacity as part of early-stage planning for wide-area DLR systems. The island of Ireland and the 110 kV network of the Republic of Ireland (ROI) power system are considered as the study cases, with comparison made against seasonal static ratings and ambient temperature adjusted line rating methods.This article is categorized under:Energy and Power Systems > Energy InfrastructureClimate and Environment > Net Zero Planning and Decarbonization

Wind farms installed at wind-rich regions often located in remote areas increase overloads in the weak adjacent transmission network. As a result of this congestion, extra transmission capacity is required to avoid wind energy or load curtailment that can be achieved by applying some modifications. New line construction and line uprating have been recognised as conventional solutions for the transmission capacity increase. Meanwhile, in the last decade, these solutions have brought several serious issues for the network operators, forcing them to evaluate and install different types of assets based on state-of-the-art technology in order to harvest the existing lines at the maximum possible level. An investment model is developed to relieve the congestion, including dynamic line rating (DLR), distributed static series compensation and energy storage systems (ESS), with a simplified unit commitment implementation. The resulting mixed-integer linear model is then solved with the classic Benders decomposition. Installations of DLR and distributed static series compensator (DSSC) on the same line are formulated, with techno-economic analysis performed for different asset combinations on the IEEE RTS 24 bus system, for high wind energy share scenarios. Wind curtailment levels are studied for different DLR/DSSC approaches, including the impact of practical implementation requirements. Based upon additional interlinking constraints, the robustness of investment decisions for independent DLR and DSSC investments is compared against approaches where DLR and DSSC investments are permitted on the same line. The investment based on sequential incorporation of the unit commitment in the study is also investigated to reflect the importance of the integration of the unit scheduling in the model for high renewable systems.

In order to maintain system security levels against a backdrop of generation and demand growth, network planners may require grid expansion and/or line modification measures. Traditionally, this has been achieved by uprating existing lines and constructing new lines. However, technical, environmental, cost and timeliness concerns can encourage the adoption of dynamic line rating (DLR) systems, as part of enhancing the utilisation of the existing network. Hence, a novel approach is presented here for planning reconductoring and DLR systems, relating to the implementation of security constraints. A multi-year stochastic mixed integer linear model for line N-1 short time security is developed, incorporating a unit commitment stage, which is later solved using Benders decomposition. An additional pre-optimisation stage, which can be efficiently parallelised, is introduced to largely support the burden of incorporating the security constraints. In addition, staged investments for individual lines, including applying DLR before later reconductoring, is investigated. The effectiveness of the proposed approach is shown for the IEEE RTS 24 bus system.

Increasing wind energy utilisation, along with demand growth, are impacting on transmission system regional loading. Traditionally, uprating of existing lines and construction of new lines would have been common approaches to increase network capacity and reduce congestion. However, environmental, social, and technical challenges are encouraging network operators to apply measures which improve utilisation of the existing network, as part of future planning. Here, a mixed integer linear programming model is developed to integrate various alternative options, including dynamic line rating, energy storage systems and distributed static series compensation, into the network planning process. Using a multi-stage approach, co-optimised planning of these assets is studied and compared against a conventional reconductoring approach. The benefits of co-optimisation are shown for the IEEE RTS 24 bus system, with high wind contributions in selected regions.

Prospective short circuit level for MV switchgears of an industrial network is supposed to increase in time, due to inevitable expansion of utility network, probable installation of local generators and increasing the production capacities resulting in more motor contribution. If this short circuit current exceeds the level for which the switchgear was designed, the plant owner shall take some measures to prevent from possible damage. To solve the problem without replacing existing equipment, current limiting protectors have been utilized. These devices could reduce prospective short circuit current coming from upstream and could be an economical solution to this problem. Meanwhile, as these devices are triggered by instantaneous current, events especially relating to sudden increase in current may cause them to operate. This `False Tripping' is troublesome since these devices usually install on main incoming feeders of the network. This paper investigates the issue for a project aiming the reduction of short-circuit level from motor dynamics perspective including contribution to upstream fault and response to voltage dip using PSCAD/EMTDC software.

Vacuum interrupters have been recognized as one of the most important sources of switching over-voltages in MV networks, leading to voltage escalation. These over-voltages are usually observed as a result of inductive current interruption which may accompany with multiple re-ignitions. Single phase fault current in high inductance-earthed networks is inherently inductive and therefore prone to cause dangerous over-voltages during interruption. To mitigate this problem, a resistor is usually inserted between ground and inductor neutral. In this paper, sizing of this resistor is investigated for an industrial plant. Also, prominent conditions affected by resistance value, leading to re-ignitions are studied. Firstly, resistor is sized through relevant IEEE recommendation. Then vacuum circuit breaker is efficiently modeled and using a new simulation-based method in PSCAD/EMTDC platform, the maximum over voltage figures are obtained for variety of operating points. Finally, simulation results are compared with those given by IEEE criterion and appropriate value for neutral resistance will be effectively determined. (C) 2014 Elsevier Ltd. All rights reserved.

When a fault occurs in high voltage (HV) and Extra High Voltage (EHV) lines, they could automatically be re-entered to the circuit by auto-reclosing operation of transmission switches after passing a certain time from the first tripping operation. It is due to the fact that most of the faults occurred in HV/EHV transmission systems have a corresponding arc which could be removed just after de-energizing the line. To ensure successful reclosing, de-energizing interval addressed as dead time is conventionally determined, based on the calculation of the time needed for quenching subsequent weakened secondary arc. However, on-fault reclosing is probable even if dead time is conservatively selected. It can lead to severe power swings and put the system in danger of instability especially in vastly loaded networks. These swings will be intensified or weakened upon rotor angular speeds of dominant generators in reclosing instant, which is the key factor in acceleration or deceleration of power swing. Therefore power oscillation can be mitigated by adaptive selection of dead time. In this paper, a new method for dead time calculation is proposed in order to mitigate power oscillations effectively. The proposed method can also be implemented in on-line monitoring and control algorithms due to low amount of calculation. In this approach, single machine infinite bus equivalent (SIME) method is used for the evaluation of power oscillations.

The high voltage (HV) and Extra High Voltage (EHV) lines could be reestablished by auto-reclosing operation of transmission switches automatically after a certain time from the first tripping during fault. Successful reclosing is carried out considering a dead time which is usually chosen based on the quenching time of possible secondary arc. However, this is not enough to guarantee the transient and dynamic stability of the system. The reclosing instant is the key factor in acceleration or deceleration of power oscillations, and should be determined carefully to ensure the stability of the system. Power oscillations can be mitigated by adaptive selection of the dead time. In this paper, a new method for dead time calculation is proposed in order to mitigate power oscillations effectively. The proposed method is also capable of utilizing in on-line identification because of low amount of calculation required. In this algorithm, single machine infinite bus equivalent (SIME) method is used for evaluation of power oscillations.

System protection performance and transient stability of the electrical network are significantly affected by each other. The larger the time delay in which protection detects and clears the fault, the more likely loss of synchronism will be, especially in the networks with internal generation. Over current protection schemes inherently operates with considerable delay. Moreover, system dynamic oscillations discernibly aggravate their performance. Therefore utilizing them as main protection is controversial and even abortive in order to maintain system stability. In this paper, transient stability of a real industrial network is studied. The study is investigated using critical clearing time (CCT) criterion for different network configuration. Equipments such as generators and motors are modeled and simulated by DIgSILENT software. In addition, the operation of over current relays adjusted by conventional methods is investigated dynamically and its performance is examined under different network configurations.