Phase Shifting Transformer (PST) offers a robust means of controlling power flows and effectively rerouting them away from heavily loaded transmission lines. Although PSTs are primarily deployed for congestion management, their ability to redistribute currents across parallel paths means they can also be used to reduce network I²R losses. This paper presents an optimisation framework for minimising active power losses in transmission networks through coordinated deployment and control of multiple PSTs. The problem is formulated as an AC optimal power flow with explicit representation of PST tap positions, yielding a mixed discrete–continuous and highly non-linear search space. To address this challenge, an enhanced DOL–Jaya–AEPI algorithm is developed, which eliminates parameter tuning and integrates elite seeding, dynamic opposition-based learning, and adaptive escape, improving robustness and search efficiency compared to conventional heuristics. The framework is tested on the IEEE 300-bus system using the MATPOWER platform, which provides a standard benchmark for large-scale AC power flow studies. Results show that the algorithm consistently identifies feasible solutions and achieves measurable reductions in losses, with the best outcome obtained using three PSTs, achieving a reduction of about 4% compared to the base case.

The Great Britain (GB) transmission network faces future stress due to geographical imbalances between expanding renewable generation in the North and increasing demand in the South. This imposes security challenges on the power transfer capabilities of the North-South network boundaries. Conventional reinforcements, such as adding new double-circuit 400kV lines, are effective but costly and slow to deliver. This study evaluates the role of Quadrature Boosters (QBs) as a possible low-cost alternative to effectively enhance boundary transfer capability in the network. A DIgSILENT PowerFactory model was built using data from the published 2024 Electricity Ten Year Statement (ETYS). The model incorporated DC power flow and sensitivity analysis and was used to identify critical circuits and influential QBs. In the specific scenario, seven boundary-double-circuit lines plus one strategically placed QB was assessed against an alternative with eight boundary-double-circuits, with the comparison focusing on the transfer capability of the associated boundary. Comparative simulations across three operating scenarios (N-0, N-1, N-D) show that the eight double-circuit baseline achieves greater incremental gains, but the seven boundary-double-circuit with the additional strategically placed QB can deliver comparable transfer capability. This demonstrating the suitability and effectiveness of QB reinforcement in enhancing the boundary transfer capability, with potential to defer or reduce the need for new transmission lines in future planning.

Detecting and locating faults in DC microgrids (DCMGs) is essential for maintaining their reliability and stability. This research introduces an optimized tabular transformer (TabNet) model to accurately locate the fault due to its ability to selectively focus on important features and provide interpretable results, making it well-suited for analyzing the complex relationships in fault-induced traveling wave (TW) signals. To improve the model's performance, TabNet hyperparameters were fine-tuned through grid search. In this work, key input features were extracted from TWs generated during fault events as input to TabNet. These features include the magnitude, polarity, and time of arrival of TWs, which were obtained using a refined time-frequency analysis of high-order synchrosqueezing transform. To make the model's predictions easy to understand, local interpretable model-agnostic explanations were used to explain how different features influenced the results. The proposed method was tested on a simulated DCMG under different fault scenarios. Its performance was compared with other existing techniques. The results showed that the method is more accurate and reliable in locating faults.

The conversion of an existing double-circuit three-phase (3Φ) transmission line into a single six-phase (6Φ) feeder presents a practical solution for enhancing power transfer capacity, because as shown in [1-6] it can operate at a higher phase-to-ground voltage. However, as compared to double-circuit 3Φ lines, possible fault conditions in a 6Φ feeder are notably more complex, with 23 significant fault types and 120 fault combinations. In addition, single-pole tripping is now essential, as disconnecting an entire 6Φ EHV feeder for a fault that involves only one-phase, or even a few phases, is unacceptable from a system stability standpoint. In our previous research [6], a phase-segregated current differential protection scheme that only tripped the faulted phases was shown to operate correctly for all fault types. This paper evaluates the applicability of conventional distance protection using DIgSILENT PowerFactory® with two standard 3Φ “Micromho” relays [7] and special tripping logic.

The proliferation of Electric Vehicle (EV) charging, Heat Pumps (HP), and Photo Voltaic (PV) generation within low voltage (LV) distribution networks is expected to escalate. This growth will cause congestion, triggering reinforcement needs to increase hosting capacity (HC) and maintain power quality and continuity. This paper presents findings from a Phase Switch System (PSS) deployment trial on the UK Power Networks (UKPN) distribution network in London and Brighton. The patented PSS increases HC by dynamically balancing three-phase LV distribution mains (LV-main) through real-time phase switching of conductors. With 2023 loads, results from the trial LV-main that supplies 40 customers, increased HC by up to 232A and 202A on average. Also, it provided an estimated 28 MWh annual energy savings in losses reductions. Crucially, simulations of future 7kW electric vehicle charging loads indicate that over 5 years, the PSS could provide 31A per phase more HC than a new and additional cable rated 500A per phase. This comparison to new cables is made, as the HC they provide is widely understood. The trial showcased the PSS as a flexible, rapidly deployable, cost-effective solution to reduce losses and unlock HC, for low-carbon technology integration into LV networks.

AbstractThe lumped element network model has been proven to be an efficient tool for the interpretation of transformer Frequency Response Analysis. However, it is challenging to obtain parameters of the model if transformer design information is unavailable. In such a case, optimisation algorithms can be used for gray‐box model parameter estimation. A methodology is developed by the authors to establish a transformer network model without winding design data, and instead, end‐to‐end open circuit Frequency Response and other terminal test results are utilised; and Genetic Algorithm is applied to approximate the unknown parameters of the model. The modelling approach developed is independent of the unit number of the network model and therefore guarantees the accuracy of optimisation. Furthermore, it can deal with transformers with a complicated winding structure such as interleaved disc type winding. Two single windings, helical and interleaved disc type, and a single‐phase 144/13 kV 60 MVA transformer are used to demonstrate the method. FRA spectra produced by the best estimated gray‐box model and the corresponding white‐box model are compared. The main features in amplitude and phase spectra are well matched, with low values of Relative Standard Deviation, for both single windings and transformer. Estimated electrical parameters show a high consistency with reference values, which are calculated based on winding design data. This validates the methodology and gives confidence to apply grey‐box modelling for FRA interpretation.

Research into travelling waves used for fault location mainly utilize digital transient models of the power system under fault conditions. Electromagnetic transient analysis is the foundation for travelling wave-based fault location estimation, and when they are applied with precise time synchronization, extremely high accuracy is achieved. Most travelling wave-based fault locators detect the time of arrivals of the fault incident surges at both ends of a transmission line, and this requires a level of time precision compatible with the speed of light. Fault signals are non-stationary and non-periodic, and consequently, an important tool to provide multiresolution analysis of the fault signals is the wavelet transform. Wavelets from Daubechies family are normally recommended by researchers that studied faults generated by electromagnetic simulators. However, the real-world travelling wave fault data described in this paper was obtained from the recording of the actual faults on transmission lines; using synchronized fault locators positioned at both ends of various transmission lines. With decomposition and reconstruction of signals at the scaling level of up to six, this paper provides a thorough comparison between the Daubechies, Biorthogonal, Symlet and Coiflet wavelet families, and underlines their accuracy and reliability for use in fault location analysis.

Quadrature boosters (QBs) are a particular type of phase shifting transformer, used in the UK since 1969 to control power flow in transmission networks. A dual core design, involving a shunt unit and a series unit, is normally applied to QBs with large throughput power. Depending on the operational mode, i.e. bucking or boosting, the magnetic flux distribution behaves differently in both the shunt and series units. In addition, the leakage flux has been found to impose different effects on the main flux in the core leg and yoke, respectively. The state-of-art analytic approach is to reduce the electromagnetic complexity into a low-frequency circuit model to ease the assessment of core saturation in QB at different operating scenarios, this approach is, nevertheless, subject to limitations of the assumptions. This paper presents the finite element modelling studies to support the development of QB equivalent circuit model. A search coil method is implemented to calculate the magnetic flux distribution and assess the influence of leakage flux on core saturation in the core leg and yoke under different QB operational conditions.

Energy demands has considerably grown in the GCC states, including Bahrain, which requires for injecting power from other GCC grids. Distance relay performance along the Bahrain interconnection when 600 MW is injected from the GCC network was investigated using DIgSILENT. GCC network, consisting of Bahrain, Kuwait, and back-to-back high voltage direct current (BTB HVDC) link, was modelled to test the distance relay. When 600 MW is injected from Kuwait, the relay was tested when subjected to infeed sources, parallel line outages, resistive faults, power flow reversal, and mutual coupling. Parallel line outages caused underreaching and overreaching issues, and infeed sources caused non-linear measured impedances along the feeders, limiting the settings selectivity. It was observed that quadrilateral relays are superior under resistive faults. When power flow is reversed, blind zone developed for ground faults, and with mutual coupling between double lines, the relay maloperates for ground faults. Short circuit and electromagnetic transient (EMT) simulations were conducted to observe the effects of injecting power from the BTB link. It contributed low fault currents, and harmonics and distortions were produced due to commutation failure. When the BTB link was the main source, the relay significantly underreached. To conclude, a Permissive Overreaching Transfer Trip (POTT) with weak infeed was recommended.

AbstractThe UK net‐zero target requires the integration of significant renewable energy resources into the electrical grid. This, together with the projected growth in electricity demand imposes practical challenges on the power transfer capability of existing transmission feeders. For environmental and planning reasons, construction of new overhead lines is problematic, and where possible upgrading of existing substations and lines is preferred. This paper investigates the feasibility of transforming an existing three‐phase (3Φ) double‐circuit 400 kV line into a six‐phase (6Φ) feeder for a simulated future GB scenario. Results indicate a 6Φ feeder, operating at a ‘phase‐adjacent phase’ voltage of 400 kV can effectively solve the constraints of boundaries in transmission networks. When considering the various operating contingencies, associated with an important UK network boundary and its expected near‐future winter‐peak power transfer requirements, the thermal overload issues are mitigated by transforming a feeder from 3Φ to 6Φ. The paper demonstrates upgrading to 6Φ technology is a potential solution to certain future boundary constraints and in these cases avoids the need to build new underground or overhead AC/DC lines.

To achieve the UK Net Zero future by 2050, National Grid needs to integrate significantly more renewable generation into the power grid. This increases the level of harmonics, reduces system inertia and adversely affects the fault level and the performance of existing protection relays. One solution to the protection problem is the use of new types of protection that use the change in the voltage and current caused by the fault, often referred to as a superimposed or incremental based protection technique. This paper describes how a superimposed directional comparison protection scheme performed when applied to a reduced section of the full UK National Grid network and relates this to the operating performance of traditional protection. Tests are performed using the simulators DIgSILENT and RelaySimTest configured with different source levels, fault types, fault locations and fault resistances. Results show the superimposed based protection scheme achieves faster fault detection and tripping than conventional protection and is capable of detecting higher resistive faults on networks where the source capacities vary from strong to weak.

This paper outlines a proposal for unit protection of electrical distribution networks using wirelessly communicating Directional Agents. Environmental factors are leading to increasing quantities of dispersed electrical generation being embedded into distribution networks. This causes power flow patterns which differ to those experienced on conventional passive radial networks, leading to problems for classic protection techniques such as non-directional time-graded overcurrent. Employing additional system measurements as well as currents allows more sophisticated techniques to be implemented. For example, combining system voltages and currents in Directional Agents allows the directionality of power flows across networks to be monitored. Directional techniques can provide better selectivity between faulted and un-faulted conditions on the protected network. Further, the increasingly widespread availability of wireless communications affords new opportunities for sharing the directional information across networks to facilitate informed wide-area decision making. This work considers the requirements of unit protection schemes formed from wirelessly connected directionality detecting devices (Directional Agents). The feasibility of wirelessly implementing communications conformant with IEC 61850 communications to transport both GOOSE messages and sampled analogue values is researched. The studies indicate that wireless Ethernet communications are suitable to connect Directional Agents to provide unit protection for wide-area schemes based on directional techniques.

Electric power injection from battery energy storage system (BESS) into the modern power grid have been increasing over the years. In terms of distributed BESS, placement optimisation might be done in various ways such as installing it on the tertiary winding of an individual super grid transformer (SGT). This configuration would benefit from the potential asset utilisation and cost elimination of having a new transformer for the BESS. On the other hand, the existence of the BESS would possibly contribute to insufficient fault current and is affecting the performance of protective relays including distance protection. In this study, the impact of the BESS on the distance protection of a sub-transmission grid has been evaluated. The evaluation involves dynamic performance testing of commercial distance relay using the Common Format for Transient Data Exchange (COMTRADE) files produced from the dynamic simulation in DIgSILENT Power Factory. The results suggest that the BESS would normally provide a significant positive benefit to distance protection if applied to a grid with weaker sources or at a higher source to impedance ratios (SIR). Further, the BESS would cause no significant positive impact to distance relay if the grid sources are strong.

The concept of introducing hybrid off-grid systems has made electricity accessible to areas that are far or have no access to grid network.This paper evaluates the techno-economic and environmental characteristics of a hybrid renewable energy system considering three different scheduling approaches, four different solar tracking systems, two different PV modules and eight scheduling scenarios to supply sustainable electricity to a rural community in Sierra Leone.Each scenario consists of a solar tracking system, a specific type of PV module and a scheduling approach.The aim is to find the most efficient and cost-effective scenario that meets the electrical demands of the village.Results revealed that the 'Two axis tracking system' generated the highest PV power, 28.8% additional power compared to the 'No tracking system' confirming the superiority of using a tracking system though it comes with initial cost repercussions.Also, systems that employed the use of Canadiasolar Dymond CS6K-285M-FG PV module tend to be more efficient and cost-effective than those that employed Sharp ND-250QCS PV module even with the same solar tracking technology and scheduling approach.From the best scheduling approach (third scheduling), Scenario 7 (SC#7) gives the lowest net present cost (NPC) of $1.53M with $0.173/kWh cost of energy (COE) and CO 2 emission of 8.54 kg/yr making it the optimum scenario.A daily operation of the optimum scenario on both a sunny and rainy day confirms that the system is capable of supplying the required electricity for both rainy and dry seasons.Sensitivity analyses explain the high reliance of the system cost on the erratic inflation rate, discount rate and PV derating factor.Maintaining a healthy and sustainable environment depends on the minimum load ratio of both the biogas and diesel generators.

The real-world travelling wave fault data investigated in this paper indicate disturbances generate unpredictable, non-stationary and random waveforms which may cause maloperation of protection and control elements in a power system including travelling wave fault locators (TWFL). This type of fault locator is directly dependent on the detection of an accurate time of arrival (ToA) of travelling waves (TW) generated by a fault. This detection becomes complicated in the presence of disturbances when their ToAs are detected earlier than the fault TWs. Since travelling waves occur in the high-frequency bands (e.g. >50 kHz), in this paper a capacitor voltage transformer is employed to measure the TW voltage signals; this involves acquiring the current flowing to the ground and removing the low-frequency components (50/60 Hz). Disturbances create high magnitude pulses in the pre-fault section of a TW fault signal that last for a short time. Therefore, the time when a TWFL starts its computations requires to be optimised so that the effect of the disturbances is eliminated. The analysis techniques mentioned in this paper are based on real-world travelling wave fault data, and the solution uses statistical tools, such as cost function, mean and standard deviation, alongside Digital Signal Processing algorithms.

Harmonic blocking is usually applied by converter transformer differential protection to prevent protection mal-operation during an inrush condition, but it may incorrectly block the protection during an internal fault. This paper first makes an in-depth analysis on factors that lead to differential protection failure to trip for converter transformer internal faults. The main factor responsible for the protection failure to trip is half-cycle saturation of the converter transformer core, which results from the dc component in the fault current. This suggests that harmonic blocking may not be suitable for differential protection of converter transformers to identify inrush conditions. In this regard, this paper proposes a novel method using mathematical morphology to effectively discriminate between the conditions caused by inrush and internal faults. This method implements the waveform symmetry criterion and improved morphological gradient criterion to distinguish between these two conditions. The effectiveness of the proposed method is evaluated based on extensive simulation, and the presented results show that the proposed method can ensure operation for all types of internal faults. Additionally, this method improves the accuracy of inrush identification, even in extreme cases, such as sympathetic inrush and inrush with current transformer saturation.

A direct lightning strike to transmission lines or a flashover can cause overvoltage on conductors in a transmission system. Their consequences in power system are severe with effects on transmission lines, substations and consumers. Lightning varies in type, magnitude and frequency but can be explained using a mathematical approach, and thus, be modelled in a simulator. A number of simulators are...

Understanding the switching behaviours of Ethernet switches is critically important for analysing the transfer time of time-critical messages, e.g. Sampled Value (SV) and Generic Object Oriented Substation Event (GOOSE) messages in a complex IEC 61850 Ethernet network. Most analytical models and simulation programs estimate the network latency by assuming a symmetrical port speed at ingress and egress ports with fixed switching delays. However, the switching characteristics are product-specific and can vary significantly depending on the types of switching hardware, transferred messages and port speed. This paper evaluates the switching characteristics of PRP/HSR enabled switches by analysing the time required to forward SV, GOOSE and IEEE 1588 messages using various port types and speeds combinations. The obtained switching behaviours provide an insight into the multi-protocol traffic interactions at substation process bus. The results can also be used as a performance reference for power engineers and academic researchers to improve the accuracy of analytical models and simulation platforms.

The design of a directional comparison protection scheme based on the raspberry PI computer is presented in this paper. A prototype directional overcurrent relay was built, and its performance was tested. This prototype could be used as the basis for a simple, more economical protection scheme for future HV and LV networks without compromising the fault clearance requirements of a power system.