Power Substations Research Articles

Research on the application and benefit of energy storage technology

The randomness, volatility and un-dispatch ability of large-scale new energy connected to the grid have caused a series of problems with the stable operation of the grid and great difficulties with power dispatch. The configuration of the energy storage power station and substation is studied through the metering and reliable capacity planning method of energy storage power station and substation capacity planning. This will improve the level of utilization of grid assets and promote the coordinated development of new energy, energy storage and the grid.

전력계통 네트워크 통신방식 변화에 따른 사이버위협 분석 및 대응방안 제시

The Energy Management System (EMS) communicates with power plants and substations, monitors the substations and plant operational status of the transmission and substation system for stability, continuity, real-time, and economy of power supply, and controls power plants and substations. Currently, the power exchange EMS communicates with power plants and substations based on the serial communication-based Distributed Network Protocol (DNP) 3.0 protocol. However, problems such as the difficulty of supply and demand of serial communication equipment and the lack of installation space for serial ports and modems are raised due to the continuous increase in new facilities to perform communication, including renewable power generation facilities. Therefore, this paper presents a TCP/IP-based communication method instead of the existing serial communication method of the power exchange EMS, and presents a security risk analysis that may occur due to changes in the communication method and a countermeasure to the security risk.

Choice of Solutions in the Design of Complex Energy Systems Based on the Analysis of Variants with Interval Weights

Ensuring high-quality and uninterrupted power supply to consumers is one of the main problems of creating reliable power systems of a new generation. It is associated with the implementation of an integral assessment of the technical state of equipment of the power stations and substations, based on technical diagnostics data. Integral assessment involves the choice of ranges of the set of parameters of the technical state for groups of constituent elements of equipment, as well as the determination of their weight coefficients. Currently, the problem is solved with the help of expert assessments, arbitrarily in each specific case, which may lead to an incorrect integral assessment of the state of the equipment. The principle of decomposition makes it possible to determine the individual performance characteristics of each of them. At the same time, their subsequent aggregation ensures that the emergent properties of the system are taken into account. Such an approach was used in this work to evaluate individual types of equipment and their constituent elements. The algorithm for constructing a tree with a minimum random weight, proposed in this paper, makes it possible to increase the validity of decisions. They are made at various stages of designing complex technical systems and include tasks with an integral assessment of the technical state of equipment of power plants and substations. In the proposed algorithm, as a result of using the tree of variants, a matroid is formed, on which, using the “greedy” algorithm, the optimal solution can be determined.

Balancing the Active Power of a Railway Traction Power Substation with an sp-RPC

The railway system is one of the safest, most efficient, and environmentally friendly means of land transport for people and goods. However, as the demand for mobility has increased, the current railway system has shown some weaknesses, requiring an increase in catenary power in order to be able to supply power to longer trains and faster locomotives, as well as to increase rail traffic. This paper proposes a control algorithm to be implemented in a sectioning post-Rail Power Conditioner (sp-RPC). The sp-RPC is connected to the neutral section between two traction power substations (TPS). With the control algorithm, it is possible to minimize the existing unbalance of the active powers of each TPS. In a regenerative braking condition, this surplus energy can be used to assist the traction of another locomotive on the existing overhead line. In this way, it is possible to increase the capacity of the overhead line. The analysis was performed with computer models using a modular multilevel converter (MMC) topology for the sp-RPC. Quantitative results for different consumption events of the locomotives and the analysis of the response to these variations are presented.

Dynamic stray current evaluation model of metro system considering reversible DC traction power system

ABSTRACT Stray current of DC metro system will accelerate metal corrosion. Therefore, it is necessary to evaluate it. With the application of inverter feedback devices in recent years, stray current is more complex due to the DC traction power system is reversible. To evaluate stray current more accurately, the dynamic evaluation model is proposed in this paper. Firstly, traction power substation (TPS) is equivalent to controlled source, considering the diverse operating characteristics. Based on this, the dynamic evaluation model is built with multiple trains running and TPSs operation. Then, considering the nonlinear and multivalued function characteristics of TPS, the solution method is proposed. The problem of slow convergence or even non-convergence in the stray current solving process of the metro system considering reversible DC traction power system is solved. The model is validated by the field test data. Finally, the model is used to obtain dynamic stray current. Result shows that stray current level tends to be higher as traction trains and braking trains run separately and concentratedly in different areas of the line.

Back Flashover Probability of the Overhead Power Line Insulation Taking into Account the Soil Ionization and Frequency Response Features

Back flashovers caused by a lightning strike on an overhead power line tower or overhead ground wire give rise to voltage surges dangerous for the insulation of power substation electrical equipment. A pulse back flashover turns into a short-circuit arc leading to the power line tripping. Calculations of voltage surges in a single–circuit 110 kV power line are carried out using the methods of the grounding devices theory, and the back flashover probability is estimated based on the curve of dangerous currents. The insulation back flashover probability for a power line tower with a ground wire in areas with high-resistance soil is determined by the grounding conductor surge impedance. It is shown that the analysis carried out with taking into account the soil ionization and frequency response features yields an essentially lower back flashover probability. The second ground wire placed under the power line wires reduces the inductance of the ground wires, thereby intensifying the spread of current through the grounding conductors of neighboring towers. This leads to a decreased tower voltage and an increased voltage induced on the wires, thus resulting in a decreased voltage across the insulation voltage and, hence, lower back flashover probability. The factors governing a positive effect from using grounding counterpoises of an overhead power line in areas with high-resistance soil are shown, and the conditions under which this effect is achieved are determined.

Problems of Constructing the Distribution Network Relay Protection System under Market Economy Conditions

The influence of the Russian Federation electric power industry market mechanisms on the operation of the distribution network relay protection system is analyzed. The normative and legal documentation regulating the interaction between various electric power industry entities is studied, and the cause of a problem affecting the construction of the distribution network relay protection system is pointed out. To confirm this hypothesis, an example with connection of a 10/0.4 kV transformer substation is considered. The actuation parameters (current and time) are calculated both for the 10 kV relay protection and 0.4 kV circuit breakers with electronic releasing devices installed in them. The calculation results were used to compile a protective devices selectivity map, based on which areas with non-selective actuation of the transformer substation protection system have been identified. Recommendations on eliminating the current situation associated with limiting the maximum time delay from the transformer substation power supply side are given.

Modeling of Stray Currents From Metro Intruding Into Power System Considering the Complex Geological Conditions in Modern Megacities

The risks of power supply in power systems attributed to stray currents caused by denser metro lines are increasing in modern megacities. Factors such as multi-layered soil and multiple metro operating lines (MOLs) make it more difficult to analyze dc coupling between the metro and power system. This article proposes a model for dc coupling of the metro and power system considering the two systems’ spatial information, the actual multi-layered soil, and the non-linear ionization of soil caused by stray currents. This article presents a dc coupling model suitable for studying multiple metro lines and large-scale power systems in modern megacities, which has an average relative error of 6.3% compared with experimental results. The neutral current of the transformer in a substation is up to 43 A (normal operation requires it to be less than 6 A in amplitude) under the influence of multiple MOL. The non-linear ionization of the soil near the power substations’ grounding network will decrease the soil resistance, this also results in greater dc currents intruding into power substations.

Measurement and Analysis on Magnetic Field Influence of Substation for Magnetic Shielding Device

The residual magnetic field in a magnetic shielding device with a multilayer high permeability material (permalloy) structure can be obtained at the nanotesla (nT) level or even lower. At present, in the process of designing a magnetic shielding device, most of the external environmental magnetic field settings are set at the size of the Earth’s environmental magnetic field, but the instruments inside the magnetic shielding device need to be powered, the active compensation coil needs to be powered, and the degaussing coil of passive shielding layer needs to be powered, so substations need to be used around magnetic shielding devices. The magnetic field generated by the substation will affect the magnetic shielding device, so this paper analyzes and measures the magnetic field generated by the substation. Firstly, the finite element model of a substation is established, and the influence of different substations on the environmental magnetic field is analyzed by changing the power. Secondly, the test method of a substation environment magnetic field is determined. Finally, the site test was carried out to measure the influence of different power substations and different distances on the magnetic field, and its influence on the magnetic shielding device was analyzed, which provided an important basis for the construction of the magnetic shielding device.

Optimal Motion of a Rolling Stock Fleet Under Traction Power System Constraints

The operators of the railway industry [i.e., traction system operator (TSO) and railway system operator (RSO)] are currently involved in a major process of energy transition. Aimed at improving both environmental sustainability and energy efficiency, technological infrastructures are being updated and new operating solutions are studied. Moreover, the business opportunities offered by the new rail market are forcing operators to search for power quality solutions. In this article, an efficiency strategy is proposed for optimally moving a fleet of trains while taking power quality indices into account. A method to relate the traction power requirements to the electrical variables of the railway infrastructure is formulated in terms of the power flow approach. Our numerical simulations focus on the real case of Metro Line 1 in the southern Italian city of Naples. The energy problem of moving the trains on the track is solved by including a set of constraints at the point of common interaction between railway market operators. Specifically, repetitive train starts and their speed profiles are optimally managed in terms of power requirements at traction power substations (TPSs) using power quality constraints. This strategy allows improvements in energy efficiency without compromising the quality of the railway service.

Analysis of Energy Losses in the Novel Distributed Power Supply System for Trams

The traction substation in conventional power supply systems for trams is a bottleneck of the system. It requires the connection with medium-voltage grid, demands high values of instant power and its centralized topology generates additional energy losses. Since the availability of low-power photovoltaic (PV) generation is increasing in the utility system, we propose to replace conventional substations with a distributed system of low-power devices cooperating with low-voltage grid and PV installations owned by individual households. The proposed in this article distributed power supply system for trams (DPSS-T) consists of multiple traction aggregators (TAs) equipped with energy storage devices (ESDs) which are distributed along the tram line. In order to evaluate the benefits of applying DPSS-T this proposed system was compared with the conventional topology regarding the energy losses in terms of annual operation. Moreover, the following aspects have been studied for the wide range EDS sizes and PV generation: PV energy injection into the power utility system, the utilization of installed ESD, and the contribution of PV generation in energy consumed by traction vehicles. At the same time, the energy management for this new topology has been proposed. The ESDs are charged with relatively low power, between tram runs and discharged with full power during the runs. The suggested energy management eliminates peaks in substation power demand. The obtained results show that despite the fact that the proposed DPSS-T is supplied from low-voltage grid the energy losses are reduced by 58%–69%.

Offensive Cyberspace Operations for Cyber Security

This work-in-progress research product covers Offensive Cyberspace Operations for Cyber Security or “Offensive Defense” for Cyber Security. Offensive cyberspace operations are shrouded in secrecy. From an intelligence perspective, this makes sense because of their development since Operation Desert Storm in 1991. The phenomenon, dubbed “Information Warfare,” and to the professionals’ surprise, they could remotely turn off an Iraqi power substation. However, the implication of remotely turning off the power substation was not only to cut off the power source to an Iraqi military headquarters, but it also meant cutting off the power to a nearby hospital, risking the lives of injured Iraqi soldiers protected by the Geneva Conventions. Since the 2000s and onwards, and with the US military recognizing cyberspace as a war-fighting domain, establishing United States Cyber Command (USCYBERCOM) may be a milestone. Thus, researchers have put much thought into cyberspace operations (offensive, defensive), such as doctrine, organizations, training, materials, leadership and education, personnel, facilities, and policy. One phenomenon, dubbed “defending forward,” was coined in the 2018 US Department of Defense Cyber Strategy. The idea is simple: take the fight to the adversary. Other terms include “hunt-forward operations” and “offensive defense.” Therefore, what is “Offensive Defense” for cyber security, and why now?

Review of Degradation Mechanism and Health Estimation Method of VRLA Battery Used for Standby Power Supply in Power System

As the backup power supply of power plants and substations, valve-regulated lead-acid (VRLA) batteries are the last safety guarantee for the safe and reliable operation of power systems, and the batteries’ status of health (SOH) directly affects the stability and safety of power system equipment. In recent years, serious safety accidents have often occurred due to aging and failure of VRLA batteries, so it is urgent to accurately evaluate the health status of batteries. Accurate estimation of battery SOH is conducive to real-time monitoring of single-battery health information, providing a reliable guarantee for fault diagnosis and improving the overall life and economic performance of the battery pack. In this paper, first, the floating charging operation characteristics and aging failure mechanism of a VRLA battery are summarized. Then, the definition and estimation methods of battery SOH are reviewed, including an experimental method, model method, data-driven method and fusion method. The advantages and disadvantages of various methods and their application conditions are analyzed. Finally, for a future big data power system backup power application scenario, the existing problems and development prospects of battery health state estimation are summarized and prospected.

Optimal Inverter-Based DG Placement considering Energy Loss, Reliability, Voltage Sag, DG, and Substation Power Cost Issues

This article presents a comprehensive multi-objective-based optimization problem formulation for finding the optimum size, site, and number of inverter-based DGs (IBDGs) for the operation of the distribution system so as to minimize annual energy cost comprising of costs for the energy loss during the normal operating state, running the IBDGs, substation power including penalty for reverse power flow (if any) and the average energy not supplied as a measure of reliability. Besides, the cost of average apparent load disturbed as a result of voltage sags during faults is also considered. The method is tested on the 33-bus distribution test system using particle swarm optimization. The results so obtained, demonstrate the effectiveness and applicability of the proposed formulation to find the optimum location(s), size(s), and number of IBDG(s) in the radial distribution system with appropriate constraints consideration.

Experimental Platform for Measuring Electrical Discharges in Long Air Gaps With Floating Objects and Its Applications Under Lightning Impulse

Long air gaps containing floating objects are common gaps in power transmission and substation projects. Investigating the discharge mechanism of gaps helps improve the power grid operational reliability. This article presents an experimental platform for measuring the electrical discharges in long air gaps with floating objects, which can measure the applied voltage and the discharge current, and capture the images of the discharge process. By analyzing these measured data, the breakdown voltage characteristics of the gap can be explained. In a long air gap with a floating conductive object under lightning impulse, as the floating object moves from the high voltage (HV) electrode to the ground potential electrode, the breakdown voltage first decreases and then increases, producing a minimum breakdown voltage area (MBVA). In this article, the experimental platform was used to explain the formation of MBVA as an application example. The results show that the formation of MBVA is related to the timing relationship between the breakdown of sub-gap 1 and the discharge in sub-gap 2 entering the final jump. The minimum breakdown voltage occurs at the shortest sub-gap 1 ensuring that the discharge in sub-gap 2 enters the final jump just as sub-gap 1 is broken down.

Research on redundancy margin analysis method of 10kV regional distribution network based on demand-side response

The current status of the regional 10kV distribution network has problems such as the unreasonable capacity declaration, capacity redundancy, and line margin reduction due to a large number of distributed PV and electric vehicle access. In this regard, a redundancy margin analysis method of a 10kV regional distribution network based on demand-side response is proposed. The customer distribution substation power consumption data and operation data are analyzed to establish a 10kV regional distribution network redundancy margin analysis model, and the model is constrained. In the experiments, the proposed method is verified for analysis accuracy. The analysis of the experimental results shows that the proposed method has a high analytical accuracy for analyzing the redundancy margin of the 10kV regional distribution network.

Resilience analysis of cyber-physical systems: A review of models and methods.

Cyber-physical systems (CPSs) are monitored and controlled by a computing and communicating core. This cyber layer enables better management of the controlled subsystem, but it also introduces threats to the security and protection of CPSs, as demonstrated by recent cyberattacks. The resulting governance and policy emphasis on cybersecurity is reflected in the academia by a vast body of literature. In this article, we systematize existing knowledge on CPS analysis. Specifically, we focus on the quantitative assessment of CPSs before and after the occurrence of a disruption. Through the systematic analysis of the models and methods adopted in the literature, we develop a CPS resilience assessment framework consisting of three steps, namely, (1) CPS description, (2) disruption scenario identification, and (3) resilience strategy selection. For each step of the framework, we suggest established methods for CPS analysis and suggest four criteria for method selection. The framework proposes a standardized workflow to assess the resilience of CPSs before and after the occurrence of a disruption. The application of the proposed framework is exemplified with reference to a power substation and associated communication network.The case study shows that the proposed framework supports resilience decision making by quantifying the effects of the implementation of resiliencestrategies.

Multi-Scale Traffic Aware Cybersecurity Situational Awareness Online Model for Intelligent Power Substation Communication Network

Substation communication network (SCN) provides real-time, high-speed, and reliable data transmissions for the advanced monitoring and control functionalities, which are facing increasing cyberspace threats and attacks. Efficient threat perception and cyber situational awareness are essential to enhance secure and reliable SCN operations. This article explores multiscale SCN traffic pattern characteristics with holistic network traffic, separated network traffic for included devices (especially IoT devices) and separated network traffic of certain types of protocol. The proposed online traffic-oriented SCN traffic anomaly detection and cyber situational awareness models are designed for the network anomalies and cyber-attacks that could cause network traffic pattern variations. We leverage a fractional autoregressive integration moving average (FARIMA)-based dynamic threshold model to detect abnormal traffic patterns without sophisticated computations or deep packet inspection. The SCN real-time operation conditions are timely quantified through the statistical methods with the alliance of SCN topology and protocols. The cyber situational awareness model is further carried out to evaluate the most affected protocol and security risks of various devices in SCN using Grubbs’ test. The experiment results are carried out based on a real 110-kV intelligent power substation. The numerical results confirm the comparative low mean square error (MSE) and low complexity of the online traffic characterization when forecasting holistic network traffic and separated network traffics. Furthermore, the timely and quantified cybersecurity risk analysis is conducted based on the SCN traffic with varying scales to detect cyberspace threats and identify the high-risk SCN devices and the most affected protocol.

Determination of the scope of the experimental-calculation method for measuring the touch voltage

The work is devoted to the improvement of methods for determining the normalized parameters of the grounding system (GS) of operating power stations and substations. The aim of the work is determination of the scope of the experimental-calculated method for measuring the touch voltage, depending on short-circuit (SC) current value for the given dimensions of the GS and the type of soil. Methodology. The study analyzed the non-linear effect of the SC current value on the touch voltage, taking into account such factors as the GS size and the soil type. The calculation used statistical data on the GS size and the characteristics of the soil obtained by monitoring the GS state of 585 operating electrical substations with a voltage class of 110-750 kV using the induction method and the method of vertical soil sounding, respectively. For the calculation, a mathematical model of a non-equipotential GS located in a three-layer semiconductor space with plane-parallel boundaries was used, this model was developed using the method of integro-differential equations. Results. To determine the scope of the method, in this work it is proposed to use the linearity criterion, which is determined due to the ratio of the constant of reduced touch voltage to the current value. The example shows the method for determining the threshold minimum and maximum values of the measuring current of the soil, in the range between which the measurements by experimental-calculated methods are impossible. A table of threshold current values has been formed and recommendations have been developed on the possibility of using experimental-measuring methods for determining the touch voltage depending on the GS size and soil characteristics.

Short-term net load forecast in distribution networks with PV penetration behind the meter

In recent years there has been a strong expansion of photovoltaic (PV) distributed generation systems. A high PV penetration level can cause uncertainty in the operation and management processes carried out by electric utilities, since most meters register the net load, i.e., the actual load minus the power generated by the PV systems behind the meter. The goal of this paper was to analyze the difference in the net load forecasting error achieved by models using or not using behind-the-meter PV generation data. The PV plant is connected to the lower voltage side of the power substation, representing a penetration level of more than 35% of the total load. The study shows that the best forecasting results are obtained with an indirect approach using two forecasting models, one for the total load and the other for the PV generation. However, the difference with respect to the results obtained with a unique net load forecasting model is almost negligible, which may be of special interest for power system distributors or other agents who do not have access to behind-the-meter generation data.