Substations are increasingly reliant on devices compatible with IEC61850 standards. However, the ... more Substations are increasingly reliant on devices compatible with IEC61850 standards. However, the conformity of a devicewith the standards does not necessarily guarantee interoperability with devices from different manufacturers. The use of devices compatible with IEC61850 standards presents a challenge to many system integrators, especially due to lack of familiarity with features such as Generic Object Oriented Substation Event (GOOSE), reporting, sample values and the need for system redundancy. To facilitate a smooth implementation, all the features and the data exchanges between devices need to be tested to ensure the system operates correctly. It is important to determine the compatibility of the devices made by different manufacturers. This paper presents a technique to assess the performance of Merging Units from different manufacturers, when operating with Intelligent Electronic Devices (IEDs) performing a distance protection function. The performance of the process bus with parallel redundancy protocol is evaluated using a closed loop approach involving a Real Time Digital Simulator.
Journal of Electrical Engineering & Technology
To achieve the UK Net Zero future by 2050, National Grid needs to integrate significantly more re... more 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...
All in-text references underlined in blue are linked to publications on ResearchGate, letting you... more All in-text references underlined in blue are linked to publications on ResearchGate, letting you access and read them immediately.
This paper proposes an algorithm for fault detection, faulted phase and winding identification of... more This paper proposes an algorithm for fault detection, faulted phase and winding identification of a three-winding power transformer based on the induced voltages in the electrical power system. The ratio of the induced voltages of the primary-secondary, primary-tertiary and secondary-tertiary windings is the same as the corresponding turns ratio during normal operating conditions, magnetic inrush, and over-excitation. It differs from the turns ratio during an internal fault. For a single phase and a three-phase power transformer with wye-connected windings, the induced voltages of each pair of windings are estimated. For a three-phase power transformer with delta-connected windings, the induced voltage differences are estimated to use the line currents, because the delta winding currents are practically unavailable. Six detectors are suggested for fault detection. An additional three detectors and a rule for faulted phase and winding identification are presented as well. The proposed algorithm can not only detect an internal fault, but also identify the faulted phase and winding of a three-winding power transformer. The various test results with Electromagnetic Transients Program (EMTP)-generated data show that the proposed algorithm successfully discriminates internal faults from normal operating
Replacing aged transformers requires intensive capital investment and is expensive for utilities ... more Replacing aged transformers requires intensive capital investment and is expensive for utilities in developed countries. A transformer end-of-life model expressed as population failure hazard curve against age is needed in order to predict the number of failure in the future and suggest the long-term capital investment. In this paper the statistical analysis on historical failure data is used to produce the failure hazard in the normal operating stage dominated by the random failure mechanism, while a physical ageing model is built based on scrapping transformer information. By linking the ageing failure mechanism with statistical approach, the population hazard curve against age is produced which can be used by operators to identify the transformer failure number a system can tolerate while maintaining a secured system operation.
Due to safety concerns and the risks associated with an islanded system, current legislation has ... more Due to safety concerns and the risks associated with an islanded system, current legislation has prohibited the islanded operation of distributed generation. However, operation of a temporary island may be a useful support to the main supply. In particular, in the event of an upstream supply outage, the temporary islanding operation of distributed generator (DG) can provide local supplies to critical customers, thus reducing customers’ outage cost and improve the power system reliability. Despite all the benefits that an islanding operation can provide to the power system, there are still many challenges and technical issues regarding its implementation that constrain its operation.
2003 IEEE PES Transmission and Distribution Conference and Exposition (IEEE Cat. No.03CH37495)
The main idea of this paper is to combine the multi-zone operating features of a pilot aided dist... more The main idea of this paper is to combine the multi-zone operating features of a pilot aided distance scheme with the unit protection features of a current differential relay. The combination, a pilot aided multi-zone differential protection scheme can cope with main or primary relay failure, incorrect measured or communicated data and the problems caused by a "stuck" circuit breaker. Simulation studies are used to illustrate the benefits of the scheme when applied to the main and back-up protection of a double circuit EHV transmission network.
Power system islanding can improve the continuity of power supply. Synchronous islanded operation... more Power system islanding can improve the continuity of power supply. Synchronous islanded operation enables the islanded system to remain in phase with the main power system while not electrically connected, so avoiding out-of-synchronism re-closure. Specific consideration is required for the multiple-set scenario. In this paper a suitable island management system is proposed, with the emphasis being on maximum island flexibility by allowing passive islanding transitions to occur, facilitated by intelligent control. These transitions include: island detection, identification, fragmentation, merging and return-to-mains. It can be challenging to detect these transitions while maintaining synchronous islanded operation. The performance of this control system in the presence of a variable wind power in-feed is also examined. A Mathworks SimPowerSystems simulation is used to investigate the performance of the island management system. The benefit and requirements for energy storage, communications and distribution system protection for this application are considered.
IEEE Open Access Journal of Power and Energy, 2021
The real-world travelling wave fault data investigated in this paper indicate disturbances genera... more 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. INDEX TERMS Fault location, optimised time, power network faults, power system disturbance, real-world data, short-circuit fault, travelling waves, travelling wave fault location.
Electrical distribution networks are becoming increasingly complex systems. The addition of embed... more Electrical distribution networks are becoming increasingly complex systems. The addition of embedded generation, sustainable energy projects, demand side participation schemes and smart metering require the system operator to gather an unprecedented level of information in real-time from their network. Current SCADA technologies, such as power-line carrier or slow scan UHF telemetry, have a low throughput (or bandwidth) and would be overwhelmed given the task of providing data service to the volume of devices needing telecoms that are predicted to be installed on the power system in the short to medium term. This paper examines alternative and emerging solutions to providing telecoms access to remote devices, with a focus on IEEE 802.16 "WiMax". WiMax has been gaining momentum over the last few years as a solution in fixed "last mile" environment, providing broadband internet access to rural homes and businesses, as it provides excellent geographic coverage for a reasonable capital investment.
This paper describes a current differential relay for transformer protection that operates in con... more This paper describes a current differential relay for transformer protection that operates in conjunction with a core saturation detection-based blocking algorithm. The differential current for the magnetic inrush or over-excitation has a point of inflection at the start and end of each saturation period of the transformer core. At these instants, discontinuities arise in the first-difference function of the differential current. The second-and third-difference functions convert the points of inflection into pulses, the magnitudes of which are large enough to detect core saturation. The blocking signal is activated if the third-difference of the differential current is larger than the threshold and is maintained for one cycle. In addition, a method to discriminate between transformer saturation and current transformer (CT) saturation is included. The performance of the proposed blocking scheme was compared with that of a conventional harmonic blocking method. The test results OPEN ACCESS Energies 2014, 7 4572 indicate that the proposed scheme successfully discriminates internal faults even with CT saturation from the magnetic inrush, over-excitation, and external faults with CT saturation, and can significantly reduce the operating time delay of the relay.
Abstract. Most substations today contain a large number of Intelligent Electronic Devices (IEDs),... more Abstract. Most substations today contain a large number of Intelligent Electronic Devices (IEDs), each of which captures and stores locally measured analogue signals, and monitors the operating status of plant items. A key issue for substation data analysis is the adequacy of our knowledge available to describe certain concepts of power system states. It may happen sometimes that these concepts cannot be classified crisply based on the data/information collected in a substation. The paper therefore describes a relatively new theory based on rough sets to overcome the problem of overwhelming events received at a substation that cannot be crisply defined and for detecting superfluous, conflicting, irrelevant and unnecessary data generated by microprocessor IEDs. It identifies the most significant and meaningful data patterns and presents this concise information to a network or regionally based analysis system for decision support. The operators or engineers can make use of the summar...
Replacing aged transformers requires intensive capital investment and is expensive for utilities ... more Replacing aged transformers requires intensive capital investment and is expensive for utilities in developed countries. A transformer end-of-life model expressed as population failure hazard curve against age is needed in order to predict the number of failure in the future and suggest the long-term capital investment. In this paper the statistical analysis on historical failure data is used to produce the failure hazard in the normal operating stage dominated by the random failure mechanism, while a physical ageing model is built based on scrapping transformer information. By linking the ageing failure mechanism with statistical approach, the population hazard curve against age is produced which can be used by operators to identify the transformer failure number a system can tolerate while maintaining a secured system operation.
Power Engineering Society, IEEE Winter Meeting, 2002
A simulation model of a continuous disc type 6.6 kV transformer winding was used to study the pro... more A simulation model of a continuous disc type 6.6 kV transformer winding was used to study the propagation behaviour of partial discharge (PD) pulses. The model based on multi-conductor transmission line theory uses a single turn as a circuit element with the capacitance, inductance, and losses calculated as distributed parameters. Transfer functions that describe how the location of the PD
2018 53rd International Universities Power Engineering Conference (UPEC)
Transient analysis is a crucial tool in the design and operation of a power network. Numerous pow... more Transient analysis is a crucial tool in the design and operation of a power network. Numerous power system analysis methodologies are implemented with different accuracy levels depending on the requirements for transient studies. The aim of this paper is to investigate the differences and similarities of two different methods of transient analysis applied to the occurrence of faults in overhead transmission lines. The first method is based on frequency response analysis undertaken by Peter Crossley in the early 1980s using a UK General Electric Company (GEC) simulator. The output results are compared to those generated by the PSCAD/EMTDC programme. Both represent the transient changes in the currents immediately after the occurrence of faults. However, they differ in details especially when the transient responses of the incremental phase currents are examined. The wave forms obtained from both approaches to modelling emphasise the enhanced accuracy of modern simulators. This study is important in validating the accuracy of a simulator when applied to the transient analysis of the current travelling waves resulting from a short circuit on a transmission line.
2018 53rd International Universities Power Engineering Conference (UPEC)
Transient analysis is a crucial tool in the design and operation of a power network. Numerous pow... more Transient analysis is a crucial tool in the design and operation of a power network. Numerous power system analysis methodologies are implemented with different accuracy levels depending on the requirements for transient studies. The aim of this paper is to investigate the differences and similarities of two different methods of transient analysis applied to the occurrence of faults in overhead transmission lines. The first method is based on frequency response analysis undertaken by Peter Crossley in the early 1980s using a UK General Electric Company (GEC) simulator. The output results are compared to those generated by the PSCAD/EMTDC programme. Both represent the transient changes in the currents immediately after the occurrence of faults. However, they differ in details especially when the transient responses of the incremental phase currents are examined. The wave forms obtained from both approaches to modelling emphasise the enhanced accuracy of modern simulators. This study is important in validating the accuracy of a simulator when applied to the transient analysis of the current travelling waves resulting from a short circuit on a transmission line.
Replacing aged transformers requires intensive capital investment and is expensive for utilities ... more Replacing aged transformers requires intensive capital investment and is expensive for utilities in developed countries. A transformer end-of-life model expressed as population failure hazard curve against age is needed in order to predict the number of failure in the future and suggest the long-term capital investment. In this paper the statistical analysis on historical failure data is used to produce the failure hazard in the normal operating stage dominated by the random failure mechanism, while a physical ageing model is built based on scrapping transformer information. By linking the ageing failure mechanism with statistical approach, the population hazard curve against age is produced which can be used by operators to identify the transformer failure number a system can tolerate while maintaining a secured system operation.
High economic operation cost in power systems is one of the challenges toward the development of ... more High economic operation cost in power systems is one of the challenges toward the development of the new smart distribution networks. Designing an energy storage system (ESS) is an essential part to manage and control the total operation cost as well as improve reliability and security in power systems. One of the major concerns of installing ESS is the transmission lines capacity constraint. Therefore, the right location of ESS is important to maximize the economic benefits. In this paper, centralized and distributed ESS with fixed capital cost are proposed to minimize the total operation cost. Economic dispatch (ED) technique and unit commitment (UC) are formulated to calculate the minimum operation cost. Constraints of thermal units, transmission lines and energy storage are included to formulate the proposed approach. Mixed integer programming (MIP) is used to model the ED and UC as well as the penetration of ESS. A six-bus system is used in all the examples studied to show the ...
Substations are increasingly reliant on devices compatible with IEC61850 standards. However, the ... more Substations are increasingly reliant on devices compatible with IEC61850 standards. However, the conformity of a devicewith the standards does not necessarily guarantee interoperability with devices from different manufacturers. The use of devices compatible with IEC61850 standards presents a challenge to many system integrators, especially due to lack of familiarity with features such as Generic Object Oriented Substation Event (GOOSE), reporting, sample values and the need for system redundancy. To facilitate a smooth implementation, all the features and the data exchanges between devices need to be tested to ensure the system operates correctly. It is important to determine the compatibility of the devices made by different manufacturers. This paper presents a technique to assess the performance of Merging Units from different manufacturers, when operating with Intelligent Electronic Devices (IEDs) performing a distance protection function. The performance of the process bus with parallel redundancy protocol is evaluated using a closed loop approach involving a Real Time Digital Simulator.
Journal of Electrical Engineering & Technology
To achieve the UK Net Zero future by 2050, National Grid needs to integrate significantly more re... more 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...
All in-text references underlined in blue are linked to publications on ResearchGate, letting you... more All in-text references underlined in blue are linked to publications on ResearchGate, letting you access and read them immediately.
This paper proposes an algorithm for fault detection, faulted phase and winding identification of... more This paper proposes an algorithm for fault detection, faulted phase and winding identification of a three-winding power transformer based on the induced voltages in the electrical power system. The ratio of the induced voltages of the primary-secondary, primary-tertiary and secondary-tertiary windings is the same as the corresponding turns ratio during normal operating conditions, magnetic inrush, and over-excitation. It differs from the turns ratio during an internal fault. For a single phase and a three-phase power transformer with wye-connected windings, the induced voltages of each pair of windings are estimated. For a three-phase power transformer with delta-connected windings, the induced voltage differences are estimated to use the line currents, because the delta winding currents are practically unavailable. Six detectors are suggested for fault detection. An additional three detectors and a rule for faulted phase and winding identification are presented as well. The proposed algorithm can not only detect an internal fault, but also identify the faulted phase and winding of a three-winding power transformer. The various test results with Electromagnetic Transients Program (EMTP)-generated data show that the proposed algorithm successfully discriminates internal faults from normal operating
Replacing aged transformers requires intensive capital investment and is expensive for utilities ... more Replacing aged transformers requires intensive capital investment and is expensive for utilities in developed countries. A transformer end-of-life model expressed as population failure hazard curve against age is needed in order to predict the number of failure in the future and suggest the long-term capital investment. In this paper the statistical analysis on historical failure data is used to produce the failure hazard in the normal operating stage dominated by the random failure mechanism, while a physical ageing model is built based on scrapping transformer information. By linking the ageing failure mechanism with statistical approach, the population hazard curve against age is produced which can be used by operators to identify the transformer failure number a system can tolerate while maintaining a secured system operation.
Due to safety concerns and the risks associated with an islanded system, current legislation has ... more Due to safety concerns and the risks associated with an islanded system, current legislation has prohibited the islanded operation of distributed generation. However, operation of a temporary island may be a useful support to the main supply. In particular, in the event of an upstream supply outage, the temporary islanding operation of distributed generator (DG) can provide local supplies to critical customers, thus reducing customers’ outage cost and improve the power system reliability. Despite all the benefits that an islanding operation can provide to the power system, there are still many challenges and technical issues regarding its implementation that constrain its operation.
2003 IEEE PES Transmission and Distribution Conference and Exposition (IEEE Cat. No.03CH37495)
The main idea of this paper is to combine the multi-zone operating features of a pilot aided dist... more The main idea of this paper is to combine the multi-zone operating features of a pilot aided distance scheme with the unit protection features of a current differential relay. The combination, a pilot aided multi-zone differential protection scheme can cope with main or primary relay failure, incorrect measured or communicated data and the problems caused by a "stuck" circuit breaker. Simulation studies are used to illustrate the benefits of the scheme when applied to the main and back-up protection of a double circuit EHV transmission network.
Power system islanding can improve the continuity of power supply. Synchronous islanded operation... more Power system islanding can improve the continuity of power supply. Synchronous islanded operation enables the islanded system to remain in phase with the main power system while not electrically connected, so avoiding out-of-synchronism re-closure. Specific consideration is required for the multiple-set scenario. In this paper a suitable island management system is proposed, with the emphasis being on maximum island flexibility by allowing passive islanding transitions to occur, facilitated by intelligent control. These transitions include: island detection, identification, fragmentation, merging and return-to-mains. It can be challenging to detect these transitions while maintaining synchronous islanded operation. The performance of this control system in the presence of a variable wind power in-feed is also examined. A Mathworks SimPowerSystems simulation is used to investigate the performance of the island management system. The benefit and requirements for energy storage, communications and distribution system protection for this application are considered.
IEEE Open Access Journal of Power and Energy, 2021
The real-world travelling wave fault data investigated in this paper indicate disturbances genera... more 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. INDEX TERMS Fault location, optimised time, power network faults, power system disturbance, real-world data, short-circuit fault, travelling waves, travelling wave fault location.
Electrical distribution networks are becoming increasingly complex systems. The addition of embed... more Electrical distribution networks are becoming increasingly complex systems. The addition of embedded generation, sustainable energy projects, demand side participation schemes and smart metering require the system operator to gather an unprecedented level of information in real-time from their network. Current SCADA technologies, such as power-line carrier or slow scan UHF telemetry, have a low throughput (or bandwidth) and would be overwhelmed given the task of providing data service to the volume of devices needing telecoms that are predicted to be installed on the power system in the short to medium term. This paper examines alternative and emerging solutions to providing telecoms access to remote devices, with a focus on IEEE 802.16 "WiMax". WiMax has been gaining momentum over the last few years as a solution in fixed "last mile" environment, providing broadband internet access to rural homes and businesses, as it provides excellent geographic coverage for a reasonable capital investment.
This paper describes a current differential relay for transformer protection that operates in con... more This paper describes a current differential relay for transformer protection that operates in conjunction with a core saturation detection-based blocking algorithm. The differential current for the magnetic inrush or over-excitation has a point of inflection at the start and end of each saturation period of the transformer core. At these instants, discontinuities arise in the first-difference function of the differential current. The second-and third-difference functions convert the points of inflection into pulses, the magnitudes of which are large enough to detect core saturation. The blocking signal is activated if the third-difference of the differential current is larger than the threshold and is maintained for one cycle. In addition, a method to discriminate between transformer saturation and current transformer (CT) saturation is included. The performance of the proposed blocking scheme was compared with that of a conventional harmonic blocking method. The test results OPEN ACCESS Energies 2014, 7 4572 indicate that the proposed scheme successfully discriminates internal faults even with CT saturation from the magnetic inrush, over-excitation, and external faults with CT saturation, and can significantly reduce the operating time delay of the relay.
Abstract. Most substations today contain a large number of Intelligent Electronic Devices (IEDs),... more Abstract. Most substations today contain a large number of Intelligent Electronic Devices (IEDs), each of which captures and stores locally measured analogue signals, and monitors the operating status of plant items. A key issue for substation data analysis is the adequacy of our knowledge available to describe certain concepts of power system states. It may happen sometimes that these concepts cannot be classified crisply based on the data/information collected in a substation. The paper therefore describes a relatively new theory based on rough sets to overcome the problem of overwhelming events received at a substation that cannot be crisply defined and for detecting superfluous, conflicting, irrelevant and unnecessary data generated by microprocessor IEDs. It identifies the most significant and meaningful data patterns and presents this concise information to a network or regionally based analysis system for decision support. The operators or engineers can make use of the summar...
Replacing aged transformers requires intensive capital investment and is expensive for utilities ... more Replacing aged transformers requires intensive capital investment and is expensive for utilities in developed countries. A transformer end-of-life model expressed as population failure hazard curve against age is needed in order to predict the number of failure in the future and suggest the long-term capital investment. In this paper the statistical analysis on historical failure data is used to produce the failure hazard in the normal operating stage dominated by the random failure mechanism, while a physical ageing model is built based on scrapping transformer information. By linking the ageing failure mechanism with statistical approach, the population hazard curve against age is produced which can be used by operators to identify the transformer failure number a system can tolerate while maintaining a secured system operation.
Power Engineering Society, IEEE Winter Meeting, 2002
A simulation model of a continuous disc type 6.6 kV transformer winding was used to study the pro... more A simulation model of a continuous disc type 6.6 kV transformer winding was used to study the propagation behaviour of partial discharge (PD) pulses. The model based on multi-conductor transmission line theory uses a single turn as a circuit element with the capacitance, inductance, and losses calculated as distributed parameters. Transfer functions that describe how the location of the PD
2018 53rd International Universities Power Engineering Conference (UPEC)
Transient analysis is a crucial tool in the design and operation of a power network. Numerous pow... more Transient analysis is a crucial tool in the design and operation of a power network. Numerous power system analysis methodologies are implemented with different accuracy levels depending on the requirements for transient studies. The aim of this paper is to investigate the differences and similarities of two different methods of transient analysis applied to the occurrence of faults in overhead transmission lines. The first method is based on frequency response analysis undertaken by Peter Crossley in the early 1980s using a UK General Electric Company (GEC) simulator. The output results are compared to those generated by the PSCAD/EMTDC programme. Both represent the transient changes in the currents immediately after the occurrence of faults. However, they differ in details especially when the transient responses of the incremental phase currents are examined. The wave forms obtained from both approaches to modelling emphasise the enhanced accuracy of modern simulators. This study is important in validating the accuracy of a simulator when applied to the transient analysis of the current travelling waves resulting from a short circuit on a transmission line.
2018 53rd International Universities Power Engineering Conference (UPEC)
Transient analysis is a crucial tool in the design and operation of a power network. Numerous pow... more Transient analysis is a crucial tool in the design and operation of a power network. Numerous power system analysis methodologies are implemented with different accuracy levels depending on the requirements for transient studies. The aim of this paper is to investigate the differences and similarities of two different methods of transient analysis applied to the occurrence of faults in overhead transmission lines. The first method is based on frequency response analysis undertaken by Peter Crossley in the early 1980s using a UK General Electric Company (GEC) simulator. The output results are compared to those generated by the PSCAD/EMTDC programme. Both represent the transient changes in the currents immediately after the occurrence of faults. However, they differ in details especially when the transient responses of the incremental phase currents are examined. The wave forms obtained from both approaches to modelling emphasise the enhanced accuracy of modern simulators. This study is important in validating the accuracy of a simulator when applied to the transient analysis of the current travelling waves resulting from a short circuit on a transmission line.
Replacing aged transformers requires intensive capital investment and is expensive for utilities ... more Replacing aged transformers requires intensive capital investment and is expensive for utilities in developed countries. A transformer end-of-life model expressed as population failure hazard curve against age is needed in order to predict the number of failure in the future and suggest the long-term capital investment. In this paper the statistical analysis on historical failure data is used to produce the failure hazard in the normal operating stage dominated by the random failure mechanism, while a physical ageing model is built based on scrapping transformer information. By linking the ageing failure mechanism with statistical approach, the population hazard curve against age is produced which can be used by operators to identify the transformer failure number a system can tolerate while maintaining a secured system operation.
High economic operation cost in power systems is one of the challenges toward the development of ... more High economic operation cost in power systems is one of the challenges toward the development of the new smart distribution networks. Designing an energy storage system (ESS) is an essential part to manage and control the total operation cost as well as improve reliability and security in power systems. One of the major concerns of installing ESS is the transmission lines capacity constraint. Therefore, the right location of ESS is important to maximize the economic benefits. In this paper, centralized and distributed ESS with fixed capital cost are proposed to minimize the total operation cost. Economic dispatch (ED) technique and unit commitment (UC) are formulated to calculate the minimum operation cost. Constraints of thermal units, transmission lines and energy storage are included to formulate the proposed approach. Mixed integer programming (MIP) is used to model the ED and UC as well as the penetration of ESS. A six-bus system is used in all the examples studied to show the ...
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Papers by PETER CROSSLEY