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Panel
12 Sep 2022
This panel session contains the following presentations:
1. Analysis of Charge Accumulation Within Insulating Materials via Numerical Simulation
The high-voltage direct current (HVDC) electrical power transmission system employs direct current (DC) for bulk power transmission. Because of its numerous advantages, such as reliability and economic efficiency, HVDC transmission technology is widely applied in the electrical engineering field. This paper presents a numerical simulation to analyze charge accumulation profile within insulating materials which are Cross-Linked Polyethylene (XLPE), low-density polyethylene (LDPE), and Oil-Impregnated paper insulation. This includes studying and explaining the effect of different values of permittivity and ambient temperature on the development of space charges within different types of insulating materials via a numerical simulation. The bipolar charge transport (BCT) model is used to simulate the behavior of space charge in the insulation materials. The build-up of space charge within the insulation layer can affect the electric field distribution and, in extreme situations, it can lead to insulation failure. The fundamental findings of the numerical simulation in this paper reveal that changes in the ambient temperature and permittivity values affect the dynamics and development of space charges within the insulating materials.
2. The Influence of Fault Current & Soil Resistivity on the Substation Grounding Grid Behaviour
The effects of fault current and soil resistivity on grounding performance are shown in this work. The fault current and soil characteristics are modified from the real values in a case study based on an actual main intake substation grounding grid utilizing CDEGS (Current Distribution, Electromagnetic Fields, Grounding, and Soil Structure Analysis) simulation software. Grounding grids give protection against the step and touch potentials to a limited extent depending on the amplitude and period of ground-fault current that is present. Besides, the soil resistivity of the location in which a grounding grid is placed also determines the performance and safety of the system. Therefore, it is important to carry out the grounding grid assessment, utilizing the field data. The findings show that maximum step and touch voltage and grid resistance increase with fault current and soil resistivity. Although the step and touch voltages, as well as the grid resistance, increase as top layer soil height increases, the grounding system remains safe up to a specific height of the top soil layer, based on certain soil resistivities.
3. The Effect of the Ambient Temperature Profile in the Determination of Power Cable Ratings
Power cables are primarily utilized for power distribution and transmission. It is a combination of one or more individually insulated electrical conductors that are generally kept together by a sheath. The arrangement is utilized for electrical power transmission and distribution. The limitations within which a cable can be used safely are determined by cable ratings. Temperature, voltage, and current are the most common factors to determine the cable ratings. When the cables are equipped in the condition of the surrounding, the cables are likely to experience a change in their ratings as they were installed in various environmental conditions and geographical locations. The IEC Standard as the main reference is used to stimulate the current ratings when the cables are in the surrounding conditions and the effect of the environmental factors such as global warming is also investigated in this paper. The ambient temperature profile which is based on a few of the world continents' profiles and also specifically the ambient temperature profile in Malaysia is studied and presented by varying ambient temperatures in the IEC Standard mathematical algorithm. The result shows that the cable capabilities to carry the current will be affected by the various ambient temperatures in different locations.
4. Reduction of Electricity Cost in Distribution Systems Based on Optimal Switching Configuration
Increasing power consumption and privatization of power networks have prompted utilities to deliver high-quality, dependable facilities to sustain continuous operation and decrease electricity prices. Reducing energy loss in the distribution system helps maintain services and reduce expenses. This paper presents an economic analysis of a practical distribution system for electricity power loss cost reduction. A Mixed Integer Second Order Cone Programming (MISOCP) technique is proposed to achieve the switching sequence from the initial configuration based on minimum power loss during intermittent switching. The Hamming dataset approach reduces search space by taking into account just the radial network topology to attain optimum switching sequences. This work is verified on the actual Malaysian 71 bus distribution system. The results disclosed that the power losses decreased to 114.99 kW and 139.49 kW compared to the initial configuration when the load was 100% and 110%, respectively. Finally, the power loss reduction resulted in saving the cost up to MYR 82,115 and MYR 100,036 when the load level was 100% and 110%, respectively.
5. Analysis of High Penetration Level of Distributed Generation at Medium Voltage Levels of Distribution Networks
The high penetration of distributed generation (DG) including solar PV generation, small hydro generation and bio-energy into the distribution network area has changed the landscape of power systems. In a conventional power system, electricity is expected to flow from power plants, transmission systems and distribution networks, before being distributed to local consumers. However, the level of DG penetration in the distribution network, including by prosumers who install DG especially solar PV systems at their own premises, is increasing every year in many countries including Malaysia. Through the Net Energy Metering (NEM) scheme, prosumers can now export excess energy generated by DG into the grid. This trend is likely to continue driven by rapid advances in the power electronics sector and lower cost of ownership of solar PV systems. However, this trend may lead to several other positive and negative impacts on the distribution network. This paper investigates several impacts of high DG penetration levels on medium voltage (MV) levels of distribution networks including impacts on voltage profile, fault level, network losses, and line loading. Simulation analysis was performed using DIgSILENT PowerFactory software on substations in the MV distribution network. Several scenarios of increasing DG penetration level were simulated and the impacts on the distribution network were analyzed. The study also shows that the use of Volt-VAr Control (VVC) function in smart inverter (SI) is effective in improving voltage regulation in distribution network and implementation of fault current limiter (FCL) effectively mitigates the high fault level at distribution substation.
6. Assessing the Resilience of a Power Distribution System Considering Different Restoration Strategies
Power systems are vulnerable to natural disasters such as hurricanes and floods. These environmental catastrophes are unavoidable and cause massive destruction at the distribution level. Thus, an efficient restoration policy is crucial to recover the electricity supply to the end-user as quickly as possible to minimize their impact. For this purpose, various restoration strategies have been proposed in the existing literature to enhance the resilience of the distribution network. In this work, we have assessed the efficiency of restoration practices that are based on shortest repair time (SRT), number of customers (NOC), betweenness centrality (BC), and first fail first recover (FFFR) policy. The Monte Carlo technique is adapted to introduce random line failures in a modified 33-bus system, and a resilience index (RI) is proposed to quantify the resilience and assess the performance of these policies during the recovery phase. The insights are helpful for utility operators to formulate a resilient restoration policy in the wake of an adverse event.
1. Analysis of Charge Accumulation Within Insulating Materials via Numerical Simulation
The high-voltage direct current (HVDC) electrical power transmission system employs direct current (DC) for bulk power transmission. Because of its numerous advantages, such as reliability and economic efficiency, HVDC transmission technology is widely applied in the electrical engineering field. This paper presents a numerical simulation to analyze charge accumulation profile within insulating materials which are Cross-Linked Polyethylene (XLPE), low-density polyethylene (LDPE), and Oil-Impregnated paper insulation. This includes studying and explaining the effect of different values of permittivity and ambient temperature on the development of space charges within different types of insulating materials via a numerical simulation. The bipolar charge transport (BCT) model is used to simulate the behavior of space charge in the insulation materials. The build-up of space charge within the insulation layer can affect the electric field distribution and, in extreme situations, it can lead to insulation failure. The fundamental findings of the numerical simulation in this paper reveal that changes in the ambient temperature and permittivity values affect the dynamics and development of space charges within the insulating materials.
2. The Influence of Fault Current & Soil Resistivity on the Substation Grounding Grid Behaviour
The effects of fault current and soil resistivity on grounding performance are shown in this work. The fault current and soil characteristics are modified from the real values in a case study based on an actual main intake substation grounding grid utilizing CDEGS (Current Distribution, Electromagnetic Fields, Grounding, and Soil Structure Analysis) simulation software. Grounding grids give protection against the step and touch potentials to a limited extent depending on the amplitude and period of ground-fault current that is present. Besides, the soil resistivity of the location in which a grounding grid is placed also determines the performance and safety of the system. Therefore, it is important to carry out the grounding grid assessment, utilizing the field data. The findings show that maximum step and touch voltage and grid resistance increase with fault current and soil resistivity. Although the step and touch voltages, as well as the grid resistance, increase as top layer soil height increases, the grounding system remains safe up to a specific height of the top soil layer, based on certain soil resistivities.
3. The Effect of the Ambient Temperature Profile in the Determination of Power Cable Ratings
Power cables are primarily utilized for power distribution and transmission. It is a combination of one or more individually insulated electrical conductors that are generally kept together by a sheath. The arrangement is utilized for electrical power transmission and distribution. The limitations within which a cable can be used safely are determined by cable ratings. Temperature, voltage, and current are the most common factors to determine the cable ratings. When the cables are equipped in the condition of the surrounding, the cables are likely to experience a change in their ratings as they were installed in various environmental conditions and geographical locations. The IEC Standard as the main reference is used to stimulate the current ratings when the cables are in the surrounding conditions and the effect of the environmental factors such as global warming is also investigated in this paper. The ambient temperature profile which is based on a few of the world continents' profiles and also specifically the ambient temperature profile in Malaysia is studied and presented by varying ambient temperatures in the IEC Standard mathematical algorithm. The result shows that the cable capabilities to carry the current will be affected by the various ambient temperatures in different locations.
4. Reduction of Electricity Cost in Distribution Systems Based on Optimal Switching Configuration
Increasing power consumption and privatization of power networks have prompted utilities to deliver high-quality, dependable facilities to sustain continuous operation and decrease electricity prices. Reducing energy loss in the distribution system helps maintain services and reduce expenses. This paper presents an economic analysis of a practical distribution system for electricity power loss cost reduction. A Mixed Integer Second Order Cone Programming (MISOCP) technique is proposed to achieve the switching sequence from the initial configuration based on minimum power loss during intermittent switching. The Hamming dataset approach reduces search space by taking into account just the radial network topology to attain optimum switching sequences. This work is verified on the actual Malaysian 71 bus distribution system. The results disclosed that the power losses decreased to 114.99 kW and 139.49 kW compared to the initial configuration when the load was 100% and 110%, respectively. Finally, the power loss reduction resulted in saving the cost up to MYR 82,115 and MYR 100,036 when the load level was 100% and 110%, respectively.
5. Analysis of High Penetration Level of Distributed Generation at Medium Voltage Levels of Distribution Networks
The high penetration of distributed generation (DG) including solar PV generation, small hydro generation and bio-energy into the distribution network area has changed the landscape of power systems. In a conventional power system, electricity is expected to flow from power plants, transmission systems and distribution networks, before being distributed to local consumers. However, the level of DG penetration in the distribution network, including by prosumers who install DG especially solar PV systems at their own premises, is increasing every year in many countries including Malaysia. Through the Net Energy Metering (NEM) scheme, prosumers can now export excess energy generated by DG into the grid. This trend is likely to continue driven by rapid advances in the power electronics sector and lower cost of ownership of solar PV systems. However, this trend may lead to several other positive and negative impacts on the distribution network. This paper investigates several impacts of high DG penetration levels on medium voltage (MV) levels of distribution networks including impacts on voltage profile, fault level, network losses, and line loading. Simulation analysis was performed using DIgSILENT PowerFactory software on substations in the MV distribution network. Several scenarios of increasing DG penetration level were simulated and the impacts on the distribution network were analyzed. The study also shows that the use of Volt-VAr Control (VVC) function in smart inverter (SI) is effective in improving voltage regulation in distribution network and implementation of fault current limiter (FCL) effectively mitigates the high fault level at distribution substation.
6. Assessing the Resilience of a Power Distribution System Considering Different Restoration Strategies
Power systems are vulnerable to natural disasters such as hurricanes and floods. These environmental catastrophes are unavoidable and cause massive destruction at the distribution level. Thus, an efficient restoration policy is crucial to recover the electricity supply to the end-user as quickly as possible to minimize their impact. For this purpose, various restoration strategies have been proposed in the existing literature to enhance the resilience of the distribution network. In this work, we have assessed the efficiency of restoration practices that are based on shortest repair time (SRT), number of customers (NOC), betweenness centrality (BC), and first fail first recover (FFFR) policy. The Monte Carlo technique is adapted to introduce random line failures in a modified 33-bus system, and a resilience index (RI) is proposed to quantify the resilience and assess the performance of these policies during the recovery phase. The insights are helpful for utility operators to formulate a resilient restoration policy in the wake of an adverse event.
Chairs:
Dr. Miszaina Osman
