Distribution systems play a crucial role in ensuring that electricity is delivered to consumers in a reliable and efficient manner. However, managing and maintaining these systems can be a daunting task due to a variety of challenges. It is essential for utilities and policymakers to address these challenges in order to ensure that the distribution system remains robust and reliable in the face of these changes.
Challenges in the Distribution System
The top challenges in the distribution system are:
1. Distribution losses
A distribution system offers a linkage between a high-voltage transmission system and low-voltage consumers where heat loss in an overall network is high due to the high current. Distribution system operators have a financial incentive to diminish losses in these networks. This incentive is evaluated as the difference in the evaluated unit price between real and standard losses.
2. Reliability of the system
The distribution system links the complicated structure of the transmission system to the individual customers. The existing power system is smart, twofold, active, interconnected, interdependent, load-sharing and phased-mission systems. Subsequently, to showcase all these features efficiently it has undergone many modifications in its structure such as:
- Incorporation of new protection devices
- Inclusion of distributed generators in the systems
- Reactive power compensating devices
- Capacitor bank requirements
The inclusion of all such foreign structures may affect the reliability of the system. The reliability of a power system is commonly defined as a measure of the ability of the system to provide the product to the customers with a passable stream. It is considered to be one of the most important performance criteria of the power sector, which includes the planning, performance and maintenance of electric power systems.
3. Contingency analysis
Contingency analysis plays a crucial role in understanding the impacts of sudden line outages due to failures of equipment, transformers, transmission lines, etc. This is mainly reflected in the system due to overburdened parts of the network caused by an irrational power flow in the lines. Its analysis is essential to take the necessary action for maintaining the security and reliable functioning of the system.
It is considered the most significant process in distribution system planning and operation. It has mainly been found that a line outage may lead to overburdened branches and sudden system voltage variations resulting in huge losses to the system in terms of economy, efficiency and execution of all-important performance parameters so the contingency analysis is often used to calculate violations in the predefined norms of the distribution system.
4. Reverse power flow
Distributed generation is considered an essential part of future distribution power systems. Grids are eventually being converted into smart grids with the annexation of advanced and improved, technologically sound distributed generation sets, along with their advanced control systems, adaptive structures, effective sensors, information and communication technologies. The distributed generation insertion has changed the complete mode of operation of the distribution systems. The traditional one-directional flow of power in the lines has changed to a two-way mode which leads to an urgent need to redesign the protection systems. In smart grids, the complicacy of the transformed structures and technologies of the power system is monitored and meticulously controlled by sensors, smart meters, digital controllers and adaptive technologies.
5. Reactive power management
Reactive power is one of the most important factors encountered for ensuring the smooth flow of the apparent power in the power lines. Generators are considered to be the prime source of reactive power and need to comply with the reactive power demand of the system and load.
Due to many undesirable factors and inappropriate functioning of a few components or parts of the system, there may be evidence of an unrealistic flow of excessive reactive power in the transmission periphery which may cause voltage instability and uneconomic network performance. Thus the reactive power control in a minor as well as a major power network, is important, particularly for a steady load. However, the control of reactive power is difficult for network operators in large systems where the system consists of long-length power lines and highly variable loads because of widely and frequently varying meteorological conditions.
6. Voltage profile management
Increasing deployment of distributed generation units in the distribution network brings new challenges, such as voltage fluctuations, power quality hampering and reverse power flows. The sudden changes in electric power generation from the distributed generations due to climate conditions or their internal glitch might cause high-voltage variations. In such critical scenarios, both low load requirements and high power contributions from renewable sources possibly result in voltage, power and load angle limit violations. To ride through this state of a highly approved approach is the disconnection of such units or curtailment of power generation which may lead to several disadvantages such as a sudden reactive power imbalance, harmonic distortion, voltage instability and malfunction of protection devices.
Thus distributed generation insertion has proved to be a boon accompanied by many technical challenges that are definitely required to be analyzed in order to enjoy all the benefits of distributed generation insertion in the distribution networks.
7. Network restructuring
Due to the low-voltage–high-current operating scenarios of the distribution system, I2R losses are the major concern of distribution network operators and need to be taken care of to improve the performance of the system. Network restructuring is one of the methods to deal with this problem which is generally used in low-voltage distribution systems. It is a very effective and conclusive method to save electrical energy. Distribution systems consist of a large number of interconnected radial and mesh networks. The network configuration and structures of distribution systems may be varied through switching operations to reallocate loads in the feeders with exhaustive planning.
8. Impacts of distributed generator insertion
Continuously growing energy requirements resulting due to industrialization, environmental concerns with diminishing fossil fuel resources, network congestion as a result of overburdened lines and declining technical performance are the key motivating factors for the day-to-day increase in integration of both renewable as well as non-renewable distributed generation units and transition of the prevailing power systems into restructured and advanced systems. Improving the technological and economic outcomes as a result of distributed generation allocation is the biggest challenge for distribution network operators for both types of distributed generators. Distribution system engineers showed strong interest in these tiny energy sources due to their technical, economic and environmental enticements. Its impending assistance includes improved system reliability, greenhouse gas emissions and energy loss reductions.
9. Grid security
The changed scenario of the distribution system with many technological changes such as network restructuring, distributed generation insertion and increasing complicity to relieve the network contingency, creates many problems in its normal operation. One of the significant problems is grid security in terms of:
- Altering the status of protection components, such as the setting of relays, circuit breakers, etc.
- Types of relays that were installed at the time of installation by keeping the one-directional state of distribution systems required to be changed due to the bidirectional operating scenario.
- Increased MVA capacity of the conductors
All these issues strongly recommend urgent alteration in the present structure to cope with newly installed technologies.
10. Stability of the system
Stability is the ability of a power system to maintain steady and acceptable limits and standards of performance parameters such as voltage and load angle at all buses under both normal and abnormal (faulty) network conditions. The load on the distribution network shows conscious behavior due to variations in consumer demands. In certain industrial as well as domestic areas, it is often observed that under certain critical loading conditions and faulty situations, the distribution system experiences a voltage collapse which is also called an instability or unstable operation of the system. The main factor causing voltage instability is the inability of power systems to comply with the demand of reactive power and maintenance of required parameters, demand load correlation
11. Inadequacy of the traditional distribution system
The available structure was designed to supply a load that was much less than the ever-increasing load the power system is bearing nowadays. Structure analysts and power system engineers work hard to investigate the means to make the available system compatible to sustain this continuously growing demand. Network modification, renewal at certain sectors or insertion of distributed generation to make it more flexible are some of the remedies that have been incorporated into the system to make it compatible to sustain the enhanced burden of the ever-increasing load.
12. Economic operation of the system
Evaluation of distribution system losses that occurred through generating unit loading plays an important role in the efficiency evaluation of distribution systems. All the enhancements made for reactive power compensation required in distribution systems require an investment and proportional maintenance cost, which must be examined along with the outputs of generating units and energy loss reduction achieved by the compensating devices, along with the benefits of quality and reliability advances which have proved to be the qualitative goals targeted with the use of these devices. The aspects that are responsible for load dispatching have operated with a precise evaluation of the generation costs of each discrete unit, but its assessment certainly necessitates an adequate knowledge of the impacts on system losses occurring from load shifting among various available generation units. In order to function at maximum efficiency, it is necessary to understand and control appropriate generator scheduling, the allocation of an optimal cost of system losses and thereafter evaluate the correlation of these costs with station operational costs. Such a methodology is considered to be an important tool in the maintenance of the operation of existing and working units and in the planning and allocation of proposed generating stations.
13. Deterioration of the grid over the course of time
This factor is completely encompassed by civil engineering but still affects the electrical engineering segment. Like all other plants, power sector structures do not remain untouched by the adverse effects of the progressing course of time. Due to the advance of time and its degrading effects, the efficacy of the system is hampered which in turn is accompanied by economic as well as efficiency losses. Restructuring and load up-gradation need vast investments and planning to incorporate compatible structures to balance the load requirements and sustain the overburdened demands. The adverse effects of the deterioration of the system can be changed by implementing the following means:
- Preventive maintenance
- Replacement of degrading units
- Annual renewal planning
- Implementation of the latest technologies to improve the performance
- Annual performance audit
Apart from these, many other strategies are implemented by network operators to improve system performance and enhance revenue.
14. Impact of worsened climatic conditions
Like all other sectors, the distribution system is also greatly influenced by the impacts of climatic conditions. The performance degradation due to variations in renewable energy generation which is often subjective to climate variations is uncontrolled by human interferences and obligations and is the major concern of evaluation of distribution system operation. The often-found mismatch of generation and electricity consumption results in load shading, load curtailment and deficiency of electricity supply during an electricity consumption peak.