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network operators (DNOs) 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 [23]. However, the increased rate of DG deployment provides a prime challenge to distribution network operators because traditional distribution networks are not designed to connect power generation facilities on their doorsteps. With the integration of DGs in these passive networks, wide ranges of alternations and sometimes parameter violations result in variability and uncertainty in the operation of renewable energy resources (RERs). It has been found that renewable DGs reveal many associated power quality (PQ), characteristics hampering, and performance violation challenges to the operators. Power quality is one of the most significant characteristics of renewable DG systems because today’s loads are excessively sensitive to PQ disturbances. Therefore, the need for innovative power quality improvement techniques becomes a foreseeable feature of the restructured power system [24].

      3.3.1.9 Grid Security

      The changed scenario of the distribution system with many technological changes, such as network restructuring, distributed generation insertion, increasing complicity to relieve the network contingency, creates many problems in its normal operation. One of the significant problems is the grid security in terms of:

       Stability

       Altering the status of protection components, such as 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.

      3.3.1.10 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 [25]. 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 parameter, demand load correlation [26].

      3.3.2 Economic Problems

      3.3.2.1 Inadequacy of the Traditional Distribution System Structure to Cope with the Day-by-Day Enhancement of the Load Requirement

      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 in the system to make it compatible to sustain the enhanced burden of the ever increasing load.

      3.3.2.2 Economic Operation of the System

Evaluation of distribution system losses that occurred through generating units loading plays an important role in 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 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 evaluating 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 [27].

      3.3.3 Environmental Problems

      3.3.3.1 Deterioration of the Grid with 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 the economic as well as efficiency losses. Restructuring and load up-gradation needs vast investments and through planning to incorporate the compactible structures to balance the load requirements and sustain the overburdened demands. The adverse effects of 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 have been found to be implemented by network operators to improve the system performance and enhance the revenue.

      3.3.3.2 Impact of Worsened Climatic Conditions

Like all other sectors the distribution system is also greatly influenced by 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 the electricity consumption results in load shading, load curtailment, and deficiency of electricity supply during an electricity consumption peak [28].

      3.4 Conclusion

      The effective operation of an active distribution network requires regulation and control, load forecast, its analysis and execution of adaptive technologies for resilient system operation, grid security monitoring and parameter optimization monitoring, etc. All these operations require advanced data management methods like energy management systems, SCADA, etc. However, to obtain the maximum output from those technologies, all the technical, economic, and environmental issues faced by distribution systems will be well researched, discussed, analyzed, and evaluated. It is also essential to improve performance and quality of power delivery by a distribution network to consumers. The state-of- the-art method of addressing these issues has been presented in this chapter, highlighting the major concerns for a distribution system that offers the best way to adopt installation of new technologies and resources in its territory.

      References

      1 [1] B. Khan, H.H. Alhelou, and F. Mebrahtu, “A holistic analysis of distribution system reliability assessment methods with conventional and renewable energy sources,” AIMS Energy, vol. 7, no. 4, pp. 413–429, 2019.

      2 [2]

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