Mohammad Kashem

Impact of distributed generation on protection of single wire earth return lines

Abstract Distributed generation (DG) inclusion within the grid system potentially introduces problems related to control, protection, harmonics, and network transients. This paper analyses one of the key issues: protection of the network, by ascertaining the impact of rotary DG inclusion on existing protection system of SWER (single wire earth return) lines and the DG sensitivity during faults. The analysis is carried out by estimating fault-sensitivity for the worst-case situation, determining the DG impact on the existing protection scheme, and comparing the network situation with and without DG during the fault. A model of arc voltage is used to represent a fault on a SWER scheme. The size of DG is selected based on the SWER capacity and SWER load. The study is conducted on an example SWER system by considering the SWER lines with and without DG and faults on the SWER backbone and laterals, and simulation results are reported. In every case studied, the fault current from the DG significantly exceeded the DG rating and the DG would have tripped. Thus the system reverts to the case with no DG. Even if DG did not trip, the fault current from the source would be largely independent of the DG, and thus the original feeder protection would continue to provide the same quality of performance. Hence, net sensitivity and existing protection system will not be adversely affected by DG inclusion in SWER lines.

Minimising voltage deviation in distribution feeders by optimising size and location of distributed generation

Abstract A new emerging trend of distribution networks is to use small generating units, known as distributed generation (DG), operating in parallel with the main grid. This kind of distribution networks has enabled DG to support power systems in fulfilling their requirements to increase power output as well as quality of power supply. In order to maximise benefits from the DG system, proper DG planning is necessary. The main purpose of this research is to maximise voltage support through optimal sizing and location of DG. A new methodology is developed to determine an optimal DG size and DG location on the distribution feeder for optimising system voltages. The developed technique is tested on a long radial feeder of a practical system and results are reported.

Improvement of power supply to rural customers through grid-interactive distributed generation

The integration of Distributed Generation (DG) into distribution grid systems introduces problems in network operation, control and protection. Key issues associated with DG inclusion are voltage or current control, cost-effective operation, protection coordination and network transients. Better understanding of these issues and finding solutions to these problems are important to power industries. This paper has addressed the general issues and problems of DG implementation, and presented solutions for effective operation and control of the DG system. The impact of DG on distribution protection has been investigated and the level of fault contribution by DG during a fault has been determined. The contribution of DG to the improvement of power quality and reliability has been examined. Mitigation of voltage dip transients and reduction of harmonics in the network by DG have been analysed through modelling and simulations. Also, criteria to select DG technology and safety issues with DG integration have been discussed.

Energy injection by distributed generation for enhancement of voltage profile in SWER systems

Abstract A system with Distributed Generation (DG) has greater load carrying capacity and can correct for a poor voltage profile during peak loading. This paper addresses the loading patterns of rural feeders and the relative effectiveness of real and reactive injection to support voltage profile in Single Wire Earth Return (SWER) systems. Real and reactive injection on a SWER network has been investigated and required energy for voltage enhancement estimated. DG with real and reactive injection (DG-PQ) using Q priority (DG-QPQ) can drastically reduce fuel and energy requirements compared to the amount required by proportional use of real and reactive power in DG-PQ.