A Non-Standard Characteristic Based Protection Scheme for Distribution Networks

Abstract

Abstract:The increasing number of distributed generation (DG) units in the distribution systems poses a challenge on protection systems in terms of coordination. In addition, the single characteristic based conventional protection causes an increase in the primary operation time of the relays due to the coordination between relay pairs. As a consequence, earlier studies investigated the utilization of non-standard characteristics and protection schemes in order to ease the insufficiencies of the standard approach. However, a commonly accepted protection approach that mitigates the effect of DG while providing lower primary operating time by levering the benefits of the non-standard protection strategy has not been developed so far. In order to overcome the aforementioned drawbacks of traditional protection, this paper firstly introduces a non-standard characteristic and then proffers an unconventional protection strategy, which utilizes a double characteristic.The suggested protection approach is tested on the IEEE 14 Bus distribution system including synchronous generator based DG connection. The results show that the proposed characteristic and protection scheme are able to provide a substantial decrease in the operation time of the relays while meeting the coordination requirements.

Detection and Location of Earth Fault in MV Feeders Using Screen Earthing Current Measurements

“…since zero-sequence current flow is not affected by Dy transformers and YYn transformers, ungrounded at MV side [34,35]. Local energy sources could affect zero-sequence current flow if YNyn transformer is used [36,37]. In such case local energy sources i.e., prosumers could have an impact on zero-sequence current flow.…”

Highly sensitive microgrid protection using overcurrent relays with a novel relay characteristic

“…Then, DOCRs programmed with the standard relay curves (1) react following different possible faults depend only on the fault current measured by the relay, considering constant values for the previously obtained TSMs and PSMs. However, the voltage at the relay location can be taken into account in the relay curve equation to reduce the operating time [45][46][47][48][49]. Moreover, DOCRs have installed voltage sensors to discern the fault current direction.…”

“…Although the relay operating time can be significantly reduced using a prominent optimisation method, this reduction is restricted due to relay characteristics. Consequently, different non-standard relay curves have occasionally been proposed in the literatures [45][46][47][48][49]. Some determinant factors should be taken into account to realise appropriate DOCR coordination utilising non-standard curves.…”

“…This case is studied in detail in Section 4. Fourth, selecting new curve characteristics is usually equivalent to introducing new optimisation variables [45][46][47][48][49]. Existing optimisation techniques should overcome several challenges to find the global optima for time setting multipliers (TSMs) and plug setting multipliers (PSMs).…”

“…An increasing number of design variables makes the situation more critical. The design variable numbers for the relay curves proposed in [45][46][47] are 6, 3, and 4, respectively. This quantity is three for the proposed relay curve considering the previous challenges.…”