Non-telecommunication based DC line fault detection methodology for meshed HVDC grids

Abstract

One of the most challenging aspects regarding realisation of meshed high-voltage direct current (HVDC) systems is the handling of DC line faults. Due to the specific DC fault current phenomena, AC fault detection and clearance methods are not applicable in meshed HVDC grids. New fault clearing algorithms and equipment need to be developed. Therefore it is necessary to be aware of the DC fault current characteristics. Starting from a travelling wave approach simplifications for fault currents in low -and high impedance earthed DC grids are derived. On this basis, a non-telecommunication based DC fault detection algorithm is designed. Due to its decentralised implementation, it is very fast acting, reliable and economic in comparison with centralised approaches which are characterised by a parallel telecommunication system. Furthermore it is able to detect pole to pole as well as pole to earth faults in low-and high-impedance earthed DC grid. Finally this fault detection algorithm is validated by numerical case studies.

Present and future multiterminal HVDC systems: current status and forthcoming

“…Since multi-level converters have many advantages over the other technologies, it can be seen that future HVDC grids are going to be based on this technology [3].…”

DC protection in modern HVDC networks: VSC-HVDC and MTDC systems

“…The MMC can be classified into half-bridge MMC (HBMMC), full-bridge MMC (FBMMC), and clamped double sub-module based MMC (CDSM-MMC). The modular feature of MMC makes it easier to increase the capacity of MMC-HVDC and, since a MMC has many advantages over the other technologies, it is very likely that future HVDC grids are based on this technology [13,20,21]. Nevertheless, it has to be noted that 2L-VSC, 3L-VSC, and HBMMC have the same nature during DC side faults, and they require DC CB for clearing the DC fault current [21].…”

“…Existing approaches are based on the detection of wave fronts generated by DC fault using wavelet transformation [13]. In this regard, the wavelet analysis is a powerful method of signal analysis well suited to fault generated signals.…”

“…In differential current protection, the main principle is to measure the currents at both line ends, so a parallel telecommunication link must be available [13]. The difference between the two measure currents is calculated and compared with a threshold, if the threshold is exceeded, the protection is tripped [23].…”

“…Besides, the reliability of the entire protection system would depend on telecommunication system's availability, so telecommunication-based DC protection systems may not be desirable due to economic and reliability reasons. Hence, a local detection principle should be preferred [13].…”