## 1 Introduction
### Literature Review  
With the intention of safe operation of HVDC systems, a quick action related to fault identification and tripping circuit breaker is essential [4]. For this purpose, several protection schemes were already proposed in much of the literature. These schemes can be categorized as one-end or multi-ends measurement-based HVDC fault detection schemes. The following are a few examples of multi-ends measurement-based HVDC fault detection schemes: the ratio of transient voltage and current at both ends [5], differential protection based on the compensation of distributed capacitive currents at both ends [6], differential protection based on the value and polarity characteristics of the subtracted both-ends-synchronized current signal, traveling wave (TW) based protection [7], directional protection [8], analyzing transient harmonic currents at both ends [9], and wavelet transform based protection [10; 11; 12]. Similar to fault detection, some examples of the HVDC transmission line's fault location schemes based on multi-end measurements are as follows: TW-based schemes [13; 14; 15; 16; 17] and a few signal processing (SP) based schemes such as discrete wavelet transform [18; 19; 20], s-transform [21], Fourier transforms [22], mathematical morphology [23], and empirical mode decomposition [24]. Here, the TW-based approach has been a well-known fault locating technique for an HVAC system for the last couple of decades. In TW-based schemes, high-speed protection can only be possible with the use of the first incident traveling wave, and the accuracy of fault location can be hampered in the case of very long transmission lines. Moreover, the computation burden, system complexity, and additional processing time involved in SP-based schemes may delay the switching of the DC circuit breaker. In addition to these disadvantages, the multi-end measuring approach faces delays due to the requirement of data transmission, and the overall performance of the system depends on the reliability of communication channels [25]. As the one-end measurement-based schemes are less costly, as well as having less selectivity as compared with multi-end information-based methods, this work proposed a fault detection and location scheme based on single-end measurements. Analysis of single-end measurement-based TW schemes was reported in the literature [26; 27; 28]. However, the requirement of a large sampling rate for data extraction so as to correctly acquire the wave front arrival time is a major disadvantage of this approach [29]. In contrast to this, several authors have proposed one-end measuring-based schemes for detecting faults in the HVDC system. [PERSON] et al. [30] proposed a protection scheme for the HVDC system using rectifier side voltage and current signals. The scheme comprised five major units such as a detection unit, boundary unit, directional unit, faulted pole identification unit, and lightning disturbance identification unit. [PERSON] et al. [31] presented a protection scheme for an HVDC system using frequency-dependent parameters extracted from voltage and current signals measured at one-end. Similarly, the following are the methods used for the protection of HVDC lines using one-end local measures: distance protection based schemes [32], directional and boundary element based method [33; 34], Teager energy operator based schemes [35], short-term Fourier transforms [36], wavelet transform based schemes [26; 37; 38], s-transform based schemes [39], and Hilbert-Huang transform based schemes [40]. However, in these types of schemes, an extensive simulation or analysis is needed to set the thresholds. Providing proper thresholding is a quite difficult task and therefore may be unsuitable to provide a stand-alone protective solution.