Fast Fault Identification in Bipolar HVDC Grids: A Fault Parameter Estimation Approach

Abstract

The protection of meshed HVDC grids requires the fast identification of faults affecting the transmission lines. Communication-based methods are thus not suited due to the transmission delays. Many approaches involving a model of the transient behavior of the faulty line have recently been proposed. Nevertheless, an accurate description of the traveling wave phenomenon in multi-conductor lines such as overhead lines requires complex computations ill-suited for fast fault identification.This paper presents a single-ended fault identification algorithm using a closed-form parametric model of the fault transient behavior. The model combines physical and behavioral parts and depends explicitly on the parameters that characterize the fault, namely the fault distance and impedance. When a fault is suspected, the fault parameters are estimated so that the model fits best the received measurements. The confidence region of the estimated fault parameters is used to decide whether the protected line is actually faulty or not.The proposed algorithm is tested on a 4 station grid simulated with EMTP-RV software. The method is able to identify the faulty line using a measurement window of less than 0.5 ms. This allows ultra-fast fault clearing and can hence improve the overall reliability of future HVDC grids.

Guidelines for EMT Transmission Line Models for Time-Domain Protection Algorithms

“…Algorithms operating in the modal domain use a constant transformation matrix e.g. in [10], [21], [22]. Often the Clark transformation is used for this purpose, because of its real and constant transformation matrix [23].…”

“…The type a algorithm in [10] aims at a detection time of 0.5 ms. The frequency range of interest is 167 kHz -0.5 MHz (1 MHz sampling rate).…”

“…To show the effects of line geometry in modal transformation, the comparison in this paper uses the benchmark model as a reference. By contrast, algorithm [10] applies the ideal line model. The ideal line model includes the delay effect of distributed lines (resonant peaks), but shows low damping at high frequencies (Fig.…”

“…Time-domain protection algorithms have been developed, but not yet (widely) used, to provide for the need of fast and dependable protection e.g. [10]- [14]. These protection algorithms use different transmission line models, ranging from simple to detailed, state-of-the-art line models.…”

Supervisory control of post-fault restoration schemes in reconfigurable HVDC grids

“…This is particularly important under safety-critical situations, such as the implementation of automatic post-fault restoration schemes. Most of the available literature regarding the protection of HVDC grids focus on the descriptions of fault detection [3] and protection strategies [4], providing extensive data about the electrical behavior of grid components during the fault recovery. However, little information is given on the development of the logical rules used in these studies and their guarantees regarding correctness and deadlocks, with automatic control sequences usually presented through generic flowcharts.…”