Intermittent Ground Faults Research Articles

Identification of Intermittent Ground Fault Lines in Medium Voltage Shipboard Power Systems

To locate increasingly frequent intermittent ground faults in medium-voltage shipboard power systems, this study proposes a fault branch selection method using wavelet analysis. By analyzing transient fault current characteristics in ship medium-voltage grids, this method utilizes wavelet analysis tools to extract features and obtain modulus maxima of branch currents. Based on a dual threshold detection strategy, the fault branch is then identified. The feasibility and validity of the proposed method are verified through simulations on the Matlab/Simulink platform. The simulation results demonstrate the capability of the wavelet analysis approach to accurately locate intermittent ground faults in ship medium-voltage power systems. This research provides an effective solution for fault branch selection of intermittent grounding faults in ship medium-voltage grids.

Multiparameter Current Protections Against Ground Faults in 6 – 10 kV Cable Networks1

Zero sequence current protections are most widely used for protection from single-phase ground faults in distributed 6 – 10 kV cable networks operating with an isolated neutral. Multiparametric operating principles for current protections are proposed which enhance their sensitivity in stable operation and during the most hazardous arc intermittent ground faults.

配電系統上での間欠地絡事故時に観測される零相電流の特徴を用いた事故様相分類法

配電系統上での間欠地絡事故時に観測される零相電流の特徴を用いた事故様相分類法

Research on Grounding of Shore-to-Ship Power Supply System

To avoid pollution of generator exhaust port after the ship docked, the use of shore power supply is developing direction of port. And the shore power grounding method and related standards needed to be carried out. According to developing status of foreign medium voltage ship and characteristics of navy shipboard power supply, this paper presents a shore power supply network structure and its grounding method. The simulation results show the power supply network structure can effectively suppress the single-phase intermittent ground fault on the system to produce the harm.

Analysis of very-high-resistance grounding in high-voltage longwall power systems

The application of very sensitive ground-fault protection in underground coal mines was demonstrated in the early 1980s for low- and medium-voltage utilization circuits (less than 1 kV), but its commercial application did not occur until the advent of high-voltage utilization circuits on longwalls in the late 1980s. With these high-voltage systems (greater than 1000 V), the Mine Safety and Health Administration initially required a maximum ground-fault resistor current limit of 3.75 A for 4160 V systems and 6.5 A for 2400 V systems in 101-c Petitions for Modification. However, more recent Petitions for Modification have been required to limit maximum ground-fault resistor currents to 1.0 A, or even 0.5 A. Standard practice in other industries generally requires high-resistance grounding to be designed so that the capacitive charging current of the system is less than or equal to the resistor current under a ground-fault condition. The intent of this practice is to prevent the system from developing some of the undesirable characteristics of an ungrounded system, such as overvoltages from inductive-capacitive resonance effects and intermittent ground faults. Shielded cables, which have significantly more capacitance than their unshielded counterparts, are required for high-voltage applications in the mining industry. Thus, with the long cable runs of a high-voltage longwall system, capacitive charging currents may exceed grounding-resistor currents under ground-fault conditions. An analysis of a typical 4160 V longwall power system that utilizes very-high-resistance grounding (grounding-resistor-current limit of 0.5 A) is performed to determine whether or not potential problems exist.

Analysis of one-line ground fault surge on simulated overhead distribution line

One-line fault location techniques of intermittent ground fault points on nongrounded distribution lines are necessary to supply steady electric power for customers. This paper proposes a novel method that uses frequency spectra of transient waveforms at a sending end when an intermittent ground fault occurs. In this method, if a ground fault position differs, it causes a different frequency spectrum pattern for the current or voltage transients at a send end (decided by surge reflection phenomena between the sending end and the ground fault point). Comparison between experimental data of one-line ground fault tests on a simulated overhead line (373 m line length, two branch points) and digital simulation analyses shows that the grounded capacitance of a power source transformer was useful in locating the ground fault point. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 118 (1): 52–60, 1997

Measurement of arc resistance and dielectric breakdown voltage at intermittent grounding of 6.6 kV distribution CVT cable

Overvoltage in power distribution system due to intermittent ground faults was studied by measuring dielectric voltage and resistance. The dielectric breakdown voltage was low at the initial stage of the ground fault, became higher than the system voltage with time, and decreased to a lower value. The arc resistance of the fault point was almost 10 Omega . Agreement between these and calculated results are obtained.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>