Ground Fault Current Research Articles

ANALYSIS OF OVER CURRENT RELAY AND GROUND FAULT RELAY PROTECTION SYSTEM IN SUB-STATION SP-2 TANAH MIRING USING RELAY COORDINATION WITH ETAP BASED

Short-circuit often occur in electricity sub-station SP-2 Tanah Miring, Merauke -Papua which caused by malfuction of Over Current Relay (OCR) and Ground Fault Relay (GFR). In enhancing the performance, it takes analysis of relay coordination using ETAP. At maximum load of feeder SP-9 (917 A) an OCR setting is 4.5 A with TMS 0.46 seconds, GFR setting is 4.58 A with TMS 0.17 seconds. At minimum load (324 A) OCR setting is 1.62 A with TMS 0.29 seconds as for the GFR setting is 1.62 A with TMS 0.22 seconds. At the maximum load of feeder Kebun Cokelat (995 A) an OCR setting is 4.97 A with TMS 0.46 seconds as for GFR set is 4.97 A with TMS 0.17 seconds. At minimum load 100 A, OCR setting is 0.5 A with TMS 0.43 seconds while GFR setting is 0.5 A with TMS 0.35 seconds. Furthermore, if the minimum load reach 98 A then the coordination time of GFR and OCR is 0,5 seconds. This analysis found that relay prohibited to operate above 1100 A (maximum) and below 98 (minimum) due to if it working out of the load range then the coordination time would not meet the manual standard.

Transformerless Inverter Topologies for Single-Phase Photovoltaic Systems: A Comparative Review

In photovoltaic (PV) applications, a transformer is often used to provide galvanic isolation and voltage ratio transformations between input and output. However, these conventional iron- and copper-based transformers increase the weight/size and cost of the inverter while reducing the efficiency and power density. It is therefore desirable to avoid using transformers in the inverter. However, additional care must be taken to avoid safety hazards such as ground fault currents and leakage currents, e.g., via the parasitic capacitor between the PV panel and ground. Consequently, the grid connected transformerless PV inverters must comply with strict safety standards such as IEEE 1547.1, VDE0126-1-1, EN 50106, IEC61727, and $\text{A}S/N$ ZS 5033. Various transformerless inverters have been proposed recently to eliminate the leakage current using different techniques such as decoupling the dc from the ac side and/or clamping the common mode (CM) voltage (CMV) during the freewheeling period, or using common ground configurations. The permutations and combinations of various decoupling techniques with integrated voltage buck–boost for maximum power point tracking (MPPT) allow numerous new topologies and configurations which are often confusing and difficult to follow when seeking to select the right topology. Therefore, to present a clear picture on the development of transformerless inverters for the next-generation grid-connected PV systems, this paper aims to comprehensively review and classify various transformerless inverters with detailed analytical comparisons. To reinforce the findings and comparisons as well as to give more insight on the CM characteristics and leakage current, computer simulations of major transformerless inverter topologies have been performed in PLECS software. Moreover, the cost and size are analyzed properly and summarized in a table. Finally, efficiency and thermal analysis are provided with a general summary as well as a technology roadmap.

CAN总线在小电流接地故障检测中的应用

CAN总线在小电流接地故障检测中的应用

FASD based on BSC method for distribution networks

A Petersen coil was used as a passive arc-suppression device (ASD) to mitigate ground-fault current when a single-phase-to-ground fault occurred in distribution networks. However, passive ASDs cannot compensate for the active and harmonic components of ground-fault current. Furthermore, a massive residual ground-fault current would endanger human life and the reliable operation of distribution networks. To overcome the shortcomings of passive ASDs, a three-phase flexible ASD (FASD) with a three-phase cascaded H-bridge topology was presented. A three-phase FASD connected to a bus bar of distribution networks was employed to compensate for the ground-fault current. In this study, the FASD with the backstepping control (BSC) based on current-compensation principle was proposed to completely eliminate the ground-fault current. The effectiveness of the proposed FASD with the BSC method was verified using the simulation and experimental results.

The Equipment Grounding System as an Effective Bonding Topology for Telecommunications Environments

Bseing provided an adequate telecommunications bonding infrastructure is one of the primary concerns for telecommunications cabling designers and installers for new and existing installations. Although not considered a safety ground where ground-fault current is concerned, the telecommunications bonding infrastructure has importance where the components are intended to equalize potentials in the event of lightning, electrostatic discharge, electromagnetic interference, and other transient events that may be imposed on it, or within telecommunications spaces. Very recently, several telecommunications design groups with varying responsibilities for data center, military encryption, and commercial facilities have explored feasible options in providing an equipotential plane for their telecommunications bonding infrastructure, especially in locations where exposed metal frame of the building is not available; the most prominent of these options being the use of the ac equipment grounding conductor system due to the abundance of metallic surface area utilized for the ac premises wiring system. This article is intended to present field-testing data and draw technical conclusions from the same so as to verify whether the equipment grounding system is viable as an alternative bonding infrastructure plane that can achieve the same effect as the standard practices in place today.

Design and Testing of a Frequency-Selective Grounding for $3\phi$ Power Transformers

Three-phase ( $3\phi$ ) power transformers can have their windings configured to create local neutral points, which can be connected to ground. The grounding of a $3\phi$ power transformer is intended to limit ground currents (including fault currents) and limit ground potentials. These objectives can be translated into the resistive grounding that is usually designed based on system ratings and transformer parameters. The resistive grounding, however, can impact the flow of the harmonic components present in the exciting currents of a $3\phi$ power transformer. As a result, undesired harmonic components are induced in primary and secondary voltages. This article presents the design and performance of a frequency-selective grounding that can achieve the objectives of grounding a $3\phi$ power transformer. The developed grounding is designed to provide a resistive path for low-frequency currents (faults), and to create a low impedance path for high-frequency currents (harmonics). The frequency-selective grounding is experimentally tested for a $3\phi$ power transformer with different primary and secondary winding configurations, different fault types, and source grounding. Test results show that the developed grounding can reduce the ground potential, harmonic distortion in primary and secondary voltages, and ground fault currents with a minimum interference with ground fault protective devices.

Flexible arc-suppression method based on improved distributed commutations modulation for distribution networks

Because of the hazard of single-phase-to-ground faults on distribution networks for human security and device insulation, it is important for the ground-fault current to be eliminated by an arc-suppression device. However, owing to their shortcomings, passive arc-suppression devices cannot compensate the ground-fault current fully. Therefore, active arc-suppression devices have been studied. The flexible arc-suppression device (FASD) with a cascaded H-bridge (HB) topology is one type of active arc-suppression device. An FASD connected to a bus bar of distribution networks is applied to mitigate the ground-fault current. Owing to the high voltage and large current during the ground fault, a large number of HBs are required for the FASD. To modulate the HBs, an improved distributed commutations modulation method, which is combined with the flexible arc-suppression method, is proposed. The proposed modulation strategy aims to minimise the error between the reference signal and the tracking signal during each sampling period. Finally, the proposed strategy is validated via simulations and experiments to confirm its effectiveness for the FASD.

Identification of Ground–fault Current in Various Transformer Connection and Generator Grounding using Symmetrical Components Method

Single line to ground-fault (SLG) fault is the record frequent fault probable to occur in an electric power system. The effect of ground-fault is determined by using grounding method and transformer connections. In this study, the simulation showed the performance of a simple power system within the SLG fault in the system at various transformer connection and generator grounding method. New approach the application of ground fault current calculation using symmetrical components method on unit generator transformers. A symmetrical components method applied with simulation was conducted in Matlab software. The results were then analyzed, presenting a comparison with the fault impact at various transformer connection and generator grounding method. The models of transformer connection for each side (primary and secondary) used were wye (Y), wye-grounded (Yn) and delta (Δ). It was clearly shown that the ground-fault currents at the generator bus had significantly an effect on the type of the transformer connections used during the ground-fault at the secondary side of the transformer.

Research on Single-Phase Grounding Fault Location Technology

In view of the complex structure, large scale and high failure rate of distribution network, as well as many branch lines, large transition resistance, difficult to detect fault signals and difficult to locate accurately., A single-phase grounding fault location method based on single-terminal measurement for distribution network with multi-dominant transmission lines is proposed. This method can solve the problem of reliable monitoring of small current grounding fault through data processing and analysis of measuring units installed at substation equipment and line end, find grounding fault line in time, find fault point, and adopt corresponding treatment measures to block the impact scope of user branch line accident, restore the power supply of non-fault line as soon as possible, and reduce the outage time. Providing further reliable power supply fundamentally solves the problems of reliability and safety of power supply in distribution network. This method only needs to synchronously measure the voltage and current at each end of the line when the parameters of the line are known. The method is simple and the measurement accuracy is high. By locating the single-phase-to-ground fault of multi-dominant power lines, the results show that the method is correct and accurate.

Measures to Minimize Series Faults in Electrical Cords and Extension Cords

In electrical power systems, cords and extension cords are exposed to mechanical damage and other insulation stresses. Mechanical damage to stranded conductors can reduce locally their cross section or break them and cause anomalous local conditions of overheating or arcing. The ordinary protective devices cannot detect the series faults that persist, so the fault point remains energized and is subject to electric shock and fire hazards. Effective protection can be accomplished by implementing active and passive measures: installing arc-fault circuit interrupters or arc-fault detection devices, able to detect arcing faults, or wiring the circuits with a grounding protection conductor to involve the ground in every fault. In this way, residual current protective devices (residual current devices or ground fault protective devices) quickly protect the series faults not only with arc, but also without it. Ground-fault-forced cables facilitate by design the conversion of any kind of cable fault to a ground fault. They are particularly recommended for cords and extension cords, internal circuits to grounded equipment, uninterruptible power system continuity circuits, aircraft circuits, road tunnels, data centers, refrigerated containers parks, residences, and hospitals.

Electrical Safety Analysis in the Presence of Resonant Grounding Neutral

The resonant grounding is one of the possible methods of the system neutral grounding for the medium voltage distribution. IEEE standards do define this grounding configuration, but important advantages and drawbacks of the resonant grounding might not be fully known, due to its rather uncommon application in North America. On the other hand, resonant grounding in Europe is imposed by the increased requirements for power quality, especially for medium-voltage (MV) industrial users, imposed to electric utilities by regulatory authorities, with the purpose to protect the interests of users and consumers. Level of the continuity of the service, magnitude and phase of ground-fault currents, magnitude of touch voltages, all depend on how the neutral is connected to ground. In this paper, the authors will discuss electrical safety features of the resonant ground, and analyze issues when a substation, originally operated with different methods of system neutral grounding, is reconfigured with a resonant ground. In particular, a conservative approach for preserving safety during high-voltage (HV)-MV substations’ reconfiguration is herein proposed; the cases of the substation reconfiguration from resonant grounding to isolated-from-ground and vice versa shall be analyzed. Finally, the analysis of the impact of the use of Petersen coil on the global grounding systems will be provided.

Refinement of the mathematical model of frequency converter cable branch with a single­phase short circuit

The mathematical model of the frequency converter cable branch as a part of the mine section power network with a single phase-to-ground fault is clarified. The model takes into account a discrete nature of the output voltage and power switches commutation inertia of a voltage inverter as a part of the converter. A technique is proposed for the formation of a mathematical model of a cable line with distributed parameters as a set of differential equations of state and algebraic coupling equations in matrix form. In this case, the cable is divided into three-phase elementary sections, for a set of typical equivalent circuits of which a graph is built, the matrix of the main sections and the matrix coefficients of the equations are calculated. The latter are solved by numerical methods. This allows to take into account the wave processes in the cable for a high-frequency pulse-width modulated output voltage of the frequency converter. Also the asymmetry of the insulation ground resistance, accompanying a ground fault, is taken into account. The matrix-topological approach allows to avoid operations with partial derivatives with respect to geometric coordinates of the cable. The relevance of the research resulted from the neglect of significant factors in known models, which reduces the accuracy of the analysis. In particular, the influence of the discrete nature of the output voltage of the frequency converter, the distributed nature of the cable line insulation parameters and the transverse asymmetry in emergency mode on the instantaneous values of the ground fault current are not taken into account. As a result of numerical simulation for the network of specific configuration, it was found that the occurrence of ground fault through a human body in the cable branch of the frequency converter is characterized by an unacceptably high probability of fatal electrocution. The monitoring method of the insulation resistance of the power network branch, equipped with the semiconductor frequency converter, is proved. The implementation of the method will improve the electrical safety of underground electrical networks due to the timely detection of insulation damage of the frequency converter cable branch and the transmission of a signal to turn off the supply voltage.

Small current ground fault location method based on Hilbert transform

A new method for small current grounding system single-phase-to grounding fault location used transient component and Hilbert transform is proposed. The feeder terminal unit detects zero-mode current and line voltage signals, First, perform the Hilbert transform on the transient line voltage, Then multiply the line voltage after the Hilbert transform with the zero-mode current, defined the product as fault direction parameter. The FA master determines the line segment where the fault point is located based on the characteristics of the opposite polarity of the front and rear direction parameters of the fault point. The results of digital simulation prove that the proposed method has certain feasibility.

Перенапряжения от однофазных замыканий в сетях номинального напряжения 110 кВ

Overvoltages induced by single-phase ground faults in 110 kV networks operating in different neutral grounding modes are investigated. Owing to low values of resistance and high values of inductive and capacitive reactances, the transients in power lines and transformers that occur in 110 kV networks differ essentially from similar processes in 6 to 35 kV networks. This difference results in that the transient overvoltage free components have higher amplitudes, and that they have lower attenuation coefficients. It has been established that 110 kV networks cannot operate with the isolated neutral, because the overvoltage in this case may exceed seven times the nominal phase voltage, which would greatly complicate the transformer winding phase insulation. The use of a neutral grounded through resistance or inductive reactance with a value equal to the zero-sequence impedance of the considered circuit significantly reduces the level of ground fault currents and especially overvoltage. Neutral grounding through resistance leads to more efficient results, because the overvoltages and ground fault current have in this case fairly low values. Neutral grounding through inductive reactance results in somewhat higher overvoltage and ground fault current values. If the neutral is grounded through a nonlinear inductance, the overvoltages have still lower values, but the ground fault current approaches the value of the short-circuit current as in the case of the solidly grounded neutral. Comparison of the relevant results relating to various grounding methods of 110 kV networks has shown that the best results are obtained in case of using the neutral grounded through resistance with the value equal to the zero-sequence impedance of the considered network circuit. In this case, the overvoltage levels in the phases do not exceed 1.78 of the phase voltage value, and the ground fault current is much less than the short-circuit current in case of using the solidly grounded neutral. However, in choosing the neutral grounding method, it should be constantly borne in mind what particular task has to be solved: to limit the short-circuit current or to limit overvoltages. In the second case, the use of the neutral grounded through a fast-saturating reactor is a more acceptable choice.

ANALISA RESETTING OVER CURRENT RELAY DAN GROUND FAULT RELAY PADA TRAFO 60 MVA 150/20 kV DAN PENYULANG 20 kV GARDU INDUK PADANG SAMBIAN

Electricity energy needs in Bali have increased annually by 135,2 GWh, as a result, the State-Owned Electrcity Company (PLN) is being required to add new power plants or the addition of transformer to serve load side fedeers. New transformer have been added to Padang Sambian substation and the reconfiguration of Padang Sambian feeders. The reconfiguration causes the feeder impedance value to change, thus affecting the protection system such as Over Current Relay (OCR) and Ground Fault Relay (GFR). Calculation of current setting and OCR and GFR relay work time can minimize the interference that occurs. The amount of short circuit current that occurs in Padang Sambian fedeers was calculated to determine the value of relay settings. The result of the analysis showed that the OCR current setting value for the incoming side of 0,91 A with Time Multiplier Setting (TMS) was 0,2 SI and OCR on the outgoing side of 2,063 A with TMS of 0,161 SI. The value of current setting for the incoming GFR was 0,01 A with TMS of 0,27 SI and the setting value of the GFR current on the outgoing side was 0,16 A with TMS of 0,106 SI. The result of Electrical Power System Analysis (ETAP) simulation obtained an OCR and GFR coordination curve that did not intersect the Time-Curve Current (TCC) characteristic. This shows that coordination runs well and meets sensitivity, reliability, selectivity and speed requirements.

Analysis of Characteristics Over Current Relay and Ground Fault Relay on Feeder Rayon Tabing

The reliability of power distribution of PT PLN (Persero) branch of Padang especially in Rayon Tabing most of the repeaters is still not optimal. This is due to an uncoordinated protection relay on each feeder. One effort made to improve the reliability of electric power is to rearrange the protection of overcurrent relays and ground disturbance relays on the feeder. So coordinated with each other well and is expected if there is interference in one of the repeater will not bring black out on other repeater. In this research we analyzed short circuit current at 20 kV side. From the analysis results obtained new relay protection settings based on the calculation of short-circuit current settings and compare the results with existing protection relays. By making efforts to improve the reliability of electric power is to rearrange the protection relay on each feeder. Based on short circuit current analysis on each repeater, the largest short circuit in 3 phase, 2 phase, and 1 phase disturbance is located at 1% disturbance location and the smallest disturbance is at 100% disturbance location. It can be concluded that the farther the location of the disturbance that occurs the smaller the disturbance, and vice versa, if the location of the disturbance that occurs closer then the greater the noise flow.

Type B Ground-Fault Protection on Adjustable Frequency Drives

This paper describes the International Electrotechnical Commission (IEC) type A (ac only) ground-fault detection circuit and its limitations in accurately detecting electrical ground-fault currents in today's modern electrical installations. Discussed are the effects of waveform modifying power sources and the effect of the dc component on the efficacy of type A safety devices. Limitations of the UL1053 standard for ground-fault sensing and relaying equipment are discussed. The paper will lead to recommending and applying IEC type B (ac/dc) detection technology for solving these shortcomings.

Device for limiting single phase ground fault of mining machines

The paper shows the reasons and consequences of the single-phase ground fault. With all the variety of devices for limiting the current single-phase ground fault, it was found that the most effective are Peterson coils having different switching circuits. Measuring of the capacity of the network is of great importance in this case, a number of options capacitance measurement are presented. A closer look is taken at the device for limiting the current of single-phase short circuit, developed in the Far Eastern Federal University under the direction of Dr. G.E. Kuvshinov. The calculation of single-phase short-circuit currents in the electrical network, without compensation and with compensation of capacitive current is carried out. Simulation of a single-phase circuit in a network with the proposed device is conducted.

STUDI ANALISIS KOORDINASI OVER CURRENT RELAY (OCR) DAN GROUND FAULT RELAY (GFR) PADA RECLOSER DI SALURAN PENYULANG PENEBEL

Short circuit causing over current problem and can might causing interference of the equipment performance such as distribution transformers also causing widespread disruption occurred. In resolving such interference is required as protection system on the distribution system. Seeing all above is needed coordination between the supporting component of the protection system which is consisted of Over Current Relay (OCR) and Ground Fault Relay (GFR). The research was conducted at PT. PLN (Persero) South Bali Area Network, INDONESIA on recloser in the feeder line of Penebel. OCR setting between the Relay feeder of Penebel, Recloser Celagi, Recloser Bakisan, and Recloser Benana still less selective, with time value coordination between average security was still less than 0,2 second. Then OCR setting and GFR relay feeder of Penebel, Recloser Celagi, Recloser Bakisan, and Recloser Benana was recommended for re-setting in order to minimize disruption and electric power distribution system to be reliable.

A Novel Neutral Electromagnetic Hybrid Flexible Grounding Method in Distribution Networks

This paper proposes a flexible neutral grounding method based on electromagnetic hybrid Petersen coil (EHPC), which consists of a magnetically controlled reactor and an active power compensator (APC). Under normal conditions, the system's neutral point grounds through a reactor of high reactance. When a single line-to-earth fault occurs, the EHPC can be controlled flexibly to suppress the recovery voltage of faulty phase and to reduce the ground-fault current to almost zero. This paper expounds the two operating modes and corresponding characteristics, the measuring method of insulation parameters of the system (mainly including capacitance to earth and leakage resistance), and the full compensation principle for arc suppression based on the equivalent negative impedance of EHPC. This paper also proposes a compound control method of neutral-to-earth impedance based on neutral-point displacement voltage and a compensating method for the harmonic component of the ground-fault current. Compared to traditional grounding methods, this method can be fast and reliably make the residual current approach almost zero without arc reignition while greatly reducing the output capacity of APC and, thus, decreasing the cost of this device. Simulations and experiments verify the correctness of this measuring method and feasibility of this flexible grounding control strategy.