Ground Currents Research Articles

Investigating the impacts of high voltage powerlines on ground current fields

Stray currents are a typical problem of areas crossed by electric railways. This well-known phenomenon can cause significant damage to all underground metallic installations, especially in case of DC stray currents. In areas close to the railway, the presence of stray currents is expected, and protective measures are applied to all sensitive installations like pipelines. However, field measurements have shown that the presence of high voltage power lines can significantly affect the ground current field due to the well-grounded ground wire representing an excellent alternative path for ground currents. This way, stray currents can appear in areas where the presence of ground current field from DC traction is normally not expected. Preliminary simulations have confirmed that high voltage power lines are a significant element affecting the spreading of ground current and the presence of high voltage power lines must be considered when investigating the ground current field of an area. However, these simulations were performed only for a limited area with a very simplified geometry of railway truck and a single power line. This paper presents results of a more complex simulation involving a large area crossed by a DC railway traction system and a complex high voltage network. The simulation is based on real topology representing an area around the town of Zilina, an industrial area with a complex high voltage network and an important railway hub.

Implementation and reliability analysis of a new transformerless high‐gain DC‐DC converter for renewable energy applications

AbstractIn this paper, a new high‐gain quadratic boost DC‐DC converter is proposed for a DC microgrid. The converter has a voltage multiplier cell made up of switched inductors to obtain a high voltage at the output. It has a common ground and continuous input current, which makes the converter feasible for renewable energy and DC microgrid applications. The proposed topology consists of a single switch which makes the control simple. The converter achieves a gain of four times the traditional quadratic boost converter and can also operate in continuous and discontinuous conduction modes. The voltage stress across the switch and all the other passive components is less than the output voltage. The variation of voltage gain in the case of parasitic resistances is also shown. The reliability analysis of the proposed converter using Markov modeling is also presented by considering both open‐circuit and short‐circuit faults across the semiconductor devices. A 200 W prototype of the converter is also prepared and the hardware results of the converter are also presented in the paper. The converter operates at high efficiency of 96% at 100 W output power operation. The variation of reliability with different converter parameters like the duty cycle and the input voltage is also discussed in the paper. The experimental results in fault conditions are also shown.

고속철도 신호기계실의 접지전류 개선 효과에 관한 연구

Through construction of high-speed railways and railway electrification projects in Korea, individual(or independent) grounding methods were replaced with common grounding methods. Common grounding methods can eliminate potential difference between equipments connected with common grounding wires, but the wires are used as return current paths such as rails. A track circuit cable consists of signal wires and shielding conductors, and connects track circuit devices installed along tracks, transmitters and receivers located in a signal machine room. Shielding conductors at one end of the track circuit cable are connected to the common earth wire, and the conductor at the other end are connected to a grounding terminal of the signal machine room. It was confirmed through measurements that impulse surge current invades to the signal machine room through shield conductors of a track circuit cable connected to grounding wires. Also, it was confirmed that steel frame grounding was used as a path for another impulse surge current to enter the room. Therefore, in this paper, the ground current status of the signal room is analyzed, the improvements of grounding facilities in the signal room are listed, and the improvement effects of the ground current are presented.

The Analysis, Modeling, and Capabilities of Grounding System Designs

The selection of a grounding configuration and design of a grounding impedance is of vital importance for the stability and functionality of power systems, including industrial and commercial power systems. These key aspects of grounding systems have been the subject of various standards, industrial codes, and recommended practices. In this article, a review, modeling, and analysis of different grounding system designs are provided. The different grounding system design discussed in this article is compared in terms of the ground potential, ground currents, and overvoltage during ground faults. The various grounding system designs are implemented for power systems components in order to assess their capabilities and performance. Several tests are conducted for ground faults, when different grounding system designs are used. Test results show that some grounding system design can limit ground currents, with minor effects on ground potentials. Other grounding system design can limit ground potentials, while fail to limit ground currents.

Experimental Assessment of Grounding System Impacts on Ground Currents and Transient Overvoltage

In this article, experimental performance assessment and comparison are presented for solid, low impedance, high impedance, frequency-selective, and isolated grounding (IG) systems. The typical design of a grounding system (for low and medium voltage generation, transmission, and distribution systems) is based on selecting an impedance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\bar{Z}_{G}$</tex-math></inline-formula> ), which is used to connect the neutral point and the ground. The impedance <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\bar{Z}_{G}$</tex-math></inline-formula> is typically composed from a combination of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$R$</tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$L$</tex-math></inline-formula> , and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$C$</tex-math></inline-formula> elements. The combination type (series or parallel), along with the values of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$R$</tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$L$</tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$C$</tex-math></inline-formula> elements, allow estimating the possible effects of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\bar{Z}_{G}$</tex-math></inline-formula> on ground currents and potentials during ground faults. In this article, solid, low impedance, high impedance, frequency-selective, and IG systems are designed for a 35-kVA <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$3\phi$</tex-math></inline-formula> transformer and a 5-kVA <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$3\phi$</tex-math></inline-formula> synchronous generator, for purposes of assessing and comparing their effects on ground currents and potentials during ground faults. The laboratory transformer and generator are tested for line-to-ground and double line-to-ground faults with all designed grounding systems under different loading levels. Experimental results show that some grounding systems can effectively reduce ground currents, and other grounding systems can effectively reduce ground potentials. These capabilities and features can be used to achieve certain system and operation mandates, including ground capacity, maximum allowed overvoltage, and service continuity.

Evaluating the Impacts of Grounding Systems on Ground Currents and Transient Overvoltage

This article presents a performance comparison of the solid, low impedance, high impedance, frequency-selective, and isolated grounding systems. A grounding system (for any power system component) is designed as an impedance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\bar{Z}_{G}$</tex-math></inline-formula> ) that connects the neutral point to the ground. The impedance <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\bar{Z}_{G}$</tex-math></inline-formula> is constructed using a combination of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$R$</tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$L$</tex-math></inline-formula> , and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$C$</tex-math></inline-formula> elements. The values and combination type (series or parallel) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$R$</tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$L$</tex-math></inline-formula> , and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$C$</tex-math></inline-formula> determine the possible influence of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\bar{Z}_{G}$</tex-math></inline-formula> on ground currents and potentials. Each grounding system is related to a system voltages level, a specific combination of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$R$</tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$L$</tex-math></inline-formula> , and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$C$</tex-math></inline-formula> , and a range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$R$</tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$L$</tex-math></inline-formula> , and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$C$</tex-math></inline-formula> values. The solid, low impedance, high impedance, frequency-selective, and isolated grounding systems are designed for a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$3\phi$</tex-math></inline-formula> transformer and a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$3\phi$</tex-math></inline-formula> synchronous generator in order to compare their influences on ground currents and potentials during ground faults. The transformer and generator are tested for line-to-ground and double line-to-ground faults with all designed grounding systems. Test results show that some grounding systems can reduce ground currents only, while others can reduce ground potentials only. Such capabilities can be used to fulfill certain system and operation requirements (e.g., service continuity, ground capacity, etc.).

Study on a Real-time Work Assistance Method for Substation Based on Petri Net Model

Work assistance is one of the important means to improve work efficiency. This paper focuses on substation work and proposes a real-time work assistance method based on petri net model. The work assistance includes two aspects, termed as, workflow guidance and operation prompt. Particularly, the workflow constructed by the petri net includes sequence, inhibition, concurrency and conflict structures to declare the correlations between work steps. Further, different forms of operation prompts at each step are designed, considering real-time responses of workers including skip, replay, pause and restart. The effectiveness of the method is well validated by an application of the work assistance on measuring the grounding current of transformer core and clamp. It is demonstrated that the unified assistance method built by the petri net successfully instructs standardized working process, helps avoid potential risks, and provides flexible operation prompts in real time.

Electrochemical Sensor Applications of Nanoparticle Modified Carbon Paste Electrodes to Detect Various Neurotransmitters: A Review

Neurotransmitters are synapses transmitting messengers that are vital towards human wellness. Any abnormality in their behaviour can lead to huge psychological ailments such as Parkinson's, Alzheimer's, and Schizophrenia. During diagnosing and assessing mental diseases, it is critical to discover distinct measures of different neurotransmitters present. A combination of nanomaterials, proteins, and polymers are employed to create suitable detecting and sensing component systems. Electrochemical detection has been widely employed for in-vivo detection, with FSCV emerging as the most promising technology to date due to advantages such as high sensitivities, simple device structure, and facile downsizing. Excessive background noise and signal, restricted target selectivity, declination with time, and the device fouling are all issues that in-vivo electrochemical neurotransmitter indications encounter. Nanomaterials have sparked a tremendous focus in recent years owing to their diverse properties. CPEs are amongst the safest and most ecologically beneficial electrodes with a vast scope of applications due to their incredibly simple and rapid manufacturing method, lower back - ground current, relatively inexpensive, adaptability to numerous modifiers and modifying techniques, so on and so forth.

Application of comprehensive diagnosis technology in fault analysis of 35kV box transformer in wind farm

Using on-line monitoring means to monitor the state quantity of power equipment is the trend of equipment diagnosis and evaluation, but it is usually difficult to accurately judge the hidden dangers of equipment by using a single means. This paper puts forward the transformer comprehensive on-line monitoring technology, which can effectively identify the equipment faults through multi state quantity and long-time comprehensive analysis. The relevant achievements are applied to the fault analysis of 35kV box-type transformer in a wind farm. The qualitative classification of fault category is realized by integrating three state quantities: temperature, oil color spectrum and iron core grounding current; Through disassembly inspection, the effectiveness of the integrated on-line monitoring system is proved; The analysis of fault mechanism is realized by using finite element electromagnetic field calculation. The technology of transformer comprehensive diagnosis in this paper has a very important reference for the defect analysis of transformer equipment.

VIGIL: A Python tool for automatized probabilistic VolcanIc Gas dIspersion modeLling

Probabilistic volcanic hazard assessment is a standard methodology based on running a deterministic hazard quantification tool multiple times to explore the full range of uncertainty in the input parameters and boundary conditions, in order to probabilistically quantify the variability of outputs accounting for such uncertainties. Nowadays, different volcanic hazards are quantified by means of this approach. Among these, volcanic gas emission is particularly relevant given the threat posed to human health if concentrations and exposure times exceed certain thresholds. There are different types of gas emissions but two main scenarios can be recognized: hot buoyant gas emissions from fumaroles and the ground and dense gas emissions feeding density currents that can occur, e.g., in limnic eruptions. Simulation tools are available to model the evolution of critical gas concentrations over an area of interest. Moreover, in order to perform probabilistic hazard assessments of volcanic gases, simulations should account for the natural variability associated to aspects such as seasonal and daily wind conditions, localized or diffuse source locations, and gas fluxes. Here we present VIGIL (automatized probabilistic VolcanIc Gas dIspersion modeLling), a new Python tool designed for managing the entire simulation workflow involved in single and probabilistic applications of gas dispersion modelling. VIGIL is able to manage the whole process from meteorological data processing, needed to run gas dispersion in both the dilute and dense gas flow scenarios, to the post processing of models’ outputs. Two application examples are presented to show some of the modelling capabilities offered by VIGIL.

Ground Fault Directional Protection Method for HVDC Multiterminal Networks

The use of multiterminal HVdc networks is increasingly relevant in electrical power systems for transporting high powers over long distance. HVdc networks are not free from ground faults that represent the main cause of failures in electrical power systems. Their quick detection and actuation in an accurate and selective way are essential to avoid possible outages. For this reason, in this article, a new protection method that develops a directional evaluation of the ground current is presented. It is based on the measurement of the currents that circulate through the grounded shields at the endings of the HVdc cables, then only low voltage devices are required. Afterward, an analysis of the current polarity is performed. If the current in the shield circulates from the shield to ground, the fault takes place in the protected line and it should be disconnected as soon as possible. On the other hand, if the current goes from ground to the shield, there is a ground fault but not in the protected line. The proposed method has been validated by computer simulations and laboratory tests achieving satisfactory results.

Physical Reasons and Mitigation Strategies for Increased Lightnings in Bangladesh

Bangladesh lightning victims’ data spanning from 2007 to 2020 were analyzed to relate victims’ activities to lightning strikes under the current upstream water piracy-set heating whence to suggest some mitigation measures. The victims’ data from the online Bangladesh news media bd news 24.com were categorized in columns of places, times of occurrences, engagements of the victims, the numbers of the dead and the injured ones including animals and property losses and the online references. After the initial survey, the data were arranged cumulatively victims’ broad activity-, district-, month- and year-wise. The highlights are - people’s outdoor activities paid a heavier toll than the indoor ones; the riskiest district was Sunamganj; the deadliest month was May; and the worst year was 2018. In most of the cases victims fell in an aerial environment of increased electrical conductivity in the range 10-14 to 10-9 S/m due to a past, ongoing, or sudden shower when the aerial electric field became about 20 times larger than the natural one of 100 V/m to which added about 100 times more victims’ moist body conductivity, crop leaves’/thorns’ conductivity in the range of ∼ 0.3 to 0.9 S/m and the curvature-dependent induced electric field in victims’ working tools and/or ornaments of conductivity ∼ 10-7 to 10-8 S/m. Upstream water piracy caused regional warming and thence the increased lightning. As for the mitigation strategy, agricultural and cutting tools should be made of the poorly conducting carbon-steal. Field workers should work one behind the other maintaining the safe distance to avoid attacks from side flashes and the ground current. Females should wear beaded jewelries. Plates, glasses and cooking pots should be made of China clay and earthen wares. China clay or carbon-steel weights should be used in fishing nets. In any state of life, prostration on the ground gives the best protection. Houses should be protected by setting up lightning rods and making earthen tyle roofs. Date tree growing should be emphasized because of their lightning-favored sharply pointed thorns and leaves.

Improved Methodology for Conducted EMI Assessment of Wide Band-Gap Power Electronics

Electromagnetic interference (EMI) compliance is a requirement for most electronic systems and devices, including power electronics. The emergence of power electronic systems designed with wide band-gap (WBG) semiconductors poses new challenges for compliance. This is due to the high edge rates achievable with WBG devices, coupled with unintentional grounding paths, some of which are introduced galvanically with traditional EMI compliance instrumentation. This makes it beneficial to use isolated measurement methods in place of traditional ground-referenced EMI instruments. This approach is viable in comparison to traditional EMI compliance measurements and can significantly reduce circulating ground currents, which can greatly impact emissions measurement accuracy. This paper proposes a streamlined method for emissions evaluation of power electronics employing an oscilloscope, differential voltage probes, and post-processing software implemented in MATLAB. This proposed method eliminates unintended metrology ground coupling, yields faster full quasi-peak scan times, and minimizes risk of instrumentation damage.

Method of Locating Ground Fault in Low Resistance Grounding Distribution Network by Grounding Wire Current

Three-core cables are increasingly used in urban distribution networks. The shielding layer, armor layer of the three-core cable and the earthing electrode constitute the earth-electrode network. When a ground fault occurs, a regular ground wire current distribution is formed in the network. This paper analyzes the distribution law of ground current, and according to the distribution law, puts forward a kind of grounding fault location method of neutral point small resistance grounding grid, and finally designs and implements the grounding fault location system.

고속철도 신호기계실의 접지전류 진단 및 개선방안에 관한 연구

Through the construction of high-speed railways and the electrification projects, the railway ground was switched to the common grounding method with the individual(or independent) grounding method. The common grounding method can eliminate the potential difference between the equipment connected to the common grounding line, but the line is used for the path which the return current of a train flows. As a result, it has been confirmed that the impulse surge current invades the signal machine room through the ground wires of the track circuit cable that connects the track circuit devices in the field and the transmitter and receiver in the signal machine room. It was also confirmed that the grounding current that entered the signal machine room affects the grounding current of other equipment in the room. The grounding system inside the signal machine room consisted of the common grounding line buried along the track and a steel frame of the building structure, but the steel frame grounding of the building structure was used as a path for another impulse surge current to enter the room. The ground current that entered the signal machine room continued to adversely affect certain equipment in the machine room, causing the equipment to malfunction or eventually burn out. Therefore, in this paper, we analyze the state of the ground current in the signal machine room and present measures to prevent the impulse surge current from entering the room and suppress the generation of ground circulating current in the room.

The resistive ground fault of PWM voltage inverter in the EV charging station

During the direct touch of the inverter output voltage or with the ungrounded shield of the cable connecting the inverter to the motor or other type of load, the nonsinusoidal ground currents with a basic harmonic frequency between 1.5 and 16 kHz, flow via a human’s body. Here was proved that Residual Current Device (RCD) (I_{triangle n} = 30 mA) does not switch off the power supply when a ground current with a value of about some hundred milliamps occurs. Because RCDs do not disconnect the power supply, the touch on the inverter’s voltage is dangerous to health and life. For the authors, the RCD usage in the Voltage Frequency Converters (VFCs) is not a good engineer practice when high-frequency common-mode distortion currents flow through it. The paper presents tests of RCD operation in the event of a resistance ground fault (via human body) during EV battery charging where the PWM voltage inverter is connected to the external rectifier to provide DC charging battery voltage. Finally, the authors propose a method of eliminating common-mode (CM) current from short protection system by using a separate circuit in which the parasitic leakage current omits an RCD.

High Step-Up Converter Based on Non-Series Energy Transfer Structure for Renewable Power Applications.

In this paper, a high step-up boost converter with a non-isolated configuration is proposed. This configuration has a quadratic voltage gain, suitable for processing energy from alternative sources. It consists of two boost converters, including a transfer capacitor connected in a non-series power transfer structure between input and output. High power efficiencies are achieved with this arrangement. Additionally, the converter has a common ground and non-pulsating input current. Design conditions and power efficiency analysis are developed. Bilinear and linear models are derived for control purposes. Experimental verification with a laboratory prototype of 500 W is provided. The proposed configuration and similar quadratic configurations are compared experimentally using the same number of components to demonstrate the power efficiency improvement. The resulting power efficiency of the prototype was above 95% at nominal load.

Transient electromagnetic interferences between a power line and a pipeline due to a lightning discharge: An EMTP-based approach

This paper presents a transient electromagnetic interference study in a right-of-way shared between an 88 kV transmission line and a 14'' pipeline, with a complex approximation layout based on real project data, and analyses of the induced voltages along the interfered pipeline due to lightning discharges. A circuit model implementation based on the Alternative Transients Program (ATP) with frequency-dependent parameters is built to predict the transient inductive interference effects and ground currents caused by lightning surges. The model is validated using industry-standard software, and then leveraged to perform a detailed investigation of how lightning discharges with different characteristics and how distinct soil properties affect the propagation of the induced voltage wavefronts along the interfered pipeline. Results are expressed in terms of electromagnetic interference (EMI) zones within which the pipeline may be subjected to potentially hazardous voltages.

Differential and common-mode model-based controller for the double-dual buck transformerless inverter

This paper studies the double-dual DC-DC buck converter composed by two buck power stages in a double dual connection. This connection has been previously studied with the boost power stage in the well-known double dual boost converter. In contrast to the double dual boost, which can only be used as a dc-dc converter, the double dual buck can be used as an inverter. Furthermore, it has a non-pulsating voltage from the input terminals to the output terminals. This property is exploited to reduce the common-mode current, which is of special interest in transformer-less photovoltaic applications, among others. The study includes a model description of the system in terms of the differential and common-mode variables. A controller based on this model representation is proposed to alleviate the effects of the common-mode component of the inverter output voltage on the leakage ground current. The analysis shows that the double-dual buck based inverter in closed-loop with the proposed controller exhibits a considerably reduced leakage-ground current, i.e., an almost negligible common-mode current flowing through the ground-path. This natural benefit makes it an attractive option for applications such as grid-tied inverters for renewable energy systems and electric vehicles. An efficiency analysis is also provided considering a conventional modulation scheme. Finally, the system performance is evaluated in a 1 kW experimental setup.

Research on High Voltage Insulation Performance of Grounding Grid in Large Substation

The gap between overhead ground wire insulators is changed by external force or subjected to overvoltage, intermittent breakdown will occur, and continuous arcing will occur in severe cases. Real-time monitoring of the current change on the ground wire is of significance to the reliable operation of the overhead ground wire major. The article proposes a method to detect the surface contamination of composite insulators by measuring the ground current of the insulator. The ground current characteristics of composite insulators are studied, and the test loops of composite insulator ground current, body leakage current and surface leakage current are established respectively. The above three currents of the insulator were measured and compared and analysed. At the same time, the article focuses on the design and development of the hardware system of the DC grounding system insulation resistance tester with digital display and multi-channel inspection function based on the microcontroller.