Mine Power Systems Research Articles

Economic aspects of introducing pumped-storage hydroelectric power plants into the mine dewatering system for distributed power generation

The paper examines the pumped hydroelectric energy storage potential of mine dewatering system for power generation in a distributed power system. Based on the water inflows that can be used to fill the drainage basins, the following options for pumped-storage hydroelectric power plants (PSHPP) are considered: when groundwater is discharged from only one mine, one hydraulic turbine is installed on the horizon below the surface; with additional discharge of groundwater from neighboring mines – installation of two or four hydraulic turbines at the drainage stages closest to the surface. Comparison was made with grid only system. It is based on net present value (NPV) and levelized cost of energy (LCOE) criteria. Variable parameters were hydraulic turbine water flow and mine power consumption. Also, for a certain combination of parameters, the optimal mine power system was determined. The area of use of the PSHS is estimated. It was found that the smallest economic effect is achieved when the power generation of one hydraulic turbine is close to the power consumption. The area of expedient use of the PSHPP within the limits of parameter variation is 17.2%, 19.6% (base and peak costs of power). This is because power generation drops when the water flow decreases. It does not cover the needs of the mine and there is a power shortage. Thus, the mine power system autonomy is very low. With an increase in water inflow and the number of hydraulic turbines, first up to two and then up to four units, the area of expedient use of PSHPP increases to 51.5%, 55.9% and 50.6%, 72.8%, respectively. However, with low energy consumption and a low water flow, it is still rational to receive electricity from the grid. This is due to a sharp drop in the efficiency of hydraulic turbines and high costs for maintenance and repair of PSHPP equipment, which are not comparable to the cost of purchasing power. So it was noted that with the base cost of electricity and an increase in the number of hydro turbines from two to four, the area of conditions under which the use of PSHPP is justified even decreased by 0.9%. At peak cost, the area increases by 16.9%. The mine power system autonomy is not achieved. In general, the efficiency of using PSHPP for mine dewatering systems is high, but the feasibility of their use should be studied for specific conditions of use.

DDS‐based protocol‐compatible communication platform for mining power system

Currently, mine protectors have different communication protocols, which make them difficult to communicate with each other due to their heterogeneity. In order to solve the problem, this study proposes a structure based on data distribution service (DDS) between substation and different mine protectors, which unifies the different protocols for devices to DDS protocol. A DDS platform is built to transmit electrical parameters between devices using different protocols with appropriate quality of service strategies. The communication between IEC 60870-103 protocol and Modbus protocol is carried out on laptop and Raspberry Pi. The proposed DDS platform implements its normal communication between different protocols and the latency can meet the requirement of mine protectors. The experimental results verify that DDS can reduce the heterogeneity of mining power system.

Application of FACTS Devices in Power Supply Systems of Coal Mines

In this article, the authors discuss the use of FACTS devices in coal mine power systems. The problems of reactive power compensation and the disadvantages of regulatory and technical documentation regarding the use of modern reactive power compensation devices are considered. The main types of FACTS devices that can be used in coal mines are identified. The scientific publications in the field of application of FACTS devices in power supply systems of industrial enterprises are analyzed. The cost indicators of FACTS devices are considered and conclusions are drawn on the theoretical technical and economic efficiency of using FACTS devices in mine conditions.

Ground-directional solution to improve selectivity in underground mining power systems protection

The trend of expanding to larger underground mining systems has motivated increases in the voltage levels used for distribution and utilisation. Such increases have caused the industry to face complexities and challenges that are not common in lower voltage systems. For high voltage levels, the mining regulations require the use of shielded cables, with a resistive grounding method for the neutral. The occurrence of a phase-to-ground fault in a power system with this arrangement causes capacitive current flows from different locations to the point of failure, which reduces the selectivity of the ground overcurrent relays. The solution proposed here for this loss of selectivity is based on the ground-directional over-current algorithm. The methodology was detailed, validated, tested, and assessed using a software test model and subsequently in a real-time hardware-in-the-loop implementation in a playback testbed. The results showed an improvement in the protection performance in the context of different failure scenarios.

Power Quality Issues of Distorted and Weak Distribution Networks in Mining Industry: A Review

Mining is an important industry in many countries including Australia and plays a vital role in their economy. The industry heavily depends on electricity as it employs different types of electrical loads. Consequently, a stable and reliable supply of electricity is vital for running the production smoothly. In this review paper, electrical characteristics of mining power systems are described and common power quality and energy efficiency concerns in these systems are stated and classified. Different types of common power electronics topologies used in the industry are also studied and main requirements for reliable and robust operation of the system are categorized. A comprehensive case study to elaborate power quality challenges in mining distribution network is performed.

The development of a new integral control model based on the analysis of three complex systems in Serbia

The aim of this paper is to analyse the results of research carried out in the railway, mining, and electric power systems in Serbia and form a new integral control model. The three methodological procedures are applied. First, analytical-synthetic methodological approach breaks down complex technical system into three parts: bio-cybernetic system, "operator"; technical system, "technology"; and additional system, "working environment." Second, network planning method is used to analyse time, according to the critical path method. Third, fuzzy analytic hierarchy process determines the key research factors. General results of research are new integral control model, and new research areas and activities. The most prominent factors are: in "bio-cybernetic system"--operator's arm reach, body postures and movement sequences, operator's work, occurrence of stress, and occurrence of fatigue; in "technical system"--location and dimension of control desk, display panel, video display terminal, symbols on video display terminal, colours in control centres, and suitability of the keyboards; and in "supporting system"--illumination in control centres and relative humidity. Based on the analysis of factors and synthesis of results, the following recommendation are proposed: new control desk design; new display panel design; new design of the main and local lighting; new illumination and contrast characteristics, and environmental impact assessment. For research on a variety of complex technical systems, new integral control model can be applied, with corresponding extensions.

Best Practices for Implementing High-Resistance Grounding in Mine Power Systems

Proper implementation of high-resistance grounding of mine power systems can reduce arc flash and shock hazards by limiting ground fault current while also permitting reliable detection and clearing of the fault. IEEE Standard 142 defines a high resistance grounded system as one with a purposely inserted resistance that limits ground-fault current to levels such that the fault current (usually thought of as less than 10 A) can flow for an extended time without exacerbating damage. However, the per-phase zero-sequence resistance of the system should not exceed the distributed per-phase capacitive reactance of the system; otherwise, the system will be prone to transient overvoltages and relay selectivity problems. Recent research has shown that in practice, the zero-sequence resistance may be considerably larger than the system capacitive reactance, thereby violating the definition of a high-resistance grounded system. This paper outlines procedures for proper sizing of the neutral grounding resistor considering the distributed system capacitance. The paper begins with a discussion of the problems caused by distributed capacitance in high-resistance-grounded mine power systems. Subsequently, procedures for determining system capacitance, sizing the neutral grounding resistor, and establishing relay pickup settings are given. These procedures are straightforward to apply and do not require computer modeling for implementation. Numerical examples of the procedure applied to a high-voltage longwall system and also an underground mine distribution system are provided.

Enhancement of Optimal Scheduling and Fuel Cost Minimization using Flexible Genetic Algorithm

This paper aims at providing a solution to optimum power flow (OPF) in considered power systems by using a flexible genetic algorithm (GA) model. The proposed approach finds the optimal setting of OPF control variables which include generator active output, generator bus voltages, transformer tap-setting and shunt devices with the objective function of minimizing the fuel cost. The proposed GA is modeled to be flexible for implementation to any power systems with the given system line, bus data, generator fuel cost parameter and forecasted load demand. The GA model has been analyzed and tested on the standard benchmark IEEE 30-bus system and two real time power systems which are an industrial park power system and a gold-copper mining power system both located in Indonesia. The results obtained outperform other approaches which are recently applied to the IEEE 30-bus system with the same control variable maximum & minimum limits and system data. Better results are also found when compared against the configurations used in the two real power systems. These superior results are achieved due to the robust and reliable algorithm of the proposed GA which utilizes the differential evaluation. General Terms Optimal power flow, Fuel cost minimization, Genetic algorithm, Differential Evaluation.

Research on Visualized Protective Relaying Setting Software for Coal Mine Power System

According to the special requirement of protective relaying setting in coal mine power system, the research and development of a visualized protective relaying setting software is described in this paper. Firstly, software architectural and its functional module is defined to meet special needs, then a novel setting method based on ‘triggered by setting condition’ and action simulation method based on setting value are proposed. Object-oriented and visualized programming means ensure its users can easily and directly carry out the setting calculation of protective relaying and simulate the protective action. The application and the achievements of good effects at last ensure its rationality.

The Solution for Malfunction of the Leakage Protection System Caused by Mine-Used Converter

The leakage protection system usually trends to make a misjudgment and tripping in normal operation after applying the converter in the coal mine power system. This seriously affects the safety in coal production. Based on the research of the structure and working principle of the converter, it has obtained the definite reason for the converter interfere the leakage protection system. It is the higher harmonics and pulses that generate the zero sequence current through the ground capacitance. Combined with the actual situation in coal mine, it has proposed two corresponding solutions: one is adding the isolation transformer in the output lines of the converter; another is modifying criterion of the leakage protection system. Both methods have their own characteristics, and have verified the feasibility of the methods through the MATLAB simulation.

Research of Integrated Distribution Scheme of Reactive Power Compensation Based on SVG for Coal Mine Power System

Aiming at the situation of the low power factor of coal mine power system, this paper puts forward an integrated distribution scheme of reactive power compensation based on SVG. In this paper, not only the disadvantageous influences of reactive power of coal mine power network are analyzed, but also the working principle and advantages of SVG are introduced. This paper proposes a distribution scheme of three-level reactive power compensation, which is to compensate in the sides of high voltage, high-low voltage power distribution and the long-distance high-power loads. According to the results of theoretical calculation and MATLAB simulation, the scheme can reduce the power loss and increase the power factor, so the power quality of coal mine can be improved.

The Research of wxWidgets Applied to Power System Graphics Software Development

This article discusses the problems existing in power system graphics software, and analyze wxWidgetss characteristics like cross-platform, local perception, face to objects and other features. The validation based on the wxWidgets development can make up for the graphics software shortcomings, providing new ideas for the development of future coal mine power system graphics software.

Safety Analysis of Trailing Cables Used on 2400-V Continuous Mining Machines

An analysis was performed to determine whether an increased shock hazard occurs with 2400-V continuous-miner trailing cables, as compared with those used with existing low and medium-voltage systems. (It should be noted that the Code of Federal Regulations defines low-voltage, medium-voltage, and high-voltage for mine power systems as 0 - 660 V, 661 - 1000 V, and greater than 1000 V, respectively). The study assumed that Mine Safety and Health Administration's Proposed Rule for High-Voltage Continuous Mining Machines was implemented with the exception of the special cable- handling requirements. Two major differences between the high-voltage proposed rule and existing low and medium-voltage regulations that are relevant to this study deal with ground-fault protection and include: (1) The maximum ground-fault current of the 2400-V system must be limited to 0.5 A, while the low and medium- voltage systems typically use a limit of 15 A, and (2) The maximum ground-fault pickup of the 2400-V system must be set at 0.125 A with a maximum time delay of 0.05 s; whereas, low and medium-voltage systems require an instantaneous pickup set at, or below, 40% of the maximum ground-fault current (6 A for 15-A systems). Results of the study show that the 2400-V trailing cable, in conjunction with the strict ground-fault protection requirements and enhanced cable construction, provide a higher level of safety compared with the trailing cables used on low and medium-voltage continuous miners.

Fault Line Selection with Parallel Supply Lines in Mine Power Systems

In mine power systems, false operation and failure operation of relays in parallel supply lines often take place when single phase grounding fault occurs. A novel method based on phase-to-phase current difference is proposed as line selection criterion in this paper. The method builds on that the phase-to-phase current difference based on fault phase in fault line is equal to the grounding fault current while the phase-to-phase current difference based on fault phase in sound lines is equal to zero. Thus the fault line was selected by the biggest phase-to-phase current difference of the lines. The simulation results using PSCAD and experiment results show that the method has a high accuracy and a great ability of anti-disturbance. It is quite effective when single-phase-to-earth fault occurs in one of the parallel supply lines. It also applies to any distribution system with different grounding patterns and won’t be affected by the value of grounding resistance or the degree of fault phase.

Based on OMAP Platform to Build the Distribution System Network of Relay Protection Devices in Coal Power

This article has carried on the analysis in view of the coal mine old communication network and the relay protection installment existence's question, Proposed based on the OMAP platform to build a coal mine power system relay protection program, elaborated the OMAP platform coal mine relay protection principle, To design this equipment's schematic diagram, and has carried on the performance introduction to this equipment's main hardware constitution, this paper has developed the data acquisition function software flow chart, it provided the basis for the development new coal mine distribution network relay protection installment.

Study on the Intelligent Current Protection for Mining Power System

The overcurrent fault characters in underground cable distribution networks is analyzed, the symmetry current fault protection based on phase-sensitive detection, the asymmetrical current fault protection based on negative sequence current detection and the overload current fault protection based on the amplitude current are designed. The protection system was tested and the result shows that signal can accurately reflect the type of fault and fault parameters. It has been realized intelligent current protection through automatic identify fault type by PLC and has been applied to mine flameproof and intrinsically safety load control centre. Practice shows that the mine's intelligent current protection system is realiable and will be of great applied value in mining industry.

Industries and lung cancer: A population-based case-control study in British Columbia

An investigation was conducted to identify high-risk industries for histological subtypes of lung cancer based on a large population-based case-control study in British Columbia, Canada. Occupational histories and information on smoking and relevant covariates were collected from 14,755 male incident cancer cases. Industrial risk factors for 2998 lung cancer cases, including histological subtypes were assessed by logistic regression using other cancer cases, excluding smoking-related cancers, as controls. An excess risk of lung cancer was found among workers in mining, metal manufacturing, and electric power systems for all histological-subtypes, and construction, water transport, health services for specific histological subtypes. Industrial associations that are unique to histological subtypes of lung cancer were identified. Future research needs to focus on confirming these histological associations, and identifying the risk from key exposures found within these industries (e.g. medical radiation, electromagnetic fields, and cooking fumes).

Ground-Fault Feeder Detection With Fault-Current and Fault-Resistance Measurement in Mine Power Systems

Many mine power systems operate with a floating neutral or are high-resistance grounded, and earth fault current is no more than a few tens of amperes. Traditional earth-fault-detection methods based on zero-sequence current have poor sensitivity in this case. For improvement, a fault-detection scheme with fault-current and fault-resistance measurement is presented in this paper, which is capable of detecting high-impedance ground faults. The scheme has been verified by electromagnetic-transient-program simulation, and a fault-detection prototype has been developed and tested in the laboratory. Results show that the scheme has high sensitivity and robustness.

Detrimental Effects of Capacitance on High-Resistance-Grounded Mine Distribution Systems

Modern underground coal mines can be very large, having a total connected load in excess of 15,000 hp. These mines generally have many miles of high-power conveyor belts and IS or more miles of high-voltage power cables at distribution voltages of 12.47, 13.2, 13.8, or 14.4 kV. The shielded cables used in mine power distribution systems have a significant level of capacitance, on the order of 110 pF per ft. This level of capacitance, in an extensive power distribution system at today's voltage levels, can cause significant charging currents during a ground fault. This paper addresses the potential detrimental effects of capacitance charging currents during line-to-ground faults in mine power distribution systems. A representative mine power system is modeled and simulations with faults at various locations are conducted to evaluate the effects of this capacitance on the level of fault current and relay selectivity. The paper also includes results of capacitance measurements made on mine power feeder cables used to validate the simulation model.

On-site safety evaluation for earth fault in mining power systems

Many mining power systems utilize ineffectively grounded sources to restrict the residual current of single-phase earth fault in order to reduce outage and shock hazard. In practice, with the system expansion, topology changing, and insulation aging, the potential residual current and zero-sequence voltage for earth fault vary dynamically and some arcing earth faults can easily cause over-voltage and induce multiple faults. In order to improve the system safety, on-site condition monitoring, safety evaluation, and preventive maintenance for earth fault are proposed in this paper. Some techniques for online parameters measurement based on resonance-measurement principle are presented. Power system operation states are classified into normal secure state, alert state, incipient fault state, and fault state. Some security enhancement methods (preventive action and remedial action) for each state are implemented. The prototype for safety evaluation has been developed and installed in industry power systems for several years.