Distance Protection Research Articles

Delimiting radiation protection distance of underground uranium mining and metallurgy facilities: A case study in China

Delimiting radiation protection distance of uranium mining and metallurgy facilities is an important radiation protection approach to control the effective public dose caused by radon and radon progeny. Ventilation shafts are the main radon release paths of underground uranium mines. It is of great importance to research the diffusion regularities and influence range of the radon around the ventilation shaft. In this study, long-term and short-term radon accumulation monitoring approaches were adapted for onsite investigation. More than 520 sets of radon concentration were acquired. The survey results effectively revealed the distribution regularities of the radon concentration around the ventilation shaft with time, space, and working conditions. These results provide data for radiation protection in uranium mines. In addition, a radiation protection distance delimiting way was proposed for the investigated facility through effective public dose assessment.

Sand control effect of HDPE sandbreak nets with different porosity structure

Straw checkerboard sand barriers with a porous structure that consists of a pervious upper portion and a dense lower portion are widely used to achieve great sand control effect. Considering this, and resolving the serious earth surface undercutting problem after HDPE sandbreak net checkboard barriers setting, the authors used HDPE (high-density polyethylene) materials to prepare new sandbreak materials with a similar porous structure. Through wind tunnel simulations and field sand control monitoring, we compared the sand control effect of three HDPE sandbreak nets with different porosity structure. Compared to the sandbreak net with uniform porosity structure, the three types of HDPE sandbreak nets with different porosity structure had poorer effect on reducing sand transport rates, but had longer effective protection distance before sandbreak nets at low wind velocity conditions (<12 m/s), longer effective protection distance at high wind velocity (>14 m/s) and longer effective protection distance between sandbreak nets at all experimental wind velocity conditions. Wind and sand control effect characteristics of HDPE sandbreak nets with different porosity structure provide an ideal material on semi-buried checkerboard sand barriers for sand stabilization. By contrast, uniform-type sandbreak nets are used as materials on high upright sand fences for sand blocking. These HDPE sandbreak nets can be used to replace traditional sandbreak materials and have a very high potential for widespread and popular application in aeolian sand disaster control.

Research and analysis on suppression and influence of transformer direct current bias

DC bias generates a large DC component in the windings of the transformer in operation, thereby generating harmonics, causing vibration, noise, and overheating. In severe cases, it can cause damage to the transformer, which will affect the safe and stable operation of the AC system. This article takes the DC bias of the main transformer of a 220kV substation as an example, and uses the capacitance isolation method to suppress the DC bias. Due to the addition of capacitor equipment at the neutral point, the zero-sequence impedance of the main transformer and the change of the zero-sequence impedance of the power grid are changed, which has an impact on the zero-sequence (directional) current protection and ground distance protection. Through theoretical analysis and simulation research verification, for general 220kV substations, the capacitor DC isolation method (1.2Ω) can be used to suppress DC bias, which has a small impact on the relay protection and does not need to adjust the related protection settings.

Misoperation analysis and logic optimization of distance protection section I of polygonal impedance

Misoperation analysis and logic optimization of distance protection section I of polygonal impedance

Cost-Effective Solution of Remote Photoplethysmography Capable of Real-Time, Multi-Subject Monitoring with Social Distancing.

Recent advances in remote-photoplethysmography (rPPG) have enabled the measurement of heart rate (HR), oxygen saturation (SpO2), and blood pressure (BP) in a fully contactless manner. These techniques are increasingly applied clinically given a desire to minimize exposure to individuals with infectious symptoms. However, accurate rPPG estimation often leads to heavy loading in computation that either limits its real-time capacity or results in a costly setup. Additionally, acquiring rPPG while maintaining protective distance would require high resolution cameras to ensure adequate pixels coverage for the region of interest, increasing computational burden. Here, we propose a cost-effective platform capable of the real-time, continuous, multi-subject monitoring while maintaining social distancing. The platform is composed of a centralized computing unit and multiple low-cost wireless cameras. We demonstrate that the central computing unit is able to simultaneously handle continuous rPPG monitoring of five subjects with social distancing without compromising the frame rate and rPPG accuracy.

Investigations on vapor cloud explosion hazards and critical safe reserves of LPG tanks

To clarify vapor cloud explosion hazards in process industries and strengthen emergency treatment measures, a full-scale liquefied petroleum gas (LPG) tank model was established using computational fluid dynamics (CFD). Also, gas dispersion behavior and explosion hazards under different leakage characteristics were investigated and LPG safe reserves reasonably predicted. The results showed that heavy gas expansion near the ground mainly moved along gaps between structural congestions, while continuous large-scale congestion had significant enhancement effects on gas expansion and concentration accumulation. When an LPG cloud with nonuniform concentration ignited, the turbulent flame impacted the diluted explosive cloud at high speed, resulting in more serious consequences. When LPG leakage exceeded 300 s and the aperture greater than 10 mm, the hazard zone (Pc > 2 kPa) sharply increased and therefore considered to be the key factor in controlling explosion hazards. The LPG safe reserve varied little under low protection distance (Rp) and critical overpressure (Pc), but increased exponentially when Rp and Pc exceeded 200 m and 20 kPa, respectively. The present research conclusions provided a theoretical reference for emergency disposal, disaster assessment, and reserve safety design of LPG leakage and explosion accidents.

A novel directional element for transmission line connecting inverter-interfaced renewable energy power plant

The fault currents characteristics of inverter-interfaced renewable energy sources (IIRESs) such as direct-drive permanent magnetic synchronous generator and photovoltaic mainly include weak feed, the variety of source impedance and frequency deviation, which may lead to the false operation of distance protection for transmission line connecting inverter-interfaced renewable energy power plant (IIREPP). The R-L differential equation algorithm based time-domain distance protection is not affected by the fault characteristics of IIRES, but it is difficult to determine the fault direction when faults near the relay. In this paper, a directional element suitable for transmission line connecting IIREPP is proposed, and an improved time-domain distance protection composed of the directional element and the R-L differential equation algorithm based time-domain distance protection is proposed. The characteristics of fault currents of IIRES and traditional AC power grid are analyzed and summarized by deriving the analytical expressions of their fault currents in dq synchronous reference frame. The analysis results show that when the back of the relay is the IIRES and the AC power grid respectively, the change trends of the d-axis component of their fault currents are the same in a short time after faults occur in front of the relay, and the changes of q-axis component of their fault currents are obviously different. The directional element is proposed based on the characteristics of the fault currents on both sides of the transmission line connecting IIREPP. The simulation results verify effectiveness of the proposed protection scheme.

A novel distance protection scheme using single‐ended transient voltage based on generalized S transform

Concerning the distance protection steady-state over-reach or under-reach caused by the transition resistance, a novel distance protection scheme based on transient information is proposed. First, multiple fault features are extracted using the Generalized Stockwell Transform (GST), and a criterion for identifying low-resistance and high-resistance ground faults is constructed. Then, a GST coefficient matrix is established for the single-ended transient voltage of the line, the attenuation coefficient and delay coefficient are derived by the least-squares method and the beat phenomenon, and the transition resistance is calculated. On this basis, adjust the operation boundary in the +R axis direction of the operation zone according to the transition resistance value. Finally, test results on real-time digital simulation system (RTDS) demonstrate that the protection scheme operates reliably in different fault cases and is highly immune to fault resistance. Compared with the traditional distance protection scheme, this scheme performs better when the transition resistance is large.

Adaptive Distance Protection Based on the Analytical Model of Additional Impedance for Inverter-Interfaced Renewable Power Plants During Asymmetrical Faults

Due to limited amplitude and controlled phase of current supplied by inverter-interfaced renewable power plants (IIRPPs), the IIRPP-side distance protection of lines connected to IIRPPs fails to detect the fault location accurately, so it may malfunction. The composite sequence network of a line connected to an IIRPP during asymmetrical faults is analyzed, and an adaptive distance protection based on the analytical model of additional impedance is proposed in this study. Based on open circuit property of negative-sequence network at the IIRPP-side, the equivalent impedance of power grid and current flowing through fault point are calculated in real-time using local measurements, which are substituted into the analytical model of additional impedance to calculate fault location. In the case of negative-sequence reactive current injection from IIRPPs during asymmetrical faults, the error of calculating fault point current from local measurements is analyzed and corrected to ensure reliability of the proposed protection. The proposed protection alleviates the effect of fault resistance in a system with weak sources. In addition, the proposed protection can adapt to different grid codes (GCs), the operation mode change of the power grid, and the capacity change of the IIRPP. PSCAD/EMTDC test results verify the effectiveness of the proposed protection.

Protection Algorithms for Closed-Ring Grids With Distributed Generation

This paper proposes an approach to mitigate adverse effects of the fault management of closed/ring grids with high shares of distributed generation (DG). The approach refers to conventional distance protection relays in particular. The rising share of DG, especially in distribution systems, can lead to overloadings and intolerable voltages. Closed-ring structures increase the grid capacity for DG due to more balanced load and voltages profiles. However, malfunctions of protection relays may occur because fault locating and selective fault clearing can be disturbed. This paper presents a distance protection algorithm for feeder relays that complies with the requirements of closed/ring grids with inter/infeeds. The proposed current comparison method (CCM) bases on the comparison of negative/sequence currents. It needs no voltage measurement and remains unaffected from inter/infeeds and fault resistances. Additionally, for relays located at the ring coupler, where the ring can be opened, a coupling relay method (CRM) is proposed. It locates unsymmetrical faults in closed/ring grids with inter/infeeds and enables fast and selective opening of the ring. This helps maintaining reliable power supply for customers in closed rings. Finally, the paper presents a grading strategy reducing the average fault clearing time. Lab tests prove the capability of both proposed algorithms.

Statistical approach for detection of fault and stable and unstable power swings based on signal energy

Distance relays, as the main protection of the transmission lines, are prone to maloperation during power swings. Therefore, the detection of faults and stable and unstable power swings is vital in the proper operation of distance protection. The existence of a method that detects all of them with the same input and calculation can considerably reduce the computational burden of relays and accelerate the performance speed. Therefore, this paper proposes a new statistical approach for the detection of these disturbances based on the voltage energy signal as input. Three indices, including the proposed shape index (PSI) based on the kurtosis and skewness, the proposed dispersion index (PDI) based on the coefficient of variation, and the swing detection index (SDI), are presented to achieve this aim. The method is unaffected by current transformer saturation due to using only voltage signals. Moreover, the method has dynamic thresholds, whose equation coefficients are constant for any system with any voltage level. The method is tested on WSCC 9-bus and New England IEEE 39-bus test systems, considering challenging situations such as noise, high resistance faults, and different swing frequencies. The results of all cases of both test systems show that the method has 100% accuracy in the detection of faults with an average detection time of 0.69 ms in noise-free conditions, while, in noisy conditions, the fault detection accuracy and the average detection time are about 99.37%, and 1.75 ms, respectively. Furthermore, the detection accuracy of stable and unstable power swings is 100% with or without noise.

A distance protection approach for untransposed parallel transmission lines in case of phase-phase-ground inter-circuit faults

Distance relays’ phase and ground elements at either circuits of the parallel transmission lines undergo miscalculation of the correct fault impedance when facing inter-circuit faults. This paper proposes a distance protection approach for untransposed parallel lines in case of phase-phase-ground inter-circuit faults, which can also be served as the fault locator as its auxiliary function. It is a demanding task compared to that of transposed lines due to the mutual coupling between all six phases of the line circuits. Considering the intended faults with the fault arc and ground resistances, the line circuit model is analyzed on a time-domain basis, resulting an equation that is mathematically a linear combination of designated functions. This would provide a great chance of establishing an adaptive linear combiner with windowed inputs (W-Adaline) in consistence with the equation derived. The W-Adaline with its simple structure is capable of giving a fast and accurate estimation of the fault distance in an online manner, which is exploited for both the line distance protection and fault location. The proposed approach is readily implementable and is independent of the system configuration. It operates robustly in high-ground resistance, variable fault arc resistance and noisy conditions. Through extensive simulation studies in PSCAD/EMTDC, performance of the proposed approach would be investigated and verified in a variety of fault and system loading conditions.

Analysis of the Impact of a Modular SSSC on the Operation of Transmission Line Protection Relays using a Hardware-In-the-Loop Configuration

This paper evaluates the impact of a modular Static Synchronous Series Compensator (m-SSSC) on the operation of communication-assisted line distance and differential protection relays. The m-SSSC system incorporates an over-current protection feature to trigger the bypass mode of operation during grid faults. A case study is analyzed for a 220 kV transmission line and an m-SSSC with a reactive power rating of 80 MVAr per phase using a Hardware-In-the-Loop configuration. The obtained results show the impact of the m-SSSC system on the distance protection operation during some cases of high resistive faults. The differential protection operation was not affected by the mSSSC.

An adaptive time–frequency approach based secured back-up distance protection scheme for system stress conditions

Critical operating conditions of power system may lead to distance relay security issues. Distance relay back-up protection is offered with long reach setting and due to this under sudden change in voltage and current parameters during non-fault situations also considered as a fault by the protection function in an integrated network. The conventional technique fails to discriminate system stress conditions such as power swing, voltage instability and load encroachment from an actual symmetrical fault in the back-up zone (third zone (Z3)) of the distance relay. To mitigate this, a Modified Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (MCEEMDAN) technique is used to decompose the instantaneous power and to develop a reliable index. The most significant intrinsic mode function (IMFs) is extracted to estimate the energy as used as detection index. An adaptive statistical threshold selection process is developed to detect and discriminate all system stress conditions from symmetrical fault in the back-up zone of the distance relay. The proposed algorithm is a supervisory scheme for the back-up zone setting (Z3) of the distance relay. Simulation results for different stress conditions, presence of noise, sudden switching of load and symmetrical fault are presented to highlight the strength of the method.

An Incremental Quantities Distance Protection Using Park's Transformation

In this article, an incremental quantities distance protection using Park's transformation is proposed to increase the operation speed of distance protection. Based on the instantaneous voltage in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">abc</i> frame approximate linear distribution along the AC transmission lines, this article proves that instantaneous voltage in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> frame still satisfies the approximate linear distribution along the AC transmission line. Then, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis voltage components of fault point and setting point are used to determine the internal and external faults. In order to ensure that the presented distance protection can be applied to all fault types, a virtual three-phase system construction method is also presented. The fault point voltage construction method and low-pass filter design method are also discussed. Finally, a typical AC transmission system is developed in PSCAD/EMTDC to verify the performance of the proposed distance protection under different fault conditions. Simulation results indicate that the proposed incremental quantities distance protection has fast operation speed under internal metallic fault conditions and high security under external fault conditions.

Seeking Ways for Dealing with the Impacts of Sandstorms on the Railway Network in Saudi Arabia

Sandstorms that cause shifting dunes are a huge technical challenge in the development of the railway network in Saudi Arabia, and are known as one of the most concerning atmospheric aspects. In this case, the weather or climate change makes railways more problematic and costly in Saudi Arabia compared to other countries. The purpose of this article is to develop Saudi Arabia’s rail system in order to overcome environmental difficulties and obstacles such as wind–sand flow behavior and other impediments (e.g., camels) by constructing obstructions such as protective walls and dykes. Theoretical analysis is used to investigate the major components that influence wind velocity and density. The wind velocity in the majority of the locations in Saudi Arabia was employed as a control value in this study, which was based on the Saudi building standard SBC301. Sandstorm protection is best achieved by combining four different building solutions, including ditches, dykes, trees, and concrete barriers. The site parameters, such as sand particle size, air velocity, and the required downwind strip distance, all influence which of the four recommended approaches is optimal. From this study, it is concluded that the wind speed at the height of interest (barrier height) should be calculated using wind shear exponents ranging from 0.2 to 0.5 depending on the topography and surface roughness aspects. A new equation based on two parameters, Q1 and n, as a function of the wind shear exponent is suggested to predict the percentage of wind velocity increase (Vinc %) over the barriers. This study found that the protected distance between the downwind strip and the receiver might be anywhere between 20 and 40 m.

Complaints of Computer Vision Syndrome in Telemarketing Workers at Bank X in Jakarta

Introduction: Computer Vision Syndrome (CVS) or digital eye strain is a collection of eye problems related to vision. The telemarketing division in Bank X has 10 hours working time per day and 60 hours per week. This study aimed to determine CVS complaints among telemarketing workers and analyze the factors that caused CVS complaints in workers. Methods: The study used a cross-sectional study design, with a total sample of 53 workers. The variables studied were lighting intensity, monitor distance, age, refractive disorders, eye rest, and eye protection. The study used a lux meter to measure the light intensity and the Snellen chart to see eye refraction abnormalities. Results: The results determined that 77.4% of computer workers in Bank X Telemarketing division experienced CVS complaints while 22.6% did not experience CVS. The results of statistical tests showed that light intensity, monitor distance, refractive disorders, and eye rest were associated with CVS complaints, while age and eye protection equipment were not related to CVS complaints. Conclusion: Most telemarketing workers experienced CVS complaints caused by lighting intensity, monitor distance, refractive disorders, and eye rest.

A Straightforward Power Swing Detection Algorithm Using Rate of Impedance Angle Change

Mal-operation of distance protection relays during power swing (PS) condition can endanger the power system stability. Therefore, it is crucial to distinguish between short-circuit faults and PS by a power swing blocking (PSB) function to prevent undesired tripping of distance relay. This paper develops a novel and straightforward PSB method based on the rate of impedance angle change (RIAC). Not only can the proposed approach fairly discriminate both symmetrical and asymmetrical faults from PS, but also it can appropriately preserve protection scheme security during PS under single-pole tripping (SPT) on a transmission line. Furthermore, there is no need to perform extensive dynamic stability studies for setting the PSB function parameters. Unlike the rate of impedance change approaches utilized two blinders, the developed approach only needs an inner blinder. Thus, it can be used for networks running near their operational limits. The proposed method is evaluated through a modified IEEE-PSRC benchmark system in PSCAD/EMTC environment. The obtained results verify superior performance of the proposed method to traditional impedance rate of change method under different scenarios.

An Algorithm to Mitigate the Infeed Effect on Overreaching Distance Zones Settings

This paper revisits the analysis of the well-known infeed effect on transmission lines distance protection. A new adaptive algorithm to overcome this drawback is proposed, which requires solely impedance data and the operational status of power apparatus to perform overreaching distance zones settings. A comparison of the proposed strategy and the traditional one is performed. The obtained results demonstrate that the proposed settings ensure the correct operation of overreaching zones. Thereby, the backup coverage is improved significantly, besides avoiding distance zones overlapping between adjacent lines. It reveals the proposed strategy usefulness and value from the practical point of view, since it can be implemented with technology readily available on the market.

Power Swing and Fault Detection in the Presence of Wind Farms Using Generator Speed Zero-Crossing Moment

Nowadays, due to the entry of wind power plants into the power systems, which causes changes in the network parameters, power swing detection has become more important. Changes in the wind speed and noncontinuity of the wind power plants lead to changes in the power swing characteristic. Therefore, the impedance seen by the distance relay is changed, and so the maloperation of the relay during the stable power swing may occur. This paper proposes a new method to detect power fluctuations based on the synchronous generator speed while it is independent of the network parameters. Based on the proposed method, the generator speed at any moment does not pass through zero during the stable power swing. In contrast, it passes through zero by occurring fault types with high and low fault resistance, fault types during power swing, and an unstable power swing. Therefore, the method prevents maloperation of distance protection. It is worth noting that the proposed method is applicable for distance protection in any power system with and without wind power plants, such as in the distance protection of compensated transmission lines. The obtained results indicate that the proposed method detects power fluctuations in a short time.