Operation Of Distance Protection Research Articles

مرحل حماية المسافة وتأثير MOV على مناطق المرحل بإستخدام الماتلاب

Transmission lines are an important part of the power system. Transmission lines are used to transmit power and are prone to many breakdowns. Therefore, protection relays are used to protect transmission lines. The purpose of the protection system is to isolate the faulty part from the healthy part, because large currents generated by faults may cause damage to electrical equipment. One of the protection relays is the distance relay and is mainly used in the transmission line. Sometimes these relays are used for backup protection. Distance relays to determine impedance need voltage and current. Transmission lines are usually protected by a distance protection relay. Distance relays are of the high-speed class and can provide transmission lines. Protection distance relays that use impedance measurements to determine the presence and location of faults, are "fooled" by a series capacitor mounted on the line, when the presence or absence of a capacitor in the fault circuit is not known in advance. This is because the capacitor cancels or compensates for some of the line inductance, so the relay may sense a fault in its first region when the fault is actually in the second or third region of the protection. Similarly, Zone one fault can be considered reverse faults. In fact, this can cause some costly operating errors. Series compensated lines are protected from overvoltage by metal-oxide-varistors (MOVs) connected in parallel with the capacitor bank. The nonlinear characteristics of MOV devices add complexity to fault analysis and distance protection operation. During faults, the impedance of the line is modified by an equivalent impedance of the parallel MOV/capacitor circuit. Worth noting is a method that determines the L and C string values of the font and the MOV effect at the time of the error. This is done by analyzing the synchronous and sub-synchronous content of the voltage and current signals separately which provides enough information to calculate the L and C series of the line. In this paper, the transmission line impedance Z, Z(f) as a function of frequency has been calculated and plotted by the sequence characteristics and the studied MOV effect on line protection and fault location. Proper operation of the distance protection relay is also shown, and its effect on relay regions. Keywords: Distance protection relay, transmission line, zones of relay, MOV.

Моделирование особенностей работы дистанционной защиты резервных трансформаторов собственных нужд энергоблоков атомной станции при самозапуске мощных двигательных нагрузок

In the article, using computer modeling, an analysis of the operation of distance protection of backup transformers is carried out, providing alternative power supply for the own needs of a nuclear power plant through a backup busbar when disconnected from the power system. During the transition from the main network to the backup network, there is a short period of power off to the sections. At the same time, the powerful motor loads of the sections that have received power begin to operate in the freewheel braking mode. Then the reserve is automatically switched on, which can occur at a more or less favorable moment. At an unfavorable moment, self-starting may be electrically more severe than a short circuit on the busbar. When combining a new network from a backup auxiliary transformer and an autonomous circuit of running machines, transient processes of electromagnetic interaction between machines switching to generator mode and the new network arise. There are some optimal favorable moments for merging networks when it is advisable to carry out self-starting. Due to the complexity of the mathematical description with a high order system of equations and a large number of interaction objects, it is advisable to study these processes using computer modeling. A practical question, which is answered by the calculations and computer modeling, concerns the value of the distance protection setting for the backup transformer for auxiliary needs. Using the developed structural simulation model in MatLab, a series of experiments was carried out on the run-down and self-starting of auxiliary sections with their given composition and load. The range of self-start time corresponded to the operation of automatic switching on of the reserve sections by distance protection. Calculations and modeling show that the adopted setting can be adjusted, ensuring protection of a larger length of the busbar with possible options for connecting auxiliary sections to it. The model is supplemented with an add-on in the form of an external program for detailed processing and visualization of data obtained from oscilloscopes of the MatLab structural model.

Distance Protection Operation During Earth-Faults in High Voltage Networks with Cable Inserts.

Distance Protection Operation During Earth-Faults in High Voltage Networks with Cable Inserts.

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.

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.

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.

Evaluation of HVDC system's impact and quantification of synchronous compensation for distance protection

This paper presents a comprehensive evaluation of the HVDC system's impact on distance protection via systematic and realistic experimental tests, along with theoretical analysis of the root causes of the identified compromised protection performance. A methodology for quantifying the impact of Synchronous Compensation (SC) in supporting the distance protection operation is also established. In this work, the performance of two widely used physical distance protection relays have been evaluated using a realistic Hardware'In'the'Loop (HIL) testing environment, where a total of 480 cases have been tested under a wide range of system scenarios. Representative cases with compromised protection performance are selected, where issues of under/over'reach, faulted phase selection and impedance measurement are identified and analysed. Furthermore, a method for quantifying the required SC level to address the under/over'reach issues resulting from HVDC systems is presented. The method establishes the relationship between the angle difference of the two'end fault current infeeds of the protected line and the SC level. Based on this relationship, the required SC capacity to constrain the angle difference within a targeted limit can be estimated, which offers a useful tool for system operators to appropriately size the SC's capacity with additional valuable insights from the distance protection perspective.

Power-Based Concept for Current Injection by Inverter-Interfaced Distributed Generations during Transmission-Network Faults

This paper analyzes the influence of inverter-interfaced distributed generations’ (IIDGs) response during transmission network faults. The simplest and safest solution is to switch IIDGs off during network faults without impacting the network voltages. A more elaborate and efficient concept, required by national grid codes, is based on controlling the IIDGs’ currents, involving positive- and negative-sequence voltage measured at the connection point. In this way the magnitude and phase of the injected currents can be adjusted, although the generated power will depend on the actual line voltages at the connection point. Therefore, an improved concept is proposed to adjust IIDGs’ fault current injection through the required active and reactive power, employing the same voltage characteristics. The proposed, i.e., power-based concept, is more definite than the current-based one, since the required power will always be generated. The discussed concepts for the fault current injection by IIDGs were tested in different 110-kV networks with loop and radial topologies, and for different short-circuit capabilities of the aggregated network supply. Based on extensive numerical calculations, the power-based concept during transmission networks faults generates more reactive power compared to the current-based concept. However, the voltage support by IIDGs during transmission networks faults, regardless of the concept being used, is influenced mainly by the short-circuit capability of the aggregated network supply. As regards distance protection operation, it is influenced additionally by the network topology, i.e., in radial network topology, the remote relay’s operation can be delayed due to a largely seen impedance.

A novel instantaneous value based incremental quantities distance protection for AC transmission lines

Conventional distance protection elements are predominantly based on voltage and current phasors. As a result, those elements require the half-cycle/full-cycle time window to estimate the accurate voltage and current phasors. Using information in the transients of voltages and currents is a possible way to improve the distance protection operation speed. To break free of phasor limitations, this paper presents a novel incremental quantities distance protection algorithm based on instantaneous values of voltage and current. Firstly, the instantaneous voltage distribution along the AC transmission line is analysed. Then, the principle of the incremental quantities distance protection is presented. The influence of fault angle on the presented algorithm is also analysed and a solution is proposed to deal with the relative small fault angle conditions. Finally, an extensive simulation results based on PSCAD/EMTDC simulation verify the performance of the presented incremental quantities distance protection.

Analysis of the FACTS devices impact on the transmission line protection operation

The effect of the static synchronous compensator (STATCOM) on distance protection of a high-voltage transmission line is studied in this article. To carry out the research stated in the topic of the paper, an experimental scheme was developed, equipment was selected, the operation settings of the 3 stages of distance protection were calculated and quad characteristics were built on their basis. All listed above, as well as further experiments, were carried out by the real time digital simulator. The STATCOM model was integrated in the scheme and set next. A series of experiments was carried out: two-phase and three-phase short circuits in various nodes of the scheme with and without the compensator and in various connection nodes. After all the experiments were carried out, appropriate conclusions were made about the impact of FACTS devices on the operation of distance protection. Possible ways to solve detected problems were also proposed.

Assessment of wind power generation impact on the distance protection operation

In the article an experimental power system consisting of Russian equipment, as well as 220 kV power line distance protection, are simulated in the RTDS Simulator. The settings were calculated and the polygonal characteristics of distance protection were constructed. A sequential installation of wind turbines into various nodes of the power system was carried out and the correct operation of the protection was verified. As a result of the study, the impact of wind turbines on the distance protection when they are connected between the protection installation site and the point of the short circuit is revealed. The analysis of this impact is made. Possible ways to solve the identified problems are proposed, such as the use of adaptive distance protection, as well as numerous studies of the behaviour of wind turbines in various operating modes for further analysis and possible adjustment of guidelines for relay protection using new algorithms for calculating and configuring of distance protection. The results of this work can be used to improve and clarify the recommendations for tuning, produced by manufacturers of relay protection devices, which currently do not take into account the impact of wind power generation.

Enhancing Distance Protection of Long Transmission Lines Compensated With TCSC and Connected With Wind Power

Thyristor controlled series compensation (TCSC) is widely used in long transmission lines to mainly improve power transfer capability. However, TCSC produces complicated impedance that negatively affects distance protection operation. The wind energy generation system produces additional complexity to the distance protection performance due to the variation of wind speed and fault current level. This paper proposes an integrated scheme to change adaptively the settings of the Mho distance protection by shifting the relay characteristics considering the bad impacts of TCSC, wind power and fault resistance. The proposed scheme achieves its main stages starting from fault detection, until relay tripping decision procedure including online estimation for preliminary fault location, impedance of TCSC and fault resistance using limited communication requirements. By extensive MATLAB simulations, the performance of the proposed scheme is examined compared with the conventional Mho relays under different fault locations, fault inception angle, fault resistance, different wind power penetration, different wind speeds and different TCSC firing angles. The achieved results ensured that the proposed scheme improves significantly Mho distance relay operation and avoids under-reaching and over-reaching problems irrespective of the large shunt capacitance along the transmission line, and also without identifying the parameters of TCSC such as the capacitance, the inductance or the firing angle.

ФАКТОРНЫЙ АНАЛИЗ РАБОТЫ ДИСТАНЦИОННОЙ ЗАЩИТЫ ФИДЕРОВ КОНТАКТНОЙ СЕТИ В УСЛОВИЯХ ОРГАНИЗАЦИИ ТЯЖЕЛОВЕСНОГО ДВИЖЕНИЯ

The paper considers a connection of factors that affect the operation of distance protection of catenary feeders. The paper also presents an assessment of this effect on operation quality and selectivity of protection in conditions of operation of heavy-load trains with the weight up to 12,000 tons on example of measurements carried out on the Zabaikal Railway.

A New Distance Protection Method Considering TCSC-FCL Dynamic Impedance Characteristics

Ignoring the dynamic impedance characteristics of a thyristor-controlled series-capacitor-type fault current limiter (TCSC-FCL) may lead to maloperation/fail-to-trip or slow response of distance protection. To solve the above problem, the TCSC-FCL dynamic impedance analysis model was established. Taking the special operation mode of the TCSC-FCL into account, the time-varying characteristics of the TCSC-FCL during the whole process from the series compensation mode to the current-limiting mode were analyzed. Then, this paper proposed the function expression of dynamic impedance characteristics of the TCSC-FCL and put forward the distance protection setting strategy based on a dynamic offset impedance circle in order to eliminate the influence of TCSC-FCL dynamic impedance characteristics to the distance protection operation. By establishing a typical simulation model including the TCSC-FCL, the correctness of dynamic feature's analytic expression and the distance protection setting strategy is proved with extensive simulation results.

Adaptive setting of distance relay for MOV-protected series compensated line considering wind power

Series compensated lines are protected from overvoltage by metal-oxide-varistors (MOVs) connected in parallel with the capacitor bank. The nonlinear characteristics of MOV devices add complexity to fault analysis and distance protection operation. During faults, the impedance of the line is modified by an equivalent impedance of the parallel MOV/capacitor circuit, which affects the distance protection. The intermittent wind generation introduces additional complexity to the system performance and distance protection. Wind variation affects the fault current level and equivalent MOV/capacitor impedance during a fault, and hence the distance relay operation. This paper proposes an adaptive setting method for the mho relay distance protection of series compensated line considering effects of wind power variation and MOV operation. The distributed parameters of a transmission line are taken into account to avoid overreaching and underreaching of distance relays. A test system is simulated, and results demonstrate the ability of the proposed method to resetting the distance relays to adapt to various system conditions, including three wind generation and different compensation levels.

Series compensator 's influence on the distance protection operation

In the paper, the rules for finding formulas which describe the value of impedance measured by a distance protection due to the series compensator's influence are presented. The graphical interpretation of the formulas has been shown and the digital simulation-based verification of the formulas has been carried out. The modifications required in the protection settings under the standard operation of the series compensator as well as with the fault current limitation available have been defined. Influence of the shunt network failure on the operation of protections has been considered. Streszczenie. W artykule podano zasady wyznaczania wzorow opisujących wartośc pomierzonej impedancji przez zabezpieczenie odleglościowe na skutek oddzialywania kompensatora szeregowego. Podano interpretacje graficzną tych wzorow oraz dokonano ich weryfikacji poprzez symulacje cyfrową. Określono wymagane zmiany w nastawach zabezpieczen w przypadku standardowej pracy kompensatora szeregowego jak i z mozliwością ograniczania prądow zwarciowych. Rozwazono wplyw awarii ukladu bocznikującego na prace zabezpieczen. (Tytul : Wplyw kompensatora szeregowego na prace zabezpieczenia odleglościowego)

Ground Distance Relaying With Fault-Resistance Compensation for Unbalanced Systems

Fault resistance is a critical variable in distance relaying. If not considered due to underreaching phenomenon, it may cause the misoperation of ground distance relays for internal faults. Still, as a consequence of the overreaching phenomenon, the unbalanced nature of loads and asymmetry of lines can affect the distance protection operation efficiency. Mainly due to these aspects, there is low precision in protection zone limits of ground distance relays. In this paper, a new algorithm is proposed to increase the precision of these limits, improving efficiency in the distance protection process. The proposed method is based in phase coordinates and uses a fault resistance estimate to develop the trip decision procedure. The results show that the algorithm is suitable for online applications, and that it has an independent performance from the fault resistance magnitude, the fault location, and the line asymmetry.

An adaptive scheme to prevent undesirable distance protection operation during voltage instability

An adaptive scheme to prevent undesirable distance protection operation during voltage instability

An Adaptive Scheme to Prevent Undesirable Distance Protection Operation during Voltage Instability

An adaptive algorithm to prevent undesirable distance protection operations during voltage instability is proposed. The algorithm is based on mathematical logic blocks and uses the rate of change of voltage as an additional relay criteria to increase the relay security with respect to voltage instability. Studies are based on simulations using two different test systems: a 15-bus system developed by the authors and the Nordic32 system. The investigation shows that undesirable zone 3 distance relay operations can be the difference between a blackout and a recovering system during voltage instability. However, simulations have shown that the adaptive algorithm may save the system from a collapse. Although the algorithm prevents mal-trips due to voltage instability the reach of the distance relay will not be restricted.