Power swing evoked by sudden changes like faults or switching operations will become more and more important for protective relaying, due to the growing load flow in electrical power networks. Unwanted trips of the di...Power swing evoked by sudden changes like faults or switching operations will become more and more important for protective relaying, due to the growing load flow in electrical power networks. Unwanted trips of the distance protection function must be avoided to prevent cascading effects and blackouts in the network. Selective out-of-step-tripping is required to stop unstable power swing and to prevent damage to affected generators. Therefore a reliable method for detection of power swing is presented, which requires no settings for operation. Power swing can be detected from 0.1 Hz up to 10 Hz swing frequency, also during open pole condition and during asymmetrical operation. A blocking logic prevents unselective trips by the distance protection. However, faults that occur during a power swing must be detected and cleared with a high degree of selectivity and dependability. For unstable power swing a flexible out of step tripping function will be proposed. The coordination of power swing detection, distance protection and out of step protection provides a reliable system protection.展开更多
Distance relays are prone to symmetrical power swing phenomenon.To mitigate this issue,a dynamic threshold-supported algorithm is proposed.A single logic is not supposed to be secure for all cases.Thus,a supervisory a...Distance relays are prone to symmetrical power swing phenomenon.To mitigate this issue,a dynamic threshold-supported algorithm is proposed.A single logic is not supposed to be secure for all cases.Thus,a supervisory algorithm,as proposed in this study,can aid in the improvement of the immunity of the relay during swing cases and be sensitive to symmetrical faults.In the developed stages,a three-phase power signal was used and processed in two different steps:(i)extraction of the effective intrinsic mode function(IMF)selected from the Kurtosis analysis using the wavelet synchro-squeezing transform,and(ii)estimation of the average Euclidean distance index using the absolute values of the decomposed IMF’s.The adaptive threshold facilitated resistance to swing situations.At the onset of a symmetrical fault,the proposed algorithm efficiently discriminated among events using a dynamic threshold.The IEEE 39-bus test system and Indian Eastern Power Grid networks were modelled using PSCAD software,and cases were generated to test the efficacy of the method.The impact of the proposed method on a large-scale wind farm was also evaluated.A comparative analysis with other existing methods revealed the security and dependability of the proposed method.展开更多
The main purpose of power swing blocking is to distinguish faults from power swings.However,the faults occur during a power swing should be detected and cleared promptly.This paper proposes an adaptive concentric powe...The main purpose of power swing blocking is to distinguish faults from power swings.However,the faults occur during a power swing should be detected and cleared promptly.This paper proposes an adaptive concentric power swing blocker(PSB)to overcome incapability of traditional concentric PSB in detecting symmetrical fault during power swing.Based on proposed method,two pairs of concentric characteristics are anticipated which the first one is placed in a stationary position(outer of zone3)but the position of the second pair is adjustable.In order to find the position of the second pair of characteristic,Static Phasor Estimation Error(SPEE)of current signal is utilized in this paper.The proposed method detects the abrupt change in SPEE and puts the second pair of characteristic in location of impedance trajectory correspondingly.Second concentric characteristic records travelling time of impedance trajectory between outer and inner zones and compares to threshold value to detect symmetrical fault during power swing.If recorded time is lower than threshold,three-phase fault is detected during power swing.Intensive studies have been performed and the merit of the method is demonstrated by some test signals simulations.展开更多
Increasing power demand,penetration of renew-ables,and limitations of necessary grid expansion are proffering new challenges to existing power system protection and control strategies.However,with the advancement in i...Increasing power demand,penetration of renew-ables,and limitations of necessary grid expansion are proffering new challenges to existing power system protection and control strategies.However,with the advancement in intelligent elec-tronic devices and relaying technology,fast,accurate and reliable protection schemes can be developed for smart power systems.In this paper,a new protection scheme based on admittance and power change has been proposed with dual-use line relays to detect symmetrical/asymmetrical faults in power systems.A large number of fault environments have been simulated by varying fault distances from relay location,fault resistance,and power angle in single machine infinite bus and WSCC 9-bus systems.Some crucial decisive fault scenarios e.g.close in/far end faults,faults in series compensated line,faults during asymmetrical swings,switching ON/OFF large loads,single and multi-modal swings have also been verified for the proposed index.In this paper,for the first time,detection of faults during power swings have been examined and verified in the presence of wind farms.The simulation results show the proficiency of the proposed algorithm for detecting faults in the presence or absence of power swings.展开更多
Power swing is an undesirable variation in power flow. This can be caused by large disturbances in demand load, switching, disconnection or reclosing lines. This phenomenon may enter the zones of distance relays and c...Power swing is an undesirable variation in power flow. This can be caused by large disturbances in demand load, switching, disconnection or reclosing lines. This phenomenon may enter the zones of distance relays and cause relay malfunction leading to the disconnection of healthy lines and undermining network reliability. Accordingly, this paper presents a new power swing detection method based on the prediction of current signal with a GMDH (Group Method of Data Handling) artificial neural network. The main advantage of the proposed method over its counterparts is the immunity to noise effect in signals. In addition, the proposed method can detect stable, unstable, and multi-mode power swings and is capable of distinguishing them from the variety of permanent faults occurring simultaneously. The method is tested for different types of power swings and simultaneous faults using DIgSILENT and MATLAB, and compared with some latest power swing detection methods. The results demonstrate the superiority of the proposed method in terms of response time, the ability to detect power swings of different varieties, and the ability to detect different faults that may occur simultaneously with power swings.展开更多
Interconnect power and repeater area are important in the interconnect optimization of nanometer scale integrated circuits. Based on the RLC interconnect delay model, by wire sizing, wire spacing arid adopting low-swi...Interconnect power and repeater area are important in the interconnect optimization of nanometer scale integrated circuits. Based on the RLC interconnect delay model, by wire sizing, wire spacing arid adopting low-swing interconnect technology, this paper proposed a power-area optimization model considering delay and bandwidth constraints simultaneously. The optimized model is verified based on 65-am and 90-nm complementary metal-oxide semiconductor （CMOS） interconnect parameters. The verified results show that averages of 36% of interconnect power and 26% of repeater area can be saved under 65-nm CMOS process. The proposed model is especially suitable for the computer-aided design of nanometer scale systems-on-chip.展开更多
文摘Power swing evoked by sudden changes like faults or switching operations will become more and more important for protective relaying, due to the growing load flow in electrical power networks. Unwanted trips of the distance protection function must be avoided to prevent cascading effects and blackouts in the network. Selective out-of-step-tripping is required to stop unstable power swing and to prevent damage to affected generators. Therefore a reliable method for detection of power swing is presented, which requires no settings for operation. Power swing can be detected from 0.1 Hz up to 10 Hz swing frequency, also during open pole condition and during asymmetrical operation. A blocking logic prevents unselective trips by the distance protection. However, faults that occur during a power swing must be detected and cleared with a high degree of selectivity and dependability. For unstable power swing a flexible out of step tripping function will be proposed. The coordination of power swing detection, distance protection and out of step protection provides a reliable system protection.
文摘Distance relays are prone to symmetrical power swing phenomenon.To mitigate this issue,a dynamic threshold-supported algorithm is proposed.A single logic is not supposed to be secure for all cases.Thus,a supervisory algorithm,as proposed in this study,can aid in the improvement of the immunity of the relay during swing cases and be sensitive to symmetrical faults.In the developed stages,a three-phase power signal was used and processed in two different steps:(i)extraction of the effective intrinsic mode function(IMF)selected from the Kurtosis analysis using the wavelet synchro-squeezing transform,and(ii)estimation of the average Euclidean distance index using the absolute values of the decomposed IMF’s.The adaptive threshold facilitated resistance to swing situations.At the onset of a symmetrical fault,the proposed algorithm efficiently discriminated among events using a dynamic threshold.The IEEE 39-bus test system and Indian Eastern Power Grid networks were modelled using PSCAD software,and cases were generated to test the efficacy of the method.The impact of the proposed method on a large-scale wind farm was also evaluated.A comparative analysis with other existing methods revealed the security and dependability of the proposed method.
文摘The main purpose of power swing blocking is to distinguish faults from power swings.However,the faults occur during a power swing should be detected and cleared promptly.This paper proposes an adaptive concentric power swing blocker(PSB)to overcome incapability of traditional concentric PSB in detecting symmetrical fault during power swing.Based on proposed method,two pairs of concentric characteristics are anticipated which the first one is placed in a stationary position(outer of zone3)but the position of the second pair is adjustable.In order to find the position of the second pair of characteristic,Static Phasor Estimation Error(SPEE)of current signal is utilized in this paper.The proposed method detects the abrupt change in SPEE and puts the second pair of characteristic in location of impedance trajectory correspondingly.Second concentric characteristic records travelling time of impedance trajectory between outer and inner zones and compares to threshold value to detect symmetrical fault during power swing.If recorded time is lower than threshold,three-phase fault is detected during power swing.Intensive studies have been performed and the merit of the method is demonstrated by some test signals simulations.
文摘Increasing power demand,penetration of renew-ables,and limitations of necessary grid expansion are proffering new challenges to existing power system protection and control strategies.However,with the advancement in intelligent elec-tronic devices and relaying technology,fast,accurate and reliable protection schemes can be developed for smart power systems.In this paper,a new protection scheme based on admittance and power change has been proposed with dual-use line relays to detect symmetrical/asymmetrical faults in power systems.A large number of fault environments have been simulated by varying fault distances from relay location,fault resistance,and power angle in single machine infinite bus and WSCC 9-bus systems.Some crucial decisive fault scenarios e.g.close in/far end faults,faults in series compensated line,faults during asymmetrical swings,switching ON/OFF large loads,single and multi-modal swings have also been verified for the proposed index.In this paper,for the first time,detection of faults during power swings have been examined and verified in the presence of wind farms.The simulation results show the proficiency of the proposed algorithm for detecting faults in the presence or absence of power swings.
文摘Power swing is an undesirable variation in power flow. This can be caused by large disturbances in demand load, switching, disconnection or reclosing lines. This phenomenon may enter the zones of distance relays and cause relay malfunction leading to the disconnection of healthy lines and undermining network reliability. Accordingly, this paper presents a new power swing detection method based on the prediction of current signal with a GMDH (Group Method of Data Handling) artificial neural network. The main advantage of the proposed method over its counterparts is the immunity to noise effect in signals. In addition, the proposed method can detect stable, unstable, and multi-mode power swings and is capable of distinguishing them from the variety of permanent faults occurring simultaneously. The method is tested for different types of power swings and simultaneous faults using DIgSILENT and MATLAB, and compared with some latest power swing detection methods. The results demonstrate the superiority of the proposed method in terms of response time, the ability to detect power swings of different varieties, and the ability to detect different faults that may occur simultaneously with power swings.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60725415 and 60971066)the National High-Tech Program of China (Grant Nos. 2009AA01Z258 and 2009AA01Z260)the National Science & Technology Important Project of China (Grant No. 2009ZX01034-002-001-005)
文摘Interconnect power and repeater area are important in the interconnect optimization of nanometer scale integrated circuits. Based on the RLC interconnect delay model, by wire sizing, wire spacing arid adopting low-swing interconnect technology, this paper proposed a power-area optimization model considering delay and bandwidth constraints simultaneously. The optimized model is verified based on 65-am and 90-nm complementary metal-oxide semiconductor （CMOS） interconnect parameters. The verified results show that averages of 36% of interconnect power and 26% of repeater area can be saved under 65-nm CMOS process. The proposed model is especially suitable for the computer-aided design of nanometer scale systems-on-chip.
