输电线路计算功率法差动保护方法研究

文章针对传统方法在输电线路差动保护应用中输电线路差流值较大,起到的差动保护效果比较差的问题进行了研究。首先根据输电线路双端口U型等值电路特征,建立输电线路数学模型;然后利用计算功率法计算发生金属性接地故障和相间金属性短路故障时输电线路功率的差动量和制动量,并判断输电线路故障是区内故障还是区外故障;在此基础上设计了高定值差动保护和低定值差动保护两种保护策略,根据相应保护原则确定差动保护定值,完成输电线路计算功率法差动保护。经实验证明,应用设计方法后输电线路差流值小于传统方法,在保护输电线路稳定运行方面具有良好的应用效果,具有较好的可靠性和灵敏性。

空压机排气量与所需电机功率速算法

介绍空压机排气量与所需电机功率的两种计算方法

对化工厂与炼油厂使用的两种用电负荷计算方法的解读与分析

对于石油化工行业,用电负荷的计算对电气专业的设计至关重要,它是选择和校验变压器容量、开关设备、电力线路、仪器仪表以及继电保护整定的重要依据。用电负荷计算过大,将导致变压器容量、电气设备、导体截面选择过大,造成投资浪费;计算偏小会导致所选变压器容量不足,电气设备、电力线路运行时电能损耗超出预期,加速绝缘老化,甚至发生事故[1]。目前需要系数法在各相关行业中应用非常广泛,在石化行业中,绝大多数的化工装置的设计也一直在沿用。而在炼油工程的设计以中石化洛阳工程公司为代表,沿用的是《炼油厂用电负荷设计计算方法》(SHT 3116-2000)中的方法来计算。本文基于工作中对两种方法的应用及体会,作进一步的解读与比较,分析各自的优劣。

Throughput-efficient wireless system and blind detection via improved particle filtering

This paper introduces throughput-efficient wireless system based on an extension to binary phasemodulations,named extended binary phase shift keying(EBPSK),and the corresponding analysis ofpower spectra,especially the extension to channel capacity are given.Importantly,a novel sequential es-timation and detection approach for this EBPSK system is proposed.The basic idea is to design a proba-bilistic approximation method for the computation of the maximum a posterior distribution via particle fil-tering method(PF).Subsequently,a new important function in PF is presented,so that the performanceof the detector has a great improvement.Finally,computer simulation illustrates that EBPSK system hasvery high transmission rate,and also the good performance of the proposed PF detector is demonstrated.

The Analysis of Distillation Tray Column Efficiency by Fluid Dynamics and Mass Transfer Computation

It has long been found that the flow pattern of the liquid phase on distillation tray is of great importance on distillation process performance. But until now, there was very few published work on quantitative investigation of this subject. By combining the computational fluid dynamics (CFD) with the mass transfer equation, a theoretical model is proposed for predicting the details of velocity and concentration distributions as well as the tray efficiency of distillation tray column. Using the proposed model, four different cases corresponding to different assumptions of liquid and vapor flowing condition for a distillation tray column were investigated. In Case I, the distributions of velocity and concentration of the incoming liquid from the downcomer and the uprising vapor from the underneath tray spacing are uniform. In Case n, the distribution of the incoming liquid is non-uniform but the uprising vapor is uniform. In Case HI, the distribution of the incoming liquid is uniform but the uprising vapor is non-uniform. In Case IV, the distributions of both the incoming liquid and the uprising vapor are non-uniform. The details of velocity and concentration distributions on a multiple sieve tray distillation column in four different cases were simulated using the proposed model. It is found that the shape of the simulated concentration profiles of vapor and the liquid is quite different from case to case. The computed results also show that the tray efficiency is highly reduced by the maldistribution of velocity and concentration of the incoming liquid and uprising vapor. The tray efficiency for Case I is higher than Case Ⅱ or Case Ⅲ, and that for Case Ⅳ is the lowest. It also reveals that the accumulated effect of maldistribution becomes more pronounced when the number of column trays increased. The present study demonstrates that the use of computational method to predict the mass transfer efficiency for the tray column, especially for the large one, is feasible.

Design of area and power efficient Radix-4 DIT FFT butterfly unit using floating point fused arithmetic

In this work, power efficient butterfly unit based FFT architecture is presented. The butterfly unit is designed using floating-point fused arithmetic units. The fused arithmetic units include two-term dot product unit and add-subtract unit. In these arithmetic units, operations are performed over complex data values. A modified fused floating-point two-term dot product and an enhanced model for the Radix-4 FFT butterfly unit are proposed. The modified fused two-term dot product is designed using Radix-16 booth multiplier. Radix-16 booth multiplier will reduce the switching activities compared to Radix-8 booth multiplier in existing system and also will reduce the area required. The proposed architecture is implemented efficiently for Radix-4 decimation in time(DIT) FFT butterfly with the two floating-point fused arithmetic units. The proposed enhanced architecture is synthesized, implemented, placed and routed on a FPGA device using Xilinx ISE tool. It is observed that the Radix-4 DIT fused floating-point FFT butterfly requires 50.17% less space and 12.16% reduced power compared to the existing methods and the proposed enhanced model requires 49.82% less space on the FPGA device compared to the proposed design. Also, reduced power consumption is addressed by utilizing the reusability technique, which results in 11.42% of power reduction of the enhanced model compared to the proposed design.

A Practical Framework for Pricing of Backup Reserve and Wheeling in Power System

This paper presents a practical pricing model for backup reserve and wheeling, which attains a balanced strategy that ensures perceived benefits to both the buyer and the seller. The model and the associated computerized algorithm deal collectively with diverse issues, including： （1） fulfilling local firm real （and reactive） power demand requirements, （2） fulfilling local power reserve requirements, （3） buying firm real （and reactive） power from the grid, （4） buying reserve power from the grid, （5） exporting firm real （and reactive） power demand to remote load centers via the grid, （6） exporting reserve power via the grid, （7） wheeling of firm power demand to remote owned sites using the grid, and （8） wheeling reserve power to remote owned sites using grid. Practical implementation features of the computerized algorithms are also discussed with an illustrative case example.

Accelerated steered response power method for sound source localization via clustering search

The steered response power-phase transform (SRP-PHAT) sound source localization algorithm is robust in a real environment. However, the large computation complexity limits the practical application of SRP-PHAT. For a microphone array, each location corresponds to a set of time differences of arrival (TDOAs), and this paper collects them into a TDOA vector. Since the TDOA vectors in the adjacent regions are similar, we present a fast algorithm based on clustering search to reduce the computation complexity of SRP-PHAT. In the training stage, the K-means or Iterative Self-Organizing Data Analysis Technique (ISODATA) clustering algorithm is used to find the centroid in each cluster with similar TDOA vectors. In the procedure of sound localization, the optimal cluster is found by comparing the steered response powers (SRPs) of all centroids. The SRPs of all candidate locations in the optimal cluster are compared to localize the sound source. Experiments both in simulation environments and real environments have been performed to compare the localization accuracy and computational load of the proposed method with those of the conventional SRP-PHAT algorithm. The results show that the proposed method is able to reduce the computational load drastically and maintains almost the same localization accuracy and robustness as those of the conventional SRP-PHAT algorithm. The difference in localization performance brought by different clustering algorithms used in the training stage is trivial.