Table of Content

25 August 2020, Volume 40 Issue 4

  

Researches and Tests

Research and Implementation of Synchronous Space Vector Modulation Algorithm for Photovoltaic Direct Drive Air Conditioner

LIN Baowei, YANG Maotao, ZENG Wenwei, ZHAO Zhigang, LIN Jing

2020, 40(4):  1-6.  doi:10.3969/j.issn.1008-0198.2020.04.001

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This paper studies the synchronous space vector modulation (SVPWM) algorithm of photovoltaic direct-drive air conditioners, and gives the implementation scheme of synchronous modulation. And the effectiveness of the synchronous modulation scheme is verified by simulation.Finally, by applying SVPWM modulation in the vector control system of permanent magnet synchronous motor, the stability of the modulation method in closed-loop control with low switching frequency is verified.

Research on Demand Side Response for Large Industrial Load in Hunan Province

WU Yefan, CHEN Jin, ZHANG Mi, LIU Haotian, DENG Kai, LI Dawei

2020, 40(4):  7-12.  doi:10.3969/j.issn.1008-0198.2020.04.002

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Regarding the problem of the time difference and seasonal differences of power demand in Hunan province in recent years, this article will combine the latest domestic and foreign latest research results demand response theory to investigate and research the large industrial load with huge power consumption. Based on the division of major industrial sectors in Hunan province, the work of each industry category and the ability are investigated to implement demand response. Then the theory and model are optimized from the aspects of peak and valley division and real-time electricity price. Finally, the optimization results of real-time data of Hunan province's large industry are given by means of origin simulation software.

Simulation of Unstable High-resistance Ground Fault Based on RTDS Platform

XU Hao, YIN Chaoyong, DONG Guoqin, WANG Shannuo, XU Liqiang, OUYANG Fan, ZHU Weijun

2020, 40(4):  13-18.  doi:10.3969/j.issn.1008-0198.2020.04.003

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RTDS is an effective simulation method for mining and processing the hidden criterion of protection device. Based on the case of invisible criterion blocking line protection under unstable high resistance ground fault, this paper analyzes the test requirements, platform, equipment parameters and test items of modeling and simulation of unstable high resistance ground fault based on RTDS, on the basis of accurately grasping the characteristics of the unstable high resistance ground resistance change. The test results show that the proposed simulation model can accurately fit the characteristics of unstable high resistance ground fault. Based on the summary of the test results, this paper further puts forward engineering suggestions for optimizing the operation performance of the protection device.

Research on Discontinues Current Power Cable

WANG Ruiqi, YANG Wenfeng, XIA Junshan, CHEN Jielian , LIU Yan

2020, 40(4):  19-23.  doi:10.3969/j.issn.1008-0198.2020.04.004

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Intermittent large alternating current in the thermonuclear fusion time passes through the power cable, causing the cable temperature to rise and damaging the cable insulation. To solve the problem, a transient thermal path model is proposed to study the change of cable temperature by using iterative optimization algorithm, and the structure of the cable is optimized. The correctness of the cable temperature intermittent high pulse current is verified through tests, which provides a basis for the development of thermonuclear fusion cable.

Economy Study of Variable Load Operation for 660 MW Steam Turbine

LI Mangmang, ZHOU Xuebin, YI Xiaojian

2020, 40(4):  24-26.  doi:10.3969/j.issn.1008-0198.2020.04.005

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With the change of domestic power consumption structure, large-scale thermal power units should participate in the peak regulation according to the requirements. In this paper,taking the 660 MW unit as the object, according to the coal consumption results of the performance test, the two operation mode of the economic situation including low-load operation and two-shift system mode under the depth peak shaving operation is compared.If the load capacity of the power plant is larger and the peak-shaving time is longer, the economy of the start-stop double shift system is more remarkable. For subcritical peaking units, the economic mode of low load operation is always better than that of two shift system. However, if the peak regulation time is longer, especially the deep peak regulation is not limited to the hot start time, the two shift system operation mode will has more energy-saving significance.

An Improved Method of One-terminal Fault Location for Hybrid Power Cable-overhead Line

WANG Chen, YE Jiangming, CHEN Hao, RAO Daiyang

2020, 40(4):  27-31.  doi:10.3969/j.issn.1008-0198.2020.04.006

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In the “power cable-overhead line” hybrid transmission line, the line impedance is no longer continuous because the impedance angle of the cable and overhead line is different. If the line parameter difference is ignored,the traditional single-terminal distance measurement algorithm has great influence on the accuracy of fault location .In this paper, an improved single-terminal distance measurement algorithm based on piecewise parameter derivation is proposed based on the impedance homogenization processing method . The impedance of cables and overhead line sections with different impedance angle is segmented evenly. The segmental fault location formula is derived by the segmental parameter derivation method, and the expression of segmental fault distance is presented. Using MATLAB, the hybrid line is modeled and simulated. By comparing the simulation results, error analysis and summary are made. The results show that the distance measurement error of the improved subsection parameter derivation method is smaller.

Faults and Analysis

Cause Analysis and Solution Method of Welding Seam Leakage of Blocking Plate Valve for Boiler Main Stream Pipe

YONG Manjiang

2020, 40(4):  32-35.  doi:10.3969/j.issn.1008-0198.2020.04.007

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The leakage of the welding seam welding the valve body for boiler main stream pipe valve and the transition stub happened in a certain power station. Based on visual inspection ,test of metallography, hardness and ultrasonic,and consulting manufacturing and installation data, the operating conditions are grasped,and the cracking causes of blocking plate welding seam are analyzed comprehensively.The on-site repair welding and replacement measures are taken to ensure the safe operation of the boiler.

Treatment and Analysis of Water Leakage Fault on Coil Winding for Double Water Internal Cooling Generator Rotor

ZHOU Wenyuan

2020, 40(4):  36-38.  doi:10.3969/j.issn.1008-0198.2020.04.008

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Taking the leakage fault diagnosis of a double-water internal-cooling generator in an overseas power plant as an example, this paper analyzes the difference of leakage water quality and leakage morphological characteristics. In this paper, the leakage fault of rotor winding of double-water internal-cooling generator is rapidly diagnosed under the limited field condition without shutdown, and the causes of leakage are analyzed by the opportunity of shutdown.

Causes Analysis of Wire Spacer Falling Off in a 220 kV Three-span Transmission Line

CAO Xianhui, OUYANG Kejian, CHEN Junjun, LIU Weike, FENG Chao, YANG Tao

2020, 40(4):  39-42.  doi:10.3969/j.issn.1008-0198.2020.04.009

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In view of the single side falling off failure occurred in the spacer rod of a “three-span” power transmission line, the dimensional inspection, physical and mechanical test analysis, field vibration measurement and simulation research are carried out. Based on the failure reason, the prevention and treatment of unilateral shedding of interphase spacer rod is proposed.

Searching and Analysis of DC Grounding Fault with Anti-distributed Capacitance Method

CAO Wenbin, CHEN Ruizhen, CAO Bin, DAI Wenliang, WU Wenjian

2020, 40(4):  43-46.  doi:10.3969/j.issn.1008-0198.2020.04.010

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Distributed capacitance has an adverse effect on the DC ground fault search,resulting in false alarms or insufficient detection sensitivity.It may also cause protection malfunctions during the grounding fault search .This paper analyzes the impact of distributed capacitance on DC grounding fault search from the perspective of DC system architecture,fault type and grounding fault search principle,and distinguishes large distributed capacitance branches from the perspective of phase comparison and characteristic frequency to achieve anti-distributed capacitance during grounding fault search.

Analysis of a Grounding Fault Caused by Wiring Error in DC System

CHEN Ruizhen, XIE Zhihao, GAO Tipan, WANG Xiao, CHEN Zhilong

2020, 40(4):  47-50.  doi:10.3969/j.issn.1008-0198.2020.04.011

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The DC system of substation provides reliable power for protection device, signal device and automatic safety device. It is an important factor of relay correct operating and its fault may affect the safe operations of the power system. According to a metallic ground fault DC bus negative pole occured during the repair work of a battery, the fault cause are analyzed, and some suggestions are put forward for the completion acceptance and routine test of DC systems.

Analysis on Over Tripping Accident of Main Transformer Caused by a Line High Resistance Grounding Fault

YIN Chaoyong, XU Hao, XU Liqiang, LI Hui

2020, 40(4):  51-54.  doi:10.3969/j.issn.1008-0198.2020.04.012

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When the high resistance ground fault occurs in the line, the fault characteristics are not obvious. At present, it is difficult for the protection device with single terminal electric quantity to realize the reliable and quick operation of the wholeline, and identify the fault.This paper introduces a single-phase high resistance grounding fault of 110 kV transmission line, analyzes the protection action of relevant lines and main transformer after the fault, points out the fault cause. It draws a conclusion that when the high resistance grounding fault is unstable and stable, protection devices may be refused to move, and its selectivity and sensitivity is difficult to meet the requirements.

Experience and Discussion

Research on Operation Strategy of Power Generation Enterprises in the Electricity Spot Market

CHENG Daotong, ZHU Guangming

2020, 40(4):  55-58.  doi:10.3969/j.issn.1008-0198.2020.04.013

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This paper studies and analyzes the strategies of power generation enterprises in marketing, planning performance, fuel supply, comprehensive statistics, financial management, risk control and other business operations in the Guangdong spot market of electric power, seeks the road suitable for the future operation and development of power generation enterprises, and promotes its own market competitiveness and value creativity in this round of electric power system reform.

Analysis and Evaluation on Computational Methods of Monitoring Index of Dam Deformation

LIU Yi, YANG Songlin, ZHOU Xiaolu, KUANG Chufeng, PENG Ke

2020, 40(4):  59-62.  doi:10.3969/j.issn.1008-0198.2020.04.014

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The formulation of dam deformation safety monitoring Index is a basic content of automatic, digital and intelligent construction of dam safety monitoring.In this paper, the principle, calculation process and applicable conditions of the calculation method of dam deformation monitoring index are systematically analyzed, which provides guidance for the formulation of dam deformation monitoring index. This method has been successfully applied to a power station project.

Lightning Strike Analysis and Ground Rectification Protection in Alpine Wind Farm

FAN Zhaosheng

2020, 40(4):  63-67.  doi:10.3969/j.issn.1008-0198.2020.04.015

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By expounding the mechanism of lightning damage, establishing the lightning discharge model and evaluating the grounding grid condition of wind farm, on the basis of a comprehensive study of the grounding grid conditions of wind farms, the process of over-voltage damage caused by lightning to wind turbines and box-type substations and the equipotential connection system, an in-depth analysis is carried out on the accidents of equipment damage caused by lightning strikes in wind farms. The improvement measures, such as the improvement of grounding grid and equipotential connection, and the replacement of low-voltage side surge protector are introduced.

New technology and Application

Analysis on New Techniques of Secondary and Auxiliary Control System in Intelligent Substation

PAN Hua, LI Hui, YAN Yabing, MAO Wenqi, LI Gang, YIN Chaoyong

2020, 40(4):  68-73.  doi:10.3969/j.issn.1008-0198.2020.04.016

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Combined with the experimental construction of Hunan 110 kV Shizishan intelligent substation, the whole structure of the substation is introduced. The exploration and application of the secondary and auxiliary control system in realizing holographic perception, autonomous inspection, remote monitoring, active forewarning and intelligent decision is emphatically analyzed. The necessity and test items of secondary and auxiliary control system joint commissioning test in factory are proposed in the view of engineering. At last, the relevant suggestions in realizing the effective landing of new technology are given.

Development and Application of RS485—carrier Bidirectional Data Converter

WANG Shaohuai, LI Jianming, TAN Zhixin, LIU Ruifang

2020, 40(4):  74-76.  doi:10.3969/j.issn.1008-0198.2020.04.017

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In the power system and many industrial applications, long-distance 485 communication is often encountered, which requires a long communication cable and a large amount of work. In order to solve this problem, by changing the working mode of type II collector, it has the function of RS485 and carrier two-way active data transmission, so as to build the "RS485—carrier—RS485" networking mode, and convert the wired 485 communication to the 220 V power line carrier communication. Bidirectional conversion device is divided into broadband and narrowband, which can adapt to different communication rates, self-organizing network, stable and reliable communication, simple use, strong adaptability, and has broad application prospects.

Design and Implementation of Power Metering Device Troubleshooting System Based on Cloud Platform

YIN Dongyang, HUANG Hongqiao, LI Kai, TAN Cong

2020, 40(4):  77-80.  doi:10.3969/j.issn.1008-0198.2020.04.018

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Combined with the knowledge and experience of many experts, this paper uses the new internet of things technology, and establishes an expert system based on cloud platform for power metering troubleshooting. The system is composed of hand-held test terminal, hand-held APP and cloud server. The on-site handlers uploads the on-site information through hand-held APP, queries the fault database and asks for online experts to realize intelligent troubleshooting and online diagnosis of metering device fault. The application example shows that the system effectively improves the troubleshooting ability and work efficiency of the field maintenance personnel,and reduces the technical requirements of the on-site maintenance personnel.

Study on Emergency Communication Channel Scheme Based on Wireless Sensor Network

DUAN Ying, YU Bin, NING Chunhai, XIANG Wei, ZHU Weijun, HUANG Hualin

2020, 40(4):  81-86.  doi:10.3969/j.issn.1008-0198.2020.04.019

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Optical fiber differential protection is widely used as the primary protection of power transmission line, but it may fail influenced by extreme natural and man-made hazard which would impair protection performance. In order to reconstruct emergency communication channel after hazard, combining with power facilities monitoring system, this paper presents a technical scheme of pilot differential protection channel based on wireless sensor network,introduces the network structure and characteristics of wireless sensor network(WSN), analyzes the superiority of communication mode on WSN for protection of traditional mode . In addition, the paper researches the arrangement mode and power supply of sensors, discusses the key technology including network reliability and time delay , and designs a routing protocol applied to emergency communication channel to ensure reliable transition of protection information.