17 февраля 2017
«ЭЛЕКТРОЭНЕРГИЯ. Передача и распределение» № 1(40), январь-февраль 2017
INTERVIEW OF THE DAY
Reports overview of 3-rd research and practical conference on equipment condition monitoring of power engineering facilities (Moscow, December 7, 2016)
According to proceedings of the 4-th All-Russian Forum on Projects, experience and current issues of intelligible grids (Yekaterinburg, December 9, 2016)
Energy Investment Fair as a Part of Power Industry Perspective Development
IDGC of North-West, PJSC
The winning project of “Energoproryv-2016” competition. 3rd place in nomination of “Breakthrough Technology”
IDGC of Volga, PJSC
RAO ES EAST, PJSC
The possibility is considered for range expansion of overhead transmission lines with short lines which are melted by means of developed discretely operated universal rectifying 144
installation for ice melting. Methods and technical solutions as applied to the topic under study are proposed.
A method of current reduction to avoid ice melting system electrical equipment overloading is proposed and investigated. Current reduction is achieved through changing the operation mode of three phase discretely controlled rectifier to double phase mode with a cyclic commutation of rectifier bridge phases in operation. Operation mode changing is performed by universal rectifying installation control system. Allowable overload capacity of electric equipment is shown for ice melting on conductors of short overhead transmission lines. Electric equipment overload become possible with coordinated work of all ice melting system elements such as transformer, controlled rectifier and overhead transmission line.
Algorithm for ice melting system calculation is created. An example is given for current calculation in all elements of ice melting system; overload capability examination of supply transformer when ice melting is sequentially executed on the few short overhead lines for conventional and severe weather conditions as well as determination of minimum allowable length for short overhead lines are melted by means of universal ice melting installation.
Keywords: overhead transmission line, ice melting universal installation, controlled rectifier, transformer, ice melting system
The article analyzes an impact of the new generation of cable lines on transients in electrical grids. It is shown that modern cables with XLPE insulation have small surge impedance. In circuits with overhead lines or power transformers small surge impedance of XLPE cables is able to cause intense transients, accompanied by overvoltages dangerous to equipment insulation.
power cable, XLPE cable, cable surge impedance, transient processes, lightning overvoltage, switching overvoltage
Overhead-to-underground 110–500 kV transmission lines have a number of specifi c features in comparison with cable lines. Among special features of these lines is an application of automatic circuit reclosers. Reclose on a short-circuit fault increases thermal load on the cable insertion material particularly if the fault takes place within the cable section. Therefore, in some countries special selective devices are used on overhead-to-underground transmission lines. These devices allow reclose on fault within overhead line section and prohibit such reclose within cable section. Thermal conditions of 110–500 kV cables are examined in emergency modes, taking into account additional thermal effects of short-circuit currents linked with automatic reclosing and presence of aperiodic components in the breaking current. The necessity is shown to take into consideration these thermal effects when selecting cables on planning stage. Possible effects are given when short-circuit currents with various values and duration impact on overhead-to-underground transmission lines with and without selective devices which prohibit automatic reclosing.
cable, cable line, overhead-to-underground transmission line, short circuit fault, automatic reclosing, heating temperature of cable cores, heating temperature of cable screen, cross-linked polyethylene, aperiodic component in the breaking current
Development of high and extra-high voltage switchgears refl ects the general trends of electric networks improvement. Among these trends are increased reliability, control, compactness, environmental friendliness and safety, reduced maintenance costs and optimization of technical and economic characteristics. CIGRE session in 2016 in Paris slightly changes understanding of high and extra high voltage switchgears modern development.
switchgear, electrical grid, reliability, high voltage unit
The article considers the tools for field / laboratory testing and calibration of instruments for electrical measurements. The test sets and calibration methods are of interest to industrial metrological departments, power industry enterprises and electric measurement equipment manufacturers.
low-voltage measurements, high-voltage measurements, power quality indexes, AC current shunts, testing of measuring instruments
IDGC of North-West, PJSC
“SO UPS”, JSC
MES Centre — branch of “FGC UES”, PJSC