Trunk Transmission Research Articles

Nonlinear wave equation for wavelength/polarization multiplexed signals in fiber transmission

Wavelength/polarization division multiplexing (WDM/PDM) schemes are standardly employed in trunk transmission systems, for which fiber nonlinearity is a serious problem. Generally, the signal transmission characteristics suffering from fiber nonlinearity have been analyzed using the nonlinear Schrödinger equation or the Manakov equation, which was originally presented for single-channel transmission. Therefore, when they are applied to WDM systems, the polarization states of each wavelength light are assumed to be identical, which is not fit to long-haul transmissions wherein the polarization states of WDM signals randomly and independently vary during the fiber transmission. Considering such conditions in WDM/PDM transmission systems, this paper presents a nonlinear wave equation for WDM/PDM signal transmission, which describes the signal behavior in systems where the polarization states of each WDM light are fully random and independent. A formula modified from the Manakov equation is derived using the polarization state coordinate of each signal light in WDM/PDM systems.

100 YEARS OF ELECTRIFICATION: HISTORICAL EXPERIENCE AND MODERN CHALLENGES

Basing on the principles of historicism and objective analysis the article examines the features and problems of implementing two state electrification plans: GOELRO plan adopted 100 years ago, under which the construction of local power plants in the Middle Volga region began, and the General Plan for the USSR Electrification, approved in 1932, which laid down the main solutions to radically redevelop the industry and agriculture of the region on the basis of using the sources of hydroelectric power, constructed on the Volga. In this regard, the historical and comparative method made it possible to highlight the main stages in creation and development of the power system of the Chuvash Republic, which since the mid 1950s has acted as a central a link in the country’s unified electric power system. The idea of creating energy hubs of the Volga Cascade, which in the years that followed provided the rise of industrial and agricultural production of the region, was based on the need for the priority development of the integrated power grid taking into account a strictly defined sequence of regional power plant construction, however, these aspects of implementing the electrification plans are not exampled in the domestic historical literature devoted to the reform of the energy industry. The article notes the pivotal role of scientific and technical cooperation between Leningrad and Cheboksary power engineers and instrument makers in solving the most complicated tasks in times of peace and during the war, it considers the contribution of Chuvash power engineers, who provided the construction and modernization of dozens of trunk transmission lines, which made it possible to fully implement the country’s electrification plan and to ensure energy security of the region.

Development of Trunk Transmission Online Integrated Stability Control System (ISC) for New Generation Grid

SUMMARYGenerally, if power transmission lines are heavily loaded, the transient stability and frequency stability tend to be worse, and one power system fault may cause wide‐area blackouts. However, restriction of the power flow sacrifices economical operations. To solve this problem, CEPCO (Chubu Electric Power Co., Inc.) has implemented the online stability control system.Since a current system was constructed more than 20 years ago, the situation of power system has drastically changed such as a large‐scale introduction of distributed energy resource or increase of cross‐regional power interchange. To cope with these changes, we are developing a new stability control system with new control functions. And, the new system integrates current systems which were constructed separately for the purposes. As the result, the number of equipment was dramatically reduced.This paper describes an outline of developing system and new stability control functions to overcome various situational changes that have happened in CEPCO power grid.

次世代グリッドに適応した基幹系統合型オンライン系統安定化システム（ISC）の開発

次世代グリッドに適応した基幹系統合型オンライン系統安定化システム（ISC）の開発

Fast computation and stable convergence technique for unbalanced load flow calculation in large‐scale systems

AbstractThis paper presents a new method of unbalanced load flow calculation to improve complexity by the method of advanced symmetrical coordinates. Usually, the electric power system has been calculated only by the positive phase sequence component on the assumption that three‐phase transmission lines and loads are balanced. However, many ultrahigh‐voltage transmission lines are not transposed, and therefore mutual inductances cause negative sequence currents in the trunk transmission system. Negative sequence currents cause heating of generators and transformers, and therefore the three‐phase sequence component should be calculated accurately. We examined the fast computation and good convergence performance of unbalanced load flow calculation by models of three‐phase transmission lines, transformers, and loads. The proposed method is not the phase coordinate system but the method of symmetrical coordinates. This technique decreases numerical complexity by the use of a simplified Jacobian matrix. The convergence performance of this method is inferior to that of the usual Newton–Raphson method. As a consequence, the problem of poor convergence performance is alleviated by a technique for the newly developed deceleration Newton method. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(1): 17–24, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21034

Basic study of dropout by phase jump characteristic modeling of distributed generators in secondary system for trunk transmission system analysis

AbstractThe secondary systems are expressed by a reduced model in trunk transmission system analysis. Thus, multiple distributed generators in the secondary system are expressed by the reduced model. But by representing distributed generators by the reduced model, partial dropout of distributed generators cannot be expressed, and therefore there is a possibility that we cannot perform an accurate analysis. Consequently, we studied a method of dropout characteristics in which distributed generators are expressed by the reduced model. To obtain the dropout characteristic, we performed parameter studies by the detailed model and the reduced model on a secondary system under the same conditions. The parameter study indicated that in the dropout characteristic the remaining voltage in the primary system is correlated with the percentage of induction machines in the secondary system. Thus, we derived a dropout characteristic in which the above two quantities were taken as parameters. To confirm the validity of this dropout characteristic, we calculated the dropout magnitudes of the distributed generator for two or more conditions with both the detailed model and the reduced model. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 172(1): 27–37, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20869

Fast Computation and Stable Convergence Technique for Unbalanced Load Flow Calculation in the Large Scale System

This paper presents a new method of unbalanced load flow calculation to improve complexity by the method of advanced symmetrical coordinates. Usually, the electric power system has been calculated only by positive phase sequence component on the assumption that three phase transmission lines and loads are balanced. However, many ultra high voltage transmission lines are not transposed, therefore mutual inductances cause negative sequence current in trunk transmission system. Negative sequence current causes the heating of the generators and transformers. Therefore, the three phase sequence component should be calculated accurately.We examined fast computation and good convergence performance of unbalanced load flow calculation by the models of three phase transmission lines, transformers and loads. The proposed method is not the phase coordinate system but the method of symmetrical coordinates. This technique decreases numerical complexity by the use of simplified jacobian matrix. The convergence performance of this method is inferior to usual Newton-Raphson method. In consequence, the problem of poor convergence performance is improved by the technique for newly developed deceleration Newton method.

Basic Study of Dropout by Phase Jump Characteristic Modeling of Distributed Generators in Secondary System for Trunk Transmission System Analysis

The secondary systems are expressed by a reduced model in trunk transmission system analysis. Thus, multiple distributed generators in the secondary system are expressed by the reduced model. But by representing distributed generators by the reduced model, partial dropout of distributed generators cannot be expressed, and therefore there is a possibility that we cannot perform an accurate analysis. Consequently, we studied a method of dropout characteristics in which distributed generators are expressed by the reduced model. To obtain the dropout characteristic, we performed parameter studies by the detailed model and the reduced model on a secondary system under the same conditions. The parameter study indicated that in the dropout characteristic the remaining voltage in the primary system is correlated with the percentage of induction machines in the secondary system. Thus, we derived a dropout characteristic in which the above two quantities were taken as parameters. To confirm the validity of this dropout characteristic, we calculated the dropout magnitudes of the distributed generator for two or more conditions with both the detailed model and the reduced model. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 172(1): 27–37, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20869

Operation Tests for SN Transition Superconducting Fault Current Limiter in the Power System Simulator

One of important problems to be solved in Japanese trunk transmission systems is the reduction of short-circuit capacity. As one solution, double buses are split into two buses in some substations. In recent years, dispersed generators have been introduced in lower voltage classes due to the deregulation of the electricity. A fault current exceeding the capacity flows during a short-circuit fault by the connection of dispersed generators. One of the key technologies for solving the above problem is the fault current limiter. We are presently conducting research on the effect of the introduction of fault current limiters into a power system. In this paper, we describe the results of operation tests of the SN transition superconducting fault current limiter (SCFCL) using 3 phases of SCFCL modules against various kinds of system faults or inrush current in the power system simulator installed at Central Research Institute of Electric Power Industry (CRIEPI).

Allocation and design of power system stabilizers for mitigating low-frequency oscillations in the eastern interconnected power system in Japan

Low-frequency oscillations have been observed on trunk transmission systems in Japan, and have been the subject for studies in fields of operation, control, and devices by the many power system utilities. Power system stabilizers (PSSs) are very effective controllers in enhancing the damping of low-frequency oscillations, since the controllers can increase damping torque for inter area modes by introducing additional signals into the excitation controllers already equipped with generators. In this paper, allocation of PSSs in an interconnected power system with inter area modes has been determined by an eigenvalue analysis, and PSSs for the allocated generators have been designed by a frequency response method. The designed PSSs have been verified in a Japanese power system standard model. This test system is created as a standard model based on the trunk transmission systems in the eastern area of Japan, and reflects characteristic features of the real power systems; therefore, realistic allocation and design for enhancement of the stability of low-frequency oscillations have been verified.

PSS design for damping of inter-area power oscillations by coherency-based equivalent model

In Japan, low-frequency oscillations have been observed on trunk transmission systems, and have been the subject for studies in fields of operation, control, and devices by many power system utilities. Power system stabilizers (PSS) are very effective controllers in enhancing the damping of low-frequency oscillations, since the controllers can increase damping torque for inter area modes by introducing additional signals into the excitation controllers already equipped with generators. To analyze and solve the problem of long-term poor damping oscillation phenomena, a method is presented to find the best allocation and to design PSS for damping inter-area power oscillations. The method is based on the single-machine-infinite-bus models derived from the multi-machine power system by coherency-based reduction technique. Dynamic simulations using a 10-machine power system model are presented in order to show the effectiveness of the PSS designed according to the proposed method.

Operation Tests for SN Transition Superconducting Fault Current Limiter in the Power System Simulator

One of important problems to be solved in Japanese trunk transmission systems is the reduction of short circuit capacity. As this countermeasure, double buses are split into two buses in some substations. In recent years, dispersed generators are introduced in lower voltage classes due to the introduction of the electricity deregulation. In such a distribution system as many dispersed generators are introduced, it is a possibility that the fault current becomes beyond the breaking capacity at the occurrence of short circuit.Introduction of superconducting fault current limiters into a power system is very effective as one of the means to solve the above-mentioned problem, and we have studied on the effective introduction method of them and setting method of their parameters.This paper describes the results of the operation tests for SN transition type of a superconducting fault current limiter using 3 phases of FCL modules against various kinds of system faults or inrush current in the Power System Simulator installed at CRIEPI.

A Study of Electromagnetic Radiation of Corona Discharge Near 500-Kv Electric Installations

Data on the spectral composition and intensity of electromagnetic radiation of corona discharge are obtained in an experimental study performed on the outdoor switchgear of the Shagol 500-kV substation of the Chelyabinsk Enterprise of Trunk Transmission Grids and under a 500-kV Shagol – Kozyrevo overhead transmission line. The electromagnetic environment on the territory of the 500-kV outdoor switchgear is shown to be determined by narrow-band radiations (harmonics of the frequency of electric supply) and wide-band radiations due to corona discharges of high-voltage sources. This means that the personnel experience the action of a commercial-frequency electric field and electromagnetic radiation of a quite wide range, which is not allowed for by the existing guidelines. It is recommended to continue the study in cooperation with medical institutions in order to create guidelines that would allow for the joint action of commercial-frequency electric field and electromagnetic radiation and for the voltage in the line, the current load, the meteorological situation, and other factors.

The setting method of the specific parameters of a superconducting fault current limiter installed at the bus-tie and response of protective relays at operation of the SFCL

We have investigated the setting method of specific parameters for a resistance-type and a rectifier-type superconducting fault current limiter (SFCL) installed in trunk transmission lines and the response of protective relays when SFCLs operate against a system fault. This paper describes the setting method of specific parameters of an SFCL installed at a bus-tie in a trunk substation, response of protective relays such as bus protection and line protection when the SFCL operates against a system fault and countermeasure of preventing tripping a sound line due to unwanted operation of some distance relays resulted by reverse current at operation of the SFCL.

Transmission pricing in Japan

This paper describes the present status of competition in the electric utility industry in Japan and the present transmission pricing system. Under the amended Electricity Utility Industry Law of 1995, the electric utility industry was categorized into the 3 types: ‘general’, ‘wholesale’, and ‘special supply’ utilities. This paper also summarizes the first competitive bidding from independent power producers (IPPs) and the evaluation of demand site proximity in the bid process. In 1996 the major utilities published wholesale wheeling price lists for IPPs. Although wholesale wheeling prices are similar to the megawatt-mile (MW-mile) approach, the trunk transmission line cost and the average local transmission cost are treated separately. The present study reviews the present wheeling price system in Japan from the principles of transmission pricing established for short-term and long-term efficiency and implementation. Finally, we propose a 2 -part tariff on transmission services for IPPs. Capacity cost should be allocated by a modified usage method. Operating cost including line losses should be allocated by a marginal or incremental method. We further propose the application of the cooperative game theory to the cost allocation problem.

An evaluation method for power transfer capability enhanced by lightning countermeasures

AbstractVarious countermeasures are taken against lightning faults in power transmission lines to decrease their occurrence and improve transmission reliability. However, how much they enhance the power transfer capability has not yet been quantitatively evaluated. The conventional deterministic approach, which is widely used in power system planning methodology, is inadequate to deal with this issue.This paper proposes a new method for numerically defining the power transfer capability enhanced by countermeasures against lightning. The proposed method is based on a probabilistic approach in which several fault patterns are taken into consideration with their occurrence frequency and maximum transferable power. This paper also gives an example application of the proposed method to a model trunk transmission system. The effect of a third overhead ground wire on the increase of transfer capability of a 500 kV transmission line has been quantitatively evaluated.

A numerical integration method for long‐term power system dynamic simulation

AbstractLarge power system frequency/voltage fluctuations due to severe faults in trunk transmission lines or major generating units may trip‐off other facilities and result in large‐scale power system blackout. To prevent such blackout, development of an accurate and fast long‐term power system dynamic simulation tool is required. With respect to the development stage, selection of a numerical integration method available for step‐size adjustment, and the development of a scheme for the adjustment are principal subjects.The trapezoidal and the second‐order Gear methods were selected as possible candidates for the step‐size adjustment from the viewpoint of numerical stability. The trapezoidal method is selected from the viewpoint of accuracy and applicability to power system dynamic simulations.A new scheme for the automatic step‐size adjustment is proposed for the trapezoidal method to achieve fast simulation of the long‐term power system dynamics. The validity of the proposed scheme is verified through simulation studies on a single‐machine‐to‐infinite bus system.

Experience with power system stabilizers in a longitudinal power system

Low frequency oscillations have been a major concern for many years in the Taiwan power system. To damp out inter-area oscillations, a number of power system stabilizers were applied at the slow response excitation systems of the most influenced generators. In this paper, the choice of stabilizer parameters and the evaluation of overall system performance improvement were studied extensively from simulation, testing and operating aspects. Both the stabilizer performance index and the spectrum analysis of steady state observations were proposed for assessment needs. From the evidence, the choice to increase system damping and power transfer capability of trunk transmission lines by adding proposed stabilizers was verified. >

雷害対策による電力輸送力増大効果の評価手法

Various preventive measures are taken against lightning faults in power transmission facilities to decrease their occurrence frequency and improve transmission reliability. However, how much they enhance the power carrying capability of a transmission line has not been quantitatively defined so far. To solve this issue rationally, it is useless to adopt the conventional deterministic approach which is widely used in power utilities as a general rule for power system planning. This paper proposes a new method for numerical evaluation of the transfer capability by means of lightning measures. The proposed method is based on a probabilistic approach in which several fault patterns are considered with their occurrence frequency and maximum transferable power. This paper also applys the developed method to a trunk transmission model system and shows numerically the effect of 3 ground wires on the increase of carrying capability of a 500 kV transmission line.

Optical amplification in trunk transmission networks

Progress in trunk transmission technologies and the impact that these systems may have on the next generation high-speed communication networks are discussed. A nonrepeatered, long-span system field test carried out at 600 Mb/s is reported. The prototype system, using multiple in-line erbium-doped fiber amplifiers and installed dispersion shifted single-mode fiber cables, was tested over a span of 300 km. Repeater spacing compatibility with the existing 600 Mb/s system was confirmed, and capacity upgradability to 10 Gb/s was verified. The bit-rate flexibility of the optical fiber amplifiers is discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>