Isolated Phase Bus Research Articles

Structural Stability and Weak Points Mechanism of a High and Vertical Enclosed Isolated Phase Bus

Recently, with the rapid rise of new energy generation, pumped storage power stations also have experienced rapid development. Due to the considerable vertical height of these power stations, high and vertical enclosed isolated phase buses (EIPB) are more and more widely used. This type of high and vertical EIPB structure differs from the horizontal EIPB structure, as it is more significantly influenced by the gravitational load during actual operation. Thus, it is crucial to investigate the stability of the novel high and vertical EIPB structure under its own gravity load. In this study, the strength of the I-beam and cross-arm of the EIPB under the influence of the gravitational load was studied through analytical calculations and finite element static analysis. The results indicate that the strength of the I-beam and cross-arm is within the threshold of the corresponding material’s load-bearing capacity, demonstrating the stability of the EIPB structure. This work holds significant value for the structural design and further optimization of high and vertical EIPB.

Isolated-Phase Bus—Design, Operation, Deterioration, and Failure

This article describes the design considerations, operation limitations, deterioration mechanisms, and failure prevention of air-insulated isolated-phase bus. The results also present the different failure modes observed in service.

Stray Magnetic Field Analysis of ITER Poloidal Field Converter Unit

Due to the space limitation and safety concerns, the non-same-phase anti-parallel connection structure is applied in the International Thermonuclear Experimental Reactor (ITER) Poloidal Field (PF) converter unit. Consequently, the electromagnetic interference caused by the strong stray magnetic field has been one of the main concerns in its design. And this paper mainly presents the stray magnetic field analysis of ITER PF converter unit. At first, an isolated phase bus (IPB) is designed for the shielding of the alternating magnetic field generated by the ac busbars to avoid overheating on ferromagnetic materials in the fire wall. The stray magnetic field on the fire wall is analyzed to verify the shielding effectiveness of the IPB. Then, the stray magnetic field generated by the converter bridges and dc reactors which is very hard to be shielded is analyzed separately. The results show that the stray magnetic field exceeds the limit value and will be a potential threat for the instrument and control (I&C) system. All the analysis presented in this paper will provide useful inputs for the electromagnetic compatibility design and test of the I&C system.

Thermal-Dynamic Stability Analysis for the Enclosed Isolated-Phase Bus Bar Based on the Subsegment Calculation Model

As a part of the power system, the stability of the enclosed isolated-phase bus bar (EIPB) plays an important role in the working safety of the power system. Usually, the dynamic-thermal stability of EIPB is analyzed by the theoretical analysis or the finite-element method (FEM). The dynamic stability can be calculated by 2-D model. For the complex structure and huge size of EIPB, large synchronous generator-side EIPB in power system is rarely analyzed. In this paper, a new co-simulation method of EIPB is studied. The subsegments EIPB model based on FEM is established, and the temperature distribution in joint surfaces is transmitted. The method is applied to a certain type of EIPB in power system. The FEM model is simulated. The temperature distribution of EIPB under certain cooling condition is also calculated. Based on the thermal results, the dynamic stability of EIPB is calculated to analyze the electrodynamic force under short-circuit condition. In addition, the feasibility and the validity of the method are proved by the test EIPB.

Electromagnetic Shielding Effectiveness Analysis of Isolated Phase Bus Applied for ITER Poloidal Field Converter

Isolated phase bus (IPB) is generally used in power plants to connect the generator to the main transformers due to its shielding ability. And this paper presents the electromagnetic shielding effectiveness analysis of the IPB applied in International Thermonuclear Experimental Reactor poloidal field converters. The circulating currents induced in the enclosures and the magnetic field around the IPB are analyzed and studied. An equivalent electrical circuit is built to analyze the circulating current with a nonsinusoidal input by solving the corresponding numerical differential equations. And an experimental test is also performed on a full scale prototype to verify the model and results of the analysis. In addition, magnetic field distribution around the IPB is analyzed based on the Fourier decomposition and finite-element method. The analysis result indicates that the IPB is of good electromagnetic shielding ability. And the method of the analysis presented in this paper is proved to have great value in the analysis and design of IPB used in converter systems.

Thermal Design of High-Power Water-Cooled Enclosed AC Busbar for ITER Poloidal Field Converter

Isolated phase bus (IPB) is chosen as the structure type of the enclosed ac busbar for ITER poloidal field (PF) converter, which is used to connect the rectifier transformer and the converter unit of the ITER PF converter module due to its electromagnetic shielding ability. To solve the heating problem of the high-power IPB, water cooling method is adopted. This paper presents the thermal design of high-power water-cooled ac enclosed busbar which is applied for ITER PF converter. The proposed approach takes full advantage of the quickness of the analytical method based on the heat transfer theory and the accuracy of the 3-D finite element method, focusing on the predictions of the temperature rise of circulating water and the enclosed busbar. Temperature measurements from the test based on a full scale prototype of the IPB show good agreements with the predictions, which proves the high efficiency and accuracy of the proposed approach in the design of cooling scheme for the ten-kilowatt-class enclosed ac busbar.

Momentary Current Test of Enclosed AC Busbar for ITER PF Converter Performed on ITER AC Test Platform

Isolated phase bus (IPB) is chosen as the structure of the enclosed ac busbar for ITER PF converter, which is used to connect the rectifier transformer and the converter unit of the ITER PF converter module due to its electromagnetic shielding ability. The IPB should withstand huge fault currents, of which the peak value of the current can reach 350 kA, in the worst fault condition according to the design requirement. In order to verify the dynamic stability of the IPB, a momentary current test for ITER PF IPB is necessary. In this paper, the momentary current test of the IPB applied for ITER PF converter based on ITER AC test platform is designed and carried out in detail. The effectiveness of the test scheme is verified by the results of both the simulation and the test. The test scheme presented in this paper is of great value for conducting momentary current tests of electrical equipment with large alternating currents.

Numerical Calculation of Short Circuit Electromagnetic Force in Isolated Phase Bus

Short circuit electromagnetic forces are one of the most important factors in design and operation of buses. 2D infinite element models are set up with ANSOFT for isolated phase buses, simulating with transient method and calculating short circuit electromagnetic force taking eddy effect and proximity effect into account. The result reveals that the maximum electromagnetic force under short circuit condition is a periodic function of current phase angle.

Analyses of three-dimensional eddy current field and thermal problems in an isolated phase bus

In this paper, a three-dimensional eddy current field model to calculate the eddy current losses in an isolated phase bus (IPB) is proposed. The rise in temperature of the conductors and enclosures in the IPB are evaluated using the proposed set of thermal equations. Computation results of a 20-kV/12.5-kA IPB scheme are reported to validate the algorithm. The withstand voltage ability and short-circuit stress of the IPB are also verified. The agreement between the computation and test results confirm that the design scheme being studied is successful and practical.

Proximity effect and magnetic field calculation in GIL and in isolated phase bus ducts

This paper deals with an integral numerical method suitable to predict the current density distribution in typical multiconductor systems represented by gas-insulated lines (GIL) or by isolated phase MV bus ducts, highlighting their proximity effect. Besides the prediction of power density distribution due to Joule losses, the integral approach makes the evaluation of the external flux density easy. The simplicity of the approach, the conciseness of the matrix algebra applied, and the close-to-reality procedure make this method extremely attractive for self-made software implementation on any commercially available math packages such as Matlab. For the sake of comparison, a finite-element method (FEM) model of the system has been implemented. In this model, a coupling between electric circuit and electromagnetic model has been used in order to take into account the real power supply conditions.

相分離母線への三次元渦電流解析の適用

相分離母線への三次元渦電流解析の適用

Practical design of generator surge protection

Generator withstand voltages, overvoltages from the power system, and arrester capabilities are critically reviewed. The specified withstand is compared with tested breakdowns for some 248 coils in five large machines using DC, power frequency, and impulses. System stresses normally prescribed for lightning are supplemented to included HV line faults, circuit breaker closing, reignitions and restrikes, fault clearing, arcing faults on the isolated phase bus, harmonic line resonance, ferroresonance, transformer HV to LV faults, the effects of stuck breaker poles, and other contingencies. It is found that internal winding stresses may be amplified due to resonance and slot reflection effects. The vulnerability of arresters to temporary overvoltages is considered. Practical guidelines for the design of generator surge protection are provided. >

Shielding Properties of Isolated-Phase Bussystems

The shielding effectiveness of an isolated-phase bus with continuous enclosures depends on a number of parameters. To study this problem we developed a system to measure amplitudes and phase angles of the currents in an isolated-phase bus during regular operation in a power plant. In our theoretical description we give new inductance values for three cylinders in situations with strong proximity effects. The flux near the short-circuiting ircuiting end connection is strongly influenced by the currents and fields outside the bussystem. Good agreement ent between calculated and measured sheath currents is reported for three bussystems. The asymmetry between the currents in the two outer sheaths is explained.

Shielding Properties of Isolated-Phase Bus Systems

The shielding effectiveness of an isolated-phase bus with continuous enclosures depends on a number of parameters. To study this problem we developed a system to measure amplitudes and phase angles of the currents in an isolated-phase bus during regular operation in a power plant. In our theoretical description we give new inductance values for three cylinders in situations with strong proximity effects. The flux near the short-circuiting ircuiting end connection is strongly influenced by the currents and fields outside the bussystem. Good agreement ent between calculated and measured sheath currents is reported for three bussystems. The asymmetry between the currents in the two outer sheaths is explained.

Proximity Effects in Cylindrical Bus Enclosures

General expressions for proximity effects in cylindrical bus enclosures (isolated phase bus, continuous type) have been developed based on Maxwell's equations for electromagnetic fields. It covers cases of enclosures with finite thickness and made of material with given physical properties.

Forced Air Cooled Isolated Phase Bus-Experimental Verification of Design Parameters

Currently 1300 MW machines are being installed in power plants and 1500 and 2000 MW machines are a distinct possibility. Consequently isolated phase bus in power plants has to carry continuous currents as high as 40,000 amps or more. In this paper the results of tests conducted under laboratory conditions up to 36,000 amps is analyzed and discussed. An empirical approach for determining time-temperature behavior under emergency conditions, such as failure of cooling equipment, is suggested. The detailed design of a forced cooling system for isolated phase bus is discussed.

The minimum ac resistance of slabs and tubes

It can be shown that the minimum ac resistance of a tubular conductor does not occur when the tube is solid. Derivations of and reasons for this behavior are presented. Knowledge of this effect can result in more efficient operation of high-power ac equipment where skin effect losses are important. Examples in the power field are overhead lines, underground cables, and isolated phase bus; examples in the microwave region are resonant cavities, high-power waveguides, and high-power coaxial lines.

The measurement of current distribution in isolated-phase bus enclosures

Current density probes for directly measuring the current distribution in cable sheaths and isolated phase bus enclosures are described. They are simple to construct and can be used to measure both transient and steady-state alternating or direct current distributions with excellent resolution in both time and space.

Proposed Guide for Calculating Losses in Isolated-Phase Bus

The proposed guide forms a useful document for those responsible for evaluating losses in isolated-phase bus. The Working Group plans two modifications in the final version of the guide. The first is an extension of Fig. 1 to make it more useful in the calculation of skin effect of very large enclosures. The second modification will be the inclusion of an empirical formula for more accurate determination of the K factor to be used in determining losses in continuous bus enclosures. The fomula will be based on test data reported in [6].

Measured Losses in Isolated-Phase Bus and Comparison with Calculated Values

The results of loss measurements on an isolated-phase bus are recorded and compared with values calculated by a proposed guide [1]. The calorimetric test method is described.