Line Differential Protection Scheme Modelling for Underground 420 kV Cable Systems

Based on the analysis of a specific relay model and an HVAC （high voltage alternating current） cable system, a detailed approach to EMTDC/PSCAD modelling of protective relays is presented. Such approach allows to create complex and accurate relay models derived from the original algorithms. Relay models can be applied with various systems, allowing to obtain the most optimal configuration of the protective relaying. The present paper describes modelling methodology on the basis of Siemens SIPROTEC 4 7SD522/610. Relay model was verified experimentally with its real equivalent by both EMTP-simulated and real world generated current signals connected to the relay.

STUDY ON EFFECTS OF ARSENIC TRIOXIDE ON GASTRIC CANCER CELL LINES

Objective To evaluate the effects of arsenic trioxide (As-2O-3) on apoptosis and differentiation of gastric cancer cell lines (GCCL). Methods MKN45 and SGC7901 cells were treated with As-2O-3 at different concentrations, then the apoptosis rates and cell cycle were determined by flow cytometry assays, the morphologic changes were observed under fluorescence microscopy and electronic microscopy, and the gene expressions were tested with immunohistologic staining. Results Higher apoptosis rates of GCCL were seen in the As-2O-3-treated group at concentrations of 5μmol and 10μmol, as compared with those in the 5-Fu-treated group. Cell-nuclear pyknosis and chromosomal condensation were observed. The As-2O-3 at a concentration of 0.5 μmol could induce the cell cycle changes of GCCL, revealing an increase in the proportion of G1/G0 phase cells and a decrease in the proportion of S phase cells. From the fifth day after treatment of SGC7901 with As-2O-3 at a low concentration, P53 and bcl-XL genes expression rates were reduced, Bax gene expression rate increased, and bcl-2 gene expression showed little change. Conclusion As-2O-3 could induce GCCL apoptosis at a high concentration and differentiation at a low concentration, but it could not completely reverse the malignant biological behaviours of cancer cells.

THE DIFFERENTIATION OF HUMAN GASTRIC ADENOCAR-CINOMA CELL LINE MGc80-3 INDUCED BY DIBUTYRYL cAMP IN VITRO

For providing some experimental basis in establishing malignant phenotypic reversed indexes of gastric carcinoma cells, human gastric adenocar-cinoma cell line MGc80-3 was induced by dBcAMP in vitro to appraise the effect of gastric carcinoma cell differentiation by chemical inducers.Under light microscope, MGc80-3 cells, after treated with 1 mM dBcAMP, tended to be flat and disperse, and their volume gradually enlarged, with their uncleus relatively smaller and their shape rather regular. Morphological changes, like norma differentiated epithelial cells, were observed. The cells attached firmly, grew slowly, their growth curve showed inhibitory rate amounted to 52.87%, and cellular division exponent displayed their peak value 1.5 times less than that of MGc80-3 cells. It was clear that dBcAMP could effectively inhibit the multiplication activity of MGc80-3 cells. After dBcAMP treatment, remarkable changes of cell surface charges was indicated by cell electrophoresis, the ratio dropped to 3.043 from 3.988, and their re-tardant ratio reached up to 31.2%. cAMP content in cells after this treatment, detected by cAMP and cGMP radioimmunoassay, was enhanced by 2.42 times, and cAMP/cGMP ratio, by 1.73 times. Thus, cAMP level within MGc80-3 cells was raised obviously by dBcAMP. Heterotransplantation experiments showed that tuntorigenic rate of MGc80-5 cells (transplanted subcutaneously to BALB/c mice) amounted to 100%, and that of the cells after this treatment was only 5.6%. Their tumorigenic ability was extremely reduced.These results confirmed that dBcAMP was able to change malignant phenotypic characteristics of MGc80-3 cells and produce a reversed alteration: Thus, it has a remarkable inductive effect in differentiating gastric carcinoma cells. All these characteristics were also considered as the reference indexes in appraising reversed effect for the homologous cancer cells.

Introduction to an Invariant Quantity Method

It is impossible,mathematically, to use a time series which is regarded as a set of observational facts of a dynamicsystem to reconstruct the particular system.Physically, however, with a few assumptions put, a dynamic system canbe rebuilt approximately by means of observational facts.This is the goal of the so called invariant quantity method(IQM),whose research and experiment are of potential significance to atmospheric sciences.

Applying Modern Communication Technology to Loss-of-Mains Protection

The protection of distribution networks is facing new challenges from an increasing amount of DG （distributed generation）. Even though current technology provides satisfactory solutions to manage this new situation, LOM （loss-of-mains protection） is still considered problematic. The solution proposed in this paper focuses on the use of a line differential protection relay. It inherently contains a suitable communication channel and provides absolutely selective protection for the feeder. Furthermore, it prevents the feeder relays from false tripping for faults on the neighboring feeder. The present trend in protection communication points towards the use of fiber optics. For line differential protection, this means a fast and high-capacity communication link which enables the implementation of many advanced protection functions. In addition, a solid foundation for such a communication link is offered by the new IEC 61850 standard and Ethernet technologies. The basic functionality of the line differential protection enables the operation of both the feeder protection and the DG protection for any fault on the feeder. Furthermore, basic LOM protection methods can be applied as backup protection for failures on the communication link.

Impact of Sensor Technology for Line Protection Performance

The paper has presented the impact on the line protection performance with the introduction of MUs （merging units） in the process bus level. The paper begins with the introduction on modem digital substation structure and process bus. Then, the paper describes the performances of different sensors such as CTs （current transformers）, CVTs （capacitive voltage transformers）, FOCS （fiber optical current transducers） and FOVS （fiber optical voltage transducers）. With the use of above transducers together with MUs, the performance of distance protection function and line differential protection function have been investigated and presented. Finally, conclusions based on the study are presented in the paper.

JACOBI SPECTRAL APPROXIMATIONS TO DIFFERENTIALEQUATIONS ON THE HALF LINE

Presents a study which investigated some Jacobi approximations which are used for numerical solutions of differential equations on the half line. Application of the approximations to problems on unbounded domains; Algorithm to prove the stability and convergence of the approximations.

Optimization of ohmic contact for InP-based transferred electronic devices

The effect of the annealing time and annealing temperature on Ni/Ge/Au electrode contacts deposited on the n-type InP contact layer has been studied using a circular transmission line model. The minimum specific contact resistance of 3.210 7 cm2was achieved on the low-doped n-type InP contact layer with a 40 s anneal at 425 ℃. In order to improve the ohmic contact and reduce the difficulty in the fabrication of the high doped InP epi-layer, the doping concentration in the InP contact layer was chosen to be 51018cm 3in the fabrication of transferred electronic devices. Excellent differential negative resistance properties were obtained by an electron beam evaporating the Ni/Ge/Au/Ge/Ni/Au composite electrode on an InP epi-layer with a 60 s anneal at 380 ℃.