Advanced Materials Research Vols. 1070-1072

Abstract: This article focuses on the characteristics of power supply protection in the Electric railway traction substation and the relationship among the protection configuration, the power grid stability and the security of the main transformer in the traction station. This article analyses the plan of the protection configuration which is safe, reliable, and cost-effective. Also proposes a simplified and optimized scheme.

Abstract: State assessment method of cables with extruded insulation and their accessories, DAC withstand test combined with a diagnostic test (such as PD measurement) has two shortcomings, the output voltage is not high enough for EHV cables, it cannot detect and locate PD effectively when defects are far away from signal acquisition point. This paper focus on DAC voltages up to 250kV and a kind of distributed measurement of PD. Defects existing in arbitrary of tested cable can be accurately measured in theory by installing sensor at intervals along the tested cable. This method has been validated on a long extra high voltage cross-linked polyethylene (XLPE) insulated underground cable circuit and the filed PD test has been completed successfully.

Abstract: The UHF method is one of the most important partial discharge (PD) detection means for GIS, while sensor technique is the key factor of the UHF method. In comparison with external sensors, inner sensors can achieve higher sensitivity. The paper firstly presents a key indicator of the sensor performance evaluation, and builds a simulation model of that. Secondly, the paper implements simulation research on the PD detection performance of the disc-type sensor, especially on the impacts caused by structural parameters based on the simulation model. The research achievements of the paper may provide reference of performance evaluation and design optimization for disc-type UHF sensors.

Abstract: The double-circuit transmission lines have already been the significant component of power system. Because of the symmetric insulation of the two circuits, the case that both circuits trip out often happens when the tower suffer lightning strike. And it harms the stability of power system and causes serious impacts to power equipments. In this paper, an electric-magnetic transient simulation model was established. Using this model, combining the analysis of physical mechanism of back striking trip-out, the influences of earth resistance, height of tower and length of insulator on the lightning withstand level of back striking (LWLBS) were clarified. The LWLBS of high tower is much low, therefore the relative high tower should be paid more attention to defense the back striking. Reducing the earth resistance and increasing the length of insulator can both upgrade the LWLBS observably. Especially, reducing the earth resistance can enhance the effect of upgrading the LWLBS by increasing the length of insulator.

Abstract: Considering the requirement of Shenzhen power grid development, this paper investigates the parameters selection for 220/20kV gas insulation transformer, including capacity, short circuit impedance, cooling mode, insulation level, over-load capability, temperature rise tolerance, loss , noise level and bushing selection. For different capacity value, the investment and loss concerning substation, 220kV grid and 20kV grid are analyzed and compared, by which the final capacity value is determined. The short circuit current level, transformer loss, manufacturing capability and investment is investigated to determine the short circuit impedance for the gas insulation transformer. The characteristic and application condition of gas cooling as well as liquid cooling mode is studied and the cooling mode for the gas insulation transformer is determined. The insulation level, overload capability and temperature rise tolerance are determined by considering related standards and the requirement of Shenzhen. The loss and noise level for the gas insulation transformer is determined by considering related standard and parameters of the domestic gas insulation transformers in operation. The gas-gas bushing is used to connect cable box and the transformer.

Abstract: According to a TOM bushing faults, three typical 220kV cable-conductor bushings (COT, TOM and BRDLW) widely used in the power grid are analyzed about diversion structure. Bushing diversion structure, diversion contact surface, current path and installation sensitivity are discussed in the paper. The study found that installation accuracy of TOM bushing has greater effect on contact resistance of diversion path than others. The improper installation of TOM bushing caused overheating defects and finally developed into this bushing fault.

Abstract: In consideration of the slow development of informatization level of relay protection device system business process handling at present, upon the request of relay protection device full life cycle management, this text has put forward the anti-metal RFID technical system for relay protection device field management on the basis of RFID technology, covering the lectotype of tags and read-write device, tag encapsulation, safety protection method. which contributes to settle the problems in relay protection device management, avoid waste of resources, save the economic cost, significantly raise the relay protection management level and working effects, and improve the power grid running performance.

Abstract: The dissertation demonstrated movable equipment to realize uninterruptable power supply on-shore connection, i.e. the movable switchgear and mobile synchronizing cabinet, which can unchanging structure of ship power station rather than hugely increase the investment of shore power transformation, and also achieve continuous electricity power supply for domestic vessels berthing on the ports with shore power interface connecting on-shore power, so as to realize environmental protection in port and expenditure savings for the ship. Ship controlling shore power connection system, by means of the movable switchgear and mobile synchronizing cabinet, can achieve paralleling operation between 400 V/ 50 Hz shore power and marine power generator correspondingly, and also transferring the load and paralleling off marine generators, as well as, paralleling accordingly marine generator with the shore power, corresponding transferring load and cut off shore power. Movable equipment for realizing seamless power supply between the port and ship is simple, reliable, convenient, economical and efficient. The dissertation proves that the device is simple, reliable, convenient, economical and efficient.

Abstract: Electronic current transformer is one of the key equipment of intelligent substation and has a direct impact to the correct operation of relay protection devices. In order to accurately establish the dynamic response model of electronic current transformer, it is needed to extract electromagnetic parameters of Rogowski coil, which is the electromagnetic coupling part of electronic current transformer. This paper builds the electromagnetic parameters model and extracts the electromagnetic distribution parameters of Rogowski coil based on the finite element method, then we use the equivalent method to calculate the lumped electromagnetic parameter. At last, comparing with the experimental results, a good accuracy of the simulation results based on finite element method is presented.

Abstract: Electromagnetic Current Transformer (CT) is one of the main equipment in power system, and the remanence in the measuring or protective windings of CT will influence the stability of the power system. Measuring CT is mainly used for the electric energy measurement in normal working condition, focusing on the steady operation state; while protective CT is usually used in fault or short-circuit condition, and the transient transfer characteristic is of significant important. Considering high remanence operation environment in the power system, the numeric analytical model of CT, which is working in the saturation condition, is depicted in this paper. With analyzing the amount of exciting current caused by remanence and deducing the transfer characteristic of CT, the influence of the remanence on the relay protection and the corresponding precautions are proposed, providing accurate and reliable theoretical basis for the protective CT’s correct action and safety operation after system failure. Finally, the electromagnetic transient model of protective CT (TPY) is built in PSCAD, the simulation result of which shows the validity and practicability of the proposed model.