Zhen Fang

Study of a novel fault current limiter on the basis of high speed switch and triggered vacuum switch

Limiting the short-circuit current is of great significance to keep the safe and steady running of the power system. A novel fault current limiter (FCL) is presented. A high speed switch is used to rapidly break the short-circuit current. A triggered vacuum switch (TVS) is used to discharge a precharged pulse capacitor so as to quench the arc in the high speed switch quickly and to realize the active transfer of the short-circuit current. A resistor is used as the current limiting component. The parameters of a FCL of 10 kV voltage level are designed. Simulations of the FCL in an oscillating circuit are performed by means of the ATP software. Experiments of a FCL sample device are also carried out in the oscillating circuit. The experimental results are in agreement with the simulation results. The current transfer characteristics and the current limiting effect are testified.

Design and Experimental Study of a Novel Fault Current Limiter

Limiting the short-circuit current effectively is of great importance to keep the safe and steady running of the power system. A novel fault current limiter (FCL) on the basis of a high speed switch and a triggered vacuum switch (TVS) is presented. The high speed switch is used to break the short-circuit current of the power system. The TVS is used to discharge the precharged pulse capacitor so as to rapidly extinguish the arc in the high speed switch and to realize the active transfer of the short-circuit current. A resistor is used to limit the short-circuit current. The parameters of the FCL for the 10 kV power system are designed and a FCL apparatus is fabricated. An onsite experiment of the FCL apparatus is performed in an actual transmission line of a substation. The FCL apparatus operates normally and achieves the expected current limiting effect.

Study and experiment of mobile DC de-icer for overhead ground wire

Serious icing disasters threaten the safe running of power system. Overhead ground wires are difficult to de-ice with common heat de-icing methods in some special areas. A mobile DC de-icer for the overhead ground wire is developed in this paper to realize flexible de-icing. A diesel generator provides the 50 Hz three-phase power supply. A rectifier transformer is used to step up the voltage and a rectifier is used to convert AC to DC. The 12-pulse rectification mode is adopted to reduce the current harmonics of the rectifier and to decrease the ripple of the DC output. Onsite experiment of the mobile DC de-icer for the overhead ground wire is performed on a GJ-70 typed overhead ground wire with the length of 4847 meters. A temperature rise of 7.0°C is achieved in 36 minutes under the DC de-icing voltage of 2700 V and current of 100 A. The result shows that the mobile DC de-icer for overhead ground wire can operate reliably and can meet the demand of flexible de-icing.

A Novel Overhead Ground Wire with Winded Insulated Conductors for Ice-Melting

Serious icing on overhead ground wires threatens the safe running of power system. Common overhead ground wires are difficult to realize ice-melting. A novel overhead ground wire structure for ice-melting is proposed. Some conductors coated with insulation layer are winded around the galvanized steel wires in a special way. Ice-melting experiments are performed on the novel overhead ground wire. Experimental results show that 30 W per meter of the wire is an economic power while 40 W per meter of the wire is an effective power for ice-melting. Engineering application of the novel overhead ground wire with insulated conductors is carried out. With the light moveable de-icer, onsite experiment is performed. Under the power of 40 W per meter of the wire, a temperature rise of 10 °C is achieved in 30 minutes. The result shows that the novel overhead ground wire can meet the demands of engineering application.

Manufacture and experiment of a novel composite insulator

Serious lightning or icing often causes flashover on the insulators and probably results in a tripping accident. A novel composite insulator with lightning protection and icing flashover prevention is presented. The novel composite insulator with the rated voltage of 220 kV, specified mechanical load of 100 kN for the whole insulator and the nominal discharge current of 10 kA for the lightning protection part is designed and is manufactured. Basic performance, electrical performance, and mechanical performance are tested for the novel composite insulator. The experimental results show that the novel product meets the requirements of both standards of the common composite insulator and the common line metal oxide surge arrester and achieves the application conditions.

Protection against lightning on monitoring system of transmission line icing

This article introduced the design background of online monitoring system of transmission line icing, and the reason of it being struck by lightning, which is easy to be received in the thunder and lightning environment. The article also proposed a method about the monitoring system of transmission line icing protecting against lightning, and analysis devices of protecting against lightning, over current and over voltage. It provided the design reference of online monitoring system of protection against lightning on the open country transmission line and the towers.

Forecast method of lightning activity based on the weather conditions

Lightning activity is a common phenomenon, which always is a great thread to safety of power grid, and its the important reason for the accident of power grid and non-planned stopped operation. Through make analysis on the statistics data of lightning activities in Hunan area, we summarize that the historic discipline of lightning activity, and propose six typical weather situations which is prone to appear lightning weather. And this proposed method has been taken to make lightning forecast. Through giving lightning forewarning information, it can offer great guidance to the anti-lightning work of transmission line.

Application of ion earthing electrode and anti-corrosion synthetical reconstruction technique in reconstruction of grounding grids

Grounding grids play an important role in guarantee the safe operation when the station has encountered the short circuit or be attacked by lighting. Grounding grids must reconstruct when grounding resistance does not meet the regulation requirements. Using ion earthing electrode to reconstruct the grounding grid will cost less and have better effect. However, this way may increase the corrosion of grounding grid. In this paper, “ Ion earthing electrode with anti-corrosion” grounding grid reconstruction technique is presented. This technique not only exerts the advantages of ion earthing electrode but also prevents grounding grid from corrosion. It was applied in 500kV Aijiachong power station, 220kV Nanzhutang power station, and so on. Grounding resistances of these power stations reached prospective effect after reconstruction.

Development of High Temperature Superconductor Current Limiter

Short current limiting technology is a hot problem in power grid with short current increasing. Several short current limiting technologies are analyzed. And improved bridge-type superconductor current limiter which can limit instantaneous and steady short current is presented. Resistance-type, bridge-type and improved bridge-type superconductor current limiter are simulated. Scheme and parameters are proposed, based on which we develop a 10 kV high-temperature superconductor current limiter. In Aug.14th, short testing implements at Gaoxi 110 kV power station in Loudi bureau, Hunan Province. Later, the limiter runs in the power grid. In short testing, the limiter can prevent the short current from 3500 A (Vms) to 635 A(Vms). There is no saltation in wave. The superconductor current limiter has run six month and all indexes are well-balanced. All these can make a base for superconductor current limiter large-scale application.

Development and Application of Capacitor Compensation AC De-Icing Equipment

Considering that conventional AC de-icing method has many shortcomings such as complicated braking operation and difficult arrangement for power operation modes, we propose the new AC de-icing technology using capacitor compensation. On this basis, a novel regulative capacitor series-wound compensating AC de-icing equipment is developed, which works through controlling the line current to be within the permitted range in order to melt the ice. By the unique design mechanism of changing the series-parallel connection modes of capacitor combination and capacitor number for each combination, this equipment can make reasonable compensation for transmission line of arbitrary length within 40 km. Field test at JiLi 220kV substation of Hunan province manifests that this new-style AC de-icing equipment has remarkable effect with low energy consumption, simple operation and low engineering cost, thus has bright prospects of engineering application.