Considering the existing main problems of the directional protection of high voltage and ultral high voltage transmission lines, a new method for determining the fault direction based on the R-L model is proposed in this paper.

When power system runs normally,and when positive directional fault and inverse directional fault of various fault types occur in power system,the characteristic of the signal of the bus is very different. According to this information,this paper poposed the model and algorithm of the fuzzy neural network to be used to identify the fault direction.

In addition,the non-uniform subsidence in vertical direction is detected on roof strata,and the roof strata especially the lower strata are oblique to the fault direction.

To detect and diagnose the faults in heating, ventilation and air conditioning (HVAC) systems effectively and operate the system safely and efficiently, a new method for fault detection and diagnosis (FDD) in HVAC systems, named fault direction space method (FDSM), was presented.

The Ms6.1 Mangya earthquake on 14th January 1990 is locted at a convergence of gravity anomaly zones, which rupture propagation direction corresponds with fault direction.

It is widely known that fault direction can be determined accurately by power directional relay when non-fault phase voltage is introduced to eliminate blind area with 90° connection.

A novel directional protection principle based on R-L model parameter identification is proposed,where the system resistance and inductance are sought out,then the symbolism of system resistance and inductance in interior and exterior faults is investigated to determine the fault direction.

In this paper the authors derive three algebraic equations, equations(3), (5) & (6), which work on the measurement of initial impedance, modification of the phase-angle and iteration of the impedance respectively. Thus, this newly developed fault locating algorithm provides higher accuracy and high speed for the microcomputer based distance relay. Obviously, it is immune from fault resistance and power flows.Accompanying the locating algorithm, a new discriminant of the fault direction is also presented...

In this paper the authors derive three algebraic equations, equations(3), (5) & (6), which work on the measurement of initial impedance, modification of the phase-angle and iteration of the impedance respectively. Thus, this newly developed fault locating algorithm provides higher accuracy and high speed for the microcomputer based distance relay. Obviously, it is immune from fault resistance and power flows.Accompanying the locating algorithm, a new discriminant of the fault direction is also presented (equation(7)), which is carried out during the calculation of equation(3). It cannot cause the relay losing of direction.A prototype of microcomputer based distance relay had been made. A series of strict experiments included digital simulation and dynamic power system model test was carried out. The test results are shown in Table 1, 2 & 3, perfectly match theoretical analysis and demands.

This paper analyzes the characteritics of fault transient travelling waves on a single phase transmission line. Then the characteristics of travelling waves propagation on the three-phase transmission line are studied using the method of modal analysis. A new distance protection scheme is presented. First the fault type and phases are recognized and a backward travelling wave singnal is combined. Then the fault direction and distance are determined by recognizing the characteristics of combined singnal....

This paper analyzes the characteritics of fault transient travelling waves on a single phase transmission line. Then the characteristics of travelling waves propagation on the three-phase transmission line are studied using the method of modal analysis. A new distance protection scheme is presented. First the fault type and phases are recognized and a backward travelling wave singnal is combined. Then the fault direction and distance are determined by recognizing the characteristics of combined singnal. The proposed algorithm has been tested by numerical simulation using a electromagnetic transient program of a typical 500kV system based on improved Bergeron method. The experiment of a single phase relay protype was made, which proved the correction of proposed algorithm.

Considering the existing main problems of the directional protection of high voltage and ultral high voltage transmission lines, a new method for determining the fault direction based on the R-L model is proposed in this paper. It has been pointed out that the microcomputer based directional protection using the proposed method has the properties of fast and reliable operation, and is easily realized.