Gao Houlei

Development of GPS synchronized digital current differential protection

This paper describes a newly developed digital current differential protection scheme for power transmission lines. The proposed protection is different from existing ones in two aspects: one is the use of GPS time information to implement synchronized sampling at all terminals of the protected line; the other is the application of a new differential algorithm based on fault component instantaneous value. To evaluate the performance of the protection scheme, both an EMTP simulation study on the new algorithm and dynamic simulation tests on the prototype of the protection are conducted. The test results have proved the correctness of the new algorithm and the feasibility of the whole protection scheme. This paper starts with a brief introduction to the overall configuration of the protection scheme, then focuses on the description of principles of GPS based synchronized sampling and the new differential algorithm. Simulation results are also presented.

The current differential and travelling wave based algorithm for ultra high speed hybrid protection

Basing on the instantaneous value current differential algorithm and the current travelling wave polarity comparison algorithm, this paper proposes a novel hybrid algorithm for ultra high speed transmission line protection. The hybrid protection algorithm retains the advantages of two algorithms: fast fault detection speed and high reliability level, meanwhile, effectively eliminates their disadvantages. The hybrid relay scheme utilizes a set of hardware platform and same communication channel to perform data processing and fault detection. Simulation results coming from EMTDC demonstrate that the combined algorithm is capable of achieving fast fault detection speed while maintaining a high reliability level.

Calculation method for one-section lumped-circuit model of uniform line

This paper aims to simulate transient characteristics of distributed parameter model by one-section lumped-circuit model (lumped-Π, lumped-T and lumped-Γ models). Based on error analysis of equivalent impedance in the lowest resonant frequency band of distributed parameter model and lumped circuits, a parameter calculation method of lumped circuits was proposed in this paper. The first simplification principle is to ensure power-frequency equivalent impedances equal. Secondly, be sure the first resonant frequency equal and comprehensive error of equivalent impedance in the lowest frequency band minimum. Contrast with traditional one-section lumped circuits, the applicable frequency band of one-section lumped-Γ, lumped-T and lumped-Γ models raised in this paper is extended. Obtained results can be used for the establishment of transient equivalent circuit.