J. H. He

Integrated protection of power systems

This paper reports on the development of integrated protection for power system. The concept of integrated protection is introduced, in which a centralized protection system (or relay) provides the protection of multiple power plant or a substation. Examples are given of the protection schemes with the features of integrated protection which are currently under development. A novel integrated protection scheme for substation and network protection is described. The technique is based on the detection and processing of fault generated transient current signals, in which specially designed protection relays are installed at each substation of a network. The transient detection unit of the relay detects the fault generated transient current signals. The transient polarity identification algorithm is then applied to the transient signals to identify the polarity of the signal detected. The direction of a fault is determined by comparison of the polarity of the signals derived from all the line sections connected to the substation. The actual faulted section is identified by processing the directional information from various substations

Simulation and algorithm development of protection scheme in DC traction system

This paper presents a simulation model of DC traction system which is based on bilateral power supply mode. The model of two substation rectifiers in one track section has been proposed which is according to practical situation. The modeling was conducted with respect to the variations of the starting-up process and short circuit conditions. By comparing and investigating the simulation results of short circuit current and the train starting current, more effective algorithms such as DDL protection has been proposed. The paper presents the principle and analysis of DDL protection scheme, which shows effectiveness of DDL protection for fault detection and discrimination against train starting currents in the DC transit system.

Developments of transient and integrated protection for power system

The paper reviews the concept and development of the transient based protection and integrated protection for power systems. A number of new protection schemes with features of transient based and integrated protections are outlined. A new transient based integrated protection scheme for the protection of distribution system plant as well as distribution network as a whole using the transient polarity comparison technique is described. The scheme is based on the detection of fault generated transient current signals from all locations of the protected network. Comparison of the signal polarities obtained provides an indication of the actual faulted section. Like other transient based protection schemes, it is insensitive to the fault type, the fault inception angle, the fault path resistance and the line loading. In addition, it also has new features of integrated protection.

Application of Transient Polarity Comparison Technique to Power System Protection

This paper introduces the development of transient polarity comparison principles for power line protection. A brief introduction to the history of power system protection is first given, which outlines the background of the new developments. The paper then introduces the new protection techniques based on fault transient polarity detection. The descriptions of new relaying techniques based on the detection of fault generated transients and their associated protection schemes are the main part of the paper. The new protection techniques based on transient polarity comparison not only offer significant new features for power line protection, but also produce novel schemes for the integrated protection of power network

A new DC feeder protection based on wavelet transform

This paper presents a new DC feeder protection based on wavelet transform. The model of two substation rectifiers in one track section has been proposed which is according to practical situation. The remote short-circuit current is determined mainly by the steel rail impedance, which is time varying due to the skin effect. In contrast, impedances of the traction motor and the contact wires, and the change of operating mode during starting govern the train starting current. The wavelet transform identifies these salient features. The remote short-circuit current and train starting current are simulated using SIMULlNK. The modeling was conducted with respect to the variations of the starting-up process and short circuit conditions. By comparing and investigating the simulation results of short circuit current and the train starting current, more effective algorithms such as wavelet transform has been proposed.

A Real Time Digital Simulation System for Testing of Integrated Protection Schemes

This paper presents the design of new real time digital simulator (RTDS) based novel relay test systems. The background of the developments in protection relays and their associated technologies, such as optical transducers and IEC 61850, are introduced. The new developments in RTDS systems are described. It is shown that the recent developments in transducers and communication technology will have great impacts to the developments of protection relays and their associated RTDS based relay test systems. The paper further describes the existing, new developments and future trend in the development of protection relays and their associated RTDS systems.

Accurate track modeling for fault current on DC railways based on MATLAB/Simulink

This paper presents an accurate track modeling for fault current on dc railways based on MATLAB/Simulink. With the introduction of skin effect of short-circuit current, the simulation of short-circuit fault based on MATLAB/Simulink is proposed. By comparing and investigating the waveforms of remote short-circuit current with and without skin effect, the paper pointed out the difference between these two currents. Moreover, the calculation of time constant proves the effectiveness of this result.

An integrated protection scheme for power line systems

This paper presents an integrated relay and its associated protection scheme for power line systems. The concept of integrated protection is firstly introduced, in which a centralized protection system or relay provides the protection for multiple power plants or a substation. A novel integrated protection relay based on a combination of a number of protection principles is described. In the proposed scheme, the specially designed protection relays are installed at each substation of a network and are responsible for the protection of every line section connected to the substation busbar. The combined algorithms with multiple settings are implemented into the relay to cover all the protected line sections. Simulation studies show that the proposed protection scheme is able to produce desirable performance and may offer many advantages over the existing one and great potential for future applications.

Design of a real-time substation communication system for integrated protection

This paper proposes an advanced substation communication system based on reflective memory (RM) network in order to implement real time data exchange for the integrated protection. In the system, a central control unit (CCU) and merging unit (MU) with the dual redundant star topologies are the controllable nodes in the network. The field programmable gate array (FPGA) chips are employed in the MU. The coordination between them is specially designed in order to achieve the functions of simultaneous data acquisition and distributed shared memory. Through dividing shared memory into many blocks by data communication protocol, the reliability of data transmission is further improved.

An Advanced Substation Communication System for Integrated Protection

This paper proposes an advanced substation communication system for supporting the latest development in power system protection - integrated protection. Recent developments in power system protection are firstly outlined, and then a description of a substation integrated protection system supported by an advanced communication network is given. Based on the proposal, there are 3 major components within the network: the CVD communication unit; the optical network; and the central integrated protection unit. The research will focus on the concept, evaluation and design of the optical network communication system.