Hideyuki Takani

Live line measurement of untransposed three phase transmission line parameters for relay settings

The purpose of this study is to develop a method to measure untransposed transmission line parameters for protection relay setting. For relaying schemes such as distance relays, current differential relays and fault locators, it is very useful to ascertain the precise setting values in service, without the need for setting calculations prior to installation, and also for the relays to be able to adaptively change their settings as the system configuration changes. This paper describes a method of live line measurement of the parameters of an untransposed three phase one circuit transmission line and untransposed two parallel transmission lines and necessary conditions to measure line parameters. We propose a mathematical approach using synchronous voltages and line currents at both ends of the line in different states, where two models, the equivalent PI circuit and distributed constant line, are employed. For two parallel transmission lines, applying a mode decomposition, we show that two parallel transmission lines can be transformed into double independent three phase circuits. The efficiency and issues are shown using several simulation examples in MATLAB.

A method of measuring three phase transmission line parameters for relay settings

The purpose of this study is to develop a method to measure transmission line parameters for protection relay setting. For relaying schemes such as distance relays, current differential relays and fault locators, it is very useful to ascertain the precise setting values in service, without the need for setting calculations prior to installation, and also for the relays to be able to adaptively change their settings as the system configuration changes. This paper describes a method of untransposed live line measurement of the parameters of a three phase transmission line. We propose a mathematical approach using synchronous voltages and line currents at both ends of the line in different states, where two models, the equivalent PI circuit and distributed constant circuit, are employed. The efficiency and issues are shown using several simulation examples in MATLAB.

Faulted phase selection function based upon impedance comparison in a distance protection relay

The distance protection relay is widely used around the world for the protection of transmission and distribution networks and it is especially essential in its application within bulk power systems. The faulted phase and the fault point on the power line must be determined by the relay with great certainty. In this paper, we propose a unique method to enhance the faulted phase selection function that uses impedance. In this method, an impedance comparison technique, the faulted phase is determined by identifying the minimum of the phase-to-phase impedances based upon the rule that a phase-to-phase fault impedance becomes a minimum for two-phase faults. In order to demonstrate the validity of the new technique, both the conventional method (voltage comparison method) and the proposed method are evaluated in detail for various test cases utilizing Toshiba distance protection relays, GRZ100 and a Real Time Digital Simulator (RTDS). These test cases include evolving faults to other phases and cross-country faults involving parallel double circuit transmission lines. The results show that the conventional method does not always have sufficient capability to discriminate the faulted phase correctly for the cross-country fault cases which have no healthy phases, on the other hand, the impedance comparison method demonstrates superior performance for all of the test cases. The proposed impedance comparison method is shown to be a promising method to enhance the faulted phase selection function for the distance protection relay and has been put to practical use successfully.

Effect and influence of residual current compensation on earth-fault distance relays

For residual compensation of an earth-fault distance relay, a compensation method using only a reactive compensation factor (X0/X1) for the transmission line or a compensation method using both a reactive compensation factor (X0/X1) and a resistive compensation factor (R0/R1) which are widely used in Japan. In this paper, we present the reason why measuring distance errors of earth-fault distance relays occur even when these two residual current compensation methods are used. Furthermore, with the compensation method that uses both reactive and resistive compensation factors, we have shown that depending upon whether the ratio, (RG/RA) of the line to earth resistance (RG) to line to line resistance (RA) is larger or smaller than the resistive compensation factor (R0/R1) that an earth-fault distance relay will respectively either overreach or underreach for a double line to earth fault.