The fault resistance introduces an error in the fault distance estimate, and hence may create an unreliable operation of a distance relay. A new compensation method based on fault resistance calculation is presented. The fault resistance calculation is based on monitoring the active power at the relay point. The compensated fault impedance measures accurately the impedance between the relay location and the fault point. The relay has shown satisfactory performances under various fault conditions especially for the ground faults with high fault resistance. This new compensation method avoids the under-reach problem in ground distance relays

Ground distance relay Compensation based on fault resistance calculation

The invention relates to a method and device for testing differential protection relays or differential protection relay systems. The operating means to be protected by the differential protection relay or differential protection relay system are simulated with all their most important parameters by means of a test device. The test currents calculated in the simulation, in accordance with the means to be protected and other parameters, are sent to the differential protection relay or relay system which is connected to the testing device, so that the operating and error performances of the differential protection relay or relay system can be detected by means of the testing current applied, and can be evaluated in accordance with the specified tolerance data of the differential protection relay or differential protection relay system.

Method and device for testing differential protection relays or differential protection relay systems

In a ring type network, a master node sends a measurement packet to a slave node in the backward direction and the forward direction, receives the measurement packet which has been circulated among a plurality of slave nodes, stores a received time of the backward direction measurement packet and a sending time of the forward direction measurement packet according to time-keeping of an internal clock, sends a measurement result notifying packet showing a sending time and a received time of the measurement packet to the slave node; each slave node receives the backward direction measurement packet and the forward direction measurement packet, sends the received measurement packet to the next node, stores the received time of the backward direction measurement packet and the sending time of the forward direction measurement packet according to the time-keeping of the internal clock, receives a measurement result notifying packet, calculates a time correction value using the sending time and the received time of the measurement packet shown in the measurement result notifying packet and the sending time and the received time of the measurement packet stored, and corrects a time of the internal clock using the calculated time correction value.

Communication system, management apparatus, communication apparatus and computer program

Based on global positioning system (GPS) technology and differential equation algorithms, a new approach to live line measuring of the inductance parameters of transmission lines with mutual inductance is proposed. The principles and mathematical model of the new method are explained in detail. Data processing by least square algorithm is introduced. To take into account the influence of distributed capacitance of transmission lines, a modified mathematical model is introduced. The hardware structure of the measuring system is given and real-time digital simulator (RTDS) experimental results validate the accuracy of the test system. Finally, an example of live line measuring two 220-kV transmission lines with mutual inductances is given. A comparison of measurement results between the differential equation method and the conventional method is also shown.

New Method of Live Line Measuring the Inductance Parameters of Transmission Lines Based on GPS Technology

A status detection apparatus for electrical equipment includes a plurality of distributed multiparameter sensors in a containment vessel or other fluid filled region of the electrical equipment The sensors are capable of providing data relating to plural parameters of the fluid simultaneously at different positions in the fluid The data provided by the sensors can be processed to permit localization of incipient faults or can indicate other operating states when combined with known flow data of the fluid through the electrical equipment A method for detecting status of electrical equipment includes sensing parameters simultaneously at multiple locations in the fluid and determining operating status based on the sensed parameters

Status detection apparatus and method for fluid-filled electrical equipment

In a transformer protection system, data of voltages and currents detected at individual terminals of a transformer connected to an electric power system are supplied to a computer. The computer computes driving point admittances or shunt admittances of the transformer on the basis of the voltage and current data and predetermined transfer admittances of the transformer and decides that an internal fault has occurred in the transformer when the values of the driving point admittances or shunt admittances deviate from pre-set reference values, thereby disconnecting the transformer from the electric power system.

Transformer protection system

Low-frequency transient oscillatory voltages and currents have prompted the development of new distance protection schemes for UHV and EHV power lines with large stray capacitances. The authors describe a scheme that is based on a differential equation for the transmission lines. An integral method with an interpolation technique is applied using a very limited number of data at a sampling rate of 600 Hz. A prototype digital distance relay composed of two 16-bit microprocessors is developed. The characteristic test results correspond well to the results of fault simulations. The method is verified to have an accuracy of +or-5% and require an operating time of less than 50 ms. >

Implementation of a digital distance relay using an interpolated integral solution of a differential equation

PURPOSE:To effectively distinguish a detection current due to an internal accident from that due to an external accident by obtaining an operation amount and a suppression amount at the time of nonsaturation in each cycle of a line current, and detecting the amplitude of a differential value due to a phase difference with an accident current. CONSTITUTION:A ratio differential relay is composed of operation amount calculating means, suppression amount calculating means and accident discriminating means. The operation amount calculating means calculates the sum of the momentary values of two line currents, calculates the operation amount of the relay on the basis of the absolute values of the difference of the present value of the sum of the calculated momentary values and a value before a predetermined time, calculates the scalar sum of the momentary values of the two line currents, and calculates the suppression amount of the relay on the basis of the absolute value of the difference of the present value of the calculated scalar sum and a value before a predetermined time. The accident discriminating means calculates the difference value between the operation amount and the suppression amount, and discriminates the content of the accident on the basis of the difference value.

Ratio differential relay

PURPOSE: To cope with a change in the constitution or processing time of stations by using a ring-type LAN by causing a main station to transmit a data frame in synchronism with a main synchronizing signal, and in a slave station, detecting the time from the generation of the own synchronizing signal to the reception of the data frame by using part of the data frame and synchronizing it to the main synchronizing signal. CONSTITUTION: A main station 1 1 transmits a frame in synchronism with a main synchronizing signal S. The frame is returned to the main station 1 1 again after it is repeated and transmitted by each slave station 1 2 -1 1 . The main station 1 1 measures the time T l from the generation to the reception of the main synchronizing signal S and at the same time, recognizes the number Na of stations subscribing to the network by means of the subscribing station counter of the frame. Then the main station 1 1 informs the slave stations by writing the delay time 17 per one repetition of the frame and transmitting the frame to the slave stations. Each slave station generates its own synchronizing signal in synchronization with the main synchronizing signal after recognizing its receiving order from the main station, finding the delay time until its own station receives the frame after the generation of the main synchronizing signal, and adjusting the generating timing of its own synchronizing signal. COPYRIGHT: (C)1990,JPO&Japio

Kazuyoshi Yoshida

Papers

Transformer protection system

Implementation of a digital distance relay using an interpolated integral solution of a differential equation

Ratio differential relay

Signal synchronizing system

Transformer protecting method