Abstract: A protective relay system for protecting a power system includes a selection circuit, a comparing circuit, and a data processing unit. The selection circuit time-sequentially switches a plurality of input signals having electrical quantities from the power system under control of the data processing unit and applies the input signals to the comparing circuit. The comparing circuit applies to the data processing unit a discriminated output signal representing the result of the comparing of a level of a signal having an electrical quantity and obtained from the input signals to the comparing circuit with a reference level. At a time point upon lapse of a time corresponding to an electrical angle of 90.degree.

Abstract: A protective relaying system is disclosed which includes a selection circuit for receiving a plurality of input signals from a power system and for selecting one of the input signals to provide a selected input signal. The system also includes a comparison circuit connected to the selection circuit for receiving the selected input signal, comparing the selected input signal with a predetermined reference signal, and producing a decision signal according to the result of the comparison. The system further includes a processing unit connected to the comparison circuit for receiving the decision signal and processing the decision signal to produce a relay output signal.

Abstract: Digital setting value data, having been stored in a first non-volatile memory in response to the operation of a first switch, is transferred to and memorized in a second non-volatile memory. Stored setting value data is read out from at least one of the first and second memories under the control of an address control circuit and coupled to a digital processing section for carrying out digital arithmetic processing for protective control in the processor.

Abstract: In a digital protective relaying device for protecting electric power transmission line including an electric station at each end thereof, and each electric station including at least one circuit breaker to be tripped by a protective relay for protecting the own station, a digital protective relay provided with a computer is further provided at each end so as to receive electrical data in digital form from the electric stations for operating in an ordinary protective operation. As a control condition occurs in one station, the condition is sent to a digital protective relay provided at the other end of the transmission line, thereby changing the operational steps of the computer included in the protective relay.

Abstract: In data processing apparatus in which address and data are transferred by means of DMA through an address bus and a data bus, a coincidence circuit determines whether the address on the address bus coincides with an address designated by an address designation device, a latch circuit latches the data on the data bus when the coincidence is detected and stores the latched data, and an indicating device indicates the data stored in the latch circuit.

Abstract: In a digital distance relay including sample-hold circuits for sampling the voltage and current of an electric power line system, analog-digital converters for converting the outputs of the sample-hold circuits into digital values, memory devices for memorizing the digital values and a program, and a central processing unit for exercising a relaying operation, there is provided a central processing unit which includes means for determining whether at least one of the digital values is greater than a predetermined value. The relaying operation of the distance relay is initiated only when the one digital value is greater than the predetermined value. A method is disclosed which includes the above determining step.

Abstract: An input setting method for a protective relaying apparatus including an input setting switch for setting data, a digital operational device for carrying out a relaying operation utilizing the data, and a memory device for storing the data, the method comprising the steps of setting the data by the input setting switch, storing the data thus set in the memory device, comparing the set data with the stored data, carrying out the relaying operation utilizing the data when the compared data are found equal, and issuing an alarm signal when the compared data are found to be unequal.

Abstract: In a digital protective relaying device utilizing a microcomputer for protecting an electric power transmission system, a setting switch is provided for writing the values into the computer after the relaying operation of the protective device is locked by a locking means. The protective values thus set in the computer is indicated on an indicating device under the control of the computer and visually checked by an operator, while the computer always confirming the coincidence of the set values with the indicated values.

Abstract: In a protective relaying apparatus for an electric power transmission system and the like there is provided a nonvolatile memory device in which various values required for protection of the system are written electrically. An input device designates addresses in the memory device and memorizes values in the addresses under control of a control device. A digital processing device carries out the protective operations for the electric power transmission system based on the values thus set in the non-volatile memory device.

Abstract: In a protective relaying device comprising first and second potential transformer circuits for transforming voltages of an electric power system, first and second relaying elements are further provided for receiving the output voltages of the first and second potential transformer circuits, respectively so that each of the relaying elements delivers an output of a particular logic state when it operates. When the outputs of the first and second relaying elements coincide with each other, a logic circuit receiving the outputs delivers a tripping signal to a circuit breaker.

Abstract: The method and the system are for detecting a current I and a voltage V of the electric power system and judging that there is fault if:.vertline.V-I.epsilon..sup.j.phi. .vertline.V.vertline./.vertline.I.vertline..vertline.<k.sub.ois fulfilled, where k.sub.o represents a constant and I.epsilon..sup.j.phi. an electrical quantity obtained by shifting the current I by a predetermined angle .phi.. In a modified form, the expression.vertline.V-I.epsilon..sup.j.phi. X.vertline.<k.sub.ois used, where X equals to .vertline.V.vertline./.vertline.I.vertline. or Z (a predetermined line impedance) whichever is smaller.