Hitachi, Ltd.

Hiroyuki Kudo

Junzo Kawakami

Takakazu Matsuyama

Yoshikazu Yamanaka

Tadao Kawai

Kazuyuki Yokoyama

Tomio Chiba

Mitsuyasu Kido

Shigeru Mori

Tatsuya Maruyama

Tsutomu Yamada

Shoji Yoshida

Kazuhisa Takami

Chikashi Komatsu

Takashi Hotta

Kotaro Shimamura

Akira Bando

Yuichiro Morita

Shigeta Ueda

Yoshitaka Takahashi

Kazuhiro Imaie

Takeshi Takehara

Shouji Yoshida

Hiroshi Sasaki

Hiromichi Yamada

Yoshio Sato

Kunio Hirasawa

Atsumi Watanabe

Yoshiaki Matsui

Yoshinori Ookura

Hideyuki Yoshioka

Tokushiro Uno

A partial discharge detection apparatus for detecting partial discharge in a power cable and recognizing an insulation deterioration state of the power cable. A low-speed AD converter converts an analog signal of an AC waveform flowing through a power cable into a digital signal. A high-speed AD converter converts an analog signal of a partial discharge current into a digital signal. The partial discharge is detected based on the maximum value or the sum of a current value obtained from the digital signal of the partial discharge current obtained by the conversion of the high-speed AD converter, for each phase of the AC waveform, which is obtained from the digital signal of the AC waveform flowing in the power cable. The digital signal is obtained by the conversion of the low-speed AD converter.

Partial discharge detection apparatus and partial discharge detection method

An object of the present invention is to propose a partial discharge determination device and method that can highly reliably determine the degree of progress of partial discharge occurring in an underground power transmission cable without preparing plural standard patterns. A distribution pattern of a set of the charge amount and the occurrence phase angle of each partial discharge occurring in a period of one or more cycles of an applied voltage of a power transmission cable is sequentially generated, a first classification process in which the pattern is classified into any one of classes on the basis of a standard distribution pattern for each class and a second classification process in which the distribution pattern are executed, a classification result by the first classification process is evaluated on the basis of a classification result by the second classification process, and the degree of progress is determined.

Partial discharge determination device and method

There is provided a communication control device including: a real-time communication status extraction unit that acquires a communication timing of real-time data; a dynamic fragment size determination unit that acquires a fragment size of sending data which can be sent until the communication timing acquired by the real-time communication status extraction unit; a fragment processing unit that fragments non-real-time data to have at least a fragment size which is equal to or less than the fragment size acquired by the dynamic fragment size determination unit; and a communication unit that sends the non-real-time data, which is fragmented by the fragment processing unit, before the communication timing of the real-time data.

Communication control device with dynamic fragmenting of non-real-time data

An object of the present invention is to provide a network system or the like in which the construction cost of a network for a plurality of control systems is suppressed which is excellent in resistance to a network failure. In order to solve the problems, according to the present invention, there is provided a network system including a plurality of communication devices that are disposed in a plurality of bases, and are grouped into predetermined control systems for each of the devices which transmit and receive packets to and from each other so as to monitor or control target equipment, and a plurality of relay devices each of which includes a plurality of communication ports and transmits a packet transmitted by the communication device to another communication device, in which a plurality of communication devices disposed in each base are connected in parallel between the two relay devices, the relay devices disposed in different bases are connected to each other in a ring shape via a network, and a plurality of communication devices disposed in at least one base include communication devices belonging to different control systems.

Network system and relay device

Communication control equipment is connected to a plurality of communication control equipment via a network and is configured to be time-synchronized with the plurality of communication control equipment by using a time synchronization procedure using a communication including at least request packets and acknowledgement packets. The communication control equipment includes a receiving-interval measurement section configured to measure a receiving interval of request packets from the plurality of communication control equipment; and a queuing-occurrence determination section configured to detect conflict of the request packets from any of the plurality of communication control equipment on a basis of the receiving interval of the request packets measured by the receiving-interval measurement section. The communication control equipment is configured to determine whether to transmit an acknowledgement packet to the communication control equipment that has transmitted the request packets based on a detection result of the queuing-occurrence determination section.

Communication control equipment

Disclosed are a digital protection control system and a digital protection control apparatus, wherein the digital protection control apparatus can easily be made to have more terminals, even when the number of terminals of a power transmission line increases. The digital protection control system has, as terminal stations thereof, a reference station that is to become the reference point for the sampling time at which power grid current information is to be taken in, tail-end stations that take in power grid current information from the power grid system, and intermediate stations that are connected between the reference station and the tail-end stations via transmission paths. The intermediate station is provided with an uplink transmission unit that is connected to a transmission path at the reference station side thereof, and a plurality of downlink transmission units that are connected to transmission paths at the tail-end station side thereof. The intermediate station also has the time thereof to be subordinate to the time of the terminal station connected to the uplink transmission unit thereof, and the time of the terminal stations connected to the downlink transmission units thereof are made to be subordinate to the intermediate station, with the time thereof used as reference time.

Digital Protection control system and digital protection control apparatus

A multi-terminal power line protective relay system is provided, which divides a power transmission line having four or more terminals into two or more power line sections composed of three adjacent terminals and portions of the power transmission line lying among the three adjacent terminals and one of the three adjacent terminals being shared by two adjacent power line sections, and includes protective relays at the respective terminals including a current-driven differential protective relay element for detecting a fault occurring in a power line section through current-differential calculation by using measured currents, inter-terminal communication channels linking two protective relays at two different terminals; and intra-terminal communication channels linking two protective relays at each shared terminal. Each protective relay that detected the fault transfers a trip instruction to the other protective relays via the inter-terminal and intra-terminal communication channels and causes the other protective relays to trip circuit breakers.

Multi-terminal power line protection relay system

In a synchronization system adopted in a synchronous-multisystem control apparatus comprising a plurality of systems operating synchronously with each other at a fixed control period, the synchronous-multisystem control apparatus can be operated in a single-system mode in the event of failures occurring simultaneously in some of the systems. The synchronous-multisystem control apparatus employs a plurality of control circuits each provided for one of the systems. Any particular one of the control circuits comprises:

Synchronization system and synchronization method of multisystem control apparatus

In a synchronization system adopted in a synchronous-multisystem control apparatus including a plurality of systems operating synchronously with each other at a fixed control period, the synchronous-multisystem control apparatus can be operated in a single-system mode in the event of failures occurring simultaneously in some of the systems. The synchronous-multisystem control apparatus employs a plurality of control circuits each provided for one of the systems. Any particular one of the control circuits includes: a period-signal generating circuit for generating a period signal indicating a start point of a control period; a synchronization-reference selecting circuit for outputting a synchronization-reference signal by referring to period signals generated by the systems; and a control-period correcting circuit for correcting a control period of the particular system by forming a judgment on a synchronization shift of the period signal generated by the particular system from the synchronization-reference signal and keeping the control period as it is in case the synchronization-reference signal is not generated.

A power signal processing system and method for protection of a power system has a signal input unit for receiving a signal representing a condition of a power system; a plurality of processing units cooperating to apply to the received signal a predetermined process including a series of predetermined different computations thereby producing a control signal for controlling operation of the power signal processing system. The respective processing units operate to perform the predetermined different computations, respectively. A control unit is provided for controlling transfer of data among the processing units so that the different computations are applied, successively, to the received signal thereby producing the control signal which is used to cause, for example, the issue of a cut-off command to a circuit breaker.

Digital control and protection equipment for power system

In order to control a voltage using e.g. a tap transformer, the difference .DELTA.V between the actual voltage and a reference voltage is obtained and integrated over time. That integral is then modified by at least one parameter generated by fuzzy logic from control conditions of the voltage. In this way the fuzzy logic may find the optimum control strategy which keeps the actual voltage closest to the reference voltage without an excessive number of tap position changes. The reference voltage may vary with time, and therefore the control of the voltage with time may be evaluated, and the control conditions varied accordingly, e.g. by fuzzy logic, so that the control arrangement can exhibit learning. Normally, the integral is modified such that

Voltage or reactive power control method and control device therefor

Analog signals are sampled and converted into digital data which is then filtered by a digital filter. The filtered digital data is then subjected to an arithmetic operation. The blocking band of the digital filter is set to a frequency band which is above the pass band of the analog signal components. Frequency of sampling, as well as the frequency of noise caused by the sampling, is elevated, so that the noise frequency falls within the blocking band of the digital filter.

Digital signal processing method and system, electric power system

A disc is provided with the equal-interval pits along tracks, at which digital signals are recorded bit by bit. Such a disc is rotated at the constant angular velocity. A signal processing apparatus according to the present invention detects the linear velocity of the track which is at present followed by a pickup. The filtering of a source signal to be recorded and the analog-to-digital conversion of the filtered signal, in the signal processing for recording, are controlled and timed in accordance with the detected linear velocity. Further, the digital-to-analog conversion of a signal read out from the disc and the filtering of the converted signal, in the signal processing for reproducing, are also timed and controlled in response to the detected linear velocity. Thereby, a disc memory device having the large storage capacity and suited for the random access memory can be realized.

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Tokyo, Japan

Mitsuyasu Kido