Hitachi, Ltd.

Kazuo Nishijima

Terunobu Miyazaki

Hiroshi Inoue

Mitsuru Nakamura

Minoru Kanoi

Junzo Kawakami

Hiroyuki Kudo

Kiyoji Iwashita

Toru Takei

Yuzuru Imamura

Eisaburo Sakou

Saburou Yasukawa

Tomoharu Nakamura

An electrical power distribution monitoring system is provided for a power distribution line having a plurality of sections with a plurality of electrical loads connected to the power distribution line to form a power distribution network. The monitoring system has at least one sensor for at least one present electrical value at least one point of the network, and estimates electrical values for at least one section of the line in dependence on both of present electrical values measured by the sensor and data relating to past power consumption by loads connected to the line. Improved prediction of actual conditions in the distribution line can be obtained.

Electrical power distribution monitoring system and method

An electrical power distribution monitoring system is provided for a power distribution line having a plurality of sections with a plurality of electrical loads connected to the power distribution line to form a power distribution network. The monitoring system has at least one sensor for at least one present electrical value at at least one point of the network, and estimates electrical values for at least one section of the line in dependence on both of present electrical values measured by the sensor and data relating to past power consumption by loads connected to the line. Improved prediction of actual conditions in the distribution line can be obtained.

A power stoppage minimizing system for a distribution line and a method of using a distribution line minimize a power stoppage section and a power stoppage time when a short circuit occurs in the distribution line, and employs a first and a second distribution line each connected through a circuit breaker to a corresponding bus and each having switches in position thereon; a normally open tie point switchgear provided between adjacent ends of the first and second distribution lines; a protective relay for opening, when a short circuit has occurred, the circuit breaker a fixed time after the occurrence of the short circuit on the first distribution line; a first unit for opening a switch on the side of a power source and nearest a point where the short circuit has occurred; a second unit for opening, after the switch is opened by the first unit, a switch on the side of a load nearest the switch opened by the first unit; and a third unit for closing the tie point switchgear after the opening of the switch by the second unit, the opening of the switch by the first unit being made within a fixed interval of time for the protective relay. Thus, the short circuit section is located and the switches before and after the short circuit section are opened. The tie point switchgear is then closed to thereby minimize the power stoppage section and time when the short circuit has occurred.

Power stoppage minimizing systems for distribution lines and methods of

Upon the occurrence of a fault on the first distribution line, a faulty section on the distribution line is pinpointed, then a tie point switchgear at the tie point between the first distribution line in which the fault occurred and the other normal second distribution line is closed to form a loop distribution system. Then, a switchgear adjacent to the fault point on the first distribution line is opened. An opposing switchgear adjacent to the fault point is opened on the condition that the fault occurrence continues after having been linked to the second distribution line. The above procedures are executed before the opening of the circuit breaker installed on the distribution bus bar.

Service interruption minimizing system for power distribution line

By forcibly grounding a selected one of three phases of a three-phase power distribution line, a higher line-to-ground voltage is applied to other phases thereby causing very small-scale grounding at a fault position so that the fault position can be specified by detecting the small-scale grounding current as generated.

Forcible grounding generation equipment and grounding occurrence

A plurality of switches are arranged in a distributive manner on a distribution line connected to a power distribution substation, and the switches are connected respectively to fault detection relays. Each of the fault detection relays includes a memory circuit for holding a voltage resulting from a ground fault on the distribution line, and the time constants of the memory circuits are set to become greater in an ascending order from the power outlet of the distribution line. Owing to difference in the time constants, there are differences in the holding voltage of the memory circuits resulting from intermittent ground faults which precede a full ground fault. By utilizing the differences of holding voltage, the switch closest to the full ground fault as viewed from the power outlet of the distribution line is the first to open the circuit.

Power distribution line protection system

A signal transmission/monitoring method for a system including a master station and a plurality of slave stations installed on and along a signal transmission line so as to be capable of mutually performing information transmission and reception in such a manner that the master station calls the slave stations through sequential polling with the called slave station sending reply information to the master station. An interrupt enable time zone is provided between a time point at which the call signal transmission from the master station is completed and a time point at which the reply signal transmission from the slave station is started. When other slave station issues an interrupt request within the interrupt enable time zone, signal transmission to the master station from that other slave station is carried out with priority.

Method of monitoring changes of state of a power transmission system by

A remote monitor control system comprises a single master station having the function of communication in synchronism with communication clocks for generating various commands required for monitor and control, and a plurality of terminal stations having the function of communication in synchronism with the communication clocks for receiving data related to objects of monitor and controlling objects of control. The terminal stations are caused to respond at different time points sequentially predetermined different times after transmission from the master station. When a sync signal fails to be received for a predetermined length of time, the predetermined time set for a particular station is shortened.

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Katsuta, Japan

Kazuo Nishijima