Tokyo Shibaura Denki Kabushiki Kaisha

Hitachi, Ltd.

The Tokyo Electric Power Company, Incorporated

Kunio Matsuzawa

Ryotaro Kondow

Mitsuru Yamaura

Junichi Inagaki

Kazuyoshi Yoshida

Tetsuo Matsushima

Hiroyuki Kudo

Yoshihiro Sano

Keizo Inagaki

Yoshifumi Oura

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

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.

Setting device for protective control system

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.

Digital distance relays

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.

Apparatus and method for protection of electric power transmission lines

Growing community of inventors

Sagamihara, Japan

Kunio Matsuzawa