Mitsubishi Denki Kabushiki Kaisha

Makoto Terada

Hiroshi Suzuki

Isao Iyoda

Isao Furo

Yosuko Tsujikura

Akifumi Iwamaru

Yosuke Tsujikura

Yoshiyuki Kobayashi

A load management and control apparatus comprising a control unit in which system voltage and a power flow state are measured to make an arithmetic decision by using the resultant variations in voltage and reactive power so as to estimate system reactance, and the estimated system reactance is used to carry out control operation while establishing unique relationship between tap changing operation of the transformer and connection or disconnection of the reactive power supply unit in the receiving side sub-station so as to set voltage and power factor of the receiving side of power system in desired ranges, whereby in a receiving end side substation, it is possible to prevent frequent tap changing operation of the transformer, and adjust system voltage not only to reduce the voltage deviation but also to provide integrated and reasonable management of the reactive power.

Load management and control apparatus

A semi-conductor bridge thyrister converter circuit for converting AC power into DC power with suppression of the higher harmonics generated by the circuit including a semi-conductor converter circuit, a control circuit, and instrument transformers for measuring the voltages and the currents at the source and the load side at a node. On the basis of the outputs of these transformers, the control circuit controls the control delay angle and the overlap angle of the thyristers of the semi-conductor converter circuit such that higher harmonics generated by the converter current are reduced to a minimum as seen from the power system side.

Thyristor converter system with higher harmonics suppression

A differential protective relay apparatus is switched over between a current differential mode and a voltage differential mode automatically by both even-order harmonic components of an imput applied to a differential circuit and a voltage across an impedance of the differential circuit, thereby to cover extensive fault modes while retaining high minimum pickup sensitivity, furthermore, devised against excessive fault voltages in the voltage differential mode, and, consequently, advantageous in insulation withstand capability.

Differential protective relay apparatus

An apparatus for differential-protection of a bus bar having a plurality of terminals which includes a plurality of trunk lines, in which an impedance of a differential circuit connected in parallel to a current transformer provided in each of the terminals is changed depending on either a terminal voltage of this differential circuit, or another terminal voltage derived from a part of the impedances. Then, either a high impedance differential relay, or a low impedance differential relay is selectively available so as to confirmly detect a fault in the bus bar.

A voltage-reactive power control apparatus provided together with VAR (volt-ampere reactive) supply equipment at principal points of the power system, such as load area substations. This voltage-reactive power control apparatus monitors the power-flow and load voltage at the load area. The apparatus quickly controls VAR supply equipment etc. upon detecting of voltage abnormalities, information that otherwise would be sent to the control point at a higher level station in the power system upon making decision to provide necessary countermeasures for wider range operation of the power system.

Growing community of inventors

Tokyo, Japan

Makoto Terada