Kabushiki Kaisha Toshiba

Tokyo Shibaura Denki Kabushiki Kaisha

Yasuhiro Kurosawa

Tetsuo Matsushima

Hidenari Amo

Fumio Andow

Mitsuru Yamaura

Akio Takeda

Itsuo Shuto

Takafumi Maeda

Hideyuki Takani

Hiroshi Saito

Hiroshi Yamakawa

Hidenori Amou

A protection relay for determining whether or not a fault point of a power system exists in a predetermined range including a filter section for inputting sampling data of a voltage and a current in the power system to a digital filter having a predetermined transfer function and outputting a first voltage data and a first current data, and a second voltage data and a second current data normal to the first voltage data and the first current data, respectively, a calculator for calculating a predetermined measurement value based on the first and second voltage data, and the first and second current data at a first time and the first and second voltage data, and the first and second current data at a second time different from the first time, and an operation decision section for performing an operation decision based on the predetermined measurement value obtained by the calculator.

Protection relay

A digital distance relay for deciding whether a fault point is within a stipulated operation region by obtaining an impedance to the fault point. The relay comprises: means for deciding whether the impedance is within a specified region by applying a value proportional to the relative phase; and means for deciding the fault point is within the stipulated operation region if: (a) when the load current indicates a sending direction, the positive-phase resistance and reactance are within a stipulated region based on stipulated positive-phase resistance and reactance, and the impedance is decided within the specified region; or (b) when the load current indicates a receiving direction, the positive-phase resistance and reactance are within a stipulated region based on stipulated positive-phase resistance and reactance, or the impedance is decided within the specified region.

Digital distance relay

A short-circuit distance relay has a short-circuit distance relay element that calculates a fault impedance from voltage and current which are introduced from a power system and that compares the fault impedance with a set impedance and uses the fault impedance comparison result within its protection zone. It calculates the amplitudes of the phase-to-phase differences of these voltage amplitudes and a sensitivity constant Vk.

Distance relay equipment

A fault locator of a parallel transmission line includes a data receiving unit that receives the transmission and the received signal of each current differential relay provided with the transmission line, and measures the receiving timing of the transmission signal from a self-terminal. A fault detecting unit judges fault detection on the transmission line based on current data received with the data receiving unit, and outputs a starting signal. A data memory unit stores a predetermined fault generating range of a quantity of electric data of each self-terminal previously stored and an other side terminal when the quantity of electric data of each self terminal received with the data receiving unit and the other side terminal are stored and a starting signal is received. A synchronous correction unit, based on information on the receiving timing measured with the data receiving unit at the time of data reception of a self-terminal transmission signal, performs synchronous correction processing between each line to the stored memory. A setting unit inputs an impedance value and the line-length for three-phases as a setting value. A fault location unit performs fault location, using impedance setting for three-phases and line-length setting which were set with the stored memory data and the setting unit and the synchronous correction processing between each line that was performed in the synchronous correction unit.

Fault locator that uses positive-phase-sequence electricity

Protective relay system provided with difference and addition filters

A frequency detecting method for detecting a frequency of an AC electric parameter of an electric power system. The frequency detecting method comprises a sampling step of sampling the AC electric parameter of the electric power system at a predetermined sampling period, an adding step of adding a sampling value v.sub.m sampled at a sampling time m and a sampling value v.sub.m-n sampled at a sampling time (m-n), thereby obtaining a sum w.sub.m of the sampling values, a first RMS value calculating step of calculating a first electric parameter E1 corresponding to a RMS value of the sum w.sub.m, a second RMS value calculating step of calculating a second electric parameter E2 corresponding to a RMS value of a time-differential value u.sub.m of the sum w.sub.m, a dividing step of dividing the second electric parameter E2 by the first electric parameter E1, and a frequency detecting step of detecting the frequency of the AC electric parameter from a division result (E2/E1).

Method and an apparatus for detecting a frequency of a power system

A digital type distance relay system comprises a sampling and hold circuit for sampling and holding the current in and voltage on a power transmission system, an A/D converter for receiving the outputs of the sampling and hold circuit through a multiplexer and converting the received analog quantities into corresponding digital quantities I and V, and a digital computer. The digital computer includes a data memory for memorizing the current I and voltage V and also a digital voltage V.sub.p having a predetermined relation to the voltage V, a setting memory for memorizing a setting value Z.sub.0 for setting a range of protection of the power transmission system, a ROM for memorizing a program for executing an arithmetic operation according to the formula .vertline.I.multidot.Z.sub.0 +K.sub.1 V.sub.p .vertline.-.vertline.I.multidot.Z.sub.0 -V-K.sub.2 V.sub.p .vertline..gtoreq.K.sub.0 as well as the constants K.sub.1 and K.sub.2 and minimum sensitivity value K.sub.0, and a CPU. The CPU executes the program dealing with the afore-mentioned arithmetic operation formula and produces a command signal for taking an action of protecting the power transmission system if the arithmetic operation formula is satisfied while producing a command signal for taking no protective action if the formula is not satisfied. The protective action can be provided even in case when the voltage V in the arithmetic operation formula is zero in level.

Growing community of inventors

Tokyo, Japan

Yasuhiro Kurosawa