Abstract: A protection relay comprises a digital processing unit including: a first filter to eliminate a DC component in the time-series data, the first filter having a first window length; a second filter to eliminate a DC component in the time-series data, the second filter having a second window length shorter than the first window length; and a coefficient calculation unit to multiply an amplitude value of an output signal of the first filter and an amplitude value of an output signal of the second filter by first and second coefficients respectively, and integrate multiplication results. An operation determination is performed based on an output of the coefficient calculation unit. The first coefficient is decreased and the second coefficient is increased when a failure of the power system is detected, and thereafter, the first coefficient and the second coefficient are changed with a lapse of time.

Abstract: Provided is a gear pump and a gear motor in which noise is reduced. A gear pump includes: gears which mesh and pair with each other; a casing including a gear housing chamber for housing the gears; and at least one hollow layer which is configured in the casing and divides the casing into at least inner walls and outer walls. Coincidence critical frequency of the inner walls and coincidence critical frequency of the outer walls are different. The hollow layer is formed between the gear housing chamber in the casing and an outer surface of the casing.

Abstract: A protection relay comprises a digital processing unit including: a first filter to eliminate a DC component in the time-series data, the first filter having a first window length; a second filter to eliminate a DC component in the time-series data, the second filter having a second window length shorter than the first window length; and a coefficient calculation unit to multiply an amplitude value of an output signal of the first filter and an amplitude value of an output signal of the second filter by first and second coefficients respectively, and integrate multiplication results. An operation determination is performed based on an output of the coefficient calculation unit. The first coefficient is decreased and the second coefficient is increased when a failure of the power system is detected, and thereafter, the first coefficient and the second coefficient are changed with a lapse of time.

Abstract: The disclosure allows a gasket to be securely attached to a gasket groove, reduces a time for an operation of attaching the gasket to the gasket groove, and allows differentiation between gaskets of different materials. A gear pump or a motor, including gears which mesh together and form a pair, axes for pivotally supporting the gears, a body having a gear storing chamber internally for placing the gears, a cover for covering the gear storing chamber of the body, is characterized in that a gasket is disposed between the body and the cover, wherein the gasket is insertable to a gasket groove disposed on at least one of the body and the cover, the gasket groove having a shape surrounding the gear storing chamber, and the gasket sticks closely to the gasket groove due to an elastic restoring force when inserted to the gasket groove.

Abstract: The disclosure allows a gasket to be securely attached to a gasket groove, reduces a time for an operation of attaching the gasket to the gasket groove, and allows differentiation between gaskets of different materials. A gear pump or a motor, including gears which mesh together and form a pair, axes for pivotally supporting the gears, a body having a gear storing chamber internally for placing the gears, a cover for covering the gear storing chamber of the body, is characterized in that a gasket is disposed between the body and the cover, wherein the gasket is insertable to a gasket groove disposed on at least one of the body and the cover, the gasket groove having a shape surrounding the gear storing chamber, and the gasket sticks closely to the gasket groove due to an elastic restoring force when inserted to the gasket groove.