摘要:
A method for assessing insulation deterioration in a live underground power cable may include, in one embodiment, attaching a coupling device to a live underground power cable and using the coupling device to couple a test signal onto the power cable. The power cable may carry a normal AC power signal at a first frequency, while the test signal may have a second frequency different from the first frequency. The test signal may be detected after it has traveled a distance along the power cable. It may then be analyzed to determine a change in velocity and/or attenuation of the test signal as a function of the normal AC power signal. The severity of water trees in the power cable may be inferred based on the magnitude of the change.
摘要:
A method for assessing insulation deterioration in a live underground power cable may include, in one embodiment, attaching a coupling device to a live underground power cable and using the coupling device to couple a test signal onto the power cable. The power cable may carry a normal AC power signal at a first frequency, while the test signal may have a second frequency different from the first frequency. The test signal may be detected after it has traveled a distance along the power cable. It may then be analyzed to determine a change in velocity and/or attenuation of the test signal as a function of the normal AC power signal. The severity of water trees in the power cable may be inferred based on the magnitude of the change.
摘要:
Provided are various embodiments of an adjustment circuit, having a base layer and a piezoelectric layer juxtaposed relative to the base layer and including a first electrode such that when the piezoelectric layer is stressed a polarization charge appears between the base layer and one side of the piezoelectric layer and an opposite polarization charge appears on an opposite side of the piezoelectric layer.
摘要:
Provided are various embodiments of an adjustment circuit, having a base layer and a piezoelectric layer juxtaposed relative to the base layer and including a first electrode such that when the piezoelectric layer is stressed a polarization charge appears between the base layer and one side of the piezoelectric layer and an opposite polarization charge appears on an opposite side of the piezoelectric layer.
摘要:
An apparatus for measuring concentrations of airborne particulate matter may include, in one embodiment, a primary channel to receive air samples from the external environment. The air samples include particles of varying sizes. A microfluidic circuit communicates with the primary channel and small particles (having a size less than a threshold size) are diverted around a bend into a secondary channel. Remaining larger particles are unable to make the bend and continue through the primary channel. A mass-sensitive element communicating with the secondary channel includes a collection surface to collect the small particles. A resonant frequency of the mass-sensitive element is reduced in proportion to the mass of the particles collected.
摘要:
An apparatus for detecting a faulty concentric neutral wire in a live power distribution cable may include, in one embodiment, a housing for sliding along a surface of a power distribution cable, a magnetic sensor, and a motion device. The magnetic sensor may be coupled to the housing and configured to detect a magnetic field produced by each concentric neutral wire as the housing moves along the surface of the cable. The motion device may also be coupled to the housing, and may detect motion of the housing relative to the cable. In some embodiments, a communication device may communicate data describing the magnetic field and motion to a destination device.
摘要:
An apparatus for measuring concentrations of airborne particulate matter may include, in one embodiment, a primary channel to receive air samples from the external environment. The air samples include particles of varying sizes. A microfluidic circuit communicates with the primary channel and small particles (having a size less than a threshold size) are diverted around a bend into a secondary channel. Remaining larger particles are unable to make the bend and continue through the primary channel. A mass-sensitive element communicating with the secondary channel includes a collection surface to collect the small particles. A resonant frequency of the mass-sensitive element is reduced in proportion to the mass of the particles collected.