Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
  • G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
  • G01R15/24—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using light-modulating devices
  • G01R15/245—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using light-modulating devices using magneto-optical modulators, e.g. based on the Faraday or Cotton-Mouton effect
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R21/00—Arrangements for measuring electric power or power factor
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R22/00—Arrangements for measuring time integral of electric power or current, e.g. electricity meters
  • G01R22/06—Arrangements for measuring time integral of electric power or current, e.g. electricity meters by electronic methods

Definitions

• a system for sensing current on a conductor and outputting to a meter includes an optical module including a light source for directing an optical signal in an optical path around the conductor and producing an optical module signal correlating to the current through the conductor.
• a cutout module receives the optical module signal and outputs a cutout module signal to the meter.
• the cutout module is adapted to output the optical module signal as the cutout module signal if the optical module signal is above a threshold value.
• the cutout module is adapted to output zero voltage as the cutout module signal if the optical module signal is below said threshold value.
• Figure 3 is a function block schematic of the Low Input Cutout module according to the present invention.
• a polarized light source (LED 18) travels through an optical path (rotator 20) around a conductor 22 to be measured.
• the light is then received at a sensor (PIN diode 24) where the rotation of the polarized light is be measured.
• the polarized light is measured as a 60 Hz modulation of the input light intensity.
• the signal from PIN diode 24 is output to a transimpedance amplifier 26.
• the PIN diode converts light into electrons which creates a flow of current.
• the transimpedance amplifier converts the current to a voltage.
• the signal from the transimpedence amplifier 26 is output to a compensator 28.
• the intensity of the light is controlled by a feedback control system.
• the compensator keeps the light intensity loop stable, the output of which drives LED 18.
• the signal from the transimpedance amplifier 26 is also output to an amplifier 30.
• the amplifier 30 outputs a 2 volt RMS signal at rated current (of the power line to be monitored).
• the pin diode 24, transimpedance amplifier 26, compensator 28, LED 18 and amplifier 30 each physically reside on a phase card 32.
• Meters incorporating an MOCT typically measure three phase power distribution, and thus three separate phase cards 32, performing three separate optical measurements (one on each phase), are used.
• the signal from amplifier 30 from each phase card 32 is output to digital PCB 12.
• the digital PCB 12 outputs to the LIC module 14 the phase A, B, and C low level voltage signals that are proportional to the respective phase current. It should be appreciated, however, that digital PCB 12 functions merely as a pass-through or router of the signal from the optical module 10. Thus, the digital PCB 12 does not appreciably modify the signal.
• the output signal from optical module 10 may be directly connected to the LIC module 14.
• the LIC module 14 includes three identical and independent circuits that continuously process the phase A, B, and C signals from optical module 10 (either received directly from the optical module 10 or through the digital PCB 12). Each LIC phase circuit outputs to an individual phase amplifier 16 which amplifies the signal and transmits it to the energy sensor or meter.
• Each phase circuit in the LIC 14 includes a narrow band pass active filter 34.
• the filter 34 is set at 60 Hz with a Q equal to 12, which provides a ⁇ 5 Hz bandwidth (for power line 22 frequencies of 60Hz).
• the band pass active filter may be adjusted to match the power line 22 frequency and may have Q values from 1 to 25.
• the output of the filter 34 drives an RMS to DC converter 36, which further filters the total RMS input into a DC value.
• the output of the RMS to DC converter 36 drives a comparator 38.
• the comparator 38 switches its output at a DC signal level corresponding to a minimum threshold value.
• the threshold value is the DC signal corresponding to 0.5% of the rated phase current of power line 22.
• the threshold value is the DC signal corresponding to 1 % of the rated phase current of the power line 22.
• the threshold value is the DC signal corresponding to 0.25% of the rated phase current of the power line 22.
• the wideband white noise present during a zero current condition at the input to the LIC module 14 has an approximate value of 5 mV RMS from DC for a 1 kHz 1000 A rated MOCT system.
• the narrowband filters 18 of the LIC module 14 reduce this noise level to approximately 0.5 mV RMS. If the rated current signal has an amplitude of 2 volts, for the exemplary embodiment wherein the threshold is 0.5% of rated current) the 0.5% rated current signal has an amplitude of 10 mV RMS. Therefore, the LIC module filtering yields an RMS signal to noise ratio of 20 and provides reliable switching at this level of input.
• a portable computer diskette a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a transmission media such as those supporting the Internet or an intranet, or a magnetic storage device.
• Computer program code or instructions for carrying out operations of the present invention may be written in any suitable programming language provided it allows achieving the previously described technical results.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Measuring Instrument Details And Bridges, And Automatic Balancing Devices (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (5)

Cited By (1)

Citations (2)

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• 2010
  • 2010-12-09 EP EP10790504.4A patent/EP2510365B1/en not_active Not-in-force
  • 2010-12-09 US US12/964,392 patent/US9664712B2/en active Active
  • 2010-12-09 WO PCT/US2010/059715 patent/WO2011072139A1/en active Application Filing
  • 2010-12-09 CA CA2783295A patent/CA2783295C/en active Active
  • 2010-12-09 CN CN201080056063.9A patent/CN102687025B/zh active Active

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