Provided herein are approaches for determining a status of a fuse or relay. In some embodiments, a system may include a first fuse or relay connected between a first input and a first output, and an optocoupler electrically connected with the first fuse or relay, wherein the optocoupler is operable to monitor a differential voltage of the first input or the first output. The system may further include an input/output (IO) expander receiving a status signal representing a state of the first fuse or relay, wherein only a single input port of the IO expander receives the status signal representing the state of the first fuse or relay.

An optical voltage prove includes: an optical modulator 1 having two modulation electrodes 11 and 12, the optical modulator 1 being configured to modulate an intensity of an incident light depending on a voltage between the two modulation electrodes and output the incident light which is modulated; an input/output optical fiber 2 connected with the optical modulator 1; two contact terminal attachment portions 5, 6 to which contact terminals 3, 4 can be detachably attached and contacted, the two contact terminals 3, 4 being configured to be in contact with the points to be measured, the two contact terminal attachment portions 5, 6 being respectively connected with the modulation electrodes 11, 12; and a package 8 that houses the optical modulator 1 and a part of the input/output optical fiber 2. A voltage signal induced via the contact terminals 3, 4 is converted into an optical intensity modulation signal. When an electric wave having a measurement frequency is applied while the contact terminal attachment portions 5, 6 are opened, the package 8 exhibits a shielding effect of attenuating the electric wave by 15 dB or more compared to an output signal intensity measured without providing the package.

An optical voltage prove includes: an optical modulator 1 having two modulation electrodes 11 and 12, the optical modulator 1 being configured to modulate an intensity of an incident light depending on a voltage between the two modulation electrodes and output the incident light which is modulated; an input/output optical fiber 2 connected with the optical modulator 1; two contact terminal attachment portions 5, 6 to which contact terminals 3, 4 can be detachably attached and contacted, the two contact terminals 3, 4 being configured to be in contact with the points to be measured, the two contact terminal attachment portions 5, 6 being respectively connected with the modulation electrodes 11, 12; and a package 8 that houses the optical modulator 1 and a part of the input/output optical fiber 2. A voltage signal induced via the contact terminals 3, 4 is converted into an optical intensity modulation signal. When an electric wave having a measurement frequency is applied while the contact terminal attachment portions 5, 6 are opened, the package 8 exhibits a shielding effect of attenuating the electric wave by 15 dB or more compared to an output signal intensity measured without providing the package.

A method and device for monitoring a measurement object. A passive unit has a light source, which radiates radiated light modulated by at least one external measurement influence from the measurement object. An active unit has an optical detector, which receives the radiated and modulated light via an optical link. In addition, there is a transmitter unit emitting energy, such as optical energy, sound energy, electromagnetic energy etc. The emitted energy is coded by an energy signature and sent to the passive unit via an energy link. The passive unit receives the emitted energy by a receiver unit, which decodes the energy signature and moderates the radiated and modulated light in dependence of the energy signature. The received energy is also used to drive the light source. A processor unit may decode the signal for discriminating the signal from error sources.

A method and device for monitoring a measurement object. A passive unit has a light source, which radiates radiated light modulated by at least one external measurement influence from the measurement object. An active unit has an optical detector, which receives the radiated and modulated light via an optical link. In addition, there is a transmitter unit emitting energy, such as optical energy, sound energy, electromagnetic energy etc. The emitted energy is coded by an energy signature and sent to the passive unit via an energy link. The passive unit receives the emitted energy by a receiver unit, which decodes the energy signature and moderates the radiated and modulated light in dependence of the energy signature. The received energy is also used to drive the light source. A processor unit may decode the signal for discriminating the signal from error sources.

The current transformer system that is the present invention allows for surveillance of an electronic grid at electrical power generating stations, at individual operational substations and in electric power distribution for electric network and grid measurement, protection, and control ranging from very low currents to high current magnitudes. The reception and relay of information from the CT primary circuit is sensed and transmitted by a primary electronic circuitry, digitized, converted to a fiber optic mode, transmitted to a secondary electronic circuit, processed and converted to a digital output and transmitted to various monitoring and recording devices.

Provided are a voltage measurement method and apparatus. The method includes following steps: a number j of height values are selected in a vertical direction of a transmission line, a number m of sensors used for measuring, according to a Stark effect, electric field strength of a corresponding spatial position are arranged in sequence at each of j spatial positions of the j heights from the ground, electric field strength values of the corresponding spatial position are measured through the m sensors respectively, and an electric field strength average value of the corresponding spatial position is calculated according to the acquired m electric field strength values, where j and m are positive integers, and the j spatial positions are below the transmission line; a voltage of the transmission line is calculated according to j electric field strength average values.

A partial discharge (PD) transducer that includes a PD sensor configured to sense a PD event of an electrical system. At least one light emitting device (LED) is arranged in series with the PD sensor. The LED is configured to receive the electrical sensor signal from the PD sensor and to generate a light signal in response to the electrical sensor signal.

A partial discharge (PD) transducer that includes a PD sensor configured to sense a PD event of an electrical system. At least one light emitting device (LED) is arranged in series with the PD sensor. The LED is configured to receive the electrical sensor signal from the PD sensor and to generate a light signal in response to the electrical sensor signal.

A partial discharge (PD) transducer that includes a PD sensor configured to sense a PD event of an electrical system. At least one light emitting device (LED) is arranged in series with the PD sensor. The LED is configured to receive the electrical sensor signal from the PD sensor and to generate a light signal in response to the electrical sensor signal.