JP3385602B2 - Current detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distribution line current detection device for detecting line current and fault current flowing in a distribution line. 2. Description of the Related Art A conventional current detecting device transmits an electric signal output from a light emitting element driving circuit 1 to a converting circuit 2 for converting the electric signal into an optical signal as shown in FIG. An optical signal is transmitted via an optical fiber 3 to an optical current detection sensor 4 provided on a distribution line (not shown). The optical current detection sensor measures the line current of the distribution line, and also measures the fault current such as overcurrent, and transmits the measurement signal to the optical fiber 3.
The measured optical signal is transmitted to a conversion circuit 5 via an analog signal, and the measured optical signal is converted into an electric signal. The noise is removed by a filter 7 through an amplifier 6. The output from the rms calculator is compared by a comparator 9 to determine whether or not an overcurrent is present and displayed on the display device 10, and the output from the rms calculator is used as the measured value of the line current. It was output to the display device 11 as an output signal. FIG. 4 is a waveform of a signal in the current detection device, and a is a waveform detected by the optical current detection sensor 4. When an overcurrent flows in the distribution line, the amplitude of the waveform increases. The waveform b is output from the filter 7, and since a filter having a high degree of selectivity is used, the amplitude of the waveform due to the accident gradually increases and becomes the waveform of the accident after the elapse of the filter delay time. c is a waveform output from the effective value calculator 8 and becomes a signal level of an accident after a lapse of a delay time from a normal signal level. d is a waveform output from the comparator 9, and outputs a detection signal after a delay time has elapsed after the occurrence of the accident. However, in the conventional method, a filter having high selectivity is used in order to improve the measurement accuracy of the measured value of the line current, and it takes time to detect accident information. There was a problem that an accident could not be detected instantaneously. Therefore, an object of the present invention is to improve the detection speed of accident information without impairing the measurement accuracy of line current information. [0004] To solve the above problems SUMMARY OF THE INVENTION The present invention provides an optical type current detection sensor provided in the distribution line, before
The optical signal detected by the optical recording current detection sensor is
And a conversion circuit for converting the signal from the conversion circuit into a signal.
An amplifier to be amplified, and a filter for inputting the signal of the amplifier.
Filter and the effective value of the signal from the filter
A value calculation circuit and a signal of the effective value calculation circuit are set in advance.
A comparator for comparing the set value with the set value.
In the current detection device for detecting the line current information and accident information of the distribution line by the detection signal of the detection sensor, the amplification
One of the signals from the filter to the low selectivity filter and the other
Connect to each of the filters with high selectivity, and
Effective value calculation circuit that calculates effective value and outputs line current information
Each is connected . According to the above means, the line current information can be measured with high accuracy using a filter with high selectivity, and the fault information can be measured at high speed with a filter with low selectivity. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of the current detection device, and FIG. 2 is a waveform diagram of signals in the current detection device. The same components as those in FIG. 3 are denoted by the same reference numerals, and detailed description is omitted. Reference numeral 12 denotes a filter with low selectivity, which removes noise from the output signal from the amplifier 6 in a short time and outputs the signal to the effective value calculator 13. This effective value calculator performs an effective value calculation on the signal from the filter 12 and outputs the signal to the comparator 14. The comparator compares the current with a certain current value.If the current value is within the certain current value, it indicates that normal current is flowing.If the current value exceeds the certain current value, it indicates that fault current is flowing. Display at 10. A high-selectivity filter 15 removes noise from the output signal from the amplifier 6 with high accuracy and outputs the result to the effective value calculator 16. This effective value calculator performs an effective value calculation on the signal from the filter 15 and outputs the calculation result to the display device 11. FIG.
Is the waveform of the signal in the current detection device, a is the waveform detected by the photocurrent detection sensor 4, and when an overcurrent flows through the distribution line, the amplitude of the waveform increases. "e" is a waveform output from the filter 12, and since a filter having a low selectivity is used, the amplitude of the waveform due to the fault current increases almost simultaneously with the occurrence of the fault, resulting in a fault waveform. Since f is a waveform output from the filter 15 and uses a highly selective filter, the waveform becomes an accident waveform after a certain delay time has elapsed since the occurrence of the accident. g is the output waveform of the effective value calculator 13, and the current level changes from the normal level to the accident level almost simultaneously with the occurrence of the accident. h becomes an accident waveform after a certain delay time which is an output waveform of the effective value calculator 16 elapses. i is the comparator 1
In the output waveform of FIG. 4, the fact that an accident current flows with a short delay time from the occurrence of the accident is output to the display device 10 to indicate the occurrence of the accident. As described above, according to the present invention, line current information is measured with high accuracy using a filter having high selectivity.
Since accident information is measured at high speed using a filter having low selectivity, high-accuracy measurement of line current information and high-speed measurement of accident information can be performed simultaneously.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of a current detection device according to the present invention; FIG. 2 is a waveform diagram of FIG. 1; FIG. 3 is a circuit diagram of a conventional current detection device; FIG. [Description of Signs] 1 drive circuit 2 conversion circuit 3 optical fiber 4 optical current detection sensor 5 conversion circuit 6
Amplifier 7 Filter 8 Effective value calculator 9 Comparator 10, 11 Display device 12 Filter 13
RMS calculator 14 Comparator 15 Filter 16 RMS calculator

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G01R 19/00-19/32 G01R 31/02-31/06

Claims (1)

(57) Patent Claims 1. A light type current detection sensor provided in the distribution line, before
The optical signal detected by the optical recording current detection sensor is
And a conversion circuit for converting the signal from the conversion circuit into a signal.
An amplifier to be amplified, and a filter for inputting the signal of the amplifier.
Filter and the effective value of the signal from the filter
A value calculation circuit and a signal of the effective value calculation circuit are set in advance.
A comparator for comparing the set value with the set value.
In a current detection device for detecting line current information and accident information of a distribution line based on a detection signal of an output sensor , one of signals from the amplifier has a low selectivity filter.
Then, connect the other to each of the filters with high selectivity, and
A current detection device, characterized in that an effective value calculation circuit that calculates an effective value and outputs line current information is connected to a subsequent stage .