JPH05249175A - Partial discharge measuring instrument - Google Patents

Abstract

PURPOSE:To surely detect partial discharge which occurs in a power transmitting and distributing facility in a state where the partial discharge is completely separated from external noise by averaging a high-frequency current generated by the partial discharge against an AC phase with an averaging process circuit. CONSTITUTION:A high-frequency current generated by partial discharge flows to the earthing conductor 10 of a high-voltage circuit 9 and detected as a current pulse signal A by means of a high-frequency CT 11. The signal A is inputted to an averaging circuit process 7' after the signal A is amplified and detected 1. At the circuit 7', the AC voltage of an AC power source 8 is fetched and the zero-crossing point of the AC voltage is detected 2, and then, the zero-crossing point is inputted to a current pulse detection circuit 4 after the voltage is divided by means of split-phase cells. Then the signal A is superimposed 4 upon the split-phase cells and the presence/absence of current pulse signals is discriminated at every split-phase cell. The circuit 4 is reset and detects the signal A in the next cycle at measuring time intervals fixed by means of a measuring time interval measurement circuit 5 in advance. The circuit 4 repeats the measurement cycle a plurality of times. Finally, the averaging processing section 7' of a personal computer finally discriminates high-frequency power supply pulses generated by partial discharge by obtaining an average value by dividing a sum by the number of repeating times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a partial discharge measuring device for detecting and measuring partial discharge generated in power transmission and distribution equipment.

[0002]

2. Description of the Related Art In order to detect a partial discharge generated in a power transmission and distribution facility, a high frequency current flowing through a ground line is usually detected by a high frequency CT or a Rogowski coil. Since the waveform is similar to that of the partial discharge pulse, malfunction often occurs in the partial discharge measurement. Therefore, in order to minimize the influence of this external noise ,. Bridge balance method (eg, Japanese Patent Publication No. 60-29075, "Partial discharge test method"). Polarity discrimination method (eg, Institute of Electrical Engineers of Japan, Electrical Discharge Research Group Material ED-8
1-34 "Improvement of partial discharge detection sensitivity by logic control noise discriminator"). Electromagnetic pulse, ultrasonic pulse synchronization method (eg Japanese Patent Publication Sho 63
Many techniques have been developed, such as Japanese Unexamined Patent Publication No. 26609- "Partial discharge monitoring device"). However, there is no decisive method for reducing external noise, and it is the current situation that these methods are combined according to the purpose to minimize the influence of noise. The balance method and the polarity discrimination method have many drawbacks such as adjustment of resistance value and capacitance or a complicated circuit.

Therefore, the applicant of the present invention has found that a commutation pulse generated from an uninterruptible power supply device using a thyristor element for OA equipment, which is prevalent in an intelligent building, enters a measurement system for partial discharge pulses as external noise. In such a case, an invention that enables removal or reduction of external noise by detecting and measuring a partial discharge pulse from the ground wire of a transformer or a gas switchgear installed in the same building (Japanese Patent Application No. 3-
No. 205364 invention "partial discharge measuring device").

[0004]

However, since the invention "partial discharge measuring device" uses the fact that external noise is commonly detected by the low-voltage power line and the ground line, the invention is not transmitted through the power line. The external noise that directly enters the high-voltage equipment and the external noise due to the air propagation do not have a constant generation phase and are not detected by the low-voltage power line, so the external noise may not be sufficiently processed.

The present invention eliminates the above-mentioned drawbacks of the conventional partial discharge measuring apparatus and completely separates the partial discharge generated in the power transmission and distribution equipment from the external noise with a simple circuit structure and reliably detects the partial discharge. ..

[0006]

The present invention is a method of reducing external noise which is an obstacle to partial discharge measurement using a high frequency CT from a ground line, and a partial discharge is generated at a substantially constant phase with respect to an AC phase. On the other hand, attention is paid to the point that external noise enters in an irregular phase, and the averaging processing circuit averages the AC phase to reduce the influence of external noise.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The partial discharge measuring apparatus of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram of a partial discharge current pulse detection apparatus which is an embodiment of the present invention. In the figure, 1 is a detection amplification circuit for amplifying and detecting the current pulse signal A detected by the high frequency CT 11 from the ground line 10 of the high voltage circuit, 2 is an AC zero cross point detection circuit for detecting the AC zero cross point of the AC power supply 8, 3 is a phase division circuit that divides one cycle of the detected AC power supply into 64, and 4 is a current pulse for each divided phase cell that is superposed with the detected current pulse in 64 divided phase cells, Current pulse detection circuit for counting, 5 is a measurement time interval measuring circuit for determining an interval of measurement time (1 cycle), 6 is a memory adding circuit for adding and storing the current pulse detecting circuit for each divided phase cell, and 7 is a current The personal computer is composed of an averaging processing unit 7'for averaging the number of pulse detections for each divided phase cell, an output display unit 7 ", and a control unit for controlling them.

Next, the operation of the partial discharge current pulse detection device of FIG. 1 will be described with reference to Table 1 and FIGS.

The high frequency current due to the partial discharge is applied to the high voltage circuit 9
Flowing through the ground line 10 and detected as a current pulse signal A by the high frequency CT 11. The detected current pulse signal A is amplified and detected by the detection amplification circuit 1 and input to the averaging processing circuit. In the averaging circuit, the AC voltage of the AC power supply 8 is taken in parallel with the input of the current pulse A, the zero-cross point of the AC voltage is detected by the AC zero-cross point detection circuit 2, and the zero-cross point is used as a reference to detect the AC voltage. 1
The cycle is divided into, for example, 64 to form a divided phase cell, which is input to the current pulse detection circuit 4.

In the current pulse detection circuit 4, the current pulse signal A is superimposed on the divided phase cells, and the peak phase is held for each divided phase cell to determine the presence or absence of the current pulse signal for each divided phase cell. (See Figure 2).

The current pulse signal peak-peaked for each divided phase cell is compared with the threshold voltage level, and added to the current pulse signal above the threshold voltage level to be stored. In this way, when the detection of the current pulse signal for one cycle and the addition and storage for each divided phase cell are completed, the current pulse detection circuit 4 is reset and the measurement time interval measurement circuit 5 performs the measurement at the predetermined measurement time interval. Next cycle as shown in 2 (second cycle)
The current pulse signal A is detected and is sequentially repeated, for example, up to 60 cycles. Table 1 shows the averaging processing value for each divided phase cell which is averaged by the detection circuit for each divided phase cell and the personal computer 7.

[0013]

[Table 1]

In the example shown in Table 1, repeated measurement was performed.
This is performed 60 times and the current pulse signal detection circuit is added.
Then, the added value is divided by the number of repetitions to obtain an averaged value.

FIG. 3 shows an output example after the averaging process. The averaging process value for each divided phase cell shown in Table 1 is shown on one cycle of the AC power supply. If the value is equal to or higher than the threshold level (hatched part), it is judged as "partial discharge".

The averaged output value is displayed on the output display section 7 "composed of a CRT or a display. Further, the data can be transmitted to a high-order computer or the like via a transmission circuit. Repeated measurement such as is continued even if it exceeds 60 times, and the oldest cycle (one time) data is removed every time a new one cycle (61 times) data is processed, and 60 times (60 times) It is possible to obtain the averaged processing value based on the data for (cycles) and display it in a scrolling manner. The time interval can be appropriately determined such as 0.5 to 5 seconds.

[0017]

As described above, according to the present invention, the intruding partial discharge current pulse is averaged for each divided phase. Therefore, according to the present invention, the external noise having an irregular phase is generated. By averaging, it becomes a very small value and it is easy to remove, and the partial discharge current pulse generated in almost constant phase does not change in size even if averaged, so partial discharge can be measured efficiently. can do.

Further, since the averaging process of the present invention is performed for each divided phase of the AC power source, the generation phase of partial discharge can be measured and the cause of partial discharge generation can be specified. Furthermore, unlike the conventional balancing method or polarity discrimination method, it does not require adjustment of resistance value or capacitance or complicated circuit, and it is possible to reduce external noise with a simple circuit that divides the phase of the AC power supply, and partial discharge is prevented. It can be measured with high efficiency.

[Brief description of drawings]

FIG. 1 Partial discharge current pulse detection block diagram

FIG. 2 Example of current pulse input on a split phase cell

FIG. 3 Output example of averaging processing

[Explanation of symbols]

 1: Detection amplification circuit 2: AC zero chronos check circuit 3: Phase division circuit 4: Current pulse detection circuit 5: Measurement time interval measurement circuit 6: Memory-addition circuit 7: PC

Claims (1)

[Claims] 1. A current pulse detecting means for detecting a high frequency current pulse flowing in a ground wire of a high-voltage circuit device in a power transmission and distribution facility, and a phase dividing means for subdividing one cycle of an AC power supply voltage to produce a divided phase cell. , A current pulse measuring means for measuring the high frequency current pulse for each divided phase cell by superposing the high frequency current pulse on the divided phase cell for a plurality of times with a predetermined time interval, and a power supply measured for each divided phase cell A digital processing means for comparing the magnitude of the pulse with the threshold level and processing as "1" above the threshold level and "0" below the threshold level, and the data ("1" in each divided phase cell). Alternatively, "0") is added by the number of times of the measurement cycle, and the added value is divided by the number of times of the measurement cycle, and each divided phase sequence. Based on the division result for each, and determination means for determining said current pulses, characterized in that it consists of capital the partial discharge measuring device.