JP3104403B2 - Partial discharge determination method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining a partial discharge used in measuring a partial discharge of a power cable line.

[0002]

2. Description of the Related Art In partial discharge measurement in a conventional insulation diagnosis method for power cable lines, a noise removal technique has become extremely important. Various methods have been known so far, and the pulse number control method and the noise window method are one of them. For example, IEEJ Technical Report (Part II) No. 222
No. 19, April 1986, the pulse number control method as a noise elimination technique using an instruction circuit is a method of directly instructing a charge value corresponding to a predetermined frequency of occurrence. In the noise window method, when one or more discharges having a predetermined size or more are generated in five consecutive half cycles, the size is instructed. It has been reported that these techniques can measure partial discharge pulses in external noise.

[0003]

According to the pulse number control method, if a partial discharge has occurred, the discharge charge can be measured with S / N <1 smaller than the external noise. It is limited by saturation, and does not provide a reference for determining whether or not partial discharge has occurred from information of a plurality of detected pulses.

The above-mentioned noise window method is effective when at least one or more pulses are generated in each half cycle during a measurement period of five half cycles, for example.
Even when a partial discharge occurs continuously, a pulse is not always generated continuously over several cycles, and cannot always be a highly accurate criterion.

It is an object of the present invention to provide a simple partial discharge determination method for reliably determining whether or not a partial discharge has occurred.

[0006]

SUMMARY OF THE INVENTION The present invention provides a method for determining whether or not a partial discharge has occurred in a partial discharge measurement of a power cable line. The number of generated pulses N ₁ and N ₂ are counted, and the difference N ₁ −
N ₂ is also determined at the same time, these three pulses from the count number of the relationship (1) the number of pulses N ₁ generated in the cycle of the positive set value n ₁ or more, and (2) the number of pulses N occurring in a negative cycle _It is determined that partial discharge has occurred only when the condition that ₂ is equal to or greater than the set value n ₂ and (3) the absolute value N ₃ of the difference N ₁ −N ₂ between the two pulse count numbers is equal to or less than the set value n _3. Partial discharge discrimination method in which the output is output and measured.

[0007]

[Action] predetermined time, the division voltage pulse number N ₁ of the positive and negative cycles have occurred in the phase, N ₂ with each count, also determined at the same time the difference N ₁ -N ₂ thereof counts, these three types of pulse pulse number n ₁ generated from the count number of the relationship in the positive cycle setpoint n ₁ or more, and the difference n ₁ number of pulses n ₂ generated in the negative cycle set value n ₂ or more, and the number of both pulse count lies in that it is determined that only the partial discharge when the condition that the absolute value n ₃ of -N ₂ set value n ₃ below are satisfied occurs. This, together with voltage application voltage is counted separately pulses N ₂ generated in the pulse N ₁ and the negative period that occurred in the positive period, by taking the difference between N ₁ -N ₂ thereof counts, partial This is to take in information that the frequency of occurrence of the discharge pulse is substantially equal between positive and negative cycles.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit configuration of a method for determining partial discharge of a power cable line according to an embodiment, and FIG. 2 is a time chart of the circuit portion. That is, a voltage is applied to the power cable 2 to be measured by the charging transformer 1, and a partial discharge is detected by the electrode 4 attached to the insulating connection 3. When a partial discharge occurs, a signal detected by the detection impedance 5 connected to the electrode 4 is amplified by the amplifier 6 and input to the gate circuits 7 and 8. This detection signal is shown in FIG.
However, in the present invention, any signal detection method may be used.

On the other hand, FIG. 2B shows the applied voltage phase information obtained from the tertiary winding 9 of the power application transformer 1. This signal passes through a gate circuit 10 to output gate control signals 11 and 12 during each half cycle in which positive and negative voltages are applied. These control signals 11 and 12 are shown in FIGS. The gate circuits 7 and 8 pass the signal for each half cycle in which the signal is at the H level according to whether the gate control signals 11 and 12 are at the H level or the L level shown in FIGS. It does not pass during the L level period. Accordingly, the time charts of the gate circuits 7 and 8 are as shown in FIGS. That is, the on / off of the gate circuits 7 and 8 is reversed.

The pulse counters 13 and 14 connected to the gate circuits 7 and 8 respectively count the number of pulses for a predetermined time. Here, the pulse counters 13 and 14
Control (measurement time setting, measurement start timing signal)
Is performed by inputting a counter control signal 16 from the computer 15. After the measurement is completed, each pulse counter 13, 14
Pulse count number are collected and output to the computer 15 connected thereto, the set value n ₁ applied voltage positive pulses have occurred during cycle N ₁ and the pulse number N ₂ which occurs during the negative cycle And the set value n ₂ and the absolute value N ₃ = | N ₁ −N ₂ | of the difference between the pulse count number and the set value n ₃ are compared. And N ₁ ≧ n ₁ and N ₂ ≧ n
Only when ₂ and N ₃ ≦ n _3, the output is made assuming that the partial discharge is detected.

For example, in the time chart shown in FIG. 2, measurement of five cycles will be described as an example. Now, FIG.
Assume that six output pulses are generated at the gate 7 and eight output pulses are generated at the gate 8 as shown in (F) and (H).
Assuming that the set values are n ₁ = n ₂ = 6 and n ₃ = 2, the number N _{1 of} pulses generated during a positive cycle of the applied voltage N ₁ = 6 ≧ n ₁
It is. In addition, the number of pulses N ₂ = 8 ≧ n ₂ generated during a cycle in which the applied voltage is negative. Then, the absolute value N ₃ = 2 ≦ n ₃ of the difference between the pulse count numbers is established. In this measurement method, information that the frequency of occurrence of the partial discharge pulse is substantially equal in the positive and negative cycles is taken into the discrimination. In this case, it is output that partial discharge has occurred.

Next, an example in which the present invention is realized by a hardware configuration will be described with reference to FIG. That is, the output of the amplifier 6 connected to the detection impedance 5 is applied to the gate circuits 7 and 8.
And up / down counter 20. Pulse counters 13, 1 connected to gate circuits 7, 8, respectively.
Reference numeral 4 counts the number of pulses, and when the count exceeds a predetermined count, the output changes from L level to H level. The up-down pulse counter 20 adds (up-counts) the number of pulses generated during the positive cycle of the applied voltage and subtracts (down-counts) the number of pulses generated during the negative cycle.
Is what you do. When the absolute value of the total count is greater than a predetermined count, the output is H level, and when the absolute value is less than the predetermined count, the output is L level. An AND circuit 21 is connected to the pulse counters 13 and 14 and the up / down counter 20, and the AND circuit 21
The logical product of the outputs of 3, 3, and the up / down pulse counter 20 is obtained. Then, the result is displayed on display 2.
2 is displayed.

On the other hand, when a predetermined number of cycles have elapsed, a reset signal is output from the reset circuit 23 connected to the gate control circuit 10, and this output is output to the pulse counter 13,
14 and an up / down pulse counter 20 so as to reset the number of pulses to zero.

FIG. 4 shows a pulse count for a period of 5 cycles, where the number of pulses in the positive cycle is 6 or more, the number of pulses in the negative cycle is 6 or more, the number of pulses in the positive cycle and the number of pulses in the negative cycle. 6 is a time chart showing the result of determining the occurrence of partial discharge under the condition that the difference in the number of pulses is 2 or less. (A) is a detection signal of the detection impedance 5 in order from the top, (B) is an applied voltage of the transformer tertiary winding 9, (C) is a gate control signal 11 from the gate control circuit 10, (D)
Is a gate control signal 12 from the gate control circuit 10,
(E) ON / OFF of the gate circuit 7, (F) output of the pulse counter 13, (G) ON / OFF of the gate circuit 8, (H) output of the pulse counter 14, (I) up / down. The output of the counter 20, (J) is the AND circuit 21
(K) is a reset signal from the reset circuit 23. That is, since the output of the AND circuit 21 immediately before the reset signal is output is at the H level, it is determined that partial discharge is present in this case.

[0014]

As described above, according to the partial discharge determination method of the present invention, it is possible to quickly and accurately determine that partial discharge has begun to occur continuously. This is a method of counting the number of pulse generations by separately counting the pulses generated during the positive period and the pulses generated during the negative period, and taking the difference between the count numbers to obtain the partial discharge pulse. This is because information that the frequency of occurrence of ほ ぼ is substantially equal in the positive and negative cycles is included in the determination.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a method for determining partial discharge of a power cable line according to the present invention;

FIG. 2 is a time chart for explaining an operation state of the circuit in FIG. 1;

FIG. 3 is a circuit diagram showing another embodiment of the method for determining partial discharge of a power cable line according to the present invention;

FIG. 4 is a time chart for explaining an operation state of the circuit of FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Power transfer transformer 2 Power cable 3 Insulated connection part 4 Detection electrode 5 Detection impedance 6 Amplifier 7,8 Gate circuit 9 Transformer tertiary winding 10 Gate control circuit 11,12 Gate control signal 13,14 Pulse counter 15 Computer 16 Counter control Signal 20 Up / down pulse counter 21 AND circuit 22 Display 23 Reset circuit

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tomoaki Imai 5-1-1, Hidaka-cho, Hitachi City, Ibaraki Prefecture “Inside Power System Research Laboratories, Hitachi Cable Ltd.” (56) References 109181 (JP, A) JP-A-3-246473 (JP, A) JP-A-1-219677 (JP, A) JP-A-56-37569 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01R 31/12

Claims (1)

(57) [Claims] 1. A method for determining whether a partial discharge has occurred in a partial discharge measurement of a power cable line,
For a predetermined time, the number of pulses N ₁ and N ₂ generated in the positive and negative cycles of the application voltage phase are counted, and the difference N ₁ −N ₂ between the counted numbers is also calculated.
From the class of the pulse count number of relations (1) the number of pulses N ₁ generated in the cycle of the positive set value n ₁ or more,
(2) The number of pulses N ₂ generated in the negative cycle is equal to the set value n.
₂ or more, and (3) the difference between the two pulse count numbers N ₁ −N
Partial discharge determination _{method 2} of the absolute value N _3, characterized in that only the partial discharge when the condition that the set value n ₃ below is satisfied is to measure out the output is determined to have occurred.