JPH0454464A - Diagnostic device for insulation deterioration of live-line - Google Patents

Abstract

PURPOSE:To obtain a maximum electric discharge, increment amount of loss angle and increment amount of charge current by measuring a local discharge pulse. CONSTITUTION:The local discharge pulse is detected by a discharge pulse detecting circuit a. By a signal generating circuit B for separating phase angle, phase angle dividing pulses are transmitted for every point equally divided to N pieces. An average cycle distribution for the apparent electric discharge 1 and generated phase angle phi are obtained by a detection circuit C. By a CPU of arithmetic display circuit D, (phi-n) distribution and (phi-q) distribution are read out after one measurement period is finished, then the maximum electric discharge qmax, increment amount DELTAtandelta of loss angle and increment amount DELTAI of AC current are calculated, and salso the distortion degree of (phi-q) distribution is calculated and printed out.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a device that can quickly diagnose insulation deterioration of rotating machine windings, CV insulated cables, etc. under live wire conditions using various diagnostic methods simultaneously or separately. It is.

(Conventional technology and its problems) In order to ensure stable power transmission without power outages in the power system, the rotating machines and cables that make up the system must be used.

It would be ideal to be able to diagnose the insulation condition of transformers and other equipment in an actual operating state, that is, in a live wire state, with high accuracy and in a non-destructive manner.

By the way, in the past, the maximum level of partial discharge pulses that occur when insulation deteriorates, that is, the apparent maximum discharge charge q. 0.
Increase in loss angle (tanδ) Δtanδ.

The well-known insulation deterioration diagnosis method is based on the change in the increase ΔI of the alternating current (capacitance current), and also the skewness of the φ-q distribution, which is the partial discharge phase characteristic, based on the inventors' method, or the insulation deterioration. Highly accurate insulation deterioration diagnosis can be achieved by combining various diagnostic parameters such as the insulation deterioration diagnosis method that utilizes changes (see JP-A No. 60-203866) and compensating for the advantages and disadvantages of each method of insulation deterioration diagnosis. It is carried out.

However, in such conventional methods, the various diagnostic parameters described above are determined separately using separate measuring instruments. Therefore, the measurement work is complicated and requires a lot of time, leading to an increase in work costs, and furthermore, the price of the entire measuring device becomes expensive.

In addition to this, a major drawback is that when measuring the above-mentioned diagnostic parameters such as the increase in loss angle Δtanδ and the increase in alternating current ΔI, it is well known that the operation of the rotating machine or other object to be diagnosed is stopped or during measurement. The drawback is that power transmission must be stopped.

(Objective of the Invention) The present invention solves the above-described partial discharge phase characteristics, that is, the deterioration of the skewness of the φ-q distribution, and the maximum discharge charges q1 and 8, which were conventionally determined using separate measuring instruments in the non-live state. The problems of the conventional method are solved by allowing diagnostic parameters such as the increase in loss angle Δtanδ and the increase in alternating current ΔI to be simultaneously and easily and quickly determined using a single measuring device in a live line state. The aim is to

(Means of the present invention for solving the problem) The present invention detects partial discharge pulses generated due to insulation deterioration, such as void defects, and an example of a partial discharge pulse measured in a second (multiple cycles) is shown in FIG. A partial discharge pulse signal data group such as (ql.

φ, )i=1...n (here, qz φ1 is the size of the i-th pulse, the phase angle of the i-th) pulse, and the number of measured pulses), and this partial discharge pulse data Count the number of pulses n of the group size q and calculate n(q) as a function of the pulse size q, i.e. the cycle average q
−n distribution and the average pulse height q per cycle for the applied voltage phase angle φ as a function of φ, q(φ), i.e. φ
This was done by clarifying that by determining the −q distribution, the maximum discharge charge q, , 8, the increase in loss angle Δtanδ, and the increase in charging current ΔI can be determined. That is, ■maximum discharge charge q3. ．． is a constant pulse generation frequency n
Since it is defined as the pulse detection level when (q) is reached, it can be determined by calculating q mat that satisfies the following equation (1) using the qn distribution.

n9=7 J'2 nc(1)dq---(1)■ The increase in the loss angle Δtanδ is obtained using the φ-q distribution. In other words, the current equation when there is no partial discharge is I(φ)=fi Icos(φ+δ), and the current equation when there is partial discharge is given as: 1'(φ)=I(φ)+q(d) .

Here, the increase in loss angle Δtanδ is the loss angle tanδ without partial discharge, and the loss angle with discharge is jan
If δ゛, then from the definition 1Mtvrl = tan5' - tanδtan6
= f:I(φ)singtfi/f,”I(φ)
cosφdφtanl' = f:I'(φ)siru
J>dφ/f:I'(φ)cosφdφ, and from the above, the increase Δtanδ is given as f:1'(φ)COφ=JπIcosδfoI(φ)
Since sindxip = , fi, yrlsin4r, by knowing the current I from, for example, the measured voltage and the rated capacity of the equipment to be diagnosed, it can be determined as follows (2). In addition, since the loss angle is considered to be in a not very large range, that is, tan δ(l, lq(φ) 1 (I), cos δ:=1.qtanJ=0, so it can be approximately determined by.

■Increase in charging current △[ is, assuming that the effective value of the alternating current without partial discharge is 1, the current in the case of partial discharge is 1. (φ) is Id(φ) = 721 cosφ + q(φ) (here, q(φ) is the partial discharge current per phase angle) as in the case of calculating the loss angle, and from this, the effective value 11 of 16 is given by Given.

Here, the increase in charging current ΔI [%] is, by definition, the effective value I of alternating current when there is partial discharge.

and the difference between the effective value of AC current in the absence of partial discharge.
It is the ratio of Therefore, if the current ■ is known from, for example, the measured voltage and the rated capacity of the insulation deterioration diagnostic equipment, Δ■ can be found as follows.

Therefore, from the above, as shown in the principle circuit diagram shown in Fig. 2, the grounding wire current in the live state of the insulation deterioration diagnostic equipment (1) is detected by the current detector (2) such as a current transformer, and q- n
Distribution [n (q)] measuring device and φ-q distribution (q(φ)1 In addition to measuring device (3), q-n of its calculated output
The distribution output is calculated by the maximum discharge charge qIn a
In addition to 4), the φ-q distribution output is calculated by the increase in the loss angle Δta given the alternating current when there is no partial discharge.
Calculator (5) of nδ and increase of alternating current Δ■[%
] In addition to the arithmetic unit (6), for example, the above equation (1), (3
) and (4), and by adding the measurement results of the φ-q distribution to the skewness calculator (7), each diagnostic pattern can be measured in the live line state using one measuring device. You can easily and quickly obtain the same information at the same time. Next, the present invention will be specifically explained with reference to Examples.

(Embodiment) FIG. 3 is a block circuit diagram of an embodiment of the present invention. In the figure, CT is a current transformer, and insulation deterioration diagnostic equipment M
Detects ground wire current. BF is a bandpass filter that detects partial discharge pulses from the detected ground line current. AM is an amplifier, which constitutes a partial discharge pulse detection circuit A to detect partial discharge pulses.

B is a phase angle discrimination signal generation circuit, and S is a synchronization signal input terminal, which uses an existing transformer, capacitor voltage divider, etc. to convert the voltage applied to the insulation deterioration diagnostic equipment M, that is, the system voltage. The reduced voltage e shown in FIG. 4(a) is applied as a synchronizing signal voltage. ZC is a zero cross signal generation circuit, which generates a synchronizing signal voltage e as shown in Fig. 4 fb).
It sends out a pulse that occurs at the zero point of . CD is a phase angle division pulse oscillation circuit, PC is a phase counter,
The oscillation circuit CD sends out a pulse signal with a higher frequency than the frequency of the synchronization signal voltage e, and the phase counter PC counts the phase angle division pulses from the oscillation circuit CD using the pulse signal from the cello cross signal generation circuit ZC as a synchronization signal. Then, every time a predetermined number of pulses are counted, a phase angle dividing pulse is sent out at each point where one cycle of 360° of the synchronizing signal voltage e is divided into N equal parts as shown in FIG. 4(C).

C is a detection circuit for n-q distribution and φ-q distribution, PH is a peak hold circuit, AS is an auto-threshold circuit, and peak hold circuit PH is the output of the partial discharge pulse detection circuit A. is input, and its peak level is held every time a partial discharge pulse exceeding a set threshold level of the auto-threshold circuit AS enters. A.D.
is an analog-to-digital conversion circuit, PS is a polarity discrimination circuit,
To is an aggregation circuit, and the aggregation circuit TO receives the phase angle division pulse from the phase counter PC, the output of the peak hold circuit PH, and the output of the polarity discrimination circuit PS, and calculates the following during the measurement period (multiple cycles): Partial discharge pulses occurring in N phase angle intervals of each cycle, for example, as shown in FIG.
Q10.11Q+3.1n qs in the cycle.

, 1, in the second cycle qIo, 2IQ117.
2I Q46. l, in the third cycle, Q63゜Q13.3r Q15.2+ q4g, 2, and in the Nth cycle, q3n+ qlon+ Q15ka, Q
24°? 440ゎ+ Q44.ゎ(The first digit of the foot character indicates the phase angle division number, and the second character indicates the cycle number) are totaled for each phase angle division, and the applied voltage phase angle characteristics of the frequency of occurrence of partial discharge pulses, That is, the cycle average distribution of φ-n is determined. At the same time, the peak level value of the partial discharge pulse obtained by the peak hold circuit PH is aggregated for each phase angle division as shown in Fig. 4 (g), and the apparent discharge charge q and the generated phase angle φ are calculated. Distribution (φ-q distribution)
Find the cycle average distribution of.

D is an arithmetic display circuit, of which BM is a buffer memory,
CPU is a microcomputer, PR is a printer, and the microcomputer CPU reads out the φ-n distribution and φ-q distribution from the aggregation circuit To stored in the buffer memory BM after one measurement period, and calculates the maximum value using the above-mentioned formulas. Discharge charge q. , 8. Calculate the loss angle increase Δtanδ and the alternating current increase ΔI, and also calculate the skewness of the φ-q distribution and print them out.

Next, an actual measurement example according to the present invention will be explained.

Table 1 shows the voltage: 6.6KV, capacity: 10.0OOkVA (
7) Maximum discharge charge qta*x measured by the conventional method and the present invention for generator windings, increase in loss angle Δt
This is a comparison of an δ and the charging current increase ΔI, and the diagnostic accuracy is almost the same as the conventional diagnostic method in a non-live state.

Table 1: Δtanδ, ΔI, etc. were measured at the same time, but
It goes without saying that only what is necessary can be measured by selectively operating the arithmetic circuit.

(Effects of the Invention) As described above, according to the present invention, by simply measuring the partial discharge pulse, not only the maximum discharge charge Q m & can be measured at the same time without any problems. Therefore, not only can the cost of the measuring device be reduced compared to the conventional method, but also
Since the measurement time is shortened and the work is made easier, the cost required for insulation diagnosis can be significantly reduced. In addition to this, it is possible to measure the maximum discharge charge etc. in a live line state.
Diagnostic accuracy can be improved. Furthermore, in the above, qmax 1

[Brief explanation of the drawing]

Fig. 1 is a diagram of the generation situation of partial discharge pulses, Fig. 2 is a diagram explaining the principle of the present invention, Fig. 3 is a circuit diagram of an embodiment of the present invention, Fig. 4
The figure is a waveform diagram for explaining the operation. (1)...Insulation deterioration diagnostic equipment, (2)...Current detector, (3)...N-Q distribution and φ-Q distribution detector, (4)...Maximum discharge charge arithmetic unit, (5)...
・Arithmetic unit of increase in loss angle Δtanδ [%1, (6)
...Arithmetic unit for the increase in alternating current ΔI, (7)...
φ-q distribution distortion calculator, M...Insulation deterioration diagnostic equipment, CT...Current transformer, BF...Band pass filter, AM...Amplifier, B...Phase angle division signal Generation circuit, Sv...Synchronization signal input terminal, PT...Transformer, ZC...Serocross signal generation circuit, CD...
・Clock pulse oscillation circuit, PC...phase counter, C...n-q and φ-q distribution detection circuit, P
H...Peak halt circuit, AS...Auto threshold circuit, AD...Analog/digital conversion circuit, PS...Polarity discrimination circuit, TO...Tally circuit, D...Calculation display circuit , BM...buffer memory, CPU...microcomputer, PR...printer. agent

Claims (1)

[Claims] A detection circuit for the ground line current of an insulation deterioration diagnostic equipment in a live line state, a distribution of the magnitude q of partial discharge pulses detected by this circuit and the number of occurrences n thereof, and a distribution of the magnitude q of the partial discharge pulses and its occurrence number n. a circuit for determining the distribution of the generated phase angle φ as a cycle average over multiple measurement cycles;
Using the qn distribution by this circuit, the maximum discharge charge q_m
Using a circuit that calculates _a_x, the φ-q distribution, and the current I of the insulation deterioration diagnostic equipment, calculate the increase in the loss angle Δtan.
A circuit that calculates δ, a circuit that calculates an increase in charging current ΔI using the φ-q distribution and I of the insulation deterioration diagnostic equipment, and a circuit that calculates the skewness of the φ-q distribution. Prepare,
Maximum discharge charge q_m_a_x, increase in loss angle Δtan
1. A live line insulation deterioration diagnostic device, characterized in that it is possible to simultaneously or individually measure δ, charge current increase ΔI, and skewness of φ-q distribution in a live line state.