JPH09166651A - Oscilloscope apparatus for electric power - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an oscilloscope apparatus by which the life of a contact maker at a breaker can be managed by extracting, when the breaker is operated on the basis of current waveform data at the generation of an accident, the magnitude of an arc current flowing to the contact maker and estimating the wear amount of a main contact maker. SOLUTION: A CPU 1 reads out, from an A/D converter 11, digital data on signals sampled by sample-and-hold circuits 9a to 9h, inputs an operating contact 52TX at a protective relay from a contact signal input port 14, and stores, in a RAM 3, waveform data on voltages and currents for a definite period before and after a breaker is operated. After that, an arc current value at every phase is extracted as the magnitude of an arc current on the basis of a stored current waveform, the wear amount of a contact maker is computed on the basis of the value of the arc current so as to be accumulated, and it is judged whether the value exceeds 70% of a predetermined life amount or not. When the value exceeds 70% of the life amount, an alarm contact signal is output via a contact-signal output part 13.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a power oscilloscope device for recording voltage and current waveform data of a power system.

[0002]

2. Description of the Related Art Conventionally, a so-called power oscilloscope for accumulating and storing waveform data of voltage and current at a predetermined portion of a power system has been used to analyze the power system when an accident occurs in the power system. Such a power oscilloscope device,
The input voltage and current signals are sampled at a constant cycle, A / D converted, and the data string is accumulated and stored as voltage and current waveform data. For example, when a short-circuit accident is detected, some start signal is generated. Once entered,
Waveform data for a certain period before and after that is saved,
The accident analysis can be done later.

FIG. 1 is a diagram showing an example of a power system. As shown in the figure, a circuit breaker CB is provided in the line,
A current transformer CT that detects a current flowing through the line and an instrument transformer PT that detects a transmission voltage are further provided. The power oscilloscope device receives the CT and PT signals and sequentially stores the waveform data in the ring buffer format. With this configuration, if it is detected that a short-circuit accident has occurred on the line, a start signal is input to the power oscilloscope device, and the power oscilloscope device displays voltage and current waveforms over a certain period before and after that. Save the data. On the other hand, when the above-mentioned short-circuit accident or the like is detected, a trip command is given to the circuit breaker CB, and the line in which the short-circuit accident has occurred is cut off.

[0004]

By the way, the main contactor of the circuit breaker is arc-discharged when it is tripped, and the main contactor is worn out whenever the circuit breaker interrupts the current. Since the characteristics and reliability of the circuit breaker are deteriorated as the main contact wears, the life of the main contact must be managed in order to maintain them at a certain level. In general, the circuit breaker specifies the maximum number of times that the fault current can be interrupted, and the operation has been performed such that the replacement time of the main contactor is determined depending on how many times the circuit breaker is interrupted.

However, the value of the current to be interrupted differs greatly depending on the content of the accident. For example, if a short circuit accident occurs at point (a) immediately after the circuit breaker shown in Fig. 1, the maximum fault current determined by the impedance from the power plant to the circuit breaker CB flows, but at point (b) the same short circuit accident occurs. Even if a fault occurs, only a small fault current will flow compared to when a short circuit occurs at point (a) depending on the line impedance. Generally, the rated breaking current value of the circuit breaker is selected according to the maximum fault current that can occur, but since the breaking current differs depending on the fault point and the type of fault as described above, the actual breaking current value is specified. It is always smaller than the rated breaking current value.

On the other hand, the wear of the main contactor of the circuit breaker greatly changes depending on the breaking current, and therefore, the number of times the breaking is possible changes greatly according to the breaking current. Here, FIG. 2 shows the relationship of the number of times of interruption until the main contact is worn out to the extent that it is necessary to replace the main contactor at each interruption current. In the example shown in the figure, for example, a fault current of 25 [kA] (rated breaking current)
It is specified that the current can be interrupted up to 10 times when it is interrupted, but for example, when interrupting the current of the rated current value of 1.2 [kA], it can theoretically be interrupted up to 2000 times.

From the above-mentioned relationship, if the life is uniformly controlled depending on whether or not the actual number of interruptions reaches the prescribed number of interruptions, in reality, the wear amount of the main contact is still small. Despite this, the main contact will be replaced. Therefore, it is uneconomical in terms of equipment cost and work cost. In particular, circuit breakers of recent years have adopted GCB, VCB, etc., and it is necessary to sufficiently manage the surrounding dust and humidity when replacing the main contactor, which requires a great deal of labor, time and cost. If this is omitted and the main contactor is replaced while the surrounding environmental management and procedure management are insufficient, the reliability of the circuit breaker will be compromised.

In order to solve such a problem, the wear amount of the main contactor due to arc discharge may be measured every time the circuit breaker is operated to determine the replacement time of the main contactor. If an attempt is made to install a new device for that purpose, there will be problems in terms of installation space and required cost.

An object of the present invention is to manage the life of the main contactor of the circuit breaker by utilizing the fact that the data of the current waveform during operation of the circuit breaker is inevitably stored in the oscilloscope for electric power. The present invention is to provide a power oscilloscope device.

[0010]

SUMMARY OF THE INVENTION According to the present invention, voltage and current signals of a power system are input, sampled at a constant cycle, AD-converted, voltage and current waveform data is accumulated and stored, and a circuit breaker A power oscilloscope device for recording voltage and current waveform data before and after operation, wherein the life of the main contactor of the circuit breaker can be accurately managed without providing new measuring means. As described, the magnitude of the arc current flowing through the main contactor of the circuit breaker during operation of the circuit breaker is extracted from the waveform data of the current,
A means for estimating the amount of wear of the main contactor of the circuit breaker from the magnitude of the arc current, and the amount of wear is accumulated every time the circuit breaker operates, and the life of the main contactor is judged by comparing with the amount of life. And means for performing.

Further, in the power oscilloscope device of the present invention, in order to more accurately estimate the amount of wear of the main contactor of the circuit breaker and manage the life thereof, as described in claim 2, the arc When the current is extracted, the magnitude of the arc current of each phase is extracted based on the current waveform data in the approximately half cycle before the arc is extinguished to estimate the wear amount of the main contact.

Further, in order to enable the arc current value for each phase to be accurately extracted, the power oscilloscope device of the present invention, as described in claim 3, when extracting the arc current of each phase, The magnitude of the arc current of each phase is extracted based on the current waveform data of each phase in the period of approximately half cycle immediately before the extinction of the phase that is extinguished with the latest delay.

In the power oscilloscope device according to the first aspect of the present invention, the current signal of the power system is sampled at a constant cycle, and the current waveform data obtained by A / D conversion is used when the breaker operates. The magnitude of the arc current flowing through the main contactor (hereinafter simply referred to as the contactor) is extracted, the wear amount of the contactor is estimated from the magnitude of this arc current, and the wear amount is accumulated each time the breaker operates. Then, the life of the contact is determined by comparing it with the amount of life of the contact that is known in advance. In this way, the power oscilloscope is designed to extract the magnitude of the arc current flowing through the contactor of the circuit breaker from the waveform data of the current stored when an accident occurs.
It becomes possible to manage the life of the contacts of the circuit breaker without adding new measuring means or measuring device.

In the power oscilloscope device according to the second aspect of the present invention, the arc current value is extracted by the current value in the substantially half cycle before the arc is extinguished. Here, the relationship between the trip start timing of the contact and the arc current will be described with reference to FIG. Since the arc extinguishes at the zero point of the current waveform, the duration of the arc current differs depending on the trip start time, but in any case, the arc current flows in the period from when the arc extinguishes until it goes back approximately half a cycle. Since it is clear that the current value (for example, its peak value or effective value) in the approximately half cycle before this arc is extinguished, the amount of contact wear can be estimated. The magnitude of the effective arc current is surely required.

In the power oscilloscope device according to the third aspect of the present invention, the magnitude of the arc current flowing through the contacts of each phase during the operation of the circuit breaker during a two-phase or three-phase short circuit accident is extracted from the current waveform data. The amount of wear of the contactor of each phase of the circuit breaker is estimated from the magnitude of the arc current. In the case of three-phase alternating current, since the currents of the respective phases have a phase difference of 120 °, the energization time of the arc current generated in the contacts of the respective phases after the contacts of the circuit breaker are separated all at once differs. Here, the relationship between the trip start timing of the contact and the arc current at the time of a three-phase short circuit will be described with reference to FIG. In FIG. 4, IA, IB, and IC are current waveforms of A phase, B phase, and C phase, respectively. As shown in the figure, since the arc current is extinguished at the current zero point, if the contacts of each phase are tripped at the same time, from the timing t1 traced back by about half a cycle of the phase extinguished most recently. It can be seen that tripping (separation of contacts) has started within the range up to the timing t2 when the current of the earliest extinguished phase becomes 0.
Thereby, for example, the arc discharge time of each phase current at the time of a three-phase short circuit accident is estimated. That is, the A-phase arc discharge time is (t4-t2)-(t4-t1), the B-phase arc discharge time is (t3-t2)-(t3-t1), and the C-phase arc discharge time is 0-. (T2-t1). In this way, the magnitude of the arc of each phase is extracted from the current waveform data of each phase, and the amount of wear of the contactor of each phase of the circuit breaker is estimated from the magnitude of the arc current. According to the oscilloscope for electric power, the life of the contactor can be managed more accurately for each phase.

[0016]

1 is a block diagram showing the configuration of a power oscilloscope device according to a first embodiment of the present invention. In the figure, the CPU 1 executes a program written in advance in the ROM 2 to manage the life of the contacts of the circuit breaker as well as the original processing of the power oscilloscope device described later. RAM
3 is used as a temporary storage of voltage and current waveform data and another working area when the above program is executed. 6a to 6d are auxiliary instrument transformers, and 7a to
7d is an auxiliary current transformer, 6a, 6b, 6c are A phase,
The voltage signals of the B-phase and the C-phase are input, and the zero-phase voltage signal is input to 6d. In addition, auxiliary current transformers 7a, 7
Current signals of the A-phase, B-phase, and C-phase are input to b and 7c, and a zero-phase current signal is input to the auxiliary current transformer 7d.
Reference numerals 8a to 8h are analog filters for cutting unnecessary frequency bands, and 9a to 9h are sample and hold circuits that sample and hold the filtered signals at predetermined timings. The signal sampled by these sample and hold circuits is selected by the multiplexer 10, and the A / D converter 11 converts the signal into digital data. The CPU 1 gives timing signals to the sample and hold circuits 9a to 9h, the multiplexer 10 and the A / D converter 11 via the I / O port 12, and reads digital data from the A / D converter 11. Further, the CPU 1 inputs from the contact signal input port 14 an operation contact (52TX) of a protective relay (a relay that detects an accident and outputs a trip command of the circuit breaker) or an auxiliary contact (52a or 52b) of the circuit breaker, The waveform data of the voltage and the current for a certain period before and after the operation is stored in a predetermined area of the RAM 3. Further, the waveform data is printed out as a waveform on the printer 4. Also, C
The PU 1 transmits the waveform data and the like to the master station of the power oscilloscope device via the transmission interface 5. The CPU 1 further estimates the amount of wear of the contactor of the circuit breaker from the waveform data of the current, accumulates the amount of wear, determines the life by comparing it with a predetermined amount of life, and contacts when the predetermined condition is reached. An alarm contact signal is output via the signal output port 13.

Next, an example of waveform data at the time of a three-phase short circuit accident, which is stored when the above accident occurs and is transmitted to the master station, is shown in FIG.
Shown in In FIG. 6, VA, VB, and VC are A, respectively.
Phase, B phase, C phase voltage waveform, Vo is zero phase voltage waveform, I
A, IB and IC are current waveforms of A phase, B phase and C phase, respectively, and Io is a zero phase current waveform. Further, 52TX is a trip command contact signal of the circuit breaker output from the protective relay. In this example, a three-phase short circuit accident occurs at time t,
Then, a circuit breaker trip command is given after a delay of T. After a few cycles, the contacts are separated, the arc discharge is extinguished, and each phase is interrupted.

Next, a processing procedure of the CPU of the power oscilloscope apparatus according to the first embodiment is shown as a flowchart in FIGS. 7 and 8.

FIG. 7 shows an interrupt process performed at each sampling timing. First, 8 channels of input signals respectively received through the auxiliary instrument transformer and the auxiliary current transformer shown in FIG. 5 are sampled, and each channel is sampled. Of A
The / D conversion value is read, and this is accumulated and stored as data of one point of each voltage / current waveform data. This accumulation and storage is performed in the so-called ring buffer format, so that the latest voltage / current waveform data for a predetermined number of cycles is always left cyclically while rewriting the voltage / current waveform data for a predetermined number of cycles in order from the oldest one. To do. If the current timing is the timing for transmitting the accumulated waveform data to the master station, the waveform data for a predetermined cycle of each voltage / current is transmitted to the master station.

FIG. 8 shows the processing executed when there is a breaker trip command, and the breaker trip command is given from the relay operating contact (52TX) or the breaker auxiliary contact (52a, 52b). If so, the timing information is transmitted to the master station, and the voltage and current waveform data for a certain period before and after the circuit breaker trip command is issued is stored. Then, the arc current value of each phase is extracted as the arc current magnitude from the stored current waveform. As shown in FIG. 3, this is the peak value (maximum current value during the period in which it is estimated that arc discharge is occurring) that is traced back approximately half a cycle after the arc is extinguished or the arc is extinguished. Calculate the effective value for the half cycle period. As another method, considering the current waveforms of the other phases, as shown in FIG. 4, the periods t1 to t corresponding to approximately a half cycle immediately before the extinguishing of the phase most recently extinguished.
Crest value of current of each phase in 4 (maximum current value in the period in which arc discharge is estimated to occur) Ia, Ib,
Ic or the effective value of the period shown by hatching in FIG. 4 is obtained. Since the magnitude of the arc current is different depending on the phase (the sound phase is the load current level and is small),
By using the maximum phase current value as the representative value, it is possible to eliminate the need for management for each phase. Then, the wear amount of the contact is calculated from the value of the arc current by a calculation formula described later. As shown in FIG. 8, the amount of wear is then accumulated and it is determined whether or not the value exceeds 70% of a predetermined amount of life. If the cumulative amount of wear exceeds 70% of the service life due to the operation of the circuit breaker this time, a warning is output.

The amount of wear and the amount of life are compared as follows. If the rated breaking current of the circuit breaker is Ir and the number of rated breaking times is 10, the life K of the contactor is K = Ir ^N * 1
It becomes 0. Here, N is set to 1.745, for example. Therefore, when the rated breaking current is 25 kA, K = 2750.

Further, the contact wear amount L is L = Σ (If) ^N, where If is an actual breaking current value (that is, arc current value). If L> K * 0.7, a warning is output. With this warning given, the rated breaking current is 25 [k
It is possible to cut off A] up to three times thereafter.

[0023] Incidentally, the remaining blocking number C during interruption of interrupting current If, so is represented by C = (K-L) / If N, in a state where the alarm output is performed, since for example each time 9 [kA] When shutting off, C = 2750 x (1
-0.7) / 9 ^1.745 = 17.8, which means that it is possible to shut off 17 more times.

Next, the configuration of a power oscilloscope device according to a second embodiment of the present invention will be described with reference to FIGS. 9 and 10.

The block diagram shown in FIG. 9 differs from FIG. 5 shown as the first embodiment in that an undervoltage relay (UV) and an overvoltage relay (O) are provided from the contact signal input port 14.
V), an operation contact signal of an accident detection relay such as an overcurrent relay (OC) is further input, and the waveform data is stored in the RAM 3 using this signal as a starting condition. Other configurations are the same as those of the first embodiment.

FIG. 10 shows a process performed based on the operation contact signal of the accident detection relay, and the undervoltage relay (U
V), overvoltage relay (OV), overcurrent relay (OC), etc. If an accident is detected based on the operating contact signal of an accident detection relay, voltage and current waveform data for a certain period before and after that is stored. In addition, based on the contact signal of the relay operation contact (52TX) or the circuit breaker auxiliary contact (52a, 52b),
If it is determined that the breaker has been broken, the arc current value of each phase is extracted from the stored current waveform. The subsequent calculation of the wear amount of the contact and the subsequent processing are the same as those in the first embodiment.

In the above example, the life of the contacts of the circuit breaker is managed on the power oscilloscope body side.
On the master station side of the power oscilloscope device, it is possible to manage the life of the contactor by the same process based on the current waveform data when the accident occurs.

[0028]

According to the first aspect of the present invention, the operation of the circuit breaker is determined from the current waveform data at the time of an accident, which is obtained by sampling the current signal of the power system at a constant cycle and performing A / D conversion. Since the magnitude of the arc current flowing through the contact is sometimes extracted to estimate the amount of wear of the main contact, the life of the contact of the circuit breaker can be managed without adding new measuring means or measuring equipment. You will be able to do it.

According to the second aspect of the invention, since the magnitude of the arc current is extracted by the current value in the approximately half cycle before the arc is extinguished, the magnitude of the arc current is surely obtained. The wear amount of the contactor of the circuit breaker can be estimated more accurately, and the replacement timing can be determined more accurately.

According to the third aspect of the present invention, the magnitude of the arc current flowing through the contact of each phase during operation of the circuit breaker is extracted from the current waveform data, and the magnitude of the arc current of each phase of the circuit breaker is extracted. Since the amount of contact wear is estimated and the life of the contact is determined for each phase, the life of the contact can be managed more accurately for each phase.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of a power system in which a circuit breaker is arranged.

FIG. 2 is a diagram showing an example of the relationship between the breaking current of a circuit breaker and the number of possible breaking times.

FIG. 3 is a diagram showing a relationship between a trip start timing of a contact and an arc discharge time.

FIG. 4 is a diagram showing the relationship between the contact start timing of the contact and the arc discharge time.

FIG. 5 is a block diagram showing a configuration of a power oscilloscope device according to the first embodiment of the present invention.

FIG. 6 is a diagram showing an example of voltage / current waveforms stored in the oscilloscope for electric power when an accident occurs.

FIG. 7 is a flowchart showing a processing procedure of the power oscilloscope device according to the first embodiment.

FIG. 8 is a flowchart showing a processing procedure of the power oscilloscope device according to the first embodiment.

FIG. 9 is a block diagram showing a configuration of a power oscilloscope device according to a second embodiment of the present invention.

FIG. 10 is a flowchart showing a processing procedure of the power oscilloscope device according to the second embodiment.

Claims (3)

[Claims] 1. A voltage and current signal of a power system is input, sampled at a constant cycle, AD-converted, voltage and current waveform data is accumulated and stored, and voltage and current waveforms before and after the operation of a circuit breaker are stored. In a power oscilloscope for recording data, the magnitude of the arc current flowing through the main contactor of the circuit breaker during operation of the circuit breaker is extracted from the waveform data of the current, and the main contact of the circuit breaker is calculated from the magnitude of the arc current. An oscilloscope device for electric power provided with means for estimating the wear amount of the child, and means for accumulating the wear amount each time the circuit breaker operates and for judging the life of the main contactor by comparing with the life amount. . 2. The means for estimating the amount of wear, when extracting the arc current, extracts the magnitude of the arc current of each phase based on the current waveform data in a substantially half cycle before the arc is extinguished. The oscilloscope apparatus for electric power according to claim 1, which is a thing. 3. The means for estimating the amount of wear, when extracting the arc current of each phase, the current waveform of each phase in the period of approximately half cycle immediately before the extinction of the arc extinguished most recently. The oscilloscope for electric power according to claim 1, wherein the magnitude of the arc current of each phase is extracted based on the data.