JPH0464206A - On-load tap changer - Google Patents

Abstract

PURPOSE:To determine the time of exchange with high accuracy by obtaining currents flowing through each arc contact from an output from a detecting section, arithmetically operating the consumption of each arc contact by calculating formula held at the time of normal operation, and comparing the arithmetic value and allowable consumption. CONSTITUTION:The closing time of a contact B is delayed by the consumption of a contact B. The delay is shown by gamma in the figure at the angle of rotation of a movable section. Since a contact A is contact-parted by closing the contact B, the contact-parting time of the contact A is also delayed with the delay of the closing of the contact B when the closing of the contact B is retarded. Consequently, time allowance up to the closing of a contact C is reduced to the duration of an arc generated by the contact-parting of the contact A, thus increasing the possibility of short circuits among taps. Accordingly, a second arithmetic section 11 compares consumption at every contact as well as the difference of consumption among each contact with each allowance value, and outputs the number of changeover until each consumption reaches the allowance values as the time of exchange on the basis of the integrated value of the number of tap changeover up to that time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an on-load tap switching device, and particularly to a means for predicting when to replace an arc contact of a switching switch.

[Prior art and problems to be solved by the invention] In general, an on-load tap changer includes an on-load tap changer consisting of a switching switch and a tap selector, and an operating mechanism that drives the on-load tap changer using switching information. It consists of Then, switching information is given to the on-load tap switching device according to the load status of the power transmission and distribution system, and the taps provided on the windings of the transformer are adjusted to adjust the voltage of the switching system.

The power transmission and distribution system to which this on-load tap-changing transformer is connected is often a main line, and if the on-load tap changing device fails, there is a risk of widespread power outage. Therefore, it is important to maintain high reliability of the on-load tap changer, and for this reason, thorough maintenance is essential.

By the way, the most important maintenance of the on-load tap changer is related to the wear and tear of the arc contacts of the changeover switch. That is, the consumption of the arc contact has a great effect on its current switching function, and if it exceeds a certain limit, it will become impossible to switch current or short circuit between taps, resulting in a serious failure.

Therefore, during periodic inspections that are usually carried out every 5 to 10 years, the wear and tear of the arc contacts is visually inspected to determine whether they are good or bad, and the average load condition of the transformer up to the point of inspection is also taken into consideration. The remaining life of the contact was then estimated.

However, for example, if the load condition of the transformer increases significantly from the value assumed at the time of the inspection, the wear of the contacts will progress more rapidly than expected, and by the time of the next inspection, the transformer will have reached its limit. It is possible that it has reached.

When such a situation occurs, it takes time to procure replacement contact parts, and unplanned power outages are forced, resulting in grid power supply failures. Furthermore, if replacement parts are always kept on hand to prevent this, public costs will increase, which is economically undesirable.

This invention was made to solve the above-mentioned problems, and makes it possible to estimate the remaining life of the arc contact of a switching switch with high accuracy regardless of load fluctuations.

[Means to solve the problem]

The on-load tap switching device according to the present invention includes a detection section that detects the switching direction, winding voltage, and load current during operation of the operating mechanism, and an arc contact that detects whether the arc contact is operating normally based on the output of this detection section. A first calculating section calculates the amount of contact wear for each arc contact under the assumption that and a second calculation unit that calculates the replacement time of the arc contact based on the predetermined allowable wear amount.

[For production]

The current flowing through each arc contact is determined from the output of the detection unit, and it is determined whether the contact is interrupted or closed.Based on this information, the wear amount of each arc contact is calculated using a calculation formula that is valid when the arc contact is in normal operation. . This calculated value is compared with the allowable consumption amount, and based on the number of tap changes up to that point, the number of tap changes until the consumption amount reaches the above-mentioned allowable value is calculated, and the switching timing is estimated.

〔Example〕

FIG. 1 is a block diagram illustrating a load-on/off/down switching device according to an embodiment of the present invention. In the figure, (1) is the on-load tap changer connected to the transformer winding (2), (
3) is an operating mechanism that drives the switching switch of the on-load tap changer (1), (2) is a switching detection unit that detects the operating direction of the operating mechanism (3) and the tap position immediately before switching, ((5) is a voltage sensor that detects the voltage of the transformer winding (2), (6)
is a current sensor that detects the load current of a transformer, and these G
The output from the detector port consisting of 4) to 6) is recorded in the recording section. (9) calculates the amount of contact wear for each arc contact using the calculation formula described later from the data in the recording section 8,
The first calculation unit (G0), which integrates the calculated value for each tap change along with the number of tap changes, has a memory that presets and stores the allowable amount of wear for each arc contact and the allowable value for the difference in amount of wear between each arc contact. Section (11) is a second calculation section that calculates the replacement timing of each arc contact from the data of the first calculation section (9) and the storage section.

Next, in order to explain the specific calculation contents of each calculation unit (91(+1)), first, the operation of the arc contact of the switching switch and the phenomenon when the contact wears out will be explained with reference to Figures 2 to 4. do.

Figure 2 shows a switching switch (1) with arcing contacts A to C.
This is a circuit diagram including a) and a tap selector (lb), in which:
(12) is a current-limiting resistor with a resistance value R, and ■ is a transformer winding (
In the voltage of 2), ■ is the step voltage, and ■ is the load current. And here, the moving part of the arc contact is indicated by the arrow (13)
A series of operations from contact A to contact B to contact C is performed.

The limit of the amount of wear of the arc contact needs to be considered from both the absolute amount for each arc contact and the difference in the amount of wear between the arc contacts. The former is determined from the current switching function of each arc contact, and assuming that the arc contact continues to operate normally, the amount of wear is determined by the following formula.

L=u・■t・ta Here, engineering is the breaking current, U is the constant, and p is the exponent (1<p<2
)-ta is an average arc duration of about 0.3 cycles.

Further, the breaking current in the case of FIG. 2 is as follows.

Breaking current of contact A: I, -I +V, /R However, if the switching direction is opposite to that shown in the diagram, the current will be 11-V, /R.

Also, V,=K(n)-V. Here, K is the ratio between the step voltage V and the winding voltage ■, which can vary depending on the tap position n.

Breaking current I 1 of contact B = V - / R However, in the illustrated switching direction, it is closed, so it is 110.

Breaking current I of contact C, = I However, since it is closed in the switching direction shown, it becomes 11-0.

Next, the limit due to the difference in consumption amount will be explained. Figure 3 shows
- As an example, the degree of wear of contact B is contact A.

This shows the state when the size is considerably larger than that of point C, and the movable part of the contact is at the position where it is just inserted into contact B.
In the figure, the dotted line indicates the state when there is no wear and tear, such as when new.
As can be seen from this figure, due to wear and tear on contact B,
This will delay the introduction of the product. This delay is represented by θ in the figure, which is the rotation angle of the movable part.

FIG. 4 is a time chart showing a series of operations of each contact. Contact A opens when contact B closes, so the third
As shown in the figure, if the closing of contact B is delayed, the opening of contact A will also be delayed accordingly. As a result, the time margin until the contact C is closed is reduced relative to the duration of the arc generated by the opening of the contact A, increasing the risk of short circuit between the taps.

For this reason, the second calculation unit (11) in FIG. 1 compares the amount of wear for each contact as well as the difference in amount of wear between each contact with its respective tolerance value, and calculates the cumulative value of the number of tap changes up to that point. Basically, the number of times of switching until each wear amount reaches the allowable value is output as the replacement time.

As described above, even if you do not have to stop the transformer operation, take out the switching switch, and measure the amount of contact wear, you can always know the wear status with comparable accuracy, and it is also suitable for sudden changes in load conditions. It becomes possible to respond accurately and advance preparation of conversion parts can be done in a planned and economical manner.

Furthermore, a periodic inspection may be performed every 5 to 10 years to actually measure the wear amount of the arc contact and compare it with the above-mentioned integrated value.

In this case, if the actual measured value is large compared to the integrated value, this may indicate a problem that increases the average arc duration, such as an increase in friction in the drive system of the arc contact and a decrease in the contact opening speed. Since this can be considered to indicate the existence of such defects, it is possible to carry out focused inspections assuming these defects, and to improve maintenance.

In the above embodiment, the tap position n at each switching point is detected by the switching detection section (A), but the step voltage V, = K (n>・V, K(n) is independent of the tap position n). Especially if this tap position n is always constant,
detection is not necessary.

Furthermore, the present invention can be applied in exactly the same way to the calculation of the time to replace the filtering material of a live-line oil purification device of an on-load tap changer, and the same results will be obtained. That is, the live line oil purifier prevents contamination and deterioration of the insulating oil by constantly removing carbon generated by the decomposition of the insulating oil in the switching switch by the operation of the arc contact using a filter material. The amount of carbon captured by this filter material is proportional to the arc energy of each arc contact, and this arc energy is further proportional to the breaking current, arc voltage, and arc connection time, of which the arc voltage is generally 60 to 60% during normal breaking. Since it is constant at 100V, the captured amount can be calculated using the same formula as the above-mentioned formula for calculating the wear amount of the arc contact. Therefore,
The concept of the second calculation unit described in the claims of the present application includes a case where the allowable amount of consumption is set as an allowable value of the amount of carbon captured by the filter medium, and the time to replace the filter medium is calculated. .

〔Effect of the invention〕

Since the present invention is configured as described above, the remaining life of the switching switch arc contact and replacement time can always be known with high accuracy regardless of load fluctuations, and economical and thorough maintenance can be performed. Become.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an on-load tap switching device according to an embodiment of the present invention, Fig. 2 is a circuit diagram including each arc contact, and Fig. 3 is a similar diagram when there is a difference in the amount of wear of each arc contact. FIG. 4 is a time chart showing a series of operations of each arc contact. In the figure, (1) is a load tap changer, <1a) is a switching switch, (2) is a winding, (3) is an operating mechanism, m is a detection unit, (9) is a first calculation unit, (1 is the second calculation unit,
■ is the voltage of the winding, and ■ is the load current. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Patent Attorney Masuo Oiwa Figure 1

Claims (1)

[Claims] A load tap changer equipped with a switching switch having a plurality of arcing contacts and an operating mechanism for driving the load tap changer, the tap changer of a winding being switched when load current is applied. A detection unit that detects the switching direction of the operating mechanism, the voltage of the winding, and the load current, and the output of this detection unit, assuming that the arc contact is operating normally. A first calculation unit that calculates the amount of contact wear for each arc contact and integrates the calculated value for each tap change together with the number of tap changes, and the output of this first calculation unit and a predetermined allowable consumption. and a second calculation section that calculates the replacement timing of the arc contact based on the amount of the arc contact.