JPH0580107A - Failed division sensing system of transforming station - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a fault section detection system for a substation that prevents malfunction due to a difference in clip characteristics of optical CT. [Structure] In order to cancel the difference in the clip characteristics of the optical CTs 8 and 9 attached to the doll section of the substation, the range of the digital converter of the digital current differential discriminator connected to the optical CTs 8 and 9 is changed to the optical CT range. Keep it narrower than the saturation region. As a result, the output in the large current region is cut, and malfunction due to a difference in clip characteristics or the like can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is capable of automatically detecting a failure section when a ground fault or a short-circuit accident occurs inside a transmission substation or a distribution substation. It concerns the improvement of the system.

[0002]

2. Description of the Related Art In a substation as described above, a plurality of banks (transformer banks) and load lines are connected to a bus bar, and these banks and load lines are each connected to a CT.
Since the CT is installed, an accident that occurred outside the substation can be easily detected by these CTs, and the part can be automatically disconnected to continue power transmission to other parts. However, regarding the accident that occurred on the busbar inside the substation, the accident point is the doll part on the bank side (the connection part between the bank and the busbar), the track side doll part (the connection part between the load line and the busbar), etc. It is not easy to determine whether it is inside or outside the doll part, and until the worker goes out and finds the accident point, power off all the lines stopped by the existing protection relay system. I had to do it.

Conventionally, as a protective relay device for protecting the busbars of a substation, a method of making a current differential discrimination using a CT attached to a bank or a load line has been widely applied.
This current differential method is to judge whether an accident is inside the section or an outside accident by the following equation based on Kirchhoff's principle using the measured current value of CT installed for each of a plurality of sections to be protected. | ΣI |> K1 × Σ | I | + K2 | ΣI |: vector sum of current measurement values of each CT Σ | I |: sum of absolute value of current measurement values of each CT K1, K2: constant In this method, 3 units When using the above CT, it is necessary to measure up to the maximum short-circuit current region of the substation. Moreover, since the CT attached to the bank or the load line is used, it was not possible to judge whether the accident point was the bank side doll part or the track side doll part.

As a failure section detection system for a substation that can determine whether the accident point is inside or outside the doll section, Japanese Patent Laid-Open No. 2-2233
As described in Japanese Patent Publication No. 34, a doll part is equipped with a relay capable of detecting the direction of the optical CT and the current, and when the accident occurs, the fault current detected by the optical CT and the relay and its direction are input to a calculator. There is a method to detect the section where the accident occurred. In order to make a distinction by this method, it is necessary to know the open / closed state of the disconnector of each doll in advance, and in order to make an automatic judgment, it is necessary to input the signal of the open / close condition of the disconnector to the computing unit. There was a problem that there is.
Therefore, if this method is combined with the current differential method, it is possible to determine whether the accident point is inside or outside the doll part without knowing the switching condition of the disconnector. Further, in this case, since the number of CTs connected to the current differential discriminator is two, it is not necessary to measure up to the maximum short-circuit current region of the substation as the measurement current range of the optical CT, and the set value of the short-circuit current is not less than It just needs to be able to measure. However, since the optical CT has a clipping characteristic in which the output is saturated when the input becomes a large current, there is the following problem when trying to determine the fault point by the digital current differential discriminator.

That is, when an optical CT is used in combination with a magnetic CT (of a bank or load line), the optical CT is used.
If there is a characteristic difference between the magnetic CT and the magnetic CT in a large current region, when the sum of the output of the optical CT and the output of the magnetic CT is calculated, a sum current based on the characteristic difference as shown in the lower part of FIG. 5 is generated. However, it may cause malfunction. Therefore, in order to prevent this, an expensive optical CT that can measure up to a large current region
However, there is a problem that the cost becomes high. On the contrary, it may be possible to match the characteristics of the magnetic CT with the characteristics of the optical CT by using a converter, but there is a problem that variations in the characteristics of the analog circuit cannot be completely eliminated.

On the other hand, when the CT of the bank or the load line is also an optical CT, a difference in the clipping characteristics of the respective optical CTs still causes a malfunction, so it is necessary to make the clipping characteristics of the respective optical CTs uniform. After all, there was a problem that the cost was high.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and eliminates the need for optical C without the use of expensive optical CT.
The present invention has been completed in order to provide a failure section detection system for a substation that does not cause a malfunction due to the difference in the clip characteristics of T.

[0008]

SUMMARY OF THE INVENTION The present invention, which has been made to solve the above problems, provides an iron core and an optical magnetic field sensor for detecting a fault current at a position surrounding each section of a busbar conductor of a substation. A plurality of optical CTs configured with or a magnetic CT such as a bushing CT or a wire-wound CT (optical CT, etc.) is attached, and the optical CT is detected by a digital current differential discriminator. In the fault section detection system of the substation, which determines whether the fault point is inside or outside the section surrounded by optical CT etc. by digitally converting the current value measured by etc. and taking the vector sum or scalar sum for each section , The input voltage range of the digital converter of the current differential discriminator is the optical C
This is characterized in that the output voltage of T is made narrower than the saturated region.

[0009]

The present invention will be described in more detail with reference to the embodiments shown in the drawings. FIG. 1 shows the overall structure of a double bus system power transmission substation, where 1a and 1b are bus bars and 2a to 2a.
Reference numeral d denotes banks 1 to 4, and 3 denotes a large number of load lines. These banks 2 and load lines 3 are respectively provided with disconnectors 4, 5
And magnetic CTs 6 and 7 are attached. Each bank 2a
2d are connected so that power can be supplied to each busbar 1a, 1b from a portion called a doll portion in the central portion of the busbars 1a, 1b, and each load line 3 is also connected to the doll portion to connect to any busbar 1a, 1b. It has a structure that can also receive power from. However, busbar disconnectors 8 and 9 are attached to these dolls, and by opening either one and closing the other, they are selectively connected to either busbar 1a or 1b.

FIG. 2 shows a part of the optical system in which the optical CTs 10 and 11 are attached to the doll part in series with the busbar disconnectors 8 and 9. In FIG. 2, the busbar disconnecting switch 8 is closed, the busbar disconnecting switch 9 is open, and a state in which an accident occurs at the point indicated by the arrow on the busbar 1a is shown. When such an accident occurs, as shown by an arrow, an upward accident current flows in the magnetic CT6 of the bank 2a and an upward accident current flows in the optical CT10 of the doll part on the bank side. Input to the current differential classifier to determine whether the accident point is inside or outside the doll part. In the present invention, the optical CTs 10 and 11 are integrated with an insulator having a built-in optical fiber, and when this is installed in a doll part, it can be incorporated as a support insulator for a bus line disconnector. Also, the magnetic C
Although the existing magnetic CT is used for T6 and T7, an optical CT may be installed and used instead of the magnetic CT6 and 7.

In this determination method, when the accident point is outside the doll part as shown in FIG. 2, a fault current flows in the magnetic CT 6 and the optical CT 10 that have the same magnitude and opposite directions. Therefore, if the accident point is inside the doll section, the fact that the sum does not become zero is used. In order to make this determination accurately, it is necessary to prevent the sum current as shown in FIG. 5 from occurring due to the clipping characteristic of the optical CT.

Therefore, in the present invention, these optical CTs are used.
Also, the range of the digital converter of the current differential discriminator for converting the output of the magnetic CT into a digital signal is set to be narrower than the saturation region of the optical CT as shown in FIG. Specifically, it is preferable to make the output voltage of the optical CT as wide as possible in a range lower than the clipping voltage. Further, the range of the digital converter needs to be equal to or more than the set value of the short circuit current.
The current differential discriminator of the present invention which will be specifically described below discriminates by the following two AND conditions as shown in FIG. ｜ ΣI ｜ ≧ K1 ・ ・ ・ ・ ・ ・ ・ ・ ｜ ΣI ｜ ≧ K2 × Σ│I ｜ + K3 ・ ・ ・ Considering the case where current flows from one location at the time of an internal accident. In order to detect an accident, it is necessary to detect a current equal to or higher than K1 (short-circuit set value) in the equation. Therefore optical CT
The measured current range and the range of the digital converter must be more than the short circuit settling value. As a result, both the output waveform of the magnetic CT shown in the upper part of FIG. 3 and the output waveform of the optical CT having a saturation region as shown in the middle part are cut in the large current region by the digital converter of the current differential discriminator. It becomes a waveform. Therefore, when the sum of both waveforms is taken, it becomes almost zero as shown in the lower part of FIG. 3, and the mountain-shaped sum current as in the conventional case shown in FIG. 5 does not occur.

In the embodiment, the example in which the optical CT and the magnetic CT are combined is shown, but the CT of the bank and the load line is also the optical CT.
In the case of, it can be implemented in the same manner. In either case, it is not necessary to use an expensive optical CT that can measure up to a large current region or to accurately align the characteristics of each optical CT, which makes it possible to reduce the system cost and to prevent malfunctions. The accident point can be discriminated without any occurrence.

[0014]

As described above, according to the present invention, the range of the digital converter of the current differential discriminator is made narrower than the saturation region of the optical CT, so that the optical CT can be used without using the expensive optical CT. It prevents the malfunction due to the difference in the clip characteristics, and contributes greatly to the industrial development as a fault section detection system for a substation that solves the conventional problems.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an overall configuration of a fault section detection system in a substation.

FIG. 2 is an enlarged circuit diagram showing a part of a failure section detection system of a substation.

FIG. 3 is a waveform diagram of an example of the present invention.

FIG. 4 is a graph showing operating characteristics of a current differential discriminator.

FIG. 5 is a waveform diagram of a conventional example.

[Explanation of symbols]

 6 Magnetic CT 7 Magnetic CT 8 Optical CT 9 Optical CT

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoru Kato 1-1, Nakamaru-cho, Kita-ku, Aichi Prefecture (72) Inventor Yasuhisa Sakurai 59-6-1, Kashiwai-cho, Kasugai-shi, Aichi No. 302 Hosoi Heights

Claims (1)

[Claims] 1. A plurality of optical CTs each composed of an iron core and an optical magnetic field sensor for detecting a fault current at a position surrounding each section of a busbar conductor of a substation, or a part thereof being a bushing CT, A magnetic CT such as a wire-wound CT (hereinafter referred to as an optical CT) is attached, a current value measured by the optical CT is digitally converted by a digital current differential discriminator, and a vector is calculated for each section. In the fault section detection system of the substation that determines whether the accident point is inside or outside the section surrounded by optical CT etc. by taking the sum or the scalar sum, the input voltage range of the digital converter of the current differential discriminator is set. A fault section detection system for a substation, characterized in that the output voltage of the optical CT is narrower than the saturated region.