JP2561984B2 - Substation fault section detection system - Google Patents

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 that 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 judge 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 performing 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 the accident is inside or outside the section by the following equation based on Kirchhoff's principle using the measured current value of CT installed for each section 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 determine whether the accident point was the bank side doll part or the track side doll part.

On the other hand, as a failure section detection system for a substation, which can determine whether the accident point is inside or outside the doll section,
As described in JP-A-2-223334, the light C is added to the doll part.
There is a method of attaching a relay capable of detecting the direction of T and the current and inputting the fault current and its direction detected by the optical CT and the relay at the time of occurrence of an accident to a calculator 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 part in advance, and in order to make an automatic distinction, it is necessary to input the signal of the open / close condition of the disconnector to the calculator. 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. It just needs to be able to measure. However, since the optical CT has a clipping characteristic that the output is saturated when the input becomes a large current,
The following problems have been encountered when trying to determine the fault point with a 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 the 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 CTs of the banks and the load lines are also optical CTs, 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 or optical Cs composed of
Combination of T and magnetic CT such as bushing CT and wire wound CT
Seen together (hereinafter, referred to as optical CT, etc.) keep mounting, and this
The current value measured by optical CT etc. is converted into a digital value and the vector sum or scalar sum is taken for each section so that the accident point is the light C
In the fault section detection system of the substation that judges whether the section surrounded by T or the like is inside or outside, the above digital conversion,
Electricity that calculates vector sums and scalar sums and determines accident points
Input Voltage Recognition Range of Digital Converter of Current Differential Discriminator
Is narrower than the region where the output voltage of the optical CT is saturated.

[0009]

The present invention will be described below in more detail with reference to the illustrated embodiments. FIG. 1 shows the entire structure of a double bus type power transmission substation. 1a and 1b are busbars 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 either one is opened and the other is closed to selectively connect to one of the busbars 1a and 1b.

FIG. 2 shows a part of the figure, showing a state in which optical CTs 10 and 11 are attached to the doll part in series with 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 a point indicated by an arrow on the busbar 1a is shown. When such an accident occurs, as shown by the 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 bank side doll portion. Therefore, the output of these optical CTs is not shown in the digital type. Input to the current differential discriminator and digital
By converting and performing vector sum and scalar sum operations
Therefore, determine whether the accident point is inside or outside the doll section. 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. Further, although the existing magnetic CTs are used as the magnetic CTs 6 and 7, an optical CT may be installed and used instead of the magnetic CTs 6 and 7.

In this determination method, when the accident point is outside the doll part as shown in FIG. 2, since the accident currents of the same magnitude and opposite directions flow to the magnetic CT6 and the optical CT10, the sum thereof becomes zero. If the accident point is inside the doll section, the sum will not be zero. 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 input voltage recognition range of the digital converter of the current differential discriminator for converting the output of the magnetic CT into a digital signal is made narrower than the saturation region of the optical CT as shown in FIG. Specifically, it is preferable that the input voltage recognition range be as wide as possible in a range lower than the voltage at which the output voltage of the optical CT clips. Also, the input voltage of the digital converter
The recognition range must be greater than or equal to the short circuit current set value .
As shown in FIG. 4, the current differential discriminator of the present invention discriminates under the following two AND conditions. ｜ ΣI ｜ ≧ K1 ・ ・ ・ ・ ・ ・ ・ ・ ・ ｜ ΣI ｜ ≧ K2 × Σ | I | + K3 ・ ・ ・ ・ Considering the case where the current flows from one location during 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 set value. In this way, the digital converter
Make the force voltage recognition range narrower than the saturation region of optical CT.
By setting, 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, an example in which the optical CT and the magnetic CT are combined is shown, but the same can be done when all the CTs of the banks and the load lines are also optical CTs. In either case, there is no need 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 input voltage recognition range of the digital converter of the current differential discriminator is set to the optical C.
By making the area narrower than the saturation region of T, expensive optical CT
It is intended to prevent malfunctions due to the difference in the clip characteristics of the optical CT without using, and to contribute 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 Yasuhisa Sakurai 59-1-6 Kashiwai-cho, Kasugai-shi, Aichi Hosoi Heights 302

Claims (1)

(57) [Claims] 1. A plurality of optical CT which is constituted by the core and the optical magnetic field sensor for detecting a fault current in a position surrounding the section for each severing sections of the bus conductor in a substation or optical CT and bushings,
Sing CT, a combination of a magnetic CT, such as wire-wound CT (hereinafter, referred to as optical CT, etc.) previously attached to, the optical CT
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 converting the current value measured by , Above digital conversion, vector
Current differential judgment that calculates sums and scalar sums and judges accident points
The input voltage recognition range of the digital converter of another device
A fault section detection system for a substation, characterized in that the output voltage is narrower than the saturated area.