JPS6315814B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention uses the principle of differential protection to detect the presence or absence of failures in power transmission and distribution lines, mainly consisting of light emitting elements that convert the amount of electricity into light amounts and communication lines for transmitting the amount of light from the light emitting elements. This relates to an optical differential protection relay system that uses .

Conventionally, as a protection method for protecting power transmission and distribution lines using communication lines stretched between substations, there is an indicator line differential protection relay system that uses a conductor called an indicator line. It is possible to protect terminals or the number of terminals up to 3 terminals, but if the number of terminals exceeds 3 terminals, transmission loss in the display line, electromagnetic induction from strong electric circuits, etc. become problems, so it is currently not applicable. .

On the other hand, the uneven distribution of electricity demand and the expansion of power systems inevitably require multi-terminal transmission and distribution lines, and currently, the legally protected relay system is no longer a viable option for multi-terminal systems. I can say that I am getting used to it. The conventional display line protection relay system will be described below. Figure 1 shows a multi-terminal power transmission and distribution line to be protected.
In this diagram, protection for up to 5 terminals is considered.

In Figure 1, 1A, 1B, 1C, 1D, 1E
indicates the CT installed at each substation. Figure 2 shows
This is a diagram for the case where the protection in Figure 1 is performed by differential protection using display lines, and in the figure, 10A, 10B,
10C, 10D, and 10E are transformers that transform the input from the CT, and 20A, 20B, 20C, and 20D are indicator lines that are stretched from each substation to the E substation, which is the central substation. show. 30
A, 30B, 30C, and 30D are transformers that transform the input transmitted via the display line from each substation;
50 is a differential circuit that combines all CT inputs from five substations to create a differential circuit. As can be seen from this diagram, the input from each substation is the transformer 30.
Since they are connected via A, 30B, 30C, and 30D, the more the number of terminals increases, the more display line circuits on the other side will be connected, and the amount absorbed by that part will increase. , the amount of data that must be transmitted will inevitably increase, which will accelerate the saturation of the CT and make it impossible to maintain differential transmission. On the other hand, display lines 20A, 20
B, 20C, and 20D are often stretched parallel to power transmission and distribution lines, and the error voltage that appears between the display line pairs due to electromagnetic induction from these high-power circuits is generated by the differential circuit 50.
The current situation is that the differential circuit 50 takes this into account and lowers its sensitivity.This also increases the amount of transmission, which accelerates the saturation of the CT Because it acts in the direction,
The differential cannot be maintained in the excessive input range.

Therefore, it is currently possible to protect up to three terminals by applying a suppressing force proportional to the amount of input transmitted from each substation (not shown in Figure 2). If you exceed 3 terminals,
Transmission loss and the effects of electromagnetic induction from high-voltage circuits
This speeds up the saturation of the CT, and protection in the excessive input range becomes a problem.

The purpose of the present invention is to protect multiple terminals by using a medium called light, which is essentially unaffected by electromagnetic induction and the impedance of the communication line circuit on the other side due to an increase in the number of terminals. FIG. 3 shows a circuit configuration according to the present invention. In the figure, 3A, 3B, 3C, 3D, and 3E are transformers that transform the input from the CT at each substation; 4A, 4B,
4C, 4D, and 4E are length compensators to make the distances from each substation to the operation determination unit 200 at the E end appear equal; 5A, 5B, 5C, 5D, and 5E are light emitting elements 6A, 6B, 6C, 6D, 6E
Light amount converter, 7A, 7B, which converts the input amount to
Reference numerals 7C, 7D, and 7E indicate optical fiber lines installed between each substation, and 100 indicates an optical coupler that couples the light from each optical fiber line and provides judgment input to the operation judgment unit 200.

In Fig. 3, in order to equalize the degree of attenuation of the electric quantity transformed by the CT at each end to the operation determination unit 200 installed at the E end, , 4D, and 4E and which have passed through this circuit are adjusted so that if they have the same magnitude, the input quantities converted into light quantities in the optical coupler 100 and the operation determination section 200 will also be equal. It is becoming.

The amount of electricity passing through the length compensation circuits 4A, 4B, 4C, 4D, 4E is then 5A, 5B, 5C, 5D, 5
E light intensity converter and 6A, 6B, 6C, 6D, 6E
7A, 7B, 7C, 7D, 7A, 7B, 7C, 7D, 7
The light of E is introduced to the optical coupler 100 via an optical fiber which is a medium for transmitting the light of A,
The amounts of light from all ends B, C, D, and E are combined, and the combined value of the amounts of light is finally introduced into the operation determining section 200, which determines the degree of pulsation of the light. This will determine whether there is an internal or external failure. FIG. 4 shows the output from the optical coupler 100 when an external failure occurs, considering only the two substations at the A end and B end. Also, Figure 5 shows A, similar to Figure 4.
The output from the optical coupler 100 when an internal failure occurs when considering only the B end is shown.

Next, to explain Fig. 4, the light amount converted according to the amount of current input under a constant light bias appears as a change in the amount of light that pulsates at the commercial frequency. Since the time periods when the light intensity is strong and weak and the time periods when the light intensity at the B end is strong and weak are completely opposite, the light amount combined by the optical coupler is a constant level light amount with no pulsation, as shown in Figure 4 (c). Become.

On the other hand, to explain the internal accident in Figure 5,
The time period for the change in the light amount at the end and the B end is the same, and when combined by an optical coupler, the light amount changes in the form of adding the pulsation at both ends, as shown in Figure 5 (c).

For the sake of simplicity, the above explanation only deals with two terminals as a representative, but the principle remains the same even if the number of terminals increases; an external failure causes no pulsation of light, and an internal failure causes no pulsation of light. Appears in fully synthesized form.

On the other hand, the optical fiber 7A, which is a light transmission medium,
In principle, 7B, 7C, 7D, and 7E are located in a frequency band where light is not affected by electromagnetic induction from electric circuits, so in extreme cases, they can be wrapped around power lines and stretched between each end. That's a good reason.

In short, the present invention proposes an optical differential protection relay system using light intensity synthesis, with the aim of achieving differential operation while eliminating problems of electromagnetic induction and transmission loss due to multi-terminals.

Note that the method of determining internal and external accidents based on the presence or absence of pulsation used in the final operation judgment is not limited to the present invention, but can also be used as a principle in conventional differential protective relay systems that use only electrical quantities. In this text, we have considered an electrical attenuator to equalize the amount of attenuation from each end, but it goes without saying that this can also be done with a light attenuator that adjusts the amount of light.

As described above, according to the present invention, fault currents from a plurality of current transformers are compensated by a length compensator and then converted into a light quantity, and a fault signal is transmitted as an analog quantity of light quantity via an optical fiber line. synthesize,
The system is configured to determine whether an internal or external accident is occurring based on the presence or absence of pulsation in this composite signal, and multi-terminal protection, which was previously difficult due to current transformer saturation caused by electromagnetic induction, is now possible. This has the effect of making it possible.

[Brief explanation of the drawing]

Figure 1 is a line diagram showing a multi-terminal power transmission line to be protected, Figure 2 is a circuit diagram showing an example of a conventional protection circuit configuration using indicator lines, and Figure 3 is a circuit diagram of a protection circuit configuration according to the present invention. A circuit diagram showing an example, FIG. 4 is a diagram showing the amount of light per hour when an external failure occurs, and FIG. 5 is a diagram showing the amount of light per hour when an internal failure occurs. In the figure, 1A, 1B, 1C, 1D, 1E are CTs installed in each S/S, 4A, 4B, 4C,
4D, 4E are length compensators, 5A, 5B, 5C, 5
D, 5E are light quantity converters, 6A, 6B, 6C, 6
D, 6E are light emitting elements, 7A, 7B, 7C, 7D,
7E is an optical fiber line, 100 is a coupler, 200
is a motion determination section. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1 A plurality of current transformers installed in a protected area of a power system, a plurality of transformers that transform the output of the plurality of current transformers, and a plurality of transformers that compensate the output of the plurality of transformers to a predetermined output, respectively. a length compensator; a plurality of light emitting elements that convert the electrical outputs of the plurality of length compensators into a predetermined amount of light via a plurality of light amount converters; a plurality of optical fiber lines to be transmitted from the optical fiber lines to the other end side; an optical coupler that couples the other end side of the plurality of optical fiber lines to combine the amounts of light of the plurality of optical fiber lines; and an output from the optical coupler. An optical differential protection relay device comprising: an operation determining unit that inputs a composite signal generated by the protective section and determines whether an internal failure or an external failure occurs in the protection section based on the presence or absence of pulsation in the composite signal.