JPH0159811B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a digital protection device, and particularly to a digital protection device that converts voltage and current of a power system into digital information.
This invention relates to an improvement in a digital protection device that processes a target protection element by performing necessary calculations using a computer.

In recent years, there has been a very active movement to use microcomputers to protect and control power systems.
Research is progressing in various places. One such method is to convert the voltage and current of the power system into digital information, process the protection elements, and determine whether or not the accident occurred within the protected area.

The protection elements can be roughly classified into main detection elements for main protection, accident detection elements for main protection, main detection elements for backup protection, accident detection elements for backup protection, etc. The number of these protection elements becomes enormous when considering the configuration of one protection method. Therefore, it is very important to increase the number of processable protection elements by thinning out the information used to process the protection elements.

By the way, conventionally, as shown in FIG.
The pre-processing shown below is applied to the data after each pre-processing, and the product calculation means 2 performs a product calculation, and the result is integrated by a certain number in the integral calculation means 3. Assuming that it is proportional to the effective value, the operating limit is determined. I was trying to get value.

Next, it will be explained more specifically. In other words, if the input information is a(t)=Asin(ωt) b(t)=Bsin(ωt+θ)...(1), the processing required to remove harmonics and phase shift included in this input information is Since it is necessary to perform this preprocessing, the preprocessing means 1a and 1b respectively perform this preprocessing. Next, the outputs after the preprocessing are designated as a ₁ (t) and b ₁ (t), and the product calculation means 2 performs a product calculation of these. Expressing this as a formula, a ₁ (t), b ₁ (t) = kA・Bsin (ωt+θ ₁ )・sin (ωt
+θ ₂ )=1/2k·A·B {cos (θ ₁ −θ ₂ ) −cos (2ωt+θ ₁ +θ ₂ )} (2). One cycle of information corresponding to a frequency 1/2 times the frequency of this input information is integrated by the integral processing means 3 to obtain a quantity proportional to A.B.cos (θ ₁ −θ ₂ ). However, in this case, it is necessary to process all protection elements within a time interval determined by the sampling frequency. By the way, the processable protection element N
is expressed by the following equation, where ΔT is the sampling time interval and Δt is the time required to process one protection element.

N=ΔT/Δt…(3) If the number of protection elements that actually require processing is M, and if the sampling time interval ΔT cannot be changed for pre-processing such as harmonic removal and phase shifting, then M It becomes necessary to install a number of computers corresponding to /N. This is economically unfavorable.

The present invention has been made in view of the above, and an object thereof is to provide a digital protection device that can increase the number of protection elements.

A feature of the present invention is that after preprocessing the power system information sampled at regular time intervals using a preprocessing means, the frequency of the preprocessed input information is 1/n (n is an integer) 1 per frequency cycle
The product operation of each of the above input information is performed using the product calculation means, the result is integrated for 6 samples using the integral calculation means, and the operation of the target protection element is determined based on the result. It is in the point that I made it.

The present invention will be explained in detail below using the embodiment shown in FIG.

FIG. 2 is a block diagram of essential parts showing one embodiment of the apparatus of the present invention. First, the input information a(t) and b(t), which are power system information and are shown by the above equation (1), are preprocessed by preprocessing means 1a and 1b, respectively. In addition, in order to remove the second harmonic in equation (2), the sampling interval is set to 30 degrees in electrical angle, and the product operation of the respective preprocessed outputs is performed every five times the sampling interval using the product operation means. Do it in 2. In this case, θ ₁ = θ ₂
= 0, 2ωt+θ ₁ +θ ₂ are 0, 300, 600,
900, 1200, 1500 degrees, and when expressed as electrical angles in the range of 0 to 360 degrees, they are 0, 300, 240, 180,
120 and 60 degrees, and the sum of these cosine values is zero. In this way, the calculation of equation (2) is performed every five times the sampling interval, and the result is integrated by the integral calculation means 3 for 6 samples. As a result, A・B・cos(θ ₁
−θ ₂ ) can be obtained. Then, a determination process is performed based on this result.

4 to 6 in FIG. 2 are input processing means for performing product calculations every five times the sampling interval;
The first input processing means adds 1 to the number of data inputs S each time data is input, and the second input processing means 5 determines whether the new number of data inputs S becomes equal to S ₀ (5 in the embodiment). Determine whether S=S ₀
In this case, the third input processing means 6 sets S=0 and provides the input data to the product calculation means 2. Further, when the second input processing means 5 determines that S≠S ₀ , the process returns to the next sample. This allows the product operation to be performed every five times the sampling interval.

By processing as described above, the number of protectable elements that can be processed can be increased approximately five times.
Note that in this technical field, it is a well-known technique to provide some kind of timer for the output of the protection element in order to increase operational reliability due to transient phenomena of input information, etc., and this specification and drawings do not specifically mention the timer. However, in this embodiment, as described above, processing equivalent to a timer is performed at the time of input information selection, so by adjusting the processing of the timer on the output side, the number of protection elements is increased by five times. However, the processing time for each protection element does not increase.

In the above embodiment, the product operation is performed every five times the sampling interval (1/5 of the sampling frequency).
Although the explanation has been given using the example of the case (1/10 times the sampling frequency), the same can be said for the case where the product operation is performed every 10 times the sampling interval (1/10 times the sampling frequency). Generally speaking, the same thing can be said for n times 5. Note that if the frequency of the input information is 50 Hz and the sampling interval is 30 degrees, performing the process of equation (2) once every 5 times the sampling interval means that the frequency is
Corresponds to 120Hz, and the product operation is performed every 10 times the sampling interval above (1/10 of the sampling frequency).
In the example, this frequency is 60Hz. In this way, the frequency f _s indicating the interval at which the product operation is performed is
When the frequency of input information is f, it is expressed as f _s =f·12/5·1/n (4). By doing this, it is possible to increase the number of processing protection elements.

As explained above, according to the present invention, processing capacity can be increased without delaying the processing time of each protection element and without performing complicated processing such as changing the processing interval depending on the processing content. can.

Furthermore, according to the present invention, the frequency of the input information is 12/
Since the product operation and the integration of 6 samples of the result of the product operation are performed at intervals of 1/n of 5 (n is an integer), the frequency characteristics near the fundamental wave contained in the input information are not impaired compared to the conventional method. do not have.

As described above, according to the present invention, since the processing capacity can be increased without changing the hardware scale, the economic effect is extremely large, and the protection elements can be increased.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the main parts of a conventional protection device, and FIG. 2 is a block diagram of the main parts of an embodiment of the protection device of the present invention. 1a, 1b... preprocessing means, 2... product calculation means, 3
... Integral calculation means, 4 to 6... Input processing means.

Claims (1)

[Claims] 1. In a device that protects and controls an electric power system using electric power system information sampled at predetermined time intervals, a preprocessing means for preprocessing the electric power system information, and a preprocessing means for preprocessing the input information preprocessed by the preprocessing means. an input processing means that takes in each of the input information once per cycle of a frequency that is 1/n (n is an integer) times 12/5 of the frequency; and each of the input information that is taken in through the input processing means. A product calculation means for performing a product calculation, an integral calculation means for integrating six samples of the result of the product calculation by the product calculation means, and a determination means for determining an accident from the result integrated by the integral calculation means. A digital protection device characterized by: