JPS61224824A - Protective relay - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a protective relay that uses a digital computer to determine the operating state of a power system and protect equipment.

[Conventional technology]

FIG. 4 is a principle diagram showing a protective relay device disclosed in, for example, Japanese Patent Application Laid-Open No. 55-23779. 23 is a scalar addition element that adds the rectified and smoothed current amounts.

24 is a rectification and smoothing element that rectifies and smoothes the vector addition amount; 25 is a comparison judgment element that compares and judges the vector addition amount (operation amount) and the scalar addition amount (suppression amount); and 26 outputs the judgment result. It is an output element.

Next, the principle of operation in Fig. 4 is expressed by the calculation formula (11, (2)).
)+4...(1)(III"ll = +I'
+ + +death"l +, X 1II7+ -II'
-'+1) ... (2) Here, I- is the amount of current sampled at one time, and the subscript i is the terminal number.
be. Also, ΣI+ is vector addition, llI'l+
Σ1lIi'll means rectification smoothing, Σ1lIi'll means neutral addition, and KotKttKt is a constant. In the above example, the sampling frequency is set to 12 of the system frequency.
Double (30° sampling).

Next, the operation shown in FIG. 4 will be explained. That is, each sampled current flow rate 11 of the power system is rectified and smoothed by the rectification and smoothing element 21 as shown in equation (2).
I+lI, which is scalar-added by the scalar addition element 23 to become ΣlII+Il. Further, the respective current amounts I+ are vector-added by a vector addition element 22, further rectified and smoothed by a rectification and smoothing element 24, and 11Σ
I+If. In the comparison/judgment element 25, the output ΣIf It It of the scalar addition element 23 is multiplied by an appropriate constant, and the output 11ΣWork%1 of the rectification and smoothing element 24 is
Along with 1, Otori is judged by equation (1). As a result, if equation (1) is established, an operation signal is output from the comparison/judgment element 25. The output element 26 gives the operation signal an appropriate time limit and outputs it as a final operation output signal.

In the above equation, 4 in equation (1) is the minimum operating value, K1
Since we are trying to obtain the differential characteristics shown by the solid line P in the operating characteristics of a general differential protection relay in Figure 5 by taking the ratio as Since variations occur in , it is necessary to perform rectification and smoothing calculations as shown in equation (2), for example. By calculating this equation (2), a form similar to four-phase rectification is achieved, and the operating value error can be reduced, and variations in the differential characteristics due to the sampling phase can be reduced.

[Problem that the invention seeks to solve]

Conventional protective relays are configured as described above, so
For example, when handling multi-terminal information that is applied to bus bar protection, it takes an enormous amount of time to process equation (2), and in order to avoid malfunctions due to CT saturation, etc., depending on the amount of current, It was necessary to automatically change 8th grade to 4th grade. Therefore, there are problems such as severe restrictions on operating time and processing capacity of the digital computer.

This invention was made to solve the above-mentioned problems, and it has easy calculation processing, high-speed response, and CT
The purpose is to obtain a protective relay that operates stably even when saturated.

[Means for solving problems]

The protective relay according to the present invention uses the principle equation (3) below, and the output of the first comparison judgment element that judges equation (3);
The arithmetic circuit is configured to output the final output by inputting the output of the second comparison judgment element determined by equation (4) to the inhibit element.

Max(II+'l, lIt'-"l)-m6
XMax(lΣIs'l, IΣIi'-1a, ,
≧ 0... (3) 11ΣIs If≧4... (4) However, chest, 6
are constants, and L and It represent the current sample amounts before times la and tb, respectively. Hereinafter, the first comparison and determination element will be referred to as a ratio lock element, and the second comparison and determination element will be referred to as a differential element.

[Effect]

By using this principle formula, it becomes possible in principle to perform judgment calculations on the ratio lock element (first comparison judgment element) using the instantaneous current value of the system.

[Embodiment] "An embodiment of the present invention will be explained below with reference to the drawings. First, in FIG. a rectifying element that rectifies, 3 a first storage element that stores the addition amount of the rectified vector addition element 1;
4 is a first maximum value deriving element that selects the maximum value (differential amount) of the output of the rectifying element 2 and the output of the first storage element 3;
is a rectifying element that rectifies the sampled current amount of each system; 6 is a second maximum value deriving element that selects the instantaneous maximum value of the rectified current amount; 7 is a memory for storing the selected instantaneous maximum value. The second storage element 8 is the maximum value (
9 is a first determination element that determines the level based on the magnitude relationship between the differential amount and the suppression amount and outputs it; lO is the addition of the rectified vector addition element 1; 29f of the amount and the addition amount of several samples ago stored in the first storage element 3! , effective value calculation element that calculates the sum, 11
12 is a second determination element that determines and outputs the magnitude relationship between the sum of squares and the reference value; 12 is an inhibit element that locks the output of the second determination element 11 with the output of the first determination element 9; 14 is a ratio lock element (10th comparison determination element) that makes a determination based on the principle formula (3), and 14 is a differential element (second ratio-determination element) that makes a determination based on the principle formula (4).

Next, the operation shown in FIG. 1 will be explained. First, when the block diagram of FIG. 1 is programmed using a digital computer, it can be expressed as the flowchart of FIG. 2.

That is, in step 1, the vector addition amount E of the current amount knee of each system sampled and quantized at one time is
D is calculated by the vector addition element 1, and in step 2, the maximum value ER of the absolute value of each of the current amounts II is calculated by the second maximum value derivation element 6. Next, in step 3, the vector addition amount ED and the vector addition amount ED before time t1 are calculated.
'-'' maximum value E,, tL < differential amount) is calculated by the first maximum value deriving element 4, and in step 4, the maximum value E,, tL < differential amount) is calculated.
The maximum value El calculated by and the maximum value El before time ib
The maximum value Ell (suppression amount) is calculated by the third maximum value deriving element 8, and in step 5, the differential amount ED'' is calculated by m.

Multiply the suppression amount ERt' and compare the magnitude relationship between
The first determination element 9 determines that the ratio lock element is in operation at 3, and that the ratio lock element is inoperative in other cases. In step 6, the addition amount EDt of the vector addition element 1 and t・
Vector addition amount ED1-1'' before time squared N E
/' is calculated by the effective value calculation element 10, and in step 7, the magnitude relationship between the sum of squares E1 and the constant number is compared, and if the former is larger or equal, the differential element is operated, and the other In this case, the second determination element 11 performs an operation to disable the differential element. In step 8, based on the determination results of steps 4 and 7, a final output is made as a total operation only when the ratio lock element 13 is inoperative and the differential element 14 is in operation; Alternatively, the inhibitor element 12 determines whether to make a final output as a comprehensive return. Note that the calculation order of steps 1 and 2, steps 2 and 3, steps 3 and 4, and steps 2 to 5 and steps 6 to 7 may be reversed. Also, when the current amount N1 of each system changes in a positive wave over time, 1. It is obvious that if E/' is set appropriately, the sum of squares E/' becomes the sum of squares of the effective values, so the explanation here will be omitted.

When tb=90° (E♂>' + < EDt-t
b,! −IEDI (sia”ω is 10S2ωt)=I
EDl. Furthermore, each determination section in FIG. 2 can perform verification multiple times (as this is self-explanatory, the explanation will be omitted) as a measure for stabilizing the characteristics.

According to this invention, the solid line in (a) in FIG. 5 is determined by the above-mentioned principle equation (3), and the dotted line in FIG. Similar ratio differential characteristics are obtained. In addition, since the principle formula (3) is determined only by the ratio of the differential amount BD" and the suppression amount EIL/*, calculations can be made based on the instantaneous value, and the solid line in (a) is a straight line passing through the origin, so the minimum operation is possible. It has the characteristic that the value 4 and the ratio - can be set independently.Also, when the terminal currents are not in the same phase or out of phase as shown in Figure 3, the opening time may vary regardless of the operating range. By compensating for the time domain in which the suppression amount Ell exceeds the vector addition amount ED (the shaded area in Fig. 3) with the stored vector addition amount ED1-'', this region can be eliminated and the operating range determined by the phase characteristics. is prevented from becoming narrow due to instantaneous calculation. Furthermore, in the event of an external fault, when an excessive current passes through and the outflow side CT is saturated, the C7 secondary current decreases instantaneously, and an excessive differential amount appears to occur. In order to cancel the excessive differential amount that occurs when It continues and does not lead to malfunction.

In addition, in the embodiment described above, the sum of squares calculation was used for the determination of the above-mentioned formula (4), but since it is a level determination in principle, the rectification and smoothing calculation of the formula (2) explained in the conventional embodiment is used. Or,
An integral calculation as shown in equation (5) may be used, and the same effect as in the embodiment described above can be achieved.

11 It ll = +lf 11'-"=1ΣI+
I + IΣLl +IΣL1 +... ・・
・(5) Il1 [Effects of the Invention] As described above, according to the present invention, the arithmetic circuit is configured in such a way that calculation determination can be made based on the instantaneous value of the system current amount, so that the above-mentioned (2) can be achieved. This eliminates the need for rectification and smoothing calculations such as those in the equation, which greatly reduces calculation time and has the effect of allowing prompt handling of accidents. Furthermore, since it is possible to respond quickly, the processing load on one digital computer is reduced. Furthermore, there are effects such as the ability to easily obtain very stable characteristics against OCT saturation phenomena during external accidents.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the operating principle of a protective relay according to an embodiment of the present invention, FIG. 2 is a 70-chart diagram of the embodiment of FIG. 1, and FIG. 3 is a diagram of the compensation principle of phase characteristics of the present invention. FIG. 4 is a block diagram of the operating principle of a conventional protective relay, and FIG. 5 is a diagram showing the operating characteristics of a general protective relay. In the figure, 1 is a vector addition element, 2 is a rectification element, and 3
is a first storage element, 4 is a first maximum value derivation element, 5 is a rectification element, 6 is a second maximum value derivation element, 7 is a second storage element, 8 is a third maximum value derivation element, 9 is the first determination element;
10 is an effective value calculation element, 11 is a second judgment element, 12 is an inhibit element, 13 is a ratio lock element (first comparison judgment element), and 14 is a differential element (second comparison judgment element). Patent applicant: Patent attorney representing Mitsubishi Electric Corporation 1) Hiroshi Sawa, ``Otsuguchi (2 others) IJ, 2-jj Figure 3 max (111 + I21: 111 + 1zl xm. IR (suppression electric))

Claims (3)

[Claims] (1) Select a vector addition element that takes in the amount of current from multiple systems and adds the vector, a first storage element that stores the addition amount of the vector addition element, and the instantaneous maximum value of the absolute value of the amount of current. a second maximum value deriving element; and a second maximum value deriving element that stores the maximum value selected by the second maximum value deriving element.
a first comparison/judgment element that takes in each output of the vector addition element, the first storage element, the second maximum value derivation element, and the second storage element, compares and judges, and outputs the vector; a second comparison and judgment element that takes in the addition amount of the addition element and the output of the first storage element, determines the level, and outputs it; and an inhibitor that inhibits the outputs of the first and second comparison and judgment elements to produce a final output. Protective relay with elements. (2) As a configuration of the first comparison determination element, the second
a third maximum value derivation element that takes in the maximum value derivation element and the output of the second storage element and outputs the maximum value; an output of the third maximum value derivation element; and a vector addition element;
A first maximum value deriving element that derives the maximum value from two outputs of the first storage element; and a first determination element that takes in the output and makes a comparative determination. Protective relay as described in section. (3) The configuration of the second comparison/determination element includes an effective value calculation element that takes in the outputs of the vector addition element and the first storage element and calculates the sum of squares, and a predetermined value for the output of the effective value calculation element. 2. The protective relay according to claim 1, further comprising a second determination element for comparison with a constant value of .