JPH0591646A - Under voltage relay device with current compensator - Google Patents

Abstract

PURPOSE:To shorten a testing time by detecting an under-voltage of a power system by seventh calculating means when any of first second and fourth deciding means outputs a decision result. CONSTITUTION:First deciding means 10 decides whether an absolute value <=a voltage settled value of a voltage vector is satisfied or not. Second deciding means 12 decides whether a ratio <= a voltage settled value of the ratio of the absolute value of a composite value of a current vector and a voltage vector to that of a current vector is satisfied or not. Fourth deciding means 17 decides whether (the absolute value of the voltage vector) <= (an added value of the absolute value of a composite value of the impedance settled value and the current vector to a voltage regulated value) is satisfied or not. When any of the first, second and fourth means 10, 12, 17 outputs a decision result, seventh calculating means 19 detects an under-voltage of a power system. Thus, the operating voltage value of a characteristic part applied by a compensating voltage is easily obtained to shorten a testing time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an undervoltage relay with current compensation of a protection relay for detecting an accident in a power system.

[0002]

2. Description of the Related Art FIG. 8 shows, for example, "Relay Practics Series Volume 2 Transmission / Distribution Protective Relay System" issued by Densho Shoin Co., Ltd. on January 25, 1976. FIG. 90 is an operating characteristic diagram of the conventional power system accident detection relay shown in FIG. 90. (Note that regarding the notation of current and voltage vectors,
Since the dot I indicating the current vector and the dot V indicating the voltage vector cannot be used due to the limitation of terms used, "V" and "I" are simply used in the text. ) In this figure, the horizontal axis is the current vector (I) direction, and ZI _L ∠ θ _L is the vector obtained by phase-shifting the current vector by the path angle θ _L of the transmission line L, and multiplying it by the settling value Z given in advance , V is the voltage vector at the relay installation point, φ is V and I
The angle formed by K ₁ , K ₁ is a preset voltage set value.

Next, the operation will be described. When an accident occurs in the transmission line in which the relay is installed, the voltage V of the relay installation advances by θ _L due to the current I, so that the phase is almost in phase with ZI _L ∠θ _L and the operation enters the shaded line. Also, if current flows even if the voltage does not drop, | ZI _L ∠θ _L
Since | becomes large, V enters the diagonal line and operates. This is generally called an undervoltage relay with current compensation and is used as a fault detection relay in the power system.

[0004]

Since the undervoltage relay with current compensation, which is a conventional fault detection device for a power system, is configured as described above, current compensation is applied when conducting an operation characteristic test of the relay. When the data of the characteristic part (A part in FIG. 8) is taken, the operating voltage value cannot be easily obtained, and it is necessary to perform conversion as shown in equation (1), which causes a problem that it takes time during the on-site test. .

[0005]

[Equation 1]

The present invention has been made in order to solve the above-mentioned problems, and the operating voltage value of the characteristic portion subjected to the current compensation is easy and irrespective of the angle θ formed by the voltage V and the current I. The purpose is to obtain an undervoltage relay with current compensation that can be obtained.

[0007]

In an undervoltage relay with current compensation according to the present invention, a vector obtained by phase-shifting a current vector of a power system by a line angle θ _L of a transmission line is I _L ∠θ _L ,
When the voltage vector is V, the preset voltage settling value is K ₁ , and the impedance settling value is Z, first determining means for determining whether or not the absolute value of the voltage vector ≦ voltage settling value, and the current vector voltage A third determination means for determining whether the ratio of the absolute value of the combined amount of the vector and the absolute value of the current vector ≦ the voltage settling value, and the second determination for determining whether the combined amount of the current vector and the voltage vector ≧ 0. Means, fourth judging means for judging whether or not absolute value of voltage vector ≦ impedance settling value and absolute value of combined amount of current vector and voltage settling value, first judging means, or second or second Undervoltage detection means for detecting an undervoltage of the power system when the determination result is output by any one of the fourth determination means.

[0008]

The function of the current compensation in the present invention is K ₁ + | ZI _L ∠
Since the circular characteristic is centered on the origin with the radius of θ _L |, the maximum operating voltage | V | in the operating region is constant regardless of the angle φ formed by the voltage vector and the current vector I, and its value is K ₁
Since + | ZI _L ∠θ _L |, it becomes easy to obtain data for that portion.

[0009]

EXAMPLES Example 1. An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, B is a bus bar, L is a protected transmission line, CB is a circuit breaker connecting the bus line B and the transmission line L,
CT is a current transformer that transforms the current flowing through the power transmission line L to a predetermined magnitude, and PT is a voltage transformer that similarly transforms the voltage to a predetermined magnitude.

Further, reference numerals 1 and 2 are input converters for converting inputs from CT and PT on a relay side, reference numerals 3 and 4 are filter portions, and a current filter portion has a function of phase shifting by θ _L. . Reference numerals 5 and 6 are sample and hold circuits, 7 is a switching circuit called a multiplexer circuit, and 8 is an analog-digital conversion circuit. The output of 8 is converted into a digital value, and the subsequent calculation can be performed by digital calculation.

First calculating means for calculating a, is 10 | | [0011] portion 20 surrounded by a chain line shows the processing circuitry of the software but 9 | V V | first determining means for determining ≦ K _1, 1
1 is the second for calculating | I _L ∠θ _L × V / | I _L ∠θ _L |
Calculating means, 12 is second determining means for determining | I _L ∠θ _L × V / | I | _L ≦ K ₁ , 13 is third calculating means for calculating I _L ∠θ _L · V, and 14 is I Third judging means for judging _L ∠θ _L · V ≧ 0, 15 is fourth calculating means for calculating | ZI _L ∠θ _L |, and 16 is _first calculating K ₁ + | ZI _L ∠θ _L | 5 computing means, 17 is | V | ≦ K ₁ + | ZI _L ∠θ _L
The fourth judging means for judging |, and the sixth judging means 18 calculates the logical product of the judgment signals of the second to fourth judging means 12, 14, and 17.
Arithmetic means, 19 is a seventh arithmetic means for calculating the logical sum of the outputs of 10 and 18.

In FIG. 1, the second computing means 11 has a | I _{L
∠θ L × V | / | I} L ∠θ L | becomes performs computation but, I _L
Since ∠Shita _L × V denotes the outer product of vector I _L ∠Shita _L and V, I _L ∠θ When the angle of the _L and V and θ second arithmetic means 11 || I _L ∠θ _L | · | V | sin θ | / | I _L ∠
θ _L | = || V | sin θ | is calculated. Therefore, in the second determination means 12, || V | sin θ | ≦ K ₁
Is determined, and the hatched portion in FIG. 2 is shown in the characteristic diagram.

Further, I _L ∠θ _L performed by the third computing means 13
V is the inner product of the vector I _L ∠θ _L and V, and similarly,
| I _L ∠θ _L | × | V | cos θ is calculated. The third judging means 14 judges whether this result is positive or negative. When the result is positive, θ ≦ 90 ° is indicated, and the characteristic diagram shows the shaded area in FIG.

The circuits of the fourth and fifth calculating means 15 and 16 and the fourth judging means 17 make a simple size judgment without directivity, and the output of the fourth judging means 17 is radius K ₁ + | as shown in FIG. Z
I _L ∠ θ _L | will be shown within the circle. It is obvious that the logical product 18 of the outputs of the above three judging units is obtained as shown in FIG. Further, the first calculation means 9 and the first determination means 1
The result of 0 indicates the inside of the circle having the radius K ₁ shown in FIG. 6, and the logical sum of this result and the result of the logical product by the sixth calculating means 18 is the seventh
The characteristics shown in FIG. 7 are obtained by the calculation means 19.

In the above calculation, it is necessary to calculate the outer product and the inner product of the vector, but the digital relay using a microprocessor currently in practical use can perform the following calculation.

(Outer product) When the two vectors I and V are sampled at an electrical angle of 30 °, for example, the calculation shown in the equation (2) is performed. i (t) * v (t-3) -i (t-3) * v (t) (2) i (t) and v (t) are the instantaneous values of the voltage vector current V and the vector I at time t. , I (t-3), v (t-3)
Indicates an instantaneous value three samples before the time t, that is, an electrical angle of 90 °. Therefore, the equation (2) is applied as follows. θ is an angle formed by the current vector I and the voltage vector V is expressed by the following equation.

[0017]

[Equation 2]

By dividing the equation (2) by | I | and taking the absolute value, | V | sin θ can be calculated. (Inner product) Similarly, the calculation shown in Expression (3) is performed. i (t) × v (t) + i (T−3) × v (t−3) (3) When the equation (3) is rewritten, the following equation is obtained.

[0019]

[Equation 3]

By judging whether this is positive or negative, it can be judged whether θ is within 90 ° or more.

[0021]

As described above, according to the present invention, the current compensation has the circular characteristic centered on the origin with the radius of K ₁ + | ZI _L ∠θ _L | V |
(A in FIG. 7) is constant regardless of the angle φ formed by the voltage vector and the current vector I, and its value is K ₁ + | ZI _L ∠θ _L |
Therefore, it becomes easy to obtain the data of that portion, and there is an effect such as shortening the test time.

[Brief description of drawings]

FIG. 1 is a block diagram according to an embodiment of the present invention.

FIG. 2 is a part of the characteristic diagram of the present invention (| V | sin ≦ K
It is explanatory drawing which shows ₁ ).

FIG. 3 is a part of the characteristic diagram of the present invention (| I _L ∠θ _L |. |
It is explanatory drawing which shows V | cos> = 0.

FIG. 4 is a part of the characteristic diagram of the present invention (| V | ≦ K ₁ + | Z
I _L ∠ θ _L |)

FIG. 5 is a part of the characteristic diagram of the present invention and is shown in FIGS.
It is explanatory drawing which shows the logical product of each characteristic diagram shown in FIG.

FIG. 6 is an explanatory diagram showing a part (| V | ≦ K ₁ ) of the characteristic diagram of the present invention.

FIG. 7 is a diagram obtained by taking the logical sum of FIG. 5 and FIG. 6, and is an explanatory diagram showing a characteristic diagram of the present invention.

FIG. 8 is an explanatory diagram showing characteristics of a conventional undervoltage relay with current compensation.

[Explanation of symbols]

First calculation means 10 for calculating a | | V | ≦ K ₁ second judging unit 11 judges _{| I L ∠θ L × V V} | bus L protected transmission line 8 analog to digital conversion circuit 9 in B power system | Second calculating means for calculating / | I _L ∠θ _L | 12 | II _L ∠θ _L × V | / | Second determining means for determining I _L ∠θ _L | ≦ K ₁ 13 I _L ∠θ _L Third calculation means for calculating V 14 I _L ∠θ _L · Third determination means for judging V ≧ 0 15 | ZI _L ∠θ _L | Fourth calculation means 16 K ₁ + | ZI _L ∠θ _L Fifth calculating means for determining | 17 | V | ≦ K ₁ + | ZI _L ∠θ _L |
Judgment means 18 Sixth calculation means for calculating AND circuit 19 Seventh calculation means for calculating OR circuit

Claims (1)

[Claims] 1. A voltage settling value in an undervoltage relay device with current compensation for protecting the power system by digitally calculating a vector of a voltage of the power system and a current vector phase-shifted by a line angle of a transmission line. And first setting means for setting the impedance settling value to determine whether the absolute value of the voltage vector ≦ the voltage settling value, and the ratio of the absolute value of the combined amount of the current vector voltage and the vector and the absolute value of the current vector. ≦ Third determination means for determining whether it is a voltage set value, second determination means for determining whether the combined amount of the current vector and the voltage vector ≧ 0, and an absolute value of the voltage vector ≦
One of the fourth determination means for determining whether it is the sum of the absolute value of the combined amount of the impedance set value and the current vector and the voltage set value, the first determination means, or the second to fourth determination means. An undervoltage relay device for current compensation, comprising: an undervoltage detection unit that detects an undervoltage of a power system when a determination result is output.