JP2001112162A - Protective relay - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely discriminate a three-phase short circuit accident or a two- phase short circuit accident, eliminating the defects of a conventional method of detecting the short circuit accident of a heavy load power system from the current with reverse phase. SOLUTION: A filter 2 extracts the current I1 for a normal phase and the current I2 for a reverse phase from the data of currents Ia, Ib, and Ic detected from a heavy load system, and a comparator 4 compares the magnitudes of the current I1 for a normal phase and the current I2 for a reverse phase, and a discriminating unit discriminates the absolute value of the current I2 for a reverse phase to be not less than a certain value when the current I1 for a normal phase is approximately equal to or a slightly larger than the current I2 for a reverse phase. A discriminating unit 5 judges the absolute value of the current I1 for a normal phase to be not less than a certain value when the current I1 for a normal phase is sufficiently larger than the current I2 for a reverse phase. A relay detector 3 obtains a current relay operation output from the current Ia, Ib, and Ic. Logical parts 7, 8 and 9 obtains a trip output, when the discriminating unit can obtain discrimination output on condition that the relay detector was able to obtain the operation output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection relay device for realizing a short-circuit protection relay for a heavy-load power system or a short-circuit distance relay for a heavy-load long-distance power transmission system.

[0002]

2. Description of the Related Art In a heavy load power system having a large load current,
Even if a short-circuit accident occurs, the short-circuit current may not be distinguished from the load current due to the distance to the short-circuit point and the arc resistance at the short-circuit point, and the short-circuit accident cannot be detected only by the overcurrent relay.

In such a system, attention is paid to the fact that there is a large amount of current in the negative phase at the time of an accident, and this is extracted by a negative phase filter, and an overcurrent relay or a directional distance relay operating in the negative phase is employed. I have. In addition, when a three-phase short circuit occurs, the amount of the negative phase component may decrease and the relay may become inoperable. Therefore, the three-phase short circuit is separately detected to obtain a protection operation.

[0004]

SUMMARY OF THE INVENTION Operation of an anti-phase filter
Are the a, b, and c phase currents I that have the vector relationship of FIG._a,
I_b, I_cThus, for example, the negative phase component is the current I_cIs 120 ° positive
In the direction of _bCalculated by subtracting
Can be

[0005]

[Number 1] _{I b -I c ∠120 ° = I} 0 + a 2 I a1 + aI a2 + aI 0 -a 2 I a1 -a 2 I a2 = (1-a) I 0 + (a1) I a2 = (A-1) I _a2 (1) where I ₀ is a zero-phase current, and is set to ≒ 0 in the event of a short circuit. I _a1 is the normal phase component based on the a-phase, and I _a2 is the reverse phase component based on the a-phase.

The negative phase component current obtained from the above equation (1) is
Current I_a, I_b, I_cIs three-phase equilibrium, I_a2Is 0
Equation (1) becomes 0. Also, when the bc phase is short-circuited,
Is I _b-I_c∠120 ° ≠ 0, not reversed phase output
Is done.

Therefore, by performing overcurrent relay operation and directional relay operation from the negative phase component extracted by the negative phase filter, it is possible to prevent the relay from malfunctioning in a three-phase balanced load even in a heavy load system, and to prevent a short circuit accident. Can respond.

However, in the case of a three-phase short-circuit accident, the operation becomes equivalent to that of a three-phase balanced load, and the protection relay from the opposite phase should operate but cannot operate. That is, it becomes difficult to distinguish between a three-phase short circuit accident and a heavy load in a heavy load system. In addition,
Even with a three-phase short-circuit relay prepared separately, it is difficult to distinguish between a heavy load and an accident.

SUMMARY OF THE INVENTION It is an object of the present invention to obtain a protection operation that reliably discriminates between a three-phase short-circuit fault and a two-phase short-circuit fault such as a two-phase short-circuit fault, which behave the same as three-phase balance in a heavy load power system. It is to provide a protective relay device that can be used.

[0010]

According to the present invention, in order to solve the above-mentioned problems, an antiphase component and an antiphase component are extracted by an antiphase filter and an antiphase filter, and whether or not the antiphase component and the antiphase component are substantially equal. Alternatively, a two-phase short-circuit accident is determined on the condition that the positive-phase component is slightly larger than the negative-phase component and the absolute value of the negative-phase component is equal to or greater than a certain value,
A three-phase short-circuit accident is determined on the condition that the positive phase component is sufficiently larger than the negative phase component and the absolute value of the positive phase component is equal to or more than a certain value, and has the following configuration.

A protection relay for a heavy-load power system or a heavy-load long-distance power transmission system, comprising three-phase currents I _a , I _b , and I _c detected from the system and _a positive-phase current I ₁ and a negative-phase current I _1. a filter for extracting a current I _2, the positive-phase component current I ₁ and the reverse-phase component current I ₂
A comparing unit for comparing the magnitude, absolute value of the reverse-phase current I ₂ when the positive phase current I ₁ in the comparison result of the comparison unit is slightly greater than or approximately equal to the negative-sequence current I ₂ is equal to or greater than a predetermined value a first determination unit determines that it is the absolute value of the positive phase component current I ₁ if the positive phase current I ₁ in the comparison result of the comparison unit is sufficiently greater than the reverse-phase current I ₂ is constant a second determination unit determines that the value or more, the current I _a, I _b, and the relay detection unit for obtaining a current relay operation output from the I _c, that the operation output is obtained in the relay detection unit The condition includes a logic unit that obtains a trip output when a judgment output is obtained by the first or second judgment unit.

[0012]

FIG. 1 is a functional block diagram showing an embodiment of the present invention. In the figure, an input conversion circuit 1
, The current I _a of the power system, I _b, is converted to dig ital data by the A / D conversion and the like to I _c voltage as a reference phase. The filter 2 extracts a normal phase component and a negative phase component from each current (vector) data. The following current vector relationship is shown in FIG.

(1) The normal phase extraction calculation by the filter 2 is as follows on the basis of the a phase. Here, I _a1 is a positive phase component, I _a2 is a negative phase component, and I ₀ is a zero phase component.

[0014]

[Number 2] _{I a = I 0 + I a1} + I a2 ... (2a) I b = I 0 + a 2 I a1 + aI a2 ... (2b) I c = I 0 + aI a1 + a 2 I a2 ... (2c) zero from above to erase phase min I _0, performing the calculation of the line current.

[0015]

I _ab = I _a −I _b = (1-a ² ) I _a1 + (1-a) I _a2 (3a) I _bc = I _b −I _c = (a ² −a) (I _{a1 -I a2) ... (3b)} I ca = I c -I a = (a1) I a1 + (a 2 -1) I a2 ... (3c) Next, line-to-line current (delta current) and it Current I _ab ∠−60 ° = (− a) I _ab , I _bc ∠−60 °
= (− A) I _bc , I _ca ∠−60 ° = (− a) I _ca , and the positive phase component is determined such that the absolute value and the phase of each phase reference are the same.

[0016]

I _ab + I _ca ∠-60 ° = (1−a ² −a ² + a) I _a1 = (1 + a−2a ² ) I _a1 = −3a ² I _a1 (4a) I _bc + I _ab ∠− ^{60 ° = (1-2a + a 2} ) I a1 = -3aI a1 ... (4b) I ca + I bc ∠-60 ° = (a + a 2 -2) I a1 = -3I a1 ... (4c) (2) reverse phase Is obtained by the following calculation based on the phase a.

[0017]

I _ab + I _bc ∠-60 ° = (2-a−a ² ) I _a2 = 3I _a2 (5a) I _bc + I _ca ∠60 ° = (2a−a ² −1) I _a2 = 3aI _a2 ... (5b) I _ca + I _ab ∠-60 ° = (2a ² −a−1) I _a2 = 3a ² I _a2 ... (5c) By the above calculations, the filter 2 forms the three-phase current I _a , I _b, the I _c, the positive-phase component current I ₁ (4a, 4b, 4
c), the negative-sequence component current I ₂ is calculated as (5a, 5b, 5)
c) It is determined from the equation.

Next, the relay detecting section 3 detects the currents I _a , I _b ,
Performing conventional current relay computation and distance relay computation from the data of the I _c. The comparing unit 4 includes a positive-phase current I ₁ and a negative-phase current I ₂
And if I ₁ ≫I ₂ , it is determined that there is a three-phase equilibrium fault or a normal heavy load condition, and the determination unit 5 determines that the absolute value | I ₁ | of the positive-phase current is a constant value K ₁ Under the conditions described above, a judgment output of a three-phase equilibrium accident is obtained.

In the comparison of the comparison section 4, the positive-phase current I ₁
Is substantially equal to the negative phase component current I ₂ (I ₁ ≒ I ₂ ) or slightly larger (I ₁ > I ₂ ), it is determined that an unbalanced fault state such as a two-phase short-circuit fault has occurred. the absolute value of the reverse-phase current | I ₂ | get determination output of the two-phase short-circuit fault in the condition that a certain value K ₂ or more.

The AND condition units 7 and 8, which become logic units, obtain judgment outputs from the judgment units 5 and 6 on condition that the relay operation is obtained by the relay detection unit 3, and provide OR condition units which become logic units. Reference numeral 9 denotes one of the judgment outputs from the AND condition units 7 and 8 to obtain a trip output of a circuit breaker or the like.

As described above, in this embodiment, in a heavy load system in which the load current and the fault current cannot be distinguished by a normal relay, the negative phase component and the positive phase component are compared, and the negative phase component and the positive phase component are compared. It is determined that a two-phase short-circuit accident occurs when the two phases are almost equal or the positive-phase part is slightly larger than the negative-phase part, and is determined as a three-phase short-circuit accident when the positive-phase part is sufficiently larger than the negative-phase part. . By setting the comparison judgment and the absolute value judgment of the positive phase component and the negative phase component in the system condition, it is possible to distinguish between a reliable relay operation in a two-phase short circuit accident and a non-operation in a three-phase normal load, and
A reliable relay operation due to a phase short circuit accident can be obtained.

[0022]

As described above, according to the present invention, the negative phase component and the normal phase component are extracted by the filter, and the positive phase component and the negative phase component are almost equal or the positive phase component is slightly larger than the negative phase component. A two-phase short-circuit fault is determined on condition that the absolute value of the negative phase component is equal to or greater than a certain value, and the positive phase component is sufficiently larger than the negative phase component and the absolute value of the positive phase component is equal to or greater than a certain value. Is determined under the condition, a three-phase short-circuit fault in a heavy load power system and an unbalanced fault such as a two-phase short-circuit fault can be reliably determined to provide a protection operation.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing an embodiment of the present invention.

FIG. 2 is a relationship diagram of a current vector in the embodiment.

FIG. 3 is a diagram showing a vector relationship for an inverse phase.

[Description of Signs] 1 ... Input conversion unit 2 ... Filter 3 ... Relay detection unit 4 ... Comparison unit 5, 6 ... Determination unit 7,8 ... And condition unit 9 ... OR condition unit

Claims (1)

[Claims] 1. A protection relay device for a heavy-load power system or a heavy-load long-distance power transmission system, wherein the three-phase currents I _a , I _b , and I _c detected from the system are opposite to the positive-phase current I _1. a filter for extracting a phase frequency current I _2, the positive-phase component current I ₁ and a comparison unit for comparing the magnitude of the reverse-phase current I _2, the positive phase current I ₁ reverse phase comparison result of the comparison unit Current I ₂
When about equal to the first determination unit determines that the absolute value of the reverse-phase current I ₂ is equal to or greater than a predetermined value when somewhat larger, positive phase current I ₁ reverse phase comparison result of the comparison unit Current I ₂
Relay absolute value of the positive phase component current I ₁ if more fully large to obtain a second determination unit determines that at least a predetermined value, the current I _a, I _b, the current relay operation output from the I _c A detection unit, provided that an operation output is obtained in the relay detection unit;
And a logic unit for obtaining a trip output when the first or second determination unit obtains a determination output.