JPH09149540A - Circuit selective relay, circuit selection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the trouble circuit selecting function in a multicircuit parallel transmission line. SOLUTION: This circuit selective relay 20 improves the reliability of selection of fault circuit on itself by computing the distance x to the fault point F, judging transmission lines 1L and 2L as one loop, using each path current I1a and I2A on two circuits in parallel, self inductance being line constant, and further mutual inductance. Especially, in the function of selecting the fault circuit in three or more multicircuit parallel transmission lines, the reliability is raised by judging it synthetically from the operation result concerning plural loops.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection relay system for a transmission line of a power system, and more particularly to a line selection relay of a fault line in a parallel transmission line and a parallel relay for selecting a fault line in the parallel transmission line. The present invention relates to a circuit selection method in a power transmission line.

[0002]

2. Description of the Related Art Regarding a protection relay system for a power transmission line of a power system, as a conventional fault line selection means in a parallel transmission line, for example, a literature example "Protective relay system", Denki Shoin, February 25, 1974, As shown on pages 54 to 55, a power balancing method using the current signals of Lines 1 and 2 and the voltage signal of the electric power station is already known.
In this power balancing system, the magnitude of the fault current and the direction of the fault current are determined to attempt to selectively cut off the fault circuit.

[0003]

However, according to the above-mentioned conventional method, a method is used in which the line constants in the transmission line are uniformly distributed and the electromagnetic induction from other transmission line circuits is not considered. Has been. So in particular,
The number of lines in parallel becomes three or more, and there is a possibility that an error may occur or an erroneous determination may occur in the determination in the lines having different line impedances.

In view of the above, the present invention solves the above-mentioned problems in the prior art and improves the fault line selection performance even in a multi-line parallel transmission line, and is capable of ensuring the fault line of the parallel transmission line. An object is to provide a selection relay and a circuit selection method thereof.

[0005]

According to the present invention, there is provided a plurality of power transmission lines connected at both ends thereof so as to have the same electric potential at each power station for transmitting power between two power stations. A line selection method for detecting in which transmission line of a fault an accident has occurred, which is assumed to have occurred in a fault position at a distance x from one electric power station, and one of the other transmission lines. When a potential drop is sequentially calculated using the self-impedance and the mutual impedance and the detected current detected from the transmission line starting from the accident position along a loop composed of electric wires, and when the circuit further goes around the loop. The distance x is calculated so that the sum of the potential drops becomes 0, and when the accident position indicated by the calculated distance x is on the transmission line on the assumption that the accident has occurred, it is determined that an accident has occurred on the transmission line. Characteristic to judge Line selection method to disclose.

Further, according to the present invention, when the number of the transmission lines is three or more, another transmission line forming a loop in combination with the transmission line assuming the occurrence of the accident is sequentially designated one by one and the distance is set. x is sequentially calculated, and when the accident position indicated by the calculated average value of the distance x is on the power transmission line assuming the occurrence of the accident, it is determined that an accident has occurred on the power transmission line. Is disclosed.

Further, according to the present invention, when the number of the transmission lines is three or more, another transmission line forming a loop in combination with the transmission line assuming the occurrence of the accident is sequentially designated one by one and the distance is set. A circuit characterized by sequentially calculating x, and determining that an accident has occurred in the power transmission line when at least one of the calculated distances x indicates an accident position on the power transmission line assuming the occurrence of the accident. A selection method is disclosed.

Further, the present invention discloses a line selecting method, wherein the detected current is a zero-phase current of a transmission line.

Further, the present invention discloses a line selecting method, wherein the detected current is a current of each phase of a transmission line. The present invention also discloses a line selection relay using each of the above methods.

[0010]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 shows a power transmission line of a power system including a circuit selection relay which is an embodiment of the present invention. In this figure, first, the protection target transmission lines 1L and 2L which are the targets of protection by the circuit selection relay are shown, and further, reference numeral 1 in the figure
Reference numeral 0 represents a power source, reference numeral 11 represents a transformer, reference numeral 20 represents a relay for selecting a failure line from a plurality of transmission lines, and reference numeral 30 represents a load. Further, in the figure, the power transmission line 1L is a line 1 and the power transmission line 2L is a line 2. Further, the symbol x in the figure indicates an electric station A and an electric station B.
It shows the distance from the electric station A to the accident point when the total length of the section between and is 1.

Here, the above-mentioned Line 1 1L and Line 2 2L
Of the Z1: 1 line 1L, Z22: 2 line 2L of the self impedance, and Z12: 1 line 1L and the line 2L of the mutual impedance. These impedances are values per unit length.

In the figure, reference numeral CT1 is the above-mentioned 1
Reference numeral CT2 is a current transformer used for measuring the passing current of the line 1L, reference numeral CT2 is a current transformer used for measuring the passing current of the line 2L, and these outputs are conducted to the relay 20. Has been. Further, reference numeral 12 indicates the neutral grounding impedance ZN of the transformer.

In the circuit configuration of FIG. 1, each power transmission line represents a non-grounded zero-phase circuit. If there is no accident in the system, the current transformer C regardless of the presence of the load 30
Zero-phase currents I1A and I2 detected using T1 and CT2
A and the like are all 0. When an accident occurs, these zero-phase currents are not zero, so it is possible to know the occurrence of the accident by detecting that. In the case of a ground fault, it can also be detected because the zero-phase voltage becomes large. On the other hand, in the case of a short circuit between phases, the occurrence of an accident can be detected by a decrease in line voltage or a sudden change in current of each phase. Although not shown in the drawings, a conventionally known technique may be used.

When the occurrence of an accident is detected as described above, it is an object of the present invention to accurately specify which position on which line the accident occurred. Therefore, it is now assumed that an accident has occurred at the point F of the electric power line A in FIG. At this time, since the zero-phase component of the current flowing toward the load 30 is 0, the zero-phase current I2A of the power transmission line 2L directly passes through the electric power station B and flows into the power transmission line 1L. Zero-phase current I1 flowing from the power line to the transmission line 1L
Both A and A flow into the accident point F. Therefore, according to Kirchhoff's second law in the closed loop of the parallel transmission lines 1L and 2L between the electric power station A and the electric power station B, the following equation (Equation 1) is established.

(Equation 1) By organizing this and calculating the distance x to the accident point,

(Equation 2) Becomes

As is clear from the above (Equation 2), it is understood that x, which is the information for determining the accident point F, depends on the self impedances Z11 and Z22 of the transmission lines 1L and 2L and the mutual impedance Z12. . Then, in the line selection relay 20, the distance x is calculated from the above-mentioned (Formula 2) calculation formula in which the electromagnetic induction between the lines is taken into consideration, and the distance x is 0 to 0.
By determining whether or not it is between 1, it is possible to reliably select the faulty line and specify its position. Further, also for the power transmission line 2L, the presence or absence of the accident point and the position thereof can be specified from the same equation as (Equation 2) (Equation 2 in which the subscripts 1 and 2 are interchanged).

Further, as shown in FIG.
In the circuit, since the distribution of the fault current flowing through the transmission lines 1L and 2L is determined only by the line constants Z11, Z22 and Z12, the mutual induction with other circuits causes a fatal problem in the above measurement of x. Absent. However, when the number of lines is further increased in FIG. 1 described above, for example, when there are three lines as shown in FIG. Cannot be ignored.

The reference numerals in FIG. 2 are the same as those in FIG.
The same reference numerals indicate the same components, and in the example shown in this figure, the reference numeral 3L indicates the transmission line No. 3, and the current signals also have transmission line numbers such as I1A, I2A, and I3A. Is shown in. Of course, these current signals are zero-phase currents of each transmission line. In addition, in FIG. 2, the self-impedance of the power transmission lines 1L, 2L, and 3L is
Z11, Z22, Z33, the mutual impedance between the transmission lines 1L and 2L is Z12, the mutual impedance between the transmission lines 2L and 3L is Z23, and the transmission line 1 respectively.
Let Z13 be the mutual impedance between L and 3L.

Therefore, in FIG. 2, it is assumed that an accident has now been detected in the same manner as in the case of FIG. Therefore, it is assumed that an accident occurs at a point F of the transmission line 1L at a distance x from the electric station A. At this time, the zero-phase currents I2A and I3A of the power transmission lines 2L and 3L all flow into the power transmission line 1L, and these and the zero-phase current I1A of the power transmission line 1L all flow into the fault point F. Therefore, the section from the electric power station A to the electric power station B is set to 1, and the distance x from the electric power station A to the accident point F is calculated by the transmission line 1L.
Calculated from Kirchhoff's second law in a closed loop of 2 and 2L, this is expressed by the following (Equation 3).

(Equation 3) Similarly, from the closed loop of the transmission lines 1L and 3L, similarly, x
When is calculated, it is shown by the following (Equation 4).

(Equation 4) Since both (Equation 3) and (Equation 4) depend on the passing current of each power transmission line and each line constant, the above (Equation 3) is applied to the line selection relay 20 in the multi-line parallel power transmission line. Alternatively, as in (Equation 4), whether or not the distance x obtained from the arithmetic expression considering the electromagnetic induction between the lines is between 0 and 1 is surely selected and the fault line is reliably selected. The position can be specified. Transmission line 2L, 3L
The same applies to.

Further, it is possible to obtain the above-mentioned value of x by either of the above (Equation 3) or (Equation 4), but whether the value of x is calculated and averaged by both equations. , Or by selecting whether or not x is in the range of 0 to 1 by comprehensively judging based on the calculation results of a plurality of formulas and selecting the faulty line. It is possible to realize a more reliable line selection relay.

Furthermore, even if the number of parallel lines is four or more, more formulas for x can be obtained by the same idea as in (Equation 3) and (Equation 4). All or a combination with a line having a relatively large passing current may be used to determine the line selection.

FIG. 3 shows an outline of a calculation flow when the circuit selection relay 20 according to the present invention is constructed by using, for example, a digital computer. The symbols used therein are as described above. 1 and 2 and the same thing as in the above (Equation 1) to (Equation 4) performs the same operation as the contents already explained above.

That is, in the flow chart of FIG. 3, first, the set value (Z1
1, Z22, Z33, Z12, Z13, Z23 and the like. However, the value per unit length is stored (step S5).
1). At this time, these data may be stored in a memory or the like which constitutes a digital computer. Next, the current transformers CT1 and CT2 for detecting the zero-phase current of each line
The current signal data (I1A, I2A, I3A) from the same is input (step S52). It should be noted that this input is automatically performed via an input / output circuit portion that constitutes a digital computer, for example. Therefore, the digital computer, for example, in its central processing unit, calculates the position x of the accident point in an arbitrary closed loop (step S53). In this case, for example, in the line shown in FIG. 1 above, the closed loop is uniquely determined by the power transmission lines 1L and 2L, while, for example, in the line shown in FIG.
Combination of L and 2L (1L / 2L), transmission lines 1L and 3L
Combination (1L / 3L), and transmission lines 2L and 3L
The combination with (1L / 2L) is possible.

This selection method is simplified in FIG. 3, but it will be described in detail as follows. That is, when there is an accident in the power transmission line L1 and the position of the accident point is x1, x1 is obtained from (Equation 3) (Equation 4) from two combinations of the power transmission lines 1L and 2L and the transmission lines 1L and 3L. . Similarly, there is an accident on the transmission line 2L, and the position of the accident point is x2.
, Then transmission lines 2L and 1L and transmission lines 2L and 3L
When x2 is calculated from the two combinations of (3) and (4) using the same formulas, and there is a fault in the power transmission line 3L, and the position of the fault point is x3, the power transmission lines 3L and 1L And two combinations of power transmission lines 3L and 2L (Equation 3) (Equation 4)
X3 is calculated by using the same formula as. And these x1,
It is checked whether x2 and x3 are between 0 and 1 (step S54). If the accident point is on the transmission line L1,

Since 0 <x1 <1 and x2 and x3 are not between 0 and 1, it is determined that the accident point is at the position x1 on the power transmission line L1 when this condition is satisfied, and ( When the expression 5) is satisfied only by x2, the accident point is at the position x2 on the power transmission line L2, and x
When it is satisfied only by 3, it is determined that there is an accident point at the position x3 on the power transmission line L3, and a cutoff command is issued to the power transmission line (step S55).

In the description of this embodiment, the so-called computer (computer) is used to identify the fault circuit, but the present invention is not limited to this embodiment. For example, the above processing can be performed by a dedicated logic circuit.

Further, in the above description, the current detected from each power transmission line is a zero-phase current, but in the case of a short circuit fault, the fault current is much larger than the load current. Therefore, at this time, the circuit of one phase of the three-phase AC, for example, the A phase, and the respective currents are also the A phase currents in this case, so that the short circuit accident can be detected approximately by the above method. it can. Therefore, if similar detection is performed for all the phases, system fault detection can be reliably performed.

[0026]

As is clear from the above detailed description, according to the line selection relay and the line selection method for a fault line in a parallel transmission line according to the present invention, two or more line parallel lines, particularly three or more lines are used. It is possible to improve the selection performance of the fault circuit in the multi-circuit parallel line of, and to make it accurate and reliable. Also, since multiple selection information can be obtained, its reliability is improved. Since the determination method focuses on the current, it does not use a voltage signal and is economically advantageous, and exhibits various technically excellent effects.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an entire transmission line of a power system using a line selection relay according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining an operation of a line selection relay in a three-line parallel line according to another embodiment of the present invention.

FIG. 3 is a flow chart showing an example of processing of a line selection method of a faulty line in a parallel transmission line by the line selection relay of the present invention.

[Explanation of symbols]

 1L, 2L, 3L Transmission line CT1, CT2 Current transformer 10 Power supply 11 Transformer 20 Line selection relay 30 Load

Claims (11)

[Claims] 1. An accident occurring in any of a plurality of power transmission lines connected to each other so that both ends thereof have the same potential for transmitting power between two power stations is detected. And a current detecting means for detecting a current of each of the power transmission lines in one electric station, and a self-impedance of each of the power transmission lines and a mutual impedance between the power transmission lines. A line selection relay, comprising: a fault line detection unit for detecting a transmission line in which an accident has occurred, based on the detected current detected by the current detection unit. 2. The fault line detection means is configured to follow a loop composed of a transmission line on the assumption that an accident has occurred at a fault position at a distance x from one electric station and another arbitrary transmission line, Starting from the accident position, the potential drop is sequentially calculated using the self-impedance and the mutual impedance and the detected current, and further, the distance x such that the sum of the potential drops when the circuit makes one round is 0. And a determining means for determining whether or not the accident position indicated by the distance x calculated by the calculating means is on a transmission line on the assumption that the accident has occurred. The line selection relay according to claim 1, which is characterized in that. 3. The line selection relay according to claim 2, wherein when the number of the transmission lines is three or more, the fault line detection means loops in combination with the transmission line assuming the occurrence of the fault. Computation control means for sequentially designating the other power transmission lines constituting each one by one and sequentially calculating the distance x from the electric station to the accident position by the computing means, and the distance x sequentially calculated by the computing means. An average value calculating means for obtaining an average value, and a determining means for determining whether or not the accident position indicated by the average value calculated by the means is on the transmission line assuming the occurrence of the accident. A line selection relay characterized by the following. 4. The line selection relay according to claim 2, wherein when the power transmission line has three or more lines, the fault line detection means combines with the power transmission line on the assumption that the fault has occurred to form a loop. Computation control means for sequentially designating the other power transmission lines constituting each one by one and sequentially calculating the distance x from the electric station to the accident position by the computing means, and the distance x sequentially calculated by the computing means. A circuit selection relay, comprising: a determination unit for determining whether or not at least one of the above-mentioned accident positions is on a transmission line on the assumption that the accident has occurred. 5. The line selection relay according to any one of claims 1 to 4, wherein the current detecting means is a means for detecting a zero-phase current of a transmission line. Selective relay. 6. The line selection relay according to claim 1, wherein the current detecting means is a means for detecting a current of each phase of the transmission line. Line selection relay. 7. A fault occurs in any of a plurality of transmission lines connected to each other so that both ends thereof have the same potential for transmitting power between two electric stations. A line selection method for detecting whether or not a power transmission line is assumed to have occurred at a fault position at a distance x from one electric power station, and a line composed of another arbitrary power transmission line. Then, starting from the accident position, the potential drop is sequentially calculated using the self-impedance and the mutual impedance and the detected current detected from the transmission line,
Further, the sum of the potential drops when the loop goes around once is 0.
A circuit characterized by calculating the distance x such that the accident position is on the power transmission line on the assumption that the accident has occurred, and determining that an accident has occurred on the power transmission line. Selection method. 8. The line selecting method according to claim 7,
When the number of the transmission lines is three or more, the other transmission lines forming a loop in combination with the transmission line assuming the occurrence of the accident are sequentially designated one by one, and the distance x is sequentially calculated, and the calculation is performed. When the accident position indicated by the average value of the distance x is on the transmission line on the assumption that the accident has occurred, it is determined that an accident has occurred on the transmission line. 9. The line selection method according to claim 7, wherein:
When the number of the transmission lines is three or more, the other transmission lines forming a loop in combination with the transmission line assuming the occurrence of the accident are sequentially designated one by one, and the distance x is sequentially calculated, and the calculation is performed. A method of selecting a line, characterized in that, when at least one of the accident positions indicated by the above-mentioned distance x is on a transmission line on which the accident is assumed to occur, it is determined that an accident has occurred on the transmission line. 10. The line selection method according to claim 7, wherein the detected current is a zero-phase current of a transmission line. 11. The line selection method according to claim 7, wherein the detected current is a current of each phase of the transmission line.