JPH0116089B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ground fault protection relay device, and in particular, to a ground fault protection relay device suitable for ground fault protection when a zero-sequence circulating current occurs in a multicircuit parallel transmission line of a resistance grounding system. Regarding relay devices.

In general, important power transmission lines are often configured as multi-circuit power transmission lines with two or more circuits as shown in FIG. 1 in order to improve the reliability of power supply.

In Figure 1, a multi-circuit power transmission line with resistance grounding system
L ₁ to _{L 4} are power supply system 1 bus bar 10 disconnectors.
They are connected via SB ₁₁ to SB ₁₄ , respectively, and the sheath breakers SB 21 to SB ₂₁ are connected to the bus 20 of load system 2.
They are connected to each other via SB ₂₄ . The power supply system 1 is constructed by connecting a bus bar 10 to a power source 12 such as a generator via a transformer 11, and grounding the neutral point of the transformer 11 via a resistor 13. In addition, the load system 2 includes a bus bar 20
is connected to a load 22 via a transformer 21.

In a multi-circuit power transmission line system configured in this way, resistance-grounded multi-circuit transmission lines L ₁ to _{L 4} are often installed together on a single tower, and zero-sequence circulating current due to mutual induction between the lines is known to occur.

FIG. 2 shows an example of a four-circuit parallel power transmission line. In this figure, when load currents I〓 _L1 , I〓 _L2 , I〓 _L3 , I〓 _L4 flow through each line L ₁ to _{L 4} , zero-phase circulating currents I〓 _CO1 , I〓 _CO2 , I〓 _CO3 , I〓 _CO4 is generated. Under such conditions, if a one-line ground fault occurs in any one of the transmission lines L ₁ to _{L 4} , in a resistance-grounded transmission line, the fault current will flow through the neutral point of the transformer 11 . Since it is limited by the grounding resistance 13 and is small, the zero-sequence circulating current I〓 _CO1 ~ I〓 _CO4 explained in Fig. 2
It is difficult to distinguish between internal and external faults, and in many cases it is not possible to determine whether the fault is internal or external using a simple ground fault directional relay.
FIG. 3 shows an example of a parallel transmission line with four circuits in parallel, similar to that shown in FIG. That is, when a ground fault occurs, the zero-sequence currents I〓 ₀₁ to I〓 ₀₄ of each line L ₁ to L ₄ on the bus 10 side in Fig. 3
is the sum of the fault current (current flowing through the neutral point grounding resistor 13) I〓 _F1 ~ I〓 _F4 and the zero-phase circulating current I〓 _CO1 ~ I〓 _CO4 , and I〓 _O1 = I〓 _F1 + I〓 _CO1 …(1) I〓 _O2 ＝I〓 _F2 +I〓 _CO2 …(2) I〓 _O3 ＝I〓 _F3 +I〓 _CO3 …(3) I〓 _O4 ＝I〓 _F4 +I〓 _CO4 …(4) The original ground fault fault judgment is based on the zero-sequence voltage V = ₀ ,
This is done by identifying the magnitude and phase of the fault current I〓 _F1 ~ I〓 _F4 , but as already mentioned, compared to the fault current, the zero-sequence circulating current I〓 _CO1 ~ I〓 _CO4 is ignored. If this is not possible, it will be affected by these currents I〓 _CO1 ~ I〓 _CO4 , and the magnitude and phase of the currents I〓 _F1 ~ I〓 _F4 will change, making it impossible to make a regular accident judgment. There were some things that I couldn't do. Various countermeasures against such phenomena have been proposed in the past. For example, by focusing on the change in zero-sequence current before and after the occurrence of an accident, only the fault current I〓 _F1 ~ I〓 _F4 can be extracted without being affected by the zero-sequence circulating current I〓 _CO1 ~ I〓 _CO4 , and an accident can be determined. A method has been proposed. This method will be described below. In this method, the zero-sequence current I〓 _O1 ~ I〓 _O4 of each line L ₁ to _{L 4} before the occurrence of an accident is only the zero-sequence circulating current I〓 _CO1 ~ I〓 _CO4 , I〓′ _O1 ＝I〓 _CO1 …(5) I〓′ _O2 ＝I〓 _CO2 …(6) I〓′ _O3 ＝I〓 _CO3 …(7) I〓′ _O4 ＝I〓 _CO4 …(8) Given On the other hand, after the accident occurs, it is given by equations (1) to (4) as mentioned above.
The values I〓′ _O1 ~ I〓′ _O4 before the occurrence of the accident are stored for a certain period of time, and these values I〓′ _O1 ~ I〓′ _O4 and the values after the accident occurrence given by equations (1) to (4) are The difference between _I〓O1 to _I〓O4 , that is, the change before and after the occurrence of the accident, is extracted for each line as shown in the formula below, and an accident is determined. In other words, the change ΔI〓 _O1 ~ ΔI〓 _O4 is ΔI〓 _O1 ≡I〓 _O1 −I〓′ _O1 = I〓 _F1 +I〓 _CO1 −I〓 _CO1 = I
〓 _F1 ……(9) ΔI〓 _O2 ≡I〓 _O2 −I〓′ _O2 ＝I〓 _F2 ＋I〓 _CO2 −I〓 _CO2 ＝I〓 _F2 ……(10) ΔI〓 _O3 ≡I〓 ₀₃ −I〓′ _O3 ＝I〓 _F3 ＋I〓 _CO3 −I〓 _CO3 ＝I〓 _F3 ……(11) ΔI〓 _O4 ≡I〓 _O4 −I〓 _O4 ＝I〓 _F4 ＋I〓 _CO4 −I〓 _CO4 ＝I〓 _F4 ……( 12) is given as follows. A specific example of a device that performs such calculations is shown in FIG. That is, FIG. 4 is a block diagram showing a conventional example of a ground fault protection device.

In FIG. 4, the earth fault protection relay device is provided for each resistance-grounded multi-circuit transmission line in which zero-sequence current occurs, and takes in the zero-sequence voltage V ₀ in each transmission line from the input terminal 30, and Calculating means 41 to 44 that take in phase currents I〓 _O1 to I〓 _O4 from input terminals 31 to 34 and calculate the effective zero-sequence current of each line based on these taken-in signals, and these calculating means 4
The comparison circuit 5 serves as a comparison means for determining an accident based on the effective zero-phase currents from 1 to 44. Since the calculation means 41 to 44 have the same configuration, these calculation means 4
To explain one of 1 to 44, calculation means 4
1 is a memory circuit 6 for the zero-sequence current input to the input terminal 31, and a comparison difference calculation between the output of the memory circuit 6 and the value of the zero-sequence current input to the input terminal 31 using the formula shown in equation (9). and an effective component calculation circuit 81 which receives the zero-sequence voltage V ₀ taken in from the input terminal 30 and calculates the effective component zero-sequence current using the value from the comparison circuit 71. In addition,
Other calculation means 42 to 44 are memory devices 62 to 64.
, comparison circuits 72 to 74, and effective component calculation circuit 82.
~84, respectively.

The operation of the earth fault protection relay device configured as described above will be explained.

Zero-sequence current I of each line L ₁ to L _{4 O1} to _I
1 to 34, and store the vector amount of the zero-sequence current in each of the storage circuits 61 to 64 for a certain period of time, and then by each of the comparison circuits 71 to 74,
The instantaneous value of the input zero-sequence current and the memory circuit 61~
64 to perform a comparison difference calculation with the stored zero-sequence current value, extract the fault currents I〓 _F1 ~ I〓 _F4 from formulas (9) to (12), and further extract each of the thus extracted values. Line L ₁
~L ₄ fault current I〓 _F1 ~I〓 _F4 and zero-phase voltage input terminal 3
From the zero-sequence voltage V ₀ introduced from zero-sequence voltage V 0 , the effective component zero-sequence current of each line (the zero-sequence current of the in-phase component with V ₀ ) of each line is calculated by the effective component calculation circuits 81 to 84 , and the result is sent to the comparison circuit 5 The line with the largest effective zero-sequence current is determined to be the fault circuit, and an output corresponding to the result is sent to output terminals 91 to 91 for each line.
94.

FIG. 7 is a diagram showing an example of the comparator circuit 5, where 51 compares the magnitude of two values among the outputs of the effective component comparator circuits 81 to 84 and determines the value applied to the positive terminal. Outputs only when the value is greater than the value applied to the negative terminal. Further, 52 is an AND circuit, which outputs when all its inputs have an output. Furthermore, 51a to 51c, 51d to 51f, 51g to
51i, 51j to 51l are each set as one set, and 51a to 51c apply the output of 81 to the positive terminal, and the inputs from the other 82 to 84 to the negative terminal. Therefore, when the AND circuit 52a outputs, it means that the output of the valid component comparison circuit 81 is at the maximum. This relationship is 51d to 51f and 52
b, 51g to 51i and 52c, 51j to 51l and 52d are the same, and when 52b outputs, the output of 82 is the maximum, and when 52c outputs, 83
This means that the output of 84 is the maximum, and when 52d outputs, the output of 84 is the maximum.

However, in a system such as this protective relay device, which is based on detecting changes and determining an accident, there are the following drawbacks. In other words, in a parallel multi-circuit power transmission line as shown in Fig. 2, assuming a single-wire ground fault on the bus 20 side, on the bus 10 side, the fault current extracted from equations (9) to (12) Since I〓 _F1 to I〓 _F4 flow in parallel and there is no difference between each line, there was a drawback that it was difficult to determine the faulty line. Furthermore, even after properly determining the fault on the bus 20 side and disconnecting the breaker SB ₂₁ at the _{20 L1} end, the current distribution remains as shown in Figure 5. In this case, only the fault current I〓 _F1 flows, but the zero-sequence circulating current I〓 _CO2 ~I〓 _CO4 flows in the healthy line, and in the worst case, it is assumed that for example, I〓 _F1 I〓 _CO2 ... (13) Even considering the changing current,
Even after leading or breaking at the 20 _L1 end on the bus bar 20 side, 10 _L1
The drawback was that it was difficult to identify the faulty line at the end.

To explain this in more detail by taking the accident example shown in Figure 3 as an example, Figure 9 shows the current distribution of each line at the terminal 20 on the side where the near-end accident occurred (hereinafter referred to as the other end). FIG. 8 shows the current distribution of each line at the terminal 10 on the opposite side (hereinafter referred to as its own end). Figures 8 and 9 a show the state before the accident occurred, Figures 8 and 9 b show the state at the time of the accident at the other end, and the state after the other end accident was removed. This is shown in FIGS. 8 and 9c.

In other words, during normal operation, zero-phase circulating currents I _CO1 to I _CO4 flow as shown in Figure 2, for example, and this flows through the second line L ₂ to fourth line L ₄ as shown in Figure 8 a at its own end.
In this case, I _CO2 to I _CO4 flow out, and this composite value flows into the first line _L1 as I _CO1 . At the other end, as shown in Figure 8b, I _CO1 flows out from the first line _L1 , and I _CO1 is equally divided from the second line _L2 to the fourth line _L4 and flows in as I _CO2 to I _CO4 . are doing. In the case of the present invention, a load current also flows, but the protective relay device is not affected by the load current, so it is not shown in FIGS. 8 and 9.

Next, when a one-line ground fault occurs in the first line near the other end, the zero-sequence circulating currents I _CO1 to I _CO4 and the fault current flow as shown in FIG. As is clear from FIGS. 8 and 9b, the zero-sequence circulating current at the time of the accident is in the same direction and magnitude as before the accident. On the other hand, regarding the fault current, since the other terminal is the load end, the fault current flows only from the own end.
Since the distances from each line to the fault point are approximately equal, approximately the same amount of fault currents I _F1 to I _F4 flows into each terminal. Of these, I _F1 flows out from the accident point, and I _F2 to I _F4 flow out from the other end, and then
It is combined and flows to the accident point. Comparing this figure, the magnitude and direction of the zero-sequence circulating current are the same before and after the accident, so the protective relay device shown in Figure 4, which responds to time changes, outputs only the fault current from the comparison circuits 71 to 74. Derive. Since the protective relay device shown in Fig. 4 determines that a fault has occurred in the line corresponding to the comparison circuits 71 to 74 with the largest output, the other end can easily determine that the fault has occurred in the first line. The other end of the first line can open the disconnector. However, it is not possible to identify the fault line because the fault currents at each end are almost the same size, and conversely, if the fault line is identified based on a slight difference in current, it is extremely unreliable as a protective relay device. In order to avoid this, it is necessary to make a judgment with a sufficiently large difference.

As a result, only the other end of the first line was disconnected.
The zero-phase circulating current flowing through the lines from the line to the fourth line is redistributed to the three lines from the second line to the fourth line, as shown in c of the figure. For example, it flows out from the third and fourth lines at the own end and flows into the second line, and at the other end, it flows out from the second line and flows into the third and fourth lines, but when it comes to the third and fourth lines, The current flowing through the healthy line when the line is broken is larger than the current value when there are 4 lines. In this case, a transient fluctuation occurs in the detected current in the second line, but since this is due to the removal of the opposite end of the first line, the second line is interlocked so as not to be removed. Next, it is known that the fault current continues to flow into the first circuit at its own end, and its magnitude is larger than the fault current at the time of the fault. In this case, the difference between the zero-phase circulating current flowing in the second line and the fault current flowing in the first line becomes small, and the comparator circuit 5 of the protective relay device cannot distinguish the magnitude. and,
As a result, it is not possible to remove the fault at the first line's own end.

The purpose of the present invention was to solve the above-mentioned drawbacks of the prior art.Even when a zero-sequence circulating current occurs in a grounded balanced multicircuit overhead power transmission line, it is not affected by the zero-sequence circulating current and is accurate. The purpose of the present invention is to provide a ground fault protection relay device that is capable of determining faults.

The present invention provides an earth fault protection relay device that takes in the zero-sequence voltage of a multi-line power transmission line and the zero-sequence current of each line, calculates an effective zero-sequence current, and determines a faulty line based on the calculation result. The ground fault fault determination is controlled based on line load current (each phase current) conditions, and fault determination is performed without the influence of zero-sequence circulating current.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 6 is a block diagram showing an embodiment of the earth fault protection relay device according to the present invention. In the embodiment shown in this figure, the same components as in FIG. 4 are given the same reference numerals, and their explanations will be omitted.

The difference between the embodiment shown in FIG. 6 and the embodiment shown in FIG. 4 is that the load currents I〓 L1 to I〓 _L4 of each line L ₁ to _{L 4} are taken in through input terminals 101 to 102, respectively.
The presence or absence of load current is determined, and the calculation line (one of 41 to 44) in the line (one of L ₁ to _{L 4 )} determined to have no load current among load current I〓 _L1 to I〓 L4 Level determination means 201 to 204 that control the computation of (1) and also control the comparator circuit 5 to exclude from the comparison target the effective zero-phase current from the computation circuit other than the computation circuit determined to have no current.
is provided for each line _L1 to _L4 . That is,
As shown in Fig. 5, the present invention is difficult to identify based on the zero-sequence current, but in a healthy line, the load current is almost the same as before the fault, regardless of the one-wire ground fault in the system. _L2 ~ I〓 Points that flow continuously like _L4 ,
In the fault lines (L ₁ to _{L 4} ), the 20 _L1 terminals normally determine an internal fault and are cut off in advance, so the load current becomes "0" and does not flow.
Focusing on the difference in load current between faulty lines and healthy lines,
This system is designed to properly determine whether an internal ground fault is caused by a lead-in or a break at the other end. In other words, since a zero-phase circulating current is flowing in a line with a load current, in order to prevent false judgments, the ground fault relay is prevented from operating, and a line with no load current is disconnected as soon as the other party is ahead. Therefore, it is determined that the inflowing zero-sequence current is only a fault current, and a regular internal one-wire ground fault fault determination is performed.

Next, the operation of the embodiment of the present invention will be explained.

In addition to the ground fault determination circuit shown in Figure 4, the load current (a single-phase circuit is shown in Figure 6, but in reality, it is a three-phase circuit to determine three-phase load current conditions). Input the conditions to the input terminal 101 for each line.
Introduced from ~104, level determination circuits 201-2
Judgment is based on 04.

Here, if one of the level determination circuits 201 to 204 determines that there is no load current, the vector storage circuits 61 to 64, which have already been explained with reference to FIG.
The amount stored in the circuit whose load current is determined to be zero is forcibly set to "0," and the amount stored in the circuit whose load current is determined to be zero among the load current level determination circuits 201 to 204 is forcibly set to "0." The output is introduced into the comparator circuit 5 and controlled so as to prevent a line with a load current from being judged. FIG. 10 shows the circuit configuration of the comparison circuit 5 of the present invention, in which a forced zero circuit 53 and a NAND gate 54 are added. Of these, the forced zero circuit 53a is provided for the first line maximum detection circuit consisting of the comparison circuits 51a to 51c and the AND gate 52a, and is connected to the output of the level judgment circuit 201 for detecting zero load current of the first line. When calculating the effective minutes of other lines, line 8
The outputs of 2, 83, and 84 are set to zero. Similarly, 53b is provided for the second line maximum detection circuit consisting of 51d to 51f and 52b, and when the output of the level determination circuit 202 of the second line is received,
1, 83, and 84 output to zero, 53c is 51g
It is provided for the third line maximum detection circuit consisting of ~51i and AND gate 52c, and when the output of the level judgment circuit 203 of the third line is received, 82,8
4 and 81 are set to zero, and 53d is set to 51j to 51.
It is provided for the fourth line maximum detection circuit consisting of 1 and 52d, and makes the outputs of 82, 83, and 81 zero when the output of the level determination circuit 204 of the fourth line is received. Further, in this circuit, the NAND gate 54 provides an output when there is an output from the maximum detection circuit of its own line (output of the AND gate 52) and there is no output from the maximum detection circuit of another line.

To explain the operation of the circuits of FIGS. 6 and 10 constructed in this way, first the normal state (FIGS. 8 and 9)
When the state changes from a) in the figure to the accident occurrence state (b in Figures 8 and 9), the level judgment circuits 201 to 204 do not provide any output because load current is flowing through all lines. The circuit breaker at the opposite end of the first line is opened by the same function as the conventional device explained in FIGS. 4 and 7.

Next, considering the transition from the accident occurrence state (b in Figures 8 and 9) to the open state at the other end of the first line (c in Figures 8 and 9), the level judgment in Figure 6 The circuit 201 detects zero load current and sets the value stored in the memory circuit 61 to zero. In other words, the value stored in the memory circuit 61 is the sum of I _F1 and I _CO1 in FIG. 8b, and the other input of the comparator circuit 71 is I _F1 in FIG. In order to set it to zero, I _F1 of FIG. 8c is derived in 71. Here, in order to set the memory value to zero in the fault line, the current change in the first line during this period is small, so it is devised to make it appear as if a large current change has occurred. This makes it easier to derive the current. Note that in a healthy line, the process of forcibly setting the stored value to zero is not performed, and the comparator circuit outputs a value corresponding to each current change. Effective component calculation circuits 81 to 84 are calculated from this current change and zero-sequence voltage.
The effective current obtained in is introduced into the comparison circuit 5, but the first line maximum detection circuit
1c and AND gate 52a), forced zero circuit 53
Since the signal is applied to a, the comparison circuits 51a~
The currents of other lines applied to the negative input terminal of 51c are forced to zero. Therefore, an output indicating the first line fault is output from the AND gate 52a.
On the other hand, no signal is applied to the forced zero circuits 53b to 53d of the other lines, and therefore, the maximum detection circuits of these lines do not match the individual judgment results according to the magnitude comparison of the input effective currents. gate 52b
52d, but regardless of this judgment result, the output of the level judgment circuit 201 is applied to the NAND gates 54b to 54d, making the output invalid. In this way, a command is finally given to the first line to trip the disconnector.

In this way, by performing the determination control based on the load current condition according to the present invention, it is possible to determine an internal one-wire ground fault that is not influenced by the zero-sequence circulating current. Furthermore, as shown in Figure 2, since the load current normally flows in parallel to each line, I〓 _L1 = I〓 _L2 = I〓 _L3 = I〓 _L4 ≡I〓 _L ...... (17 ), and since the zero-sequence circulating current has the following proportional relationship, I〓 _CO1 = α ₁ I〓 _L ... (18) I〓 _CO2 = α ₂ I〓 _L ... (19) I 〓 _CO3 = α ₃ I〓 _L ... (20) I〓 _CO4 = α ₄ I〓 _L ... (21) (However, α ₁ , α ₂ , α ₃ , α ₄ constants [complex numbers]). Therefore, I〓 _L is small and the fault current I〓 _CO1 ~I〓 _C
O4
It is conceivable that the fault current I〓 _F1 to I〓 _F4 is proportionally small and can be ignored in terms of accident judgment.Even in such cases, the present invention can be applied and the level judgment shown in Fig. 6 can be carried out. By selecting the levels of the circuits 201 to 204, it is possible to forcibly set the storage amount of the Bekult storage circuit to "0", detect a change, and make a determination.

As described above, according to the present invention, the load current is taken in, the presence or absence of the load current is determined, and the calculation of the effective zero-sequence current of the line for which it is determined that there is no load current is controlled. Since the effective zero-sequence current of the line can be controlled to be excluded from the fault determination conditions, there is an advantage that fault determination can be made accurately without being influenced by the zero-sequence circulating current.

[Brief explanation of drawings]

Figure 1 is a system diagram showing the system configuration of multi-circuit transmission lines, Figure 2 is an explanatory diagram showing the distribution of zero-sequence circulating current and load current in the system shown in Figure 1, and Figure 3 is an illustration of the internal distribution of the same transmission line. An explanatory diagram showing the current distribution in the event of a single-line ground fault; Figure 4 is a block diagram showing a ground fault protection relay device that takes measures against zero-sequence circulating current;
Fig. 5 is an explanatory diagram showing the current distribution when one end is ahead or disconnected, Fig. 6 is a block diagram showing an embodiment of the earth fault protection relay device according to the present invention, and Fig. 7 is a conventional comparison circuit. Figure 8 is a diagram explaining the current changes in each line at the own end before and after the occurrence of an accident, Figure 9 is a diagram explaining the changes in current in each line at the other end before and after the occurrence of an accident, and Figure 10 The figure is a circuit configuration diagram of the comparison circuit 5 of the present invention. 41-44... Arithmetic circuit, 5... Comparison circuit, 61-
64...Memory circuit, 71-74...Comparison circuit, 81-
84...Validity calculation line, 201-202...Level determination circuit.

Claims (1)

[Scope of Claims] 1. In a ground fault protection relay system for detecting a ground fault in a multi-circuit parallel transmission line, a plurality of a zero-sequence current detector, a plurality of storage circuits that store the outputs of each zero-sequence current detector for a predetermined period of time, a plurality of difference calculation circuits that calculate the difference between the input and output of the storage circuits, and a zero-sequence of the multi-circuit parallel power transmission line. a zero-phase voltage detector that detects voltage; a plurality of effective component calculation circuits that compare the output of the zero-phase voltage detector and the output of the difference calculation circuit to derive a difference calculation circuit output component that is in phase with the zero-phase voltage; a comparison circuit that compares the outputs of the effective component arithmetic circuits and determines that a ground fault has occurred in the line corresponding to the effective component arithmetic circuit that gives the largest output, provided for each line of the multi-circuit parallel transmission line; When the load current detector output detects zero load current, the zero-phase current detector output of this line is directly input to the effective component calculation circuit as the difference calculation circuit output. a level determination circuit that prevents the output of the effective component calculation circuit other than this line from being applied to the comparison circuit and becomes a target for ground fault determination when the load current detector output detects zero load current; A ground fault protection relay system characterized by comprising means for: