JPS61221518A - Ground fault detector for parallel two-channel system - 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] [Technical Field of the Invention] The present invention relates to a protective relay device for protecting a parallel two-wheel system, and in particular to a ground fault detection system that digitally detects a ground fault fault using a computer or the like. It is related to the device.

(Technical background of the invention) FIG. 6 shows an example of a conventional ground fault detection system.

In the figure, P is a power supply, and the power supply is connected to each circuit breaker CB11°CB21 on the power transmission side from the bus BUS1, and the power transmission line L1.
．． L2, load side breaker CBI 2. It is connected to bus line BLIS2 via CB22. 8th send N1! L1. L
A zero-phase current transformer ZCT11. A ZCT 21 is provided, and ground fault direction detection relays 67G11 and 67G21 are connected to the secondary side thereof, respectively. On the other hand, the above bus line BUS
The grounding transformer GTR is connected to l, and the open delta connected secondary winding is connected to each of the above-mentioned fault direction detection relays 67G11.
．． 67G21 respectively, and the voltage signal VO is output in the event of a ground fault.
supply. Further, a current limiting resistor CLR is connected to the secondary winding of the grounding transformer GTR, which sets the value of the ground fault current 0 in the event of a ground fault in the power system. Similarly, each power transmission line L1. There is also a zero-phase current transformer ZCT12 on the load side of L2,
ZCT22, ground fault direction detection relay 67G12.67G2
2 are provided and connected to each other, and the zero-phase voltage v0 is supplied to the ground fault direction detection relays 67G12 and 67G22 from the zero-phase transformer GPT. Also, arrow DI, D2. D3.
D4 is ground fault detection relay 67G11.67G21.67G
12°67G22 respectively indicate the ground fault detection direction.

FIG. 7 shows the configuration of the ground fault detection circuit (breaker trip circuit) in the system example of FIG. 6. In the figure, 67G11a and 67G12a.

67G21a and 67G22a are contacts that close when the ground fault direction detection relay 67G11.67G12.67G21°67G22 is operated.

T1. T2. T3. T4 is a time delay circuit that generates an output after a certain period of time after a signal is input. A1. A2. A3. A4 is an AND circuit which outputs a signal when two signals are input simultaneously. OR1, OR2
, OR3, OR4 are logical sum circuits, and when one or both of the two signals is input, a circuit breaker CB1
1. CB12, CB21. It outputs a trip signal to each of the CBs 22. In other words, the AND circuit AI and A3 indicate that both ground fault direction detection relays 67G11 and 67G12 installed at both ends of the power transmission side and load side of the power transmission line have operated.
is detected by the circuit breaker CB11 . This instantly trips the CB12. Similarly, earth fault direction detection relays 67G21 and 67G
22 is activated, the circuit breaker CB21. CB22
I'm trying to make a trip. In addition, as a backup for this, when only one of the power transmission side and the load side is operating, for example, when only the ground fault direction detection relay 67G11 on the power transmission side is operating, the time delay circuit T1 activates the OR circuit after a certain period of time. This trips the circuit breaker CB11 on the power transmission side via OR1. In such a power system, if a ground fault occurs at the 11 points shown in the diagram on the power transmission line L1, a zero-phase voltage V□ will occur on the secondary side of the grounding transformer GTR, and the current limiting resistor connected to this secondary winding will Due to C and R, a ground fault current IO having the same phase as this zero-phase voltage flows to the ground fault point F1, and this ground fault current 0 flows to each power transmission line L1. L'2km becomes zero-sequence current IO1, 102, respectively, and is divided. The 101. IO2 is connected to each power transmission line L1. Zero-phase current transformer ZCT11 provided at both ends of L2.
ZCTl 2, ZCT21. ZCT22 secondary current 1011, 1012, 1021, '022 and '1 ground fault direction detection relay 67G11.67G12.67
G21.67 is supplied to G22. In this case, the ground fault direction detection relay 67G11.67G12.67G21 receives zero-sequence current i. Since 11.1o12゜i and the zero-phase voltage v0 are in the same phase, they operate respectively. As a result, as shown in the configuration of the ground fault detection circuit shown in FIG.
G11 a.

By closing 67G12a, the power transmission line L on the side where the accident occurred
1 both ends breaker CB11. By tripping CB12, the power system is protected from the ground fault F1 point. Note that even if a ground fault occurs in the power transmission line L2, protection is provided in the same way.

[Problems with background technology]

In the above case, the zero-sequence circulating current ■ flowing due to unbalanced system impedance, etc., acts as a sum for '012゜i and as a difference for '011゜' 022, which causes the original ground fault to occur. There are cases where the current cannot be determined due to the influence of zero-phase circulating current, resulting in malfunction or malfunction.

Further, as mentioned above, when a ground fault occurs at the 11 points shown in Figure 6, the zero-sequence current ■0 flowing to point F1 is the zero-sequence current 101 flowing from the bus BUS1 via the breaker CB11, and the zero-sequence current 101 flowing from the bus BUS1 to the breaker CB11. CB21. The current is shunted to the zero-sequence current 102 flowing through the CB22.0B12. The ratio of the shunt values of the shunt zero-phase currents 101 and 102 is the bus line BU
It is determined by the system impedance ratio of each branch line from S1 to fault point F1. Also, this impedance ratio is 1. Since the impedance of L2 is constant, it changes depending on the location where the ground fault occurs. If the ground fault point F1 in Fig. 6 is extremely close to the zero-phase current transformer ZCT11, the impedance of the transmission line L1゜L2 will all be changed from the bus BUSI to the circuit breaker CB21.0B22.0B12.
This is the impedance of the shunt line for the current 102 to the fault point F1 via . On the other hand, the impedance from the bus line BUS1 to the fault point F1 via the circuit breaker CSII includes the power transmission line L1. The impedance of L2 is not included. In other words, the current I01 flowing from the bus line eusi via the breaker CB11 is equivalent to the ground fault current 0 flowing to the point F1, and almost no shunt zero-sequence current 102 flows. Therefore, the ground fault direction detection relay 67G11 on the power transmission side operates, and the ground fault direction detection relay 67G12 on the load side becomes inoperative. As a result, in the ground fault detection circuit shown in Fig. 7, the output signal of the AND circuit A1 is not configured, and even though there is a ground fault on the power transmission line L1 side, the fault cannot be instantaneously interrupted, and the time delay circuit T
1, the power transmission side breaker CBII is cut off after a certain period of time from the operation of the ground fault direction detection relay 67G11. Subsequently, the ground fault current ■0 flowing to point F1 due to the interruption of circuit breaker CB11 is transferred from bus line BLJS1 to circuit breaker CB21.
CB22 and CB12, l0=IO2, the ground fault direction detection relays 67G21, 67G12 operate, and the time delay circuit T2. of the ground fault detection circuit shown in FIG.
The power supply to the bus BUS2 side is stopped only after the circuit breakers CB21.0B12 are respectively cut off after a certain period of time by T3.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned problems, and its purpose is to eliminate malfunctions and malfunctions of protection devices, and to make it possible to determine faulty lines using only the protection devices on the load side of power transmission lines. By doing so, a protection device on the power transmission side can be omitted, and even if the ratio of zero-sequence currents distributed to each power transmission line changes depending on the location of the accident on the transmission line, it is possible to reliably detect a ground fault on the power transmission line. Another object of the present invention is to provide a ground fault detection device that can further downsize the device and save labor.

[Summary of the invention]

The ground fault detection device of the present invention decomposes a zero-sequence current into directional components of each line voltage, stores each component of the zero-sequence current before the occurrence of a ground fault accident as each component of a zero-sequence circulating current, and detects a ground fault. By subtracting the component of the zero-sequence circulating current corresponding to the ground-fault fault phase before the memorized ground-fault fault from the component corresponding to the ground-fault fault phase of the zero-sequence current at the time of the fault, zero-sequence circulation 1! Obtain the component of the ground fault current that corresponds to the ground fault phase from which the influence of the ground fault current has been removed, determine the direction of the ground fault current component, and identify the line where the ground fault fault occurred based on the direction of the determined ground fault current component. It is characterized by discrimination.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of a system configuration for ground fault detection to which the present invention is applied. The same parts as those in FIG. 6 are given the same reference numerals, and the explanation thereof will be omitted, and only the different parts will be described here.

In other words, FIG. 1 shows the ground fault direction detection relays 67G11 to 67G22 provided at both ends of each power transmission line in FIG. 6 and the zero-phase current transformer ZCT11. ZCT
21. Omit the grounding transformer GTR, and instead provide a ground fault detection device GFD only on the load side, and use the zero-phase current transformer ZCT.
The zero-sequence current '012゜i which is the secondary output of 12°ZCT22, the line voltage (a-b, b-c, and ■) which is the secondary output of the zero-phase transformer GPT, and the zero-sequence voltage V.

■c-a It is configured to input.

FIG. 2 is a functional block diagram showing the configuration of the ground fault detection device GFD. In the figure, 1 is a clock that provides the sampling period of this device, and pulse 1 from this clock 1
1, the following processing is performed. FIG. 3 shows the processing operation. This will be explained below with reference to FIGS. 2 and 3.

First, when the pulse 11 is emitted from the clock, the determining means 2 and the extracting means 3 and 4 input each line voltage, zero-sequence voltage, and zero-sequence current (102).

The extraction means 3 is i. 1, which extracts each line voltage direction component, zero-sequence current i and line voltage va-b.

Input vb-co ■ and change the zero-sequence current i to the line C
-a 012 Decomposed into directional components of voltage va-b, b-c, vc-a,
■ Each decomposed component and each line l11M! ' 01a-b ''01b-C'' with a positive sign when the pressure phase difference is Oo and a negative sign when it is 1800.
01C-a (104). For example, zero-sequence current i
If the relationship between and each line voltage has a phase between a-b and vb-c as shown in Figure 4, then the zero-sequence current i
is i' 012 01a-b with magnitude and positive sign and 11 01a-b 01b-c with magnitude and positive sign i'01b-c 01C
i with magnitude represented by -a and negative sign and 1C-
It is decomposed into a.

The extraction means 4 extracts each line voltage direction component of 1. It manually inputs the zero-sequence current i and each line-to-line voltage, performs the same processing as the extraction means 3, and extracts the zero-sequence current i '02a.
-b・'02b-c・'02cma (104).

The determining means 2 uses the line voltages ■a-b, vb-c,'
.

The occurrence of a ground fault accident and the ground fault phase are determined based on vc-a and zero-phase voltage v0 (106, 110). The ground fault phase can be determined by the phases of the line voltages va-b, b-c, and c-a and the zero-sequence voltage V. This is done by comparing the phase of That is, as shown in FIG. 5, the phase of the zero-phase voltage V□ is a, b
, c, the ground fault phase is the C phase,
It is determined that the phase is B phase or C phase. The reason why the ground fault phase can be determined using this method is as follows. That is, a when healthy.

Each phase voltage V a , V b , V c of b, c is 30° clockwise from a-b b-c, c-a in Fig. 5.
゜■ , ■ It is at the rotated position 1 v a , v b '' - v c . Therefore, within a range of 60 degrees in both directions with the center a b at the position v '', v '', v,'' If so, the zero-sequence voltage V. is the phase voltage v”, V
b ”, vC” k-1) Since it is virtually impossible for the phase change due to a near ground fault to exceed 60 degrees, it is difficult to determine whether the phase change is in the range a, b, or c. Accordingly, there is no error in determining that a ground fault has occurred in phases a, b, and c.

When the determination means 2 determines that an accident has occurred, it outputs a pulse 21.
and data 22 indicating the ground fault phase are outputted to the removal means 6, and when the occurrence of an accident is not determined, a pulse output 23 is outputted to the storage means 5. The storage means 5 operates on the pulse 23 from the discriminating means 2, that is, when no ground fault has occurred, and stores the output of the extraction means 3.4 at each sampling period.
That is, the zero-sequence current components decomposed by the extraction means 3 and 4 are divided into the line voltage components of the zero-sequence circulating current.
1b-c.

' j 1 cma and ' M 2a-b-' fJ2b
-c-' j! It is stored as 2 cma (108).

The removing means 6 is for removing the influence of the zero-phase circulating current, and the removing means 6 is operated by the pulse human power 21 from the determining means 2. Based on the ground fault phase 22, 1 is extracted from the component corresponding to the ground fault phase of the zero-sequence current component output from the extraction means 3.4.
A ground fault fault corresponding to the ground fault phase of the ground fault current obtained by subtracting the component corresponding to the ground fault phase of the zero-sequence circulating current component stored in the storage means 5 before the sampling period to remove the influence of the zero-sequence circulating current. Output means 7 for determining current components 'f1 and' f2
(112). For example, if the ground fault phase is C phase,
'fl is i. 1. - from '11a-b,' f2 is '02a-b from' 412
It is obtained by subtracting a-b. Also, if it is in phase b, 'f
1 is '01b-c minus' j Ib-6 = f2 is '02b-C to' II 2b
-c is subtracted.

Similarly, if it is C phase, 'fl is '01e-a to i
ρ1cma is subtracted = f2 is ' 02c
It is calculated by subtracting 12 cm from ma.

The judgment output means 7 detects the ground fault current components i and i corresponding to the ground fault phase from the removal means 6.
2. Determine the line where the occurrence occurs (114), and output a signal to cut off the determined line (116, 118). For example, if 'fl is positive and' f2 is negative, the line where the ground fault occurred is determined to be Ll, and if 'f1 is negative and' f2 is positive, the line where the ground fault occurred is determined to be L1, and the former Case CB11.0B1
116), in the latter case, the trip signals 03,0 to CB21°CB22 should be output.
4 is output (118).

〔Effect of the invention〕

As described above, according to the present invention, since the ground fault fault judgment is made based on the original ground fault fault current from which the influence of the zero-sequence circulating current has been removed, malfunction or malfunction of the protective device is eliminated. . Furthermore, since faulty lines can be determined only by the protection device on the load side of the power transmission line, the protection device on the power transmission side can be omitted. Furthermore, even if the ratio of zero-sequence currents that are divided into each power transmission line changes depending on the location on the power transmission line where the accident occurs, it is possible to reliably detect a ground fault accident in the power transmission line. Furthermore, it is possible to downsize the device and save labor.

[Brief explanation of the drawing]

FIG. 1 is a ground fault detection system diagram according to an embodiment of the present invention, FIG. 2 is a block diagram showing an embodiment of the present invention, FIG. 3 is a flowchart showing processing operations in an embodiment of the present invention, and FIG. The figure is a vector diagram showing the relationship between zero-sequence current and each line voltage,
FIG. 5 is a vector diagram showing the phase relationship between the ground fault phase and line voltage, FIG. 6 is a conventional ground fault detection system diagram, and FIG. 7 is a diagram showing a conventional ground fault detection circuit. DESCRIPTION OF SYMBOLS 1... Ri0tsuku, 2... Discrimination means, 3.4... Extraction means, 5... Storage means, 6... Removal means, 7...
・Judgment output means. Applicant's agent Kiyoshi Inomata Figure 2 Figure 4 Figure 5 Figure e1

Claims (1)

[Claims] In a ground fault detection device for a system equipped with a zero-phase current transformer and a zero-phase transformer on the load side of each line, each line voltage, zero-phase voltage, and zero-phase current from each zero-phase current transformer are used. means for decomposing the zero-sequence current into directional components of each line voltage; means for determining the occurrence of a ground fault based on the zero-sequence voltage; A means for storing each component, a means for determining the ground fault phase from the zero-sequence voltage and each line voltage when a ground fault occurs, and a means for storing the components of the zero-sequence current corresponding to the ground fault phase at the time of a ground fault. means for obtaining a component of the ground fault fault current corresponding to the ground fault fault phase from which the influence of the zero-sequence circulating current has been removed by subtracting the component of the zero-sequence circulating current corresponding to the ground fault fault phase before the ground fault fault; A ground fault detection device for a parallel two-line system, comprising means for determining the direction of the ground fault current component and means for determining the line in which the ground fault has occurred from the determined direction of the ground fault current component.