JPS631809B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Technical Field The present invention is a line selection ground fault directional relay device applied to a power transmission line system with two parallel lines, in which the relay at one end is activated in the event of a ground fault at the nearest end of the other end. This invention relates to a line selection ground fault directional relay device configured to prevent the device from accidentally tripping in series.

(b) Prior art A relay device that implements a line selective relay method for a parallel multi-circuit high-resistance grounding system in which a zero-sequence circulating current exists is configured as shown in Figure 1. The figure shows the case of R-phase failure detection). In FIG. 1, I ₀ is a zero-sequence current corresponding to the zero-sequence current difference between two lines. This zero-sequence current I ₀ is led to a storage capacitor 13 as a voltage signal via a current transformer 11 and a gate circuit 12, and is further passed to a level detection circuit via a differentiating circuit 16 consisting of a series capacitor 14 and a shunt resistor 15. Guided by 17. The DC voltage ±K ₀ is also input to the level detection circuit 17 as a detection level signal, and the input signal from the differentiating circuit 16 has a larger amplitude than the DC voltage ±K ₀ .
The level detection circuit 17 is a line selection signal for line 1.
Outputs the line selection signal V _OUT 2 for V _OUT 1 or line 2.

On the other hand, the voltage V _ST between the S and T phases of the system is
8 to the sampling pulse generation circuit 19. This circuit 19 issues a sampling pulse at a specific phase point of _VST to turn on the gate circuit 12.

In the device shown in Figure 1, in order to memorize the effective component I ₀ cos θ of the constant zero-sequence current and see the change in I ₀ cos θ after a failure, it is necessary to use the zero-sequence voltage generated at the time of the failure as the polarity quantity. Because it cannot be done, it always exists and is 1
The amount that does not change when a line-to-ground fault occurs is used as the polarity amount. For example, for a failure in the R phase, the voltage V _ST between the S and T phases is used, V _TR is used for the S phase, and V _RS is used for the T phase. Therefore, the line selection signals V _OUT 1 and V _OUT 2 need to be phase-selected by each phase failure detection output 28, and the line selection outputs V _OUT 1 and V _OUT 2 are obtained via the AND circuits 20A and 20B. .

Next, the principle of change in zero-sequence current I ₀ and faulty line selection will be explained with reference to FIGS. 2a and 2b. In the figure, 21 and 22 are parallel two-line systems grounded through a high resistance 23, where line 21 is one
Assume that line 22 is line 2. The currents in both lines are led to the line selection relay device 25A via the main current transformers 24A and 24B. Figure 2a shows the state before a fault occurs, and the zero-sequence circulating current Ioth is connected to both lines as shown in the figure. Assume that it is circulating between lines. Figure 2b shows the situation when a ground fault occurs at point F1 of line 1 _21. In addition to the zero-sequence circulating current Ioth, there are fault currents If _A and If _B at each line end. flows. Note that each zero-sequence current has a positive direction in the direction of inflow into the protection section.

Before the failure in FIG. 2a, the amount of electricity I ₀ introduced into the relay device 25A is given by equation (1).

I ₀ = Ioth - (-Ioth) = 2 Ioth (1) The electrical quantity I ₀ after the failure in FIG. 2b is given by equation (2).

I ₀ = (If _A − If _B ) + 2Ioth …(2) Change when comparing equations (1) and (2) (If _A − If _B )
If the direction is determined by , line selection becomes possible regardless of the existence of the electric quantity Ioth. For example, if _A > If _B , line 1 21 is determined to be a failed line, and if _A < If _B , line 2 22 is determined to be a failed line.
If If _A = If _B , there is an external failure and there is no change corresponding to If _A - If _B = 0, and the relay device 25A will not operate properly.

Next, a case where a line selection relay device is provided at both terminals and an internal accident occurs at the end closest to the other end will be described with reference to FIG. Explanation of similar parts in Figure 2 will be omitted.24
C and 24D are main current transformers for both lines, 25B is a line selection relay device installed at the B end, and 26A to 26D are line breakers.

Assuming that the A end is the own end and the B end is the other end, if a ground fault occurs at _{the two} points F inside the end closest to the other end, the change in the zero-sequence current introduced to the own end relay device 25a is
Since If _A ≒ If _B , a state close to zero can be considered. At this time, the relay device 25A is inoperable, and only the other end relay device 25B is in operation. In this manner, there is a case where only one end operates due to a failure at the end closest to each terminal. This range is determined by the sensitivity of the relay device, but it usually occurs when a failure occurs between one-third of the total length of the transmission line from each end.

When the other end relay device 25B operates, the disconnector 26
When C is tripped, the fault current If _B becomes zero and at the same time the zero-sequence circulating current Ioth also becomes zero, causing a change in the zero-sequence current introduced into the own-end relay device 25A, and the relay device 25A This is a so-called series trip. At this time, the current flowing through the grounding resistor 23
Assuming that If and Ioth have the relationship shown in FIG. 4, the changed current introduced into the relay device 25A is judged to be a failure on the line 2 22 side, and the disconnector 26B of the healthy line malfunctions. As a countermeasure against this, the relay device 2
5A for a certain period of time (T) depending on ground fault overvoltage conditions.
A series tri-lock method is adopted.

This series trip lock output 29 (see Figure 1) is connected to AND circuits 20A, 2 along with the line selection outputs of V _OUT 1 and V _OUT 2 and the failure detection outputs 28 of each phase.
0B to control the line selection outputs V _OUT 1' and V _OUT 2'. FIG. 5 shows an operation time chart of the line selection device shown in FIG. 1 described above. In Fig. 5, operating time of V _OUT 1 and V _OUT 2: T ₁ (10 to 20 ms) Operating time of failure detection output 28: T ₂ (30 to 70 ms) Operating time of shield circuit breakers 26A to 26D: T ₃ (20～
30ms). Also, the maximum value of the fluctuation of each element operation time is
MAX and MIN shall be added to the minimum value.

At this time, the series trip lock time T must satisfy the condition of equation (3) shown below, as described above.

Other end line selection output V _OUT 1' operating time MIN + shield breaker operating time MIN + own end line selection signal V _OUT 2
Operating time MIN > T > Other end line selection output V _OUT
1' operating time MAX + shingle breaker operating time MAX...(3) From equation (3), if the operating times of line selection outputs V _OUT 1' and V _OUT 2' fluctuate, the settling of this lock time (T) will be extremely difficult. becomes difficult.

On the other hand, each phase failure detection device 28 shown in FIG. 1 employs an undervoltage detection device, but the operating time T ₂ varies by about 30 to 70 ms depending on the degree of ground fault, which causes the above-mentioned problems.

From the relationship of the time chart in Figure 5, the value of equation (3) is as follows.

T _2MIN +T _3MIN +T _1MIN >T>T _2MAX +T _3MAX (30+20+10)ms>T>(70+30)ms 60ms>T>100ms Therefore, T cannot be set and there is a risk of malfunction due to series trip.

(c) Purpose of the Invention The present invention has been made in consideration of the above points, and an object of the present invention is to obtain a line selection ground fault directional relay device that has a simple configuration and facilitates time setting of the series trip lock function. This is what I did.

(d) Structure of the invention FIG. 6 shows an embodiment of the invention. The same parts as in FIG. 1 are given the same symbols and their explanations are omitted here.

The outputs V _OUT 1 and V _OUT 2 of the level detection circuit 17 are introduced into AND circuits 20A and 20B via time-limited operation circuits 27A and 27B, together with the failure detection conditions for each phase and the series trip lock conditions, respectively, and the V _OUT
1'', V _OUT 2'', each line selection output for line 1 and line 2 is obtained.

(e) Operation of the invention Next, the operation of the invention configured as shown in FIG. 6 will be explained using the time chart shown in FIG. 7.

The time-limited operation circuit 27 delays the operation time of the level detection circuit by a certain period of time (t), eliminates the influence of each phase failure condition that has a lot of fluctuation in operation time, and outputs the line selection output V _OUT.
By reducing the fluctuations in the operating times of 1'' and V _OUT 2'', it becomes possible to widen the series trip lock time setting range determined by equation (3). (however,
V _OUT 1', V _OUT 2' in equation (3) are V _OUT 1'', V _OUT
2″ respectively).

As an example, if t=70ms, the series trip lock setting can be set within the following range from equation (3).

{(T _1MIN +t)T _3MIN +(2T _1MIN +t)}>T> {(T _1MAX +t)+T _3MAX } (10+70+20+20+70)ms>T>(20+70+30)ms190ms>T>120ms Therefore, series trip block is easy It is possible to realize a line selection ground fault direction relay device that can be set.

(f) Overall effect When a line selection relay device is installed at both terminals, as mentioned above, if the operating time of the relay device varies greatly, it becomes very difficult to set the series trip lock, or it may become unstable. In some cases it is possible. Furthermore, if the line selection relay devices installed at both ends employ different principles, the operating times of the devices at both ends will also differ, making series trip lock setting for the devices at both ends complicated.

However, according to the invention, the above-mentioned problems can be solved and series trip lock setting can be made easier.

[Brief explanation of the drawing]

Figure 1 shows a conventional line selection ground fault directional relay device (R
Figures 2a and b are system diagrams showing the applied transmission line before and after failure, Figure 3 is the applied transmission line system diagram, and Figure 4 is the vector relationship between fault current and zero-sequence circulating current. FIG. 5 is an operation time chart of a conventional line selection relay device, FIG. 6 is a diagram of a line selection ground fault direction relay device (R phase) showing an embodiment of the present invention, and FIG. 7 1 is an operation time chart of the line selection relay device of the present invention. 11...Current transformer, 12...Gate circuit, 13...
...memory capacitor, 14...series capacitor,
15...Shunt resistance, 16...Differential circuit, 17...
Level detection circuit, 18...Transformer, 19...Sampling pulse generation circuit, 20A, 20B...
AND circuit, 24A, 24B, 24C, 24D...
...Main current transformer, 25A...A-end line selection relay device,
27A, 27B...Time-limited operation circuit, 28...Each phase failure detection output, 29...Series trip lock output.

Claims (1)

[Claims] 1 When the phase difference between the zero-sequence current difference I ₀ between two lines and the zero-sequence voltage V ₀ that occurs during a ground fault is θ, the effective component I of the zero-sequence current difference I ₀ with respect to the zero-sequence voltage V _{0 0} cosθ to 1
The amount of voltage that does not change when a line-to-ground fault occurs is constantly stored, and the change in I ₀ cos θ before and after the fault is detected.
A line selection signal is obtained by determining the polarity and magnitude of this change output, and an output obtained by delaying this line selection signal by a time-limited operation circuit, and an output obtained from a ground fault detection device for each phase. A line selection ground fault directional relay device characterized in that line selection is performed by an AND output with a series trip block output that operates after a scheduled time from the point of occurrence of a ground fault fault.