JPS6356121A - Ratio differential relay - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a ratio differential relay for power system protection, and particularly to a high-performance protection relay that can prevent malfunctions due to current transformer saturation in a signal input circuit. .

[Conventional technology]

As described in Japanese Patent Publication No. 54-21940, conventional ratio differential relays use the absolute value of the current passing through the protection zone as the control amount as a measure to prevent malfunctions due to saturation of the current transformer that takes in the input signal. This is inconvenient for widening the operating range, so-called high sensitivity.

[Problem that the invention seeks to solve]

SUMMARY OF THE INVENTION An object of the present invention is to provide a ratio differential relay having a highly sensitive operating range even if saturation of a current transformer that obtains an input signal occurs.

[Means for solving problems]

In order to obtain a highly sensitive operating region, the control amount is always weakened, and when an external fault occurs, the suppression amount is memorized using a signal before the current transformer becomes saturated. Use it during the time period.

Prevent malfunction.

However, if an internal accident occurs while the suppression amount is being memorized, the operation may be delayed.

Therefore, in the present invention, high-speed operation is controlled so that the operation time is not delayed even in the case where there is a serious internal accident and most of the current passing through each terminal within the protection zone becomes the internal fault current. Let's do it.

[Function] As a measure to increase speed in the event of an internal accident, a low-sensitivity relay that can perform phase comparison of the current passing through the protection zone or low-sensitivity ratio differential judgment is provided, and this suppression amount is memorized and a certain ratio is set. By controlling the differential relays, serious internal faults or simple internal faults caused only by inflow current can be detected at high speed and with high sensitivity.

〔Example〕

FIG. 1 shows an embodiment of the present invention.

A line 1 that is part of the power system is connected to circuit breakers 2A and 2B at the A and B terminals.

The line 1 may be a power equipment equivalent to a bus bar, a transformer, a generator, a capacitor, etc. The line 1 is not limited to terminals A and B, and may have multiple terminals, but it may be a two-terminal line. 1 will be explained as a protection target.

3A and 3B are current transformers for obtaining input signals of the ratio differential relay device 100.

EA and E are power supplies connected to the A terminal and B terminal, respectively.

F is the point of an accident within the protected area (hereinafter referred to as an internal accident, and an accident outside the area is referred to as an external accident), and the current I 1111 I
11□ are the primary currents of current transformers 3A and 3B, respectively, and the secondary type currents are I,,I,.

When the voltages of power supplies E and E are in phase, the secondary current generator and 1. current transformer 3A so that they are in the same phase.

Determine the polarity of 3B.

When an internal accident occurs as at point F, a cutoff command is given from the ratio differential relay device 100 to the breakers 2A and 2B. The cutoff command is output R of the ratio differential relay device 100.
This is done by Y generating a high level voltage, and the protected area is separated from the power grid.

Next, the internal operation of ratio differential relay device 100 will be explained.

10 is a low sensitivity relay. The low sensitivity relay 10 has its sensitivity reduced so as not to malfunction in the event of an external fault even if a magnetic saturation phenomenon occurs in the current transformers 3A and 3B and an error occurs in the output current.

The output of the low sensitivity relay is indicated by R1°. Output R1° produces a high level output voltage only when an internal fault is detected.

20 is a ratio calculation section.

The ratio calculation unit 20 receives the current transformer secondary current 1, which is an input signal.
．． 1. Based on, ■8□=l I, +1. I-, (I 1.Ill
1. I)...Calculate (1).

However, I and 11 are the output signals of the ratio calculation section 20 and K.

is a constant that determines the inhibition tl1M.

Equation (1) adds the conventionally known suppression of the protection interval passing current by a scalar amount, and the first term on the right side of Equation (1) is the operating amount, and the second term is the suppression amount. .

21 is a level determiner, and if Ill in equation (1) is a predetermined value, for example, Pl, the output R1 of the level determiner 21 is determined by a larger value ■, , >P, . . . only in (2) generates a high level voltage output.

The conventional ratio differential relay device immediately determines that an internal fault has occurred when the output R0 is at a high level.

However, with only the output R1, when the primary current I AX f I 11 of the current transformers 3□, 311 includes a transient DC component, a secondary current saturated with one polarity due to the DC deviation is generated. Despite an external accident, the operating amounts II, +I, and l shown in equation (1) increase, and if a highly sensitive determination is performed, the output R1 may reach a high level, that is, a malfunction may occur.

As a means to prevent this malfunction, the output L of the ratio calculation section 20
When X is a negative value, this means that the amount of suppression is larger than the amount of operation in equation (1), so using this as the amount of suppression, current transformers 3°, 3. is stored for a time ΔT during which saturation of 61
Use again as a time suppression amount.

The negative value memory shown in FIG. 31 has this storage function.

In the negative value memory 31, only when the input signal Iti is negative,
Remember that value.

When the storage time is ΔT, its setting is set by the timer 32.

However, in embodiments of the invention, the timer 32
'When RL becomes negative, the memory function of the negative value memory 31 is started and input signal processing is performed. 61 hours after 1 becomes positive or zero, the memory function of the negative value memory 31 is stopped,
The stored values are also cleared to zero. The output signal for setting and clearing in this way is T.

33 is an OR gate, and the contents of the negative value memory 31 are also cleared by the operation output of the low sensitivity relay.

That is, Tc is a clear signal. When clearing the contents of the negative value memory 31, it is assumed that the output TM of the timer 32 or the output R111 of the low sensitivity relay 10 is at a high level. The output of the negative value memory 31 is input to the input signal generator, □
From those stored for ΔT time, the maximum value, the average value, or simply the input signal value, the value obtained by shifting □ by ΔT time, etc. are obtained as the output signal value □.

34 is a second ratio differential calculation unit; =1. , −, I□ = lI, +1. l-to □(l 工、l + l I、
l) -to, lI,.

...(3) This is an element that calculates .

In equation (3), the third term on the right side is the second suppression amount by the suppression amount storage. KH is a constant that determines the suppression coefficient, and the current transformer 3. ．． 3. In view of the performance of the ratio differential relay device 100, the magnitude of the passing current, the setting value of the operating range of the ratio differential relay device 100, etc., it is determined to prevent malfunction.

The output from equation (3) is □.

35 is a level judger, and if □ is a predetermined value, for example P2, then ■ is the input signal. >p,
...Only in (4), the operating side output, that is, the output R2, is set to a high level voltage.

Reference numeral 36 denotes an AND gate, which generates an operational output, that is, a high-level voltage as the output signal R2 only when both the signals R1 and R are at high-level voltages.

The OR gate 37 generates a high level voltage at the output RV as an operating output when either or both of the output R1° of the low sensitivity relay 10 or the output R1□ of the AND gate 36 is at a high level.

When output RY is at high level voltage, circuit breaker 2□, 2
．． is the trip permissible.

Figure 2 is an example of the low sensitivity relay shown in Figure 1,
(a) is a method for detecting internal faults by comparing the phases of the currents at each terminal in the protection zone.

11. 11. is a level slicer which generates a high level voltage only when the input signal is equal to or higher than the level, for example, level 11 or higher. Its output voltage is V Mal V%&
It is.

12 is an AND gate, and input signals V A B and ■.

The output voltage V A is only when both are at high level voltage.
S 8 becomes a high level voltage.

13 is a timer, and when the input signal V A 118 remains at a high level voltage for a certain period of time TA11, for example, T a m = 5 m S or more in a 50 Hz frequency system, an output signal R□ is generated. becomes a high level voltage,
The return lasts -cycles, 20 ms.

As described above, when the secondary currents I, , I, of the current transformer are sufficiently larger than the determination level (3) of the level slicer, the operation can be performed with the phase difference between the two currents I, , I, within 90°.

The waveforms shown in FIG. 3(b) explain the input and output signals of each block shown in FIG. 2(a) using the same symbols.

FIG. 3 shows one embodiment of the low sensitivity relay 10. 5
1 is an or gate, and level slicers 11, . 11.
(7) This is to obtain the OR output of the high level voltage of the output signal V A 111 V 11 M, and V aat
Va.

When any of the voltages are at high level, the output voltage v
Q6 becomes high level.

The timer 52 receives an input signal V. , is at a low level for a certain period of time T. R or more, for example, T, , = 5ms or more, the output on the operating side, that is, the high level voltage is Ro
. occurs in The return is performed at 2 in the same way as timer 13 in Figure 2.
0m5, it can be used in the applicable frequency system of 50 Hz.

According to this method, the outflow current is 1s, which is the value of the level slicer.
If it is smaller than , an internal fault can be determined, so even if there is a serious internal fault, for example, the inflow current is larger than the level slicer, the outflow current is sufficiently smaller than that, and there is a non-current end, the internal fault can be detected. is possible and can operate regardless of the operating output R1i shown in FIG.
High-speed operation is possible when an external accident progresses to an internal accident.

In addition, the low sensitivity relay 10 may be an overcurrent relay that operates when the current at each terminal is above a certain level, a distance direction relay, or an undervoltage relay.

FIG. 4 shows an example of internal fault detection in the ratio differential relay device 10 of the present invention.

This is a case where the current IAt flows from the A terminal 1 and the B terminal current Imx=Im=O.

Current transformer 3°, 3. Considering 1:1, ■1□=I.

This is an indication.

The output I+1 of the ratio differential section 20 is a smoothed AC signal. When output crab 1 is equal to or higher than the determination level P1, the operation is activated, and the output R1 becomes high level.

The operating time at this time was set as t□.

The output T of the timer 32 remains at a high level because the input signal I* of the timer 32 is positive.

As explained in FIG. 3, the low sensitivity relay 10 has an operating time t.
This is an example of operating on ia.

Therefore, the clear signal T of the negative value memory 31. remains at a high level and is a continuation of Kriya.

Therefore, the output RIM of the negative value memory continues to be zero.

The output T0 of the ratio differential calculation unit 34 is only the input signal r+tt, and I Km =I K1.

The output R2 of the level determiner 35 is activated when the signal I12 is greater than the level determination value P2, and the operation time is t.

The output R2 becomes high level.

From the above, since both the output R1 of the AND gate 36 and the output RV of the OR gate 37 change to a high level indicating operation, an internal accident can be detected.

Even if there is an outflow current at the B terminal, the ratio differential (calculation unit 20.
If the output of 34 reaches a predetermined determination level,
It can operate similarly to this description.

FIG. 5 is an explanatory diagram of the operation contents when an external accident progresses to an internal accident.

This is an example in which the current transformer 36 at the B terminal was saturated transiently from the cycle after an external fault occurred, and in about the fifth cycle, the external fault current was cut off, an internal fault occurred, and the current flowed from the A terminal. be.

The output I tx of the ratio differential calculation unit 2o becomes a negative value immediately after the occurrence of an external fault, but due to the current transformer saturation at the B terminal, the difference current (
IA+I,) increases and becomes positive.

After an internal accident, it becomes even larger in the positive direction.

Therefore, when the output crab □ is level 21 or higher, the output R of the level determiner 21 becomes operational, and it can be seen that if it continues as it is, it will malfunction even in the event of an external accident.

Therefore, the timer 32 allows the negative value memory 31 to be set, and enters the function of storing the negative value of the signal □ for a period of ΔT.

However, after an internal fault occurs, the input current becomes only 11, and the low sensitivity relay 10 produces an operating output at RID. As a result, the output Tc of the OR gate 33 becomes the clear signal and the output (■) of the negative value memory 31. Set to zero.

Therefore, the output I□ of the ratio differential calculation section 34 becomes higher than the level judgment value P2 of the level judgment device 3S in the positive direction, and the operating output is outputted to R2.

As a result, the output R of the AND gate 36 is 2. With the output RV of the OR gate 37, the operating side output can be obtained at high speed after an internal accident occurs.

If the low-sensitivity relay 10 is not used, the operation time will be delayed by the time Tlx shown in FIG. 5, depending on the time ΔT during which the suppression amount is stored.

Furthermore, the present invention can also be performed by digital calculation, and the calculation flow is shown in FIG.

It is convenient for digital calculation to repeatedly sample the input signals I, , I, at the same time. In the figure, operating conditions are indicated by 1 (equivalent to high level) and others by O (equivalent to low level).

〔Effect of the invention〕

According to the present invention, internal faults can be detected with high sensitivity and high speed, and malfunctions due to current transformer saturation can be reliably prevented.

[Brief explanation of drawings]

Figure 1 is a system diagram of one embodiment of the present invention, Figures 2 and 3 are diagrams of an embodiment of a low sensitivity relay used in the present invention, Figure 4 is a side view of the operation in the event of an internal accident, and Figure 5 is a diagram of an embodiment of the low sensitivity relay used in the present invention. FIG. 6, which is a diagram showing an example of the operation at the time of an external accident and an internal accident, is a flowchart of calculation implementation when the present invention is performed by digital calculation. 10...Low sensitivity relay. 1, - Agent Patent attorney Katsuo Ogawa, '5 Circular 1 Figure p-No.
- Soryokui 20 //A (b) 躬3 霞ljΔ (b) Ichigin Yami 躬年 蛬内茔 p δ miss occurrence shouting question 5m 菟 6 fig.

Claims (1)

[Claims] 1. The line current of each terminal in the protection zone is individually taken in as an input signal via a current transformer, and the vector sum current of the input signals is operated as a means for detecting an internal fault in the protection zone. What is claimed is: 1. A ratio differential relay device that controls a current value or a stored value of a quantity or a scalar quantity, wherein the ratio differential relay is controlled using an internal fault detection relay. 2. A ratio differential relay device according to claim 1, characterized in that the internal fault detection relay is carried out by identifying a phase difference between line currents at each terminal within the protection zone. 3. The ratio differential relay device according to claim 1, characterized in that the internal fault detection relay is equipped with a low-sensitivity one. 4. The ratio differential relay device according to claim 1, wherein an internal fault is identified by an OR determination of the operational outputs of the internal fault detection relay and the ratio differential relay. 5. The ratio differential relay device according to claim 4, characterized in that a distance direction relay is used as the internal accident detection relay.