JPH02136027A - Differential relay device - Google Patents

Abstract

PURPOSE:To obtain a differential relay device of quick operating time by providing an undervoltage relay reset after the fixed time from closing a power source to a transformer. CONSTITUTION:When an internal accident is generated after an undervoltage relay 11 is reset, a ratio differential element 6 operates and the second harmonic content detecting element 7 transiently operates, but the undervoltage relay 11 is not in operation, so that an AND circuit 10 generates an output '0'. Accordingly, an output is '1' of a NOT circuit 8, and an output of the ratio differential element 6 is left as it is, serving as an output (output of ratio differential relay 1A) of an AND circuit 9. As the result, the ratio differential relay 1A, when the internal accident occurs, provides its operating time equal to the operating time of the ratio differential element 6, and the ratio differential relay, operating earlier by the amount of no time locked by an output of the second harmonic content detecting element 7, is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a differential relay device used to protect a power transformer.

(Prior art) Fig. 6 shows an example in which the ratio differential relay 1 is applied to a power transformer 2. 3 in the figure shows the current r't of each terminal of the transformer 2.
, a current 11 corresponding to I'2, a main current transformer for introducing I2, 4A and 4B are circuit breakers, and 22 is a system power supply.

FIG. 7 shows an example of ratio characteristics of the ratio differential relay 1, and FIG. 8 shows an example of second harmonic lock characteristics. To briefly explain the necessity of this 21iI wave lock characteristic, the transformer excitation inrush current flows from the power supply side when the power is turned on to the transformer, as if it were an internal accident in the overvoltage transformer. Therefore, there is a possibility that the ratio differential relay may malfunction (operate even though there is no accident).

Therefore, it is necessary to distinguish between the excitation inrush current and the current caused by an actual accident.

Since the excitation inrush current has a characteristic that it contains a large amount of second harmonic component, generally when the ratio of the second harmonic component to the fundamental wave component exceeds a certain set value (generally about 15% is often used), , it is often used to lock the output of a ratio differential relay to prevent malfunction of the relay.

FIG. 5 shows an example of a circuit of a conventional ratio differential relay for protecting a transformer. In Fig. 5, 5 is the input transformer, 6 is the sixth
7 is a ratio differential element having the ratio characteristic shown in the figure, 7 is a second harmonic content detection element having the second harmonic lock characteristic shown in FIG.
807 circuit that inverts the output of the harmonic content detection element, 9 is an AND that takes the AND of the ratio differential element 6 and the 807 circuit 8
It is a circuit.

In FIG. 9, input current 1. , I2 are introduced into the ratio differential element 6 and the second harmonic content detection element 7 through the input transformer 5, respectively. The input currents 11 and I2 introduced into the ratio differential element 6 are equal to the differential amount Id in the ratio differential element 6.
=I11+I2 1 and suppression amount 1r=k (l It
l+l I2 l ) [Here, k is a constant] is derived. Furthermore, the differential amount Id and the suppression amount Ir are added to derive the operating amount (Ia Ir).

The time ratio differential element 6 whose operation amount (Id Ir) is larger than 4 [here, 1 is a constant] outputs a constant value.

As described above, the operating formula of the ratio differential element 6 is If +I2 l k (l 111+l I2
i)≧1, resulting in the ratio characteristic shown in FIG.

On the other hand, the input current 11, I2 introduced into the second harmonic content detection element 7 derives the differential amount Td=l II +12 1 in the second harmonic content detection element 7, and further from the differential amount Id. Fundamental wave ff1k211f1 and second harmonic amount 12
Derive f1. 211fl and the second harmonic amount 12f1 are added to this basic pumping amount, and the operating amount (l 2fl- is 211
fl ) is derived. Dynamic Fe amount (211 in l 2fl-
When fl ) is greater than zero, the second harmonic content detection element 7 outputs.

When the above content is transformed, l 2fl / l 01≧2
This means the content rate of the second harmonic, and its characteristics are the lock characteristics shown in FIG. The output of the second harmonic content detection element 7 “
1" becomes "0" at NOT time g@8. Since the output of the ratio differential element 6 and the output of the 807 circuit 8 are introduced into the ANDN0 circuit, the second harmonic content detection element 7 operates to lock the output of the ratio differential relay 1.

FIG. 10 shows the response of the ratio differential relay 1 when a transformer excitation inrush current flows. Even if the ratio differential element 6 operates due to the transformer magnetizing inrush current when the power is turned on, the second harmonic content detection element 7 operates faster due to the second harmonic current contained in the transformer magnetizing inrush current. In order to operate, the output of the ratio differential element 6 is locked by the output of the second harmonic content detection element 7, so that the ratio differential relay 1 will not produce an erroneous output due to the excitation inrush current.

(Problems to be Solved by the Invention) FIG. 11 shows the response of the ratio differential relay 1 in the event of an internal accident. As described above, the second harmonic content detection element 7 is for detecting the second harmonic current contained in the transformer excitation inrush current when the power is turned on, and for preventing the ratio differential relay 1 from malfunctioning. However, due to the transient response of the filter that extracts the highly selective second harmonic amount 12f1 as shown in Fig. 8, due to the sudden change in the internal fault current that does not contain the second harmonic current. The output of the second harmonic content detection element 7 is output. Therefore, the internal fault ratio differential element 6 outputs at time c2, but it is locked by the transient output C1 of the second harmonic content detection element 7, so until the transient lock is released. The output of relay 1 is delayed by time C3, and relay 1
There is a problem in that the operating time t4 of is relatively long.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a differential relay device with short operating times.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention inputs the amount of electricity corresponding to the current flowing through each terminal of the transformer, and calculates the difference obtained from the amount of electricity input to each terminal. A differential element that outputs when the amount of electric power is equal to or more than a predetermined value, and an output of the differential element when the ratio of the second harmonic component to the fundamental wave component included in the input amount of electricity is equal to or more than a predetermined value. In a differential relay device having a locking second harmonic content detection element, an element for detecting no-voltage of the transformer terminal voltage is added, and on condition that the no-voltage detection element is restored, after a certain period of time, The second harmonic content detection element output is configured to be locked.

(Function) Since it is equipped with an undervoltage relay 11 that returns after a certain period of time after the power is turned on to the transformer 2, when the undervoltage relay 11 is operating, the second harmonic content rate can be detected. The output of element 7 can be activated and locked when inactive. Therefore, malfunctions can be reliably prevented in the same way as in the past when it comes to the excitation inrush current that occurs when the power is turned on to the transformer 2, and when an internal fault is detected, the transient output of the second harmonic content detection element 7 The differential 111 has no delay in operation time and therefore has a fast operation time! We can provide electrical equipment.

(Example 8a) Examples will be described below with reference to the drawings.

FIG. 1 shows an example in which a ratio differential relay 1A according to the present invention is applied to a power transformer 2, and a new undervoltage relay 11
is added, and the output of this undervoltage relay 11 is introduced into a ratio differential relay.

FIG. 2 shows a differential relay device according to the present invention, which has a functional block configuration in which a ratio differential relay 18 and an undervoltage relay 11 are combined. The same reference numerals are given to the same parts as in FIGS. 4 and 5.

In FIG. 2, 12 in the undervoltage relay 11 is an input transformer, and 13 is an undervoltage detector that operates when power is not applied to the transformer 2 and returns when power is applied to the transformer 2. Element 14 is an operation delay circuit that has a time longer than the time required for the fault to be removed and the grid voltage to stabilize in the event of an internal or external fault; 15 is an operation delay circuit that attenuates the excitation inrush current that flows when the power is turned on to the transformer 2; 10 of the ratio differential relay 1A is an AND circuit that takes the logical product of the output of the undervoltage relay 2811 and the output of the second harmonic content detection element 7; This is a NOT circuit that inverts the output of ANDN0 circuit 1, and the other configurations are the same as in FIG. 5.

The operation of the present invention will be explained with reference to the configuration diagram in FIG.

The operation of the ratio differential element 6 and the second harmonic content detection element 7 is the same as in the prior art.

When the power is not applied to the transformer 2, the undervoltage relay 11 is in operation, and the ANDN0 circuit 1 of the ratio differential relay 1A says ``The IJ signal is applied.If the power is applied to the transformer 2 in this state, , the excitation inrush current flows and the ratio differential element 6 operates, and the second harmonic content detection element 7 operates, and the "1" signal enters the other input of the ND circuit 10. At this time, the output of the undervoltage relay 11 is rl for the time required to be resolved by the recovery delay circuit 15, so both inputs to the NO circuit 10 become "1" and the output also becomes "1". This output is inverted by the NOT circuit 8, and a "0" signal is input to the ANDN0 circuit. ANDN
The 0 circuit output is "0" while the output of the NOT circuit 8 is "0" even if the output of the ratio differential element 6 is "1". As a result, when the excitation inrush current flows, the conventional ratio differential as shown in Fig. 10! l! The response is the same as that of the electric appliance 1, and the output of the ratio differential element 6 can be blocked by the output of the second harmonic content detection element 7, thereby reliably preventing malfunctions due to excitation inrush current.

When the undervoltage relay 11 returns after a time determined by the return delay circuit #115 (longer than the time for the excitation inrush current to attenuate), the signal introduced into the ANDN0 circuit 1 becomes "o". Therefore, if an internal accident occurs after the undervoltage relay 11 is restored, the ratio differential element 6 operates and the second #A wave content detection element 7 also operates transiently, but the undervoltage relay 11 does not operate. Therefore, the ANDN0 circuit 1 output remains "o".

Therefore, the output of the NOT circuit 8 remains at 1, and the output of the ratio differential element 6 becomes the output of the AND circuit 9 (the output of the ratio differential relay 1A). As a result, the operating time of the ratio differential relay 1^ in the event of an internal fault becomes equal to the operating time of the ratio differential element 6 (Fig. 11 63), and the pressure of the second harmonic content detection element 7 as in the conventional The time locked at (
Fig. 11 63) A ratio differential that operates faster due to the absence of a
Electric appliances can be obtained. The operation delay circuit 14 of the undervoltage relay 11 is provided to prevent the undervoltage relay 11 from outputting unnecessary output due to a drop in system voltage at the time of an internal or external fault.

FIG. 3 is a configuration diagram of another embodiment according to the present invention.
Functions that are the same as those in the figure are given the same reference numerals.

In this embodiment, a contact 16 of the transformer 2 to the power supply side breaker 4 is used instead of the output condition of the undervoltage m electric device 11 shown in FIG. Recovery delay circuit 15
is provided for the same purpose as in Figure 2.

The breaker contact 16 is a contact that closes when the power supply side breaker 48 is open, and is configured so that by connecting one side to the power supply, it becomes equivalent to the logic signal "1" when the breaker is open. be.

The operation of this embodiment is the same as that of the embodiment shown in FIG. 2 described above. When the circuit breaker 4A closes, power is turned on to the transformer 2 and an excitation inrush current is generated, but this excitation current is reliably prevented from malfunctioning as in the past, and when an internal fault is detected, the second A differential relay that is not affected by the harmonic content detection element 7 and has a quick operating time can be provided.

FIG. 4 is a block diagram of still another embodiment of the present invention.

In this embodiment, the output from the undervoltage relay is used to control the ratio differential element output, and the reference numerals in the figure correspond to those in FIGS. 2 and 3.

17 is an 807 circuit, 18 is an AND circuit that takes a logical product of the NO'r circuit 17 and the ratio differential element 6, 19 is a delay circuit connected to the ratio differential element, and 20 is an AND circuit 18
and the delay circuit 19; 21 is the second OR circuit;
807 circuit connected to harmonic content detection element, 10 is O
This is an AND circuit that inputs the R circuit 20 and the NOT times FRt21 and calculates a logical product. The other configurations are the same as in FIG. 9.

Next, the operation of the embodiment will be explained.

The operation of the ratio differential element 6 and the second harmonic content detection element 7 is the same as in the prior art.

When no power is applied to the transformer 2, the undervoltage relay 11 is activated and the NOT times IY of the ratio differential relay 1A
A "1" signal is input to 817. This signal is NOT
Qlj1?417l and 1? ,AND 1m]Route 18
Heha comes in as an "o" signal. In this state, transformer 2
When the power is turned on, an excitation inrush current flows, the ratio differential element 6 operates, and the second harmonic content detection element 7 operates. The output of the ratio differential element 6 is introduced into the t8 harmonic operation delay circuit 19 together with the output of the second harmonic content rate detection element 7, and is also introduced into the AND circuit 18.
The circuit 18 receives the r
Since it is introduced only for the time determined by , it does not appear as output. Therefore, the output of the operation delay circuit 19 becomes the output of the OR circuit 20, and is introduced into the AND circuit 1%10.

As a result, when the excitation inrush current flows, the response is the same as that of the conventional ratio differential relay 1 shown in FIG. 10, and malfunction of the ratio differential relay 1A can be reliably prevented.

When the undervoltage relay 11 is restored after a time determined by the restoration delay circuit 15 (longer than the time for the excitation inrush current to decay) after power is turned on to the transformer 2, the output of the NOT circuit 17 becomes "1".
'', when an internal fault occurs after the undervoltage relay 11 is restored, the ratio differential element 6 operates and its output is introduced to the operation delay circuit 19 and to the ND circuit 18. At this time, since the output of the NOT circuit 17 is [1], the AND circuit 18 outputs the output and introduces it into the output circuit 20.

The OR circuit 20 outputs the output when the ratio differential element 6 operates regardless of the presence or absence of the output of the operation delay circuit 19, and performs an AND operation.
is introduced into the circuit 10. At the time of an internal accident, the second harmonic content detection element 7 is not operating, and the output of the NOT circuit 21 is "
1'', the AND circuit 10 outputs, and the ratio differential relay 18 outputs. As a result, in the case of an internal fault in which the second harmonic current does not flow and the second harmonic content detection element 7 does not operate, the operation is faster by the time of the operation delay circuit 19 than the operation time of the conventional ratio differential relay. You can get a.

The operation delay circuit 14 of the undervoltage relay 11 is provided to prevent the undervoltage relay 11 from outputting unnecessary output due to a drop in system voltage during an internal or external accident.

FIG. 5 is a block diagram of still another embodiment.

In this embodiment, instead of the output condition of the undervoltage relay 11,
This uses the contact 23 of the power supply side breaker 4^ of the transformer 2, and includes an operation delay circuit 14, lfi delay circuit 15
is provided for the same purpose as in Figure 2.

The contact 23 of the circuit breaker is a contact that closes when the circuit breaker 4A on the power supply side is open, and is configured so that by connecting one side to the power supply, it becomes equivalent to the logic signal "1" when the circuit breaker is open. As mentioned above,

The operation of this embodiment is the same as that of the embodiment shown in FIG. 2 described above. When the breaker 4^ closes, the power is turned on to the transformer 2 and an excitation inrush current is generated, or malfunctions are reliably prevented in the same way as in the conventional case against this excitation inrush current, and when an internal fault is detected. A ratio differential relay that is not affected by the operation delay circuit 19 and has a fast operation time can be obtained.

[Effects of the Invention] As explained above, according to the present invention, the differential relay device is provided with an element or condition for detecting whether or not power is applied to the transformer, and the response of the element is When power is not applied to the transformer, the second harmonic content detection element is utilized, and the second harmonic content detection element is locked after a certain period of time after power is applied to the transformer. With this configuration, malfunctions are reliably prevented against the excitation inrush current that occurs when the power is turned on to the transformer, and second harmonic content is prevented against internal accidents that occur after a certain period of time after the power is turned on. It is possible to provide a differential relay device that operates quickly and is not affected by the rate detection element output.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an example of application of the differential relay device of the present invention to a power transformer, Fig. 2 is a functional block diagram of an embodiment of the differential relay device of the present invention, and Fig. 3 is a diagram showing another embodiment of the differential relay device of the present invention. FIG. 4 and FIG. 5 are configuration diagrams of other embodiments, FIG. 6 is an example of application of a conventional differential relay device to a power transformer, and FIG. 7 is a ratio difference diagram. Dynamic element ratio characteristic diagram, Figure 8 is a second harmonic lock characteristic diagram, Figure 9 is a configuration example diagram of a conventional ratio differential relay, Figure 10.11
The figure is a time chart diagram of a ratio differential relay. 1.18... Ratio differential relay 2... Power transformer 3... Main current transformer 4A,
4B... Breaker 5.12... Input transformer 6
... Ratio differential element 7 ... Second harmonic content detection element 8 , 9 , 10.17.18.20.21 ... Logic circuit 11 ... Undervoltage relay 13 ... Undervoltage Detection elements 14, 15. 19...Delay circuits 16, 23...Next point of breaker 22...System power supply Figure 1 Patent source Toshiba Corporation Patent attorney Norio Ishii Figure 2 Figure Figure Figure Figure 9 Figure 10

Claims (2)

[Claims] (1) Input the amount of electricity corresponding to the current flowing through each terminal of the transformer, and select the differential element that outputs when the amount of differential obtained from the amount of electricity input to each terminal is greater than a predetermined value, and the input amount of electricity. In a differential relay device having a second harmonic content detection element that locks the output of the differential element when the ratio of the second harmonic component to the included fundamental wave component exceeds a predetermined value, the transformer A differential coupling characterized in that an element for detecting no-voltage of the terminal voltage is added, and the output of the second harmonic content detection element is locked after a certain period of time on the condition that the no-voltage detection element is restored. Electrical equipment. (2) A differential element that inputs the amount of electricity corresponding to the current flowing through each terminal of the transformer and outputs when the amount of differential obtained from the amount of electricity input to each terminal is greater than or equal to a predetermined value; a delay circuit that delays the operation for a certain period of time after operation; and a second delay circuit that locks the output of the delay circuit when the ratio of the second harmonic component to the fundamental wave component included in the input electricity amount exceeds a predetermined value. In a differential relay device having a harmonic content detection element output, an element for detecting no-voltage of the transformer terminal voltage is added, and the delay circuit is bypassed on the condition that the no-voltage detection element is restored. A differential relay device characterized by: