JPH0347050B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a protective relay that protects a power system.

[Conventional technology]

FIG. 1 is a block diagram showing a signal input section of a conventional protective relay, FIG. 2 is a block diagram of a power system, and FIG. 3 is a block diagram showing a determination section of a conventional protective relay. 1 to 1-n are transformers (n=1, 2...) that convert the current flowing through the power supply lines S-1 to S-n connected to the bus B within the protection range C of the power system into voltage; 2-1 to 2-n are transformers 3-1 to 3- that convert the current flowing through the load-side lines l-1 to l-n connected to the bus line B into voltage;
n, 4-1 to 4-n are transformers 1-1 to 1-n, 2
-1 to 2-n filters connected to the output terminals, 5
-1 to 5-n, 6-1a to 6-na and 6-1b
~6-nb is filter 3-1~3-n, 4-1~
Sample and hold the output of 4-n.
Hold circuit, 7 is sample/hold circuit 5-
1-5-n, 6-1a-6-na, 6-1b-6
8 is a converter that converts the output of multiplexer 7 from analog to digital; 9 is the current data given by the output of converter 8 (power supply side current I〓 _P1 ~ I〓 _Po ，
A first arithmetic circuit 10-1 to 10-n determines whether a system fault has occurred within the protection range C based on the load side current I〓 _L1 ~ I〓 _Lo ), and 10-1 to 10-n are the converter 8 Current data given by the output (I〓 _L1 ~ I〓 _Lo )
A second arithmetic circuit 11 determines whether a system accident has occurred outside the protection range C based on the OR of the outputs (judgment results) of the second arithmetic circuits 10-1 to 10-n. The OR circuit 12 is an AND circuit that ANDs the output (judgment result) of the first arithmetic circuit 9 and the inverted output of the OR circuit 11. Next, the operation will be explained. First, power supply side current I〓 _P1 ~ I〓 _Po and load side current I〓 _L1
−
I〓 _Lo is the transformer 1-1~1-n, 2-1~
After being input to 2-n and converted into voltage, it is passed through filters 3-1 to 3-n, 4-1 to 4-n to sample/hold circuits 5-1 to 5-n, 6-1a to
6-Input to na. However, the sample/hold circuits 6-1b to 6-nb include filters 4-1 to 6-nb.
It is input without going through 4-n. The multiplexer 7 then samples and hold circuits 5-1 to 5-1.
5-n, 6-1a to 6-na, 6-1b to 6-nb
Each voltage (current data) input to is sequentially outputted to the analog-to-digital converter 8, and converted into a digital value by the analog-to-digital converter 8. Next, _the first _arithmetic circuit 9 receives current data (load _side current _{I〓 L
1}
~I〓 _Lo current data is sample-and-hold circuit 6
-1a to 6-na) is input,
The second arithmetic circuits 13-1 to 13-n receive current data ( _sample / _hold circuit 6
-1b to 6-nb) are input. Here, the first arithmetic circuit 9 determines whether or not the following arithmetic expression holds true, and if the formula holds true, it determines that a system accident has occurred within the protected range C. (I〓 _P1 +...+I〓 _Po +I〓 _L1 +...I〓 _Lo ) ² −K ₁ × (I〓 _P1 ² , ..., I〓 _Po ² ) max＞K ₂ ...(1) K ₁ , K ₂ are constants, and the second term means to select the largest one among (I〓 _P1 ² , ..., I〓 _Po ² ). Further, the second arithmetic circuits 10-1 to 10-n are
It is determined whether the following arithmetic expression holds true, and if the formula holds true, it is determined that a system accident has occurred outside the protected range C. I〓 _L1 ² > K ₃₁ ... (2-1) I〓 _Lo ² > K _3o ... (2-n) K ₃₁ to _{K 3o} are constants. Next, the OR circuit 11 takes the OR of each output of the second arithmetic circuits 10-1 to 10-n, and the AND circuit 12 takes the AND of the output of the first arithmetic circuit 9 and the inverted output of the OR circuit 11. and outputs the result to a circuit breaker, etc. (protector). That is, the first arithmetic circuit 9
has determined that a system fault has occurred within the protected range C, and any of the second arithmetic circuits 10-1 to 10-n has determined that a system fault has not occurred outside the protected range C. In this case, the AND circuit 12 outputs a signal to operate a system disconnector or the like. Here, the reason why the judgment results of the second arithmetic circuits 10-1 to 10-n are added to the judgment results of the first arithmetic circuit 9 is that if no system accident occurs inside or outside the protected range C, or In the case of a system accident outside the protection range C, the first term of the judgment formula (1) will normally be zero according to Kirchhop's law, so the judgment formula (1) will not hold (if the accident occurs in the protection range C) Even if there is a system fault outside the protection range C (for example, the fault at point F in Figure 2), a large current flows through the current transformer related to fault F. The current transformer becomes saturated, and the first term of judgment formula (1) can no longer be made zero with the current given from such a current transformer, and judgment formula (1) is not satisfied. (Even though it is a system accident outside the protection range C, it is determined that the accident occurred within the protection range C.) In order to deal with such a case, the second arithmetic circuit 10 -1~10
-n judgment results are added. In addition, in order to reliably eliminate the above-mentioned inconvenience, it is necessary to use the second arithmetic circuits 10-1 to 1 based on the determination result of the first arithmetic circuit 9.
Since it is necessary to first output the determination result of 0-n to the AND circuit 12, the load side current I〓 _L1 to I〓 _Lo inputted by the first arithmetic circuit 9 passes through the filters 4-1 to 4-n. It is assumed that the second arithmetic circuits 10-1 to 10
−n inputs load side current I〓 _L1 ~I〓 _Lo is filter 4
-1 to 4-n (delays caused by filters 4-1 to 4-n are taken into consideration).

[Problem to be solved by the invention]

Conventional protective relays are configured as described above, so it is necessary to obtain the load-side current that has passed through the filter and the load-side current that has not passed through the filter, and the circuit becomes more complex as the number of input points increases. There were issues such as: This invention was made in order to solve the above-mentioned problems, and it is an object of the present invention to provide a protective relay that eliminates the need for load-side current that does not pass through a filter and that does not make the circuit configuration complicated even when the number of input points increases. With the goal.

【Example】

An embodiment of the present invention will be described below with reference to the drawings. FIG. 4 is a block diagram showing a signal input section of a protective relay according to an embodiment of the present invention, and FIG. 5 is a block diagram showing a determination section of a protective relay according to an embodiment of the present invention. The same reference numerals indicate the same or corresponding parts, and the explanation will be omitted. 13-13n is a terminal that determines whether a system fault has occurred outside the protection range C based on the current data (load side current _I〓L1 to _I〓Lo ) given by the output of the converter 8. The calculation circuits 14 and 15 of No. 2 count the number of times that the calculation result of judgment formula (1) is satisfied in the calculation circuit 9, and confirm that the calculation result (system status) continues, that is, the calculation circuit 9 confirms that the calculation result (system status) is continuous. An accident occurred;
The output is output only when the number of times that the judgment formula (1) is satisfied continues n _times , and the output is returned only when the accident is removed and the number of times that the judgment formula (1) is not satisfied continues _n times. A verification circuit (in this embodiment, the judgment result of the first arithmetic circuit 9 is transferred to the _second arithmetic circuit 13 _to Logic circuits 11, 12, 14, 15, 17-1 ~ later than the determination result of 13n
It also serves as a delay circuit for input to 17-n. ), 17-1 to 17-n are arithmetic circuits 1
An AND circuit that takes AND between the outputs of 3-1 to 13-n and the matching circuit 15, where 11, 12, 1
5, 17-1 to 17-n, the first arithmetic circuit 9 determines that a system fault has occurred within the protection range C, and the second arithmetic circuit 13-13n has a fault outside the protection range C. Constructs a logic circuit that outputs a signal to operate a system protector (such as a power cutter) in order to eliminate a system fault within the protected range C when it is determined that no system fault has occurred. ing. 16 is a verification circuit. Next, the operation will be explained. First arithmetic circuit 9 and second arithmetic circuit 13-1
The process of inputting current data to ~13-n is the same as the conventional one (however, the process of inputting current data to the second arithmetic circuit 13-n
Since the load side currents I〓 _L1 to I〓 _Lo that have passed through the filters 4-1 to 4-n are input to -1 to 13-n, their explanation will be omitted. First, the operation of the second arithmetic circuits 13-1 to 13-n determines whether the following arithmetic formula holds true or not, and if the formula holds true, it is determined that a system accident has occurred outside the protection range C. It is determined that K ₁・I〓 _L1 ² ＞K ₃₁ ...(3-1) K _o・I〓 _Lo ² >K _3o ...(3-n) Here, K ₁ and _Ko are corrections for the transformation ratio of the transformer The coefficients K ₃₁ and K _3o are values that include a margin in the rated current of the load current I〓 _L1 ~ I〓 _Lo , and are approximately 1.5 to 2 of the rated current.
It's double. Also, this judgment formula (3-1) to (3-
n) is K ₁・I〓 _L1 ² for the level value of K ₃₁ ~K _3o
〜K _o ·I〓 It is determined whether the value of _Lo ² is large or not. Therefore, in the case of a system accident within the protection target range C, the determination formula (1) of the first arithmetic circuit 9 is established, so the output of the first arithmetic circuit 9 is present, and the second arithmetic circuit 13- Judgment formula (3-1) for 1 to 13-n
Since (3-n) does not hold, the second arithmetic circuit 13
The outputs of −1 to 13-n are null, and as a result,
Since the output of the verification circuit 14 is positive and the output of the verification circuit 16 is negative, the output of the AND circuit 12 is positive, and a signal is output to operate a system disconnector or the like in order to eliminate a system fault. On the other hand, protection scope C
In the case of an accident other than the above, the determination formula (1) of the first arithmetic circuit 9 does not hold, so the first arithmetic circuit 9 has no output, and the second arithmetic circuits 13-1 to 13-n
Since the determination formulas (3-1) to (3-n) hold true, the outputs of the second arithmetic circuits 13-1 to 13-n are positive, and as a result, the output of the matching circuit 14 is negative.
Since the output of the verification circuit 16 is positive, the output of the AND circuit 12 is negative, and no signal for operating the circuit breaker or the like is output. Furthermore, even in the case of an accident outside the protected range C, if the current transformer involved in the accident is saturated, the output of the arithmetic circuit 9, which should originally have no output, becomes active, but the second arithmetic circuit 13- 1-13-n
Since the determination formulas (3-1) to (3-n) hold true, the outputs of the second arithmetic circuits 13-1 to 13-n are positive, and as a result, the output of the matching circuit 14 is positive,
Since the output of the verification circuit 16 is also positive, the output of the AND circuit 12 is negative, and unnecessary operations such as a circuit breaker are prevented. Here, the number of times of verification by the verification circuit 14 is
Needless to say, this number is greater than the number of verifications of 5.16. In the above embodiment, the coefficient of the determination formula is a constant, but it may be changed depending on the number of times the verification circuit is used.

【Effect of the invention】

As described above, according to the present invention, the first arithmetic circuit is connected between the first arithmetic circuit and the logic circuit, and the determination result of the first arithmetic circuit is transmitted to the logic circuit later than the determination result of the second arithmetic circuit. Since a delay circuit for input is provided, there is no need for load-side current that does not pass through the filter, so even if the number of input points increases, the circuit configuration does not become complicated, and the circuit can be made at a lower cost.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the signal input section of a conventional protective relay, Fig. 2 is a block diagram of a power system, Fig. 3 is a block diagram showing a judgment section of a conventional protective relay, and Fig. 4 is a block diagram showing the signal input section of a conventional protective relay. FIG. 5 is a block diagram showing a signal input section of a protective relay according to an embodiment of the present invention, and FIG. 5 is a block diagram showing a determination section of a protective relay according to an embodiment of the present invention. 9 is a first arithmetic circuit, 13-1 to 13-n are second arithmetic circuits, 11, 12, 17-1 to 17-n
is a logic circuit, and 14 and 15 are matching circuits (delay circuits).
In addition, in the figures, the same reference numerals indicate the same parts.

Claims (1)

[Claims] 1. A first arithmetic circuit that determines whether a system fault has occurred within the protection range of the power system based on each current flowing through the power supply side line and load side line connected to the bus within the protection area of the power system. and a second arithmetic circuit that determines whether a grid fault has occurred outside the protection range based on the current flowing in the load-side line; When it is determined that an accident has occurred, and it is determined that a system accident has not occurred in the second arithmetic circuit outside its protected range,
a logic circuit that outputs a signal to operate a system protector in order to eliminate a system accident within the protection target range; and a logic circuit that is connected between the first arithmetic circuit and the logic circuit; and a delay circuit for inputting the determination result to the logic circuit later than the determination result of the second arithmetic circuit.