JP2009207335A - Current differential guard relay - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten the operation time without causing operation reliability to be reduced. <P>SOLUTION: A first restricting current portion 16 generates a first restricting current Ires1 by the sum of actual values of self end currents I1, I2 and an actual value of an opposite end current Ir. A second restricting current portion 17 generates a second restricting current Ires2 by the sum of the actual values of the self end currents I1, I2 and either an actual value of the opposite end current Ir or the actual value of a current obtained, by multiplying the opposite end current Ir by K times (a real number satisfying K>1). In the second restricting current portion 17, when there is no output from a first ratio differential operation result of the opposite-end side transmitted from the opposite end side, a value obtained by multiplying the opposite end current Ir by K times is selected as an input signal; and when there is an output from the first ratio differential operation result, the actual value of the opposite end current is selected as the input signal, and when there is an output from among a second ratio differential operation result of the self end side, a relay action signal to a circuit breaker provided in a bus connecting line, is generated and outputted. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a current differential protection relay of a power transmission line that protects a power transmission line from a bus of a substation configured in a 1.5CB system, and in particular, by a counterpart substation and a carrier signal. The present invention relates to a current differential protection relay that differentially protects a current flowing in a transmission line by transmitting and receiving each other.

  1.5CB system that installs two or three circuit breakers in the bus connection line between two buses and connects the power transmission line between each circuit breaker in one of the bus configurations in the power plant or substation Bus configuration (hereinafter referred to as 1.5CB bus configuration). For the protection of transmission lines with 1.5 CB bus configuration, the current obtained from the current transformer installed in the bus connection path and the current transformer installed in the bus line of the substation at the opposite end of the transmission line are used. A current differential protection relay that outputs a relay operation signal that trips the circuit breaker based on the obtained current is used.

  For example, the conventional current differential protection relay is similar to the current obtained from each current transformer installed in the bus connection path sandwiching the transmission line in the 1.5CB bus configuration and the bus of the substation opposite to the transmission line. The differential protection calculation is executed using the opposite-end current obtained by synthesizing the currents obtained from the current transformers installed in, and the calculation result is output as a relay operation signal.

  More specifically, the conventional current differential protection relay is obtained from each current obtained from the two current transformers installed on the bus connecting line to which the current differential relay is connected and the received current at the opposite end. While calculating the effective value of the sum of the instantaneous values of the three currents with the current (hereinafter referred to as the effective value of the instantaneous value sum (the effective value of the vector sum)) and the effective value of each of the three currents Then, a suppression operation for obtaining a sum of these effective values (hereinafter referred to as an effective value sum (scalar sum of effective values)) is performed. In addition, the conventional current differential protection relay performs the ratio differential calculation using the effective value of the instantaneous value sum and the RMS value sum and transmits the ratio differential calculation result to the current differential protection relay on the opposite end side. The current differential protection relay that receives this ratio differential calculation result generates a relay operation signal for controlling the circuit breaker based on its ratio differential calculation result and the received ratio differential calculation result. Output.

  Since the conventional current differential protection relay is configured as described above, for example, a power line external failure occurs on the bus, and the bus is connected to one of the two current transformers connected to the bus. Even when a current difference flows due to the saturation of the current transformer caused by the concentration of the current flowing through the connection line and the current flowing from the opposite end via the transmission line, the suppression current is input to the current differential protection relay 3 Since the current value from the two current transformers (currents from the two current transformers on the bus connection path where they are placed and the current from the current differential protection relay at the opposite end) is calculated, the suppression current is secured. This makes it possible to prevent malfunctions at its own end.

  On the other hand, the received current at the opposite end is a combined current including saturation of the current transformer, and receives the opposite end current equal to the difference current. Although there is a possibility, an unnecessary output of the relay operation signal is prevented by taking a logical product of the ratio differential calculation result of the own end and the ratio differential calculation result received from the opposite end. (For example, refer to Patent Document 1).

JP-A-1-227617

  The conventional current differential protection relay as described above requires a ratio differential calculation result on the opposite end side when outputting a relay operation signal. For example, when an internal failure of a transmission line system occurs, a failure occurs. There is a problem that the operation time from the detection of the signal until the relay operation signal is output becomes longer by the transmission delay time for obtaining the ratio differential calculation result on the opposite end side. Note that the transmission delay time is about several ms to several tens of ms, which may be a problem as a power transmission line protection relay that requires high-speed operation.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a current differential protection relay capable of shortening the operation time without reducing the operation reliability.

  In order to solve the above-described problems and achieve the object, the current differential protection relay according to the present invention is obtained by each of the current transformers obtained from each of the current transformers installed on the bus connection line sandwiching the power transmission line in the 1.5CB bus configuration. The difference current expressed as the effective value of the vector sum of the end current and the opposite end current obtained by synthesizing the current obtained from each current transformer installed on the bus connecting line across the transmission line at the opposite end of the transmission line is A first suppression that calculates a first suppression current expressed as a scalar sum of three effective values by the difference current part to be calculated, the effective values of the respective end currents, and the effective value of the opposing end currents A first differential ratio calculation that performs a ratio differential calculation based on the current unit, the difference current, and the first suppression current, and outputs a result of the ratio differential calculation as a first ratio differential calculation result. And the first ratio differential calculation result, An output section for generating and outputting a relay operation signal for tripping a circuit breaker installed on the line connecting line, and the first differential of the opposite end side transmitted from the opposite end side. If the result of the differential differential operation is no output, a scalar sum of three effective values obtained by multiplying each effective value of each self-end current by a value obtained by multiplying the opposite-end current by a predetermined real value exceeding 1 When the first ratio differential calculation result on the opposite end side transmitted from the opposite end side has an output, each effective value of each own end current is calculated. A second suppression current unit that calculates a second suppression current expressed as a scalar sum of three effective values according to the effective value of the opposite-end current, the difference current, and the second suppression current The ratio differential calculation based on the ratio differential calculation is performed, and the result of the ratio differential calculation is the second ratio difference. A second ratio differential calculation unit that outputs as a calculation result, and the output unit outputs the relay operation signal when the second ratio differential calculation result on its own side has an output. It is characterized by.

  According to the present invention, the first suppression current unit that calculates the first suppression current expressed as a scalar sum of the three effective values based on the effective values of the respective end currents and the effective value of the opposite end current; In addition, when the first ratio differential operation result transmitted from the opposite end side is not output, each effective value of each own end current and a predetermined real value exceeding 1 in the opposite end current And a second suppression current expressed as a scalar sum of three effective values by the value multiplied by the first effective differential differential operation result on the opposite end side transmitted from the opposite end side is output. If yes, a second suppression current for calculating a second suppression current expressed as a scalar sum of three effective values based on the effective values of the self-terminal currents and the effective value of the counter-terminal currents Are provided. That is, in the second suppression current unit, when the first ratio differential operation result transmitted from the opposed end side is not output, a predetermined real value exceeding 1 is set to the opposed end current. When the multiplied signal is selected as an input signal and the first ratio differential operation result transmitted from the opposite end side is output, the opposite end current itself is selected as the input signal and Since the relay operation signal for the circuit breaker installed on the bus connecting line is output when the second ratio differential calculation result on the side is an output indicating relay ON, the relay operation signal is output even if there is no operation signal at the opposite end. Can be output, and there is an effect that it is possible to obtain a current differential protection relay that can shorten the operation time without lowering the operation reliability.

  Embodiments of a current differential protection relay according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
The current differential protection relay according to the first exemplary embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a bus configuration of a 1.5 CB bus system in which a current differential protection relay according to the present embodiment is installed. In FIG. 1, the 1.5CB bus system has a bus configuration in which three circuit breakers CB1 to CB3 are arranged on the bus connecting line connecting the A-end bus 51 and the bus 52, and the circuit breakers CB1 and CB2 The current transformer CT1 is arranged between them, the current transformer CT2 is arranged between the circuit breaker CB3 and the bus 52, and three circuit breakers are connected to the bus connecting line connecting the bus 53 and the bus 54 at the B end. CB1r to CB3r are disposed, a current transformer CT1r is disposed between the circuit breaker CB1r and the circuit breaker CB2r, a current transformer CT2r is disposed between the circuit breaker CB3r and the bus bar 54, and the circuit breaker CB2 and the circuit breaker are disposed. The power transmission line 3 is connected between the CB3 and between the circuit breaker CB2r and the circuit breaker CB3r. The current differential protection relay 1 receives the currents I1 and I2 from the current transformers CT1 and CT2. The current differential protection relay 2 has a current transformer C 1r, current from CT2r I1r, with I2r is input, and can communicate with the transmission path 4 is a current differential protection relay 1 and the current differential protection relay 2.

  The A-terminal current differential protection relay 1 includes currents I1 and I2 from the current transformers CT1 and CT2, and currents I1r and I2r obtained from the current differential protection relay 2 at the opposite end (B end) of the transmission line. Is subjected to differential protection calculation with three currents (I1r + I2r) combined (I1r + I2r) and outputs a relay operation signal for controlling the circuit breakers CB2 and CB3 to protect the transmission line 3. The current differential protection relay 2 on the B end side includes currents I1r and I2r from the current transformers CT1r and CT2r, and a current I1 obtained from the current differential protection relay 1 on the opposite end side (A end side) of the transmission line. The differential protection calculation is performed with three currents, which are the combined current I2 and the current I2, and a relay operation signal for controlling the circuit breakers CB2r and CB3r is output to protect the transmission line 3.

  When viewed from the A-terminal current differential protection relay 1, the currents I1 and I2 are self-currents, and the current Ir is a counter-current. Conversely, when viewed from the B-terminal current differential protection relay 2, the currents I1r and I2r are self-currents, and the current (I1 + I2) is a counter-end current. These current differential protection relays 1 and 2 have the same function, although the input current is different.

  Next, the function of the current differential protection relay will be described with reference to FIG. FIG. 2 is a block diagram of the configuration of the current differential protection relay according to the first embodiment. In FIG. 2, the current differential protection relay 1 includes input current conversion units 10 and 11, an input current synthesis unit 12, a synchronization delay unit 9, a reception current conversion unit 13, a counter current K multiplication unit 14, a difference current unit 15, First suppression current unit 16, second suppression current unit 17, first ratio differential calculation unit 18, second ratio differential calculation unit 19, opposed end ratio differential calculation result reception unit 20, output unit 21 And a transmission unit 23.

  The input current conversion units 10 and 11 take the currents I1 and I2 from the current transformers CT1 and CT2 into the current differential protection relay 1 and convert them into current values handled in the current differential protection relay. Specifically, the input current converters 10 and 11 capture the currents I1 and I2 and insulate them from the secondary sides of the current transformers CT1 and CT2, and remove the harmonics of the captured currents I1 and I2. The current value of I2 is converted into self-end current data of a digital signal. The synchronization delay unit 9 considers the propagation delay time of the current signal notified from the current differential protection relay 2 at the opposite end, delays the currents I1 and I2, and notifies from the current differential protection relay 2 at the opposite end. The currents I1 and I2 are converted so that the current value of the current Ir and the current values of the currents I1 and I2 become the current values at the same time.

  The input current synthesis unit 12 adds (vector addition) the respective end current data converted by the input current conversion units 10 and 11, and the added current is the combined current (the opposite end as viewed from the current differential protection relay 2 at the opposite end). Current)) to the transmitter 23. The transmission unit 23 uses the combined current combined by the input current combining unit 12 as a carrier signal, together with a ratio differential calculation result (output of the first ratio differential calculation unit 18) described later, and a current difference via the transmission line 4. Transmit to the dynamic protection relay 2.

  The reception current converter 13 receives the opposite end current Ir transmitted from the current differential protection relay 2 at the opposite end via the transmission line 4, and handles the received opposite end current Ir in the current differential protection relay 1. Convert to edge current data.

The differential current unit 15 includes time-synchronized current data of the currents I1 and I2, that is, the current data I1 and I2 converted by the input current conversion units 10 and 11, and the received current (opposing end current Ir). The output data of the synchronous delay unit 9 corrected to be the same time and the opposite end current data of the opposite end current Ir converted by the reception current conversion unit 13 are added, and the current data obtained by the addition is obtained. The effective value of the current shown (the sum of the time-synchronized self-end currents I1 and I2 and the counter-end current Ir) is obtained. Here, when the effective value calculation is expressed by “rms”, the difference current Id as the calculation result of the difference current unit 15 is expressed by the following equation.
Id = (I1 + I2 + Ir) rms (Formula 1)

The first suppression current unit 16 includes an effective value of current data representing the time-synchronized currents I1 and I2 and an effective value of current data representing the counter-current Ir converted by the reception current conversion unit 13. And the obtained effective values are added (scalar addition) to obtain the first suppression current. Here, when the effective value of the current I1 is I1rms, the effective value of the current I2 is I2rms, and the effective value of the counter-end current Ir is Ir_rms, the first suppression current Ires1 is expressed by the following equation.
Ires1 = I1rms + I2rms + Ir_rms (Formula 2)

  The opposite end ratio differential calculation result receiving unit 20 receives the first ratio differential calculation result at the opposite end transmitted by the current differential protection relay 2 at the opposite end via the transmission line 4 (the opposite end ratio differential calculation result). Receive.

  The counter-end current K multiplication unit 14 receives the counter-end ratio differential calculation result, which is an output from the counter-end ratio differential calculation result receiving unit 20, and according to whether or not the counter-end ratio differential calculation result is output. Then, the multiplication coefficient (settling value) to be multiplied by the counter-end current Ir when the input counter-end current Ir is output to the second suppression current unit 17 is changed. More specifically, when the output of the counter end ratio differential calculation result is “present”, the input counter end current Ir is multiplied by 1, that is, the counter end current Ir is directly supplied to the second suppression current unit 17. Output. On the other hand, when the output of the counter end ratio differential calculation result is “none”, the input counter end current Ir is multiplied by K and output to the second suppression current unit 17. Here, the output of the opposite end ratio differential calculation result “present” means that the first ratio differential calculation unit 18 at the opposite end transmits “logic“ 1 ”” to the transmission unit 23. The output of the opposite end ratio differential calculation result “None” means that the first ratio differential calculation unit 18 at the opposite end transmits “logic“ 0 ”” to the transmission unit 23. The multiplication coefficient K is a set value that satisfies “K ≧ 1, K is a real number”, and is set using any input means (not shown).

Here, if the effective value of the current I1 is I1rms, the effective value of the current I2 is I2rms, and the effective value of the counter-end current Ir is Ir_rms, the second suppression current Ires2 is the difference between the counter-end ratio differential calculation results. Can be expressed by the following equation.
Ires2 = I1rms + I2rms + K × Ir_rms (Formula 3)
Note that K in (Expression 3) satisfies the following condition.
(1) When the output of the opposite end ratio differential calculation result is “present”: K = 1
(2) When the output of the opposite end ratio differential calculation result is “None”: K> 1 (K is a real number)

  The first ratio differential calculation unit 18 performs the ratio differential calculation based on the difference current Id obtained by the difference current unit 15 and the first suppression current Ires1 obtained by the first suppression current unit 16. Do. The second ratio differential calculation unit 19 performs the ratio differential calculation based on the difference current Id obtained by the difference current unit 15 and the second suppression current Ires2 obtained by the second suppression current unit 17. Do.

In the first ratio differential calculation unit 18 and the second ratio differential calculation unit 19, for example, determination processing based on the following conditional expressions ((condition 1) to (condition 3)) is performed.
(Condition 1) Id ≧ K1
(Condition 2) Id ≧ R1 × Ires
(Condition 3) Id ≧ R2 × Ires + K2

  In the above conditional expression, Id is a difference current input from the difference current unit 15, and Ires is a suppression current (in the first ratio differential operation unit 18, the first current input from the first suppression current unit 16. In the second ratio differential operation unit 19, the second suppression current is input from the second suppression current unit 17, and K1, K2, R1, and R2 are set from the outside by an input means, for example. It is a settling value which shows the characteristic of ratio differential operation. These settling values K1, K2, R1, and R2 are ratio differential operations in a region where the suppression current Ires is large so that a malfunction does not occur due to an error of the current transformers CT1 and CT2 that increases when the suppression current Ires increases. It is preferable to settle so that the region becomes narrow. The set value R2 is generally set to “1” in consideration of the influence of saturation of the current transformers CT1, CT2, CT1r, and CT2r.

  The first ratio differential calculation unit 18 performs ratio differential calculation by substituting the first suppression current Ires1 for Ires in the above (condition 1) to (condition 3), and performs the above (condition 1) to (condition 3). ) Are all satisfied, the first ratio differential calculation result indicating that (all the conditional expressions are satisfied) is output, and any of the above (condition 1) to (condition 3) is not satisfied Outputs the first ratio differential calculation result indicating that (at least one conditional expression is not satisfied).

  Similarly, the second ratio differential calculation unit 19 performs ratio differential calculation by substituting the second suppression current Ires2 for Ires in the above (condition 1) to (condition 3), and the above (condition 1) to When all of (Condition 3) is satisfied, a second ratio differential calculation result indicating that (All of the conditional expressions are satisfied) is output, and any of the above (Condition 1) to (Condition 3) is output. If not satisfied, a second ratio differential operation result indicating that (at least one conditional expression is not satisfied) is output.

  The output unit 21 includes a first ratio differential calculation result obtained by the first ratio differential calculation unit 18 and a second ratio differential calculation result obtained by the second ratio differential calculation unit 19. Is output as a relay operation signal to the circuit breakers CB1 and CB2. That is, the output unit 21 uses the first suppression current Ires1 to satisfy the above (condition 1) to (condition 3), and the second suppression in which the output of the counter end ratio differential calculation result is reflected. A relay operation signal is output when the above (condition 1) to (condition 3) are satisfied using the current Ires2, and at least one of the above (condition 1) to (condition 3) using the first suppression current Ires1 When one conditional expression is not satisfied, or when at least one of the above (condition 1) to (condition 3) using the second suppression current Ires2 is not satisfied, the relay operation signal is not output.

  By the way, the above (Expression 1) to (Expression 3) represent the differential current Id, the first suppression current Ires1, and the second suppression current Ires2 in the current differential protection relay 1 on the A end side (own end side). It was a calculation formula. Next, the differential current Idr, the first suppression current Ires1r, and the second suppression current Ires2r in the current differential protection relay 2 on the B end side (opposing end side) will be clarified.

Similarly to the A-terminal difference current unit 15, the B-terminal difference current unit 15 obtains the effective value of the sum of the self-terminal current and the opposed terminal current as the difference current. Here, the respective currents at the current differential protection relay 2 are “current I1r” and “current I2r”, and the opposite-end current is “current (I1 + I2)”. Therefore, the difference current Idr calculated by the difference current unit 15 of the current differential protection relay 2 is expressed by the following equation by applying these currents (I1r, I2r, I1, I2) to the above (Equation 1). Can do.
Idr = (I1r + I2r + I1 + I2) rms (Formula 4)

Similarly, the first suppression current Ires1 obtained by the first suppression current unit 16 of the B terminal (current differential protection relay 2) is an effective value I1r_rms of the own-end current I1r, an effective value I2r_rms of the own-end current I2r, and By applying the effective value (I1 + I2) rms of the counter-end current (I1 + I2) rms to (Expression 2), it can be expressed by the following expression.
Ires1r = I1r_rms + I2r_rms + (I1 + I2) rms (Formula 5)

On the other hand, the second suppression current Ires2 obtained by the second suppression current unit 17 of the B end (current differential protection relay 2) is the second suppression current Ires2 via the counter end current K multiplication unit 14. Since it is input to the unit 17, the calculation formula is different from that of the first suppression current Ires1. Specifically, the second suppression current Ires2 is expressed by the effective value I1r_rms of the self-end current I1r, the effective value I2r_rms of the self-end current I2r, and the effective value (I1 + I2) rms of the counter-end current (I1 + I2) rms (formula 3 ) Can be expressed by the following equation.
Ires2r = I1r_rms + I2r_rms + K × (I1 + I2) rms (Formula 6)
In the above (Expression 6), when the output of the first ratio differential calculation unit at the A end (opposing end), that is, the first ratio differential calculation unit 18 of the current differential protection relay 1 is “present” As described above, when K = 1 is set for and the output of the first ratio differential calculation unit 18 is “none”, a predetermined real value satisfying K> 1 is set.

  Here, some supplementary explanations regarding the failure of the transmission line system will be given. The failure of the transmission line system includes a transmission line external failure and a transmission line internal failure. A power transmission line internal failure is a failure that occurs on a region surrounded by current transformers CT1, CT2, and current transformers CT1r, CT2r, and a power transmission line external failure is a failure that occurs on a region other than the above. Of these power transmission line failures, the failure to be detected by the current differential protection relay 1 and the current differential protection relay 2 is a power transmission line internal failure.

  Next, the operation of the current differential protection relay of the first embodiment will be described. Here, first, in the 1.5CB bus system bus configuration shown in FIG. 1, a transmission line external failure occurs in a region 60 between the current transformer CT2 and the A-end bus 52, and this transmission line external failure Therefore, the case where the current transformers CT1r and CT2r at the opposite ends and the current transformer CT1 at the opposite end are not saturated and only the current transformer CT2 at the own end is saturated will be described as an example. In this description, “R1 = 0.4” and “R2 = 1”, which are general ratio characteristics, are used as the settling values R1 and R2 of the operation area of the ratio differential characteristics.

  For convenience of explanation, it is further assumed that current I1 = current I2 = current I and current I1r = current I2r = 0. These conditions give conditions that the current differential protection relay is liable to malfunction.

When the current transformer CT2 is not saturated, the difference current Id is “0” from (Equation 1). On the other hand, when the current transformer CT2 is saturated due to an external failure of the transmission line, the difference current Id is a value different from “0” from the above (Equation 1). Here, it is assumed that the current I2 becomes 50% of the actual current (current at the normal time when no power line external failure occurs) due to saturation of the current transformer CT2. In this case, the difference current Id is noted that the directions of the currents I1 and I2 are opposite, and from the above (Equation 1),
Id = (I1 + I2 + Ir) rms
= (I−0.5 × I + 0) rms
= 0.5 × Irms (Formula 7)
It becomes.

Further, the current differential protection relay 1 becomes easier to operate when the difference current Id / suppression current Ires is larger. Therefore, assuming that the current differential protection relay 1 is most likely to operate, the effective value Ir_rms of the opposite-end current is set to “0”.
At this time, the first suppression current Ires1 is calculated from the above (Equation 2).
Ires1 = I1rms + I2rms + Ir_rms
= Irms + 0.5 × Irms + 0
= 1.5 × Irms (Formula 8)
It becomes.

  From (Equation 7) and (Equation 8) above, “difference current Id / suppression current Ires1” is “1/3”. Accordingly, when the set value R1 is set so that “R1> 1/3” holds, “difference current Id / first suppression current Ires1 <settling value R1” is satisfied, and the above (condition 2) is not satisfied. Therefore, the first ratio differential operation unit 18 indicates that the first ratio differential indicating that at least one of the above (condition 1) to (condition 3) (condition 2 in this case) is not satisfied. The calculation result is output to the transmission unit 23 and the output unit 21. Further, the first ratio differential calculation result is transmitted to the current differential protection relay 2 on the opposite end side through the transmission unit 23.

  In this way, the first ratio differential calculation result without output is input to one of the input terminals of the output unit 21. Therefore, the output unit 21 does not depend on the output result of the second ratio differential operation unit 19 and does not output a relay operation signal.

Further, the opposite-end current Ir of the current differential protection relay 1 is the sum of the self-end currents I1r and I2r viewed from the current differential protection relay 2. Therefore, the differential current of the current differential protection relay 1 shown in (Equation 1) can also be expressed by the following equation.
Id = (I1 + I2 + I1r + I2r) rms (Equation 9)

As is apparent from the comparison between (Equation 4) and (Equation 9), the difference current Idr obtained by the difference current portion 15 of the current differential protection relay 2 is obtained by the difference current portion 15 of the current differential protection relay 1. It becomes equal to the difference current Id. Therefore, the difference current portion 15 of the current differential protection relay 2 when the current I2 becomes 50% of the actual current (normal current when no external fault of the transmission line has occurred) due to the saturation of the current transformer CT2. The difference current Idr to be obtained is
Idr = Id = 0.5 × Irms (Formula 10)
It becomes.

Here, the same conditions as when (Equation 7) is obtained, that is, the conditions of I1r_rms = I2r_rms = 0 and I1 = I2 = I are used. At this time, the first suppression current Ires1r of the current differential protection relay 2 is expressed by the above (formula 9).
Ires1r = I1r_rms + I2r_rms + (I1 + I2) rms
= 0 + 0 + (I−0.5 × I) rms
= 0.5 × Irms (Formula 11)
It becomes.

Further, the second suppression current Ires2r of the current differential protection relay 2 is expressed by the above (formula 6).
Ires2r = I1r_rms + I2r_rms + K × (I1 + I2) rms
= 0 + 0 + K × (I−0.5 × I) rms
= 0.5 × K × Irms (Formula 12)
It becomes.

  Here, according to (Equation 10) and (Equation 11), in the current differential protection relay 2, the difference current Idr and the first suppression current Ires1r are equal to each other, so that “difference current Idr / first suppression current”. Ires1r = 1 ”. Therefore, in order to prevent malfunction, it is necessary to establish “differential current Idr / first suppression current Ires1r> 1”. However, in the case of an internal failure at the one-end input, “difference current Idr / first suppression current Ires1r = 1” is satisfied, so that setting is performed so that “difference current Idr / first suppression current Ires1r> 1” is satisfied. I can't. Therefore, there is a possibility that the first ratio differential calculation result (the output of the first ratio differential calculation unit 18) enters the operation area of the current differential protection relay 2 and is unnecessary detected. That is, all of the above (Condition 1) to (Condition 3) are satisfied, and there is a possibility that a signal with output is output to one input terminal of the output unit 21.

On the other hand, as described above, in the current differential protection relay 1, (Condition 2) out of the (Condition 1) to (Condition 3) is not satisfied, so the first ratio differential calculation result ( The output of the first ratio differential operation unit 18) is not output. As a result, the multiplication coefficient K in (Equation 12) is set to a real value that satisfies K> 1. Here, for example, if K = 3 is set, the above (formula 12) becomes
Ires2r = 0.5 × 3 × Irms
= 1.5 × Irms (Formula 13)
Thus, “difference current Idr / second suppression current Ires2r = 1/3”. Therefore, by setting “R1> 1/3”, at least (condition 2) of the above (condition 1) to (condition 3) can be made unsatisfied. As a result, the second ratio differential calculation result without output (the output of the second ratio differential calculation unit 19) is input to the other input terminal of the output unit 21, so that the relay operation signal is output. Therefore, malfunction can be prevented. Further, the first ratio differential operation unit 18 of the A-terminal current differential protection relay 1 is kept in an inoperative state and continues to output a signal indicating no output, so that the value of the multiplication coefficient K is maintained. The B-terminal current differential protection relay 2 does not output a relay operation signal.

  Next, in the 1.5CB bus system bus configuration shown in FIG. 1, for example, an operation when a power transmission line internal failure occurs on the current differential protection relay 1 side will be described. As the operation conditions, the same conditions as described above, that is, I1 = I2 = I, I1_rms = I2_rms = 0, “K = 3”, “R2 = 1”, and the like are used.

Under the above conditions, the difference current Id and the first suppression current Ires1 at the A terminal (current differential protection relay 1) are expressed by the following equations using the above (Equation 1) and (Equation 2), respectively.
Id = (I1 + I2 + Ir) rms
= (I + I + 0) rms
= 2 × Irms (Formula 14)
Ires1 = I1rms + I2rms + Ir_rms
= Irms + Irms + 0
= 2 × Irms (Formula 15)

  Therefore, “difference current Id / first suppression current Ires1 = 1”. In order to satisfy the above (condition 2), the settling value R1 is set so that “R1 <1” holds. As a result, the first ratio differential calculation result at the A end (current differential protection relay 1) is output.

Further, the second suppression current Ires2 of the A end (current differential protection relay 1) is expressed by the following equation by using the above (Equation 3).
Ires2 = I1rms + I2rms + 3 × Ir_rms
= (I + I + 3 × 0) rms = 2 × Irms (Expression 16)

  Therefore, “difference current Id / second suppression current Ires2 = 1”, and the second ratio differential calculation result of the current differential protection relay 1 is also the first ratio differential calculation result of the current differential protection relay 1. As with the output.

Next, consider a case where it is difficult to operate against a power line internal failure. As an example, consider the case of I1 = I2 = I1r = I2r = I. Under this condition, the difference current Id and the first suppression current Ires1 at the A terminal (current differential protection relay 1) are expressed by the following equations using the above (Equation 1) and (Equation 2), respectively. .
Id = (I1 + I2 + Ir) rms
= (I + I + I + I) rms
= 4 × Irms (Expression 17)
Ires1 = I1rms + I2rms + Ir_rms
= Irms + Irms + Irms + Irms
= 4 × Irms (Formula 18)

  Therefore, “difference current Id / first suppression current Ires1 = 1”. In order to satisfy the above (condition 2), the settling value R1 is set so that “R1 <1” holds. As a result, the first ratio differential calculation result at the A end (current differential protection relay 1) is output.

Further, the second suppression current Ires2 of the A end (current differential protection relay 1) is expressed by the following equation by using the above (Equation 3).
Ires2 = I1rms + I2rms + 3 × Ir_rms
= (1 + 1 + 3 × 2) Irms = 8 × Irms (Equation 19)

  Therefore, “difference current Id / second suppression current Ires2 = 4/8 = 1/2”. In order to satisfy the above (condition 2), it is necessary to set the settling value R1 to “R1 <1/2”. Further, as described above, in order to prevent malfunction due to saturation of the current transformer CT2 in the case of an external failure of the transmission line, it is necessary to set the settling value R1 to “R1> 1/3”. Therefore, the settling value R1 may be set (settling) to a value satisfying “1/3 <R1 <1/2” (for example, any real value from 0.35 to 0.45). By using such a set value, it is possible to detect an internal failure of the transmission line and prevent malfunction due to saturation of the current transformer CT2 due to an external failure of the transmission line. In addition, although the setting value K of the counter end current K multiplication part 14 was demonstrated here as "3", it is not restricted to this value, The value which can be operated at the time of a power transmission line internal failure was match | combined with the power transmission line system. A settling value may be adopted.

  FIG. 3 is a diagram showing the relationship between the differential differential operation area of the first ratio differential calculation unit 18 and the second ratio differential calculation unit 19 and the ratio between the differential current and the suppression current. In FIG. 3, the vertical axis indicates the difference current Id, and the horizontal axis indicates the suppression current. In addition, the slope of the line L1 indicated by a broken line indicates the ratio of “difference current Id / suppression current Ires = 1” when it is difficult to operate against a power line internal failure, and the line L2 indicated by the broken line is A ratio of “difference current Id / suppression current Ires = ½” is shown, and a line L3 indicated by a broken line shows a ratio of “difference current Id / suppression current Ires = 1/3”. A line L4 indicated by a one-dot chain line indicates the boundary value “difference current Id = setting value K” in the above (condition 1), and a line L5 indicated by the one-dot chain line indicates “setting value R1 = 0.4. ”Indicates the boundary value“ Difference current Id = Settling value R1 × Suppression current Ires ”in the above (Condition 2), and the line L6 indicated by the alternate long and short dash line indicates the above setting in the case of“ Settling value R2 = 1 ”. The boundary value of (Condition 3) “Differential current Id = Settling value R2 × Suppression current Ires + Settling value K2” is shown, and the region where all of (Condition 1) to (Condition 3) are satisfied is the current differential protection relay 1 , 2 operation area. Further, as is clear from the above description, the conditional expression of the second ratio differential operation unit 19 is (Condition 2), so that only the (Condition 2) may be configured.

  As described above, in the first embodiment, together with the first suppression current unit that generates the first suppression current by the self-end current and the counter end current, the second suppression current is generated by the self-end current and the counter end current. When the output of the ratio differential calculation result at the opposite end (first ratio differential calculation result) is not output, this counter is replaced with the opposite end current. Since the second suppression current is calculated with the input obtained by multiplying the end current by a predetermined multiplication coefficient exceeding 1, it is possible to obtain a ratio differential calculation result that is unlikely to cause an unnecessary operation with respect to a power line external failure. It becomes. In addition, when obtaining the ratio differential calculation result, it does not wait for the operation signal at the opposite end to be output as in the prior art, but instead of the ratio differential calculation result (first and second ratio differential calculations at its own end). As a result, it is possible to increase the speed by the transmission delay time.

Embodiment 2. FIG.
In the current differential protection relay according to the first embodiment, a counter-end current multiplied by a predetermined multiplication coefficient is input in accordance with the presence / absence of the output of the ratio differential calculation result of the counter end separately from the first suppression current unit. By using the second suppression current section, a ratio differential calculation result that hardly causes unnecessary operation against a power line external failure is obtained. In the first embodiment, the first ratio differential calculation result based on the output of the first suppression current unit and the second ratio differential calculation result based on the output of the second suppression current unit are output to the output unit. The relay operation signal is obtained by inputting the signal into the. On the other hand, in the configuration of the first embodiment, the magnitude of the counter-end current that is input to the second suppression current unit is changed depending on whether or not the ratio differential calculation result of the counter-end is output. When the ratio differential operation unit 2 and the first ratio differential operation unit are configured by the same conditional expression, the first ratio differential operation result at the opposite end is reflected on the input signal. Further, in the configuration of the first embodiment, when the output of the differential differential calculation result at the opposite end is “present”, the determination processing of the first suppression current unit and the second suppression current unit is the same result. Become. For this reason, in the configuration of the first embodiment, it is possible to obtain the same effect as that of the first embodiment without using the first ratio differential calculation result for the output of the relay operation signal. A current differential protection relay 1a shown in FIG. 4 is configured based on such a technical idea.

  In FIG. 4, the current differential protection relay 1a has only the output of the second ratio differential operation unit 19 as the input of the output unit 21 of the current differential protection relay 1 of the first embodiment shown in FIG. The difference is that is used. In addition, the same code | symbol is attached | subjected to the component which has the same function as the current differential protection relay 1 of Embodiment 1 shown in previous FIG. 2, and the overlapping description is abbreviate | omitted.

  According to the current differential protection relay according to the second embodiment, when the ratio differential calculation result is obtained, instead of waiting for the operation signal at the opposite end to be output and outputting the ratio differential calculation result, Since the operation can be performed with the output of the operation results (first and second ratio differential operation results), the speed can be increased by the transmission delay time compared to the conventional case. Further, according to the second embodiment, in comparison with the first embodiment, it is not necessary to provide the output unit 21 with a logic circuit such as an AND circuit, so that the configuration can be simplified.

  As described above, the current differential protection relay according to the present invention is useful for protecting a transmission line having a 1.5CB bus configuration, and is particularly suitable for a system that requires a high-speed relay output.

It is a figure which shows the bus-bar structure of the 1.5CB bus-bar system in which the current differential protection relay concerning Embodiment 1 is installed. 1 is a block diagram showing a configuration of a current differential protection relay according to a first exemplary embodiment. It is a figure which shows the relationship of the ratio of the operation area | region of the ratio differential calculation of the 1st ratio differential calculation part 18 and the 2nd ratio differential calculation part 19, and a differential current and a suppression current. FIG. 6 is a block diagram illustrating a configuration of a current differential protection relay according to a second exemplary embodiment.

Explanation of symbols

1, 1a, 1b, 2 Current differential protection relay 3 Transmission line 4 Transmission path 9 Synchronization delay unit 10, 11 Input current conversion unit 12 Input current synthesis unit 13 Reception current conversion unit 14 Opposite end current K multiplication unit 15 Difference current unit 16 1st suppression current part 17 2nd suppression current part 18 1st ratio differential calculation part 19 2nd ratio differential calculation part 20 opposing edge ratio differential calculation result receiving part 21 output part (AND condition)
21a Output unit 23 Transmitter unit 51, 52, 53, 54 Bus CB1, CB2, CB3, CB1r, CB2r, CB3r Breaker CT1, CT2, CT1r, CT2r Current transformer

Claims (2)

Each self-current obtained from each current transformer installed in the bus connection line sandwiching the transmission line in the 1.5CB bus configuration, and each current transformer installed in the bus connection line sandwiching the transmission line at the opposite end of the transmission line A counter current obtained by combining the currents obtained from the above, a difference current part for calculating a difference current expressed as an effective value of a vector sum of the current, an effective value of each of the self-currents, and an effective value of the counter-current A first suppression current unit that calculates a first suppression current expressed as a scalar sum of three effective values according to, and a differential ratio calculation based on the difference current and the first suppression current, A first ratio differential calculation unit that outputs a result of the ratio differential calculation as a first ratio differential calculation result; and a circuit breaker installed on the bus connecting line based on the first ratio differential calculation result Output unit that generates and outputs a relay operation signal that trips In current differential protection relay equipped with,
When the first ratio differential operation result transmitted from the opposite end side is not output, each effective value of each own end current and a predetermined actual value exceeding 1 for the opposite end current are obtained. A second suppression current expressed as a scalar sum of three effective values by a value multiplied by a numerical value is calculated, and the first ratio differential calculation result on the opposite end side transmitted from the opposite end side is calculated. When there is an output, a second suppression current is calculated for calculating a second suppression current expressed as a scalar sum of three effective values based on the effective values of the respective end currents and the effective value of the opposite end current. A current section;
A second differential ratio calculation unit that performs a differential ratio calculation based on the difference current and the second suppression current, and outputs a result of the differential ratio calculation as a second differential ratio calculation result;
With
The output section outputs the relay operation signal when the second ratio differential calculation result on the end side has an output. Each self-current obtained from each current transformer installed in the bus connection line sandwiching the transmission line in the 1.5CB bus configuration, and each current transformer installed in the bus connection line sandwiching the transmission line at the opposite end of the transmission line A counter current obtained by combining the currents obtained from the above, a difference current part for calculating a difference current expressed as an effective value of a vector sum of the current, an effective value of each of the self-currents, and an effective value of the counter-current A first suppression current unit that calculates a first suppression current expressed as a scalar sum of three effective values according to, and a differential ratio calculation based on the difference current and the first suppression current, A first ratio differential calculation unit that outputs a result of the ratio differential calculation as a first ratio differential calculation result; and a circuit breaker installed on the bus connecting line based on the first ratio differential calculation result Output unit that generates and outputs a relay operation signal that trips In current differential protection relay equipped with,
When the first ratio differential operation result transmitted from the opposite end side is not output, each effective value of each own end current and a predetermined actual value exceeding 1 for the opposite end current are obtained. A second suppression current expressed as a scalar sum of three effective values by a value multiplied by a numerical value is calculated, and the first ratio differential calculation result on the opposite end side transmitted from the opposite end side is calculated. When there is an output, a second suppression current is calculated for calculating a second suppression current expressed as a scalar sum of three effective values based on the effective values of the respective end currents and the effective value of the opposite end current. A current section;
A second differential ratio calculation unit that performs a differential ratio calculation based on the difference current and the second suppression current, and outputs a result of the differential ratio calculation as a second differential ratio calculation result;
With
The output unit outputs the relay operation signal when the first ratio differential calculation result on the own end side has an output and the second ratio differential calculation result on the own end side has an output. Current actuated protection relay, characterized in that

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