JP5279282B2 - PCM current differential protection relay - Google Patents

Abstract

The invention discloses a PCM current differential protection relay, equipped with a mechanism which can detect the situation and control without misoperation under the condition that even the relay can not identify the switch and the transmission relay time of the duplex transmission line switch changes sharply. A resetting processing part (20), according to the judgment of the establishment of three conditions that a current change detecting part (17) shows no change of a home terminal current data, a difference current detecting part (19) detects a difference current exceeding a adjustment value and a phase different detecting part (18) determines that the home terminal current data of the present time and a period before is out of step, provides operation instruction to a synchronous processing part (14) and a ratio differential operation part (15). The synchronous processing part (14) receives the operation instruction and resets the time synchronization of the home terminal current data, and the ratio differential operation part (15) terminates the operation processing, stores and outputs the operation results in the period before obtaining accurate synchronization.

Description

  The present invention relates to a PCM current differential protection relay that uses a PCM (Pulse Code Modulation) signal transmission path existing between both ends to perform transmission line protection in a protection section of a power system.

  In power transmission line protection of a power system, a PCM current differential protection relay is disposed at each end of the protection section (an electric station such as a substation). Each PCM current differential protection relay samples the transmission line current at its own terminal at a constant cycle, and transmits the obtained data of its own terminal to and from the other end using a PCM signal transmission line. Then, the differential differential calculation using the data of the own end and the other end is executed, and the presence / absence of a transmission line failure in the protection section is determined. When each PCM current differential protection relay detects a power transmission line failure in the protection section, the PCM current differential protection relay trips the circuit breaker on its own end and disconnects the power transmission line in the protection section from the power system. The transmission lines in the section are protected.

  Incidentally, since generation of transmission errors is inevitable in the PCM signal transmission line connecting the PCM current differential protection relays at both ends, as a measure for improving the reliability of power transmission line protection, for example, in Patent Document 1, the PCM signal transmission line is used. When the PCM current differential protection relay detects a disturbance in the received signal and switches the transmission path to the normal side, it switches to the other end that sent it, instead of switching only at its own end that detected the disturbance. A PCM signal transmission path switching method has been proposed in which both ends select the transmission path of the same path by sending a command and switching the other end.

  For example, Patent Document 2 proposes a method of switching by providing two systems of the above-mentioned PCM signal transmission path. In Patent Document 2, a case where only one route is operated is considered. More specifically, in the operation period of only one of the routes, it is unavoidable that the reliability is unavoidable, and each of the two transmission lines is constituted by a main transmission line and a sub-transmission line. Then, each transmission side signal is branched and transmitted to the main transmission line and the sub transmission line. In addition, the receiver side is equipped with a circuit that corrects and adjusts so that there is no difference in the propagation delay time, clock phase, and frame phase between the main transmission line and the sub-transmission line, and the transmission line can be switched without any change in delay time or frame phase. To realize.

JP-A-5-236635 (paragraphs “0017” and “0019”) JP-A-5-103415 (FIG. 1, paragraph “0012”)

  However, in the conventional switching method of the PCM signal transmission path, the PCM current differential protection relay has a configuration in which the transmission path switching circuit is built in, resulting in an increase in the cost of the PCM current differential protection relay.

  Therefore, in order to reduce costs, the PCM signal transmission path switching method for connecting between the PCM current differential protection relays at both ends is arranged in such a way that the PCM current differential protection relays at each end of the protection section are arranged in close proximity. Consider a method realized by a configuration in which two multiplex communication devices capable of handling general communication between electrical stations are connected via a transmission line switching circuit. In this configuration, the two multiplexing communication devices control the transmission line switching circuit.

  In the case of this configuration, when the cause of switching from one of the two transmission paths to the other is a transmission abnormality that has occurred in the communication channel for the PCM current differential protection relay, the PCM current differential protection relay uses the transmission abnormality. Therefore, it is possible to cope with a change in transmission line delay time due to transmission line switching in advance. However, when the cause of switching from one of the two transmission paths to the other is a transmission abnormality occurring in a communication channel other than the communication channel for the PCM current differential protection relay, the PCM current differential protection relay transmits the transmission. Since the abnormality cannot be recognized, it is impossible to cope with transmission line switching in advance. In other words, the PCM current differential protection relay has a problem that time synchronization of current data between both ends may be lost due to a change in transmission delay time that occurs unexpectedly and suddenly.

  In the PCM current differential protection relay, the time synchronization determination of the current data between both ends is normally repeated at a frequency of once every several cycles. Therefore, the time synchronization of the current data is performed for the worst number of 10 ms. Transmission line protection will be continued without recognizing any deviation. In this case, depending on the magnitude of the load current and the degree of sudden change in the transmission delay time, the result of the ratio differential calculation may erroneously indicate the protection section abnormality, and an unnecessary operation may be performed, and the reliability of the transmission line protection is impaired. There is a fear.

  The present invention has been made in view of the above, and a PCM current differential protection relay that can be controlled so as not to malfunction even when a duplex transmission path is switched due to a switching cause that cannot be recognized on the relay side. The purpose is to obtain.

  In order to achieve the above-described object, the present invention is arranged at each end of the protection section, and a current data generating unit that samples the current of the transmission line at its own end at a certain period to generate its own end current data; A transmission processing unit that puts the self-end current data on a predetermined transmission frame and sends it to one or the other of the duplex transmission lines, and a self-end generated by the current data generation part in the other end current data received from the transmission line A power transmission line in a protection section that performs a ratio differential operation using a synchronization processing unit that outputs current data in time synchronization, and the other end current data and local current data that has been subjected to time synchronization processing by the synchronization processing unit. In a PCM current differential protection relay comprising a ratio differential operation unit for determining the presence or absence of a failure, it detects a loss of time synchronization due to a change in transmission delay time that occurs when the duplex transmission path is switched. A control signal that generates a signal for controlling both the synchronization processing unit and the ratio differential operation unit or the ratio differential operation unit until time synchronization is completed on the transmission path in which the synchronization processing unit is switched. A generation unit is provided.

  According to the present invention, even when the duplex transmission path is switched due to a switching cause that cannot be recognized in advance on the relay side, it can be detected and controlled so as not to malfunction, and the protection section using the duplex transmission path can be controlled. There is an effect that a PCM current differential protection relay capable of performing transmission line protection with high reliability can be realized.

  Exemplary embodiments of a PCM current differential protection relay according to the present invention will be described below in detail with reference to the drawings.

  First, in order to facilitate understanding of the present invention, referring to FIGS. 1 to 3, the transmission path configuration between PCM current differential protection relays employed in the present invention and the current transmitted and received between both ends of the protection section The time synchronization process using data will be described.

  FIG. 1 is a system diagram illustrating a transmission path configuration between PCM current differential protection relays applied to the present invention. As shown in FIG. 1, when a protection section is provided between the electric stations A and B, a PCM current differential protection relay (PCM relay) 30 is disposed in the electric station A, and the electric station B includes A PCM current differential protection relay (PCM relay) 35 is arranged.

  Then, a switching circuit 31 is provided for the PCM relay 30 disposed at the electric station A. Connected to the switching circuit 31 are two multiplexed communication devices (MUX) 32 and 33 that are arranged in the same electric station A and are used for communication with the electric station B. Control of the switching circuit 31 is performed by the MUXs 32 and 33.

  Similarly, a switching circuit 36 is provided for the PCM relay 35 disposed at the electric station B. Connected to the switching circuit 36 are two multiplexed communication devices (MUX) 37 and 38 that are arranged in the same electric station B and are used for communication with the electric station A. The MUXs 37 and 38 control the switching circuit 36.

  That is, between the PCM relay 30 arranged at the electric station A and the PCM relay 35 arranged at the electric station B, a multiplex transmission path connecting the MUX 32 and the MUX 37, and a multiplex transmission connecting the MUX 33 and the MUX 38. Duplex with road.

  In this configuration, the transmission path between the PCM relay and the switching circuit is configured by one line, but the transmission path between the MUXs is configured by a duplex transmission path. Since the PCM relay and the MUX are arranged at the same electric station, the transmission path length is short, and it is considered that the occurrence of disturbances causing a transmission error is extremely small. On the other hand, since the transmission line between MUXs straddles between electric stations, it is a long-distance transmission line of, for example, several tens of kilometers or more, and it can be said that there is a high possibility that a disturbance causing a transmission error occurs.

The multiplex transmission lines between the MUXs 32 and 37 and between the MUXs 33 and 38 are independent and independent transmission lines, and the transmission delay times in the multiplex transmission lines are almost always different.
In other words, if the transmission delay time in the multiplex transmission path between the MUXs 32 and 37 is t1, and the transmission delay time in the multiplex transmission path between the MUXs 33 and 38 is t2, then t1 ≠ t2 between them. There is a relationship.

  Therefore, for example, when operating using a multiplex transmission path between the MUXs 32 and 37, one or both of the MUXs 32 and 37 detect the occurrence of an abnormality such as a transmission error, and go to the multiplex transmission path between the MUXs 33 and 38. When the switching is performed, the transmission delay time in the PCM relays 30 and 35 changes suddenly. Since the PCM relays 30 and 35 may not be able to detect in advance transmission path switching, current data may be out of time synchronization. This will be specifically described with reference to FIGS.

  FIG. 2 is a diagram for explaining the relationship between current data transmitted and received before transmission path switching and transmission delay time in the transmission path configuration shown in FIG. FIG. 3 is a diagram for explaining the relationship between current data transmitted and received after switching the transmission line and transmission delay time in the transmission line configuration shown in FIG.

  2 and 3, counterpart end transmission current data I1 (t) to I1 (t-11) arranged in the vertical direction on the left end side are PCM relays (hereinafter referred to as “one PCM relay”) arranged at one electrical station. Current data sampled at regular intervals and the self-end current data I2 (t) to I2 (t-11) arranged in the vertical direction on the right end side are PCM relays arranged at the other electric station. (Hereinafter referred to as “the other PCM relay”) current data sampled at regular intervals, and each sampled at the same time.

  In FIG. 2 and FIG. 3, when the other PCM relay synchronizes its own time, the current data (mating end transmission current data) transmitted by the other PCM relay is the transmission delay. Since the received current data I1 ′ (t) to I1 ′ (t−8) are received after the elapse of time t1 and t2, one PCM relay is selected from the current data at its own end in the other PCM relay. The state of selecting current data that synchronizes time with current data (received current data) obtained from is shown.

  When operation is performed using multiple transmission paths between the MUXs 32 and 37 and the transmission path is not switched, as shown in FIG. 2, the other PCM relay has its own current data I2 (t-3 ) Is selected as current data that is time-synchronized with the received current data I1 ′ (t) from one of the PCM relays that has arrived after the lapse of the transmission delay time t1.

  In this state, when the transmission path is switched to the multiple transmission path between the MUXs 33 and 38, as shown in FIG. 3, the received current data I1 ′ (t) from the one PCM relay is changed to the MUX 33, It is received after the elapse of the transmission delay time t2 in the multiplex transmission line between 38. Therefore, in the other PCM relay, the current data to be selected as the time synchronization data at its own end is actually the current data I2 (t-6). The above is the same when one PCM relay performs time synchronization with the current data of the other PCM relay.

  However, the PCM relays 30 and 35 usually perform processing for compensating for the delay time of the transmission line and synchronizing the current data at its own end with the received current data at the other end at a fixed time interval of several tens of ms or more. Therefore, as described above, even if the delay time of the current data at the other end changes suddenly, it cannot immediately follow the sudden change in the transmission delay.

  Therefore, in the above example, the other PCM relay is set to the current data I2 (t-3) before switching within a period of several tens of ms or more until the time synchronization processing is completed. In the previous incorrect time synchronization state. Then, as a result of performing the differential ratio calculation, there is a possibility of malfunction due to generation of an erroneous difference current. In this case, since the synchronization of the sample timing does not change in the PCM relays 30 and 35 at both ends even when the transmission path is switched, the time length of time synchronization loss caused by the switching corresponds to a time width that is an integral multiple of the transmission frame. Become length. The time width of one transmission frame is a time corresponding to one sampling interval or an integral multiple thereof (that is, within one cycle).

  Therefore, according to the present invention, in the transmission line configuration shown in FIG. 1, the PCM relays 30 and 35 at both ends switch the duplex transmission line due to a switching cause that the multiplex communication devices 32, 33, 37, and 38 cannot recognize on the relay side. When a sudden change occurs in the transmission delay time as a result of performing the above, a control signal generation unit is provided that recognizes the change and generates a signal that controls the malfunction so as not to malfunction with respect to the sudden change in the transmission delay time. I did it. Since this control signal generation unit can be configured in various modes, it will be individually described as an embodiment.

Embodiment 1 FIG.
FIG. 4 is a block diagram showing a configuration of a PCM current differential protection relay including a control signal generation unit (part 1) according to Embodiment 1 of the present invention.

  In FIG. 4, at the corresponding end of the transmission line 1 in the protection section, a current transformer (CT) 2 for taking out the current of the transmission line 1 is used, and although not shown, the transmission line 1 is used to disconnect from the system. It is equipped with a circuit breaker.

  The PCM current differential protection relays 3a disposed at both ends of the protection section include a current data generation unit 11, a transmission processing unit 12, a current data reception processing unit 13, a synchronization processing unit 14, a ratio differential calculation unit 15, and In addition to the output processing unit 16, the control signal generation unit 5a includes a current change detection unit 17, a phase difference detection unit 18, which is a synchronization presence / absence confirmation unit, a difference current detection unit 19, and a reset processing unit 20.

  The current data generation unit 11 samples the current of the transmission line 1 taken out by the CT 2 at a sampling interval synchronized between both ends, and generates its own end current data.

  The transmission processing unit 12 converts the current data at one sampling interval generated by the current data generation unit 11 or current data synchronized at an integer multiple of the sampling interval into a PCM signal, and converts it into one transmission frame. The data is sent to the multiplexed communication device placed on the terminal. For ease of understanding, a description will be given assuming that one sampling interval = 1 transmission frame, that is, a configuration in which current data is transmitted at each sampling interval.

  The current data reception processing unit 13 converts the PCM signal transmitted from the partner relay received from the multiplexing communication device arranged at its own end into appropriate current data.

  When the “operation command” is not input from the reset processing unit 20, the synchronization processing unit 14 measures the delay time of the current data of the counterpart terminal received by the current data reception processing unit 13, and only the amount of the delay time By delaying the sequence number (frame number) of the local current data generated by the current data generation unit 11 and setting the frame number (synchronization frame) used for time synchronization, the local time synchronized with the counterpart current data Processing for obtaining current data is performed, and the self-current data subjected to the time synchronization processing is output together with the counterpart current data.

  The ratio differential calculation unit 15 uses the other end current data and the own end current data synchronized with the time, which are input from the synchronization processing unit 14 when the “operation command” is not input from the reset processing unit 20. The ratio differential calculation is performed to determine the failure of the transmission line 1. The determination result is given as a relay output from the output processing unit 16 to a circuit breaker (not shown) equipped in the power transmission line 1.

  In the control signal generation unit 5a, the following processing operation is performed. The current change detection unit 17 detects whether or not the self-end current data generated by the current data generation unit 11 has changed, and outputs the detection result to the reset processing unit 20.

  The phase difference detection unit 18 confirms whether or not the self-end current data time-synchronized with the other-end current data is present one cycle before the present time of the self-end current data subjected to the time synchronization processing by the synchronization processing unit 14. The synchronization processing unit 14 performs this by detecting the phase difference between the self-end current data and the counterpart end current data that are synchronized in time. When the detected phase difference is a phase difference corresponding to an integral multiple of the transmission frame, that is, the other end current data and time are one cycle before the current end current data. When there is synchronized self-end current data, it is determined that the time synchronization is lost due to a sudden change in the transmission line delay time due to the switching of the duplex transmission line, and the determination signal of the time synchronization loss is sent to the reset processing unit 20. Output.

  The difference current detection unit 19 calculates a difference current from each current data of the own end and the other end with which the synchronization processing unit 14 is synchronized in time, and when the calculated difference current is equal to or larger than a certain set value, a detection signal Is output to the reset processing unit 20. The end of the detection signal is when the calculated difference current is below a certain settling value.

  The reset processing unit 20 is mainly configured with an AND circuit, and the current change detection unit 17 does not detect a current change at its own end, and the phase difference detection unit 18 detects a phase difference that is an integral multiple of the transmission frame. When the three conditions of detecting and the difference current detection unit 19 detecting the difference current exceeding the set value are satisfied, it is determined that the time synchronization loss due to the transmission path switching has occurred, and the ratio with the synchronization processing unit 14 The “operation command” is output to the differential operation unit 15.

  In the “operation command” that the reset processing unit 20 gives to the synchronization processing unit 14, the start time when the three conditions are satisfied is important. Therefore, the “operation command” output from the resetting processing unit 20 is a start pulse signal with a short pulse width that indicates when three conditions are satisfied.

  That is, the synchronization processing unit 14 responds to the “operation command” from the resetting processing unit 20, that is, in response to the start time when the three conditions are satisfied, the self-end current having previously synchronized with time. The time synchronization process for finding a new frame number for time synchronization by shifting the frame number of the data is started and the frame number is reset. Note that the pulse width of the start instruction pulse signal having a short pulse width output from the reset processing unit 20 is a time width required for resetting the frame number.

  Further, when the ratio differential calculation unit 15 receives the “operation command” from the reset processing unit 20, that is, when the notification of the start time when the three conditions are satisfied, the ratio differential calculation unit 15 stops the dynamic calculation processing and immediately before The calculation result is held and output, and is continued for a period until the “operation command” from the reset processing unit 20 indicates the end time.

  When the resetting in the synchronization processing unit 14 is completed, time synchronization is established in the switched transmission line, so that the ratio differential calculation unit 15 includes the self-end current data and the other end current that are correctly time-synchronized. Data will be input.

  Then, when the above three conditions are not satisfied, the resetting processing unit 20 outputs an “operation command” indicating the end time to the ratio differential calculation unit 15. When the “operation command” from the reset processing unit 20 indicates the end time, the ratio differential calculation unit 15 resumes a new ratio differential calculation process using the self-terminal current data that is correctly synchronized.

  As described above, in the first embodiment, when there is no change in the current data detected at its own end, when a difference current exceeding the set value occurs, the cause is the switching of the duplex transmission path. If there is a sudden change in the transmission delay time resulting from this, only a sudden phase change occurs in the current data at the other end, and the phase difference between the current data at the other end and the current data at the other end is an integral multiple of the transmission frame. We focused on the fact that the electrical angle is equivalent to. In other words, it recognizes that the switching of the transmission path has been performed by the establishment of these three conditions, resets the frame number for time synchronization of the self-end current data, and within the period until it can be reset By stopping the dynamic calculation process and holding and outputting the immediately previous calculation result, malfunction within the period until it can be reset is prevented. Then, after the resetting, the transmission line protection is continued by performing the ratio differential calculation using the self-current data that is time-synchronized correctly. As a result, it is possible to realize a highly reliable PCM current differential protection relay that does not cause a malfunction even when switching of the duplex transmission path is performed for a reason that cannot be recognized in advance.

Embodiment 2. FIG.
FIG. 5 is a block diagram showing a configuration of a PCM current differential protection relay including a control signal generation unit (part 2) according to Embodiment 2 of the present invention. In FIG. 5, the same reference numerals are given to the same or equivalent components as those shown in FIG. 4 (Embodiment 1). Here, the description will be focused on the portion related to the second embodiment.

  As shown in FIG. 5, in the PCM current differential protection relay 3b according to the second embodiment, in the configuration shown in FIG. 4 (first embodiment), the control signal generating unit 5b is replaced with the control signal generating unit 5a. Is provided. In the control signal generation unit 5b, the self-end current data to the phase difference detection unit 18 is changed from the self-end current data after the time synchronization process to the self-end current data before the time synchronization process. This is due to the fact that the self-end current data has a phase difference equivalent to an integral multiple of the transmission frame before and after time synchronization.

  That is, the phase difference detection unit 18 may detect whether or not the phase difference between the partner end current data and the own end current data before synchronization is a phase difference corresponding to an integral multiple of the transmission frame. The same operations and effects as those of Form 1 can be obtained.

Embodiment 3 FIG.
FIG. 6 is a block diagram showing a configuration of a PCM current differential protection relay including a control signal generation unit (part 3) according to Embodiment 3 of the present invention. In FIG. 6, the same or similar components as those shown in FIG. 4 (Embodiment 1) are denoted by the same reference numerals. Here, the description will be focused on the portion related to the third embodiment.

  As shown in FIG. 6, in the PCM current differential protection relay 3c according to the third embodiment, in the configuration shown in FIG. 4 (first embodiment), the control signal generation unit 5c is replaced with the control signal generation unit 5a. Is provided. In the control signal generation unit 5 c, an effective value ratio calculation unit 21 is provided instead of the phase difference detection unit 18.

  The effective value ratio calculation unit 21 calculates the effective value of the difference current exceeding the set value detected by the differential current detection unit 19 and the effective value of the other end current data output from the synchronization processing unit 14, respectively. When the ratio is a value corresponding to an integral multiple of the transmission frame, it is determined that the time synchronization is lost due to a sudden change in the transmission line delay time due to the switching of the duplex transmission line, and the determination signal for the time synchronization loss is reset. To the unit 20.

  The cause of the difference current due to the sudden change in the transmission delay time is due to the sudden change in the phase of the received current data at the other end, so the phase difference with the other end current data before and after the occurrence of the difference current corresponds to an integral multiple of the transmission frame. By determining whether or not the phase difference is a difference, it is also possible to determine a time synchronization loss due to a sudden change in transmission delay time due to switching of the duplex transmission path. This is a matter corresponding to claim 5.

  In this case, FIG. 7 is a vector diagram showing the relationship between the other end current and the difference current before and after switching. As shown in FIG. 7, before the occurrence of the differential current c exceeding the set value, that is, the counterpart terminal current a before the transmission line switching, and after the occurrence of the differential current c exceeding the set value, that is, the counterpart terminal current after the transmission line switching. b is only the phase change amount θ, and the amplitude is the same without change. Therefore, the phase difference θ corresponding to an integral multiple of the transmission frame can be measured based on the ratio between the effective value of the generated difference current c and the effective value of the counterpart end current a (b). This is a matter corresponding to claim 6.

That is, if the effective value of the difference current is Id and the effective value of the counterpart current is I, when the phase change amount θ is 180 ° or less,
Id / (2 · I) = sin (θ / 2) (1)
Since the phase change amount θ can be expressed as
θ = 2 · Sin ⁻¹ {(Id / (2 · I)} (2)
Can be calculated. If the electrical angle corresponding to one transmission frame is φ, the detection condition in the effective value ratio calculation unit 21 is that the phase change amount θ obtained by the equation (2) is an integral multiple of the electrical angle φ.

  FIG. 8 is a diagram for explaining the operation of the effective value ratio calculation unit shown in FIG. Although FIG. 8 shows the case of φ = 30 °, the effective value ratio calculation unit 21 applies each value of the effective value ratio Id / I to the equation (2) as shown in FIG. θ is calculated, and when it is an integral multiple of the electrical angle φ, the determination signal is output.

  As described above, in the third embodiment, the same operation and effect as in the first embodiment can be obtained only when the transmission delay difference between the duplex transmission lines is found to be 180 ° or less in electrical angle. Since the multiple (θ / φ) can be replaced with the relationship of the effective value ratio Id / I, there is an advantage that it is not necessary to directly perform the phase calculation and the processing is simplified.

Embodiment 4 FIG.
FIG. 9 is a block diagram showing a configuration of a PCM current differential protection relay including a control signal generation unit (part 4) according to Embodiment 4 of the present invention. In FIG. 9, the same or similar components as those shown in FIG. 4 (Embodiment 1) are denoted by the same reference numerals. Here, the description will be focused on the portion related to the fourth embodiment.

  As shown in FIG. 9, in the PCM current differential protection relay 3d according to the fourth embodiment, in the configuration shown in FIG. 4 (first embodiment), the control signal generating unit 5d is replaced with the control signal generating unit 5a. Is provided. In the control signal generation unit 5d, a reset processing unit 22 is provided instead of the phase difference detection unit 18 and the reset processing unit 20. The reset processing unit 22 includes an AND circuit 22a and a zero difference current selection unit 22b.

  The AND circuit 22a generates a time synchronization loss due to transmission line switching when the current change detection unit 17 detects a difference current exceeding the set value when the current change detection unit 17 does not detect a change in its own terminal current data. An AND condition for determining is satisfied, and a condition satisfaction signal is supplied to the zero difference current selection unit 22b. The end of the condition satisfaction signal is after the time required for resetting the frame number in the normal transmission synchronization processing in the synchronization processing unit 14 after the signal is output.

  When the condition establishment signal is input from the AND circuit 22a, the zero difference current selection unit 22b outputs an “operation command” to the ratio differential calculation unit 15 and, for example, the following procedures (1) and (2) Then, the synchronization processing unit 14 sequentially determines whether or not to select the own terminal current data that minimizes the difference current with the other end current data from the own end current data output in one cycle. The frame number of the selected self-end current data is set in the synchronization processing unit 14.

  When the “operation command” is input from the zero difference current selection unit 22b, the ratio differential calculation unit 15 stops the calculation process and starts holding and outputting the previous calculation result.

  The synchronization processing unit 14 starts the time synchronization process using the newly set frame number.

  The ratio differential calculation unit 15 resumes the calculation process using the self-end current data output from the synchronization processing unit 14 and time-synchronized correctly.

  The processing of the zero difference current selection unit 22b will be specifically described with reference to FIGS. Before the transmission line switching, as shown in FIG. 2, in the synchronization processing unit 14, the received current data I ′ (t) is time-synchronized with the local current data I (t−3) from the other end. is there. In this case, it is assumed that the current change detection unit 17 does not detect the change of the self-end current data, and the difference current detection unit 19 detects the difference current exceeding the set value. The synchronization processing unit 14 continues to execute the previous time synchronization process regardless of them.

(1) When it is known that the transmission delay time increases due to the switching of the duplex transmission path, the zero difference current selector 22b calculates the difference current δ between the received current data from the other end and the own end current data. The frame number of the self-end current data is changed from “I1 ′ (t) + I2 (t−3) = δ0” → “I1 ′ (t) + I2 (t−4) = δ1” → “I1 ′ (t) + I2 ( t−5) = δ2 ”→“ I1 ′ (t) + I2 (t−6) = δ3 ”→“ I1 ′ (t) + I2 (t−7) = δ4 ”and shift toward the past number. While calculating. Then, since a point where the difference current δ gradually decreases and increases is found, the frame number that should synchronize the frame number of the minimum difference current (δ3 is the minimum difference current in FIG. 3) at the turning point. Is set in the synchronization processing unit 14 as follows.

(2) If it is unclear whether the transmission delay time increases or decreases due to the switching of the duplex transmission path, the zero-difference current selection unit 22b sets the frame number of the local current data to “I1 ′ (t) + I2”. (T−3) = δ0 ”→“ I1 ′ (t) + I2 (t−2) = δ−1 ”→“ I1 ′ (t) + I2 (t−1) = δ−2 ”→“ I1 ′ (t ) + I2 (t) = δ−3 ”→“ I1 ′ (t) + I2 (t−4) = δ1 ”→“ I1 ′ (t) + I2 (t−5) = δ2 ”→“ I1 ′ (t) + I2 (T−6) = δ3 ”→“ I1 ′ (t) + I2 (t−7) = δ4 ”and the like, it is also necessary to check the frame number that has advanced from the frame number used for time synchronization before switching. However, the subsequent confirmation can be omitted by increasing the δ value. In the example of FIG. 3, since it increases at δ−1, each process of “I1 ′ (t) + I2 (t−1) = δ−2” and “I1 ′ (t) + I2 (t) = δ−3”. Can be omitted.

  As described above, according to the fourth embodiment, in addition to obtaining the same operation and effect as those of the first embodiment, the process of sequentially confirming the frame number of the own-end current data that minimizes the difference current is performed. Therefore, although there is a drawback that the processing amount becomes large, since the difference current is directly measured, the accuracy of time synchronization can be improved.

Embodiment 5 FIG.
FIG. 10 is a block diagram showing a configuration of a PCM current differential protection relay including a control signal generation unit (part 5) according to Embodiment 5 of the present invention. In FIG. 10, the same reference numerals are assigned to the same or equivalent components as those shown in FIG. 4 (Embodiment 1). Here, the description will be focused on the portion related to the fifth embodiment.

  As shown in FIG. 10, in the PCM current differential protection relay 3e according to the fifth embodiment, in the configuration shown in FIG. 4 (first embodiment), the control signal generating unit 5e is replaced with the control signal generating unit 5a. Is provided. In the control signal generator 5e, an effective value change detector 24 and a reset processor 25 are provided instead of the phase difference detector 18 and the reset processor 20.

  The effective value change detection unit 24 detects whether or not there is a change in the effective value of the counterpart current data output from the synchronization processing unit 14, and outputs the detection result to the reset processing unit 25.

  The reset processing unit 25 includes an AND circuit, and when the current change detection unit 17 does not detect a change in its own end current data, the effective value change detection unit 24 does not detect a change in the effective value of the other end current data. However, when the three conditions of the difference current detection unit 19 detecting the difference current exceeding the set value are satisfied, it is determined that the time synchronization is lost due to the transmission path switching, and the “operation command” is set to the ratio difference. The result is output to the dynamic calculation unit 15. The reason why the “operation command” is not output to the synchronization processing unit 14 is that the frame number of the time-synchronized self-current data in the synchronization processing unit 14 is not confirmed in the present example. This is because the time synchronization cannot be reset. In the present example, the three conditions are not satisfied when the difference current detector 19 detects a difference current equal to or less than a set value.

  The reset processing unit 25 outputs the “operation command” output to the ratio differential calculation unit 15 as a start instruction pulse signal having a short pulse width indicating that the three conditions are satisfied, as in the reset processing unit 20. To do. The pulse width of the start instruction pulse signal having a short pulse width is a time width required for the synchronization processing unit 14 to reset the correct frame number.

The ratio differential calculation unit 15 has a configuration that performs one of the following two processes.
(1) When the ratio differential calculation unit 15 is configured to perform calculation processing with a ratio set value corresponding to a difference current equal to or smaller than the set value set in the difference current detection unit 19, the reset processing unit 25 When the “operation command” is input, that is, when the notification of the start time when the above three conditions are satisfied is received, the calculation process is stopped, and the previous calculation result is held and output. This continues for the period until the “operation command” indicates the end time. When the “operation command” indicating the end time is input, since the synchronization processing unit 14 is performing the correct time synchronization processing, the ratio differential calculation unit 15 can resume the calculation processing.

(2) When the ratio differential calculation unit 15 is configured to perform calculation processing with the first ratio set value corresponding to the difference current equal to or less than the set value set in the difference current detection unit 19, the transmission delay time If the second ratio set value is set to a value large enough not to respond to the difference current due to the difference between the two, and the notification of the start time when the above three conditions are satisfied is received from the reset processing unit 25, The ratio set value is changed from the first ratio set value to the second ratio set value without stopping the process, and is continued for a period until the “operation command” from the reset processing unit 25 indicates the end time. To do. When the “operation command” indicating the end time is input, the ratio set value is returned again from the second ratio set value to the first ratio set value, and the calculation process is resumed.

  As described above, in the fifth embodiment, the difference current is generated in the state where there is no power transmission line failure only when the duplex transmission path is switched. In this case, the effective value of the other end current data is obtained. Focusing on the fact that there is no change, instead of detecting the phase difference between the other end current data and the own end current data, the change in the effective value of the other end current data is detected. If a difference current is detected in a state where there is no change in the effective value of the end current data, it is determined that the time synchronization is lost due to transmission path switching. The time synchronization cannot be reset because the frame number of the self-current current data synchronized with the time cannot be determined, but the ratio differential calculation is stopped for the time necessary for the time synchronization processing and the previous calculation result is held. Alternatively, control is performed to automatically increase the ratio set value so that it does not operate with a difference current due to a change in transmission delay time, so that malfunction can be prevented with simple processing.

Embodiment 6 FIG.
FIG. 11 is a block diagram showing a configuration of a PCM current differential protection relay including a control signal generation unit (part 6) according to Embodiment 6 of the present invention. In FIG. 11, the same reference numerals are given to components that are the same as or equivalent to those shown in FIG. 4 (Embodiment 1). Here, the description will be focused on the portion related to the sixth embodiment.

  As shown in FIG. 11, in the PCM current differential protection relay 3f according to the sixth embodiment, in the configuration shown in FIG. I have. The settling value memory 27 stores in advance a settling value for the amount of time synchronization deviation calculated as follows.

When the difference between the transmission delay time during operation and the transmission delay time after switching is known in advance, if the transmission delay time difference is Δt and the transmission frame time is t1, the time synchronization deviation after switching The quantity D is as follows:
When 0 <Δt ≦ t1, D = 0 or 1
When t1 <Δt ≦ 2 · t1, D = 1 or 2
In the case of 2 · t1 <Δt ≦ 3 · t1, D = 2 or 3
In the case of 3 · t1 <Δt ≦ 4 · t1, D = 3 or 4
And thereafter take the same form.

And if it changes to shorten the transmission delay time,
When -t1 <Δt ≦ 0, D = 0 or −1
−2 · t1 <Δt ≦ −t1, D = −1 or −2
In the case of −3 · t1 <Δt ≦ −2 · t1, D = 2 or 3
And thereafter take the same form.

  In this way, when the amount of change in the transmission delay time due to the switching of the duplex transmission path is known, the frame number used for synchronization in the own end current data from the predicted phase change amount of the other end current data due to the transmission path switching. Therefore, if a settling value for the amount of deviation of the synchronization frame is prepared in advance, the synchronization processing unit 26 does not agree with the amount of change in the frame number of the local current data when the synchronization is reset. Therefore, it becomes possible to perform time synchronization processing with higher accuracy, and the reliability of power transmission line protection can be further improved.

  In the sixth embodiment, the application example to the first embodiment has been described. Needless to say, the sixth embodiment can be similarly applied to the second to fourth embodiments.

  As described above, the PCM current differential protection relay according to the present invention provides highly reliable protection of power transmission lines using a duplex transmission path that may be switched due to a switching cause that cannot be recognized on the relay side. Useful to do.

It is a system figure explaining the transmission line structure between the PCM current differential protection relays employ | adopted by this invention. It is a figure explaining the relationship between the current data transmitted / received before transmission line switching in the transmission line structure shown in FIG. 1, and transmission delay time. It is a figure explaining the relationship between the current data and transmission delay time which are transmitted / received after transmission line switching in the transmission line structure shown in FIG. It is a block diagram which shows the structure of the PCM current differential protection relay provided with the control signal generation part (the 1) by Embodiment 1 of this invention. It is a block diagram which shows the structure of the PCM current differential protection relay provided with the control signal generation part (the 2) by Embodiment 2 of this invention. It is a block diagram which shows the structure of the PCM current differential protection relay provided with the control signal generation part (the 3) by Embodiment 3 of this invention. It is a vector diagram which shows the relationship between the other end electric current before and behind switching, and a difference current. It is a figure explaining operation | movement of the effective value ratio calculating part shown in FIG. It is a block diagram which shows the structure of the PCM current differential protection relay provided with the control mechanism at the time of the transmission line switching by the Embodiment 4 of this invention (the 4). It is a block diagram which shows the structure of the PCM current differential protection relay provided with the control-signal production | generation part (the 5) by Embodiment 5 of this invention. It is a block diagram which shows the structure of the PCM current differential protection relay provided with the control signal generation part (the 6) by Embodiment 6 of this invention.

Explanation of symbols

1 Transmission line at one end of protected section 2 Current transformer (CT)
3a, 3b, 3c, 3d, 3e, 3f PCM current differential protection relay 5a, 5b, 5c, 5d, 5e Control signal generation unit 11 Current data generation unit 12 Transmission processing unit 13 Current data reception processing unit 14, 26 Synchronization processing Unit 15 Ratio differential operation unit 16 Output processing unit 17 Current change detection unit 18 Phase difference detection unit 19 Difference current detection unit 20, 22, 25 Reset processing unit 21 RMS value calculation unit 22a AND circuit 22b Zero difference current selection Unit 24 RMS value change detection unit 27 Setting value memory 30, 35 PCM current differential protection relay (PCM relay)
31, 36 Switching circuit 32, 37 Multiplexing communication device (MUX) forming one multiplexed transmission line
33, 38 Multiplexed communication device (MUX) that forms the other multiple transmission path
A, B Electricity stations at both ends of the protection section

Claims (8)

A current data generation unit that is arranged at each end of the protection section and samples the current of the transmission line at its own end in a certain cycle to generate its own end current data, and the self end current data is placed on a predetermined transmission frame A transmission processing unit for sending to one or the other of the duplex transmission line, and a synchronization processing unit for outputting the current data generated by the current data generation unit in time synchronization with the counterpart current data received from the transmission line; A ratio differential calculation unit that performs a ratio differential calculation using the counterpart terminal current data and the local terminal current data that has been time-synchronized by the synchronization processing unit to determine the presence or absence of a power line failure in the protection section. In PCM current differential protection relay,
The synchronization process is performed until the time synchronization process is detected on the transmission path in which the synchronization processing unit is switched by detecting a time synchronization loss due to a change in transmission delay time that occurs when the duplex transmission path is switched. A control signal generation unit that generates a signal for controlling both the ratio differential calculation unit and the ratio differential calculation unit,
With
The control signal generator is
A current change detection unit for detecting whether or not there is a change in the self-end current data generated by the current data generation unit;
A difference current detection unit for detecting whether or not a difference current between the other end current data and the own end current data subjected to time synchronization processing by the synchronization processing unit exceeds a settling value;
A synchronization presence / absence confirmation unit that confirms whether or not there is self-current data that is time-synchronized one cycle before the present time of the self-current data that has been subjected to time synchronization processing by the synchronization processing unit;
The current change detection unit detects that there is no change in the self-end current data, the difference current detection unit detects a difference current exceeding a set value, and the synchronization presence / absence check unit includes time-synchronized self-end current data. A reset processing unit that outputs an operation command for resetting to the synchronization processing unit and the ratio differential operation unit,
The synchronization processing unit receives the operation command and executes the time synchronization process again, and the ratio differential operation unit stops the operation processing upon receiving the operation command and holds and outputs the previous calculation result. , Restarting the arithmetic processing in response to the end of the operation command,
P CM current differential protection relay you, characterized in that. The synchronization presence / absence confirmation unit detects the presence of the self-end current data synchronized in time by detecting the phase difference between the counterpart end current data and the self-end current data subjected to time synchronization processing by the synchronization processing unit. 2. The PCM current differential protection relay according to claim 1 , wherein the PCM current differential protection relay is a phase difference detection unit configured to determine the out of time synchronization when the phase difference is a phase difference corresponding to an integral multiple of the transmission frame. The synchronization presence / absence confirmation unit confirms the existence of the self-end current data synchronized in time by detecting the phase difference between the counterpart end current data and the self-end current data generated by the current data generation unit. 2. The PCM current differential protection relay according to claim 1 , wherein the PCM current differential protection relay is a phase difference detection unit configured to determine the out of time synchronization when the phase difference is a phase difference corresponding to an integral multiple of the transmission frame. The synchronization presence / absence confirmation unit confirms the presence of time-synchronized self-end current data by detecting a phase difference of the counterpart end current data before and after the difference current detection unit detects a difference current exceeding the set value. 2. The PCM current differential according to claim 1 , wherein the PCM current differential is a phase difference detection unit configured to determine the out of time synchronization when the detected phase difference is a phase difference corresponding to an integral multiple of the transmission frame. Protection relay. The phase difference detection unit is configured to perform the time synchronization when a ratio between an effective value of the counterpart terminal current data and an effective value of the difference current detected by the difference current detection unit is a phase difference corresponding to an integral multiple of the transmission frame. The PCM current differential protection relay according to claim 4 , wherein determination of disconnection is performed. A current data generation unit that is arranged at each end of the protection section and samples the current of the transmission line at its own end in a certain cycle to generate its own end current data, and the self end current data is placed on a predetermined transmission frame A transmission processing unit for sending to one or the other of the duplex transmission line, and a synchronization processing unit for outputting the current data generated by the current data generation unit in time synchronization with the counterpart current data received from the transmission line; A ratio differential calculation unit that performs a ratio differential calculation using the counterpart terminal current data and the local terminal current data that has been time-synchronized by the synchronization processing unit to determine the presence or absence of a power line failure in the protection section. In PCM current differential protection relay,
The synchronization process is performed until the time synchronization process is detected on the transmission path in which the synchronization processing unit is switched by detecting a time synchronization loss due to a change in transmission delay time that occurs when the duplex transmission path is switched. A control signal generation unit that generates a signal for controlling both the ratio differential calculation unit and the ratio differential calculation unit,
With
The control signal generator is
A current change detection unit for detecting whether or not there is a change in the self-end current data generated by the current data generation unit;
A difference current detection unit for detecting whether or not a difference current between the other end current data and the own end current data subjected to time synchronization processing by the synchronization processing unit exceeds a settling value;
When the current change detection unit outputs no change in its own-end current data, and the difference current detection unit detects a difference current exceeding a set value, a reset operation command is output to the differential ratio calculation unit In addition, the frame number of the self-end current data in which the difference current with the counterpart end current data selected from the self-end current data output from the synchronization processing unit during one cycle becomes near zero is used for time synchronization. A reset processing unit that sets the frame number in the synchronization processing unit,
The synchronization processing unit executes the time synchronization processing based on the set end-of-frame current data of the frame field, and the ratio differential operation unit stops the operation processing in response to the operation command and performs the immediately preceding operation. The result is held and output, and the arithmetic processing is resumed in response to the end of the operation command.
P CM current differential protection relay you, characterized in that. A current data generation unit that is arranged at each end of the protection section and samples the current of the transmission line at its own end in a certain cycle to generate its own end current data, and the self end current data is placed on a predetermined transmission frame A transmission processing unit for sending to one or the other of the duplex transmission line, and a synchronization processing unit for outputting the current data generated by the current data generation unit in time synchronization with the counterpart current data received from the transmission line; A ratio differential calculation unit that performs a ratio differential calculation using the counterpart terminal current data and the local terminal current data that has been time-synchronized by the synchronization processing unit to determine the presence or absence of a power line failure in the protection section. In PCM current differential protection relay,
The synchronization process is performed until the time synchronization process is detected on the transmission path in which the synchronization processing unit is switched by detecting a time synchronization loss due to a change in transmission delay time that occurs when the duplex transmission path is switched. A control signal generation unit that generates a signal for controlling both the ratio differential calculation unit and the ratio differential calculation unit,
With
The control signal generator is
A current change detection unit for detecting whether or not there is a change in the self-end current data generated by the current data generation unit;
A difference current detection unit that detects whether or not a difference current between the other end current data and the own end current data that has been synchronously processed by the synchronization processing unit exceeds a settling value;
An effective value change detecting unit for detecting whether or not there is a change in the effective value of the counterpart terminal current data;
The current change detection unit outputs no change in its own terminal current data, the difference current detection unit detects a difference current exceeding a set value, and the effective value change detection unit displays an effective value change of the counterpart terminal current data. A reset processing unit that outputs an operation command for resetting to the ratio differential operation unit when detecting,
The ratio differential calculation unit receives the operation command, stops the calculation process, holds and outputs the previous calculation result, restarts the calculation process in response to the end of the operation command, or In response, the ratio setting value is changed from the first ratio setting value used immediately before to the second ratio setting value which is large enough not to respond to the difference current due to the difference in transmission delay time, and the end of the operation command. In response to the second ratio set value from the second ratio set value to the first ratio set value to resume the calculation process,
P CM current differential protection relay you, characterized in that. The synchronization processing unit, one or more of claims 1 to 6, characterized in that set value for a time synchronization deviation amount caused by a change in the transmission delay time due to the transmission path switching is provided with a setting value memory is stored in advance PCM current differential protection relay described in 1.

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