JP6161527B2 - Transmission line protection relay - Google Patents

Description

  The present invention relates to a power transmission line protection relay for protecting a power transmission line of a power system.

  In general, power transmission lines are roughly classified into overhead lines that pass through the air through steel towers and underground cables. While there are many temporary short-circuit faults or ground faults caused by lightning strikes in overhead line faults, underground cable faults are often permanent faults. For this reason, in the case of an overhead wire failure, after the failure is detected and the circuit breaker is once opened, the circuit breaker is closed again, whereas in the case of an underground cable failure, After detecting a failure and opening the circuit breaker, an operation is performed in which the circuit breaker is not closed again.

  As described above, the underground cable and overhead line differ in whether or not the circuit breaker is reclosed after the failure is detected. It is necessary to determine whether or not. When it is determined that the underground cable section has failed, the reclosing function of the circuit breaker is stopped.

  Japanese Patent Application Laid-Open No. 61-266017 (Patent Document 1) discloses a method for determining whether or not there is a failure in an underground cable section in an overhead power transmission line having an underground cable section in an intermediate portion. Specifically, protection relays are provided at both ends of the overhead power transmission line. Each protection relay includes a short-range fault detector that detects a fault in the overhead transmission line and a long-range fault detector that detects a fault in the underground cable transmission line.

JP-A-61-266017

  The above-mentioned patent documents do not specifically describe how the short-range fault detector and the long-range fault detector detect a fault. If the impedance at the fault point is calculated based on the measured transmission line voltage and transmission line current in the same manner as a conventional distance relay, it is possible that the calculated impedance may contain an error. The inventor found out. The reason is that the values of the zero-phase impedance and the positive-phase impedance are different between the cable and the overhead wire. For this reason, the prior art cannot accurately determine whether or not there is a failure point in the cable section (the above problem is not known at the time of filing this application).

  The present invention has been made in consideration of the above-mentioned problems, and its purpose is to accurately determine whether or not there is a failure point in a cable section in a transmission line in which cables and overhead lines are mixed. It is to provide a transmission line protection relay capable of.

  A power transmission line protection relay according to an embodiment protects a power transmission line including an overhead line section and a cable section, and includes an input unit, first and second calculation units, and a determination unit. The input unit receives the input of the transmission line current and the transmission line voltage measured at the installation point of the transmission line protection relay. The first calculation unit calculates the voltage at the installation point when the start point is assumed to be a failure point based on the impedance of the transmission line from the installation point to the start point of the cable section and the measured transmission line current. It is comprised so that it may calculate as a voltage of. The second calculation unit calculates the voltage at the installation point when the end point is assumed to be a failure point based on the impedance of the transmission line including the cable section from the installation point to the end point of the cable section and the measured transmission line current. It is configured to calculate as the second voltage. The determination unit is configured to determine whether there is a failure point in the cable section based on the first and second voltages and the measured transmission line voltage.

  According to the above embodiment, it is possible to accurately determine whether or not there is a failure point in the cable section in the transmission line in which the cable and the overhead line are mixed.

It is a figure which shows the model of the electric power grid | system to which the power transmission line protection relay 100 by Embodiment 1 is applied. It is an impedance diagram (R-jX diagram) showing the impedance of the power transmission line 20. It is a figure which shows the numerical example of the positive phase impedance and zero phase impedance of an overhead wire and a cable with a table format. It is a functional block diagram which shows the structure of the power transmission line protection relay 100 of FIG. It is a figure for demonstrating voltage Vin * which projected the input voltage Vin on the X-axis. It is a figure for demonstrating the method for removing the influence of load current. FIG. 5 is a functional block diagram illustrating configurations of a voltage calculation unit 130 and a failure section determination unit 150 in FIG. 4. 5 is a flowchart showing the operation of the power transmission line protection relay 100. It is a figure for demonstrating the voltage calculation in the case of a short circuit failure. It is a figure for demonstrating the voltage calculation in the case of a ground fault. It is a figure which shows the model of the electric power grid | system to which the power transmission line protection relay by Embodiment 2 is applied. It is a figure for demonstrating the calculation of voltage Vp1, Vp2 in the case of a short circuit failure. It is a figure for demonstrating the calculation of voltage Vp1, Vp2 in the case of a ground fault.

  Hereinafter, each embodiment will be described in detail with reference to the drawings. The same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

<Embodiment 1>
[Overall configuration of power system]
FIG. 1 is a diagram showing a model of a power system to which a power transmission line protection relay 100 according to Embodiment 1 is applied.

  In the model shown in FIG. 1, there are substations at both ends (A end and B end) of the transmission line 20, and generators 10 </ b> A and 10 </ b> B are provided far away from the A end and B end, respectively.

  At the A-terminal substation, an instrument transformer 32 that measures the current and voltage of the transmission line 20, that is, an instrument current transformer (CT) 30 and an instrument voltage transformer (PT) (not shown). ) Is provided. The power transmission line protection relay 100 is connected to the instrument transformer 32 and receives input of signals representing the voltage and current of the power transmission line 20 measured by the instrument transformer 32. The power transmission line protection relay 100 detects a failure of the power transmission line 20 based on the signals representing the input power transmission line voltage and power transmission line current.

  The power transmission line 20 is composed of an overhead line and a cable. In the example of FIG. 1, a cable section 24 is provided at the center of the power transmission line 20, an overhead line 22 is provided on the A end side of the cable section 24, and an overhead line 26 is provided on the B end side of the cable section 24. Yes. Let XL be the reactance component of the positive phase impedance of the transmission line 20 from the A end to the B end. In the cable section 24, the reactance component of the positive phase impedance from the A-terminal substation is provided between X1s and X1e.

  The power transmission line protection relay 100 includes a distance relay element (reference numeral 111 in FIG. 4). The distance relay element calculates the impedance based on the current and voltage flowing through the transmission line 20 measured by the instrument transformer 32. The distance relay element determines that there is a failure in the power transmission line 20 when the calculated impedance is within a predetermined protection range, and disconnects the failure section from the system so that the circuit breakers installed at both ends of the power transmission line 20 (see FIG. Open command is output to (not shown). Thereby, the power transmission line 20 is protected.

  In general, the protection range of the distance relay element is divided into three operation areas: Zone1, Zone2, and Zone3. The upper limit value Xz1 of the reactance component of the positive phase impedance in Zone 1 is set to about 80% of the reactance component XL of the positive phase impedance of the transmission line to the counterpart substation (B terminal substation). The distance relay element outputs a signal (relay operation signal) for opening the circuit breaker without delay with respect to a power transmission line failure in Zone1.

  The upper limit value Xz2 of the reactance component of the positive phase impedance in Zone 2 is set to 120 to 150% of the reactance component XL of the positive phase impedance to sufficiently cover the reactance component XL of the positive phase impedance up to the counterpart substation. The distance relay element outputs a relay operation signal after a predetermined time when the detected impedance is within Zone2.

  The upper limit value Xz3 of the reactance component of the positive phase impedance in Zone 3 is set so as to cover a farther region. When the detected impedance is in Zone 3, the distance relay element outputs a relay operation signal after a time period longer than a certain time period in Zone 2 has elapsed.

  In addition to the distance relay element described above, the power transmission line protection relay 100 has a function of more accurately detecting whether the failure point is in the cable section 24 or the overhead line sections 22 and 26 than in the past. Details of the function for detecting the failure section will be described in detail with reference to FIGS.

[Transmission line impedance]
FIG. 2 is an impedance diagram (R-jX diagram) showing the impedance of the power transmission line 20. In FIG. 2, the resistance component is indicated by a horizontal axis (referred to as “R axis”) and the reactance component is indicated as a vertical axis (referred to as “X axis”).

  Referring to FIG. 2, generally, the impedance of the overhead wire is represented by a straight line having an angle of 85 to 90 degrees from the R axis on the impedance diagram, whereas the impedance of the cable 24 is an angle from the R axis. Is often represented by a straight line smaller than 80 degrees. For this reason, in FIG. 2, the angle (impedance angle) formed between the straight line representing the impedance of the overhead wire sections 22 and 26 and the R-axis (impedance angle), and the angle formed between the straight line representing the impedance of the cable section 24 and the R-axis (impedance angle). Is different.

  FIG. 2 further shows the protection ranges (Zone1, Zone2, and Zone3) of the distance relay element described in FIG. When the power transmission line 20 is normal and the load is far away from the front, the impedance detected by the power transmission line protection relay 100 is substantially equal to the load impedance. In the impedance diagram of FIG. To position.

FIG. 3 is a diagram showing, in a tabular form, numerical examples of the positive phase impedance and the zero phase impedance of the overhead wire and the cable. In FIG. 3, numerical examples of the positive phase impedance Z1 and the zero phase impedance Z0 in the overhead wire and OF (Oil Filled) cable used for the extra high voltage transmission line with a nominal voltage of 275 kV are shown as values per unit length (1 km). It is shown. If numerical examples of FIG. 3, the cross-sectional area of the conductor of the overhead wire is 810～410Mm ^2, the cross-sectional area of the conductor of the OF cable is 400 mm ^2. The zero-phase impedance Z0 of the OF cable is shown for both cases where the cable sheath is a lead sheath and an aluminum sheath.

  As shown in FIG. 3, not only the impedance angle but also the ratio (Z0 / Z1) between the zero-phase impedance Z0 and the positive-phase impedance Z1 is different between the overhead wire and the cable.

[Configuration of transmission line protection relay]
FIG. 4 is a functional block diagram showing a configuration of the power transmission line protection relay 100 of FIG. Referring to FIG. 4, power transmission line protection relay 100 includes an input unit 102, an AD (Analog to Digital) conversion unit 104, a processing unit 106, a relay operation signal output unit 108, and a reclosing lock signal output unit 110. Including.

  The input unit 102 secures insulation between the internal circuit of the transmission line protection relay 100 and the outside, and transmits the transmission line voltage and the transmission line current input from the instrument transformer 32 of the transmission line 20 shown in FIG. The detection signal is converted into a signal having an appropriate voltage level. Input unit 102 further includes a low-pass filter circuit for removing high-frequency signal components included in the converted transmission line voltage signal and transmission line current signal.

  The transmission line voltage signal and the transmission line current signal from which the voltage level has been converted by the input unit 102 and from which the high frequency component has been removed are input to the AD conversion unit 104 and converted to digital data by the AD conversion unit 104.

  The processing unit 106 performs arithmetic processing using the digital data representing the transmission line voltage and the transmission line current output from the AD conversion unit 104 and preset internal data. The processing unit 106 is configured based on a computer including a CPU (Central Processing Unit), a memory, and the like.

  Specifically, the processing unit 106 includes a distance relay calculation unit 112, a Zone1 determination unit 114, a Zone2 determination unit 116, a Zone3 determination unit 118, a failure phase determination unit 120, an OR circuit 122, a voltage calculation unit 130, and a failure section determination unit. 150 functional blocks. The distance relay computing unit 112, the Zone 1 determination unit 114, the Zone 2 determination unit 116, the Zone 3 determination unit 118, the failure phase determination unit 120, and the OR circuit 122 constitute the distance relay element 111.

  The distance relay calculation unit 112 performs the same calculation as that of a conventional distance relay. Specifically, the distance relay calculation unit 112 calculates the impedance up to the failure point based on the input data representing the current and voltage of the transmission line. The distance relay calculation unit 112 outputs the calculated impedance to the Zone 1 determination unit 114, the Zone 2 determination unit 116, the Zone 3 determination unit 118, and the failure phase determination unit 120.

  Each of the Zone1 determination unit 114, the Zone2 determination unit 116, and the Zone3 determination unit 118 determines whether or not the calculated impedance value is within the operation range determined by the self-determination unit. When the calculated impedance is within the determined operating range, each determination unit immediately after a predetermined timing has elapsed (in the case of the Zone 1 determination unit 114, immediately after the fixed time in the case of the Zone 2 determination unit 116, Zone 3 In the case of the determination unit 118, the output signal to the OR circuit 122 and the voltage calculation unit 130 is activated at a later timing.

  The OR circuit 122 activates the output signal to the relay operation signal output unit 108 when any of the output signals of the determination units 112, 114, 116 is activated. The relay operation signal output unit 108 outputs a relay operation signal when the output signal of the OR circuit 122 is activated. In response to the relay operation signal, the corresponding circuit breaker (usually provided at the A-end and B-end substations in FIG. 1) is opened.

  The failure phase determination unit 120 identifies a failure phase among the A phase, the B phase, and the C phase based on the impedance calculation result by the distance relay calculation unit 112. Specifically, the fault phase determination unit 120 includes an A phase ground fault, a B phase ground fault, a C phase ground fault, an AB phase short circuit (ground fault) fault, a BC phase short circuit (ground fault) fault, and a CA phase short circuit. (Ground fault) It is determined whether it is a failure or a three-phase failure.

  The voltage calculation unit 130 starts the calculation in response to the activation of the output signal of the Zone1 determination unit 114. Specifically, based on the determination result of the failure phase determination unit 120, the voltage calculation unit 130 performs voltage calculation for determining a failure section for a phase related to the failure phase. Details of the voltage calculation will be described later.

  The failure section determination unit 150 receives the calculation result of the voltage calculation unit 130 and determines whether or not the failure point is a cable section. When the failure section determination unit 150 determines that the failure point is a cable section, the failure section determination unit 150 notifies the reclosing lock signal output unit 110 to that effect. Thus, the circuit breaker is locked so as not to be reclosed by the reclose lock signal output from the reclose lock signal output unit 110 to the circuit breaker.

[About judgment method of failure section]
Hereinafter, the failure section determination method will be described by taking the case of the A-phase ground fault as an example. In this specification, the voltages of the A phase, B phase, and C phase input to the transmission line protection relay 100 are Va, Vb, and Vc, respectively, and the currents of the A phase, B phase, and C phase are Ia, Ib, and Ic, respectively. And Further, the zero-phase voltage, the positive-phase voltage, and the negative-phase voltage calculated from these voltages and currents are V0, V1, and V2, respectively, and the zero-phase current, the positive-phase current, and the negative-phase current are I0, I1, and I2, respectively. To do.

  In general, the A phase voltage Va, the A phase current Ia, and the zero phase current I0 at the time of the A phase ground fault satisfy the following relational expression.

Va = ZF × (Ia + ((Z0 / Z1) −1) × I0) (1)
In the above equation (1), the positive phase impedance from the protection relay installation point to the failure point is ZF, the positive transmission line impedance per unit length from the protection relay installation point to the failure point is Z1, and the protection relay Z0 is the zero-phase impedance of the transmission line per unit length from the installation point to the failure point. The reason why the zero-phase current appears in the equation is that in the case of a ground fault, the fault current flows through the ground.

  From the above equation (1), the impedance ZF up to the failure point is expressed as follows by the A-phase voltage Va, the A-phase current Ia and the zero-phase current I0 input to the power transmission line protection relay 100.

ZF = Va / (Ia + ((Z0 / Z1) −1) × I0) (2)
When the transmission line is composed of either an overhead line or a cable line, Z0 / Z1 is constant at the failure point in the transmission line section, so the distance relay element is grounded according to the above equation (2). There is no problem in calculating the impedance up to the point of failure at the time of failure. For example, since the set value (X1) of Zone 1 applied to the distance relay element is determined to be approximately 80% of the impedance of the transmission line between substations, Z0 / used for calculating the impedance ZF up to the fault point There is no problem using Z0 / Z1 at the point of the set value X1 of Zone1 as Z1.

  However, when the transmission line has a configuration in which overhead lines and cable lines are mixed, the value of Z0 / Z1 used for the calculation of the impedance ZF differs depending on the position of the failure point on the transmission line. For this reason, if impedance ZF to the fault point is calculated simply by using Z0 / Z1 at the set value X1 of Zone1, an error will occur.

  For the above reasons, the power transmission line protection relay 100 according to the first embodiment determines whether or not there is a failure point in the cable section 24 by a method different from the conventional method. Specifically, in the case of an A-phase ground fault, in the determination method, first, the reactance component (X-axis component) of the zero-phase impedance of the overhead wire from the installation point of the protection relay to the start point of the cable section 24 is set to X0s. The reactance component (X-axis component) of the positive phase impedance of the overhead wire from the relay installation point to the start point of the cable section 24 is defined as X1s. The zero-phase impedance and the positive-phase impedance reactance component ratio KN1 (= X0s / X1s), the positive-phase impedance reactance component X1s, and zero calculated from the transmission line currents Ia, Ib, and Ic. A voltage Vp1 represented by the following expression is calculated using the phase current I0.

Vp1 = X1s × (Ia + (KN1-1) × I0) (3)
In the above equation (3), the voltage Vp1 is the transmission line voltage detected by the transmission line protection relay 100 when the failure point is assumed to be the start point of the cable section 24 (Va in the case of an A-phase ground fault) Means the value of the X-axis component (value projected on the X-axis) or the value of the detection voltage Va projected in the vector direction obtained by advancing the fault current Ia by 90 degrees (Ia and Va are the faults of the A-phase ground fault) If).

  Furthermore, in the determination method, the reactance component of the total zero-phase impedance of the overhead wire and the cable from the installation point of the protection relay to the end point of the cable section 24 is X0e, and the distance from the installation point of the protection relay to the end point of the cable section 24 is Let X1e be the reactance component of the total positive phase impedance of the overhead wire and the cable. The zero-phase impedance and the positive-phase impedance reactance component ratio KN2 (= X0e / X1e), the positive-phase impedance reactance component X1e, and the zero calculated from the transmission line currents Ia, Ib, and Ic. A voltage Vp2 represented by the following equation is calculated using the phase current I0.

Vp2 = X1s × (Ia + (KN2-1) × I0) (4)
In the above equation (4), the voltage Vp2 is the transmission line voltage detected by the transmission line protection relay 100 assuming that the failure point is the end point of the cable section 24 (Va in the case of an A-phase ground fault). The value of the X-axis component (the value projected on the X-axis) or the value of the detection voltage Va projected in the vector direction obtained by advancing the fault current Ia by 90 degrees (Ia and Va are in the case of an A-phase ground fault) ).

  In the above equations (3) and (4), the voltages Vp1 and Vp2 are obtained by multiplying the fault current by the reactance of the positive phase impedance, so the transmission line voltage is projected on the X axis (reactance axis) of the impedance diagram. It is equivalent to the value.

  FIG. 5 is a diagram for explaining a voltage Vin * obtained by projecting the input voltage Vin on the X axis. Referring to FIG. 5, since the input current Iin at the time of failure may be regarded as being on the R axis, projecting on the X axis is projected in the direction of the current vector obtained by advancing the phase of the input current Iin by 90 °. Is equivalent to

  Here, the reason for projecting on the X axis is to compare the magnitudes of the voltages Vp1 and Vp2 with the magnitude of the input voltage Vin in the same vector direction. If there is an arc resistance at the failure point, the voltage generated by the arc resistance is in phase with the input current, so by projecting the phase of the input current in the direction of the current vector by 90 °, the influence of the voltage generated by the arc resistance is Can be removed.

  When each of the voltage Vp1, the voltage Vp2, and the input voltage Vin * (Va * in the case of an A-phase ground fault) is obtained as described above, the values are compared. Thus, it can be determined whether or not the failure point is in the cable section 24.

Specifically, when the failure point is closer to the start point of the cable section 24,
Vp1 <Vin * (5)
When the failure point is far from the start point of the cable section 24,
Vp1> Vin * (6)
It becomes. Therefore, when the failure point is in the cable section 24,
Vp1 ≧ Vin * and Vp2 ≦ Vin * (7)
Is satisfied.

[Removing the influence of load current]
In order to determine a more accurate cable section, it is desirable to delete the load current from the input current Vin of the power transmission line protection relay. This is because the input current Vin is a combined current of the fault current IF and the load current IL.

  FIG. 6 is a diagram for explaining a method for removing the influence of the load current. Referring to FIG. 6, load current IL (t) several cycles before the occurrence of a failure is equal to input current Iin (t). A waveform in a case where it is assumed that the load current IL (t) continues during the failure is shown by a one-dot chain line in FIG. The fault current IF (t) is obtained by subtracting the load current IL (t) (dotted line in the figure) estimated to continue during the fault from the input current Iin (t) during the fault at each time. It is done. In the calculation of the voltage calculation unit 130, the load section IL (t) calculated by the above method is used in place of the input current Vin, so that a more accurate failure section can be determined.

[Details of voltage calculation and failure section determination]
FIG. 7 is a functional block diagram illustrating configurations of the voltage calculation unit 130 and the failure section determination unit 150 of FIG. FIG. 8 is a flowchart showing the operation of the power transmission line protection relay 100. Hereinafter, the details of the determination of the failure section will be described with reference mainly to FIGS.

  As already described, the transmission line protection relay 100 receives detection signals of the transmission line voltages Va, Vb, Vc and the transmission line currents Ia, Ib, Ic from the instrument transformer 32 (step S100). Next, the distance relay calculation unit 112 of FIG. 4 performs a normal distance relay calculation (step S105). Based on the result, the determination units 114, 116, and 118 perform zone determination, and the failure phase determination unit 120 A failure phase is determined (step S115). Based on the determination results of the determination units 114, 116, and 118, a relay operation signal is output from the output unit 108 as a relay operation signal (step S115).

  The voltage calculation unit 130 starts the calculation in response to the activation of the output signal of the Zone1 determination unit 114. As shown in FIG. 7, the voltage calculation unit 130 includes a calculation unit 132 (Vp1 calculation unit 134 and Vp2 calculation unit 136), a calculation unit 138 (Vp1 calculation unit 134 and Vp2 calculation unit 136), and a projection processing unit 144. And an input current correction unit 146.

  The calculation unit 132 calculates the voltages Vp1 and Vp2 in the case of a short circuit failure, and the calculation unit 138 calculates the voltages Vp1 and Vp2 in the case of a ground fault (step S120). The projection processing unit 144 performs a projection process on the X axis of the input voltage Vin (step S125).

  As described with reference to FIG. 6, the input current correction unit (failure current calculation unit) 146 estimates the load current IL (t) after the failure based on the input current Iin (t) immediately before the failure, and the estimated load The fault current IF (t) is calculated by subtracting the current IL (t) from the input current Iin (t) after the fault. The calculation processes in the calculation units 132 and 134 and the Vin projection process in the projection processing unit 144 use the fault current IF (t) calculated by the input current correction unit 146 instead of the input current Iin (t). It is desirable to be executed.

  FIG. 9 is a diagram for explaining voltage calculation in the case of a short circuit failure. Referring to FIG. 9, for example, in the case of a short circuit failure between AB phases, the current Iab = Ib−Ia between the AB phases becomes the input current Iin, and the voltage Vab = Vb−Va between the AB phases becomes the input voltage Vin.

  In addition, in the case of a ground fault in the A phase and the B phase, it is actually calculated as a short circuit failure between the AB phases.

  The voltage Vp1 is given by the following expression using the reactance component X1s of the positive phase impedance from the installation point of the protection relay to the start point of the cable section 24.

Vp1 = X1s × Iab (8)
Similarly, the voltage Vp2 is given by the following equation using the reactance component X1e of the positive phase impedance from the installation point of the protection relay to the end point of the cable section 24.

Vp2 = X1e × Iab (9)
The same applies to the case of a short circuit failure between the BC phases and between the CA phases. The voltage Vp1 is the value of the X-axis component (on the X-axis) of the voltage (Vab in the case of a short-circuit fault between AB phases) detected by the transmission line protection relay 100 when the failure point is the start point of the cable section 24. Or the value of the detection voltage Vab projected in the vector direction obtained by advancing the fault current Iab by 90 degrees (Iab and Vab are in the case of a short-circuit fault between AB phases). The voltage Vp2 is the value of the X-axis component of the voltage (Vab in the case of a short-circuit fault between AB phases) detected by the transmission line protection relay 100 when the failure point is the end point of the cable section 24 (projected on the X-axis. Value) or the value of the detection voltage Vab projected in the vector direction obtained by advancing the fault current Iab by 90 degrees (Iab and Vab are in the case of a short-circuit fault between AB phases).

  FIG. 10 is a diagram for explaining voltage calculation in the case of a ground fault. In the case of an A-phase ground fault, since it has already been described with reference to equations (3) and (4), the description will not be repeated. In the case of a ground fault in the B phase and the C phase, the voltages Vp1 and Vp2 are calculated as in the case of the A phase.

  Referring to FIGS. 7 and 8 again, failure section determination unit 150 obtains voltages Vp1 and Vp2 that are values projected on the X axis, and input voltage Vin * obtained by projecting input voltage Vin on the X axis. Compare. Here, the values of the voltages Vp1, Vp2, and Vin are shown in FIG. 9 according to the fault phase in the case of a short-circuit fault, and are shown in FIG. 10 according to the fault phase in the case of a ground fault. .

  Specifically, failure section determination unit 150 includes determination units 152 and 154 and AND circuit 156. The determination unit 152 determines whether the voltage Vp1 is equal to or higher than the input voltage Vin * (step S130). The determination unit 154 determines whether the voltage Vp2 is equal to or lower than the input voltage Vin * (step S135). The AND circuit 156 activates an output signal to the reclosing lock signal output unit 110 when both the determination results of the determination units 152 and 154 are satisfied (when both Step S130 and Step S135 are YES). When the output signal of the AND circuit 156 is activated, the reclosing lock signal output unit 110 outputs a signal for locking the reclosing of the corresponding circuit breaker (step S140).

[effect]
As described above, the transmission line protection relay according to the first embodiment uses the reactance components of the zero-phase and positive-phase impedances from the installation point of the protection relay to the start point and end point of the cable, and the voltage according to the fault phase. It is determined whether or not there is a failure in the cable section by executing an operation and comparing the calculated voltage with the actual input voltage. Therefore, since the zero phase and positive phase impedance can be set correctly, it is possible to accurately determine whether or not the cable section is faulty.

[Modification]
In the above embodiment, the case of a single cable section has been described. However, even in the case of a transmission line having a plurality of cable sections, a failure is caused in each cable section by performing the same calculation as described above in each cable section. Whether or not there is a point can be determined.

<Embodiment 2>
In the second embodiment, determination of a failure section when a cable section and an overhead line section are mixed in a multi-line power transmission line will be described.

  FIG. 11 is a diagram illustrating a model of a power system to which the power transmission line protection relay according to the second embodiment is applied.

  In the model shown in FIG. 11, a case where there are two power transmission lines 200 is shown. There are substations at both ends (A end, B end) of the power transmission line 200, and generators 10A, 10B are provided far away from the A end and the B end. The power transmission line protection relay 100 is installed in a substation at the A end, and measures the current and voltage of the power transmission line (two lines) at the A end with an instrument transformer (the current transformer 30 and a voltage transformer (not shown)).

  The power transmission line 200 has a two-line configuration in which overhead lines and cables are mixed. Cable sections 240 and 241 are provided in the center of the transmission line, overhead line sections 220 and 221 are provided on the A end side of the cable sections 240 and 241, and overhead line sections are provided on the B end side of the cable sections 240 and 241. 260, 261 are provided.

  In the case of two lines, an induced electromotive force is generated by the current flowing in the adjacent line in the overhead line section. For this reason, it is necessary to correct the arithmetic expressions of the voltages Vp1 and Vp2 described in the first embodiment using the zero-phase mutual induction impedance. As in the case of the first embodiment, the voltage Vp1 is the transmission line voltage estimated to be detected by the transmission line protection relay 100 on the X axis when the failure point is assumed to be the start point of the cable section 24. The voltage Vp2 means a value obtained by projecting the transmission line voltage estimated to be detected by the transmission line protection relay 100 on the X axis when the failure point is assumed to be the end point of the cable section 24. To do.

  FIG. 12 is a diagram for explaining the calculation of the voltages Vp1 and Vp2 in the case of a short circuit failure. That is, in the case of the two transmission lines shown in FIG. 11, the calculation formulas of the voltages Vp1 and Vp2 when a short-circuit failure occurs are shown in the table of FIG. As shown in FIG. 12, in the case of a short circuit failure, the calculation method of the voltages Vp1 and Vp2 is the same for the case of one line and the case of a plurality of lines.

  FIG. 13 is a diagram for explaining calculation of the voltages Vp1 and Vp2 in the case of a ground fault. Hereinafter, the case of the A-phase ground fault will be described. The same applies to the B phase and the C phase.

  Referring to FIG. 13, in the case of a ground fault, it is necessary to consider the induced electromotive force due to zero-phase current I0m flowing in the adjacent line. The reactance component of the mutual induction impedance of the overhead lines 220, 221 from the installation point of the protection relay to the start point of the cable section is XMs, and the positive phase impedance of the overhead line 220 from the installation point of the protection relay to the start point of the cable section Let the reactance component be X1s. When the ratio KM1 (= XMs / X1s) between the two is used, the above equation (3) is corrected as the following equation.

Vp1 = X1s × (Ia + (KN1-1) × I0 + KM1 × I0m) (10)
Similarly, the reactive component of the total mutual induction impedance of the overhead lines 220 and 221 and the cables 240 and 241 from the installation point of the protection relay to the end point of the cable section is XMe, and from the installation point of the protection relay to the end point of the cable section The reactance component of the total positive phase impedance of the overhead wire 220 and the cable 240 is X1e. When the ratio KM2 (= XMe / X1e) of both is used, the above equation (4) is corrected as the following equation.

Vp2 = X1e × (Ia + (KN2-1) × I0 + KM2 × I0m) (11)
Since the second embodiment is the same as the first embodiment except for the calculation formulas of the voltages Vp1 and Vp2, the description will not be repeated. As described in the equations (5) to (7), whether or not the failure point is in the cable sections 240 and 241 is projected on the X-axis and the voltages Vp1 and Vp2 that are values projected on the X-axis. This can be determined by comparing the input voltage Vin * (Va * in the case of an A phase ground fault).

  As described above, even in the case of a multi-line power transmission line, the voltages Vp1 and Vp2 can be accurately calculated using the mutual induction impedance from the installation point of the protection relay to the start point and end point of the cable section. It is possible to accurately determine whether a failure has occurred in the cable section.

  In addition, the configuration other than the arrangement of the overhead wire and the cable wire as illustrated, that is, when there is a cable wire from the protection relay installation point and there is an overhead wire in the distance, and vice versa, the cable is used in the same manner. A section can be determined.

  The embodiment disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  10A, 10B generator, 20,200 transmission line, 22, 26, 220, 221, 260, 261 overhead line (section), 24, 240, 241 cable (section), 30 current transformer, 32 instrument transformer, 100 power transmission line protection relay, 102 input unit, 104 AD conversion unit, 106 processing unit, 108 relay operation signal output unit, 110 reclosing lock signal output unit, 111 distance relay element, 112 distance relay operation unit, 114 Zone1 determination unit, 116 Zone2 determination unit, 118 Zone3 determination unit, 120 Fault phase determination unit, 130 Voltage calculation unit, 144 Projection processing unit, 146 Input current correction unit, 150 Fault zone determination unit.

Claims (5)

A transmission line protection relay that protects a transmission line including an overhead line section and a cable section,
An input unit for receiving an input of a transmission line current and a transmission line voltage measured at an installation point of the transmission line protection relay;
Based on the impedance of the transmission line from the installation point to the start point of the cable section and the measured transmission line current, the voltage at the installation point when the start point is assumed to be a failure point is a first value. A first computing unit configured to calculate as a voltage;
Based on the impedance of the transmission line including the cable section from the installation point to the end point of the cable section and the measured transmission line current, the voltage at the installation point when the end point is assumed to be a failure point is calculated. A second computing unit configured to calculate as a second voltage;
A determination unit configured to determine whether there is a failure point in the cable section based on the first and second voltages and the measured transmission line voltage ;
The determination unit is projected when the first and second voltages and the measured transmission line voltage are projected in a current vector direction obtained by advancing the phase of the measured transmission line current by 90 degrees. A transmission line configured to determine whether there is a failure point in the cable section by comparing the measured value of the transmission line voltage with the projected first and second voltages Protection relay. The power line protection relay is
A distance relay element configured to detect a failure of the power transmission line and to output a signal for opening a circuit breaker provided in the power transmission line upon failure detection;
The power transmission line according to claim 1 , wherein the determination unit is configured to output a signal for locking a reclosing circuit of the circuit breaker when it is determined that the failure point is in the cable section. Protection relay. The first calculation unit, when a ground fault is detected by the distance relay element, reactance components of zero-phase impedance and positive-phase impedance of the transmission line from the installation point to the start point of the cable section And the first voltage is calculated based on the ratio of the reactance component of the positive phase impedance of the transmission line from the installation point to the start point of the cable section,
The second computing unit, when a ground fault is detected by the distance relay element, of reactance components of zero-phase impedance and positive-phase impedance of the transmission line from the installation point to the end point of the cable section The transmission according to claim 2 , configured to calculate the second voltage based on a ratio and a reactance component of a positive phase impedance of the transmission line from the installation point to an end point of the cable section. Wire protection relay. The transmission line protection relay estimates a load current after failure detection based on a transmission line current measured immediately before failure detection by the distance relay element, and transmits the estimated load current measured after failure detection. A fault current calculator configured to calculate the fault current by subtracting from the wire current;
The transmission line protection relay according to claim 2 , wherein the first and second calculation units and the determination unit perform calculation using the calculated fault current instead of the measured transmission line current. The power transmission line includes a plurality of lines,
When the first relay is detected as a ground fault by the distance relay element, each reactance component of the mutual induction impedance and the positive phase impedance of the transmission line from the installation point to the start point of the cable section Further configured to calculate the first voltage based on a ratio of:
The second calculation unit, when a ground fault is detected by the distance relay element, a ratio of reactance components of the mutual induction impedance and the positive phase impedance of the transmission line from the installation point to the end point of the cable section The transmission line protection relay according to claim 3 , further configured to calculate the second voltage based on the following.

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