Protective relay

Abstract

The present invention provides a protective relay device that can reduce the processing load when determining the direction of a fault. [Solution] The protective relay device includes an electrical quantity acquisition unit that acquires instantaneous current time series values ​​and instantaneous voltage time series values; a current change vector calculation unit that calculates a current change vector of the protected line from the instantaneous current time series values; a voltage change vector calculation unit that calculates a voltage change vector of the bus connected to the protected line from the instantaneous voltage time series values; a phase angle calculation unit that calculates a reference phase angle based on the current change vector and the voltage change vector; and a direction determination unit that determines the direction of the fault point in the protected line based on the reference phase angle, a first angle, and a second angle that is larger than the first angle.

Description

Technical Field

[0001] The present disclosure relates to a protective relay device.

Background Art

[0002] Conventionally, a distance relay device is known as a protective relay device that detects a short-circuit fault (accident) and a ground fault of a transmission line in a power system and protects the transmission line. For example, a distance relay device applied to the protection of a three-phase AC power transmission line includes a distance determination element that determines whether an impedance corresponding to the distance to the fault point of the transmission line is within a set value, and a direction determination element that determines whether the fault point is in front of or behind the installation point of the distance relay device. The direction determination element determines whether a transmission line accident has occurred in front of or behind the distance relay device based on the phase relationship between voltage and current.

[0003] The direction determination relay method according to Japanese Patent Laid-Open No. 52-17644 (Patent Document 1) is configured to determine the necessity of protecting a protected system based on the outputs of means for determining the direction of an accident from changes in the voltage and current of the protected system and means for detecting the occurrence of an accident in the system from the electrical quantities of the protected system.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] One objective in certain aspects of this disclosure is to provide a protective relay device that can reduce the processing load when determining the direction of a fault point. [Means for solving the problem]

[0007] According to one embodiment, a protective relay device for protecting a power system is provided. The protective relay device includes an electrical quantity acquisition unit that acquires the time-series instantaneous value of current detected in the power system and the time-series instantaneous value of voltage detected in the power system; a current change vector calculation unit that calculates the current change vector of a protected line included in the power system from the time-series instantaneous value of current; a voltage change vector calculation unit that calculates the voltage change vector of a bus connected to the protected line from the time-series instantaneous value of voltage; a phase angle calculation unit that calculates a reference phase angle based on the current change vector and the voltage change vector; and a direction determination unit that determines the direction of a fault point in the protected line based on the reference phase angle, a first angle, and a second angle that is greater than the first angle. [Effects of the Invention]

[0008] According to this disclosure, the processing load when determining the direction of the fault point can be reduced. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows an example of the overall configuration of a protective relay device. [Figure 2]This figure shows the equivalent circuit for a single-phase ground fault using the symmetrical coordinate method. [Figure 3] This figure shows the equivalent circuit during a two-phase short-circuit fault using the symmetrical coordinate method. [Figure 4] This figure shows the equivalent circuit during a three-phase short-circuit fault using the symmetrical coordinate method. [Figure 5] This figure shows the equivalent circuit obtained by replacing the fault point resistance in Figure 4 with impedance. [Figure 6] This diagram illustrates the positional relationship between the positive-sequence voltage change vector and the positive-sequence current change vector. [Figure 7] This figure shows the current waveforms when the CT is saturated and when it is not saturated. [Figure 8] This diagram illustrates the positional relationship between the positive-sequence voltage change vector and the positive-sequence current change vector when CT saturation is taken into consideration. [Figure 9] This diagram illustrates that the positive-sequence voltage change vector and its inverse vector are in phase. [Figure 10] This block diagram shows an example of the functional configuration of a protective relay device according to Embodiment 1. [Figure 11] This figure shows the equivalent circuit during a one-phase ground fault according to Embodiment 2. [Figure 12] This figure shows an example of the functional configuration of the direction determination unit according to Embodiment 2. [Figure 13] This is a vector diagram showing the relationship between current and voltage before and after a single-phase ground fault. [Figure 14] This figure shows another example of the functional configuration of the direction determination unit according to Embodiment 2. [Figure 15] This is a vector diagram showing the relationship between current and voltage before and after a short-circuit fault. [Figure 16] This flowchart shows an example of a fault location direction determination method according to Embodiment 2. [Modes for carrying out the invention]

[0010] Hereinafter, the present embodiment will be described while referring to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

[0011] Embodiment 1. <Overall Configuration> FIG. 1 is a diagram showing an example of the overall configuration of a protective relay device. Referring to FIG. 1, a digital protective relay device 100 is installed, for example, inside a substation. In the present embodiment, an example in which the protective relay device 100 for protecting a power system is a distance relay device will be described. The substation includes a circuit breaker 50 that disconnects the transmission line 7 from the power system in the event of a fault in the transmission line 7 or the like, a current transformer (CT: Current Transformer) 60 for detecting the current information of the transmission line 7, and a voltage transformer (VT: Voltage Transformer) 70 for detecting the voltage information of the bus 8. The transmission line 7 is a three-phase transmission line.

[0012] The CT 60 detects the current of each phase (for example, phase A, phase B, and phase C) of the transmission line 7 (that is, the phase A current, the phase B current, and the phase C current). More specifically, the CT 60 converts the magnitude of the current of each phase of the transmission line 7 to the input current level of the protective relay device 100. The VT 70 detects the voltage of each phase of the bus 8 (that is, the phase A voltage, the phase B voltage, and the phase C voltage). More specifically, the VT 70 converts the magnitude of the voltage of each phase of the transmission line 7 to the input voltage level of the protective relay device 100. The information on the current detected by the CT 60 and the voltage detected by the VT is input to the protective relay device 100.

[0013] The protective relay device 100 performs necessary operations such as relay calculations using the input electrical quantities (for example, current and voltage), and determines whether a fault has occurred within the protection zone of a transmission line or the like. When the protective relay device 100 detects a fault within the protection zone, it outputs an opening command (for example, a trip signal) to the circuit breaker 50 provided on the transmission line 7. The protective relay device 100 includes, as a hardware configuration, an auxiliary transformer 10, a signal conversion unit 20, and an arithmetic processing unit 30.

[0014] The auxiliary transformer 10 takes in the electrical quantities from CT60 and VT70, converts them into voltage signals suitable for signal processing in the internal circuitry, and outputs them. The signal conversion unit 20 takes in the electrical quantities (i.e., analog electrical quantities) output from the auxiliary transformer 10 and converts them into digital data. Specifically, the signal conversion unit 20 includes filters 21 and 23, sample-and-hold circuits (corresponding to the SH circuits in the figure) 24 and 25, a multiplexer 26, and an A / D converter 27.

[0015] Filters 21 and 23 are analog filters that remove high-frequency noise components from the current and voltage waveform signals output from the auxiliary transformer 10. The outputs of filters 21 and 23 are input to sample-and-hold circuits 24 and 25, respectively. Sample-and-hold circuits 24 and 25 sample the current and voltage waveform signals output from filters 21 and 23, respectively, at predetermined sampling periods.

[0016] The multiplexer 26 sequentially switches the waveform signals input from the sample-and-hold circuits 24 and 25 in time series based on the sampling signal input from the arithmetic processing unit 30 and outputs them to the A / D converter 27. The A / D converter 27 converts the waveform signal input from the multiplexer 26 from analog data to digital data. The A / D converter 27 outputs the digitally converted waveform signal to the arithmetic processing unit 30.

[0017] The arithmetic processing unit 30 is primarily composed of a microcomputer. Specifically, the arithmetic processing unit 30 includes a CPU (Central Processing Unit) 32, a ROM (Read Only Memory) 33, a RAM (Random Access Memory) 34, a DO (Digital Output) circuit 36, a DI (Digital Input) circuit 37, a display 38, and an input interface 39. These are connected by a bus 31.

[0018] The CPU 32 controls the protective relay device 100 by reading and executing a program pre-stored in the ROM 33. The RAM 34, as volatile memory, and the ROM 33, as non-volatile memory, are used as the main memory of the CPU 32. The ROM 33 stores programs and setting values ​​for signal processing. The CPU 32 acquires digital data from the signal conversion unit 20 via the bus 31. The CPU 32 performs relay calculations for fault detection using the acquired digital data according to the program stored in the ROM 33. The CPU 32 determines whether or not a fault has occurred based on the relay calculation results.

[0019] When the CPU 32 detects a fault (i.e., determines that a fault has occurred), it outputs an open command to the circuit breaker 50 via the DO circuit 36 ​​to isolate the faulty section from the power system. The DI circuit 37 receives a digital input signal, for example, which is a signal indicating the opening and closing information of the circuit breaker 50. The display 38 is, for example, a liquid crystal display. The input interface 39 is typically a set of buttons, etc., which accept various operations from the user (e.g., an operator) of the protective relay device 100.

[0020] Furthermore, at least a portion of the protective relay device 100 may be configured using circuits such as FPGAs (Field Programmable Gate Arrays) and ASICs (Application Specific Integrated Circuits). Also, at least a portion of the protective relay device 100 may be configured using analog circuits.

[0021] <Method for determining the direction of the fault point> (Equivalent circuit) Figure 2 shows the equivalent circuit for a single-phase ground fault using the symmetrical coordinate method. Specifically, the equivalent circuit shown in Figure 2 is the equivalent circuit for a single-phase ground fault using the symmetrical coordinate method, which involves virtually moving the power supply to the fault point and generating a fault current. The CT in the figure inputs current information to the protective relay. Although not shown, the VT is installed near the CT and inputs voltage information to the protective relay. Typically, Figure 2 shows the equivalent circuit when a ground fault occurs in one of the three phases (e.g., phase A, phase B, phase C) of a single transmission line (specifically, phase A) in the forward direction (e.g., the protection direction).

[0022] Let's consider, for example, the case where a power transmission line is protected by a distance relay. If the fault is located in the direction from the distance relay, which is located at the end of the power transmission line, to the other end of the power transmission line, the input voltage to the distance relay will lead the input current by the angle of the power transmission line (for example, around 90°). This "direction to the other end" is referred to as "forward." On the other hand, if the fault is located behind the distance relay (i.e., in the opposite direction from the other end), the phase relationship between the input voltage and input current will be the opposite of the above. This "direction opposite to the other end" is referred to as "backward."

[0023] Referring to Figure 2, “Ef” is the power supply voltage when the power supply is virtually moved from the actual power supply location to the fault point when a fault occurs, so that the fault current flows toward the fault point. “Rf” is the resistance at the fault point. “ZS1”, “ZS2”, and “ZS0” are the “positive-sequence back impedance”, “negative-sequence back impedance”, and “zero-sequence back impedance”, respectively, from the actual rear power supply on the local end to the relay installation point on the local end (i.e., the installation point of the protective relay device 100). “ZR1”, “ZR2”, and “ZR0” are the “positive-sequence back impedance”, “negative-sequence back impedance”, and “zero-sequence back impedance”, respectively, from the relay installation point on the other end of the transmission line to the actual rear power supply on the other end.

[0024] "ZL1", "ZL2", and "ZL0" are the "positive-sequence impedance", "negative-sequence impedance", and "zero-sequence impedance" of the transmission line (hereinafter also simply referred to as "the line"), respectively. "ZL11", "ZL21", and "ZL01" are the "positive-sequence impedance", "negative-sequence impedance", and "zero-sequence impedance" of the line from the relay installation point on the local end to the fault point, respectively. "ZL12", "ZL22", and "ZL02" are the "positive-sequence impedance", "negative-sequence impedance", and "zero-sequence impedance" of the line from the fault point to the relay installation point on the other end, respectively. Here, "ZL1 = ZL11 + ZL12", "ZL2 = ZL21 + ZL22", and "ZL0 = ZL01 + ZL02".

[0025] "ΔV1" is the difference in positive-sequence voltage before and after the fault (i.e., the change obtained by subtracting the positive-sequence voltage before the fault from the positive-sequence voltage at the time of the fault). "ΔV2" is the difference in negative-sequence voltage before and after the fault (i.e., the change obtained by subtracting the negative-sequence voltage before the fault from the negative-sequence voltage at the time of the fault). "ΔV0" is the difference in zero-sequence voltage before and after the fault (i.e., the change obtained by subtracting the zero-sequence voltage before the fault from the zero-sequence voltage at the time of the fault). "ΔI1" is the difference in positive-sequence current before and after the fault (i.e., the change obtained by subtracting the positive-sequence current before the fault from the positive-sequence current at the time of the fault), "ΔI2" is the difference in negative-sequence current before and after the fault (i.e., the change obtained by subtracting the negative-sequence current before the fault from the negative-sequence current at the time of the fault), and "ΔI0" is the difference in zero-sequence current before and after the fault (i.e., the change obtained by subtracting the zero-sequence current before the fault from the zero-sequence current at the time of the fault).

[0026] Figure 3 shows the equivalent circuit for a two-phase short-circuit fault using the symmetrical coordinate method. Specifically, the equivalent circuit shown in Figure 3 is the equivalent circuit for a two-phase short-circuit fault using the symmetrical coordinate method, which involves virtually moving the power supply to the fault point and generating a fault current. Typically, Figure 3 shows the equivalent circuit when a short-circuit fault occurs in two of the three phases (specifically, phases B and C) at the front. The symbols shown in Figure 3 are as explained in Figure 2.

[0027] Figure 4 shows the equivalent circuit for a three-phase short-circuit fault using the symmetrical coordinate method. Specifically, the equivalent circuit shown in Figure 4 is the equivalent circuit for a three-phase short-circuit fault using the symmetrical coordinate method, which involves virtually moving the power supply to the fault point and generating a fault current. The equivalent circuit shown in Figure 4(a) is the equivalent circuit when the three-phase short-circuit fault occurs in the forward position. The equivalent circuit shown in Figure 4(b) is the equivalent circuit when the three-phase short-circuit fault occurs in the backward position. The symbols shown in Figure 4 are as explained in Figure 2.

[0028] Here, we consider representing the equivalent circuits for a ground fault shown in Figure 2, a two-phase short-circuit fault shown in Figure 3, and a three-phase short-circuit fault shown in Figure 4 as a single positive-sequence circuit. Specifically, we consider replacing the fault point resistance Rf in the equivalent circuit of Figure 4 with impedance Zf.

[0029] Figure 5 shows the equivalent circuit obtained by replacing the fault point resistance in Figure 4 with impedance. Specifically, the equivalent circuit shown in Figure 5(a) is the equivalent circuit obtained by replacing the fault point resistance Rf in Figure 4(a) with impedance Zf. The equivalent circuit shown in Figure 5(b) is the equivalent circuit obtained by replacing the fault point resistance Rf in Figure 4(b) with impedance Zf.

[0030] Referring to Figure 5(a), the inverted-phase and zero-phase circuits in Figures 2 and 3, along with the fault point resistance Rf in Figures 2 to 4, are collectively defined as impedance Zf. Specifically, impedance Zf is the sum of the fault point resistance Rf, the combined impedance of the inverted-phase circuits on the local and other ends as seen from the fault point, and the combined impedance of the zero-phase circuits on the local and other ends as seen from the fault point. As a result, as shown in the equivalent circuit of Figure 5(a), the equivalent circuit during a forward fault can be represented by a single positive-phase circuit regardless of the type of fault (e.g., ground fault, two-phase short-circuit fault, three-phase short-circuit fault).

[0031] The same applies to rear faults. Specifically, the combined impedance of the inverted-phase circuit, the combined impedance of the zero-phase circuit, and the fault point resistance Rf during a rear fault are combined and defined as impedance Zf. This allows the equivalent circuit during a rear fault to be represented by a single positive-phase circuit, regardless of the type of fault, as shown in the equivalent circuit in Figure 5(b).

[0032] Therefore, referring to Figure 5(a), if a forward fault occurs, the following equation (1) holds true for the change in positive-sequence voltage ΔV1 and the change in positive-sequence current ΔI1. Referring to Figure 5(b), if a backward fault occurs, the following equation (2) holds true for the changes in ΔV1 and ΔI1.

[0033] ΔV1 / ΔI1=-ZS1 …(1) ΔV1 / ΔI1=ZL1+ZR1 …(2) Let θ1 (hereinafter also referred to as "impedance angle θ1") be the angle of the positive-sequence back impedance ZS1 on the local end. Also, let θ2 (hereinafter also referred to as "impedance angle θ2") be the angle of the combined impedance "ZL1+ZR1" which is the positive-sequence back impedance of the line ZL1 and the positive-sequence back impedance ZR1 on the other end. Since power transmission lines and transformers behind relays generally have strong reactance, the impedance angles θ1 and θ2 will be in the range of, for example, 80° to 89°.

[0034] (Direction determination using vectors) Based on equations (1) and (2) obtained from the equivalent circuit explained in Figure 5, the vector diagram shown in Figure 6 is obtained.

[0035] Figure 6 is a diagram illustrating the positional relationship between the positive-sequence voltage change vector and the positive-sequence current change vector. Here, the vector representing the change in positive-sequence voltage is referred to as the "positive-sequence voltage change vector ΔV1," and the vector representing the change in positive-sequence current is referred to as the "positive-sequence current change vector ΔI1." In this case, Figure 6(a) shows the relationship between the positive-sequence voltage change vector ΔV1 and the positive-sequence current change vector ΔI1 during a forward fault. Figure 6(b) shows the relationship between the positive-sequence voltage change vector ΔV1 and the positive-sequence current change vector ΔI1 during a rearward fault.

[0036] Here, the vector of the positive-sequence current I1 is calculated from the time-series instantaneous value data of each phase current detected by CT60. The vector of the positive-sequence voltage V1 is calculated from the time-series instantaneous value data of each phase voltage detected by VT70. For example, the time-series instantaneous value data of the current I from time (tn) to time (t) is I(tn),...I(t-1),I(t). Similarly, the time-series instantaneous value data of the voltage V from time (tn) to time (t) is V(tn),...,V(t-1),V(t). Here, n represents the sampling number corresponding to the number of positive integer cycles.

[0037] In this case, the change in positive-sequence current at time t is defined as "ΔI1(t) = I1(t) - I1(tn)". The change in positive-sequence voltage at time t is defined as "ΔV1(t) = V1(t) - V1(tn)". From this, the positive-sequence voltage change vector ΔV1 and the positive-sequence current change vector ΔI1 are calculated. For example, if the number of positive integer cycles is 2, then n is the number of samples corresponding to the period of those 2 cycles. If the number of samples corresponding to 1 cycle is "12", then "n = 24". In this case, the change is only valid for 2 cycles, but in a typical fault, 2 cycles is sufficient for operation. Considering the change in this way, even if there is load current, the effect of the load current can be eliminated, and the situation will be the same as if there were no load current. Note that other changes in current or voltage at time t are defined in the same way as above. Specifically, the change ΔD at time t is defined as "ΔD(t) = D(t) - D(tn)".

[0038] Referring to Figure 6(a), the relationship between the positive-sequence voltage change vector ΔV1, the positive-sequence current change vector ΔI1, and the impedance angle θ1 is based on equation (1) obtained from the equivalent circuit in Figure 5(a). The impedance angle θ1 is, for example, 80°. In this case, angle φ1 is set to 170° (=80°+90°) and angle φ2 is set to 350° (=80°+270°). Here, let "α" be the phase angle of the positive-sequence voltage change vector ΔV1 (i.e., ΔV1 / ΔI1) with respect to the positive-sequence current change vector ΔI1. When a forward fault occurs, the phase angle α satisfies the relationship "φ1 < α < φ2". In Figure 6(a), the range from angle φ1 to angle φ2 is shown as a shaded area. This is also the case in Figure 6(b).

[0039] Referring to Figure 6(b), the relationship between the positive-sequence voltage change vector ΔV1, the positive-sequence current change vector ΔI1, and the impedance angle θ2 is based on equation (2) obtained from the equivalent circuit in Figure 5(b). The impedance angle θ2 is, for example, 80°. As explained above, angle φ1 is 170° and angle φ2 is 350°. Also, the phase angle α is equal to the impedance angle θ2. In the case of a back fault, since "α < φ1", the phase angle α does not satisfy the relationship "φ1 < α < φ2".

[0040] Based on the above, the protective relay 100 determines that a fault point exists ahead if the phase angle α of the positive-sequence voltage change vector ΔV1 (i.e., ΔV1 / ΔI1) with respect to the positive-sequence current change vector ΔI1 satisfies the relationship “φ1 < α < φ2”. The shaded area in Figure 6 is the operating area of ​​the direction determination element included in the protective relay 100 (for example, corresponding to the direction determination unit described later).

[0041] Furthermore, angles φ1 and φ2 may be set in a configuration that takes into account the effect of CT saturation. Figure 7 shows the current waveforms when the CT is saturated and when it is not saturated. Referring to Figure 7, waveform 301 shows the CT secondary current when the CT is not saturated, waveform 302 shows the CT secondary current when the CT is saturated, and waveform 303 shows the current waveform after filtering the CT secondary current when the CT is saturated for relay calculations.

[0042] Focusing on the falling edge of the current, the falling edge of waveform 302 during CT saturation is to the left of waveform 301 during CT non-saturation, so the phase appears to be ahead on the relay side. Therefore, when phase calculation is performed on waveform 303 after filtering, the phase is ahead of the actual phase. Also, waveform 303 has a smaller amplitude than waveform 301 during CT non-saturation.

[0043] Figure 8 is a diagram illustrating the positional relationship between the positive-sequence voltage change vector and the positive-sequence current change vector when CT saturation is considered. Specifically, Figure 8 shows the relationship between the positive-sequence voltage change vector ΔV1 and the positive-sequence current change vector ΔI1 in the event of a forward fault.

[0044] Referring to Figure 8, the positive-sequence current change vector ΔI1 when the CT is saturated is phase-leading compared to the positive-sequence current change vector ΔI1 when the CT is not saturated. As described above, the operating region of the direction determination element for forward faults is set to angles φ1 (=170°) to φ2 (=350°). The shaded region in Figure 8 corresponds to the operating region of the direction determination element when there is no CT saturation.

[0045] Here, if we assume that the positive-sequence current change vector ΔI1 advances by 30° when the CT saturates, the region on the angle φ2 side approaches the positive-sequence voltage change vector ΔV1 during a rear fault, which is in almost the opposite phase to the positive-sequence voltage change vector ΔV1 during a front fault, as shown by the dashed line in Figure 8. Therefore, if CT saturation occurs during a rear fault, the front fault region approaches the positive-sequence voltage change vector ΔV1 during a rear fault, increasing the risk of misidentifying a rear fault as a front fault. Accordingly, misidentification can be prevented by, for example, reducing the angle φ2 (for example, setting φ2 = 320°). In distance relays, it is especially important to prevent misidentification of a rear fault as a front fault, as this tends to cause malfunctions.

[0046] On the other hand, regarding the φ1 angle, when the CT saturates, the angle between the positive-sequence voltage change vector ΔV1 during a forward fault and the angle φ1 becomes smaller, and the operating region for forward faults tends to narrow. Therefore, even if there is CT saturation during a rear fault, there is no risk of misjudgment. In this case, there is a possibility that a forward fault may not be detected when a forward fault occurs, but the CT saturation is attenuated by the DC time constant included in the fault current. For this reason, even if there is a time delay during CT saturation, it is still detected as a forward fault, so it does not pose a problem.

[0047] Therefore, to prevent misjudgment of the direction determination element, angle φ1 is maintained, and the range of angle φ2 is narrowed. For example, angle φ2 is set to 320°, which is 30° smaller than the angle when CT is not saturated (i.e., 350°). Angles φ1 and φ2 may be angles other than those mentioned above.

[0048] (modified version) As described above, the protection relay device 100 can determine whether a fault point exists ahead based on the phase relationship between the positive-phase voltage change vector ΔV1 and the positive-phase current change vector ΔI1. However, in order to accurately obtain the phase relationship, it is preferable that |ΔI1| indicating the effective value of the positive-phase current change vector ΔI1 and |ΔV1| indicating the effective value of the positive-phase voltage change vector ΔV1 are both above a certain level. For example, it is necessary that |ΔI1| is above the threshold value Ki (e.g., 10% of the CT rated current), and |ΔV1| is above the threshold value Kv (e.g., relay input voltage: 1 - 5V). Hereinafter, |P| indicates the effective value of the vector P.

[0049] Here, when a forward fault occurs, "ΔV1 = -ZS1 * ΔI1" holds according to Equation (1). The symbol "*" indicates the multiplication symbol. Therefore, when |ΔI1| is small (however, |ΔI1| > Ki) due to a fault point existing far away from the protection relay device 100, etc., and the positive-phase behind impedance ZS1 is small, |ΔV1| becomes small. Specifically, there may be a case where "|ΔV1| < Kv". In this case, paying attention to the fact that the phase of the positive-phase voltage change vector ΔV1 is almost the same as the phase of the reverse vector "-V1" of the positive-phase voltage vector V1, the protection relay device 100 may be configured to perform direction determination using the reverse vector "-V1" with a large effective value instead of the positive-phase voltage change vector ΔV1.

[0050] Specifically, let the phase angle of the reverse vector "-V1" (i.e., -V1 / ΔI1) with respect to the positive-phase current change vector ΔI1 be "α1". The protection relay device 100 determines that a fault point exists ahead when the phase angle α1 satisfies the relational expression "φ1 < α1 < φ2".

[0051] Figure 9 is a diagram for explaining that the positive-phase voltage change vector and the reverse vector of the positive-phase voltage vector are almost in the same phase. Figure 9(a) is a vector diagram showing the voltage relationship before and after an A-phase ground fault. Figure 9(b) is a vector diagram showing the voltage relationship before and after a two-phase short circuit fault of phases B and C.

[0052] In Figure 9, “Vax”, “Vbx”, “Vcx”, and “V1x” represent the vectors of the A-phase voltage, B-phase voltage, C-phase voltage, and positive-sequence voltage, respectively, before the failure. “Va”, “Vb”, “Vc”, and “V1” represent the vectors of the A-phase voltage, B-phase voltage, C-phase voltage, and positive-sequence voltage, respectively, at the time of the failure (i.e., after the failure). “ΔV1” represents the positive-sequence voltage change vector before and after the failure. As shown in Figures 9(a) and 9(b), it can be seen that the positive-sequence voltage change vector ΔV1 is almost in phase with the inverse vector of the positive-sequence voltage vector V1.

[0053] <Functional Configuration> Figure 10 is a block diagram showing an example of the functional configuration of a protective relay device according to Embodiment 1. Referring to Figure 10, the protective relay device 100 includes, as its main functional configuration, an electrical quantity acquisition unit 101, a current change vector calculation unit 103, a voltage change vector calculation unit 105, a phase angle calculation unit 107, a direction determination unit 109, a distance determination unit 111, and an output control unit 113. These functions are realized, for example, by a processing circuit included in the protective relay device 100. The processing circuit may be dedicated hardware, or it may be a CPU 32 that executes a program stored in the internal memory (e.g., ROM 33) of the protective relay device 100. If the processing circuit is dedicated hardware, it may be composed of, for example, an FPGA, an ASIC, or a combination thereof.

[0054] The electrical quantity acquisition unit 101 acquires the time-series instantaneous values ​​of current detected in the power system and the time-series instantaneous values ​​of voltage detected in the power system. Specifically, the electrical quantity acquisition unit 101 acquires time-series instantaneous values ​​(i.e., current time-series instantaneous values) sampled from each phase current (e.g., A-phase current, B-phase current, C-phase current) of the transmission line 7 detected by the CT60, and time-series instantaneous values ​​(i.e., voltage time-series instantaneous values) sampled from each phase voltage (e.g., A-phase voltage, B-phase voltage, C-phase voltage) of the busbar 8 detected by the VT70. The above sampling and A / D conversion are performed by the signal conversion unit 20 described above.

[0055] The current change vector calculation unit 103 calculates the current change vector of the protected line (e.g., transmission line 7) included in the power system from the instantaneous current time series values. Specifically, the current change vector calculation unit 103 calculates the change vector (e.g., positive-sequence current change vector ΔI1) of the positive-sequence current I1 obtained from the phase currents of the protected line (e.g., transmission line 7).

[0056] The voltage change vector calculation unit 105 calculates the voltage change vector of the busbar 8 connected to the protected line (e.g., transmission line 7) from the instantaneous voltage time series values. Specifically, the voltage change vector calculation unit 105 calculates the change vector of the positive-sequence voltage V1 obtained from the phase voltages of each phase of the busbar 8 (e.g., positive-sequence voltage change vector ΔV1).

[0057] The phase angle calculation unit 107 calculates a reference phase angle based on the current change vector and the voltage change vector. Specifically, the phase angle calculation unit 107 calculates the phase angle α of the positive-sequence voltage change vector ΔV1 relative to the positive-sequence current change vector ΔI1 as the reference phase angle.

[0058] The direction determination unit 109 determines the direction of the fault point in the protected line (e.g., transmission line 7) based on the reference phase angle, a first angle (e.g., angle φ1), and a second angle (e.g., angle φ2) that is greater than the first angle. Specifically, the direction determination unit 109 determines whether the reference phase angle is included within an angle range H1 that is greater than angle φ1 and less than angle φ2 (e.g., whether φ1 < α < φ2 is satisfied). If the reference phase angle is included within the angle range H1 (e.g., φ1 < α < φ2 is satisfied), the direction determination unit 109 determines that the fault point is located in front of the protective relay device 100. For example, the direction determination unit 109 outputs a forward determination signal indicating that the fault point is located in front.

[0059] In other situations, the phase angle calculation unit 107 calculates the inverse vector "-V1" of the positive-sequence voltage vector V1 of the busbar 8. If the effective value of the positive-sequence voltage change vector ΔV1 is less than the threshold Kv, the phase angle calculation unit 107 calculates the phase angle α1 of the inverse vector "-V1" for the positive-sequence voltage change vector ΔV1 as the reference phase angle instead of the phase angle α. In this case, the direction determination unit 109 outputs a forward determination signal if the phase angle α1 is included in the angle range H1 (for example, satisfying φ1 < α1 < φ2). That is, the direction determination unit 109 determines that a fault point exists in front. It is assumed that the effective value of the positive-sequence current change vector ΔI1 (i.e., |ΔI1|) is greater than or equal to the threshold Ki.

[0060] The distance determination unit 111 calculates the impedance to the fault point using a predetermined calculation method based on the current data and voltage data acquired by the electrical quantity acquisition unit 101. The distance determination unit 111 then determines whether the calculated impedance is within a set value.

[0061] The output control unit 113 outputs an open command (e.g., a trip signal) to the circuit breaker 50 based on the determination results of the direction determination unit 109 and the distance determination unit 111. Specifically, if the direction determination unit 109 determines that the fault point is located ahead, and the distance determination unit 111 determines that the impedance is within the set value, the output control unit 113 outputs an open command to the circuit breaker 50.

[0062] <Advantages> According to Embodiment 1, the direction of the fault point is determined using the positive-sequence voltage change vector and the positive-sequence current change vector. The protection control device according to Embodiment 1 can perform the fault point direction determination by calculating for one phase (i.e., the positive-sequence phase), thus reducing the processing load in the direction determination.

[0063] Embodiment 2. In Embodiment 1 described above, a configuration was described in which the direction of the fault location is determined based on changes in positive-sequence voltage and positive-sequence current. In Embodiment 2, a configuration will be described in which the direction of the fault location is determined based on changes in line voltage and line current. The overall configuration according to Embodiment 2 is the same as the <overall configuration> of Embodiment 1.

[0064] <Method for determining the direction of the fault point> (Equivalent circuit) Figure 11 shows the equivalent circuit for a single-phase ground fault according to Embodiment 2. Specifically, the equivalent circuit shown in Figure 11 is an equivalent circuit for a single-phase ground fault using the symmetrical coordinate method, which involves virtually moving the power supply to the fault point and generating a fault current. Typically, Figure 11 shows the equivalent circuit when a ground fault occurs in phase A of a single transmission line, where phases A, B, and C occur ahead. Therefore, the equivalent circuit shown in Figure 11 is basically the same as that in Figure 2.

[0065] Referring to Figure 11, “E” is the power supply voltage when the power supply is virtually moved to the fault point so that the fault current flows toward the fault point. “ΔIF1”, “ΔIF2”, and “ΔIF0” represent the current changes flowing from the fault point of the positive-sequence circuit, negative-sequence circuit, and zero-sequence circuit, respectively. The other signs are the same as those explained in Figure 2. From the equivalent circuit in Figure 11, the following equations (3) and (4) hold for the change amounts ΔI1, ΔI2, and ΔI0.

[0066] ΔI1=ΔI2=ΔIF1*(ZR1 / (ZS1+ZL1+ZR1)) …(3) ΔI0=ΔIF0*(ZR0 / (ZS0+ZL0+ZR0)) …(4) Furthermore, since "ΔIF1=ΔIF2=ΔIF0", if we define "ΔI1=ΔI2=I", then the following equation (5) holds. Note that the impedance of the positive-sequence circuit is equal to the impedance of the negative-sequence circuit, but the impedance of the zero-sequence circuit is different from the impedances of the positive-sequence and negative-sequence circuits.

[0067] ΔI0=I*(ZR0 / ZR1)*((ZS1+ZL1+ZR1) / (ZS0+ZL0+ZR0))=I*P …(5) In equation (5), we have set “P=(ZR0 / ZR1)*((ZS1+ZL1+ZR1) / (ZS0+ZL0+ZR0))”. If we denote the vector operator as “a”, the change in A-phase current ΔIa, the change in B-phase current ΔIb, and the change in C-phase current ΔIc are expressed by the following equations (6), (7), and (8), respectively.

[0068] ΔIa=ΔI0+ΔI1+ΔI2 =I*(2+P) …(6) ΔIb = ΔI0 + a 2 *ΔI1+a*ΔI2=I*(P-1) …(7) ΔIc = ΔI0 + a * ΔI1 + a 2 *ΔI² = I*(P-1) …(8) Therefore, for the changes in line current between phases AB, ΔIab, CA, and BC of the power system, the following conditions hold: "ΔIab = 3I", "ΔIca = -3I", and "ΔIbc = 0". From this, the change in line current between healthy phases (in this case, between phases B and C) is zero.

[0069] Next, using the fact that "ΔI1=ΔI2" and "ZS1=ZS2", the following equations (9) and (10) hold for the changes ΔV1, ΔV2, and ΔV0.

[0070] ΔV1=ΔV2=-ΔI1*ZS1=-I*ZS1 …(9) ΔV0=-ΔI0*ZS0=-I*P*ZS0 …(10) Furthermore, the change in the A-phase voltage ΔVa, the change in the B-phase voltage ΔVb, and the change in the C-phase voltage ΔVc are expressed by the following equations (11), (12), and (13), respectively.

[0071] ΔVa=ΔV0+ΔV1+ΔV2=-I*(2*ZS1+P*ZS0) …(11) ΔVb = ΔV0 + a 2 *ΔV1+a*ΔV2=-I*(P*ZS0-ZS1)…(12) ΔVc = ΔV0 + a * ΔV1 + a 2 *ΔV2=-I*(P*ZS0-ZS1)…(13) From this, the following equations hold true for the change in line voltage ΔVab of phase AB, the change in line voltage ΔVca of phase CA, and the change in line voltage ΔVbc of phase BC: "ΔVab = -3I * ZS1", "VIca = -3I * ZS1", and "ΔVbc = 0".

[0072] Therefore, the equation "ΔVab / ΔIab=-ZS1" holds true for the AB phase, and "ΔVca / ΔIca=-ZS1" holds true for the CA phase.

[0073] Furthermore, if the fault point resistance is Rf, then equation (14) holds, and therefore equation (15) holds for "I".

[0074] ΔIF1=E / (2*((ZS1+ZL1) / ZR1)+((ZS0+ZL0) / ZR0)+Rf) …(14) I=(E / (2*((ZS1+ZL1) / ZR1)+((ZS0+ZL0) / ZR0)+Rf))*(ZR1 / (ZS1+ZL1+ZR1)) …(15) From equation (15), the phase of “I” is affected by the fault point resistance Rf. However, from the above relationship, it can be understood that “ΔVab / ΔIab” and “ΔVca / ΔIca” are not affected by the fault point resistance Rf.

[0075] (Direction determination in the event of a single-phase ground fault) Figure 12 is a diagram showing an example of the functional configuration of the direction determination unit according to Embodiment 2. Specifically, Figure 12 shows the functional configuration of the direction determination unit 109 according to Embodiment 2, which is used to perform direction determination in the event of a single-phase ground fault.

[0076] Referring to Figure 12, the direction determination unit 109 includes an AB phase determination unit 201, a BC phase determination unit 202, a CA phase determination unit 203, and AND circuits 211 to 213.

[0077] The AB phase determination unit 201 outputs a determination signal Sab with a value of "1" when the conditions based on the change amounts ΔVab and ΔIab are met, and outputs a determination signal Sab with a value of "0" when the conditions are not met. The BC phase determination unit 202 outputs a determination signal Sbc with a value of "1" when the conditions based on the change amounts ΔVbc and ΔIbc are met, and outputs a determination signal Sbc with a value of "0" when the conditions are not met. The CA phase determination unit 203 outputs a determination signal Sca with a value of "1" when the conditions based on the change amounts ΔVca and ΔIca are met, and outputs a determination signal Sca with a value of "0" when the conditions are not met. The determination methods of the AB phase determination unit 201, the BC phase determination unit 202, and the CA phase determination unit 203 will be described below.

[0078] Figure 13 is a vector diagram showing the relationship between current and voltage before and after a single-phase ground fault. Typically, the example in Figure 13 assumes a single-phase ground fault in phase A occurring ahead. In Figure 13, "Vax" represents the vector of the phase A voltage before the fault. "Va," "Vb," and "Vc" represent the vectors of the phase A, B, and C voltages at the time of the fault, respectively. "Vabx" and "Vcax" represent the vectors of the A-B and C phase line voltages and the CA phase line voltages before the fault, respectively. "Vab" and "Vca" represent the vectors of the A-B and C phase line voltages and the CA phase line voltages at the time of the fault, respectively. Note that in reality, during a phase A ground fault, the B-phase voltage vector Vb and C-phase voltage vector Vc of the healthy phase change slightly, but this change is small compared to the change in the A-phase voltage vector Va, and is therefore ignored in Figure 13.

[0079] In FIG. 13, “ΔVab” represents the vector of the change in the line voltage between phases A and B before and after the fault (hereinafter, also referred to as “line voltage change vector ΔVab”), and “ΔVca” represents the vector of the change in the line voltage between phases C and A before and after the fault (hereinafter, also referred to as “line voltage change vector ΔVca”). “ΔIab” represents the vector of the change in the line current between phases A and B before and after the fault (hereinafter, also referred to as “line current change vector ΔIab”), and “ΔIca” represents the vector of the change in the line current between phases C and A before and after the fault (hereinafter, also referred to as “line current change vector ΔIca”). “ΔIa” represents the vector of the change in the phase A current. Also, the vector of the change in the line current between phases B and C before and after the fault is also referred to as “line current change vector ΔIbc”.

[0080] During a single-phase-to-ground fault of phase A, |ΔIab| and |ΔIca| become greater than or equal to the threshold value Ki, and |ΔIbc| becomes less than the threshold value Ki. That is, |ΔIab|≧Ki, |ΔIbc|<Ki, and |ΔIca|≧Ki hold.

[0081] As shown in FIG. 13, the line voltage change vector ΔVab, the inverse vector “-ΔVca” of the line voltage change vector ΔVca, and the phase A voltage change vector ΔVa are in the same phase. The line current change vector ΔIab, the inverse vector “-ΔIca” of the line current change vector ΔIca, and the phase A current change vector ΔIa are in the same phase.

[0082] As explained using the equivalent circuit of FIG. 11, since “ΔVab / ΔIab=-ZS1” holds, the reference vector “ΔIab*ZS1” obtained by multiplying the current change vector ΔIab by the positive-sequence behind impedance ZS1 and the line voltage change vector ΔVab have opposite phases. Similarly, since “ΔVca / ΔIca=-ZS1” holds, the reference vector “ΔIca*ZS1” obtained by multiplying the current change vector ΔIca by the positive-sequence behind impedance ZS1 and the line voltage change vector ΔVca have opposite phases.

[0083] Thus, in the event of an A-phase ground fault, the line voltage change vector and the reference vector are in a near-opposite phase relationship. The direction determination unit 109 of the protective relay 100 uses this to determine the direction of the ground fault point. Specifically, the AB-phase determination unit 201 of the direction determination unit 109 outputs a determination signal Sab with a value of "1" if the phase angle θab of the line voltage change vector ΔVab with respect to the reference vector "ΔIab*ZS1" satisfies the relationship "φ3 < θab < φ4". For example, φ3 is 90° and φ4 is 275°. Here, the determination signal Sab with a value of "1" indicates that there is a possibility that the fault point is located in front of the protective relay 100. In the following, the determination signal Sab with a value of "1" may be referred to as the "forward determination signal Sab" for convenience. The same applies to the other determination signals Sbc and Sca.

[0084] As explained in the <modified example> of Embodiment 1, in order to accurately determine the phase relationship of each vector, the effective value of each vector must be above a certain level. For this reason, for the AB phase, it is preferable that |ΔIab| is above the threshold Ki and |ΔVab| is above the threshold Kv. However, if |ΔVab| is below the threshold Kv, another vector in phase with the line voltage change vector ΔVab may be used instead of the line voltage change vector ΔVab. Specifically, as shown in Figure 13, the line voltage change vector ΔVab is in phase with the A phase voltage change vector ΔVa. And the A phase voltage change vector ΔVa is in phase with the inverse vector "-Va" of the A phase voltage vector Va.

[0085] Therefore, if |ΔVab| is less than the threshold Kv, the AB phase determination unit 201 determines whether the phase angle θabx of the inverse vector "-Va" with respect to the reference vector "ΔIab*ZS1" satisfies the relationship "φ3 < θabx < φ4". If the relationship is true, the AB phase determination unit 201 outputs a forward determination signal Sab.

[0086] Next, the CA phase determination unit 203 of the direction determination unit 109 outputs a determination signal Sca (i.e., a forward determination signal Sca) with a value of "1" if the phase angle θca of the line voltage change vector ΔVca with respect to the reference vector "ΔIca*ZS1" satisfies the relationship "φ3 < θca < φ4" for the CA phase.

[0087] For the CA phase as well, it is preferable that |ΔIca| is greater than or equal to the threshold Ki and |ΔVca| is greater than or equal to the threshold Kv. Here, as shown in Figure 13, the line voltage change vector ΔVca is in phase with the inverse vector of the A phase voltage change vector ΔVa. And the inverse vector of the A phase voltage change vector ΔVa is in phase with the A phase voltage vector Va. Therefore, if |ΔVca| is less than the threshold Kv, the CA phase determination unit 203 determines whether the phase angle θcax of the A phase voltage vector Va with respect to the reference vector "ΔIca*ZS1" satisfies the relationship "φ3 < θcax < φ4". If the CA phase determination unit 203 satisfies this relationship, it outputs a forward determination signal Sca.

[0088] In the event of an A-phase ground fault, the change in line current and line voltage of the BC phases is zero. Therefore, the BC phase determination unit 202 of the direction determination unit 109 outputs a determination signal Sbc with a value of "0" without performing the above determination for the BC phase. In other words, the BC phase determination unit 202 does not output a forward determination signal Sbc.

[0089] In addition, similar to Embodiment 1, the angles φ3 and φ4 may be set considering the effect of CT saturation. Specifically, in order to prevent misjudgment of the direction determination element when CT saturation occurs, the range from angle φ3 to angle φ4 is narrowed by making angle φ4 smaller. For example, angle φ4 is set to 245°, which is 30° smaller than when CT is not saturated. The angles φ3 and φ4 may be angles other than those mentioned above.

[0090] Thus, when a ground fault of phase A occurs in front of the protection relay device 100, |ΔIab|≧Ki, |ΔIbc|<Ki, and |ΔIca|≧Ki hold, and the value of the determination signal Sab is "1", the value of the determination signal Sbc is "0", and the value of the determination signal Sca is "1".

[0091] In FIG. 13, the single-phase ground fault of phase A has been described. However, the single-phase ground faults of phases B and C can be considered in the same way. Specifically, when a ground fault of phase B occurs in front, |ΔIab|≧Ki, |ΔIbc|≧Ki, and |ΔIca|<Ki hold, and the value of the determination signal Sab is "1", the value of the determination signal Sbc is "1", and the value of the determination signal Sca is "0". When a ground fault of phase C occurs in front, |ΔIab|<Ki, |ΔIbc|≧Ki, and |ΔIca|≧Ki hold, and the value of the determination signal Sab is "0", the value of the determination signal Sbc is "1", and the value of the determination signal Sca is "1".

[0092] Referring to FIG. 12 again, the AND circuit 211 performs an AND operation on the output value of the AB-phase determination unit 201, the value with the logical level of the output of the BC-phase determination unit 202 inverted, and the output value of the CA-phase determination unit 203. Specifically, when the value of the determination signal Sab is "1", the value of the determination signal Sbc is "0", and the value of the determination signal Sca is "1", the AND circuit 211 outputs a signal Sa with the value "1". As described above, when a ground fault of phase A occurs in front of the protection relay device 100, the value of the determination signal Sab is "1", the value of the determination signal Sbc is "0", and the value of the determination signal Sca is "1". Therefore, the signal Sa with the value "1" indicates that the single-phase ground fault point of phase A exists in front of the protection relay device 100.

[0093] The AND circuit 212 performs an AND operation on the output value of the AB-phase determination unit 201, the output value of the BC-phase determination unit 202, and the value with the logical level of the output of the CA-phase determination unit 203 inverted. Specifically, when the value of the determination signal Sab is "1", the value of the determination signal Sbc is "1", and the value of the determination signal Sca is "0", the AND circuit 212 outputs a signal Sb with the value "1". The signal Sb with the value "1" indicates that the single-phase ground fault point of phase B exists in front of the protection relay device 100.

[0094] The AND circuit 213 performs an AND operation between the inverted logic level of the output of the AB phase determination unit 201, the output value of the BC phase determination unit 202, and the output value of the CA phase determination unit 203. Specifically, when the value of the determination signal Sab is "0", the value of the determination signal Sbc is "1", and the value of the determination signal Sca is "1", the AND circuit 213 outputs a signal Sc with the value "1". A signal Sc with the value "1" indicates that the one-phase ground fault point of the C phase is located in front of the protective relay device 100.

[0095] (Directional determination in the event of a short-circuit fault or ground fault involving two or more phases) Figure 14 shows another example of the functional configuration of the direction determination unit according to Embodiment 2. Specifically, Figure 14 shows the functional configuration of the direction determination unit 109 according to Embodiment 2 for performing direction determination in the event of a short-circuit fault or ground fault in the event of a two-phase or more-phase short-circuit fault.

[0096] Referring to Figure 14, the direction determination unit 109 includes an AB phase determination unit 201x, a BC phase determination unit 202x, and a CA phase determination unit 203x.

[0097] The AB phase determination unit 201x outputs a determination signal Sabx with a value of "1" if the conditions based on the change amounts ΔVab and ΔIab are met, and outputs a determination signal Sabx with a value of "0" if the conditions are not met. The BC phase determination unit 202 outputs a determination signal Sbcx with a value of "1" if the conditions based on the change amounts ΔVbc and ΔIbc are met, and outputs a determination signal Sbcx with a value of "0" if the conditions are not met. The CA phase determination unit 203 outputs a determination signal Scax with a value of "1" if the conditions based on the change amounts ΔVca and ΔIca are met, and outputs a determination signal Scax with a value of "0" if the conditions are not met.

[0098] Here, the determination methods of the AB phase determination unit 201x, the BC phase determination unit 202x, and the CA phase determination unit 203x will be explained.

[0099] Figure 15 is a vector diagram showing the relationship between current and voltage before and after a short-circuit fault. Typically, the example in Figure 15 assumes a two-phase short-circuit fault in the B and C phases occurring in front of the fault. In Figure 15, "Vbx" and "Vcx" represent the vectors of the B-phase voltage and C-phase voltage before the fault, respectively. "Vbc" represents the vector of the B and C phase line voltage at the time of the fault. "ΔVbc" represents the vector of the change in the B and C phase line voltage before and after the fault (hereinafter also referred to as "line voltage change vector ΔVbc"). "ΔIbc" represents the vector of the change in the B and C phase line current before and after the fault (hereinafter also referred to as "line current change vector ΔIbc"). The other vectors are as explained in Figure 12.

[0100] In the event of a short-circuit fault or ground fault involving two or more phases, |ΔIab|, |ΔIbc|, and |ΔIca| will be greater than or equal to the threshold Ki. That is, |ΔIab|≧Ki, |ΔIbc|≧Ki, and |ΔIca|≧Ki will hold true.

[0101] Here, similar to the single-phase ground fault described in Figure 13, in the case of a short-circuit fault, the reference vector obtained by multiplying the line-to-line current change vector by the positive-sequence back impedance ZS1 and the line-to-line voltage change vector are in opposite phase. Specifically, the reference vector "ΔIbc*ZS1" and the line-to-line voltage change vector ΔVbc are in opposite phase. Similarly, the reference vector "ΔIab*ZS1" and the line-to-line voltage change vector ΔVab are in opposite phase, and the reference vector "ΔIca*ZS1" and the line-to-line voltage change vector ΔVca are in opposite phase. Note that "ΔVab+ΔVbc+ΔVca=0".

[0102] In the event of a short-circuit fault, the line voltage change vector and the above-mentioned reference vector are in a near-opposite phase relationship. The direction determination unit 109 uses this to determine the direction of the fault point. Specifically, the BC phase determination unit 202x of the direction determination unit 109 outputs a determination signal Sbcx with a value of "1" if the phase angle θbc of the BC phase satisfies the relationship "φ3 < θbc < φ4". Similarly, in the event of a two-phase ground fault in the BC phase, the phase angle θbc also satisfies the relationship "φ3 < θbc < φ4". Therefore, a determination signal Sbcx with a value of "1" indicates that the two-phase short-circuit fault point or two-phase ground fault point of the BC phase is located in front of the protective relay device 100. Hereinafter, the determination signal Sbcx with a value of "1" will also be referred to as the "forward determination signal Sbcx".

[0103] Furthermore, considering the phase determination accuracy, it is preferable that |ΔIbc| is greater than or equal to the threshold Ki and |ΔVbc| is greater than or equal to the threshold Kv. However, if |ΔVbc| is less than the threshold Kv, another vector in phase with the line voltage change vector ΔVbc may be used instead of the line voltage change vector ΔVbc. As shown in Figure 15, in the case of a BC phase short-circuit fault, the line voltage change vector ΔVbc is in phase with the inverse vector "-Vbc" of the line voltage vector Vbc. Therefore, if |ΔVbc| is less than the threshold Kv, the BC phase determination unit 202x determines whether the phase angle θbc1 of the inverse vector "-Vbc" with respect to the reference vector "ΔIbc*ZS1" satisfies the relationship "φ3 < θbc1 < φ4". If the relationship is true, the BC phase determination unit 202x outputs a forward determination signal Sbcx.

[0104] Thus, for the BC phase, if a fault exists in front of the protective relay device 100, the value of the determination signal Sbcx becomes "1". Although Figure 15 describes the BC phase, the same considerations can be applied to the AB phase and CA phase. Specifically, for the AB phase, if a fault exists in front (for example, a two-phase short-circuit fault or a ground fault), the AB phase determination unit 201x determines that the phase angle θab satisfies the relationship "φ3 < θab < φ4" and outputs a determination signal Sabx with a value of "1" (i.e., forward determination signal Sabx). For the CA phase, if a fault exists in front, the CA phase determination unit 203x determines that the phase angle θca satisfies the relationship "φ3 < θca < φ4" and outputs a determination signal Scax with a value of "1" (i.e., forward determination signal Scax).

[0105] In the event of a three-phase short-circuit fault or a three-phase ground fault, the values ​​of the judgment signals Sabx, Sbcx, and Scax will all be "1".

[0106] (summary) The direction determination method using the line voltage change vector and line current change vector explained in Figures 11 to 15 can be summarized as follows.

[0107] First, we will explain the determination method when |ΔIab|≧Ki, |ΔIbc|≧Ki, and |ΔIca|≧Ki are all true. In this case, the direction determination unit 109 performs direction determination using the functional configuration shown in Figure 14. In this case, there is a possibility that either a short-circuit fault or a ground fault of two or more phases (i.e., two or three phases) has occurred.

[0108] The direction determination of the AB phase will be described. When |ΔVab| ≧ Kv, the AB phase determination unit 201x outputs a forward determination signal Sabx when the phase angle θab of the line voltage change vector ΔVab with respect to the reference vector "ΔIab*ZS1" satisfies "φ3 < θab < φ4". That is, the AB phase determination unit 201x determines that a fault point (for example, a short-circuit fault point or a ground fault point including phase A and phase B) exists in front in the AB phase. Next, when |ΔVab| < Kv, the AB phase determination unit 201x determines that a fault point exists in front in the AB phase when the phase angle θab1 of the inverse vector "-Vab" with respect to the reference vector "ΔIab*ZS1" satisfies "φ3 < θab1 < φ4".

[0109] The direction determination of the BC phase will be described. When |ΔVbc| ≧ Kv, the BC phase determination unit 202x outputs a forward determination signal Sbcx when the phase angle θbc satisfies "φ3 < θbc < φ4". That is, the BC phase determination unit 202x determines that a fault point (for example, a short-circuit fault point or a ground fault point including phase B and phase C) exists in front in the BC phase. When |ΔVbc| < Kv, the BC phase determination unit 202x determines that a fault point exists in front in the BC phase when the phase angle θbc1 satisfies "φ3 < θbc1 < φ4".

[0110] The direction determination of the CA phase will be described. When |ΔVca| ≧ Kv, the CA phase determination unit 203x outputs a forward determination signal Scax when the phase angle θca satisfies "φ3 < θca < φ4". That is, the CA phase determination unit 203x determines that a fault point (for example, a short-circuit fault point or a ground fault point including phase C and phase A) exists in front in the CA phase. When |ΔVca| < Kv, the CA phase determination unit 203x determines that a fault point exists in front in the CA phase when the phase angle θca1 of the inverse vector "-Vca" with respect to the reference vector "ΔIca*ZS1" satisfies "φ3 < θca1 < φ4".

[0111] Next, a determination method when only one of |ΔIab|≥Ki, |ΔIbc|≥Ki, and |ΔIca|≥Ki does not hold will be described. For example, when only |ΔIbc|≥Ki does not hold (i.e., |ΔIbc|<Ki) and |ΔIab|≥Ki and |ΔIca|≥Ki hold, the occurrence of a ground fault in phase A is assumed. Similarly, when only |ΔIab|≥Ki does not hold, the occurrence of a ground fault in phase C is assumed, and when only |ΔIca|≥Ki does not hold, the occurrence of a ground fault in phase B is assumed.

[0112] Here, assume that only |ΔIbc|≥Ki does not hold. In this case, since |ΔIbc|<Ki, the direction determination unit 109 (specifically, the BC-phase determination unit 202) does not perform the direction determination of the BC phase and thus does not output the forward determination signal Sbc. Specifically, the BC-phase determination unit 202 outputs a determination signal Sbc with a value of "0".

[0113] The direction determination of the AB phase will be described. When |ΔVab|≥Kv, the direction determination unit 109 (specifically, the AB-phase determination unit 201) outputs a forward determination signal Sab (i.e., a determination signal Sab with a value of "1") when the phase angle θab satisfies "φ3<θab<φ4". Next, when |ΔVab|<Kv, the AB-phase determination unit 201 outputs a forward determination signal Sab when the phase angle θabx of the inverse vector "-Va" with respect to the reference vector "ΔIab*ZS1" satisfies "φ3<θabx<φ4".

[0114] The direction determination of the CA phase will be described. When |ΔVca|≥Kv, the direction determination unit 109 (specifically, the CA-phase determination unit 203) outputs a forward determination signal Sca (i.e., a determination signal Sca with a value of "1") when the phase angle θca satisfies "φ3<θca<φ4". Next, when |ΔVca|<Kv, the CA-phase determination unit 203 outputs a forward determination signal Sca when the phase angle θcax of the A-phase voltage vector Va with respect to the reference vector "ΔIca*ZS1" satisfies "φ3<θcax<φ4".

[0115] Then, if the value of the determination signal Sab is "1", the value of the determination signal Sbc is "0", and the value of the determination signal Sca is "1", the direction determination unit 109 (specifically, the AND circuit 211) determines that the one-phase ground fault point of phase A is located in front of the protective relay device 100 (for example, it outputs a signal Sa with a value of "1").

[0116] Furthermore, if two or more of the following conditions are not met: |ΔIab|≧Ki, |ΔIbc|≧Ki, and |ΔIca|≧Ki, the direction determination unit 109 does not perform a direction determination of the fault point, as it is determined that no fault has occurred. In other words, the direction determination unit 109 does not output the forward determination signals Sab, Sbc, and Sca.

[0117] (flowchart) Figure 16 is a flowchart showing an example of a fault location direction determination method according to Embodiment 2. Each step shown in Figure 16 is typically performed by the CPU 32.

[0118] Referring to Figure 16, the protective relay 100 acquires electrical quantity data for each phase (step S10). The protective relay 100 determines whether each of the three conditions |ΔIab|≧Ki, |ΔIbc|≧Ki, and |ΔIca|≧Ki is met (step S12).

[0119] The protective relay device 100 executes the process from step S14 onward if it determines that all three conditions have been met. Here, we will describe the direction determination process for the AB phase executed by the direction determination unit 109 of the protective relay device 100. The direction determination processes for the BC phase and CA phase are the same as the processes from step S14 onward. For example, the direction determination process for the BC phase is equivalent to replacing "|ΔVab|", "θab", "θab1", and "Sabx" with "|ΔVbc|", "θbc", "θbc1", and "Sbcx", respectively, in steps S14, S16, S18, S20, and S22. The CA phase direction determination process corresponds to replacing “|ΔVab|”, “θab”, “θab1”, and “Sabx” with “|ΔVca|”, “θca”, “θca1”, and “Scax”, respectively, in steps S14, S16, S18, S20, and S22.

[0120] The direction determination unit 109 determines whether |ΔVab| is greater than or equal to the threshold Kv (step S14). If |ΔVab| is greater than or equal to the threshold Kv (YES in step S14), the direction determination unit 109 determines whether "φ3 < θab < φ4" holds true for the phase angle θab of the line voltage change vector ΔVab with respect to the reference vector "ΔIab*ZS1" (step S16). If "φ3 < θab < φ4" holds true (YES in step S16), the direction determination unit 109 outputs a forward determination signal (step S20). If step S14 has been passed, the forward determination signal Sabx is output in step S20. If "φ3 < θab < φ4" does not hold true (NO in step S16), the direction determination unit 109 does not output a forward determination signal (step S22). For example, if step S14 has been passed, the determination signal Sabx with a value of "0" is output.

[0121] Furthermore, if |ΔVab| is less than the threshold Kv (NO in step S14), the direction determination unit 109 determines whether "φ3 < θab1 < φ4" holds true for the phase angle θab1 of the inverse vector "-Vab" with respect to the reference vector "ΔIab*ZS1" (step S18). If "φ3 < θab1 < φ4" holds true (YES in step S18), the direction determination unit 109 outputs a forward determination signal (step S20). If "φ3 < θab1 < φ4" does not hold true (NO in step S20), the direction determination unit 109 does not output a forward determination signal (step S22).

[0122] The protective relay 100 executes the processing from step S24 onwards if it determines that only one condition is not met. Here, we will describe the direction determination processing for the AB phase, which is performed by the direction determination unit 109 when |ΔIab|≧Ki and |ΔIca|≧Ki are met, but |ΔIbc|≧Ki is not met. The direction determination processing for the CA phase is the same as the processing from step S24 onwards. The direction determination processing for the CA phase corresponds to replacing “|ΔVab|”, “θabx”, “θab”, “θab1”, and “Sab” with “|ΔVca|”, “θcax”, “θca”, “θca1”, and “Sca” respectively in steps S24, S26, S16, S20, and S22. Note that the direction determination processing for the BC phase is not performed, and the forward determination signal Sbc is not output.

[0123] The direction determination unit 109 determines whether |ΔVab| is greater than or equal to the threshold Kv (step S24). If |ΔVab| is greater than or equal to the threshold Kv (YES in step S24), the direction determination unit 109 executes the processing from step S16 onward. However, if step S24 is passed, a forward determination signal Sab is output in step S20, and a determination signal Sab with a value of "0" is output in step S22.

[0124] On the other hand, when |ΔVab| is less than the threshold value Kv (NO in step S24), the direction determination unit 109 determines whether "φ3 < θabx < φ4" holds for the phase angle θabx of the inverse vector "-Va" of the A-phase voltage vector with respect to the reference vector "ΔIab*ZS1" (step S26). When "φ3 < θabx < φ4" holds (YES in step S26), the direction determination unit 109 outputs a forward determination signal (step S20). When "φ3 < θabx < φ4" does not hold (NO in step S26), the direction determination unit 109 does not output a forward determination signal (step S22).

[0125] Here, the processing in the case where the occurrence of a single-phase-to-ground fault in phase A is assumed (that is, |ΔIab| ≧ Ki, |ΔIbc| < Ki, and |ΔIca| ≧ Ki hold) has been described. However, the same applies to the case where the occurrence of a single-phase-to-ground fault in phase B is assumed (that is, |ΔIab| ≧ Ki, |ΔIbc| ≧ Ki, and |ΔIca| < Ki hold) and the case where the occurrence of a single-phase-to-ground fault in phase C is assumed (that is, |ΔIab| < Ki, |ΔIbc| ≧ Ki, and |ΔIca| ≧ Ki hold).

[0126] When the occurrence of a single-phase-to-ground fault in phase B is assumed, the direction determination process for phases AB corresponds to the process after step S24. The direction determination process for phases BC corresponds to the process in steps S24, S26, S16, S20, and S22 where "|ΔVab|", "θabx", "θab", "θab1", and "Sab" are replaced with "|ΔVbc|", "θbcx", "θbc", "θbc1", and "Sbc", respectively. The direction determination process for phases CA is not executed, and the forward determination signal Sca is not output.

[0127] If a single-phase ground fault in phase C is anticipated, the direction determination process for phases BC corresponds to replacing "|ΔVab|", "θabx", "θab", "θab1", and "Sab" with "|ΔVbc|", "θbcx", "θbc", "θbc1", and "Sbc" respectively in steps S24, S26, S16, S20, and S22. The direction determination process for phases CA corresponds to replacing "|ΔVab|", "θabx", "θab", "θab1", and "Sab" with "|ΔVca|", "θcax", "θca", "θca1", and "Sca" respectively in steps S24, S26, S16, S20, and S22. The direction determination process for phases AB is not performed, and the forward determination signal Sab is not output.

[0128] Furthermore, the protective relay device 100 terminates processing if it determines that two or more conditions are not met. In other words, the direction determination unit 109 does not perform direction determination of the fault point and therefore does not output a forward determination signal.

[0129] <Functional Configuration> Referring to Figure 10, the functional configuration of the protective relay device 100 according to Embodiment 2 will be described. The functional configuration of the electricity quantity acquisition unit 101 is the same as the functional configuration described in Figure 10.

[0130] The current change vector calculation unit 103 calculates the line current change vector of the protected transmission line (for example, line current change vectors ΔIab, ΔIbc, ΔIca) as the current change vector. The voltage change vector calculation unit 105 calculates the line voltage change vector of the busbar 8 (for example, line voltage change vectors ΔVab, ΔVbc, ΔVca) as the voltage change vector.

[0131] The phase angle calculation unit 107 calculates the phase angle (e.g., phase angle θab) of the line voltage change vector (e.g., line voltage change vector ΔVab) with respect to a reference vector (e.g., reference vector "ΔIab*ZS1") obtained by multiplying the line current change vector by the positive-sequence impedance (e.g., positive-sequence back impedance ZS1) from the power supply point to the installation point of the protective relay device 100. The phase angle calculation unit 107 also calculates the phase angles θbc and θca as described above.

[0132] The direction determination unit 109 determines whether or not a fault point exists in front of the A phase and B phase (for example, whether or not a forward determination signal Sabx is output from the AB phase determination unit 201x) based on an angular range H2 that is greater than a first angle (for example, angle φ3) and smaller than a second angle (for example, angle φ4) and a reference phase angle (for example, phase angle θab).

[0133] In a given situation, the direction determination unit 109 determines that condition G1 is met, which is that the effective values ​​of the line current change vectors ΔIab and ΔIca (i.e., |ΔIab| and |ΔIca|) are greater than or equal to the threshold Ki, and the effective value of the line current change vector ΔIbc (i.e., |ΔIbc|) is less than the threshold Ki.

[0134] For example, if condition G1 is met and both |ΔVab| and |ΔVca| are greater than or equal to the threshold Kv, the direction determination unit 109 compares each of the phase angles θab and θca with the angular range H2. If both the phase angles θab and θca are within the angular range H2 (i.e., both “φ3 < θab < φ4” and “φ3 < θca < φ4” are met), the direction determination unit 109 determines that there is a one-phase ground fault point of phase A ahead.

[0135] For example, if condition G1 is met and both |ΔVab| and |ΔVca| are less than the threshold Kv, the direction determination unit 109 compares each of the phase angles θabx and θcax with the angular range H2. If both the phase angles θabx and θcax are within the angular range H2, the direction determination unit 109 determines that there is a one-phase ground fault point of phase A ahead. Alternatively, if condition G1 is met, |ΔVab| is greater than or equal to the threshold Kv, and |ΔVca| is less than the threshold Kv, the direction determination unit 109 compares each of the phase angles θab and θcax with the angular range H2. If both the phase angles θab and θcax are within the angular range H2, the direction determination unit 109 determines that there is a one-phase ground fault point of phase A ahead.

[0136] In other situations, the direction determination unit 109 determines that condition G2 is met, which is that all of |ΔIab|, |ΔIbc|, and |ΔIca| are greater than or equal to the threshold Ki. If condition G2 is met and all of |ΔVab|, |ΔVbc|, and |ΔVca| are greater than or equal to the threshold Kv, the direction determination unit 109 compares each of the phase angles θab, θbc, and θca with the angle range H2. If the phase angle θab is within the angle range H2, the direction determination unit 109 determines that there is a fault point ahead in phases A and B (for example, a short-circuit fault point in phases AB or a ground fault point in phases AB). If the phase angle θbc is within the angle range H2, the direction determination unit 109 determines that there is a fault point ahead in phases B and C. If the phase angle θca is within the angle range H2, the direction determination unit 109 determines that there is a fault point ahead in phases C and A.

[0137] Furthermore, if two or more of the effective values ​​of |ΔIab|, |ΔIbc|, and |ΔIca| are less than the threshold Ki, the direction determination unit 109 does not perform a direction determination of the fault point.

[0138] <Advantages> According to Embodiment 2, the direction determination of the fault point is performed using the line-to-line voltage change vector and the line-to-line current change vector for three phases. The protection control device according to Embodiment 2 can perform the direction determination of the fault point (for example, the ground fault point and the short-circuit fault point) by calculating for three phases between lines, so that the processing load in the direction determination can be reduced.

[0139] Other embodiments. (1) In Embodiment 1 described above, the protection relay device 100 determines that there is a fault point in the forward direction when the phase angle α1 is included in the angle range H1 (for example, satisfying φ1 < α1 < φ2) when "|ΔV1| < Kv" holds. However, when the threshold value Ki can be set as follows, based on the fact that "|ΔV1| < Kv" holds, the protection relay device 100 may immediately determine that there is a fault point in the forward direction.

[0140] Specifically, based on the equivalent circuit during a rearward fault as shown in Fig. 4(b), "ΔV1 = ΔI1 * (ZL1 + ZR1)" holds. From this, during a rearward fault, |ΔV1| becomes equal to or greater than the minimum value Vmin of |ΔI1 * (ZL1 + ZR1)| (that is, "|ΔV1| ≧ Vmin" holds). Here, when the threshold value Kv is set to be smaller than the minimum value Vmin, when "|ΔV1| < Kv" holds, "|ΔV1| < Vmin" also holds. This means that since "|ΔV1| ≧ Vmin" during a rearward fault is not satisfied, it can be determined that the fault point exists in the forward direction.

[0141] Therefore, when the effective value of the positive-phase voltage change vector ΔV1 is less than the threshold value Kv (where Kv < Vmin), the direction determination unit 109 determines that there is a fault point in the forward direction.

[0142] The above is the same in Embodiment 2. Specifically, when the effective value of the line-to-line voltage change vector (for example, |ΔVab|) is less than the threshold value Kv (where Kv < Vmin), the direction determination unit 109 may output a forward determination signal. For example, in the flowchart of FIG. 16, when |ΔVab| is less than the threshold value Kv (NO in step S14), the direction determination unit 109 outputs a forward determination signal (step S20). Also, when |ΔVab| is less than the threshold value Kv (NO in step S24), the direction determination unit 109 outputs a forward determination signal (step S20). For example, when the condition G2 that all of |ΔIab|, |ΔIbc|, and |ΔIca| are greater than or equal to the threshold value Ki holds and |ΔVab| is less than the threshold value Kv, the direction determination unit 109 determines that a fault point exists in front in phases A and B.

[0143] The above also applies to the effective values of other line-to-line voltage change vectors (for example, |ΔVbc|, |ΔVca|).

[0144] (2) In the above-described embodiment, the configuration in which the protection relay device 100 is a distance relay device has been described, but it is not limited to this configuration. For example, the protection relay device 100 may be another protection relay device (for example, a directional overcurrent relay device) that uses the above-described direction determination method (for example, has a direction determination unit 109).

[0145] (3) The configurations exemplified as the above-described embodiments are examples of the configuration of the present disclosure, and it is possible to combine them with other known technologies, and it is also possible to change the configuration by omitting a part or the like without departing from the gist of the present disclosure. Also, in the above-described embodiments, it may be a case where the processes and configurations described in other embodiments are appropriately adopted and implemented.

[0146] <Supplementary Note> Hereinafter, various aspects of the present disclosure will be summarized and described as supplementary notes.

[0147] (Supplementary Note 1) A protective relay device for protecting a power system, comprising: an electrical quantity acquisition unit that acquires instantaneous time-series values ​​of current detected in the power system and instantaneous time-series values ​​of voltage detected in the power system; a current change vector calculation unit that calculates a current change vector of a protected line included in the power system from the instantaneous time-series values ​​of current; a voltage change vector calculation unit that calculates a voltage change vector of a bus connected to the protected line from the instantaneous time-series values ​​of voltage; a phase angle calculation unit that calculates a reference phase angle based on the current change vector and the voltage change vector; and a direction determination unit that determines the direction of a fault point in the protected line based on the reference phase angle, a first angle, and a second angle that is larger than the first angle.

[0148] (Note 2) The protective relay device according to Appendix 1, wherein the direction determination unit determines that the fault point is located in front of the protective relay device if the reference phase angle is within an angular range greater than the first angle and smaller than the second angle.

[0149] (Note 3) The protective relay device according to Appendix 1 or Appendix 2, wherein the current change vector calculation unit calculates the positive-sequence current change vector of the protected line as the current change vector, the voltage change vector calculation unit calculates the positive-sequence voltage change vector of the bus as the voltage change vector, and the phase angle calculation unit calculates the first phase angle of the positive-sequence voltage change vector with respect to the positive-sequence current change vector as the reference phase angle.

[0150] (Note 4) The protective relay device as described in Appendix 3, wherein the phase angle calculation unit calculates the inverse vector of the positive-sequence voltage vector of the busbar, and if the effective value of the positive-sequence voltage change vector is less than a first threshold, the second phase angle of the inverse vector with respect to the positive-sequence voltage change vector is calculated as the reference phase angle instead of the first phase angle.

[0151] (Note 5) The protective relay device according to Appendix 3, wherein if the effective value of the positive-sequence voltage change vector is less than the first threshold, the direction determination unit determines that the fault point is located in front of the protective relay device.

[0152] (Note 6) The protective relay device as described in Appendix 1, wherein the current change vector calculation unit calculates the line-to-line current change vector of the protected line as the current change vector, the voltage change vector calculation unit calculates the line-to-line voltage change vector of the bus as the voltage change vector, and the phase angle calculation unit calculates the third phase angle of the line-to-line voltage change vector with respect to a reference vector obtained by multiplying the line-to-line current change vector by the positive-sequence impedance from the power source point to the installation point of the protective relay device as the reference phase angle.

[0153] (Note 7) The protective relay device according to Appendix 6, wherein the line-to-line current change vector includes a first current change vector of the first line-to-line current of the first and second phases of the power system, the line-to-line voltage change vector includes a first voltage change vector of the first line-to-line voltage of the first and second phases, the reference vector includes a first vector obtained by multiplying the positive-sequence impedance by the first current change vector, the third phase angle includes a fourth phase angle indicating the phase angle of the first voltage change vector with respect to the first vector, and the direction determination unit determines that the fault point is located in front of the protective relay device in the first and second phases based on an angular range greater than the first angle and less than the second angle, and the fourth phase angle.

[0154] (Note 8) The protective relay device according to Appendix 7, wherein the line-to-line current change vector further includes a second current change vector of the second line-to-line current of the second and third phases and a third current change vector of the third line-to-line current of the third and first phases; the line-to-line voltage change vector further includes a second voltage change vector of the second line-to-line voltage of the second and third phases and a third voltage change vector of the third line-to-line voltage of the third and first phases; the reference vector further includes a second vector obtained by multiplying the positive-sequence impedance by the second current change vector and a third vector obtained by multiplying the positive-sequence impedance by the third current change vector; and the third phase angle further includes a fifth phase angle indicating the phase angle of the second voltage change vector with respect to the second vector and a sixth phase angle indicating the phase angle of the third voltage change vector with respect to the third vector.

[0155] (Note 9) The direction determination unit compares the fourth phase angle and the sixth phase angle with the angle range if the effective values ​​of the first current change vector and the third current change vector are greater than or equal to the second threshold, and the effective value of the second current change vector is less than the second threshold, and if both the fourth phase angle and the sixth phase angle are within the angle range, it determines that the ground fault point of the first phase is located in front of the protective relay device, as described in Appendix 8.

[0156] (Note 10) The direction determination unit compares the fourth phase angle with the angular range if the effective values ​​of all the first current change vector, the second current change vector, and the third current change vector are greater than or equal to the second threshold, and determines that the fault point is located in front of the protective relay device in the first and second phases if the fourth phase angle is within the angular range, as described in Appendix 8 or Appendix 9.

[0157] (Note 11) A protective relay device according to any one of Appendix 8 to Appendix 10, wherein if the effective values ​​of two or more current change vectors among the first current change vector, the second current change vector, and the third current change vector are less than the second threshold, the direction determination unit does not perform direction determination of the fault point.

[0158] (Note 12) A protective relay device according to any one of the appendices 6 to 11, wherein if the effective value of the line voltage change vector is less than a first threshold, the direction determination unit determines that the fault point is located ahead.

[0159] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended. [Explanation of Symbols]

[0160] 7 Transmission line, 8 Busbar, 10 Auxiliary transformer, 20 Signal conversion unit, 21,23 Filter, 24,25 Sample-and-hold circuit, 26 Multiplexer, 27 A / D converter, 30 Arithmetic processing unit, 31 Bus, 33 ROM, 34 RAM, 36 DO circuit, 37 DI circuit, 38 Display, 39 Input interface, 50 Circuit breaker, 100 Protective relay, 101 Electric quantity acquisition unit, 103 Current change vector calculation unit, 105 Voltage change vector calculation unit, 107 Phase angle calculation unit, 109 Direction determination unit, 111 Distance determination unit, 113 Output control unit, 201,201x AB phase determination unit, 202,202x BC phase determination unit, 203,203x CA phase determination unit, 211,212,213 AND circuit.

Claims

1. A protective relay device for protecting a power system, An electrical quantity acquisition unit that acquires the instantaneous time-series value of current detected in the power system and the instantaneous time-series value of voltage detected in the power system, A current change vector calculation unit calculates the current change vector of the protected line included in the power system from the current time series instantaneous values, A voltage change vector calculation unit calculates a voltage change vector of a bus connected to the protected line from the aforementioned voltage time-series instantaneous values, A phase angle calculation unit that calculates a reference phase angle based on the current change vector and the voltage change vector, A protective relay device comprising a direction determination unit that determines the direction of a fault point in the protected line based on the aforementioned reference phase angle, a first angle, and a second angle that is larger than the first angle.

2. The protective relay device according to claim 1, wherein the direction determination unit determines that the fault point is located in front of the protective relay device if the reference phase angle is within an angular range greater than the first angle and smaller than the second angle.

3. The current change vector calculation unit calculates the positive-sequence current change vector of the protected transmission line as the current change vector, The voltage change vector calculation unit calculates the positive-sequence voltage change vector of the bus as the voltage change vector, The protective relay device according to claim 1 or claim 2, wherein the phase angle calculation unit calculates a first phase angle of the positive-sequence voltage change vector with respect to the positive-sequence current change vector as the reference phase angle.

4. The phase angle calculation unit, The inverse vector of the positive-sequence voltage vector of the busbar is calculated, The protective relay device according to claim 3, wherein, if the effective value of the positive-sequence voltage change vector is less than a first threshold, the second phase angle of the inverse vector with respect to the positive-sequence voltage change vector is calculated as the reference phase angle instead of the first phase angle.

5. The protective relay device according to claim 3, wherein if the effective value of the positive-sequence voltage change vector is less than a first threshold, the direction determination unit determines that the fault point is located in front of the protective relay device.

6. The current change vector calculation unit calculates the inter-line current change vector of the protected transmission line as the current change vector, The voltage change vector calculation unit calculates the line-to-line voltage change vector of the bus as the voltage change vector, The protective relay device according to claim 1, wherein the phase angle calculation unit calculates a third phase angle of the line voltage change vector with respect to a reference vector obtained by multiplying the line current change vector by the positive-sequence impedance from the power source point to the installation point of the protective relay device, as the reference phase angle.

7. The line-to-line current change vector includes the first current change vector of the first line-to-line current of the first phase and second phase of the power system. The line-to-line voltage change vector includes the first voltage change vector of the first line-to-line voltage of the first phase and the second phase, The reference vector includes a first vector obtained by multiplying the positive-sequence impedance by the first current change vector. The third phase angle includes a fourth phase angle that indicates the phase angle of the first voltage change vector with respect to the first vector, The protective relay device according to claim 6, wherein the direction determination unit determines whether the fault point exists in front of the protective relay device in the first phase and the second phase based on an angular range greater than the first angle and less than the second angle and the fourth phase angle.

8. The line current change vector further includes a second current change vector of the second line current of the second phase and the third phase, and a third current change vector of the third line current of the third phase and the first phase. The line voltage change vector further includes a second voltage change vector of the second line voltage of the second phase and the third phase, and a third voltage change vector of the third line voltage of the third phase and the first phase. The reference vector further includes a second vector obtained by multiplying the positive-sequence impedance by the second current change vector, and a third vector obtained by multiplying the positive-sequence impedance by the third current change vector. The protective relay device according to claim 7, wherein the third phase angle further includes a fifth phase angle indicating the phase angle of the second voltage change vector with respect to the second vector, and a sixth phase angle indicating the phase angle of the third voltage change vector with respect to the third vector.

9. The direction determination unit, If the effective values ​​of the first current change vector and the third current change vector are greater than or equal to the second threshold, and the effective value of the second current change vector is less than the second threshold, then the fourth phase angle and the sixth phase angle are compared with the angle range. The protective relay device according to claim 8, wherein if both the fourth phase angle and the sixth phase angle are within the angular range, it is determined that the ground fault point of the first phase is located in front of the protective relay device.

10. The direction determination unit, If the effective values ​​of the first current change vector, the second current change vector, and the third current change vector are all greater than or equal to the second threshold, the fourth phase angle is compared with the angle range. The protective relay device according to claim 8, wherein if the fourth phase angle is within the angular range, it is determined that the fault point is located in front of the protective relay device in the first phase and the second phase.

11. The protective relay device according to claim 9 or 10, wherein if the effective values ​​of two or more current change vectors among the first current change vector, the second current change vector, and the third current change vector are less than the second threshold, the direction determination unit does not perform a direction determination of the fault point.

12. The protective relay device according to any one of claims 6 to 10, wherein if the effective value of the line voltage change vector is less than a first threshold, the direction determination unit determines that the fault point is located in front of the protective relay device.

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