JP2012130107A - Ground fault protection relay system and ground fault protection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability of ground fault protection for a parallel two-circuit power-transmission line of a high-resistance grounding system.SOLUTION: In a ground fault protection relay system that protects a parallel two-circuit power-transmission line made up of first and second power-transmission lines, which are connected between a power transmission terminal bus line of a high-resistance grounding system and a power receiving terminal bus line grounded via a compensation reactor, from ground fault accident, the system includes: a main protection relay system that is used as main protection for protecting the parallel two-circuit power-transmission line from ground fault accident; first and second ground fault direction relay systems which are respectively installed to the first and second power-transmission lines and used as back-up protection of the main protection relay system; and first and second zero-phase current transformers which respectively detect first zero-phase current flowing through the first power-transmission line and second zero-phase current flowing through the second power-transmission line. The main protection relay system outputs a lock signal for stopping the operation of the first and second ground fault direction relay systems when the first zero-phase current and the second zero-phase current are approximately equal.

Description

  The present invention relates to a ground fault protection relay system and a ground fault protection method.

  Many extra high voltage power transmission systems of several tens to hundreds of tens of kV employ a high resistance grounding system in which a neutral point is grounded via a high resistance neutral point grounding resistor. In the high-resistance grounding system, a ground fault protection system for a parallel (balanced) two-line power transmission line between a power transmission end bus and a power reception end bus is, for example, a ground fault protection relay shown in FIG. As in the system, a ground fault direction relay device is used as a back-up protection.

  Moreover, in patent document 1, when both a ground fault overcurrent relay apparatus and a ground fault direction relay apparatus detect a ground fault, the trip signal for interrupting the circuit breaker installed in the power transmission line is output. A ground fault protection relay system is disclosed. In this way, by using the ground fault overcurrent relay device and the ground fault direction relay device in combination, the parallel two-line power transmission line can be protected from a ground fault accident without causing a decrease in supply reliability. .

JP 2009-254036 A

  By the way, in recent years, in the urban areas, the underground electric lines have been undergrounded in consideration of the improvement of the scenery and the safety aspect at the time of disaster. In addition, the underground cable has a larger ground charging capacity than the overhead cable, so the compensation reactor for offsetting the ground charging current is distributed at the power station at the power receiving end around the power station at the transmitting end. May be installed.

  However, in a high-resistance grounding system in which compensation reactors are dispersedly installed, zero-phase current is supplied via the compensation reactor and a resistor connected in series to the compensation reactor. Therefore, the ground fault direction relay device may malfunction.

  The main present invention that solves the above-described problem is a parallel two-circuit composed of first and second power transmission lines connected between a power transmission end bus of a high-resistance grounding system and a power reception end bus grounded through a compensation reactor. A ground fault protection relay system for protecting a line transmission line from a ground fault, and a main protection relay device used as a main protection for protecting the parallel two-line transmission line from a ground fault; First and second ground fault direction relay devices installed on the first and second transmission lines, respectively, and used as supplementary protection for the main protection relay device, and a first flowing through the first transmission line 1 and a second zero-phase current transformer for detecting a first zero-phase current and a second zero-phase current flowing through the second transmission line, respectively. When the zero-phase current of 1 and the second zero-phase current are substantially equal, A ground fault protective relay system and outputs a lock signal for stopping the operation of the first and second earth fault direction relay device.

  Other features of the present invention will become apparent from the accompanying drawings and the description of this specification.

  ADVANTAGE OF THE INVENTION According to this invention, the reliability of the ground fault protection with respect to the parallel 2 line power transmission line of a high resistance grounding system can be improved.

It is a block diagram which shows the structure of the ground fault protection relay system in one Embodiment of this invention. It is a figure which shows the relationship between the zero phase current of each power transmission line, and the logic level of the lock signal LKa. It is a figure which shows the relationship between the zero phase current of each power transmission line, and the logic level of the lock signal LKb. It is a figure which shows the relationship between the zero phase current of each power transmission line, and the logic level of the lock signal LKc. It is a figure which shows the relationship between the zero phase current of each power transmission line, and the logic level of the lock signal LKd. In one Embodiment of this invention, it is a figure explaining operation | movement of a ground fault protection relay system when a ground fault accident generate | occur | produces in the power transmission line L3. In one Embodiment of this invention, it is a figure explaining the operation | movement of a ground fault protection relay system when a ground fault accident generate | occur | produces in the power transmission line L1. In one Embodiment of this invention, it is a figure explaining operation | movement of a ground fault protection relay system when a ground fault accident has occurred near the power transmission end of the transmission line L1.

  At least the following matters will become apparent from the description of this specification and the accompanying drawings.

=== Configuration of ground fault protection relay system ===
Hereinafter, with reference to FIG. 1, the structure of the ground fault protection relay system in one Embodiment of this invention is demonstrated.

  The ground fault protection relay system shown in FIG. 1 is a system for protecting a parallel two-line transmission line between substations A and B from a ground fault, and is used together with circuit breakers 14a to 14d. The ground fault protection relay system includes zero-phase current transformers 11a to 11d, current differential relay devices 12a to 12d, and ground fault direction relay devices 13a to 13d.

  The parallel two-line transmission line is composed of a (first) transmission line L1 and a (second) transmission line L2 connected between the transmission end bus 20a of the substation A and the receiving end bus 20b of the substation B. . The neutral point of the power transmission end bus 20a is grounded via a neutral point grounding resistor 22a, and the neutral point of the power receiving end bus 20b is composed of a compensation reactor 23 and a neutral point grounding resistor connected in series. It is grounded through 22b. Furthermore, grounded-type instrument transformers 21a and 21b are connected to the power transmission end bus 20a and the power reception end bus 20b, respectively. In FIG. 1, a power transmission line L3 connected between the bus 20a of the substation A and the bus 20c of the substation C is shown as a power transmission line that is not protected by the ground fault protection relay system. Yes.

  Zero-phase current transformers 11a and 11b are installed on the power transmission end side and the power receiving end side of the transmission line L1, respectively, and zero phase current transformers 11c and 11d are installed on the power transmission end side and the power reception end side of the transmission line L2, respectively. Has been. Zero-phase currents I0a to I0d are output from the zero-phase current transformers 11a to 11d, respectively. In the present embodiment, the zero-phase current transformers 11a and 11b correspond to the first zero-phase current transformer, and the zero-phase currents I0a and I0b correspond to the first zero-phase current. On the other hand, the zero-phase current transformers 11c and 11d correspond to the second zero-phase current transformer, and the zero-phase currents I0c and I0d correspond to the second zero-phase current.

  Zero-phase currents I0a to I0d are input to the current differential relay devices 12a to 12d, respectively. The current differential relay devices 12a to 12d output trip signals T1a to T1d and lock signals LKa to LKd, respectively. Furthermore, the current differential relay devices 12a to 12d have a function of mutually transmitting and receiving information on the zero-phase currents I0a to I0d via a PCM (Pulse Code Modulation) transmission line. In the present embodiment, the current differential relay devices 12a and 12b correspond to the first current differential relay device, and the current differential relay devices 12c and 12d serve as the second current differential relay device. Equivalent to.

  Zero-phase currents I0a to I0d and lock signals LKa to LKd are input to the ground fault direction relay devices 13a to 13d, respectively. The ground fault direction relay devices 13a and 13b receive the zero-phase voltage V0a from the grounded-type instrument transformer 21a, and the ground fault direction relay devices 13c and 13d receive the ground-type instrument transformer 21b. Zero phase voltage V0b is input. Trip signals T2a to T2d are output from the ground fault direction relay devices 13a to 13d, respectively. In the present embodiment, the ground fault direction relay devices 13a and 13b correspond to the first ground fault direction relay device, and the ground fault direction relay devices 13c and 13d serve as the second ground fault direction relay device. Equivalent to.

  The circuit breakers 14a and 14b are respectively installed on the power transmission end side and the power receiving end side of the power transmission line L1, and the circuit breakers 14c and 14d are respectively installed on the power transmission end side and the power receiving end side of the power transmission line L2. Trip signals T1a to T1d and trip signals T2a to T2d are input to the circuit breakers 14a to 14d, respectively.

=== Operation of ground fault protection relay system ===
Next, the operation of the ground fault protection relay system according to the present embodiment will be described with reference to FIGS. 2 to 5 as appropriate. In the ground fault protection relay system of this embodiment, the current differential relay devices 12a to 12d are used as main protection, and the ground fault direction relay devices 13a to 13d are used as back-up protection.

  Zero-phase current transformers 11a and 11b detect a zero-phase current I0a flowing through the power transmission end of power transmission line L1 and a zero-phase current I0b flowing through the power receiving end, respectively. On the other hand, the zero-phase current transformers 11c and 11d detect the zero-phase current I0c flowing through the power transmission end of the transmission line L2 and the zero-phase current I0d flowing through the power receiving end, respectively. The direction in which each zero-phase current flows is the direction from the power transmission end or power reception end side where the zero-phase current transformer is installed toward the opposite end (power reception end or power transmission end) (the direction of each arrow in FIG. 1). Is positive.

  The current differential relay device 12a includes the zero-phase current I0a information input from the zero-phase current transformer 11a and the zero-phase current I0b and I0c information received from the current differential relay devices 12b and 12c, respectively. Based on this, the trip signal T1a and the lock signal LKa are output.

  Specifically, the current differential relay device 12a is configured to transmit the transmission line when the zero-phase current at the power transmission end flowing into the power transmission line L1 and the zero-phase current at the power receiving end flowing out from the power transmission line L1 are not equal. It is detected that a ground fault has occurred at L1, and the trip signal T1a is set to high level. That is, when I0a − (− I0b) ≠ 0, the trip signal T1a is at the high level. On the other hand, the current differential relay device 12a does not detect the occurrence of a ground fault in the power transmission line L1, and transmits the zero-phase current on the power transmission end side flowing into the power transmission line L1 and the power transmission flowing into the power transmission line L2. When the zero-phase current on the end side is (substantially) equal, the lock signal LKa is set to high level. That is, as shown in FIG. 2, when I0a + I0b = 0 and I0a = I0c, the lock signal LKa is at a high level.

  Similarly, when I0a + I0b ≠ 0, the trip signal T1b is at a high level, and as shown in FIG. 3, when I0a + I0b = 0 and I0b = I0d, the lock signal LKb is at a high level. Similarly, when I0c + I0d ≠ 0, the trip signal T1c becomes high level, and as shown in FIG. 4, when I0c + I0d = 0 and I0a = I0c, the lock signal LKc becomes high level. Similarly, when I0c + I0d ≠ 0, the trip signal T1d is at a high level. As shown in FIG. 5, when I0c + I0d = 0 and I0b = I0d, the lock signal LKd is at a high level.

  When the lock signal LKa is at a low level, the ground fault direction relay device 13a is connected to the zero phase voltage V0a, the zero phase current I0a, and the ground fault overvoltage relay in the same manner as a general ground fault direction relay device. A trip signal T2a is output based on an output signal of a device (not shown). On the other hand, when the lock signal LKa is at a high level, the ground fault direction relay device 13a is locked (stops operation), and the trip signal T2a is held at a low level.

  Similarly, when the lock signal LKb is low level, the trip signal T2b is output based on the zero-phase voltage V0b and the zero-phase current I0b and the output signal of the ground fault overvoltage relay device, and the lock signal LKb When is high, it is held low. Similarly, when the lock signal LKc is at a low level, the trip signal T2c is output based on the zero-phase voltage V0a and the zero-phase current I0c and the output signal of the ground fault overvoltage relay device. When the signal LKc is at a high level, it is held at a low level. Further, similarly, when the lock signal LKd is at a low level, the trip signal T2d is output based on the zero-phase voltage V0b and the zero-phase current I0d and the output signal of the ground fault overvoltage relay device. When the signal LKd is at a high level, it is held at a low level.

  The circuit breaker 14a is cut off when the trip signal T1a is at a high level or when the trip signal T2a is at a high level. Similarly, the circuit breaker 14b is cut off when the trip signal T1b is at a high level or when the trip signal T2b is at a high level. Similarly, the circuit breaker 14c is cut off when the trip signal T1c is at a high level or when the trip signal T2c is at a high level. Further, similarly, the circuit breaker 14d is cut off when the trip signal T1d is at a high level or when the trip signal T2d is at a high level.

  In this way, in the ground fault protection relay system of the present embodiment, the current differential relay device (main protection) does not detect that a ground fault has occurred in the power transmission line to be protected, and the power transmission line When the zero-phase currents flowing through L1 and L2 are (substantially) equal, the ground fault relay device (rear protection) is locked.

=== Specific example of operation of ground fault protection relay system ===
Here, a specific example of the operation of the ground fault protection relay system will be described with reference to FIGS. 6 to 8 as appropriate. In the following description, the ground charging current is completely canceled by the compensation reactor 23, and the current flowing into the ground capacitance of each transmission line is omitted from the ground fault current.

  First, with reference to FIG. 6, the operation when a ground fault occurs in the transmission line L3 that is not protected by the ground fault protection relay system will be described.

  When a ground fault occurs on the transmission line L3, a ground fault current Ig (= Iga + Igc) flows from the ground fault point to the ground. Further, the ground fault current Ig flows into the neutral point grounding resistors 22a and 22b through the ground.

  Of the ground fault current Ig, the current IRa flowing into the neutral grounding resistor 22a flows toward the ground fault point of the power transmission line L3 via the power transmission end bus 20a. Therefore, current IRa does not affect zero phase currents I0a to I0d.

  Of the ground fault current Ig, the current IRb flowing into the neutral point grounding resistor 22b is directed to the ground fault point of the transmission line L3 via the power receiving end bus 20b, the power transmission lines L1 and L2, and the power transmission end bus 20a. Flowing. Since the power transmission lines L1 and L2 are parallel two-line power transmission lines, the current IRb is distributed substantially evenly to the power transmission lines L1 and L2.

  Therefore, the relationship of I0a + I0b = 0 and I0c + I0d = 0 is maintained, and the trip signals T1a to T1d are all held at the low level. Further, the relationship of I0a = I0c and I0b = I0d is also maintained, the lock signals LKa to LKd are all at the high level, and the ground fault direction relay devices 13a to 13d are all locked. Therefore, malfunction of the ground fault direction relay devices 13a to 13d is prevented, and the circuit breakers 14a to 14d are not blocked.

  In the ground fault protection relay system of the present embodiment, the power transmission end bus 20a and the power receiving end bus 20b are also not protected, and even when a ground fault occurs in the power transmission end bus 20a or the power receiving end bus 20b, The entanglement relay devices 13a to 13d are all locked.

  Next, with reference to FIG. 7, an operation when a ground fault occurs in the power transmission line L1 that is a protection target of the ground fault protection relay system will be described.

  When a ground fault occurs in the transmission line L1, a ground fault current Ig (= Iga + Igb) flows from the ground fault point to the ground. In addition, the current IRa out of the ground fault current Ig flows toward the ground fault point of the power transmission line L1 via the power transmission end bus 20a. On the other hand, the current IRb flows toward the ground fault point of the power transmission line L1 via the power receiving end bus 20b.

  Therefore, I0a + I0b ≠ 0, trip signals T1a and T1b are at a high level, and breakers 14a and 14b are cut off. Further, the relationship of I0c + I0d = 0 is maintained, and the trip signals T1c and T1d are held at the low level. Further, I0a ≠ I0c and I0b ≠ I0d, and the lock signals LKa to LKd are all low level, and the ground fault relay devices 13a to 13d are not locked. Therefore, despite the occurrence of a ground fault in the transmission line L1, the ground fault direction relay devices 13a and 13b are not locked, and a malfunction that does not operate when it should operate is prevented. .

  As shown in FIG. 7, when a ground fault near the midpoint of the transmission line L1 occurs, the lock signals LKa to LKd are set to the low level only by the relationship of I0a ≠ I0c and I0b ≠ I0d. You can also However, in this case, as shown in FIG. 8, when a ground fault occurs near the power transmission end of the transmission line L1, there is a possibility of malfunction.

  In FIG. 8, the current IRa out of the ground fault current Ig flows toward the ground fault point of the power transmission line L1 via the power transmission end bus 20a. On the other hand, since the ground fault near the power transmission end is substantially equal to the ground fault in the power transmission end bus 20a for the current IRb on the power receiving end side, the current IRb is distributed substantially evenly to the power transmission lines L1 and L2. .

  Accordingly, as in the case of FIG. 7, the trip signals T1a and T1b are at a high level, and the trip signals T1c and T1d are held at a low level. Further, I0a ≠ I0c, the lock signals LKa and LKc become low level, and the ground fault relay devices 13a and 13c are not locked. On the other hand, the relationship of I0b = I0d is maintained, the lock signal LKd becomes high level, and although the ground fault relay device 13d is locked, since I0a + I0b ≠ 0, the lock signal LKb becomes low level. The ground fault direction relay device 13b is not locked. Therefore, also in FIG. 8, the ground fault direction relay devices 13a and 13b are not locked, and malfunction is prevented.

  When a ground fault occurs near the power receiving end of the transmission line L1, the ground fault direction relay device 13c is locked, but the ground fault direction relay devices 13a and 13b are not locked. Operation is prevented. Furthermore, when a ground fault occurs near the power transmission end or power receiving end of the transmission line L2, the ground fault direction relay devices 13a or 13b are locked, but the ground fault direction relay devices 13c and 13d are locked. There is no false malfunction.

  As described above, in the ground fault protection relay system shown in FIG. 1, when the zero-phase currents flowing through the transmission lines L1 and L2 are (substantially) equal, a high level lock signal is output, By locking the earth fault direction relay device used, it is possible to prevent malfunction of the earth fault direction relay device against ground fault accidents that are not protected, and to prevent ground fault protection for parallel two-line transmission lines of the high resistance grounding system. Reliability can be improved.

  Also, by using the current differential relay device as the main protection, the zero-phase current information is mutually transmitted and received, and the ground fault occurs based on the zero-phase current on the power transmission end side and the zero-phase current on the power receiving end side , And the ground fault direction relay device can be locked based on the zero-phase current flowing through the transmission lines L1 and L2.

  In addition, the malfunction of the ground fault direction relay device is prevented by locking the ground fault direction relay device only when the current differential relay device does not detect that a ground fault has occurred on the transmission line to be protected. Can be prevented.

  Also, when the zero-phase currents flowing through the transmission lines L1 and L2 are (substantially) equal, the ground fault direction relay device is locked to prevent malfunction of the ground fault direction relay device against a ground fault accident that is not protected. In addition, it is possible to improve the reliability of ground fault protection for the parallel two-line transmission line of the high resistance grounding system.

  In addition, the said embodiment is for making an understanding of this invention easy, and is not for limiting and interpreting this invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes equivalents thereof.

11a to 11d Zero-phase current transformer 12a to 12d Current differential relay device 13a to 13d Ground fault direction relay device 14a to 14d Breaker 20a to 20c Busbar 21a, 21b Grounding type instrument transformer 22a, 22b Neutral point Grounding resistor 23 Compensating reactor L1-L3 Transmission line

Claims (4)

In order to protect a parallel two-line power transmission line composed of first and second power transmission lines connected between a power transmission end bus of a high resistance grounding system and a power receiving end bus grounded via a compensating reactor from a ground fault. The ground fault protection relay system of
A main protection relay device used as a main protection for protecting the parallel two-line transmission line from a ground fault;
First and second ground fault direction relay devices installed on the first and second transmission lines, respectively, and used as backup protection of the main protection relay device;
First and second zero-phase current transformers that respectively detect a first zero-phase current flowing through the first transmission line and a second zero-phase current flowing through the second transmission line;
With
The main protection relay device is configured to stop the operation of the first and second ground fault direction relay devices when the first zero-phase current and the second zero-phase current are substantially equal. A ground fault protection relay system that outputs a lock signal.   The main protective relay device is installed in each of the first and second power transmission lines, and detects a ground fault based on the amount of electricity between the power transmission end side and the power reception end side. The ground fault protection relay system according to claim 1, wherein the ground fault protection relay system is a dynamic relay device. The main protective relay device is
When detecting a ground fault occurring in the first power transmission line, do not output the lock signal to the first ground fault direction relay device,
The said lock signal is not output with respect to a said 2nd ground fault direction relay apparatus, when the ground fault accident which generate | occur | produced in the said 2nd power transmission line is detected, The lock signal is not output. The ground fault protection relay system described in 1. A ground that protects a parallel two-line power transmission line composed of first and second power transmission lines connected between a power transmission end bus of a high resistance grounding system and a power receiving end bus grounded via a compensation reactor from a ground fault. A protection method,
When the first zero-phase current flowing through the first transmission line and the second zero-phase current flowing through the second transmission line are substantially equal, the first and second transmission lines are installed respectively. A ground fault protection method comprising: stopping operations of the first and second ground fault direction relay devices.

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