JPH0155487B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to reactive power compensation equipment for power systems, and in particular, when a grounding fault occurs on a power transmission line, the grounding fault is detected and a reactor is controlled so that the secondary arc current is minimized. The present invention relates to a reactive power compensator configured to do so.

In ultra-high-voltage or ultra-super-high-voltage transmission lines, reactive power compensation equipment is installed to suppress the value of phase-advanced reactive power based on the distributed capacitance that exists between each phase line of the transmission line and the ground, and between each phase line. Installed on electric wires. In such a system, in order to reclose the circuit in the event of a fault, etc., the fault current must be cut off by a circuit breaker, and then the fault current should be cut off by an electrostatic coupling between the fault phase and the healthy phase. It is necessary to reduce the flowing secondary arc current.

FIG. 1 shows an example of a configuration in which a power transmission line is equipped with a reactive power compensator.

In Figure 1, 1 is a power transmission line connected to a three-phase AC power supply AC via a sheath disconnector 2 and corresponds to each of the three phases, and 3 is a distributed static electricity that exists between each phase line of the power transmission line 1 and the ground. The capacitance 4 is the distributed capacitance existing between each phase line of the power transmission line 1. In addition, 5 has a star connection (Y connection) on the primary side and a delta connection (Δ connection) on the secondary side.
The primary side of the transformer 5 is connected to each phase line of the power transmission line 1, and a control reactor 6 is connected between the neutral point and the ground. Further, a control reactor 7 connected in a delta connection (Δ connection) is connected to the secondary side of the transformer 5.
Each of these control reactors 6 and 7 is constructed by connecting a reactor in series to a thyristor connected in antiparallel. In the figure, reference numeral 8 denotes a ground fault breakout switch installed between one phase of the power transmission line 1 and the ground.

In a system with such a configuration, the magnitude of the secondary arc current flowing due to the electrostatic coupling between the faulty phase and the healthy phase is considered as follows.

A power transmission line 1 in which distributed capacitances 3 and 4 exist between each phase line of the power transmission line 1 and the ground and between each phase line
The admittance matrix determines the voltage on each phase line.
Let Va, Vb, Vc, and each phase current injected into the distributed capacitance be _ia , _ib , and _ic , as expressed by equation (1).

i _a i _b i _c = Yaa −Yab −Yac −Yab Ybb −Ybc −Yac Ybc YccVa Vb Vc …(1) On the other hand, between the neutral point on the primary side of Y-Δ connection transformer 5 and the earth Control reactor 6 installed in
The admittance matrix of the reactive power compensation equipment consists of the control reactor 7 connected to each phase on the secondary side in a delta connection, and the current injected into the reactive power compensation equipment is i _a ′, i _b ′, i Let _c ′ be given by equation (2).

i _a ′ i _b ′ i _c ′＝ Yaa′ −Yab′ −Yac′ −Yab′ Ybb′ −Ybc′ −Yac′ −Ybc′ Ycc′Va Vb Vc …(2) In equations (1) and (2) Based on the conditions, one phase of the transmission line 1 is caused to fail by turning on the shield breaker 8, and the failed phase is opened by the shield breaker 2 to separate the failed phase from the grid, thereby creating a secondary arc. The current I is determined by the following equation.

I=i _a ′+i _a =−(Yab+Yab′)Vb −(Yac+Yac′)Ve…(3) In the formula (3), the values of admittance Yab and Yac have the opposite sign with respect to the admittance Yab′ and Yac′. Therefore,
If the admittances Yab and Yac determined by the control reactors 6 and 7 are selected to satisfy equation (3) for the admittances Yab and Yac determined by the distributed capacitances 3 and 4 of the transmission line 1, the secondary arc current can be It can be set to zero.

However, since the distribution capacitances 3 and 4 of the power transmission line 1 are not symmetrical, the values of the secondary arc current determined by equation (3) and this secondary arc current depend on which phase fails. Normally, the value of the control reactor is different in order to minimize the

The present invention has been made in view of the above circumstances, and it calculates the conditions for minimizing the secondary arc current based on the signal of the detection circuit that detects the faulty phase, and uses the calculated conditions to control the control reactor. It is an object of the present invention to provide a reactive power compensator that can easily minimize secondary arc current in any ground fault by controlling the value.

The present invention will be described below based on an embodiment shown in the drawings. FIG. 2 shows one configuration example of the present invention, and the same parts as in FIG. 1 are given the same symbols. That is, in FIG. 2, 5 is a Y-Δ connection transformer, the primary side of which is connected to each phase line of the power transmission line 1, and its neutral point is grounded to the earth through a control reactor 6. A Δ-connected control reactor 7 is connected to each phase on the secondary side of the transformer 5. In such reactive power compensation equipment, a detection device 8 for detecting a ground fault phase is connected to each phase line of the power transmission line 1, and a control reactor 7 is connected to each phase on the secondary side of the Y-Δ connection transformer 5. A voltage detection device 9 for detecting voltage is connected. The outputs of both of these detection devices 8 and 9 are given to a current calculation device 10. On the other hand, 11 is Δ
A current measuring device is used to add each phase current of the connected control reactor, and the output of this current measuring device 11 is compared with the output of the current calculating device 10. The differential voltage between the matched output of the current calculation device 10 and the output of the current measurement device 10 is converted into an amplifier 1.
2 to the pulse generating circuit 13, and the pulse is applied to the gate circuit of the thyristor of the control reactor 7. Note that although the circuit from the ground failure phase detection device 8 of the power transmission line 1 to the pulse generation circuit 13 is represented by one line, it is configured for each phase.

Next, the operation of the apparatus of this embodiment configured as described above will be explained.

When a grounding fault occurs in the power transmission line 1, a grounding fault phase detection device 8 detects which phase has caused the grounding fault. When the ground phase is detected by this detection device 8, the ground phase is determined from the distributed capacitance of the power transmission line 1.
In the current calculation device 10 in which the admittance matrix of equation (1) is stored, the value of the control reactor that minimizes the secondary arc current based on the ground phase is calculated from the condition of equation (3). Next, in the current calculation device 10, a current flows when the value of the control reactor reaches the calculated value based on the calculated value of the control reactor and the voltage value of the control reactor detected by the voltage detection device 9. Calculate the current. The difference between the voltage proportional to the current calculated by the current calculation device 10 and the voltage proportional to the actually flowing current output from the current measurement device 11 is determined by the amplifier 12.
The output is amplified by the pulse generating circuit 13. In the pulse generation circuit 13, the amplifier 12
Since the pulse is generated in the direction in which the output of is possible.

In FIG. 2, the description has been made for a single-circuit power transmission line, but as shown in FIG. 3, the invention can also be applied to a two-circuit power transmission line. In addition, in FIG. 3, the same parts as in FIG. 2 are indicated with the same symbols,
The explanation thereof will be omitted here. However, in FIG. 3, 14 is the inter-line distributed capacitance.

The admittance matrix obtained from the distributed capacitances 3, 4, and 14 of the two-line power transmission lines 1, 1 shown in FIG. If the phase currents are i _a , i _b , and i _f , then the following equation (4) is obtained for equation (1).

i _a i _b・ i _f = Yaa −Yab ・ −Yaf −Yab Ybb ・ −Yaf ・ ・ ・ ・ −Yaf −Ybf ・ YffVa Vb ・ Vf …(4) On the other hand, the admittance matrix of the control reactor is given by equation (2). In contrast, the following equation (5) is obtained.

i _a ′ i _b ′ ・ i _f ′＝ Yaa′ −Yab′ ・ −Yaf′ −Yab′ Ybb′ ・ −Ybf′ ・ ・ ・ ・ −Yaf′ −Ybf′ ・ Yff′Va Vb ・ Vf …(5) Now, one phase of the power transmission line of one line (for example, A phase)
The secondary arc current I when is grounded is Vd=Va, Ve=Vb, Vf considering that it is a two-circuit transmission line.
The condition =Ve can be obtained from equation (6) by substitution.

I=−(Yad+Yad′)Vd −(Yab+Yae+Yab′+Yae′)Vb −(Yac+Yaf+Yae′+Yaf′)Vc…(6) Therefore, the above equation (6) is slightly more complicated than equation (3), but ( 6) From equation 6), it is possible to find the conditions that minimize the secondary arc current I, so even in the case of two circuits,
Control to minimize the secondary arc current is possible in the same way as in the line.

Also, in Fig. 3, a separate control reactor 6 is connected between the neutral point of the transformer and the ground, but that control reactor may be shared, or even used as a simple reactor (3) and (6). Since the conditions for minimizing the secondary arc current can be obtained from the equation, the same effect as described above can be obtained.

Furthermore, although a Y-Δ connection was considered as a transformer connection, if the connection has a zero-sequence current path on the secondary side, this effect will not be affected in any way.

As explained above, according to the present invention, the conditions for minimizing the secondary arc current are calculated based on the signal from the fault phase detection circuit, and the value of the control reactor is controlled based on the calculated conditions. A reactive power compensator can be provided that can easily minimize secondary arc current in any ground fault and can enable high-speed reclosing of power transmission lines.

[Brief explanation of drawings]

Fig. 1 is a circuit configuration diagram showing a state in which reactive power compensation equipment is connected to a power transmission line, Fig. 2 is a circuit configuration diagram showing one embodiment of the present invention, and Fig. 3 is a circuit diagram showing another embodiment of the present invention. FIG. 3 is a circuit configuration diagram. 1...Power transmission line, 3...Ground distribution capacitance of the power transmission line,
4...Distributed capacitance between conductors of power transmission line, 5...Transformer,
6, 7... Control reactor, 8... Ground failure phase detection device, 10... Current calculation device, 9... Voltage detection device, 1
1... Current measuring device, 12... Pulse generation circuit.

Claims (1)

[Claims] 1. In a reactive power compensation equipment in which the primary side of a transformer is connected to a power transmission line, a reactor is connected between its neutral point and the earth, and a control reactor is connected to the secondary side of the transformer, A ground fault phase detection device that detects a ground fault phase when a ground fault occurs on the power transmission line; a reactor terminal voltage detection device that detects the terminal voltage of the control reactor; and an admittance determined from the distributed capacitance of the power transmission line. The admittance matrix determined from the matrix and the reactive power compensation equipment is stored, and when the ground phase is detected by the ground fault phase detection device, the secondary arc current based on the ground phase is determined from the conditions determined from both admittance matrices. The minimum value of the control reactor is calculated, and the current that flows when the value of the control reactor reaches the calculated value based on the value of this control reactor and the voltage value detected by the reactor terminal voltage detection device. a current calculation device that calculates
A current measuring device that measures the current flowing through the control reactor; and a signal based on a difference between a signal corresponding to the current calculated by the current calculating device and a signal corresponding to the current measured by the current measuring device. A reactive power compensator comprising: a control circuit that controls impedance of the control reactor.