HU180542B - Device for suppressing arc-current and limiting over voltages on the very high voltage ac transmission line - Google Patents

Description

FIELD OF THE INVENTION The present invention relates primarily to apparatus for suppressing arc current and limiting overvoltages in a high voltage AC transmission line.

The equipment is mainly used for automatic reconnection of high-voltage AC transmission lines with shunt and neutral chokes.

Known devices for arc current suppression and overvoltage control used in high-voltage AC transmission lines have either the overvoltage limitation function in automatic three-phase reset or arc suppression in automatic single-phase reset. In addition, it is not possible for any known device to test the restoration of complete electrical insulation strength of a damaged phase of a transmission line, while the use of a neutral inductor with constant inductance reduces the efficiency of arc suppression depending on the power transmitted through the line. In order to increase the efficiency of the auto-reclosing of the power transmission line, a complex apparatus is required which operates in both single-phase and multi-phase disturbances in the transmission line.

It is known to provide a device for suppressing arc current and limiting overvoltages on a high-voltage AC transmission line having at each end a unit for automatically switching the line and having channels for 5-phase and 3-phase control, and a device for overloading and neutralizing comprising at least one group of a protective element, the common point of the choke and the protective element being connected to the center of the respective three-phase group of shunt chokes connected to the phase of the transmission line (Grosa L., Crístovici A., Neskulesku DS, Ionescu A .:

Single-pole reclosing on EHV systems, CIGRE, 1974, rep. 31-03.).

Said device does not limit the overvoltage during automatic three-phase reset and is not reliable due to the constant current flowing through the neutral photo coil and relay protection required. When the equipment is damaged, the transmission line shuts off, which can then be operated normally without the neutral choke. In addition, due to the low voltage induced by the two non-damaged phases of the transmission line during the single-phase auto-reclosing cycle, it is not possible to determine with sufficient certainty the restoration of the complete insulation of the off-phase.

180,542

The object of the invention is to provide an apparatus for suppressing arc current and limiting overvoltages on a very high voltage AC transmission line, which enables to increase the reliability of the equipment, to increase the efficiency of the automatic switch-off, to reduce the optimum adjustment of the neutral choke according to the transmitted power.

SUMMARY OF THE INVENTION The present invention is solved by providing an apparatus for suppressing arc current and for overvoltage control of high-voltage AC transmission lines, having at each end of the transmission line a means for automatically reconnecting the line having channels for single-phase and three-phase control, in at least one group consisting of a neutral choke and a parallel-connected surge protector, the common point of the neutral choke and the surge protector is connected to the center of a corresponding three-phase group, which three-phase group is connected the number of switching devices corresponding to the number of neutral chokes with automatic control circuits each of which is connected in parallel with the respective neutral choke, and the circuits for automatically controlling the switching device on and off are electrically connected to a unit for automatic resetting.

Preferably, the apparatus comprises a delay element which electrically connects the circuit for automatically controlling the switching device to the one-phase control circuit of the automatic switch-off unit, and the circuit for automatically controlling the switch-off device to be electrically connected to the single-phase control unit.

Preferably, the apparatus comprises a resistor connected in series with the switching device and a delay member which electrically couples the circuit for controlling the switching device shutdown to the three-phase control channel of the automatic switching unit and the circuit for automatically controlling the switching device to switch on. with its three-phase control channel.

Preferably, the apparatus further comprises a second delay element having a trigger input for a single-phase control channel of the auto-reset unit and an output for connection to an auto-control circuit for switching off the switching device.

Preferably, the apparatus comprises a current meter connected in series with the switching device and the control input of the second delay element is connected to the output of the current meter.

The apparatus preferably comprises an additional switching device connected in series with a resistor and provided with automatic on / off control circuits which are connected in parallel with the neutral choke and three further delay elements, two of which are electrically coupled to automatically control the on and off circuit. implementing a single-phase control channel of the auto-off unit, and the third delay element providing an electrical connection between the circuit for automatically controlling the main switching device and the three-phase control channel of the auto-switching unit, and the circuit for automatically controlling the switching of the main switching device. automatic reset unit rear mphase control channel.

Preferably, the apparatus comprises a comparator unit which compares electrical signals generated by the switching device when the choke coil is shunted during the damaged phase of the power transmission line, and the comparator unit input is electrically connected to the transmission line phases, one of its outputs being switched, while its other output is connected via a switch to a single-phase control channel of the auto-reclosing unit and is electrically connected to circuits for automatically controlling the on / off switch of the main switching device.

Preferably, the neutral choke has adjustable inductance.

The incorporation of a switching device controlled by an automatic reset unit via a delay element into the equipment for arc suppression and overvoltage control on the ultra-high voltage AC transmission line allows for increased reliability by shutting down the unit during normal operation and there is no current flowing through it. In addition, switching on the switching device makes it possible to reduce the forced voltage on the switching phase by about 10% during the automatic one-phase switching cycle just prior to switching on.

The use of a second delay element in the switching circuit breaker circuit enables control of the switch-off time and thereby provides accelerated damping of the DC component of the arc current.

The switchgear circuit of the current meter is-25

Application to 180 542 V allows control of the damping of DC components and that shutdown can be performed when this component reaches a predetermined value.

The resistor applied in the switchgear circuit allows the equipment to be extended, i.e. to further limit overvoltages during automatic three-phase reset, while fully maintaining the efficiency of the unit during automatic one-phase reset.

The apparatus with both a shunt switching device and a switching device with a single-resistance circuit enables the construction of a high-reliability device that does not require relay protection, and the forced voltage is reduced during both automatic single-phase and three-phase reset.

The use of a unit for comparing electrical signals in the apparatus allows the status of the phase of the transmission line to be switched off in an automatic single-phase reset cycle. This is achieved by reconnecting the neutral throttle switching device after the arc current has been extinguished. Meanwhile, a voltage approaching the rated voltage is induced on the off phase, which can be reliably judged to completely restore the electrical strength of the phase.

The adjustable inductance neutral choke provides optimum adjustment for all possible transmissions.

The invention will now be described in more detail with reference to embodiments and drawings. In the drawings it is

Fig. 1 is a schematic diagram of an apparatus for suppressing arc current and limiting overvoltages in a high-voltage AC transmission line during automatic single-phase reclosing,

Fig. 2 is a schematic diagram of the apparatus of the invention according to Fig. 1 for three-phase automatic reset, a

Fig. 3 is an embodiment of an apparatus for arc suppression and overvoltage limitation in accordance with the present invention, which comprises a shunt switch during normal operation of the transmission line, and

Fig. 4 is a device according to the invention according to Fig. 3, which is also suitable for checking the state of the off phase.

The apparatus for suppressing arc current and limiting overvoltages on the ultra-high-voltage AC transmission line comprises a set of exemplary embodiments of a given embodiment, consisting of a parallel neutral neutral choke 1 and a surge protection element 2 (Fig. 1). As a surge protector 2, a drain valve or a non-linear resistor can be used. The common point of the neutral choke 1 and the surge protection element 2 is connected to the center 3 of the three-phase group of shunt chokes 4 connected to phases A, B, C of the transmission line 5.

At each end of the transmission line 5 there is provided a unit 6 for automatic resetting, which is provided with channels for single-phase and three-phase control (7-channel for single-phase control in the embodiment shown). At each end of the transmission line 5 are switches 8 for controlling each phase, which are controlled by the respective units 6.

The device comprises a switching device 9 with circuits 10, 11 for automatic control of the switching on and off, which is connected in parallel with the neutral choke 1. Circuits 10, 11 of the automatic control are electrically connected to the unit 6 for automatic resetting.

During normal operation of the transmission line 5, the switching device 9 is closed and the neutral choke 1 does not operate.

The device also includes a delay element 12 which provides an electrical connection to the channel 7 of the unit 6 for controlling the switching device 9 automatically. Here, the circuit 11 for automatically controlling the switching off of the switching device 9 is electrically connected to the channel 7 of the unit 6.

The device comprises a second delay element 13 for quicker damping of the DC component of the arc current, the trigger input 14 of which is connected to the channel 7 of the unit 6 and the output of which is connected to a circuit I1 for automatically controlling switching device switching off.

To control the damping of the DC component of the arc current, the apparatus includes a current meter 15 connected in series with the switching device 9, wherein the control input 16 of the second delay element 13 is connected to the output of the current meter.

In order to limit the overvoltage during the automatic three-phase reset, the device includes a resistor 17 connected in series with the switching device 9 (Fig. 2). The device is also provided with a delay element 18 which provides an electrical connection of the circuit 11 for automatically controlling the switch-off of the switching device 9 with the channel 19 for the three-phase control of the automatic switch-off unit 6. Here, the switching control circuit 10 is also electrically connected to channel 1B of unit 6. During normal operation of the transmission line 5, the switching device 9 is open and the neutral choke 1 operates.

In order to limit overvoltage and increase reliability during automatic three-phase reclosing, the unit is connected in series with 20 resistors (Fig. 3) and on,

180 542 comprises a switching device 21 with circuitry 22 and 23 for automatic shut-off control, which is connected in parallel with the neutral choke 1. There are also three further delay elements 24, 25 and 26, wherein the delay elements 24 and 25 provide electrical connection of the circuits 22 and 23 to the channel 7 of the unit 6, and the delay element 26 connects the circuit 10 for automatically controlling switching device switching. With 19 channels. Here, the circuit 11 for automatically controlling the switching off of the switching device 9 is connected to the channel 19 of the unit 6. During normal operation, the switching devices 9 and 21 are closed and the neutral choke 1 does not operate.

For checking the off phase of the transmission line 5, the apparatus includes a comparator unit 27 (Fig. 4) which compares the electrical signals generated by the switching device 9 when shunting the neutral choke 1 in the defective phase of the transmission line. Here, the input of the comparator unit 27 is electrically connected to the phases A, B, C of the transmission line 5 and its output 28 is connected to the unit. The other output 29 is connected via switch 30 to the output of channel 6 of unit 6 for single-phase control and is electrically connected to circuits 10, 11 for automatic control of switching device 9 on / off.

For maximum suppression of the arc current, the neutral choke 1 is configured with adjustable inductance in all operating conditions of the transmission line.

1-4. FIGS. 6A to D show arrows D caused by single-phase interference.

The equipment described in the embodiments of the following examples, in the event of various malfunctions, operates as follows:

If a single-phase short-circuit occurs in the transmission line 5 (FIG. 3), for example, in phase C, the auto-reclosing units 6 switch off the faulty phase C of the transmission line 5 via the switch 8 using channels 7 for single-phase control. At the same time, the channel 7 of the unit 6 receives an instruction on the circuit 11 for automatically controlling the switching device 9 and the circuit 23 for automatically controlling the switching device 21 off. Here, the switching device 9 is deactivated without delay, or after a predetermined time if the delay element 13 is used. When the switching device 9 (Fig. 1) is switched off without a time delay, the neutral choke 1 is immediately connected to the arc circuit. The DC component of the arc current, the magnitude of which depends on the number of connected shunt choke coils and the phase of current flowing therein, influences the arc burn time and thus the desired non-current break time of the automatic single-phase reset.

In many cases, the circuitry for most of the DC component of the arc current is: defective phase 4 shunt chokes - 4 faultless phase A and B shunt chokes - source (not shown in Figure 3) - arc D faulty phase C 4 shunt chokes. This circuit is formed because of less effective resistance than the following circuit: defective phase C shunt choke 4 - arc suppressor - arc D defective phase C choke. Due to the above, the DC component of the arc current attenuates with a significant delay of 1-2 seconds. In order to eliminate this phenomenon, the delay element 13 is used in the apparatus in the circuit 11 for automatically controlling the switch-off of the switching device 9. When an instruction is received from the channel 7, the delay element 13 provides a delay in switching off the switching device 9. As a result, the bypass circuit of the DC component of the arc current is shunted and the arc burn time is reduced accordingly. Further reduction of phase current can be achieved by using a current threshold element as the delay element 13. The delay element 13 is set to a current level that reliably extinguishes the arc current, and when this level is reached it is possible to switch off the switching device 9. This automatically takes into account the fact that the initial value of the DC component of the arc current and consequently the damping time is dependent on the instantaneous current of the shunt choke 4 at short-circuit and varies over a wide range. The use of a current threshold element in each particular case ensures a minimum break time of the automatic single-phase switching.

An additional effect of the switch-off delay of the switching device 9 is the less stable state of the arc current due to the earlier occurrence of the total arc current n. This is because the arc current has a high AC component relative to the compensated arc current when the switching device 9 is momentarily switched off.

The switching device 21 (Fig. 3) is deactivated with a delay defined by the delay element 25. This period is determined by the condition of damping the DC component after the switching device 21 is switched off without delay. When using the delay of the delay element 13 when the switching device 9 is switched off, the delay of the delay element 25 is selected to be smaller than the delay element of the delay element 13.

After switching off the switching devices 9 and 21, the neutral choke 1 is put into operation, which suppresses the arc current and limits the return voltage of the switched off phase C. After the auto-off time has elapsed, the units 6 switch on phase C through the channels 7 via the switches 8 at each end of the transmission line 5. The switching device 9 shuts off the neutral choke 1 by switching it on

180 542 following a command from an automatic control circuit 10 of a chute after a period of time defined by the delay element 12 initiated by the channel 7 of the unit 6. This delay is chosen to be greater for the equipment of Figures 1 and 3 than for the non-current break time of the automatic single phase reset.

The switching device 21 is closed by a command from the channel 7 of the unit 6 via the delay element 12. Here, the delay of the delay element 24 is greater than that of the delay element 12.

The use of a device having a comparator unit 27 (Fig. 4) allows the condition of the off phase to be checked at a voltage close to the rated value to determine the recovery of the total electrical insulation strength of the faulty phase. This is achieved by selecting the delay of the delay element 12 approximately equal to the expected burn time of the arc. To generate a high voltage, an instruction turns on the switching device 9 which shunt the neutral choke 1. Meanwhile, the voltage induced by the two switched phases on the off phase varies greatly due to the change in phase capacitance compensation of the transmission line 5. The voltage change is pulsed with an amplitude of about twice the steady state value of the voltage induced on the fault-free phase. Since the voltage is checked on the off phase, and this voltage is compared to the voltage that should be present on the off phase, it is determined that the off phase is faultless or that there has been repeated failure. The result of the comparison is transmitted from the output 28 of the comparator unit 27 to the unit 6 and used to disable it in the event of a further malfunction and to enable reconnection when the transmission line 5 is restored to its normal state.

If the transmission line 5 allows for not only one but several status monitoring cycles according to the stability conditions, the switching device 9 is repeated with a predetermined time delay when a malfunction occurs again from the output 29 to the switch 30. After the arc is extinguished, the neutral choke 1 is again shunted, the electrical signal at phase C off is compared with the predetermined signal, and the phase C state is determined.

2, the neutral choke 1 is permanently coupled to the center 3 of the shunt 4, immediately after switching off phase C by means of switches 8 at the ends of the transmission line, the phase capacities of the transmission line 5 are compensated and accordingly the arc quenching and limiting the return voltage on phase-out.

In order to more effectively compensate for the phase capacities of the transmission line 5 (Fig. 4), it is advisable to form the neutral choke 1 with adjustable inductance. This provides an opportunity to change the compensation of the electrostatic and electromagnetic components in the arc current by varying the power transmitted by the transmission line 5 from zero to a maximum so as to obtain a minimum value of the total arc current, thereby increasing the efficiency of arc suppression.

Note that if more than one of the three-phase groups of the shunt chokes 4 is present on the transmission line 5, the switching of the device may conveniently be accomplished in the zero conductors of each or at least two three-phase groups of the shunt chokes.

In the event of any multiphase interference on the transmission line 5 (Fig. 2), the auto-reconnect units will switch off each of the three phases A, B, C of the transmission line 5 via the switch 8 via the three-phase control channel 19 at each end. Simultaneously, the channel 19 of the unit 6 receives an instruction on the circuit 10 for automatically switching on the switching device 9 so that the resistor 17 is connected to the center of the shunt choke 4. This causes the charge to drain from the transmission line during the non-current break of the automatic three-phase reset. The delay time of the delay element 18 is selected to be approximately the same as the duration of the power-free break. After this time has elapsed, the circuit 11 for automatically switching off the switch is commanded and the switching device 9 is switched off. The value of the resistor 17 is selected according to two main parameters:

- ensuring a substantially complete discharge of the charge from the transmission line 5 during the power-off period of reconnection;

- limiting the voltage of the center 3 of the shunt choke 4 according to the insulation class.

Thus, due to the connection of the resistor 17, the charges are discharged from the transmission line 5 during the non-current break and the overvoltages generated when the transmission line 5 is switched on are reduced to twice the rated value.

In the embodiment of the apparatus shown in FIG. 3, at the same time as the transmission line 5 is switched off, the channel 19 of the unit 6 is instructed to automatically switch off the switching device 9 so that a resistor 20 is connected to the center 3 of the shunt. This ensures that an effective resistor is inserted into the discharge circuit of the transmission line 5. The time of resistor insertion 17 is determined by the delay element 26 in the circuit 10 for automatically switching on the switching device 9 and is similar to the delay time of the delay element 18 (FIG. 2) close to the duration of the power-free break.

Claims (8)

PATENT CLAIMS 1. An apparatus for suppressing arc current and limiting overvoltages on a high-voltage AC transmission line having at each end a unit for automatically switching the line and having channels for single-phase and three-phase control, and for receiving the device from a neutral choke and a pair of at least one group wherein the common point of the neutral choke and the surge protection element is connected to the center of a respective three-phase group of shunt chokes connected to the phases of the power transmission line, characterized in that the apparatus comprises a number of switching devices (9) have circuits (10, 11) for automatically controlling on and off switches and are connected in parallel to the corresponding circuits (10, 11) for automatically controlling switching and switching of the switching device (9) are electrically connected to the auto-switching unit (6). An embodiment of the device according to claim 1, characterized in that it comprises a delay element (12) which electrically connects the circuit (10) for automatically controlling the switching on of the gating device (9) and the one-phase control for the automatic switching-on unit (6). and a circuit (11) for automatically controlling the switch-off of the switching device (9) is electrically connected to the single-phase control channel (7) of the automatic reset unit (6). An embodiment of the apparatus according to claim 1, characterized in that the switching device (9) comprises a resistor (17) connected in series and a delay element (18) electrically connecting the circuit (11) for automatically controlling switching device switching off and and a circuit (10) for automatically switching on the switching device (9) and electrically connected to the three-phase control channel (19) of the switching device (9). An embodiment of the apparatus according to claim 2, characterized in that it comprises a second delay element (13) having a trigger input (14) for a single-phase control channel (7) of an automatic reset unit (6) and an output of the switching device (9). ) is connected to a circuit (11) for automatically controlling the switch-off. An embodiment of the apparatus according to claim 4, characterized in that the switching device (9) comprises a current meter (15) connected in series and the control input (16) of the second delay element (13) is connected to the output of the current meter (15). An apparatus according to any one of claims 2, 4 or 5, characterized in that the switching device (21) is connected in series with a resistor (20) and has circuits (22, 23) for automatic control of the on and off. are connected in parallel with the neutral choke (1) and include three further delay elements (24, 25, 26), two of which are delay circuits (23, 22) for automatically switching on and off connecting the unit (6) to the single-phase control channel (7), and the third delay element (26) electrically coupling the switching device (9) automatic switching control circuit (10) to the three-phase control channel (19) of the automatic switching unit (6). ) and also switching off the switching device (9) The automatic control circuit (11) is connected to the three-phase control channel (19) of the automatic reset unit (6). An apparatus according to any one of claims 1, 2, 4, 5 or 6, characterized in that, in the damaged phase of the transmission line (5), when the neutral choke (1) is shunted, the switching device (9) comprising an electrical signal comparison unit (27), wherein the input of the comparison unit (27) is electrically connected to the phases (A, B, C) of the transmission line (5), one of its outputs (28) to the input of the automatic reset unit (6). connected, while its other output (29) is connected via a switch (30) to a single-phase control channel (7) of the automatic reset unit (6) and is electrically connected to circuits for automatically switching the switching device (9) on and off. (10, 11). 8. Figures 1-7. An apparatus according to any one of claims 1 to 6, characterized in that the neutral photo coil (1) is formed with adjustable inductance.