RU2779875C1 - Method for controlling circuit breakers in high and extra high voltage networks with power electromagnetic devices - Google Patents

Abstract

FIELD: electric power industry.

SUBSTANCE: invention relates to the electric power industry. According to the method, in the process of monitoring the presence or absence of a unipolar current in the consumer circuits, the instantaneous values ​​of the unipolar current are additionally monitored. During repeating time intervals, high-frequency free oscillatory components of transient processes are filtered out. If, during the monitoring interval, the moments of current transition through zero value with a change in polarity are not detected and the instantaneous current values ​​are fixed only in the region exceeding the maximum allowable value of the direct switching current declared by the manufacturer of the circuit breaker, then the circuit breaker is blocked. If, during the monitoring interval, the moments of current transition through the zero value with a change in polarity or the entry of the instantaneous value into the region that does not exceed the maximum allowable value of the direct switching current declared by the manufacturer of the circuit breaker are detected, then the circuit breaker is allowed to open.

EFFECT: increasing the wear resistance of SF6 circuit breakers and preventing their damage.

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Description

The invention relates to the electric power industry and can be used to prevent damage to circuit breakers (for example, SF6), through which high (HV) or extra high (EHV) voltage is supplied to sections with high-voltage electromagnetic power devices, in particular, with shunt reactors or power transformers (autotransformers ).

When switching a power switch, electric currents arise in the circuit, containing forced and free components, including aperiodic ones. The resulting current in the circuit breaker circuit is unipolar for some time, i.e. has no zero crossings with polarity reversal. This is due to resonant conditions, certain values of the reactive resistances of electric overhead lines with shunt reactors installed on them, as well as parameters of the magnetizing current inrush, such as: the initial phase of switching on, the timing of switching on the phases of the switches, the mutual magnetic and current influence of the phases, the residual magnetization of the core. The unipolarity interval ranges from several power frequency periods to a few seconds, depending on the circuit parameters and scenario conditions.

Long-term non-switching off by the pole of the SF6 circuit breaker that does not pass through zero current due to the presence of a large aperiodic component in it leads to accidents with subsequent destruction of the switching equipment and, as a result, to the need for its prompt and costly replacement. The destruction of the circuit breakers is caused by prolonged arcing in the contact gap, which in turn leads to burnout of the contacts, overheating of the extinguishing gas, a sharp increase in its pressure and explosion of the circuit breaker, which causes damage to the surrounding equipment.

A known method for detecting aperiodic, essentially abrupt changes in the amplitude of at least one electrical parameter, in particular the current and / or voltage in the electrical network (Patent RU No. 2525082, publ. from the mains in case of faults that are accompanied by aperiodic changes in current and / or voltage, and to which other protective switches do not react.

The disadvantages of this technical solution are the inefficiency for switching circuit breakers of high (HV) or extra high (EHV) voltage, tk. an attempt to implement a trip when an aperiodic current component is detected will lead to the destruction of the circuit breaker under conditions of the flow of a unipolar current. The invention relates to a low voltage class (LV), where protective circuit breakers are used.

Technical solutions are known for controlling a power circuit breaker, especially a SF6 circuit breaker, in which the detection of the aperiodic component of the transient current is intended not to turn off the circuit breaker, but, on the contrary, to prevent it from being turned on under conditions when an attempt to implement switching of the circuit breaker by the command "turn off" in the interval of unipolarity of the current to be turned off has significant difficulties and is fraught with damage to the circuit breaker.

A method for damping the aperiodic component in the current of a linear switch is known, described in patent RU No. 118490 for the utility model "Device for damping the aperiodic component in the current of a linear switch" (published on 20.07.2012, IPC H02R 13/00), which provides damping before switching the SF6 circuit breaker ( or suppression) of the aperiodic component by installing shunt reactors in the neutrals, the so-called "pre-switching resistors", with the help of which the parameters of power circuits are radically changed and, as a result, the occurrence of long intervals of current unipolarity is excluded.

The disadvantages of this technical solution are the emergence of a new aperiodic current component when shunting the resistor, the unreliability of shunting resistors, unsuitability for inrush currents switching on power transformers and geoinduced currents.

There is a known method of suppressing the aperiodic component in the current of the linear switch, described in patent RU No. 117707 for the utility model "Device for suppressing the aperiodic component in the current of the linear switch" (published on June 27, 2012, IPC H01C 1/00), according to which, before switching the SF6 circuit breaker, it is provided suppression of the aperiodic component by installing a damping resistor between the output of the high-voltage switch and the output of the shunt reactor, the second output of which is grounded, the so-called "pre-switching resistor", with the help of which the parameters of power circuits are radically changed and, as a result, the occurrence of long intervals of current unipolarity is excluded.

The disadvantages of this technical solution are the emergence of a new aperiodic current component when shunting the resistor, the unreliability of shunting resistors, unsuitability for inrush currents switching on power transformers and geoinduced currents.

The closest in technical essence to the proposed invention is a method for controlling SF6 circuit breakers in HV and SVN networks (publ. JP No. 2000188044, pub. 04.07.2000, IPC H01N 33/59), according to which the aperiodic current component is detected and minimized due to controlled switching, which involves setting the switch to turn on at the moment of the maximum value of the mains voltage. In order to increase the life of the circuit breaker, a controlled shutdown is implemented under the condition of sinusoidality and the possibility of predicting the shape of the emergency current or load current curve and generating a command to turn off ahead of the time of the circuit breaker operation until the current passes through zero. Thus, it is possible to control the parameters of transient processes during switching or to exclude unipolar current intervals.

The disadvantages of this technical solution is the low efficiency of control due to switching overvoltages on the line insulation and on the equipment connected to the line, since the inclusion of the source voltage in the maximum leads to the largest transient component; formation at the moment of switching on the line of an additional aperiodic component of the current in the linear switch; the impossibility of implementing a controlled shutdown during saturation of electromagnetic current transformers, which occurs especially sharply with sharply non-sinusoidal forms of the primary current;

In addition, this technical solution does not take into account the modes that are accompanied by the occurrence of unipolar aperiodic currents and the subsequent destruction of the switch:

- short circuits (SC) on overhead lines (VL), when there is a non-selective shutdown of the shunt reactor switch of the damaged phase of the same name;

- close short circuits on overhead lines or on buses, with one-sided energization of the transformer (autotransformer) network and the presence of a current surge with subsequent disconnection of the circuit breaker;

- geoinduced currents in circuits of networks with a repeatedly grounded neutral with a period duration of about hundreds of seconds and an amplitude from units to tens and even hundreds of amperes, which lead to failure of the primary equipment and, when superimposed on the main frequency, can cause long unipolarity intervals.

- damped oscillatory processes of recharging capacitive and inductive elements under conditions of disconnected reacted VL VN (SVN).

The technical objective of the proposed invention is the implementation of a controlled adaptive delay in switching off the power circuit breaker of high and extra high voltage, depending on the shape of the curve of the current to be switched off.

The technical result consists in increasing the efficiency of control of SF6 circuit breakers and, as a result, increasing their wear resistance and preventing damage to such circuit breakers.

This is achieved by the fact that in the known method of controlling switches in high and extra high voltage networks with power electromagnetic devices, according to which the presence or absence of a unipolar current is controlled in consumer circuits, and if it is present, the switch is turned off with a time delay until the moment of current transition is detected. through the zero value with a change in polarity, in the process of monitoring, the instantaneous values of the unipolar current are additionally monitored, the specified control is carried out for repeating time intervals, in each of the control intervals, high-frequency free oscillatory components of transients are filtered out, while if during the control interval no transition moments are detected current through the zero value with a change in polarity and fix the instantaneous current values only in the region exceeding the maximum allowable value of the direct switching current declared by the manufacturer of the switch, then b they block the circuit breaker trip, and if during the monitoring interval they detect the moments of the current passing through the zero value with a change in polarity or the entry of the instantaneous value into the region that does not exceed the maximum allowable value of the direct switching current declared by the circuit breaker manufacturer, then the circuit breaker is allowed to open.

In this case, the duration of the control intervals is set in the range of 12-15 ms. The current is controlled on the HV or SVH side in each phase of the overhead line, and for receiving control signals and transmitting control signals by switches, direct and reverse radio channels are used. The current is controlled at the ground potential in the neutral circuit of power transformers (autotransformers) or shunt reactors from the side of zero terminals, and direct and reverse wired communication channels are used to receive control signals and transmit control signals to switches.

The circuit breaker opening is blocked using a blocking device, which is constantly kept in sleep mode and switched to a time-limited active mode by control commands, while the commands are generated according to relay protection and automation algorithms or operational control.

Switch off is blocked when a quasi-permanent geoinduced current is detected, caused by a change in the geomagnetic field during geomagnetic storms, reaching hundreds of amperes with a frequency of 0.0001 to 0.1 Hz, having long non-transitions through zero, dangerous for SF6 circuit breakers. They also block the switch off when an aperiodic current component is detected at close short circuits on the overhead line or on the tires, when the transformer (autotransformer) network is energized one-sidedly and there is a current surge. They block the shutdown of the reactor switch in case of a short circuit on the overhead line or on the tires, when non-selective shutdown of the switch of the shunt reactor of the damaged phase of the same name is possible.

The essence of the invention is illustrated by drawings, where in Fig. 1 shows a general block diagram of a device that implements the proposed method when controlling the current on the HV or EHV side in each phase of the overhead line (HV) circuit breaker (the diagram is displayed for only one phase), in Fig. 2 shows a general block diagram of a device that implements the proposed method when controlling the current at the earth potential in the neutral circuit of power transformers (autotransformers) or shunt reactors, in fig. 3 shows the timing diagrams in the absence of current transitions through the zero value and the presence of the “Disable” command signal from the operational control, where a is the operation (algorithm) of the blocking device, b is the timing diagrams of signals explaining the implementation of composite operations, in Fig. 4 shows the time diagrams of switching on the overhead line and short circuit at the time t = 0.3 s, until the aperiodic component of the current decays, where a is the operation (algorithm) of the blocking device, b is the time diagrams of signals explaining the implementation of composite operations.

A device that implements the proposed method for preventing damage to SF6 circuit breakers, shown in Fig. 1 and 2, contains a power supply source 1 connected by means of a SF6 circuit breaker 2 to a consumer (reactive load) 3 in the form of a power electromagnetic device, for example, a shunt reactor or a power transformer (autotransformer), a separate switch control cabinet (SHUV) 4, which receives control actions from the human-machine system for managing the configuration of the electrical network (CS) 5, which is configured to transfer control actions to the blocking device (UB) for turning off the switch 6 by means of forward and reverse channels of the radio communication node 7.

A distinctive feature of the device shown in Fig. 2 is the location of the blocking device for switching off the circuit breaker 6 (CB) not under the potential of the EHV, as implemented in FIG. 1, but in the neutral network of a power transformer (autotransformer) or reactor.

The method of controlling switches in high and extra high voltage networks with power electromagnetic devices is carried out as follows.

In different parts of the electric power systems, there are sections in which HV (EHV) from the power supply 1 through the SF6 switch 2 is supplied to the section with the power electromagnetic high-voltage apparatus 3, in particular, a shunt reactor or a power transformer (autotransformer). The control of the SF6 circuit breaker 2 is carried out through the SHUV 4 equipment, which implements the “Enable” or “Disable” commands of the control system 5 by the configuration of the electrical network. Control commands in CS 5 are formed automatically according to the algorithms of relay protection and automation, as well as by the person performing the functions of operational control.

When switching the SF6 circuit breaker 2, electric currents arise in the circuit, containing forced and free components, including aperiodic ones (Fig. 3, a). With a certain combination of values of reactive resistances of inductive and capacitive conduction of overhead lines with installed shunt reactors, or certain values of the initial phase of switching on, the timing of switching on the phases of switches, the mutual magnetic and current influence of the phases, the residual magnetization of the core of a power transformer (autotransformer) or reactor 3, which determine the parameters of the throw magnetizing current, the resulting value of the current in the circuit of switch 2 during the time when the current has a unipolar character, i.e. has no zero crossings with polarity reversal, extends to a duration from several periods of industrial frequency to units of seconds, depending on the circuit parameters and scenario conditions. An attempt to implement switching on the “open” command in the interval of unipolarity of the current to be switched off has known difficulties and is fraught with damage to the SF6 circuit breaker.

As already mentioned, measures have been developed and are being implemented in power systems aimed at preventing damage to power circuit breakers:

- circuit-mode, aimed at design constraints and determining the order of switching on the primary equipment;

- installation in circuits with switches or in neutral shunt reactors of the so-called "pre-switching resistors", which radically change the parameters of power circuits to ensure the suppression of free components and prevent the occurrence of long intervals of unipolarity;

- equipping the circuit breaker control cabinet equipment with an additional unit that ensures the implementation of controlled non-synchronous switching of the power circuit breaker in a given phase of the instantaneous value of the controlled electrical quantity, taking into account the operating time of the power circuit breaker drive.

The listed measures, however, have technical limitations of application and are characterized by the values of the failure rate parameter, therefore, in justified cases, they require redundancy.

Another source of unipolar currents should also be taken into account - geoinduced currents in circuits of networks with a repeatedly grounded neutral with a period duration in the region of hundreds of seconds and an amplitude from units to tens and even hundreds of amperes. The above measures cannot affect space (magnetospheric) phenomena, and at the same time, high-voltage networks of power systems must be resistant to the effects of geomagnetic disturbances - geoinduced currents and similar phenomena. Also, damped oscillatory processes of recharging capacitive and inductive elements in the conditions of disconnected reacted VL VN (SVN) or short circuit on VL, when there is a non-selective shutdown of the switch of the shunt reactor of the damaged phase of the same name, are also dangerous for switching.

To implement the function of blocking the shutdown of a unipolar current when switching a HV (SVN) switch, U B 6 is installed in the circuits of each phase. 7. If the current is controlled at the ground potential in the neutral circuit of power transformers (autotransformers) or shunt reactors, direct and reverse wire channels of the communication node 7 are used to receive control signals and transmit control signals to switches.

Upon receipt from SU 5 to SHV 4 commands "Enable" and/or "Turn off" the switch, the signal from SS 4 through the direct channel of the communication node 7 is transmitted to UB 6 command "Switch to active mode". Each UB 6 goes into active mode, performs self-control and through the reverse channel 7 reports readiness for action.

In the active mode, UB 6 generates and transmits via the reverse channel of the communication node 7 to the SHUV 4 the “Lock” signal in the case when, in the presence of a primary current, during the duration of the control interval (12-15 ms), the moments of current transition through zero value with a change are not detected. polarity and fix instantaneous current values only in the area exceeding the maximum allowable value of direct switching current, declared by the manufacturer of the switch.

If, in active mode, in the presence of a primary current, UB 6 detects in the control interval the moments of the current passing through the zero value with a change in polarity or the entry of the instantaneous value of the current into the region that does not exceed the maximum allowable direct switching current declared by the manufacturer of the circuit breaker, then via the reverse channel communication node 7 in SHUV 4 is transmitted signal "Permission" switching.

It should be noted that both the presence (absence) of the moments of current transition through the zero value, and the excess (non-exceedance) of the instantaneous current value of the maximum allowable direct switching current are fixed by the microprocessor controller, which is part of UB 6. With the help of this controller, signals are also filtered, excluding high-frequency free oscillatory components of transients, which can lead to a false release of UB 6 during the flow of a unipolar current.

SHUV 4 generates commands for the drive of the SF6 circuit breaker 2 depending on the signals from the UB 6 and delays the "Disable" command in the presence of the "Lock" signal until the disappearance of the "Lock" signal and the appearance of the "Enable" switching signal. If you do not receive from the UB 6 on the reverse channel of the communication node 7 signal "Ready", the commands are implemented from the control system 5 according to the algorithms currently in force, for example, with a time delay.

We emphasize that in the practical implementation of this technical solution, blocking the trip of the SF6 circuit breaker 2 can be performed using the prediction of the decay time of the free aperiodic component of the turn-on current surge to values that are safe for switching, taking into account the intrinsic disconnection time of the connection.

On the oscillograms of Fig. 3 a, b illustrate the switching on of the overhead line and the "Turn off" command until the moment of attenuation of the aperiodic current component from the operational control, and in Fig. 4 a, b - switching on the overhead line and short circuit at the time t = 0.3 s, until the aperiodic component of the current is attenuated.

In FIG. 3a and fig. 4, and the signals are presented:

I - primary current with one-sided switching on of 750 kV overhead lines with 3 × 110 MVA SR;

II - commands from the control system 5, including from relay protection;

III - blocking off the unipolar current UB 6;

IV - switch positions 2.

In FIG. 3b and fig. 4b shows the signals representing the positions of the constituent organs involved in the implementation of the proposed method:

V - "Start" blocking device UB 6;

VI - active mode UB 6;

VII - "Block" from UB 6 to SHUV 4;

VIII - "Permission" from UB 6 to SHUV 4.

On the oscillogram of Fig. 3 a, b demonstrates the operation (algorithm) of UB 6 in the absence of current transitions through the zero value and the presence of the “Turn off” command signal from the operational control of the CS 5 system. In the presented phase, there is an aperiodic component with a time constant significantly exceeding the period of forced oscillations. Switching off the SF6 circuit breaker 2 of the overhead line in the interval of the unipolarity of the current curve causes a danger caused by the impossibility of breaking the arc due to the presence of an aperiodic component in the full current of the circuit breaker 2. This situation leads to damage to the circuit breaker 2 and possible failure of the overhead line VN (SVN), which is extremely negative affects the reliability of the power system. Algorithm UB 6 blocks switching in the interval of unipolarity of the current curve and SF6 circuit breaker 2 is successfully switched off after the aperiodic current component decays to safe values.

On the oscillogram of Fig. 4 a, b demonstrates the operation (algorithm) of UB 6 during a short circuit on an overhead line. The short circuit current also contains an aperiodic component, which in the limiting maximum case can be equal to the forced periodic component of the industrial frequency. Algorithm UB 6 allows switching in less than 10 ms after the occurrence of a short circuit, which in turn does not slow down the action of the relay protection and the SF6 circuit breaker 2 is successfully turned off.

Thus, the proposed method makes it possible to increase the efficiency of control of SF6 circuit breakers. This increases wear resistance and prevents damage to SF6 circuit breakers. The method is a conflict-free technical solution, its application has a positive effect on the overall reliability of the electric power system.

Claims (8)

1. A method for controlling SF6 circuit breakers in HV and SVN networks with power electromagnetic devices, according to which the presence or absence of a unipolar current is monitored in the circuits of the switches and, if present, the circuit breaker is turned off with a time delay until the moment of current transition through the zero value with a change in polarity is detected, characterized in that during the monitoring process, the instantaneous values of the unipolar current are additionally monitored, the specified monitoring is carried out over repeated time intervals, in each of the monitoring intervals, high-frequency free oscillatory components of transient processes are filtered out, while if during the monitoring interval the moments of current transition through zero are not detected value with polarity reversal and fix instantaneous current values only in the area exceeding the maximum allowable value of direct switching current declared by the manufacturer of the circuit breaker, then block the trip of the circuit breaker i, and if, during the monitoring interval, the moments of the current transition through the zero value with a change in polarity or the entry of the instantaneous value into the region that does not exceed the maximum allowable value of the direct switching current declared by the manufacturer of the circuit breaker are detected, then the circuit breaker is allowed to turn off. 2. The control method according to claim 1, characterized in that the duration of the control intervals is set in the range of 12-15 ms. 3. The control method according to claim 1, characterized in that the current is controlled on the HV or EHV side in each phase of the overhead line, and for receiving control signals and transmitting control signals by switches, direct and reverse radio channels are used. 4. The control method according to claim 1, characterized in that the current is controlled at the ground potential in the neutral circuit of power transformers / autotransformers or shunt reactors from the side of zero terminals, and for receiving control signals and transmitting control signals by switches, direct and reverse wired communication channels are used . 5. The control method according to claim 1, characterized in that the circuit breaker trip is blocked using a blocking device, which is constantly kept in sleep mode and switched to a time-limited active mode by control commands, while the commands are generated according to relay protection and automation algorithms or operational management. 6. The control method according to claim 1, characterized in that they block the switch off when a quasi-permanent geoinduced current is detected, caused by a change in the geomagnetic field during geomagnetic storms, reaching hundreds of amperes with a frequency of 0.0001 to 0.1 Hz, having long non-transitions through zero . 7. The control method according to claim 1, characterized in that it blocks the circuit breaker from opening when an aperiodic current component is detected at close short circuits on the overhead line or on the buses, when the transformer / autotransformer network is energized one-sidedly and there is a current surge. 8. The control method according to claim 1, characterized in that the shutdown of the reactor circuit breaker is blocked in the event of a short circuit on the overhead line or on the buses, when a non-selective shutdown of the shunt reactor circuit breaker of the damaged phase of the same name is possible.

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