Device for earth fault current compensation in three-phase electrical networks (versions)

FIELD: electricity.

SUBSTANCE: invention is used in electrical engineering. The device represents an earthing bipole - a tracking width-modulated voltage converter (a tracking PWM converter) attaching the neutral of the network feeding transformer to earth and forming lagging current for compensation of leading capacitance current of single-phase fault to earth, as well as a neutral current sensor, a network voltage transformer, a clock signal generator for measurement of network capacity and a calculation unit for determination of the required admittance of the above bipole. In addition to a common set of functional units, the tracking PWM converter is equipped with a current setting unit, the inputs of which are represented by neutral voltage and the required admittance, and the output of which is represented by current demand supplied to the current control input of the tracking PWM converter, and transfer function of the current setting device provides for lagging phase shift of about 90 degrees on network frequency.

EFFECT: improving quick action and enlarging functional capabilities.

9 cl, 46 dwg

 

The claimed technical solution relates to electrical engineering and intended primarily to offset current ground fault and arc-quenching in three-phase electrical networks with isolated neutral.

In three-phase electrical networks with isolated neutral Pets work equipment single-phase ground fault (single-phase earth fault up to 90% of the total number of injuries), but the fault current if is controlled. Based on operating experience, the fault currents to earth not more than 5...20 A (depending on the magnitude of the voltage) are valid and do not require immediate power-off.

In case of short circuit to earth of one of the phases of the electrical network (medium-voltage: 6, 10, 20 kV or high voltage: more than 20 kV) through a short flows capacitive current, which can have significant value and to keep the arc short circuit. This phenomenon was investigated Petersen [1], and he suggested the means to reduce the arc current short circuit - connection of the neutral of the supply transformer to ground through the coil (Petersen coil). The inductance of the coil (or conductivity - admittance) is chosen according to the resonance condition so that the lagging current of the inductance compensated ahead of capacitive current; when that is exactly what the current setting in place the circuit in the steady state should be zero. Since the Petersen coil is widely used in medium-voltage and high-voltage networks. In simple cases, can be used unregulated coil. In branched networks, where the capacity of the land may change, apply coil with taps, switching contactors [2, 3] or plunger-type reactors, the inductance of which is regulated by the movement of the magnetic shunt[4, 5, 6, 7]. Power arc suppression device QNdepends on the mains voltage and residual current compensation.

Lack of reactors with branches is the complexity of setting compensation due to the discrete change of inductance.

Disadvantages plunger reactors are large weight and dimensions, as well as the presence of the rotating and moving parts, which affects the reliability and durability of the reactor. The low speed of movement of the movable part of the reactor plunger type imposes limitations on their performance.

Also known reactors without moving parts, adjustable bias [8, 9, 10]. The developed device allows you to configure the adjustable reactor automatically, without operator[5, 7, 9, 10]. This applies to the auxiliary inverter generator test signal supplied to the network through additional ammo the ku reactor. In response to the test signal is determined by the network capacity on the ground and then set the appropriate value of inductance of the reactor.

However, the use of auxiliary Converter increases the cost of the arc quenching device as a whole.

To assess or other arcing devices fundamental fact is that these devices must operate in two different classes of situations. Coil Petersen successfully operates in situations of the first class, when a short circuit to earth stable (metal S.C.). In these situations, the steady state short circuit is established lagging sinusoidal current coil, which compensates fully or with some uncertainty ahead of the capacitive current and reduces the current and the dissipation in the gap short circuit. The voltage of the healthy phases relative to the earth are overrated intime. However, the network can continue to operate for some time; immediate interruption of power supply of consumers can be avoided. It is also possible and a more favorable outcome when under the influence of the current reduction in the amount of short circuit its dielectric strength is restored, and the restored and normal operation of the network.

<> More typical, however, the situation of the second class with a recurrent breakdown of the insulation between when the partial restoration of the electric strength of the gap should increase voltage on it, re-strikes, etc. Situation of this second class was considered by Peters and Slepian [11], Juvarly CM [12], Belyaev NM [13]. In situations with repeated breakdowns application of the Petersen coil is not a stable positive effect, as you might expect, since it is designed for steady-state mode.

To improve processes for repeated breakdowns it was proposed that the combined device in which the coil Petersen joins the resistor. Completed M. A. Ilyin's cartographic establishment al. study [14] demonstrated the beneficial damping effect of the resistor after repeated breakdowns. However, resistive damping is associated with some deterioration of the established processes. Thus, there is a contradiction. The resistor current is no offset and is added to the proceeding in the amount of short circuit current. The possibility of increasing the conductivity of the shunt resistor to improve the dynamics limited.

Closest to the claimed technical solution is a technical solution [10], which is used to manage the th bias electric reactor (UPAR) with automatic control system. UPAR has no moving parts and has a relatively high speed. The disadvantage of this technical solution is too high consumption of electrical materials (copper and electrical steel), large weight and dimensions, the need to use a special device for generating test voltages on the neutral of the transformer. Additionally, UPAR does not provide damping of high-frequency oscillations arising at the time earth fault after repeated breakdowns and contributing to the occurrence of the arc. Automatic control system WPAR has no ability to determine the time of termination of single-phase earth fault to exit the mode of compensation. This leaves the possibility of a resonant overvoltages when switching and other disturbances and reduces the level of network reliability.

The task, which directed the claimed technical solution is to give the arcing equipment, along with the basic, additional useful features such as the ability to identify network without the use of auxiliary equipment, fast transient suppression components of the current, including recurring breakdowns, accelerated decrease in the arc current, while eliminating the foregoing disadvantages inherent in UPAR [10].

PR is the solution of the problem technical result achieved is to reduce the material intensity arc suppression device, in the ease of operation and increase the stability of the network to ground short circuits.

The essence of this technical solution is to apply as an arc suppression device (instead of the regulated somehow reactor, or a combination of the reactor with a shunt resistor) active element - servo pulse modulated (pulse-width modulation, PWM) transistor voltage Converter, hereinafter referred to as servo PWM Converter. Current technology allows such converters required for Dagahaley parameters, and these converters if properly managed, they can mimic an adjustable inductance. The use of servo PWM Converter is consistent with the trends of modern technology and offers several advantages in itself, with simple playback in a new way the same functions. However, the application of the active element - servo PWM Converter is able to give more to ease the contradiction between the demand for good accuracy compensation with sustainable circuits and requirement of good damping when temporary disruptions.

Except where noted, there is another useful feature of the servo PWM Converter. In the previous review it was considered as a device for obtaining a lagging current, i.e. how similar governed by the second inductance. However, such converters are equally able to give and rapid current, so they should not be regarded as analogous to inductance or capacitance, but as a universal controlled reactive element. The change in the reaction of such a link from inductive to capacitive corresponds to changing the sign of the coefficient of conductivity Yn Converter as dvukhpolosnykh. When the coefficient of Yn through zero in the negative values Yn servo PWM Converter will issue ahead of the current, i.e. will become a similar capacity. When networking, this situation can occur if the conductivity of the reactor on the accession of another transformer will be more than required. Witness PWM Converter automatically eliminates excess, moving into a mode with a negative coefficient of conductivity Yn and the advancing shock. No switching or reconfiguration for transition from the inductive mode, the capacitive mode is not required. The ability of such a Converter to bilateral regulation can be used to build arc suppression device by price or other reasons.

In addition to the options arc suppression device on the basis of the Converter may be other options, the choice of which is due to feasibility considerations.

A good option is when part of the arcing which disorder is introduced unregulated coil on half power Q N/2 and servo PWM Converter on the same half-power QN/2. Regulation of the Converter full-scale range of ±QN/2 total admittance regulated in the full range from zero to the nominal value.

Similarly, by price or other some motives (for example, to run the Converter on low voltage) may be helpful to use a matching transformer.

It may also be useful to perform this transformer as the transformer-reactor, with a capacity of idling is equal to half the required nominal power arc suppression device. The required installed capacity servo PWM Converter also is half of the rated capacity.

We offer servo PWM Converter according to the structure such STATCOM (Statkom - static reactive power compensation - static compensator based on a voltage Converter). The main characteristic of STATCOM - the ability to generate current of any phase relative to the voltage. We offer servo PWM Converter can:

- work mode dvukhpolosnykh with a controlled impedance (admittance), which allows for compensation of capacitive currents and extinguishing of the arc, and fast controllers of the control system in combination with virtually instantaneous power semiconductor elements allow auth to obtain an effective suppression of higher harmonics, favorable flow transients as sustainable when shorted to ground, and after a temporary breakdowns,

- generate the neutral of the transformer test signals required power with any harmonic content required for accurate identification of parameters of a three-phase network, it does not require any additional equipment, in addition to the program area of the microprocessor in the control system, when the powerful capabilities of modern microprocessors not require any additional material costs,

- work mode dvukhpolosnykh that have the property to load the active character, i.e resistor (but without absorption and energy dissipation, except for small losses in the elements of the scheme), which allows to damp high-frequency vibrations that contribute to the emergence of overvoltage,

- to combine with the work of any of the above modes, for example, the mode of compensation of capacitive currents and the mode damping of the parasitic oscillations and surges, that is impossible when using a passive element, a reactor of any of the above types.

In accordance with the proposed technical solution, this task is solved in that in the known device the compensation current earth fault in three-phase electrical networks containing the m dvukhpolosnykh, connecting the neutral mains transformer with the ground and forming a lagging current to compensate for the rapid capacitive current of single-phase ground fault, and the current sensor neutral, transformer voltage, generator test signals for measuring network capacity and computing unit for determining the required admittance mentioned dvukhpolosnykh, according to the claimed technical solution as grounding dvukhpolosnykh applied servo pulse modulated Converter voltage (servo PWM Converter), is provided in addition to the usual set of functional units unit unit current, the inputs of which are the neutral voltage and the desired admittance, the way out is the job of the current supplied to the input of the regulator current mentioned servo PWM Converter, and the transfer function of the generator current provides a lagging phase shift of about 90 degrees at the network frequency.

In accordance with the proposed technical solution, this task is solved by the fact that the transfer function of the unit in addition to the reactive (first) component contains a damping proportional to the input signal component, which in the action of the Converter appears as a shunt resistor (virtual resistor).

In accordance with the proposed technically the solution to this problem can be solved by that the capacitor DC voltage servo PWM Converter (storage capacitors) made a "hung" (not attached to the source or the drain voltage of comparable power output), and the transfer function of the unit introduced an additional component (balance), generated based on the error voltage capacitor servo PWM Converter, and ensure the maintenance of their stresses around the nominal level.

In accordance with the proposed technical solution, this task is solved by the fact that the ground dvukhpolosnykh entered unregulated coil on half the required reactive power grounding dvukhpolosnykh (QN/2), connected in parallel to the servo PWM Converter, which is also executed on the same half-power (QN/2); and regulation witness PWM Converter in the full range of QN/2 to +QN/2 (leading by 90 degrees lagging currents up to 90 degrees currents) provides regulation total admittance in the full power range from zero to the rated values of QN.

In accordance with the proposed technical solution, this task is solved by the fact that the witness PWM Converter is connected through a matching transformer.

In accordance with paragraph shall izlaganim the technical solution of this task is solved by the what servo PWM Converter is connected through a matching transformer (transformer-reactor) with a capacity of idling QN/2.

In accordance with the proposed technical solution, this task is solved by the fact that the witness PWM Converter in parallel with performing the basic functions (compensation capacitive current) injects (injection) in the neutral network test current or test voltage, and the desired admittance is calculated in the control system in response to a test frequency in the neutral voltage.

In accordance with the proposed technical solution, this task is solved by the fact that the transfer function of the unit along with reactive (compensatory), damping and balanced components contains an additional component of the test signal with a frequency (ωtest), non-network (ωs) (for example, ωtest=0,5ωs)generated in the control system servo PWM Converter.

In accordance with the proposed technical solution, this task is solved by the fact that the test signal is the sum of two or more harmonic components of different frequencies, different from the network.

In accordance with the proposed technical solution, this task is solved in that the control system servo PWM Converter based on a strong signal to the aqueous processor, combines the functions device-specific compensation current earth fault in three-phase electrical networks (such as the generation of test signals, processing the responses to the test signals and the calculation of the required indicators), with non-specific (normal) control functions servo PWM Converter, thereby eliminating the need to use additional equipment.

For clarification, the following illustration.

Figure 1 shows the equivalent circuit (figure 1 from [3]) three-phase electric network with isolated neutral with arc reactor in neutral.

On figa presents well-known single-phase bridge circuit of the voltage Converter and the three-level AC voltage.

On figb presents well-known single-phase five-level diagram of the voltage Converter.

On figa and 3b presents known variants of the Converter voltage, made of modular multilevel scheme.

4 shows the scheme of an active arc suppression device, made on the basis of single phase servo PWM Converter.

Figure 5 shows a block diagram of three-DCB (D - damping, With payment, balance) knob current functional blocks which are based on a powerful signal processor.

Figure 6 presents one of the C possible implementation of the controller unit balance, part of the unit current.

On figa shows a network with two supply transformers with arc suppression coil on the first of them and with the witness PWM Converter in a second.

On figb shows the equivalent circuit for the neutral, presented at figa.

On Fig shows a variant of the arc suppression device in parallel operation of the fixed orifice and the witness PWM Converter.

Figure 9 shows a variant of the arc suppression device connected servo PWM Converter through a matching transformer or transformer-reactor.

Figure 10 presents the scheme of automatically reconfiguring arc suppression device with servo PWM Converter.

On figa presents a functional diagram for determining the resistive Gn and capacitive Yn components of the conductivity of the network and the desired ratio Yz conductivity compensation.

Fig 11b, the circuit network on the test frequency fIthat differs from the network frequency f.

On Fig presents a functional diagram for determining the resistive Gn and capacitive Yn components of the conductivity of the network and the desired ratio Yz conductivity compensation for the case when the servo PWM Converter operates in parallel with fixed arc reactor in the schema view figa or in the schemes of the form Fig, Fig.9.

Rhythm is and replace the network with arc-reactor [3], presented in figure 1 illustrates the basic principle of compensation current ground fault and arc-quenching. Arc reactor is connected to the zero point of the network and to the ground. The parasitic capacity of the phases relative to the earth marked Ca, Cb, Cc.

The device proposed technical solution - servo PWM-Converter is in its static state can be described using illustrations presented in figure 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12.

Witness PWM-Converter - for use in arc suppression device may be performed by any of the known circuits of converters voltage:

- single-phase bridge circuit with three levels of AC voltage (figa);

- single-phase five-level scheme (figb);

- modular multilevel scheme [15], (figa, 3b).

The choice of one or another of them is determined by the conditions of use. Pulse modulation must be sufficiently high frequency. Ripple pulse modulation are suppressed LC-filter (figure 2 and 3 not shown). Reactance X=ωSL and admittance Y=ωSC filter network frequency ωSnegligibly small. Witness PWM Converter is equipped with the usual set of blocks for the implementation of the servo PWM: driver transistors, sensors and powerful enough signal processor. The latter performs the functions of the modulator and the additional functionality required. Beings who nimi properties servo PWM Converter are as follows. The output voltage of the Converter vae(t) with sufficient accuracy repeats the reference signal vz(t); detracting from the scale can be written

In addition, in and of itself this is not accumulating and not scattering energy link (non-energetic; non-dissipativ); output power Converter Pae(t) coincides with the power flowing in the DC link voltage Pd(t):

(here denoted by vd, id- voltage and current in the DC link of the Converter, iae- output current of the Converter).

For modular multilevel circuit where capacitor few, in the last expression will include the amount of; when enlarged consideration instead of sum can be considered equivalent to a capacitor. For further consideration of the active element - servo PWM Converter is controlled quadrupole with two ports: AC vae, iaeand DC vd, iddescribed by equations (1, 2).

Active arc suppression device is formed (see figure 4) by attaching port AC single-phase voltage servo PWM Converter 1 between neutral mains transformer 2 and ground 3 in series with the current sensor 4. In relation to traffas the first AC power supply (figure 4 in a single view) it is a manageable dvukhpolosnykh. The port (or ports) DC voltage when using servo PWM Converter 1 in arc suppression device are connected only to the accumulating capacitor 5 (capacitors). Connection to a source or drain DC voltage commensurate power is not required; it is enough to have a connection to a low-power charger for pre-charging the capacitor 5. When used in arc suppression device witness PWM Converter 1 contains in addition to non-specific functional blocks, such as the modulator 6 (mdl), the controller 7 drives (regi), specific functional block unit 8 lagging current iz(t), denoted geniz. Figure 4 presents also included in the servo PWM Converter 1:

the Converter 9 voltage (power section, made in accordance with one of the options shown in figure 2 and 3),

- LC filter 10, the overwhelming surge pulse modulation,

the adder 11,

block 12 of the auxiliary power supply (bpsn), power system control,

Figure 4 shows also busbars 13 three-phase electric network switching devices 14 from the side of the supply transformer 2, and the consumers (figure 4 consumers not shown) and the transformer 15 voltage network.

Figure 5 shows a block diagram of three-DCB (D - damping, With payment, balance) knob 8 current iz(t), the functional blocks which are based on a powerful signal processor.

Structural scheme includes:

the adders 16, 17, 18,

- blocks the multiplication 19, 20, 21,

integrators 22, 23,

- block 24 of balance control,

unit 25 of the voltage regulator and energy storage capacitors 5 Converter 9 voltage.

Input signals knob 8 current signals calculated in the control system:

- vn - bias voltage neutral,

- Gdemp - conductivity coefficient of damping,

- Yz - required coefficient of conductivity compensation

- εz - nominal (rated) energy level storage capacitor (capacitor) 5,

- ud - current (measured) value of the voltage storage capacitor (capacitor) 5.

Figure 6 presents one possible implementation of block 24 of balance control. Block 24 balance control provides high-speed PID (proportional-integral-differential) controller 26 and a filter 27 of the second harmonic. The PID controller includes integral 28, 29 proportional and differential 30 units with constant time tint, t1, tdif, respectively. The outputs of the links 28, 29, 30 are summed in adder 31 with the corresponding coefficients 1, Kpr, Kdif. To reduce the ripple is filtered using a second harmonic using a synchronous filter. To this end the output signal GbalIthe adder 31 is supplied to the input of the filter 27 of the second harmonic. The output signal Gbal block 24 balance control is applied to one of inputs of the block 21 multiplication (see figure 5).

On figa shows a network with two supply transformers 32 and 2 with arc suppression coil 33 on the first of them and with the witness PWM Converter 1 on the second. On figb shows the equivalent circuit for the neutral that is used to identify the network settings in the control system servo PWM Converter 1, earthing the neutral of the second transformer 2. Equivalent circuit (figb) consists of enabled parallel to L, C and R values are calculated in the control system (in and vn - current and neutral voltage).

On Fig shows a variant of the arc suppression device in parallel operation of the fixed orifice 34, performed on half the required reactive power grounding dvukhpolosnykh (QN/2) and witness PWM Converter 1 on the same power (QN/2).

Figure 9 shows a variant of the arc suppression device connected servo PWM Converter 1 through a matching transformer 35.

Another possible option (scheme are the same as in Fig.9) is the implementation of the matching transformer 35 in the form of a transformer-reactor, with a capacity of idling is equal to half the desired nominal m is snasti arc suppression device (Q N/2). The required installed capacity servo PWM Converter 1 also is half of the rated capacity (QN/2).

Figure 10 presents the scheme of automatically reconfiguring arc suppression device with servo PWM Converter 1. Functions are locked loop block 36-locked loop microprocessor control system, including:

- sub 37 calculate the required admittance (coefficient of conductivity neutral) for active dvukhpolosnykh - servo PWM Converter 1,

generator 38 of the test signal.

As part of the control system for the purposes locked loop has an adder 39.

On figa presents a functional diagram for determining the resistive Gn and capacitive Yn components of the conductivity of the network and the desired ratio YZ conductivity compensation.

On figa indicated:

generator 40 (genθ)generating orthogonal sinusoidal pair of variables cosθ and sinθ, has a frequency of fIdiffers from the network frequency f,

- blocks the multiplication 41, 42, 43, 44,

the adder 45,

filters 46, 47 of the lower frequencies

block 48 calculate the resistive GnIand capacitive YnIthe components of the conductivity of the network on the test frequency fIdiffers from the network frequency f,

Fig 11b, the circuit network on the test frequency f Ithat differs from the network frequency f.

On Fig presents a functional diagram for determining the resistive Gn and capacitive Yn components of the conductivity of the network and the desired ratio YZ conductivity compensation for the case when the servo PWM Converter 1 operates in parallel with fixed arc reactor in the schema view figa or in the schemes of the form Fig, Fig.9. The scheme is constructed similar to the scheme on figa, differing from it by a double set of multipliers (added blocks multiplying 49, 50, 51) and low-pass filters (filters 52, 53), as well as entered by the adder 54.

The device operates as follows.

As noted above, the servo PWM Converter 1 contains (see figure 4) typically used in such devices, functional blocks: a modulator 6 and the controller 7 current. For use as an arc suppression device in witness PWM Converter 1 is introduced specific functional block unit 8 lagging current iz(t).

The controller 7 of the current building which is at a sufficiently high frequency modulation does not cause trouble, ensures the equality of the output current tracking PWM Converter 1 job: iae=iz;

Unit 8 current generates a variable iz(t), which in steady state is behind the bias voltage vn at an angle of about 90º.

Delahaye in parentheses is the essence of the voltage phases of the network, measured by the transformer 15 voltage network.

To obtain such a backward variable can be used as the transfer function of the knob 8 current simply a function of admittance coil Petersen

where Lo, Ro - inductance and resistance of the coil. When this witness PWM Converter 1 would function as a passive dvukhpolosnykh. However, the application of servo PWM Converter 1 allows you to make two steps forward. First, witness the PWM Converter 1 can be simulated in the power circuit, not only the coil inductance, but the combined circuit composed of inductance and shunt resistor R00

These inductance and resistor are virtual; they are no more than a couple of operators in the microprocessor control system servo PWM Converter 1, but in the power scheme of the act as the inductor and the resistor. In arc suppression devices, described in [14] the damping resistor R00combined scheme Dagahaley remains active and steady when it is no longer needed, and spoils the characteristics of the mode. In witness PWM Converter 1, you can take the next step of improvement, and to remove the effect of virtual damping resistor as it becomes unnecessary. This step in the system is active dugogodisnjem is not only possible, but also necessary. The energy absorbed by the virtual resistor

is transmitted by the Converter 9 voltage in the DC link voltage accumulating capacitor 5). In the proposed scheme Dagahaley the DC link voltage is not connected to any source of comparable power output, but only to the accumulating capacitor 5. To maintain voltage (Ud) capacitor 5 in the vicinity of the nominal voltage (Udz) to the job current iz must be added a third component - the component balance ibal. Balance functions in the direction of the main harmonicsthe neutral voltage vn. The level of impact is determined by the ratio of the conductivity balance Gbal:

,

which in turn is determined by the voltage regulator and energy storage capacitors of the Converter

where F(p) is a conversion function block 24 balance control,

Ez and Ed - nominal (calculated) and measured (calculated) levels of the energy storage capacitor (capacitor) 5, respectively.

Thus the resulting system of referencing current for the active arc suppression device in which the current job is composed of three components (figure 5):

- compensation the ion component, acting orthogonal to the direction of voltage neutral with a coefficient of conductivity compensation Yz

- damping component acting on all components of the neutral voltage with a coefficient of conductivity damping

- balanced component acting in the direction of the main harmonic voltage neutral with a coefficient of conductivity balance Gbal, which is determined by the balance control voltage (energy) capacitor (6, 7).

Job current iz is the sum of (adder 16 figure 5)

The fundamental harmonicand the orthogonal component of vn ortcan be obtained by using a filter of the second order, depicted in figure 5 (blocks 17, 22, 23),

or in any other way.

Active arc suppression device, made on the basis of servo PWM Converter 1 with a three-part unit current DCB (D - damping, With payment, balance) provides damping is not worse than the combined scheme Dagahaley described in [14] (the reactor with a resistor), but it provides full compensation capacitive current in steady-state conditions sumycin who I am.

As noted above, when used in branched networks adjustable arc suppression devices are equipped with automatic settings. Their action is based on the fact that the main components of current or voltage neutral mixes with the test signal that has a frequency different from the line frequency. In response to the test signal are determined by the parameters of the circuit network neutral, and by these parameters is determined by the desired ratio of the conductivity of the grounding device. With this purpose in arc suppression devices plunger reactors or in the magnetically controlled reactors uses a special additional winding and a special unit test generator and signal analyzer response[5, 7, 9, 10]. When applying the proposed device the task of automatic tuning simpler. Witness PWM Converter 1 can infuse in the neutral network test current or test voltage in parallel with performing the main functions without any additives to it. The desired test signal itest mixes with the reference signal current iz of the Converter by means of the adder 39:

,

as shown in figure 10. The controller 7 current and the Converter 9 voltage supply current equal to the task, in the neutral network, i.e. in the part of the eye neutral component appears the test frequency, mixed with the component of the network frequency.

,

Thus, servo PWM Converter 1 simultaneously with the execution of the main function performs the function of a powerful low-frequency amplifier, which in arc suppression devices inductors [5, 7, 9, 10] is a separate additional device. Receiving the test signal in the proposed system does not require any additional equipment at all; signal itest is generated by microprocessor control system servo PWM Converter 1 and is amplified by servo PWM Converter 1 without any hardware additions. Analysis of the response to the test signal is also controlled by microprocessor control system servo PWM Converter 1, again without requiring additional devices in the system Dagahaley. All the necessary variables in the control system servo PWM Converter 1 are already available to perform their main function, and the computational capabilities of modern signal processors make it easy to combine the calculations of the response and processing them to perform basic functions. Implementation tasks for automatically determining the desired ratio of the conductivity of the arc suppression device (blocks 37 and 38, figure 10) can be carried out by any of the known CA is applied algorithms.

Figure 11 shows one possible functional diagrams to determine the desired ratio Yz conductivity, built on the principle of simultaneous filtering. The generator 40 (genθ) produces orthogonal sinusoidal pair of variables cosθ and sinθ, has a frequency of fIdiffers from the network frequency f:

f'≠f,.

The value of the neutral voltage vncalculated by the adder 45 in accordance with the expression (3).

The test signal itest(t) is obtained by using the block 41 multiplication

itest=Itest×cosθ',

where Itest - selected amplitude of the test current. In the system of orthogonal coordinates of the complex amplitude of the test current is equal to

Itest=Id+j·Iq, Iq=0.

The complex amplitude of the response

Vtest=Vd'+j·Vq'

stands out from the neutral voltage vnby the method of synchronous filtering by multiplying vnon reference variables cosθ and sinθ (blocks multiplying 42 and 43) and then low pass filters 46 and 47. Resistive GnIand capacitive YnIthe components of the conductivity is calculated by the block 48 calculate the components of the conduction network of the components of complex amplitudes

A capacitive conductivity on the test frequency f' is then determined by the desired ratio Yz conductivity at the network frequency (block multiplication 44)

All actions by the circuit 11 are microprocessor controlled servo PWM Converter 1; no hardware additions are not required

When the Converter in parallel with fixed arc reactor in the schema view figa or in the schemes of the form Fig, Fig.9 circuit in neutral becomes a chain of second order (figb). Algorithm-locked loop with a test signal of frequency f'≠f under these conditions is insufficient. However, this algorithm can easily be modified. To identify the parameters of more complex circuits in block 36-locked loop (figure 10) should be provided for generating a two-frequency test signal with frequency f', f", which differ from each other and from the network frequency f

f'≠f≠f.

A test signal is produced by generator 40 and the adder 54 in the form:

itest=Id1·cosθ'+Id2·cosθ",

,.

In the functional diagram shown Fig, for processing the response using a double set of blocks multiplication(41, 42, 43, 49, 50, 51) and low-pass filters(46, 47, 52, 53), outputs which are components of the response (test signal) Vd', Vq', Vd", Vq". These values taking into account Iq'=0, Iq=0, in block 48 (calc) computed LnCn, Rnand then define the desired coefficient of Yz PR is Vedemosti neutral for servo PWM Converter 1.

The operation of the inventive controlled semiconductor Converter illustrate graphs of processes in the compensation of the capacitive current and the network identification, mathematical modeling in MathCad (Fig - Fig).

For the purposes of comparative study of active Dagahaley the results of the simulation of the combined system Dagahaley [14], which uses arc suppression coil with inductance Lo and the damping resistor with resistance Roo. Considered a network with a voltage of 6.3 kV capacity of 5.6 MW, in which the steady-state capacitive current to earth is about 100 A. the nominal reactance arc suppression coil is

ωs·Lon=36.75Ω.

Actually set the inductance of the coil Lo may vary significantly from the desired value, the range starts from

(overcompensation) and ends with

(neocomposite). Consider this part of the process provide the basis for subsequent measurement system with active dugogodisnjem. Processes are considered in the simplest equivalent circuit (Fig).

The graphs Arc 02 19 (Fig) shows the process when a large resistance of the shunt resistor.

,

so that only works arcing beach is CA. Inductance arc suppression coil taken with overcompensation

.

The upper diagrams show the voltage coming between vd(·) and the voltage on the ground dvukhpolosnykh v0(·). Displayed as a graph of the critical stress vkrit at which the breakdown occurs span. On average graphs are given arc current id(·) and the current ground dvukhpolosnykh i0(·). The lower diagrams show the phase voltage relative to the earth va(·), vb(·), vc(·).

The graphs show that if high resistance shunt resistor process is completely unsatisfactory. On the interval t=600 MS followed each other recurring breakouts. Overvoltage reach multiplicity, a prominent arc energy reaches Endu=5.2 kJ.

The graphs Arc 02 20 (Fig) shows that the introduction of the shunt resistor with a lower resistance

corrects the process. After five successive breakdown strength of the insulation gap is restored and installed normal network. The maximum strain is reduced to =2.45, and released the energy in the place of breakdown is reduced to 1.9 kJ.

The graphs Arc 02 23 (Fig) shows the same processes as above, but if neocomposite

.

Financial p the tats similar to those described above: when the intermediate value of the conductivity of the shunt resistor after several breakdowns recovers normal operation of the network.

The graphs Arc 02 26 (Fig) shows the processes while fine-tuning compensation

Regenerative voltage while fine-tuning is growing slowly and shunt resistor under these conditions is not conducive to the improvement process. However, the use of shunt resistor is useful because it softens the impact of the inevitable errors settings.

Made above (see Fig, 15, 16, 17) consideration of the combined scheme Dagahaley [14] is an auxiliary. The purpose is to provide the basis for the assessment of the proposed active arc suppression device. Analyzed the circuit in figure 4, in which the generator current 8 made by the scheme of figure 5. The circuit network is the same (Fig)that was used when considering the combined device Dagahaley [14]. Saved as a substitution circuit parameters and the model parameters of the arc.

The graphs Arc 05 01, 02, 03, (Fig, 19, 20) shows the processes active arc suppression device when overcompensationif neocompositeand fine tuning. Resistor Roo in the active arc suppression device is virtual. Its conductivity is assumed to Roo=1.5×ωSLon.

Variables and symbols in the graphs Arc 05 01, 02, 03 are the same as above. Comparison of the graphs of the active control is Ogasawara devices Arc 05 01, 02, 03 (Fig, 19, 20) charts with combined arc suppression device Arc 02 20, 23, 26 (Fig, 16, 17) shows that each of these devices in these circumstances the network after a series of breakdowns restoration of normal network operation. Very close and quantitative indicators processes, as can be seen from the following table:

ValueDetuningCombined schemeActive device
1.252.32.41
12.02.26
0.82.452.32
ε, kJ1.252.192.33
10.621.52
0.81.921.47

Thus, the active arc suppression device in terms of recovering breakdowns equivalent to binyavanga arc suppression device [14], composed of a reactor and a resistor. The difference between the functional characteristics of these devices is manifested in a different class situations, when installed and maintained short circuit to earth. The system of balance of energy storage capacitors in these situations reduces the active component of the current to zero, thus reducing the current in the gap short circuit; while fine-tuning the latter is reduced to zero, as shown in the graphs Arc 05 04, 04 (Fig, 22). Combined same scheme [14] with sustained short circuit pouring the residual current in place of the circuit even when you are fine tuning (graphics Arc 02 28 Fig), which, of course, is its disadvantage. When inaccurate setting of the advantage of the active arc suppression device is somewhat reduced, since the error setting system balance is not compensated. However, some reduction in the current in the gap short circuit still work.

All of the above, apply equally to the alternative arc suppression device on the basis of the servo PWM Converter 1 (figure 4, 7, 10)and other options (Fig, 9), the choice of which is due to feasibility considerations.

On Fig presents a variant of the arc suppression device with fixed orifice 34, performed on half the required reactive power of zazemlyayushchikh (Q N/2) and witness PWM Converter 1 on the same half-power (QN/2). Regulation of the Converter full-scale range of ±QN/2 total admittance regulated in the full range from zero to the nominal value.

Similarly, by price or other some motives (for example, to run the Converter on low voltage) may be helpful to use a matching transformer 35 (Fig.9). This transformer 35 may also be designed as a transformer-reactor, with a capacity of idling is equal to half the required nominal power arc suppression device. The required installed capacity servo PWM Converter 1 also is half of the rated capacity.

So, as a summary of the results can be noted:

- it is proposed to use as an adjustable arc suppression device active element - servo PWM Converter 1, by itself or in combination with fixed orifice 34 or transformer-reactor 35;

- proposed control algorithm to generate a three-component reference signal current tracking PWM Converter 1 (DCB algorithm);

- a preliminary comparative study of the characteristics of the active arc suppression device with a combined arc suppression device RL-type [14] showed that in situations with intermittent p is the Wallpaper of their characteristics are close, and in situations with steady-state short-circuit active device tracking PWM Converter 1 has the advantage of;

- power equipment servo PWM Converter 1 and microprocessor-based control system can be used as equipment for testing the network and automatically configure arc suppression device, thereby eliminating the need for any additional hardware-locked loop.

Thus, when the above-mentioned performance of the inventive device is provided to perform basic functions - compensation capacitive current for single-phase ground fault, as well as additional useful functions: the ability to identify network without the use of auxiliary equipment, fast transient suppression components of the current, including recurring breakdowns, accelerated decrease in the arc current, the exit compensation upon termination circuit.

Based on the above, the task of creating a device of the compensation current earth fault in three-phase electrical networks based on single-phase servo PWM Converter with along with the basic, additional useful features such as the ability to identify the network, fast transient suppression components of the current, accelerated decrease in the arc current, p is and the simultaneous elimination of the aforementioned disadvantages, inherent UPAR [5] solved.

Sources of information:

1. Petersen W. Der aussetzende Erdschluss. ETZ, Bd 38, S.553-555; ETZ, Bd 47, S.564-566; ETZ, Bd48, 1917.

2. Likhachev F.A. ground fault in networks with isolated neutral and with compensation of capacitive currents. M Energy, 1971

3. Chernikov A.A. Compensation capacitive currents in networks with ungrounded.., M Energy, 1974

4. Arc suppression reactors, technical information, www.energan.ru., LLC ENERGY", 2007.

5. Gernot Druml, Olaf Seifert. Arc suppression reactors 6-35 kV. A new method of determining network parameters. News of Electrical engineering, No. 2 (44), 2007.

6. Koenigi R. Arc suppression coils - the key component of modern earth fault protection systems. Papp K. Transmission and Distribution Conference and Exposition: Latin America (T&D-LA), p.366-371, 2010.

7. Arc Suppression Coils. Brochure of the firm Trench. www.trenchgroup.com. TRENCH Group 2012.

8. Managed Pogranichnyi Arc suppression reactors with automatic compensation of the capacitive current earth fault networks 6-35 kV. A.M. Bryantsev, Lurie A.I., Dolgopolov, A.G. and other Electricity No. 7, 2000

9. System control and protection for arc suppression reactors, the magnetically controlled. A.M. Bryantsev, Dolgopolov A.G. Electric station No. 2, 2000

10. RF patent №2130677, H02J 3/26, NN 3/17, publ. 20.05.1999, Authors: A.M. Bryantsev, Dolgopolov A.G.

11. Peters I.F., Slepian I. Voltage Inducted by Arcing Grounds. Tr. AIEE, p.478-489, 1923.

12. theory of surge from the ground arcs in a network with isolated neutral. Joo is Arly CM, Electricity No. 6, p.18-27, 1953

13. The study of surge in arc short circuits to ground in circuits 6 and 10 KV with insulated neutral. Belyakov NM, Electricity No. 5, p.31-36, 1957

14. M. A. Ilyin's Cartographic Establishment, L. Sarine, A. Sinkovec, E Buyanov. Offset and combined grounded neutral. The experience of operating the network 6 kV steel mill. News of Electrical engineering, No. 2 (44), 2007.

15. DE 10103031 B4, 2011.12.01, NM 5/42. Rainer Marquardt. St romrichterschaltung mit verteilten Energiespeichern und Verfahren zur Steuerung einer derartigen Stromrichterschaltung

1. The device compensation current earth fault in three-phase electrical networks containing dvukhpolosnykh connecting the neutral mains transformer with the ground and forming a lagging current to compensate for the rapid capacitive current of single-phase ground fault, and the current sensor neutral, transformer voltage, generator test signals for measuring network capacity and computing unit for determining the required admittance mentioned dvukhpolosnykh, characterized in that as the grounding dvukhpolosnykh applied servo pulse modulated Converter voltage (servo PWM Converter), is provided in addition to the usual set of functional blocks by the block generator current inputs are voltage neutral and required admittance, the output assetstudio current at the input of the current regulator mentioned servo PWM Converter, and the transfer function of the generator current provides a lagging phase shift of about 90 degrees at the network frequency.

2. The device compensation current earth fault in three-phase electrical networks according to claim 1, characterized in that the transfer function of the unit in addition to the reactive (first) component contains a damping proportional to the input signal component, which in the action of the Converter appears as a shunt resistor (virtual resistor).

3. The device compensation current earth fault in three-phase electrical networks according to claim 1, characterized in that the capacitor DC voltage servo PWM Converter (storage capacitors) made a "hung" (not attached to the source or the drain voltage of comparable power output), and the transfer function of the unit introduced an additional component (balance), generated based on the error voltage capacitor servo PWM Converter, and ensure the maintenance of their stresses around the nominal level.

4. The device compensation current earth fault in three-phase electrical networks according to claim 1, characterized in that the grounding dvukhpolosnykh entered unregulated coil p is lovino required reactive power grounding dvukhpolosnykh (Q N/2), connected in parallel to the servo PWM Converter, which is also executed on the same half-power (QN/2); and regulation witness PWM Converter in the full range of QN/2 to +QN/2 (leading by 90 degrees lagging currents up to 90 degrees currents) provides regulation total admittance in the full power range from zero to the rated values of QN.

5. The device compensation current earth fault in three-phase electrical networks according to claim 1, characterized in that the servo PWM Converter is connected through a matching transformer.

6. The device compensation current earth fault in three-phase electrical networks according to claim 1, characterized in that the servo PWM Converter is connected through a matching transformer (transformer-reactor) with a capacity of idling QN/2.

7. The device compensation current earth fault in three-phase electrical networks according to claim 1, characterized in that the servo PWM Converter in parallel with performing the basic functions (compensation capacitive current) injects (injection) in the neutral network test current or test voltage, and the desired admittance is calculated in the control system in response to a test frequency in the neutral voltage.

8. The device compensation current earth fault in Proc. of hasnah electrical networks according to claim 1, characterized in that the transfer function of the unit along with reactive (compensatory), damping and balanced components contains an additional component of the test signal with a frequency (ωtest), non-network (ωs) (for example, ωtest=0,5ωs)generated in the control system servo PWM Converter, and a test signal is the sum of two or more harmonic components of different frequencies, different from the network.

9. The device compensation current earth fault in three-phase electrical networks according to claim 1, characterized in that the control system servo PWM Converter based on a powerful signal processor, combines the functions device-specific compensation current earth fault in three-phase electrical networks, (such as: the generation of test signals, processing the responses to the test signals and the calculation of the required indicators) with non-specific (normal) control functions servo PWM Converter, thereby eliminating the need to use additional equipment.



 

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