Method for quickly and automatically switching on backup power supply for consumers

Abstract

FIELD: electrical engineering.SUBSTANCE: invention relates to devices for network automation of substations. According to the method, emergency components of the sections of the main and backup power sources are isolated from the measured currents and voltages. Based on the results of simulation modelling and calculations, the real part of the functional dependence of the current ratio coefficient on the possible location of damage in the section of the electrical network is determined, as well as the complex coefficients involved in the calculations of the current ratio coefficient. The values of the real part of the functional dependence of the current ratio and complex coefficients are stored in the memory blocks. The current ratio coefficient is calculated. If the value of the real part of the current ratio coefficient falls in the vicinity of the transition point of the functional dependence of the current ratio through the zero value, as well as in the case of zero current values, the action of fast automatic input of the reserve is not provided. If the value of the real part of the current ratio coefficient falls into the positive part of the functional dependence of the current ratio, then consumers are disconnected from the bus section of the main power source and connected to the bus section of the backup power source. If the value of the real part of the current ratio coefficient falls into the negative part of the functional dependence of the current ratio, then the consumers are disconnected from the bus section of the backup power source and connected to the bus section of the main power source.EFFECT: increasing the speed of the method for automatically switching on backup power supply for consumers.1 cl, 4 dwg

Description

[0001] The invention relates to electrical engineering, in particular to devices for network automation of substations.

[0002] A method for automatically switching on a reserve is known [Russian Federation Patent for Invention No. 2725423, IPC H02J 9 / 06, published 02.07.2020 Bulletin No. 19]. According to the method of automatically switching on a reserve, the voltage U is measured Ш on consumer buses and current I ВП on the power input switch (PIS), connected via the PIS to the working power source. The position of the PIS is continuously monitored using the first and second position relays. The angle ϕ between the voltage U and the load, which characterizes the loss of power to consumers, is determined. Ш and current I ВП . Compare the voltage U Ш , current I ВП and angle ϕ with specified values, and if they exceed them, a signal is sent to disconnect the power transmission line. Then the first sectional switch (SS) is turned on, the current I1 in its phases is measured, and the resistance is determined by the ratio Z1 = U Ш / I1. Compare the current I1 with the given value of current I Э and resistance Z2 with the value of resistance Z Э , and if the value of current I2 is greater than or equal to the specified value of current I Э , or Z2 is less than or equal to Z Э , then after a time delay t1 a signal is sent to turn off the first SV. If the current I2 is less than the set current I Э , and Z2 is greater than Z Э , then the time delay is switched to t2 greater than t1. If, after a time greater than t2 after the first CB switch is closed, it turns out that the current value I1 is greater than or equal to the set current value I Э or Z1 is less than or equal to Z Э , then after time t2 after the moment of increase of current I1 in the phases of the first CB to I Э or decreasing Z1 to Z ЭA signal is sent to turn off the first PV. Additionally, the second PV is placed on hot standby. If, after the signals to turn off the PV, it is turned off and there is a signal from the first or second PV position relay and the first PV has not turned on, the second PV is turned on. Next, immediately after the second PV is turned on, the current I2 in its phases is measured and the resistance is determined using the ratio Z2 = U Ш / I2. Compare the current I2 with the given value of current I Э and the ratio Z2 with the resistance value Z Э , and if the value of current I2 is greater than or equal to the specified value of current I Э , or Z2 is less than or equal to Z Э , then after a time delay t1 a signal is sent to turn off the second SV. If the current I2 is less than the set current I Э , and Z2 is greater than Z Э , then switch the time delay to t2. Further, if after turning on the second SV it turns out that the current value I2 is greater than or equal to the set current value I Э , or Z2 is less than or equal to Z Э, then after time t2 after the moment of increase of current I2 in the phases of the second CB to I Э or decreasing Z2 to Z Э send a signal to turn off the second SV.

[0003] The disadvantage of the known method of automatic switching on of the reserve is low performance.

[0004] A known method for automatically switching on a backup power supply for consumers [RU Patent for Invention No. 2447565, IPC H02J 9 / 06, published 10.04.2012 Bulletin No. 10], which involves measuring the positive sequence voltage of the buses of the main and backup power sources, measuring the angle between the positive sequence voltage vectors of the buses of the main and backup power sources, determining the direction of the active power at the input of the buses of the main power source, determining the minimum input current of each section, switching the buses of the main power source to the backup one when the positive sequence voltage of the buses of the main power source decreases below a specified level or when the angle between the positive sequence voltage vector increases greater than a specified value and when the active power is directed from the buses to the main power source and when a specified current is exceeded.

[0005] According to the proposal, the direction of the powers in the phases at the input of the main and backup sources is determined on the basis of the phase currents and opposite line voltages, taking into account the angle of maximum sensitivity, while if the values ​​of the line voltages on the buses of the main source are less than the specified voltage value, then the corresponding voltages of the backup source are taken as the vectors of these voltages, the values ​​of the phase currents at the input are compared with the specified current value, and if the values ​​of the phase currents at the input of the main source are less than the specified current value, and the values ​​of the phase currents at the backup input are greater than the specified current value, or if the powers at the input from the main source change sign to negative in at least one phase, and the powers at the input from the backup source are positive in all phases, then the power is switched to the backup source.

[0006] The disadvantage of the known method of automatically switching on the backup power supply of consumers is the low speed of operation.

[0007] The closest technical solution is a method for automatically switching on the backup power supply of consumers [RU Patent for Invention No. 2326481, IPC H02J 9 / 06, published 10.06.2008 Bulletin No. 16], which involves measuring the positive sequence voltage of the buses of the main and backup power sources, measuring the angle between the positive sequence voltage vectors of the buses of the main and backup power sources, determining the direction of the active power at the input of the buses of the main power source, switching the buses of the main power source to the backup one when the positive sequence voltage of the buses of the main power source decreases below a specified level or when the angle between the positive sequence voltage vector increases greater than a specified value and when the active power is directed from the buses to the main power source.

[0008] According to the proposal, the minimum input current of each section is additionally measured, compared with the set input current value, and if the set current is exceeded, a switch to the backup power source is also performed.

[0009] The disadvantage of the prototype method is its low performance.

[0010] Fast automatic power transfer system (FAPS) is required for industrial applications with continuous operation, where power supply interruptions are not permitted. In such cases, the response time for the FAPS device is approximately one period of the main power frequency. Therefore, in terms of the required speed of emergency recognition, the FAPS automation system must outperform relay protection. Therefore, it is advisable to use unified mode recognition algorithms developed for relay protection in FAPS automation.

[0011] Let us consider a classic BAVR automation system, which includes three active modules A1, A2, A3 (Fig. 1), in which the state of module A3, which is connected to the other two, is subject to monitoring. Observation of all processes in the system (Fig. 1) is considered in terms of complex quantities. , And , , Where , And , - respectively, the currents and voltages supplied to the inputs of modules A1 and A2. It is assumed that the values ​​of the previous mode , (Fig. 1.a) have extrapolation , for the time after the short circuit that occurred in module A3 (Fig. 1.b), in connection with which the current short circuit mode can be represented as a superposition of the previous real mode and an artificial purely emergency mode, in which emergency components of currents and voltages operate (Fig. 1.c)

[0012]

[0013] The presence of sources in module A3 is emphasized by the indication of EMF (Fig. 1.a, b, c), and damage to this module is indicated by the appearance of current at the location of the short circuit (Fig. 1.b, c). Values And unknown, as is the location of the short circuit itself.

[0014] Dependent on the observed EMF modes And introduced into the structure of the electrical network in accordance with the compensation principle. The state of module A3 in the circuit of Fig. 1.c remains the same as in the original structure of Fig. 1.b. The difference is that modules A1 and A2 can be excluded from consideration, starting with the circuit of Fig. 1.c. In accordance with the principle of superposition, it is possible to exclude the source from consideration module A3 and move on to the purely emergency mode circuit (Fig. 1.g), in which the now passive module P3 is under the influence of external sources And . Further application of the superposition method leads to the division of the purely emergency mode into the normal mode created in the undamaged module P3 by emergency components of voltages (Fig. 1.d), and a local mode created in module P3, the terminals of which are shunted by an unknown short-circuit current (Fig. 1.e). The local mode plays a central role in short-circuit recognition because it is here that the information about the damage to the object is concentrated. Normal components ( ) and the corresponding normal mode allow local components to be identified

[0015]

[0016] but at the same time they themselves have no direct connection with the damage.

[0017] The system (Fig. 1.a) can be represented as a real section of the electrical network corresponding to Fig. 2.a, in which there are loads H1 and H2, fed from different transformers T1 and T1, which receive energy from one EMF source with internal resistance along power transmission lines L1 and L2 with lengths l1 and l2 and specific resistances And . Currents and voltages of loads H1 and H2 are observed in the previous and current modes. , ; , ; , ; , ; according to them, the differences (1) are determined as emergency components , ; , The task of the BAVR is to recognize short circuits in the first and second supply circuits (at points f т1 and f л1 or f л2 and f т2 ), and separately at points f ш1 and f ш2 behind the place of observation of currents on load buses H1 or H2 (“behind the back”).

[0018] In the section of the electrical network under consideration, the normal mode model is a connection of its passive elements leading from the first busbar system to the second (Fig. 2.b); here And - transformer resistance, , - line resistance. This model is defined by three coefficients , , Conductivities express normal currents through the voltages applied to the model

[0019]

[0020] where

[0021] In addition to operations (3), (4), operation (2) of determining local currents is performed And , as well as the operation of forming from them the current ratio coefficient

[0022]

[0023] and comparing it with the a priori function that establishes the dependence of the current ratio coefficient (5) on the location of the short circuit in the power supply network.

[0024] These operations are designed to solve the primary functional objective of the proposed BAVR method, which is to determine in which of the two supply circuits a short circuit has occurred. A notable feature of the BAVR method is that its use of local currents eliminates the influence of load parameters H1 and H2, which are variable and tend to switch from motor mode to generator mode during a short circuit in the electrical network. The fact that it ignores loads when determining the a priori function of the current ratio coefficient from the location of a potential short circuit allows the proposed BAVR method to be classified as a unified method.

[0025] The coordinate function of the current ratio coefficient is determined using the local mode model (Fig. 2.c) and is intended to establish an a priori relationship between the ratio (5) and the short-circuit location, which is unified in nature, since it does not depend on the magnitude of the short-circuit transition resistance, on its type, and is the same for each of the three phases. The coordinate of the suspected short-circuit location (Fig. 2.a) is defined as the transition from the first busbar system s to the second r. The value of the inductive resistance X is taken as the coordinate f elements of the circuit from point s to an arbitrary location of the expected short circuit, related to the total longitudinal inductive resistance of the entire circuit

[0026]

[0027] where X т1 , X т2 - inductive reactance of transformers, and X л1 , X л1 - lines.

[0028] The left and right parts of the model (Fig. 2.c) are each equivalent relative to the location f of the supposed short circuit with coordinate X f passive blocks And Currents And in shunted inputs are expressed through the same unknown voltage . Thus, in the circuit of Fig. 2.g, with a short circuit in the first line at the location local currents will arise

[0029]

[0030] where

[0031] Substituting (8) and (9) into relation (5) will determine the desired function of the current ratio coefficient during a short circuit in line L1

[0032]

[0033] where - the coordinate of the fault location on line L1. The coordinate function of other circuit elements is determined in a similar manner. For example, in the case of a short circuit in the second line, expressions similar to (7), (8) are swapped.

[0034]

[0035]

[0036] Hence the function of the coefficient of the ratio of currents during short circuit in line L2

[0037]

[0038] As an example, we consider a real 110 kV network with identical lines L1 and L2 with a length of l = 41.635 km, wire grade AC-120 / 19 and transformers T1 and T2 110 / 10 kV, with a capacity of 10 MVA each and short-circuit losses of 53.8 kW. The power source resistance is assumed to be .

[0039] The function of the current ratio coefficient as a dependence of its real part on the coordinate of the short-circuit location is determined for a network section using formulas (7) - (12) and the final ratio (5), the result of which is shown in Fig. 3 (solid curve). In this case, the regularity of the current ratio coefficient during a short circuit in the first and second circuits is clearly evident, the values ​​​​of which differ in signs, changing within the range from +1 during a short circuit at the terminals of the low-voltage winding of transformer T1 to (-1) during a short circuit at similar terminals of transformer T2, and during a short circuit at a point b common to both circuits takes a zero value (Fig. 2.a). The sharp transition from positive to negative values ​​​​of the current ratio coefficient when observing the system on the load buses (Fig. 2.a) is explained primarily by the influence of the internal resistance in the local mode model (Fig. 2.c).

[0040] To investigate the capabilities of the BAVR method, a simulation model of an electrical network section corresponding to Fig. 2.a was used, with the same passive parameters for which the a priori characteristic was previously determined, in which short circuits at various points of the electrical network section were simulated. The network load consisted of electric motors: H1 - synchronous, H2 - asynchronous, two electric motors with a capacity of 2.3 MVA on each load busbar system.

[0041] In the digital processing of observed processes, it is advisable to use orthogonal component filters that transform a sample of the observed value into a complex number. Adaptive orthogonal component filters have the highest response speed, measured by the duration of the observation window [e.g., Ivanov S.V., Lyamets Yu.Ya., Makashkin F.A. Estimation of the parameters of elementary components of an electrical quantity from a small number of samples. Electrical Engineering, 2020. No. 3. pp. 59-67]. However, satisfactory results are also provided by non-adaptive filters, including the full-wave Fourier filter, which is most widely used in the software of relay protection and automation terminals [e.g., Shneerson E.M. Digital Relay Protection. Energoatomizdat, 2007].According to a formal indicator such as settling time, it is not considered a high-speed filter. However, the current ratio coefficient (5), for which the ratio of local current complexes is important, rather than each individual current, is relatively insensitive to the process of settling identical filters at different observation locations. In Fig. 3, the dotted line shows the current ratio coefficient function obtained from simulation modeling over an 8-ms electrical quantity observation interval. It differs somewhat from the a priori characteristic obtained in the sinusoidal local mode model (Fig. 2.c). With an extension of the input signal processing interval to 20 ms, both characteristics coincide.

[0042] The objective of the invention is to increase the speed of the method for automatically switching on the backup power supply of consumers.

[0043] The stated task is achieved by a method of rapid automatic switching on of the backup power supply of consumers (BAVR), in which the voltage and current of the bus sections of the main and backup power sources are measured, the calculated currents are determined, the value depending on the input current of each section is compared with the specified value and, based on the results of the comparison, the consumers are switched to the backup power source.

[0044] According to the proposal, emergency components of the main sections are isolated from the measured currents and voltages , and backup , Based on the results of preliminary simulation modeling and calculations, the real part of the functional dependence of the current ratio coefficient on the potential fault location in the electrical network section, as well as the complex coefficients involved in calculating the current ratio coefficient, are determined for power sources. The values ​​of the real part of the functional dependence of the current ratio and the complex coefficients are stored in memory blocks, and the current ratio coefficient (5) is calculated based on the corresponding local currents.

[0045]

[0046] The complex coefficients a, c, d are determined by the relations:

[0047]

[0048] where , - transformer resistance, , - resistance of lines respectively connected to the bus sections of the main and backup power sources; - internal resistance of the power source.

[0049] In the comparison block, a decision is made regarding the BAVR, if the value of the real part of the current ratio coefficient falls in the vicinity of the transition point of the functional dependence of the current ratio through the zero value, and also in the case of zero current values =0, =0, then the BAVR is not intended to operate. If the value of the real part of the current ratio coefficient falls within the positive part of the current ratio functional dependence, then consumers are disconnected from the main power supply bus section and connected to the backup power supply bus section, and a control signal is generated from the first output of the comparison unit. If the value of the real part of the current ratio coefficient falls within the negative part of the current ratio functional dependence, then consumers are disconnected from the backup power supply bus section and connected to the main power supply bus section, and a control signal is generated from the second output of the comparison unit.

[0050] Fig. 1 characterizes the electrical system, including three active modules, and its operating modes: a - previous; b, c - current short-circuit mode; g - purely emergency; d - normal, e - local.

[0051] Fig. 2 shows models of a section of an electrical network with two redundant loads: a - simulation model; b - normal mode model; c - expanded model of the local mode, d - equivalent relative to the location of the short circuit.

[0052] Fig. 3 shows the dependence of the real part of the current ratio coefficient on the coordinate of the expected location of the short circuit: 1 - a priori, 2 - simulation.

[0053] Fig. 4 shows a structural diagram of a device that implements the proposed method for quickly automatically switching on backup power supply for consumers.

[0054] The device (Fig. 4) includes: a block for generating emergency mode components 1; a block for calculating local currents 2; a block for calculating the current ratio coefficient 3; a comparison block 4; a block for storing coefficients 5; a block for storing simulation results 6.

[0055] The device implementing the method of quickly automatically switching on the backup power supply of consumers (Fig. 4) operates as follows.

[0056] Before the device starts to function (Fig. 4), the coefficients a, c, d are calculated using expressions (15) - (17) using the parameters of the electrical network section: And - transformer resistances; , - line resistance; power supply resistance The results of the calculations of the coefficients a, c, d are entered into the coefficient memory block 5 of the device (Fig. 4).

[0057] Additionally, before the start of operation of the device (Fig. 4), a simulation modeling of the section of the electrical network is carried out (Fig. 2.a) in order to obtain the functional dependence of the real part of the current ratio coefficient Re , characterizing damage in different parts of the electrical network section (Fig. 2.a), supplying loads H1 and H2. The results of the simulation modeling in the form of values ​​of the functional dependence (Fig. 3) of the real part of the current ratio coefficient Re the results of the simulation modeling are entered into the memory block 6 (Fig. 4).

[0058] During the operation of the device (Fig. 4), discrete values ​​of currents i1(n), i2(n) and voltages u1(n), u2(n) of the bus sections of the main and backup power supplies are received at the inputs of block 1. Discrete values ​​of currents i1(n), i2(n) and voltages u1(n), u2(n) of the bus sections of the main and backup power supplies can also be received, for example, from digital current and voltage transformers in accordance with the IEC 61850 - 9.2 SV protocol. In block 1, emergency components are generated , , , in accordance with expression (1).

[0059] Complex values ​​from block 1 output , , , are fed to the inputs of block 2 for calculating local currents. Also, the coefficients a, c, d are fed to the inputs of block 2 from the outputs of block 5 for the coefficient memory to perform calculations of local currents according to expressions (13) and (14).

[0060] After implementing the computational procedures in block 2, the complex values ​​of local currents And are fed to the inputs of block 3 to calculate the current ratio coefficient according to expression (5). The value of the real part of the current ratio coefficient Re from the output of block 3 goes to the input of comparison block 4. The values ​​of the functional dependence (Fig. 3) of the real part of the current ratio coefficient Re are sent to the other input of comparison block 4 from the output of block 6 of the memory of the results of simulation modeling , characterizing damage in different parts of the electrical network section (Fig. 2.a).

[0061] In comparison block 4, a decision is made regarding the actions of the BAVR. If the value of the real part of the current ratio coefficient Re falls into the vicinity of point b - the transition of the characteristic through the zero value (Fig. 3), then this indicates a short circuit in the source (Fig. 2.a). In this mode, the BAVR is not provided for to operate.

[0062] Also, the action of the BAVR is not provided when the value of the real part of the current ratio coefficient Re corresponds to the short-circuit mode on the load buses (points f ш in Fig. 2.a), and the location of the short circuit is outside the observed part of the system. Since the observed part of the system is not damaged, its model in normal mode (Fig. 2.b) does not differ from the model of the original purely emergency mode, and in the model of the local mode (Fig. 2.c). As a consequence, And i.e. in such a mode, which does not involve the action of the BAVR, zero levels of local currents are characteristic with a high level of emergency components of currents and voltages.

[0063] If the value of the real part of the current ratio coefficient Re falls into the positive part of the characteristic (Fig. 3) above the vicinity of point b, then this indicates a short circuit in the first supply circuit, in which case the load H1 is switched - disconnected from the first circuit and connected to the load H2 buses. In this case, a control signal is issued from the first output of the comparison block 4 of the device (Fig. 4).

[0064] If the value of the real part of the current ratio coefficient Re falls into the negative part of the characteristic (Fig. 3) below the vicinity of point b, this indicates a short circuit in the second supply circuit, and the load H2 is switched - disconnected from the second circuit and connected to the load H1 buses. In this case, a control signal is issued from the second output of the comparison unit 4 of the device (Fig. 4).

[0065] It was previously noted that the current ratio coefficient (5), for which the ratio of local current complexes is important, is insensitive to the process of establishing currents measured at different points within a section of the electrical network. This is confirmed by the calculation of the current ratio coefficient function (Fig. 3, dotted line) obtained from simulation modeling over an 8-ms electrical value observation interval. Clearly, the accuracy of this coefficient's calculation over this interval is high and fully meets the requirements for reliable implementation of the proposed method for quickly and automatically switching on backup power to consumers.

[0066] Thus, the proposed method makes it possible to achieve the objective of the invention, which consists in increasing the speed of the method for automatically switching on the backup power supply of consumers.

Claims

A method for quickly automatically switching on the backup power supply of consumers (BAVR), in which the voltage and current of the bus sections of the main and backup power sources are measured, the value depending on the input current of each section is compared with a specified value and, based on the results of the comparison, the consumers are switched to the backup power source, characterized in that the emergency components of the main sections are isolated from the measured currents and voltages and backup power sources, based on the results of preliminary simulation modeling and calculations, determine the real part of the functional dependence of the current ratio coefficient on the possible location of damage in the section of the electrical network, as well as the complex coefficients involved in the calculations of the current ratio coefficient, store in memory blocks the values ​​of the real part of the functional dependence of the current ratio and the complex coefficients, and calculate the current ratio coefficient using the expression Where - local currents; - complex coefficients; - transformer resistance; - resistance of lines respectively connected to the bus sections of the main and backup power sources; - internal resistance of the power source, in the comparison block, a decision is made regarding the BAVR, and if the value of the real part of the current ratio coefficient falls in the vicinity of the transition point of the functional dependence of the current ratio through the zero value, and also in the case of zero current values the action of the BAVR is not provided; if the value of the real part of the current ratio coefficient falls into the positive part of the functional dependence of the current ratio, then the consumers are disconnected from the bus section of the main power source and connected to the bus section of the backup power source, while a control signal is issued from the first output of the comparison block; If the value of the real part of the current ratio coefficient falls into the negative part of the functional dependence of the current ratio, then the consumers are disconnected from the bus section of the backup power source and connected to the bus section of the main power source, while a control signal is issued from the second output of the comparison block.

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