RU131198U1 - DEVICE FOR CONTROL OF ELECTRIC POWER SUPPLY LOSSES IN TRANSFORMERS - Google Patents

Abstract

1. A control device for additional losses of electricity in transformers, containing the control object - a transformer, characterized in that it contains an ambient temperature sensor, a current sensor connected to the control object, connected to an analog-to-digital converter unit, which, in turn, is connected directly with the unit for calculating and analyzing the main indicators, with the unit for calculating the integral indicators and with the unit for calculating the K-factor of the network, connected to the unit for calculating the temperature correction, while at the unit for calculating integral indicators, a database unit is connected, and a database unit is connected to the input of the unit for calculating the temperature correction, connected to the input of the unit for calculating and analyzing basic indicators, connected to the graphical interpretation and signaling unit, to the control unit, to the knowledge unit connected to data block. 2. The device according to claim 1, characterized in that the device is additionally equipped with a temperature sensor mounted on a transformer connected to an analog-to-digital converter unit.

Description

The utility model relates to the field of electrical machines, namely to means for monitoring the operational state of transformers, and can be used for bench assessment of the susceptibility of a transformer to thermal dissipation of the energy of higher harmonic currents, continuous monitoring of the temperature of the most heated point of the transformer and predicting its maximum load, as a unit correcting the operation of the cooling system of the transformer, the information block signaling or deciding on the need unloading of the transformer or shutdown of the transformer as a result of critical overload, at currents lower than the protection settings, the information block registering changes in the susceptibility of the transformer to high harmonics during the life cycle and predicting developing defects based on information trends, the information block registering the susceptibility of a serial transformer identifying the park transformers with similar parameters (the same plant, design, power, etc.), to set frequencies (vulnerability) and forming correction temperature coefficients for this series of transformers, information block for controlling higher harmonics filters.

An increase in the proportion of non-linear load and, as a result, an increase in the non-sinusoidality of the mains voltage, makes it necessary to take into account the influence of higher harmonics on power facilities. The most common node in electrical networks is a power transformer. Analyzing the physics of processes that ensure the conversion of voltage from one system to another, it is urgent to take into account the effects caused by high-frequency currents. With an increase in the proportion of higher harmonics in the fundamental frequency curve, processes are associated with additional thermal dissipation of energy: an increase in active resistance due to the skin and proximity effect, an increase in losses caused by eddy currents in the magnetic circuit, in structural units penetrated by the displaced magnetic flux, due to manifestations of magnetic viscosity. Known approaches to the construction of such devices based on the thermal model of the transformer described in GOST 14209-97 (85) and IEC 60076-7 (1. Lykov A.A. Improving the efficiency of power supply systems based on improving models of power transformers and cables: abstract of dissertation of the candidate of technical sciences / KubGTU. - Krasnodar .: KubGTU, 2007. - 24 pp .; 2. Komkov E.Yu. Development of a design and diagnostic complex for optimizing the life cycle of power transformers with forced cooling: abstract Candidate of Technical Sciences / ISEU - Ivanovo: IGEU, 2008. - 24 pp .; 3. Valuyskikh AO Modeling of the thermal regime of a transformer in monitoring and diagnostic control systems / Dulkin I.N., Filatov A.A., Tsfasman G.M. // "Electro", 2008, No. 1; 4. Slatinova MN The rationale for the rational operating parameters of power transformers of power supply systems to improve the reliability and quality of their functioning: dissertation of the candidate of technical sciences /. - Tula, 2010. - 137 p.)

The main controlled parameter is the temperature of the most heated point of the transformer, calculated either continuously or iteratively, with a certain interval.

The block diagram of the known device contains functionally similar blocks, namely, a transformer load unit, a unit for calculating the coil heating time constant, an oil temperature measuring unit, a transformer cooling automation control unit, a unit for calculating changes in winding resistance versus temperature, a comparison and signaling unit, and a coil temperature calculation unit (Lykov A.A. Improving the efficiency of power supply systems based on improving models of power transformers and cables: abstract of diss. . Those sciences / KubGTU -.. .: KubGTU Krasnodar, 2007 - 24)..

A device for controlling a transformer cooling system is known, comprising a key unit for thermal calculation of a transformer. The thermal model of the transformer is represented by differential equations of the dynamics of thermal processes containing coefficients characterizing the weight and size parameters of the transformer and heat transfer processes (Komkov E.Yu. Development of a design and diagnostic complex for optimizing the life cycle of power transformers with forced cooling: abstract of dissertation of the candidate of technical sciences / IGEU. - Ivanovo: IGEU, 2008. - 24 p.).

A common drawback of the known devices presented above is that in their structures there is no block for calculating the K-factor of the network (or another indicator of the quality of EE), a block for calculating the temperature correction, which takes into account the effect of additional heating from additional losses.

A device is proposed for use in diagnostic and monitoring systems, containing a unit for calculating the temperature of a transformer (Valuyskih A.O. Modeling the thermal conditions of a transformer in control systems for monitoring and diagnostics / Dulkin I.N., Filatov A.A., Tsfasman G.M. . // "Electro", 2008, No. 1).

In addition to the thermal change in the resistance of the winding, the known device additionally takes into account additional losses in the windings due to eddy currents, which makes it somewhat more adequate. Nevertheless, it is not envisaged to provide continuous monitoring of the sinusoidality and to adjust the coefficient of additional losses, as proposed in this device.

The closest in technical essence and adopted for the prototype is a device containing a unit for calculating the temperature of the transformer (Slatinova M.N. Justification of rational operating parameters of power transformers of power supply systems to improve the reliability and quality of their functioning: dissertation of the candidate of technical sciences /. - Tula , 2010 .-- 137 s.). A feature of this device is that the thermal model of the transformer takes into account additional heating due to additional losses caused by the higher harmonic composition of the mains current, the eddy current losses in the windings and other structural elements of the transformer are estimated.

The disadvantage of the above thermal model is that it does not take into account all processes associated with the action of higher harmonics, which also need to include microcurrents in the magnetic circuit, which are directly losses, and also cause the effect of magnetic viscosity, which affects the loss of short circuit, change in resistance due to surface effect and proximity effect, etc. Note that these effects have hardly formalizable relationships with both idle losses and short circuit losses. ia, the ratio of which is introduced into the thermal model of the transformer of the known device by a separate coefficient.

The task to which the claimed utility model is directed is the development of a control device that ensures the prevention of possible accidents.

When implementing a utility model, the task is solved by achieving a technical result, which is to limit unacceptable overloads, extend the life of transformers that are not equipped with protection for the temperature of the cooling medium, reduce repair costs and save energy.

The specified technical result is achieved by the fact that in the device for monitoring additional losses of electricity in transformers containing the control object - the transformer, the new is that it contains an ambient temperature sensor, a current sensor connected to the control object, connected to an analog-to-digital converter unit, which, in turn, is connected directly to the unit for calculating and analyzing key indicators, to the unit for calculating integral indicators and to the unit for calculating the K-factor of the network, connected to the unit calculation of the temperature correction, while the database unit is connected to the input of the calculation unit of integral indicators, and the database unit is connected to the input of the calculation block of temperature correction, connected to the input of the calculation and analysis of basic indicators, connected to the graphical interpretation and signaling unit, to the control unit to the knowledge block connected to the data block. In addition, the device is additionally equipped with a temperature sensor mounted on a transformer connected to an analog-to-digital converter unit.

New in the proposed device is the presence of a block of continuous monitoring of the K-factor of the network (or another indicator of the quality of EE), which characterizes the harmonic contribution to the network current, a block for calculating the temperature correction, which selects the coefficient of additional losses introduced into the thermal model of the transformer, as well as a knowledge base unit, accumulating experience and adjusting the correction factor and parameters of the thermal model of the transformer based on temperature measurements of the transformer. The accumulated knowledge, which corresponds to the values of the K-factor of the network (or another indicator of the quality of EE), the values of the temperature correction, can be used to control serial transformers having similar parameters (for example, the same: power, performance, manufacturer, etc. )

The dependences of the correction coefficient on the K-factor of the network (or another EE indicator) can be obtained in other ways, for example, you can establish the relationship between the transformer temperature measured by the thermal imager and retrospective data on the change in the K-factor of the network (or another indicator of EE quality). Dependence in this case can be obtained by analyzing a sufficient amount of accumulated information.

The device, controlling the harmonic composition of the mains voltage, estimates the additional losses by which it calculates the expected temperature and prevents overheating, which causes accelerated aging of the insulation, and as a result, increased maintenance costs, possible emergency failure of the transformer. As a result of the assessment of additional losses, the device can signal thermal overload, limit the main electrical load, and send a trip signal. By analyzing the harmonic composition of the mains voltage, the device generates a signal that can be used to control the filter, if used in conjunction with the device. The coordinated operation of the device and the filter, if used together, increases the quality of the mains voltage, reduces the loss of electricity in electrical installations.

In FIG. A schematic diagram of the device is presented.

The device for monitoring the transformer object contains an ambient temperature sensor (DTV) 1, a transformer temperature sensor (DTT) 2, a current sensor (DT) 3 connected to an analog-to-digital converter unit (BACP) 4, which in turn is connected directly to block calculation and analysis of key indicators (BRAOP) 5, block 4 is connected in series with block 5 through the block calculation of integral indicators (BRIP) 6, block 4 is connected to block 5 in series through the block calculation of K-factor network (BRKFS) 7 and the temperature calculation block popr avki (BRTP) 8. To the input of block 6, in addition to block 4, a database block (DB) is connected 9. To the input of block 8, in addition to block 7, a database block (DB) 9 is connected, block 9 is connected in series to the input of block 5 Block 5 is connected in series to the graphical interpretation and signaling unit (BGIS) 10, is also connected in series to the control unit (BU) 11, to the knowledge unit (KB) 12. Block 12 is connected in series to block 9.

The DT 3, DTT 2, DTV 1 sensors are devices that convert the measured values into an electric signal for subsequent transmission to BACP 4, namely the DTV 1 thermoelectric sensor - ambient temperature, the DTT 2 thermoelectric sensor - transformer temperature, the DT 3 induction sensor - instantaneous current values.

The BACP 4 unit is an analog-to-digital converter.

The BRIP 6 block is a controller that organizes a mathematical module for calculating the equivalent value of the load coefficient, the effective value of the load currents, and average temperatures.

Block BRKFS 7 is a controller that organizes a mathematical module for calculating the K-factor of the network (or other indicator of the quality of energy efficiency).

The BRTP block 8 is a controller that organizes a mathematical module for calculating the correction temperature coefficient based on the calculated value of the K-factor of the network (or another indicator of the quality of EE).

Block DB 9 is a digital information storage device that organizes a database containing the necessary parameters of the transformer and the necessary ratios for the analysis of its operating mode.

The BRAOP 5 block is a controller organizing a mathematical module for calculating temperatures, maximum permissible values of the transformer load factor.

Block BZ 12 is a controller that organizes a mathematical module that refines the parameters of the thermal model of the transformer, calculates the relationships between the K-factor of the network and the temperature correction, as well as overwrites them in the database unit 9.

Block BGIS 10 is a controller that generates, in the case of connecting to it an alarm board or monitor, a signal that interprets the values of the monitored parameters.

Block BU 11 is a controller that generates control signals for the load, superchargers of the cooling system, filters of higher harmonics.

The blocks of the device are interconnected by information transfer buses (shown in Fig.).

Block BRKFS 7 is a controller that performs the calculation of the K-factor of the mains voltage according to the formula (1).

(1)

(one)

where m is the number of harmonics monitored by the device in the network, h is the serial number of harmonics, i _h is the root mean square value of the harmonic current with number h.

The device operates as follows.

(°C) и блоком БРКФС 7, производящим расчет К-фактора сети (о.е.), необходимого для расчета блоком БРТП 8 поправочного температурного коэффициента Ψ (о.е.). С блоков БРИП 6, БРТП 8, БАЦП 4, БД 9 среднее значение температуры охлаждающей среды

(°C), коэффициент нагрузки К (о.е.) (БРИП 6), отношение потерь короткого замыкания к потерям холостого хода трансформатора d (о.е.), номинальное значение превышение температуры масла в верхних слоях над температурой окружающей среды

(°C), номинальное значение превышения температуры наиболее нагретой точки обмотки над температурой масла в верхних слоях

(°C), постоянная времени масла τ_м (мин.), постоянная времени обмотки τ_об (мин.), показатель степени обмотки y (о.е.), показатель степени масла x (о.е.) (БД 9), поправочный коэффициент Ψ (о.е.) (БРКФС 7) поступают на блок БРАОП 5, производящий непрерывный расчет температуры наиболее нагретой точки обмотки и сравнение ее с предельным значением, а также экстраполирующий предельный график нагрузки трансформатора.Continuous signals taken from the sensors are digitized by the BACP 4 analog-to-digital converter unit. Arrays of instantaneous values are processed by the BRIP 6 unit, which calculates the integral parameters for the thermal model of the transformer contained in the BRAOP 5 unit, namely, the load coefficient K (p.u. ), the average value of the temperature of the cooling medium

(° C) and the BRKFS 7 unit, which calculates the K-factor of the network (pu), which is necessary for the BRTP 8 to calculate the correction temperature coefficient Ψ (pu). With BRIP 6, BRTP 8, BACP 4, BD 9 blocks, the average value of the temperature of the cooling medium

(° C), load factor K (pu) (BRIP 6), ratio of short circuit losses to transformer idle losses d (pu), nominal value, excess of oil temperature in the upper layers over ambient temperature

(° C), the nominal value of the temperature rise of the most heated winding point over the temperature of the oil in the upper layers

(° C), oil time constant τ _m (min.), Winding time constant τ _r (min.), Indicator of the degree of winding y (p.u.), indicator of the degree of oil x (p.u.) (DB 9) , correction factor Ψ (pu) (BRKFS 7) is supplied to the BRAOP 5 unit, which continuously calculates the temperature of the warmest point of the winding and compares it with the limit value, as well as extrapolates the load curve of the transformer.

The calculation of the temperature of the most heated point of the transformer (NNT) is presented below.

From the BRAOP block 5, information about the current values of the indicators is transmitted to the BGIS 10 block, which generates a signal, in case of connecting an alarm board or monitor to the device, interprets the values of the monitored parameters, and a control unit (BU 11) generates control signals for the cooling, filtering, and load control systems switching devices. In the process, a device equipped with a transformer temperature measuring channel adjusts the parameters of the thermal mathematical model of the transformer organized in the BRAOP 5 block and overwrites the values in the database organized in the DB 9 block. To reduce the cost of the device, the temperature measuring channel (DTT 2 ) can only be equipped with transformers for which correction temperature coefficients are not known that correspond to the values of the K-factor of the network (or another indicator of the quality of EE). The data accumulated by the device connected to the serial transformer can be distributed to devices that control the operation of transformers of the same series and similar parameters. However, equipping the device with a transformer temperature measuring channel is not necessary.

The temperature of the most heated point of the transformer in the block BRAOP 5 for the mode of increasing the load is determined as follows.

The temperature of the NNT in the thermal regime of temperature increase is calculated with the interval Δt = t _{n + 1} -t _n = 4τ _rpm (min.) According to the following formulas:

, (2)

, (2)

- средняя температура окружающей среды (°C) за период Δt (мин.) вычисляемая по формуле (°C):Where

- the average ambient temperature (° C) for the period Δt (min.) calculated by the formula (° C):

(3)

(3)

- превышение температуры масла в верхних слоях над температурой окружающей среды (°C) к концу расчетного интервала времени вычисляемое по формуле (°C):Where

- the excess of oil temperature in the upper layers over the ambient temperature (° C) at the end of the calculated time interval calculated by the formula (° C):

(4)

(four)

- установившееся превышение температуры масла в верхних слоях над температурой окружающей среды (°C) в предшествующем расчетном интервале времени,Where

- the steady-state excess of the oil temperature in the upper layers over the ambient temperature (° C) in the previous calculated time interval,

- расчетное превышение температуры масла в верхних слоях над температурой окружающей среды (°C) в установившемся режиме с эквивалентным коэффициентом нагрузки К_n+1 рассчитываемое по формуле (°C):

- the calculated excess of the oil temperature in the upper layers above the ambient temperature (° C) in steady state with an equivalent load factor K _{n + 1} calculated by the formula (° C):

(5)

(5)

- номинальное значение превышения температуры масла в верхних слоях над температурой окружающей среды (°C), d - отношение потерь короткого замыкания к потерям холостого хода трансформатора (о.е.), x - показатель степени масла (о.е.).where K _{n + 1} is the equivalent value of the load factor in the estimated time interval calculated as the arithmetic average of the initial and final values of the load factors (p.u.),

- the nominal value of the excess of oil temperature in the upper layers over the ambient temperature (° C), d is the ratio of short circuit losses to transformer idle losses (pu), x is the oil degree index (pu).

τ is the thermal time constant of the transformer (min.);

- превышение температуры наиболее нагретой точки обмотки над температурой масла в верхних слоях (°C) к концу текущего расчетного интервала времени вычисляемое по формуле (°C):

- excess of the temperature of the warmest point of the winding over the temperature of the oil in the upper layers (° C) by the end of the current calculated time interval calculated by the formula (° C):

(6)

(6)

- установившееся значение превышения температуры наиболее нагретой точки обмотки над температурой масла в верхних слоях (°C) в предшествующем расчетном интервале времени,Where

- the steady-state value of the temperature rise of the most heated winding point over the temperature of the oil in the upper layers (° C) in the previous calculated time interval,

- расчетное значение превышения температуры наиболее нагретой точки обмотки над температурой масла в верхних слоях (°C) в установившемся режиме с эквивалентным коэффициентом нагрузки К_n+1 рассчитываемое по формуле (°C):

- the calculated value of the temperature rise of the most heated winding point over the oil temperature in the upper layers (° C) in steady state with an equivalent load factor K _{n + 1} calculated by the formula (° C):

(7)

(7)

- номинальное значение превышения температуры наиболее нагретой точки обмотки над температурой масла в верхних слоях (°C), y - показатель степени обмотки (о.е.);Where

- the nominal value of the temperature rise of the most heated winding point over the oil temperature in the upper layers (° C), y is the indicator of the degree of winding (pu);

Ψ - correction factor taking into account additional losses with the corresponding value of the K-factor of the network (pu).

The temperature of the most heated point of the transformer in the block BRAOP 5 for the mode of load reduction is determined as follows.

The temperature of the NNT in the thermal regime of temperature reduction is calculated with the interval Δt = t _{n + 1} -t _n = 4τ _rpm (min.), According to the following formulas (° C):

(8)

(8)

- средняя температура окружающей среды (°C) за период Δt вычисляемая по формуле (°C):Where

- the average ambient temperature (° C) for the period Δt calculated by the formula (° C):

(9)

(9)

- превышение температуры масла в верхних слоях над температурой окружающей среды (°C) к концу расчетного интервала времени вычисляемое по формуле (°C):Where

- the excess of oil temperature in the upper layers over the ambient temperature (° C) at the end of the calculated time interval calculated by the formula (° C):

(10)

(10)

- установившееся превышение температуры масла в верхних слоях над температурой окружающей среды (°C) в предшествующем расчетном интервале времени,Where

- the steady-state excess of the oil temperature in the upper layers over the ambient temperature (° C) in the previous calculated time interval,

- расчетное превышение температуры масла в верхних слоях над температурой окружающей среды (°C) в установившемся режиме с эквивалентным коэффициентом нагрузки K_n+1 рассчитываемое по формуле (°C):

- the calculated excess of the oil temperature in the upper layers over the ambient temperature (° C) in steady state with an equivalent load factor K _{n + 1} calculated by the formula (° C):

, (11)

, (eleven)

- номинальное значение превышения температуры масла в верхних слоях над температурой окружающей среды (°C), d - отношение потерь короткого замыкания к потерям холостого хода трансформатора (о.е.), x - показатель степени масла (о.е.), τ - тепловая постоянная времени трансформатора (мин.);where K _{n + 1} is the equivalent value of the load factor in the estimated time interval calculated as the arithmetic average of the initial and final values of the load factors (p.u.),

is the nominal value of the excess of oil temperature in the upper layers over the ambient temperature (° C), d is the ratio of short circuit losses to transformer idle losses (p.u.), x is an indicator of the degree of oil (pu), τ - thermal time constant of the transformer (min.);

- превышение температуры наиболее нагретой точки обмотки над температурой масла в верхних слоях (°C) к концу текущего расчетного интервала времени вычисляемое по формуле (°C):

- the excess of the temperature of the warmest point of the winding over the temperature of the oil in the upper layers (° C) by the end of the current calculated time interval calculated by the formula (° C):

(12)

(12)

- установившееся превышение температуры наиболее нагретой точки обмотки над температурой масла в верхних слоях (°C) в предшествующем расчетном интервале времени,Where

- the steady-state excess of the temperature of the warmest point of the winding over the temperature of the oil in the upper layers (° C) in the previous calculated time interval,

- расчетное значение превышения температуры наиболее нагретой точки обмотки над температурой масла в верхних слоях (°C) в установившемся режиме с эквивалентным коэффициентом нагрузки K_n+1 рассчитываемое по формуле (°C):

- the calculated value of the temperature rise of the most heated winding point over the oil temperature in the upper layers (° C) in steady state with an equivalent load factor K _{n + 1} calculated by the formula (° C):

(13)

(13)

- номинальное значение превышения температуры наиболее нагретой точки обмотки над температурой масла в верхних слоях (°C), y - показатель степени обмотки (о.е.);Where

- the nominal value of the temperature rise of the most heated winding point over the oil temperature in the upper layers (° C), y is the indicator of the degree of winding (pu);

Ψ - correction factor taking into account additional losses with the corresponding value of the K-factor of the network (pu).

Thus, the claimed device, controlling the harmonic composition of the mains voltage, estimates the additional losses, calculates the expected temperature and prevents overheating, which causes accelerated aging of the insulation, and as a result, increased maintenance costs, a possible emergency failure of the transformer. The device generates a signal that can be used to control the filter, if used in conjunction with the device. The coordinated operation of the device and the filter, if used together, increases the quality of the mains voltage, reduces the loss of electricity in electrical installations.

Claims (2)

1. A control device for additional losses of electricity in transformers, containing the control object - a transformer, characterized in that it contains an ambient temperature sensor, a current sensor connected to the control object, connected to an analog-to-digital converter unit, which, in turn, is connected directly with the unit for calculating and analyzing the main indicators, with the unit for calculating the integral indicators and with the unit for calculating the K-factor of the network, connected to the unit for calculating the temperature correction, while at the unit for calculating integral indicators, a database unit is connected, and a database unit is connected to the input of the unit for calculating the temperature correction, connected to the input of the unit for calculating and analyzing key indicators, connected to the graphical interpretation and signaling unit, to the control unit, to the knowledge unit connected to data block. 2. The device according to claim 1, characterized in that the device is additionally equipped with a temperature sensor mounted on a transformer connected to an analog-to-digital converter unit.

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