CN109950037B - Distribution transformer body drying processing variable current power supply device and processing method - Google Patents
Distribution transformer body drying processing variable current power supply device and processing method Download PDFInfo
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- CN109950037B CN109950037B CN201910280441.4A CN201910280441A CN109950037B CN 109950037 B CN109950037 B CN 109950037B CN 201910280441 A CN201910280441 A CN 201910280441A CN 109950037 B CN109950037 B CN 109950037B
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Abstract
The device carries out variable flow heating and variable pressure by using a low-voltage side short circuit method, provides a novel three-phase transformer high-low voltage winding wire resistance measuring module, and realizes the aim of respectively measuring the temperatures of high-low voltage windings. The device data analysis unit can analyze the temperature of the winding and then issue a control instruction to the variable flow control unit, so that the winding can be heated simultaneously or independently. Through the structure and the method, the technical problems of long processing time, poor processing effect and influence on the service life of the transformer in the prior art are solved.
Description
Technical Field
The invention belongs to the field of transformer equipment, and particularly relates to a variable current power supply device for drying a distribution transformer body and a drying method.
Background
The distribution transformer is used as important power transmission and transformation equipment, and good insulation of the transformer body is an important factor for guaranteeing safe operation of the distribution transformer. The distribution transformer body is mainly assembled by a transformer winding coil, an iron core, an insulating material and a clamping piece. The insulating material is distributed on the iron core and the coil and is used for improving the insulating level of the transformer and improving the insulating voltage resistance and the electric breakdown resistance.
The general structure of the body of the distribution transformer and the distribution of the used insulating materials are as follows: the iron core is in the innermost layer, the low-voltage winding is uniformly surrounded around the iron core through the isolation of the insulation paper board, the high-voltage winding is isolated around the low-voltage winding through the insulation paper board, the high-voltage winding and the low-voltage winding lead are wrapped by the insulation paper for insulation treatment, and the lead support and the clamping piece are made of insulation laminated wood materials.
The existing process method for heating the body of the transformer is mainly divided into a hot air circulation drying process a; b. a variable pressure method drying process; c. a low frequency short circuit heating method;
a. the hot air circulation drying process comprises the following steps: the transformer body is dried by a method of providing heating heat through a heat pipe or an electric heating wire in a drying tank or a drying chamber and circulating hot air in the drying tank or the drying chamber through a fan.
b. The pressure-changing drying process method comprises the following steps: and evaporating and condensing the heat conduction oil by using the heat pipe to complete the drying treatment of the transformer insulation.
When a hot air and pressure-variable method is adopted for drying, because the radial depth of the transformer body is thicker, particularly for low-voltage windings and iron cores distributed in the transformer body, the drying effect of the inner layer is not obvious, and an absolute dry layer, namely, outer dry and inner wet, is easy to appear, belongs to a drying blind area in a traditional mode, and the process generally has the defects of low thermal efficiency, long treatment time and the like.
c. The low-frequency short circuit drying method comprises the following steps: the drying method of heating from inside to outside by short-circuiting the low-voltage winding and electrifying and heating the high-voltage winding is adopted, the problems of the two methods can be effectively solved, and the drying method is an upgrading version of the former two methods.
When the traditional low-frequency short-circuit drying process is adopted, although heating is performed from inside to outside, the high-voltage winding and the low-voltage winding are different in wire diameter due to the fact that wires of high-voltage windings and wires of low-voltage windings are different in wire diameter, temperature difference exists between the high-voltage windings and the low-voltage windings, but in the structure of the conventional distribution transformer at present, a reserved temperature measuring channel or a pre-buried temperature measuring optical fiber cannot be provided for a transformer body generally, so that temperature measurement of the transformer body drying process is mainly completed through an external thermocouple, the temperature can only represent the temperature of a high-voltage side winding, accurate temperature measurement cannot be performed on the temperature of a low-voltage side winding, independent heating and drying treatment on an undertemperature winding cannot be achieved, heating is performed simultaneously, the drying degree of the low.
Disclosure of Invention
Aiming at the problems, the invention provides a distribution transformer body drying treatment variable current power supply device and a drying treatment method, and variable current heating and variable voltage are carried out by using a low-voltage side short circuit method.
In order to achieve the purpose, the invention adopts the technical scheme that: a variable current power supply device for drying a distribution transformer body is characterized in that: comprises a control system module, a variable current power switch module and an air pressure variable pressure processing module;
the control system module comprises a signal input end of a parameter acquisition unit, a current and voltage sensor in the variable current power switch module and an air pressure sensor in the air pressure transformation processing module are connected, a signal output end of the parameter acquisition unit is connected with a data analysis processing unit, a signal output end of the data analysis processing unit divides an output signal into two paths, one path is connected with an air pressure control execution unit in the air pressure transformation processing module after passing through an air pressure control unit, and the other path is connected with a three-phase/single-phase rectification power unit and a three-phase power output unit in the variable current power switch module after passing through a variable current control unit;
the current-converting power switch module is connected with a winding of the distribution transformer, and the current-voltage sensor detects an electric signal of the winding; the three-phase/single-phase rectification power unit and the three-phase power output unit are in line connection with the high-voltage winding side of the distribution transformer;
the air pressure transformation processing module and the distribution transformer body are arranged in the same box body, the air pressure control execution unit consists of an air circulation unit and an air drying unit, an air inlet of the air circulation unit is connected with an air outlet of the vacuum tank unit, and an air inlet of the air drying unit is connected with an air inlet of the vacuum tank unit.
The control system module consists of a data analysis processing unit, a parameter acquisition unit, a transformer winding temperature detection unit, an air pressure control unit and a variable flow control unit; the current transformation control unit controls the electric signals connected to the high and low windings of the distribution transformer through a three-phase/single-phase rectification power unit and a three-phase power output unit in the current transformation power switch module.
The three-phase/single-phase rectification power unit in the variable current power switch module consists of a diode, a thyristor and a single-phase or three-phase bridge rectifier circuit built by a mosfet or an IGBT; the three-phase power output unit in the current transformation power switch module consists of a three-phase bridge inverter circuit built by mosfets or IGBTs; the current and voltage sensor inputs the detected voltage and current electrical quantity signals of the primary winding of the distribution transformer into the control system module, and receives the current signals with control signals output by the control system module to supply power for the high-voltage winding of the body of the distribution transformer.
The current signal with the control signal is three different types of current signals, which are respectively: three-phase high-frequency sine wave output current signals, or three-phase low-frequency sine wave output current signals, or single-phase direct current output current signals.
The air pressure transformation processing module consists of a vacuum tank unit, an air pressure monitoring unit and an air pressure control execution unit, wherein an air pressure sensor of the air pressure monitoring unit provides air pressure non-electrical signals to be input into the control system module; the control system module controls the air circulation unit to pump out air and enter the air drying unit for drying, the air output end of the air drying unit after drying is connected with the vacuum tank unit, and the air drying unit is used for discharging water vapor generated by the transformer winding in the heating process through reciprocating operation.
A method for drying a distribution transformer body by the device is characterized by comprising the following steps:
1) presetting: inputting rated parameters of the transformer as initial values into a data analysis processing unit;
2) a preparation stage:
2.1) vacuum tank leak test: the method comprises the following steps that a leakage test is carried out on a transformer vacuum tank through an air pressure transformation processing module, an air pressure monitoring unit in the air pressure transformation processing module monitors the air pressure value of the transformer vacuum tank in real time, and meanwhile, the initial values of a primary winding and a secondary winding of a transformer are measured through a parameter acquisition unit in a control system module; in the actual operation process, the primary winding and the secondary winding are changed along with the change of the environmental temperature;
2.2) vacuumizing:
the control system module carries out vacuum pumping operation on the air pressure variable pressure processing module, so that the vacuum state of the device body can be approached, air containing moisture in the vacuum tank is removed, and the vacuum state is kept to be continuously pumped out;
3) a heating stage I:
at this stage, controlling an air drying unit in the air pressure control execution unit, carrying out ventilation operation on a ventilation valve arranged at the bottom of the vacuum tank unit, and continuously injecting dry hot air for circularly filtering moisture dried by the transformer; heating the transformer winding through a variable current power switch module; in the heating process, monitoring the temperature of the transformer winding by a parameter acquisition unit of a control system module, taking the set rated temperature as the limit of the average winding temperature, and heating insulating parts except the coil to remove moisture;
4) and (3) a stabilization stage:
after the average temperature of the transformer winding reaches the rated temperature, stopping heating, and entering a stable state stage to prevent the transformer from being continuously heated and damaged; in the process of the stabilization stage, the drying hot gas is continuously circulated, so that the water vapor is prevented from being condensed in the vacuum tank;
5) a heating stage II:
after the stabilization phase is finished, carrying out secondary heating on the transformer box; the transformer winding is heated to be higher than the rated temperature by the variable frequency current and the circulating drying hot gas and is heated to be 10 ℃; measuring the winding resistance through a transformer winding temperature measuring unit to determine the primary winding temperature and the secondary winding temperature; if the temperature of the primary winding is lower than the rated temperature plus 10 ℃, the primary winding is heated by the direct current from the variable current power switch module until the primary winding is heated to the rated temperature plus 10 ℃;
6) and (3) a final drying stage:
and after the drying stage, the circulating hot gas is not used, the air pressure variable pressure processing module is controlled to release air pressure, and dry nitrogen is released to enter the vacuum tank to complete the drying treatment.
In the heating stage I and the heating stage II, the temperature rise speed is controlled within 1 ℃/min to limit depolymerization of the cellulose heat-insulating layer and ensure that parts of the non-coil heat-insulating layer are properly heated.
The method for measuring the initial values of the primary winding and the secondary winding of the transformer by the parameter acquisition unit in the step 2.1) comprises the following steps: the high-frequency, low-frequency and direct-current signals output by the transformer initial control variable-current control unit are applied to a high-voltage winding of a transformer body by using a transformer T-shaped equivalent circuit, and the average temperature of each winding is directly calculated by measuring high-voltage side resistance and low-voltage side resistance respectively according to a resistance temperature equivalent formula.
The method for measuring the initial values of the primary winding and the secondary winding of the transformer by the parameter acquisition unit specifically comprises the following steps:
the output signal of the current transformation control unit controls the current transformation power switch module to output three-phase sine wave current with the frequency of 300Hz, the three-phase sine wave current is applied to a high-voltage winding of the transformer body, the short-circuit state of a low-voltage side winding is kept, and a group of total leakage reactance of the transformer with the current frequency is calculated; the output signal of the current transformation control unit controls the current transformation power switch module to output three-phase sine wave current with the frequency of 10Hz, the three-phase sine wave current is applied to a high-voltage winding of the transformer body, the short-circuit state of a low-voltage side winding is kept, the total leakage reactance of another group of transformers with the current frequency is calculated, and the equations are combined to obtain the total leakage inductance and the total resistance value of the transformer body;
the output signal of the current transformation control unit controls the current transformation power switch module to output single-phase direct current which is applied to a high-voltage winding of the transformer body, the direct current cannot be transmitted to a low-voltage side due to the law of electromagnetic induction, and the low-voltage side wiring mode has no influence on the direct current input at the high-voltage side; after the direct current is stabilized, measuring input voltage and input current, and calculating to obtain a resistance value which is a single-phase high-voltage side resistance; then, the output of the variable current power switch module is three phases, and when a single-phase direct current signal is used, the three phases of the output need to be divided into three groups of inputs, and the resistance value of each phase of the A/B/C three-phase winding at the high-voltage side of the transformer is measured;
the high-voltage winding resistance and the low-voltage winding resistance are respectively calculated in an alternating current and direct current mode, and then the actual temperature of each winding is calculated by using a temperature and resistance conversion formula.
The beneficial effects created by the invention are as follows:
the invention provides a drying device and a drying method suitable for online measurement of the resistance of each winding of a three-phase distribution transformer body based on the defects, wherein the resistance of each winding of the transformer body is directly measured, the actual temperature of each winding is obtained, manual intervention is not needed in the drying process, the control system module is controlled to perform coordination control on a variable flow control module and an air pressure transformation processing module, and the drying device and the drying method are mainly applied to a heating and drying process of the three-phase distribution transformer body in an oil-free state. The invention not only ensures the drying effect on the inside of the body, but also avoids the defects of high energy consumption, long processing time and the like of the traditional scheme.
The invention realizes accurate temperature measurement of each winding of the transformer, realizes simultaneous heating of high and low voltage windings of the transformer, and independent heating of undertemperature windings in a targeted manner, thereby improving the drying effect of the transformer body and simultaneously protecting the insulation life of the windings reaching the drying temperature.
Drawings
Fig. 1 is a flowchart of a control method.
Fig. 2 is a circuit block diagram.
Fig. 3 is a schematic circuit diagram a.
Fig. 4 is a circuit schematic b.
Fig. 5 is a schematic circuit diagram c.
Fig. 6 is a circuit schematic d.
Fig. 7 is a circuit schematic e.
Fig. 8 is a schematic circuit diagram f connected to the schematic circuit diagram e.
Fig. 9 is a schematic circuit diagram g connected to the schematic circuit diagram f.
Detailed Description
As shown in fig. 2-9, a variable current power supply device for drying a distribution transformer body includes a control system module 1, a variable current power switch module 2, and an air pressure transformation processing module 3;
the control system module 1 comprises a signal input end of a parameter acquisition unit, and is connected with a current and voltage sensor in the variable current power switch module 2 and an air pressure sensor in the air pressure variable pressure processing module 3, a signal output end of the parameter acquisition unit is connected with a data analysis processing unit, a signal output end of the data analysis processing unit divides an output signal into two paths, one path is connected with an air pressure control execution unit in the air pressure variable pressure processing module 3 after passing through an air pressure control unit, and the other path is connected with a three-phase/single-phase rectification power unit and a three-phase power output unit in the variable current power switch module 2 after passing through a variable current control unit;
the current-converting power switch module 2 is connected with a winding of a distribution transformer, and a current-voltage sensor detects an electric signal of the winding; the three-phase/single-phase rectification power unit and the three-phase power output unit are in line connection with the high-voltage winding side of the distribution transformer;
the air pressure transformation processing module 3 and the distribution transformer body are arranged in the same box body, the air pressure control execution unit consists of an air circulation unit and an air drying unit, an air inlet of the air circulation unit is connected with an air outlet of the vacuum tank unit, and an air inlet of the air drying unit is connected with an air inlet of the vacuum tank unit.
The control system module 1 consists of a data analysis processing unit, a parameter acquisition unit, a transformer winding temperature detection unit, an air pressure control unit and a variable flow control unit; the current transformation control unit controls the electric signals connected to the high and low windings of the distribution transformer through a three-phase/single-phase rectification power unit and a three-phase power output unit in the current transformation power switch module 2.
The three-phase/single-phase rectification power unit in the variable current power switch module 2 consists of a diode, a thyristor and a single-phase or three-phase bridge rectifier circuit built by a mosfet or an IGBT; the three-phase power output unit in the current transformation power switch module 2 consists of a three-phase bridge inverter circuit built by mosfets or IGBTs; the current and voltage sensor inputs detected voltage and current electrical quantity signals of the primary winding of the distribution transformer into the control system module 1, and receives current signals with control signals output by the control system module 1 to supply power to the high-voltage winding of the body of the distribution transformer.
The current signal with the control signal is three different types of current signals, which are respectively: three-phase high-frequency sine wave output current signals, or three-phase low-frequency sine wave output current signals, or single-phase direct current output current signals.
The air pressure transformation processing module 3 is composed of a vacuum tank unit, an air pressure monitoring unit and an air pressure control execution unit, an air pressure sensor of the air pressure monitoring unit provides air pressure non-electrical signals to be input into the control system module 1, the air pressure control execution unit is composed of an air circulation unit and an air drying unit outside the vacuum tank unit, and the air pressure control execution unit receives control signals sent by the control system module 1 and controls the air pressure in the vacuum tank unit; the control system module 1 controls the air circulation unit to pump out air and enter the air drying unit for drying, the air output end of the air drying unit after drying is connected with the vacuum tank unit, and the air drying unit is used for discharging water vapor generated by the transformer winding in the heating process through reciprocating operation.
As shown in fig. 1, a method for drying a distribution transformer body by the device includes the steps of:
1) presetting: inputting rated parameters of the transformer as initial values into a data analysis processing unit;
2) a preparation stage:
2.1) vacuum tank leak test: the leakage test is carried out on the transformer vacuum tank through the air pressure transformation processing module 3, an air pressure monitoring unit in the air pressure transformation processing module monitors the air pressure value of the transformer vacuum tank in real time, and meanwhile, the initial values of a primary winding and a secondary winding of the transformer are measured through a parameter acquisition unit in the control system module (1); in the actual operation process, the primary winding and the secondary winding are changed along with the change of the environmental temperature;
2.2) vacuumizing:
the control system module (1) carries out vacuum pumping operation on the air pressure variable pressure processing module 3, so that the device body can reach a state close to vacuum, air containing moisture in the vacuum tank is removed, and the vacuum state is kept to be continuously pumped out;
3) a heating stage I:
at this stage, controlling an air drying unit in the air pressure control execution unit, carrying out ventilation operation on a ventilation valve arranged at the bottom of the vacuum tank unit, and continuously injecting dry hot air for circularly filtering moisture dried by the transformer; heating the transformer winding through a variable current power switch module; in the heating process, monitoring the temperature of the transformer winding by a parameter acquisition unit of the control system module 1, taking the set rated temperature as the limit of the average winding temperature, and heating the insulating parts except the coil to remove moisture;
4) and (3) a stabilization stage:
after the average temperature of the transformer winding reaches the rated temperature, stopping heating, and entering a stable state stage to prevent the transformer from being continuously heated and damaged; in the process of the stabilization stage, the drying hot gas is continuously circulated, so that the water vapor is prevented from being condensed in the vacuum tank;
5) a heating stage II:
after the stabilization phase is finished, carrying out secondary heating on the transformer box; the transformer winding is heated to be higher than the rated temperature by the variable frequency current and the circulating drying hot gas and is heated to be 10 ℃; measuring the winding resistance through a transformer winding temperature measuring unit to determine the primary winding temperature and the secondary winding temperature; if the temperature of the primary winding is lower than the rated temperature plus 10 ℃, the primary winding is heated by the direct current from the variable current power switch module until the primary winding is heated to the rated temperature plus 10 ℃;
6) and (3) a final drying stage:
and after the drying stage is started, the circulating hot gas is not used, the air pressure variable pressure processing module 3 is controlled to release air pressure, and dry nitrogen is released to enter the vacuum tank to finish the drying processing.
In the heating stage I and the heating stage II, the temperature rise speed is controlled within 1 ℃/min to limit depolymerization of the cellulose heat-insulating layer and ensure that parts of the non-coil heat-insulating layer are properly heated.
The method for measuring the initial values of the primary winding and the secondary winding of the transformer by the parameter acquisition unit in the step 2.1) comprises the following steps: the high-frequency, low-frequency and direct-current signals output by the transformer initial control variable-current control unit are applied to a high-voltage winding of a transformer body by using a transformer T-shaped equivalent circuit, and the average temperature of each winding is directly calculated by measuring high-voltage side resistance and low-voltage side resistance respectively according to a resistance temperature equivalent formula.
The method for measuring the initial values of the primary winding and the secondary winding of the transformer by the parameter acquisition unit specifically comprises the following steps:
the output signal of the current transformation control unit controls the current transformation power switch module to output three-phase sine wave current with the frequency of 300Hz, the three-phase sine wave current is applied to a high-voltage winding of the transformer body, the short-circuit state of a low-voltage side winding is kept, and a group of total leakage reactance of the transformer with the current frequency is calculated; the output signal of the current transformation control unit controls the current transformation power switch module to output three-phase sine wave current with the frequency of 10Hz, the three-phase sine wave current is applied to a high-voltage winding of the transformer body, the short-circuit state of a low-voltage side winding is kept, the total leakage reactance of another group of transformers with the current frequency is calculated, and the equations are combined to obtain the total leakage inductance and the total resistance value of the transformer body;
the output signal of the current transformation control unit controls the current transformation power switch module to output single-phase direct current which is applied to a high-voltage winding of the transformer body, the direct current cannot be transmitted to a low-voltage side due to the law of electromagnetic induction, and the low-voltage side wiring mode has no influence on the direct current input at the high-voltage side; after the direct current is stabilized, measuring input voltage and input current, and calculating to obtain a resistance value which is a single-phase high-voltage side resistance; then, the output of the variable current power switch module is three phases, and when a single-phase direct current signal is used, the three phases of the output need to be divided into three groups of inputs, and the resistance value of each phase of the A/B/C three-phase winding at the high-voltage side of the transformer is measured;
the high-voltage winding resistance and the low-voltage winding resistance are respectively calculated in an alternating current and direct current mode, and then the actual temperature of each winding is calculated by using a temperature and resistance conversion formula.
Example 1:
as shown in fig. 1-9, a drying device for transformer includes a control system module, a variable power switch module and a pressure variable processing module. The control system module collects parameters of sensors arranged in the conversion power switch module and the air pressure transformation processing module, sends control instructions after analyzing and processing the data, and respectively controls the output current of the conversion power switch module and the air pressure intensity level of the air pressure transformation processing module. A220V/380V power supply is connected to a variable current power switch module, a sensor arranged in the module provides voltage and current electrical quantity signals to be input into a system control module, receives control signals sent by the system control module, and outputs different types of current signals to supply power for a high-voltage winding of a body of a distribution transformer. An air pressure sensor arranged in the air pressure transformation processing module provides air pressure non-electrical signals to be input into the control system module, receives control signals sent by the system control module, and controls the air pressure in the vacuum tank unit.
The control system module is electrically connected with all other modules and sends control signals, and the control system module consists of a data analysis processing unit, a parameter acquisition unit, a transformer winding temperature measurement unit, an air pressure control unit and a variable flow control unit. The variable current signal output by the current transformation power switch module is connected with the high-voltage winding side of the body of the distribution transformer through a wire, so that the high-voltage winding and the low-voltage winding of the distribution transformer simultaneously generate current or generate current on one side, and further the winding of the transformer generates heat. The air pressure variable pressure processing module consists of a vacuum tank unit, an air pressure monitoring unit and an air pressure control execution unit, wherein the air pressure execution unit consists of an air circulation unit and an air drying unit.
Introduction of a control system module: the device consists of a data analysis unit, a parameter acquisition unit, a transformer winding temperature measurement unit, an air pressure control unit and a variable flow control unit. The method is characterized in that: after the control system module is electrified, rated parameters of the transformer are input into the data analysis processing unit as initial values, the parameter acquisition unit acquires and uploads air pressure parameters and voltage and current electric quantity parameters in the variable current power switch module to the data analysis processing unit, the temperature of the high and low windings of the transformer in an initial state is recorded by utilizing a method for realizing the temperature measurement of each winding of the transformer respectively, the temperature of each winding is preset as a controlled target, the variable current power switch module is controlled to heat the high and low windings of the transformer simultaneously when the winding temperature is close to room temperature in the initial heating stage, the current frequency and effective value output by the variable current switch frequency module are automatically adjusted according to the maximum value of the power factor, and meanwhile, the control system module carries out evacuation operation on the air pressure transformation processing module 3 to ensure that the transformer body can be close to vacuum and the vacuum state is kept, the transformer winding temperature measuring device is used for discharging moisture evaporated from a transformer body and is matched with the heating of the variable current switch module, the transformer winding temperature measuring unit is always switched with the heating process in the heating process, when one side winding reaches the expected temperature, the variable current power switch module is switched into a single-side heating working mode, when all windings of the transformer body reach the expected temperature, the heating is stopped, the drying stage is started, the air pressure variable pressure processing module 3 is controlled to release air pressure, dry air is released to enter the vacuum tank, and the drying processing is completed.
The current transformation power switch module: the current transformation power switch module consists of a three-phase or single-phase rectification power unit and a three-phase power output unit. The three-phase or single-phase rectification power unit is characterized by comprising a single-phase or three-phase bridge rectifier circuit built by a diode, a thyristor, a mosfet or an IGBT, a three-phase power output unit is composed of a three-phase bridge inverter circuit built by a mosfet or an IGBT, a sensor arranged in the module provides voltage and current electric quantity signals to be input into a system control module and receives control signals sent by the system control module, and three different types of current signals are output to supply power for a high-voltage winding of a distribution transformer body, so that different control requirements are realized. The method comprises the following steps: the three-phase high-frequency sine wave outputs a current signal, the three-phase low-frequency sine wave outputs a current signal, and the single-phase direct current outputs a current signal.
The air pressure variable pressure processing module: the device consists of a vacuum tank unit, an air pressure monitoring unit and an air pressure control execution unit, wherein the air pressure execution unit consists of an air circulation unit and an air drying unit. An air pressure sensor arranged in the air pressure transformation processing module provides air pressure non-electrical signals to be input into the control system module, receives control signals sent by the system control module, and controls the air pressure in the vacuum tank unit. The vacuum tank unit comprises an air inlet and an air outlet, the air inlet of the air circulation unit is connected with the air outlet of the vacuum tank unit, and the air inlet of the air drying unit is connected with the air inlet of the vacuum tank unit. The control system module controls the air circulation unit to pump out air to enter the air drying unit for drying, the dried air enters the vacuum tank unit again, and the air drying unit is used for discharging moisture generated by the transformer winding in the heating process in a reciprocating mode.
The method for realizing the temperature measurement of each winding of the transformer comprises the following steps:
the method comprises the following steps of measuring high-voltage side resistance and low-voltage side resistance respectively, and directly calculating the average temperature of each winding according to a resistance temperature equivalent formula, wherein the specific implementation method comprises the following steps: by using the T-shaped equivalent circuit of the transformer, high-frequency, low-frequency and direct-current signals output by the transformer initial control variable-current control unit are applied to the high-voltage winding of the transformer body without changing the short-circuit state of the low-voltage winding.
(1) And controlling a control signal of the variable current control unit to output three-phase sine wave current with the frequency of 300Hz to the variable current power switch module to be applied to a high-voltage winding of the transformer body, keeping a short-circuit state of a low-voltage side winding, calculating a group of total leakage reactance of the transformer with the current frequency, controlling the control signal of the variable current control unit to output three-phase sine wave current with the frequency of 10Hz to be applied to the high-voltage winding of the transformer body, keeping the short-circuit state of the low-voltage side winding, calculating another group of total leakage reactance of the transformer with the current frequency, and combining equations to obtain the total leakage inductance and the total resistance value of the transformer body.
(2) The method comprises the steps that a control signal of a variable current control unit is controlled to be sent to a variable current power switch module to output single-phase direct current to be applied to a high-voltage winding of a transformer body, direct current cannot be transmitted to a low-voltage side due to the law of electromagnetic induction, therefore, the low-voltage side wiring mode has no influence on input direct current of the high-voltage side, after the direct current is stabilized, input voltage and input current are measured, the resistance value obtained through calculation at the moment is a single-phase high-voltage side resistance, the output of the variable current power switch module is three phases, when single-phase direct current signals are used, three groups of inputs are required, and the resistance value of each phase.
(3) The high-voltage winding resistance and the low-voltage winding resistance can be respectively calculated in an alternating current and direct current mode, and then the actual temperature of each winding is calculated by using a temperature and resistance conversion formula.
Carrying out the step
(1) And (3) a vacuum tank leakage testing stage:
the leakage test is carried out on the transformer vacuum tank through the air pressure transformation processing module, an air pressure monitoring unit in the air pressure transformation processing module monitors the air pressure value of the transformer vacuum tank in real time, and meanwhile, the initial values of the primary winding and the secondary winding of the transformer are measured through a parameter acquisition unit in the control system module. In actual operation, the primary winding and the secondary winding are changed along with the change of the ambient temperature.
(2) And (3) vacuumizing stage:
the control system module carries out vacuum pumping operation on the air pressure variable pressure processing module 3, so that the vacuum state of the device body can be approached, air containing moisture in the vacuum tank is removed, and the vacuum state is kept to be continuously pumped out.
(3) A heating stage I:
in the continuous evacuation state, the vent valve is opened, and the dry hot air is continuously injected for heating the dried moisture by the circulating filter transformer. And heating the transformer winding through the variable-current power switch module. In the heating process, the temperature of the transformer winding is monitored by a parameter acquisition unit of a control system module, the average winding temperature is 100 ℃ as a limit, the transformer is prevented from being damaged due to overhigh temperature, and insulating parts except the coil are heated to remove moisture.
Because the moisture content of the heat-insulating layer is high, the temperature rise speed must be controlled within 1 degree/minute to limit depolymerization of the cellulose heat-insulating layer and ensure that parts of the non-coil heat-insulating layer are properly heated.
(4) And (3) a stabilization stage:
after the average temperature of the transformer winding reaches 100 ℃, the heating is stopped, and the stable state stage is entered, so as to prevent the transformer from being damaged due to continuous heating. During the stabilization phase, the dry hot gas is continuously circulated to prevent condensation of water vapor in the vacuum tank.
(5) A heating stage II:
and after the stabilization stage is finished, carrying out secondary heating on the transformer box. The variable frequency current and circulating dry hot air heated the transformer windings to a temperature of T11 (average winding temperature measured by resistance is 110 degrees celsius). The primary winding temperature and the secondary winding temperature are determined by measuring the winding resistance by a transformer winding temperature measuring unit. And if the temperature of the primary winding is less than 110 ℃, the secondary winding is heated by the direct current from the variable current power switch module until the temperature of the primary winding is 110 ℃. Heating the primary winding to 110 degrees celsius is important because it has the highest voltage rating and the thickest insulating material.
(6) And (3) a final drying stage:
and after the drying stage is started, the circulating hot gas is not used, the air pressure variable pressure processing module 3 is controlled to release air pressure, and dry nitrogen is released to enter the vacuum tank to finish the drying processing.
Claims (7)
1. A method for carrying out drying treatment on a distribution transformer body is characterized by comprising the following steps:
1) presetting: inputting rated parameters of the transformer as initial values into a data analysis processing unit;
2) a preparation stage:
2.1) vacuum tank leak test: the leakage test is carried out on the transformer vacuum tank through the air pressure transformation processing module (3), an air pressure monitoring unit in the air pressure transformation processing module monitors the air pressure value of the transformer vacuum tank in real time, and meanwhile, the initial values of a primary winding and a secondary winding of the transformer are measured through a parameter acquisition unit in the control system module (1); in the actual operation process, the primary winding and the secondary winding are changed along with the change of the environmental temperature;
the method for measuring the initial values of the primary winding and the secondary winding of the transformer by the parameter acquisition unit comprises the following steps: the high-frequency, low-frequency and direct-current signals output by the transformer initial control variable-current control unit are respectively applied to a high-voltage winding of a transformer body by utilizing a transformer T-shaped equivalent circuit, and the average temperature of each winding is directly calculated by respectively measuring high-voltage side resistance and low-voltage side resistance according to a resistance temperature equivalent formula;
the method for measuring the initial values of the primary winding and the secondary winding of the transformer by the parameter acquisition unit specifically comprises the following steps:
the output signal of the current transformation control unit controls the current transformation power switch module to output three-phase sine wave current with the frequency of 300Hz, the three-phase sine wave current is applied to a high-voltage winding of the transformer body, the short-circuit state of a low-voltage side winding is kept, and a group of total leakage reactance of the transformer with the current frequency is calculated; the output signal of the current transformation control unit controls the current transformation power switch module to output three-phase sine wave current with the frequency of 10Hz, the three-phase sine wave current is applied to a high-voltage winding of the transformer body, the short-circuit state of a low-voltage side winding is kept, the total leakage reactance of another group of transformers with the current frequency is calculated, and the equations are combined to obtain the total leakage inductance and the total resistance value of the transformer body;
the output signal of the current transformation control unit controls the current transformation power switch module to output single-phase direct current which is applied to a high-voltage winding of the transformer body, the direct current cannot be transmitted to a low-voltage side due to the law of electromagnetic induction, and the low-voltage side wiring mode has no influence on the direct current input at the high-voltage side; after the direct current is stabilized, measuring input voltage and input current, and calculating to obtain a resistance value which is a single-phase high-voltage side resistance; because the output of the variable current power switch module is three phases, when a single-phase direct current signal is used, three groups of inputs are required to be divided, and the resistance value of each phase of A/B/C three-phase windings at the high-voltage side of the transformer is measured;
respectively calculating the resistance of a high-voltage winding and the resistance of a low-voltage winding in an alternating current and direct current mode, and then calculating the actual temperature of each winding by using a temperature and resistance conversion formula;
2.2) vacuumizing:
the control system module (1) carries out vacuum pumping operation on the air pressure variable pressure processing module (3), so that the device body can reach a state close to vacuum, air containing moisture in the vacuum tank is removed, and the vacuum state is kept to be continuously pumped out;
3) a heating stage I:
at this stage, controlling an air drying unit in the air pressure control execution unit, carrying out ventilation operation on a ventilation valve arranged at the bottom of the vacuum tank unit, and continuously injecting dry hot air for circularly filtering moisture dried by the transformer; heating the transformer winding through a variable current power switch module; in the heating process, monitoring the temperature of a transformer winding through a parameter acquisition unit of a control system module (1), taking the set rated temperature as the limit of the average winding temperature, and heating insulating parts except a coil to remove moisture;
4) and (3) a stabilization stage:
after the average temperature of the transformer winding reaches the rated temperature, stopping heating, and entering a stable state stage to prevent the transformer from being continuously heated and damaged; in the process of the stabilization stage, the drying hot gas is continuously circulated, so that the water vapor is prevented from being condensed in the vacuum tank;
5) a heating stage II:
after the stabilization phase is finished, carrying out secondary heating on the transformer box; the transformer winding is heated to be higher than the rated temperature by the variable frequency current and the circulating drying hot gas and is heated to be 10 ℃; measuring the winding resistance through a transformer winding temperature measuring unit to determine the primary winding temperature and the secondary winding temperature; if the temperature of the primary winding is lower than the rated temperature plus 10 ℃, the primary winding is heated by the direct current from the variable current power switch module until the primary winding is heated to the rated temperature plus 10 ℃;
6) and (3) a final drying stage:
and after the drying stage is started, the circulating hot gas is not used, the air pressure variable pressure processing module (3) is controlled to release air pressure, and dry nitrogen is released to enter the vacuum tank to finish the drying processing.
2. The method of claim 1, wherein the drying process comprises: in the heating stage I and the heating stage II, the temperature rise speed is controlled within 1 ℃/min to limit depolymerization of the cellulose heat-insulating layer and ensure that parts of the non-coil heat-insulating layer are properly heated.
3. A method of drying a body of a distribution transformer, using a variable current power supply apparatus for drying a body of a distribution transformer, as recited in claim 1, wherein: the device comprises a control system module (1), a variable-current power switch module (2) and a gas pressure variable-voltage processing module (3);
the control system module (1) comprises a signal input end of a parameter acquisition unit, a current and voltage sensor in the variable current power switch module (2) and an air pressure sensor in the air pressure transformation processing module (3) are connected, a signal output end of the parameter acquisition unit is connected with a data analysis processing unit, a signal output end of the data analysis processing unit divides an output signal into two paths, one path is connected with an air pressure control execution unit in the air pressure transformation processing module (3) after passing through an air pressure control unit, and the other path is connected with a three-phase/single-phase rectification power unit and a three-phase power output unit in the variable current power switch module (2) after passing through a variable current control unit;
the variable current power switch module (2) is connected with a winding of a distribution transformer, and a current and voltage sensor detects an electric signal of the winding; the three-phase/single-phase rectification power unit and the three-phase power output unit are in line connection with the high-voltage winding side of the distribution transformer;
the air pressure transformation processing module (3) and the distribution transformer body are arranged in the same box body, the air pressure control execution unit consists of an air circulation unit and an air drying unit, an air inlet of the air circulation unit is connected with an air outlet of the vacuum tank unit, and an air inlet of the air drying unit is connected with an air inlet of the vacuum tank unit.
4. A distribution transformer body drying process variable current power supply apparatus according to claim 3, wherein: the control system module (1) consists of a data analysis processing unit, a parameter acquisition unit, a transformer winding temperature detection unit, an air pressure control unit and a variable flow control unit; the current transformation control unit controls the electric signals connected to the high and low windings of the distribution transformer through a three-phase/single-phase rectification power unit and a three-phase power output unit in the current transformation power switch module (2).
5. A distribution transformer body drying process variable current power supply apparatus according to claim 3, wherein: the three-phase/single-phase rectification power unit in the variable current power switch module (2) consists of a diode, a thyristor and a single-phase or three-phase bridge rectification circuit built by a mosfet or an IGBT; the three-phase power output unit in the current transformation power switch module (2) consists of a three-phase bridge inverter circuit built by mosfets or IGBTs; the current and voltage sensor inputs detected voltage and current electrical quantity signals of the primary winding of the distribution transformer into the control system module (1) and receives current signals with control signals output by the control system module (1) to supply power to the high-voltage winding of the body of the distribution transformer.
6. The drying process variable-current power supply device for the body of the distribution transformer as claimed in claim 5, wherein: the current signal with the control signal is three different types of current signals, which are respectively: three-phase high-frequency sine wave output current signals, or three-phase low-frequency sine wave output current signals, or single-phase direct current output current signals.
7. A distribution transformer body drying process variable current power supply apparatus according to claim 3, wherein: the air pressure variable pressure processing module (3) consists of a vacuum tank unit, an air pressure monitoring unit and an air pressure control execution unit, an air pressure sensor of the air pressure monitoring unit provides air pressure non-electrical signals to be input into the control system module (1), the air pressure control execution unit consists of an air circulation unit and an air drying unit which are installed outside the vacuum tank unit, and the air pressure control execution unit receives control signals sent by the control system module (1) and controls the air pressure in the vacuum tank unit; the control system module (1) controls the air circulation unit to pump out air and enter the air drying unit for drying, the air output end of the air drying unit after drying is connected with the vacuum tank unit, and the air drying unit is used for discharging water vapor generated by the transformer winding in the heating process through reciprocating operation.
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| EP0543181B1 (en) * | 1991-11-18 | 1998-03-25 | MICAFIL Vakuumtechnik AG | Method of drying the solid insulating material of transformers, especially transformers for distribution installations, and apparatus therefor |
| CN101692402B (en) * | 2009-09-24 | 2012-02-29 | 保定天威集团有限公司 | Method and device for drying large-scale power transformer |
| CN102903482B (en) * | 2012-09-29 | 2016-04-06 | 苏州华电电气股份有限公司 | On-the-spot transformer's oil-treatment self-heating apparatus |
| CN203734546U (en) * | 2014-03-19 | 2014-07-23 | 国家电网公司 | Large-scale power transformer low-frequency heating device based on square wave modulation |
| CN207977206U (en) * | 2018-03-30 | 2018-10-16 | 安徽华环电气设备有限公司 | A kind of transformer heating system |
| CN108321712A (en) * | 2018-04-20 | 2018-07-24 | 国网电力科学研究院武汉南瑞有限责任公司 | A kind of transportable transformer device body drying device |
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