WO2022267802A1

WO2022267802A1 - Drying device and method for insulation damping treatment of large ampere-turns current transformer

Info

Publication number: WO2022267802A1
Application number: PCT/CN2022/094931
Authority: WO
Inventors: 林建军; 姜兆福; 张鸿升; 李晓彬
Original assignee: 华能伊敏煤电有限责任公司
Priority date: 2021-06-24
Filing date: 2022-05-25
Publication date: 2022-12-29
Also published as: CN113532029A

Abstract

A drying device and method for insulation damping treatment of a large ampere-turns current transformer. The drying device comprises a group of current transformer secondary windings (1). The group of current transformer secondary windings (1) and a voltmeter (2) are connected in parallel. An interface at one end is an interface S1, and the other end is connected to an ampere meter in series and then is an interface S2. There are four current transformer secondary windings in the group of current transformer secondary windings (1), the first three current transformer secondary windings are respectively connected to the ampere meter (3) in series and then connected to another ampere meter. The interface S1 and the interface S2 are respectively connected to an output interface (8) of a low-frequency power supply device. A grounding wire (4), an RS232 communication interface (5), a protection input interface (6), a protection output interface (7), an output interface (8), a safety device (9) and a power supply (10) are respectively mounted above the low-frequency power supply device. According to the drying device and the drying method, by reducing the power frequency of the dried large ampere-turns current transformer, the purpose of drying is achieved while the voltage is reduced and a secondary coil is not discharged.

Description

Drying device and drying method for damp treatment of current transformer insulation with large ampere turns

technical field

The invention relates to a drying device and a drying method for treating the insulation of a current transformer with a large ampere-turn number and being damp.

Background technique

For small ampere-turns, such as 1250/5 current transformers to deal with the problem of insulation and moisture heating, ordinary 400V voltage regulators can be used to pressurize the CT twice to make it reach the rated current. The required equipment is simple and the effect is good. , but for large ampere-turns, such as 1250/1 current transformer, the insulation is damp, and when the secondary coil needs 1600V voltage, the secondary coil can reach the rated current of 4A (4 groups of secondary parallel connections), and the voltage is difficult to meet the requirements. At this time, the series resonance vacuum short-circuit drying method can be used for voltage compensation, but for the larger ampere-turns such as: LBT5-220W2 CT produced by Ataki Dayi Hu Electric Co., Ltd. in 2012, the power frequency secondary current reaches At the rated current (1 ampere), its secondary voltage reaches 8000V, but the secondary insulation design is only about 2000V. Using the power frequency resonance method is very easy to damage the secondary insulation, and it is also easy to cause internal discharge during vacuum drying, which cannot reach the rated current. dry.

Contents of the invention

The purpose of the present invention is to provide a drying device and drying method for treating the insulation of a large ampere-turns current transformer with moisture. The secondary coil is discharged, so that heating and vacuuming are carried out at the same time, so as to achieve the purpose of drying.

technical solution

Above-mentioned purpose realizes by following technical scheme:

A drying device for treating the insulation of a large ampere-turns current transformer with moisture, which consists of: a set of secondary windings of current transformers, a set of secondary windings of current transformers, and a voltmeter connected in parallel, one end of which is connected to S1 interface, the other end is connected with the ammeter in series to be the S2 interface, and a set of said current transformer secondary windings is 4, wherein the first 3 are respectively connected with the ammeter in series and then connected with another ammeter, the said S1 interface, the The S2 interface described above is respectively connected to the output interface of the low-frequency power supply device, and the top of the low-frequency power supply device is respectively equipped with a ground wire, an RS232 communication interface, a protection input interface, a protection output interface, the output interface, a safety device, and a power supply, A main switch, a voltage adjustment button and a display screen are respectively installed below the low-frequency power supply device.

A drying device and a drying method for treating the insulation of a current transformer with a large ampere-turn number by moisture, the method comprising the following steps:

Firstly, by short-circuiting the primary winding of the current transformer, an automatically adjustable low-frequency voltage is applied to the secondary winding of the current transformer to make the coil reach the rated current and realize heating and drying;

Adopt AC power supply, use low-frequency power supply instead of industrial frequency power supply, reduce the voltage applied to the secondary side of CT, and select an automatically adjustable low-frequency power supply device with an output of 0-400V/0-5A and a frequency range of 1-50Hz. In the low-frequency power supply device, when the input CT secondary rated constant current mode is set, the equipment will automatically boost the voltage and reduce the frequency. After reaching the set current, it will maintain a constant current output to the CT secondary side to achieve the purpose of CT drying. The voltage on the secondary side is up to 400V;

The voltage of the current transformer low-frequency vacuum short-circuit drying method will not discharge the secondary coil. Heating and vacuuming are carried out at the same time. At least 20 times of vacuuming are required, and a minimum of 20 times of vacuum breaking are required. The time required for 20 cycles is up to 120 hours;

The specific operation process is: connect the output of the low-frequency power supply to the CT secondary protection terminal, and short-circuit the other terminals, set it as a unit, set the temperature control module, vacuum degree control module, time control module, and dry air heating control module as a unit, Set the upper and lower limits of CT drying temperature, vacuum degree, and drying air temperature through temperature and pressure sensors, automatically and regularly control the start and stop of low-frequency power supply, vacuum pump, and drying air heater, and realize remote control and monitoring through cameras and wireless transmission systems Function, so that the drying site is unattended during the whole drying process.

Beneficial effect

1. The present invention is a drying device and drying method for the insulation of a large ampere-turns current transformer and a drying method. The structure and method reduce the voltage by reducing the frequency of the dried current transformer with a large ampere-turns. After the wet current transformer is dried, and the voltage will not cause the secondary coil to discharge, heating and vacuuming can be carried out at the same time to achieve the purpose of drying, which can minimize the workload and improve work efficiency.

2. The present invention selects the output 0-400V/0-5A, frequency range 1-50Hz automatic adjustable frequency conversion power supply device, in the frequency conversion power supply device setting input CT secondary rated constant current mode, the equipment will automatically boost and drop Frequency, after reaching the set current, it will maintain a constant current output to the secondary side of the CT to achieve the purpose of CT drying.

Description of drawings

Accompanying drawing 1 is the electrical wiring diagram of frequency conversion heating of the present invention.

Accompanying drawing 2 is the structural diagram of the low-frequency power supply device of the present invention.

Among them: 1. Secondary winding of current transformer, 2. Voltmeter, 3. Ammeter, 4. Ground wire, 5. RS232 communication interface, 6. Protection input interface, 7. Protection output interface, 8. Output interface, 9, Safety device, 10, power supply, 11, main switch, 12, voltage adjustment button, 13, display screen.

detailed description

Example 1:

A drying device for treating the insulation of a current transformer with a large ampere-turn number and being exposed to moisture. Its composition includes: a set of secondary windings 1 of the current transformer, a set of the secondary windings of the current transformer, and a voltmeter 2 connected in parallel, one end of which is connected to the It is the S1 interface, and the other end is connected with the ammeter in series to be the S2 interface. A set of said current transformer secondary windings is 4, and the first 3 of them are respectively connected with the ammeter 3 in series and then connected with another ammeter. The said S1 The interface and the S2 interface are respectively connected to the output interface 8 of the low-frequency power supply device, and the ground wire 4, the RS232 communication interface 5, the protection input interface 6, the protection output interface 7, and the above-mentioned low-frequency power supply device are installed respectively. The output interface, safety device 9, power supply 10, and the bottom of the low-frequency power supply device are respectively equipped with a main switch 11, a voltage adjustment button 12, and a display screen 13.

Example 2:

According to the drying method of the drying device of the large ampere-turns current transformer insulation damp treatment described in embodiment 1, the method comprises the following steps:

For large CTs with higher ampere-turns, because the saturation inflection point voltage of the iron core is very high (from several thousand volts to tens of thousands of volts), it is easy to cause the insulation breakdown and discharge of the secondary winding, which cannot be realized by the power frequency electric drying method, for example: A The LBT5-220W2 type CT produced by Taqi Dayihu Electric Co., Ltd. in 2012, the volt-ampere characteristic test of the protective winding TPY, when the power frequency secondary current reaches the rated current (1 ampere), its secondary voltage reaches 8000V, but the secondary The insulation design is only about 2000V, and the power frequency resonance method cannot reach the rated current at all;

If you want to add a low voltage to the CT secondary coil to make the coil reach the rated current, you have to start with the volt-ampere characteristic curve of the current transformer core. From the volt-ampere characteristic curve of the current transformer with a higher ampere-turn number, it can be seen that At the rated frequency, the inflection point (iron core saturation) voltage is very high, from thousands of volts to tens of thousands of volts. In order to reduce the iron core saturation point, the method of reducing the power frequency can be adopted, which can be explained by the formula of the induced electromotive force of the transformer;

E. = 4.44fWBS = K f B

K = 4.44WS

In the formula, E - induced electromotive force (V);

f - power frequency (Hz);

W - the number of turns of the coil;

B ——Magnetic flux density (T)

S ——Core cross-sectional area (m2)

K - constant of proportionality

It can be seen from the above formula that if B is kept unchanged, because the value of K is constant, when the power frequency is reduced by 10 times, the induced voltage is also reduced by 10 times, and the voltage at the inflection point (core saturation) of the core volt-ampere characteristic curve can be reduced from several thousand volts to hundreds of volts;

The principle is to short-circuit the primary winding of the current transformer and apply a low-frequency voltage that can be automatically adjusted to the secondary winding to make the coil reach the rated current and realize heating and drying. The winding loss and the eddy current loss of the iron core working in saturated excitation also generate heat, so the heating rate is faster than that of direct current, and the direct current will cause the transformer core to have residual magnetic flux, resulting in a decrease in the accuracy of the transformer, while the alternating current Then there will be no residual magnetism, and the use of low-frequency power supply instead of industrial frequency power supply can greatly reduce the voltage applied to the secondary side of the CT, and the work is very safe. If you choose to output 0-400V/0-5A, and the frequency range is 1-50Hz, it can be automatically adjusted. Variable frequency power supply device, in the variable frequency power supply device, when the input CT secondary rated constant current mode is set, the equipment will automatically increase the voltage and reduce the frequency. Purpose, the maximum voltage applied to the CT secondary side is 400V;

Through the above analysis, the low-frequency vacuum short-circuit drying method for current transformers is feasible, and this voltage will not cause the secondary coil to discharge, and heating and vacuuming can be carried out at the same time. Practice has proved that if the power frequency vacuum short-circuit drying method wants to achieve the purpose of drying, it often needs to carry out at least 20 times of vacuuming, and it also needs to carry out at least 20 times of vacuum breaking, and 20 cycles need as much as 120 hours. Low-frequency vacuum short-circuit drying method measurement, the drying time can be reduced by at least 5 days, which can minimize the workload and improve work efficiency;

The low-frequency vacuum short-circuit drying method is to reduce the voltage by reducing the frequency, so as not to discharge the secondary coil, so that heating and vacuuming can be carried out at the same time. The specific working process can connect the output of the low-frequency power supply to the secondary protection terminal of the CT, and short-circuit the other terminals. , as a unit; set the temperature control module, vacuum degree control module, time control module, and drying air heating control module as a unit, and set the upper and lower limits of CT drying temperature, vacuum degree, and drying air temperature through temperature and pressure sensors , automatically and regularly control the start and stop of low-frequency power supply, vacuum pump, and drying air heater; it can also realize remote control and monitoring functions through cameras and wireless transmission systems, so that the drying site is unattended during the entire drying process, and the work of employees is minimized again. volume, improve work efficiency;

Among them, the electrical wiring diagram of frequency conversion heating shown in Figure 1, the output terminals S1 and S2 of the low-frequency power supply device shown in Figure 2 are connected to the parallel windings of four 3S, 4S, 5S, and 6S secondary windings TPY of the current transformer.

Claims

A drying device for treating the insulation of a current transformer with a large ampere-turn number and being exposed to moisture, which comprises: a set of secondary windings of a current transformer, characterized in that: a set of secondary windings of a current transformer and a voltmeter are connected in parallel, wherein One end interface is the S1 interface, and the other end is the S2 interface after being connected in series with the ammeter. A group of said secondary windings of the current transformer is 4, of which the first 3 are respectively connected in series with the ammeter and then connected to another ammeter. The S1 interface and the S2 interface are respectively connected to the output interface of the low-frequency power supply device, and the ground wire, the RS232 communication interface, the protection input interface, the protection output interface, the described output interface, and the insurance are respectively installed above the low-frequency power supply device. device, power supply, and the bottom of the low-frequency power supply device is respectively equipped with a main switch, a voltage adjustment button, and a display screen.
A drying method for a drying device for treating the insulation of a large ampere-turn current transformer according to claim 1, characterized in that: the method comprises the following steps:

Firstly, by short-circuiting the primary winding of the current transformer, an automatically adjustable low-frequency voltage is applied to the secondary winding of the current transformer to make the coil reach the rated current and realize heating and drying;

Adopt AC power supply, use low-frequency power supply instead of industrial frequency power supply, reduce the voltage applied to the secondary side of CT, and select an automatically adjustable low-frequency power supply device with an output of 0-400V/0-5A and a frequency range of 1-50Hz. In the low-frequency power supply device, when the input CT secondary rated constant current mode is set, the equipment will automatically boost the voltage and reduce the frequency. After reaching the set current, it will maintain a constant current output to the CT secondary side to achieve the purpose of CT drying. The voltage on the secondary side is up to 400V;

The voltage of the current transformer low-frequency vacuum short-circuit drying method will not discharge the secondary coil. Heating and vacuuming are carried out at the same time. At least 20 times of vacuuming are required, and a minimum of 20 times of vacuum breaking are required. The time required for 20 cycles is up to 120 hours;

The specific operation process is: connect the output of the low-frequency power supply to the CT secondary protection terminal, and short-circuit the other terminals, set it as a unit, set the temperature control module, vacuum degree control module, time control module, and dry air heating control module as a unit, Set the upper and lower limits of CT drying temperature, vacuum degree, and drying air temperature through temperature and pressure sensors, automatically and regularly control the start and stop of low-frequency power supply, vacuum pump, and drying air heater, and realize remote control and monitoring through cameras and wireless transmission systems Function, so that the drying site is unattended during the whole drying process.