CN102255273B - A Direct Current Melting Method - Google Patents

Abstract

The invention relates to a high-efficiency direct-current ice melting method. The direct-current ice melting method comprises the steps that direct-current ice melting is started when the ice coating thickness of a circuit does not exceed a designed value, two leads are connected in series and then connected into the direct-current ice melting device to melt ice on two phases of leads, and the two leads which have finished ice melting are connected in parallel and then connected in series with a third lead to be connected into the direct-current ice melting device to melt ice on a third lead. And in the process of direct-current ice melting, the three-phase lead is automatically switched to be connected to the ice melting device for ice melting by controlling the operation of the direct-current side disconnecting link. The ice melting method can safely and quickly realize ice melting of the power transmission line, can effectively delay the growth of ice coating on the line and consumes least electric energy.

Description

A Direct Current Melting Method

technical field

The invention relates to a direct current ice melting method, which belongs to the innovative technology for the application of direct current ice melting to a power transmission line of a power transmission network.

Background technique

After the ice disaster in 2008, my country's electric power science and technology workers independently carried out the research and development of DC ice-melting technology and devices, and successfully developed a high-power DC ice-melting device with completely independent intellectual property rights. Various types such as transformers and vehicle-mounted mobile types have been promoted and applied throughout the country. the

In January 2009, Guizhou Power Grid Corporation carried out DC deicing on 500kV Fushi Ⅱ Line, 220kV Fujiu Line, 110kV Funiu Line and 110kV Shuishumei Line. The Zhaoda I line has carried out DC ice melting, and Guangdong Power Grid Corporation has carried out DC ice melting on the 110kV Tongmei Line. In November 2009, Yunnan Power Grid Corporation carried out DC deicing on the 110 kV large and medium T lines. The initial practical application shows that the DC deicing technology is an effective means of deicing the power grid. the

In January 2011, large-scale icing hit the Southern Power Grid again. The 19 sets of DC ice-melting devices installed in the Southern Power Grid all played a major role. A total of 227 DC ice-melting operations were performed on lines above 110kV, of which 500kV AC lines 40 More times, the power of the DC ice melting device has been fully utilized.

Ice-covered overload causes transmission line tripping and equipment damage. The jumping and galloping of conductors caused by natural deicing of the weather will also cause transmission line tripping and equipment damage. Untimely melting of ice may also cause conductor jumping and galloping, which will also cause transmission equipment damage. At the same time, in the process of icing, when one side of the wire is covered with ice, the center of gravity will shift, and the twisting of the wire will facilitate further ice accumulation on all sides and accelerate the growth of ice coating. Important means of ice. According to the statistical data of heavy ice period in 2008, the daily average thickness of ice coating on the line is about 5mm. If it is necessary to control the icing of the line to no more than 10mm, the line needs to be melted every 2 days. The practical application of DC deicing devices in 2011 also proved that timely and efficient deicing is an important means to ensure the safety of transmission lines.

Contents of the invention

The object of the present invention is to provide a direct current ice melting method with convenient operation.

The technical solution of the present invention is: the DC deicing method of the present invention, the DC deicing device used in the DC deicing method includes a converter, a DC side switch, a control and protection system, and the three-phase input connection of the converter To the AC power supply, the positive and negative outputs of the DC side of the converter are respectively connected to the three-phase AC line that needs to be melted through the DC side switch when the DC is melting. The DC side switch includes the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the first switch S1 and the second switch S2 on the DC side switch converter side are connected in parallel to the negative pole of the converter, the third switch S3 It is connected in parallel with the fourth switch S4 and then connected to the positive pole of the converter; the first switch S1 on the DC side switch line side is connected to the ice-melting line A, and the second switch S2 and the third switch S3 are connected in parallel to the Phase B of the ice-melting line is connected, and the fourth knife switch S4 is connected with phase C of the ice-melting line. The DC ice-melting method includes the following steps:

1) When the ice thickness of the line exceeds the warning value, the DC ice melting process of the line will be started;

2) Connect the A and B-phase wires in series and connect them to the DC ice-melting device through the DC side switch, close the first switch S1 and the third switch S3, open the second switch S2 and the fourth switch S4, That is, the A and B phase conductors are connected in series with the DC ice melting device through the first switch S1 and the third switch S3 in the DC side switch;

3) After closing the isolation switch K, close the circuit breaker QF, issue an unlock command on the control and protection system to unlock the DC ice melting device, increase the DC current to the designed ice melting current of the wire at a rate of 300-600A/s, and wait for the line to overturn. Ice falls off; after the line ice falls off, the control and protection system issues a blocking command, and the output current of the DC ice melting device drops to the minimum allowable value at a set rate of 300-600A/s before blocking;

4) After the DC ice-melting device is locked, open and close the DC side switch, close the second switch S2 and the fourth switch S4, keep the first switch S1 closed, and open the third switch S3, which will be completed The two-phase conductors A and B for melting ice are connected in parallel, connected in series with the third conductor C, and then connected to the DC deicing device;

5) Unlock the DC ice melting device again, and increase the output current of the DC ice melting device at a rate of 300-600A/s to the designed melting current of the line, and wait for the third wire C phase ice to fall off; after the line ice falls off, When the control and protection system issues a blocking command, the output current of the DC deicing device drops to the minimum allowable value at a set rate of 300-600A/s and then is blocked to complete the three-phase line melting;

6) Turn on the AC side circuit breaker QF, the isolation switch K and the DC side switch of the DC deicing device, and restore the operation of the deicing line that has been completed.

During the above process, the AC side circuit breaker QF and the isolation switch K remain closed.

The above-mentioned warning value for exceeding the ice coverage ratio is 0.4-0.6.

Since the DC deicing device of the present invention adopts a structure including a converter, control and protection equipment, and a DC side knife switch, the DC deicing method of the present invention starts to perform DC deicing when the ice thickness of the line has not exceeded the design value. The first step is to connect the two wires in series and connect them to the DC ice melting device to complete the ice melting of the two-phase wires. The wire melted ice. During the DC ice melting process, by controlling the operation of the DC side knife switch, there is no need to disconnect the AC side circuit breaker QF and close the isolation knife switch, and automatically switch the three-phase wires to connect to the ice melting device for ice melting. The DC deicing device of the present invention can ensure fast and safe deicing of the three-phase line, greatly improving the safety and reliability of the system; at the same time, it reduces the switching operation of the switching knife switch and the on-site wiring work for deicing. The DC ice melting method of the present invention is a method for safely and quickly realizing the ice melting of transmission lines, which can effectively delay the growth of line ice coating, consume the least electric energy, and avoid equipment damage caused by ice coating exceeding the design value, DC ice melting or natural deicing process. Practical DC ice melting method. the

Description of drawings

Figure 1 is a schematic diagram of the connection between the 12-pulse DC ice-melting device and the ice-melting circuit.

Fig. 2 is a schematic diagram of the connection between the 6-pulse DC ice-melting device and the ice-melting circuit.

Detailed ways

Below in conjunction with accompanying drawing and embodiment description is as follows:

Example 1:

The schematic diagram of the connection between the 12-pulse DC ice-melting device and the ice-melting circuit is shown in Figure 1. After the icing ratio of the transmission line reaches 0.4-0.6, the line will be out of service, the three-phase ends of the three-phase line will be short-circuited, and the head end will be connected to the DC ice-melting device.

Close the first switch S1 and the third switch S3 in the DC side switch 2 in Fig. 1, the second switch S2 and the fourth switch S4 are disconnected, close the switch QF after closing the isolation switch K, That is, the ice-melting loop is formed by the A-phase, B-phase wires and the ice-melting device. Unlock the DC ice-melting device, increase the DC current to the designed ice-melting current of the conductor at a rate of 300-600A/s, and wait for the phase A and phase B conductors to be iced off; When a blocking command is issued, the output current of the DC ice-melting device drops to the minimum allowable value at a set rate of 300-600A/s and then blocks.

After the DC ice-melting device is locked, open and close the DC side switch, close the second switch S2 and the fourth switch S4, and then disconnect the third switch S3, and the parallel connection of the A-phase and B-phase wires will be completed. After that, it is connected in series with the C-phase wire and then connected to the DC ice-melting device.

Unlock the DC ice melting device again, and increase the output current of the DC ice melting device at a rate of 300-600A/s to the designed melting current of the line, and wait for the ice on the C-phase wire to fall off; after the ice on the C-phase wire falls off, the control system will send out Blocking command, the output current of the DC ice melting device drops to the minimum allowable value at a set rate of 300-600A/s and then blocks.

After disconnecting the circuit breaker QF on the AC side, disconnect the isolation switch K, then disconnect the first switch S1, the second switch S2 and the fourth switch S4 on the DC side, and finally resume the operation of the ice-melting line.

Example 2:

6. The schematic diagram of the connection between the pulsating DC ice-melting device and the ice-melting circuit is shown in Figure 2.

After the icing ratio of the transmission line reaches 0.4-0.6, the line will be out of service, the three-phase ends of the three-phase line will be short-circuited, and the head end will be connected to the DC ice-melting device.

Close the first switch S1 and the third switch S3 on the DC side in Figure 1, close the second switch S2 and the fourth switch S4, close the isolation switch K on the AC side, and then close the circuit breaker QF, that is The ice-melting loop is formed by the A-phase and B-phase wires and the ice-melting device. Unlock the DC ice-melting device, increase the DC current to the designed ice-melting current of the conductor at a rate of 300-600A/s, and wait for the phase A and phase B conductors to be iced off; When a blocking command is issued, the output current of the DC ice-melting device drops to the minimum allowable value at a set rate of 300-600A/s and then blocks.

After the DC ice-melting device is locked, open and close the DC side switch, close the second switch S2 and the fourth switch S4, and then disconnect the third switch S3, and the parallel connection of the A-phase and B-phase wires will be completed. After that, it is connected in series with the C-phase wire and then connected to the DC ice-melting device.

Unlock the DC ice melting device again, and increase the output current of the DC ice melting device at a rate of 300-600A/s to the designed melting current of the line, and wait for the ice on the C-phase wire to fall off; after the ice on the C-phase wire falls off, the control system will send out Blocking command, the output current of the DC ice melting device drops to the minimum allowable value at a set rate of 300-600A/s and then blocks.

After disconnecting the AC side circuit breaker QF, disconnect the K isolation switch, then separate the first DC switch S1, the second switch S2 and the fourth switch S4, and finally resume the operation of the ice-melting line.

Claims (3)

1. A DC deicing method, the DC deicing device used in the DC deicing method comprises a converter (1), a DC side switch (2), a control protection system (3), a converter (1 ) is connected to the AC power supply, and the positive and negative outputs of the DC side of the converter (1) are respectively connected to the three-phase AC line that needs to be melted through the DC side knife switch (2) when the DC side is melting ice. The switch (2) includes the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4. The first switch S1 and the second switch on the converter side of the DC side switch (2) The switch S2 is connected in parallel to the negative pole of the converter (1), the third switch S3 and the fourth switch S4 are connected in parallel to the positive pole of the converter (1); the DC side switch (2) line side The first knife switch S1 is connected to the deicing line A, the second knife gate S2 and the third knife gate S3 are connected in parallel to the B phase of the deicing line, and the fourth knife gate S4 is connected to the C phase of the deicing line. It is characterized in that the direct current ice melting method comprises the following steps: 1) When the ice thickness of the line exceeds the warning value, the DC ice melting process of the line will be started; 2) Connect the wires of phase A and B in series to the DC ice melting device through the DC side switch (2), close the first switch S1 and the third switch S3, and close the second switch S2 and the fourth switch S4 Disconnect, that is, the A and B phase conductors are connected to the DC ice-melting device after being connected in series through the first knife switch S1 and the third knife switch S3 in the DC side knife switch (2); 3) After closing the isolation switch K, close the circuit breaker QF, issue an unlock command on the control and protection system (3) to unlock the DC ice-melting device, and increase the DC current to the designed ice-melting current of the wire at a rate of 300-600A/s. Wait for the line to be iced off; after the line is iced off, the control and protection system issues a blocking command, and the output current of the DC deicing device drops to the minimum allowable value at a set rate of 300-600A/s before blocking; 4) After the DC ice-melting device is locked, open and close the DC side switch (2), close the second switch S2 and the fourth switch S4, keep the first switch S1 closed, and open the third switch S3, Connect the two-phase conductors A and B that have been melted in parallel, connect them in series with the third conductor C, and connect them to the DC deicing device; 5) Unlock the DC ice melting device again, and increase the output current of the DC ice melting device at a rate of 300-600A/s to the designed melting current of the line, and wait for the third wire C phase ice to fall off; after the line ice falls off, When the control and protection system issues a blocking command, the output current of the DC deicing device drops to the minimum allowable value at a set rate of 300-600A/s and then is blocked to complete the three-phase line melting; 6) Turn on the AC side circuit breaker QF, the isolation switch K and the DC side switch of the DC deicing device, and restore the operation of the deicing line that has been completed. 2. The DC deicing method according to claim 1, characterized in that the AC side circuit breaker QF and the isolation switch K remain closed during the above process. 3. The direct current ice melting method according to claim 1, characterized in that the warning value for exceeding the ice coating ratio is 0.4-0.6.

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