Dual power switching control protection device for valve cooling system

Abstract

The application relates to a dual-power switching control protection device for a valve cooling system, which comprises a control circuit corresponding to each power inlet, wherein the control circuit has a main branch and an auxiliary branch; the main branch comprises a control switch and a coil of a first intermediate relay in series; the auxiliary branch is connected in parallel with the coil of the first intermediate relay, wherein the auxiliary branch comprises a contact of the first intermediate relay, a coil of a power contactor and a current-limiting resistor in series; wherein the current-limiting resistor is connected in parallel with a short-circuit branch which is used for being turned on after starting and being turned off again. The technical scheme of the application can effectively avoid the adhesion of output contact points of a valve cooling control device, and can effectively avoid the continuous large heat generation of the coil of the power contactor, so as to improve the reliability and safety of equipment and power supply.

Description

Technical Field

[0001] This application generally relates to the field of electrical control technology. More specifically, this application relates to a dual-power switching control and protection device for a valve cooling system. Background Technology

[0002] In recent years, my country's ultra-high voltage direct current (UHVDC) transmission technology has developed rapidly. In DC transmission projects, converter valves are core equipment, playing a crucial role in processes such as AC-DC conversion. A suitable temperature environment is essential for the safe and stable operation of converter valves; therefore, all converter valves are equipped with a converter valve cooling system (hereinafter referred to as the valve cooling system).

[0003] In existing technologies, valve cooling systems generally include various equipment such as internal cooling electric heaters, external cooling electric heaters, raw water pumps, makeup water pumps, and electric actuators. These devices are typically powered by the AC busbar in an AC power supply cabinet. For example, air cooler fans are powered by the AC busbar in the fan power supply cabinet, while cooling tower fans, spray pumps, bypass filter pumps, and drainage pumps are powered by the AC busbar in the cooling tower power supply cabinet. If any of these AC power busbars fail, the corresponding equipment will malfunction, leading to the shutdown of the valve cooling system. This prevents the system from continuing to provide cooling services to the converter valves, ultimately causing the converter valves to stop operating, resulting in serious safety accidents and economic losses.

[0004] To ensure the safety of the converter valve's power supply, the AC power supply for the valve cooling system typically uses two power input lines, which can automatically switch between each other. For example, if the power quality of one power input line fails, the system can switch to the other power input line. Power quality information includes fault information such as undervoltage, loss of voltage, and overvoltage. Under normal conditions, one power input line is selected for operation. When the aforementioned fault information is received, a control signal is output to activate the other power input line.

[0005] Specifically, Figure 1 The diagram illustrates the electrical principle of the main AC power supply circuit. L1, L2, and L3 represent the three-phase AC busbars, which are connected to two power input lines: the first power input line XT1 and the second power input line XT2. The first power input line XT1 has its main contact KWN-1 connected in series with it, and KA1 is the output contact of the valve cooling control device, used to control the main contact KWN-1. Similarly, the second power input line XT2 has its main contact KWR-1 connected in series with it, and KA2 is the output contact of the valve cooling control device, used to control the main contact KWR-1.

[0006] Figure 2An electrical schematic diagram of a dual power supply switching control circuit based on existing technology is shown.

[0007] SA1 and SB1 represent manual switches, while KA1, KB1 and KA2, KB2 represent remote control switches, i.e., the output contacts of the valve cooling control device. QCN and QCR represent circuit breakers. X1 represents the control power supply, which can be taken from the AC bus or obtained by rectifying the AC bus. KWN-2 and KWR-2 represent the auxiliary contacts of the power contactor. Figure 2 The circuit shown includes two loops, each corresponding to a power input line (i.e., the first power input line and the second power input line). The contacts and coils of the two power contactors in each loop are connected in series to form an interlock circuit, ensuring that only one power contactor operates at a time.

[0008] Based on actual operating conditions, this dual-power switching control method has the following technical problems:

[0009] 1) The control power for the first and second power input lines is taken from the same power supply section X1. If this power supply section fails, not only will the dual power supply switching be impossible, but neither AC power supply can be put into operation, and the AC bus will lose power, thus affecting the normal operation of the valve cooling equipment.

[0010] 2) During the coil of the power contactor (such as KWN) is energized, a short-term overvoltage is generated, which will impact the control power supply (such as X1). Long-term use may cause control power supply failure, thus posing a safety hazard to the system.

[0011] 3) The coil of the power contactor (such as KWN) has a large inrush current at the moment of engagement, which may reach more than 10A in some cases. However, the rated current of the output contacts of the valve cooling control device (such as KA1) is generally small. Long-term or frequent operation can easily cause the contacts to stick together, which will lead to the inability to complete the power switching action and affect the normal operation of the valve cooling equipment.

[0012] 4) After the power contactor has completed its operation, the coil of the power contactor (such as KWN) is always directly connected to the two ends of the control power supply. However, according to the characteristics of the contactor, only a small current is needed to maintain the energized state. If a large current is maintained for a long time, it will cause the contactor coil to overheat severely, accelerate aging, and pose a fire hazard.

[0013] Based on this, this application considers optimizing the dual power supply switching device. In addition to ensuring the normal switching function of the dual power supply, it should also protect the output contacts of the valve cooling control device and the coil of the power contactor to avoid problems such as contact sticking and severe coil overheating. Summary of the Invention

[0014] The purpose of this application is to provide a dual power supply switching control and protection device for a valve cooling system, which at least solves one or more technical problems described in the background art.

[0015] According to one aspect of this application, a dual power supply switching control and protection device for a valve cooling system is provided, wherein the valve cooling system includes two power input lines, each power input line is provided with a corresponding main contact of a power contactor, and the dual power supply switching control and protection device includes a control circuit corresponding to each power input line, wherein the control circuit has a main branch and a secondary branch; the main branch includes a control switch and a coil (KN1) of a first intermediate relay connected in series; the secondary branch is connected in parallel with the coil (KN1) of the first intermediate relay, wherein the secondary branch includes the contacts (KN1-1 / KN1-2) of the first intermediate relay connected in series, the coil (KWN) of the power contactor, and a current-limiting resistor (R1); wherein the current-limiting resistor (R1) is connected in parallel with a short-circuit branch, the short-circuit branch being used to conduct after startup and then disconnect again.

[0016] In one embodiment, a short-circuit control branch for controlling the short-circuit branch is also included.

[0017] In one embodiment, the short-circuit branch includes the contacts (KN2-1) of the second intermediate relay; the short-circuit control branch includes the coil (KN2) of the second intermediate relay connected in series and the auxiliary contacts (KWN-2) of the power contactor.

[0018] In one embodiment, the short-circuit control branch is connected in parallel with the coil (KWN) of the power contactor and in series with the contacts (KN1-1 / KN1-2) of the first intermediate relay.

[0019] In one embodiment, the short-circuit control branch is connected in parallel with the series circuit portion of the power contactor's coil (KWN) and current-limiting resistor (R1).

[0020] In one embodiment, the two power input lines include a first power input line (XT1) and a second power input line (XT2); the main branch of the control circuit corresponding to the first power input line is connected to the first control power supply (X1), and the main branch of the control circuit corresponding to the second power input line is connected to the second control power supply (X2).

[0021] In one embodiment, the first intermediate relay has two or more contacts, and the contacts of the two or more first intermediate relays are connected in series.

[0022] In one embodiment, the secondary branch is further provided with an interlocking contact (KWR-3) connected in series with the coil (KWN) of the power contactor.

[0023] In one embodiment, the control switch includes a manual switch and a remote control switch, which are connected in parallel; the remote control switch includes an output contact of a valve cooling control device.

[0024] In one embodiment, a circuit breaker is also connected in series in the main branch.

[0025] The technical solution of this application effectively avoids the valve cooling control device's output contacts from sticking together because the coil of the power contactor is not directly connected in series with the output contacts, thus improving safety. Furthermore, by using a built-in current-limiting resistor, this application effectively prevents the power contactor coil from continuously overheating during the contactor's engaged state, improving the reliability and safety of the equipment and power supply. In addition, the presence of the current-limiting resistor also reduces the starting current, protecting the power contactor coil.

[0026] Furthermore, the short-circuit control branch of this application is connected in parallel with the coil of the power contactor, which can eliminate the overvoltage generated during the contactor engagement process while ensuring the normal engagement of the AC power main circuit contactor.

[0027] Furthermore, the control power supplies corresponding to the first power contactor and the second power contactor in this application are not the same power supply. Therefore, in extreme cases, if either control power supply fails, the dual power supply switching control protection device can operate with the other control power supply to ensure that one incoming power supply is put into operation, without affecting the normal operation of the valve cooling equipment.

[0028] In summary, this application overcomes many shortcomings of the original dual-power switching circuit through reasonable circuit combination. Attached Figure Description

[0029] The above and other objects, features, and advantages of exemplary embodiments of this application will become readily understood by reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of this application are illustrated by way of example and not limitation, and the same or corresponding reference numerals denote the same or corresponding parts, wherein:

[0030] Figure 1 A schematic diagram of the main circuit for AC power supply according to existing technology;

[0031] Figure 2 A schematic diagram of the electrical principle of a dual power supply switching control circuit based on existing technology;

[0032] Figure 3 This is a schematic diagram of the electrical principle of a dual power supply switching control and protection device according to an embodiment of this application (first part);

[0033] Figure 4This is a schematic diagram of the electrical principle of a dual power supply switching control and protection device according to an embodiment of this application (Part Two). Detailed Implementation

[0034] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0035] The technical solution of this application, such as Figure 3 and Figure 4 As shown, where Figure 3 For the first power input line XT1 Figure 4 Used for the second power input line XT2. That is to say... Figure 3 It is mainly used to control the main contacts KWN-1 of the first power contactor. Figure 4 The main contact KWR-1 used to control the second power contactor, because... Figure 3 and Figure 4 The principles are basically the same, so when introducing the circuit, we mainly focus on... Figure 3 The following explanation will be based on an example. Figure 3 Therefore, in this embodiment, the term "power contactor" is used to refer to the first power contactor.

[0036] Figure 3 The first part of a dual-power switching control and protection device for a valve cooling system is shown, namely, the control circuit corresponding to the first power input line XT1. This control circuit has a main branch and a secondary branch. The main branch includes a control switch connected in series and the coil KN1 of a first intermediate relay. The secondary branch, connected in parallel with the coil KN1 of the first intermediate relay, includes the contacts KN1-1 / KN1-2 of the first intermediate relay connected in series, the coil KWN of a power contactor, and a current-limiting resistor R1. A short-circuit branch is connected in parallel with the current-limiting resistor R1. The short-circuit branch includes the contact KN2-1 of a second intermediate relay. The short-circuit control branch includes the coil KN2 of the second intermediate relay connected in series and the auxiliary contact KWN-2 of the power contactor.

[0037] In other words, in this embodiment, the contact KN2-1 of the second intermediate relay is called the short-circuit branch, and the series circuit of the coil KN2 of the second intermediate relay and the auxiliary contact KWN-2 of the power contactor is called the short-circuit control branch of the short-circuit branch.

[0038] In this embodiment, the contacts KN1-1 / KN1-2 of the first intermediate relay are normally open contacts, the auxiliary contact KWN-2 of the power contactor is a normally open contact, and the contact KN2-1 of the second intermediate relay is a normally open contact. In one embodiment, the control switch includes a manual switch SA1 and a remote control switch, which are connected in parallel; the remote control switch includes output contacts KA1 and KB1 of the valve cooling control device.

[0039] The following description Figure 3 Circuit principle:

[0040] Under normal conditions, the circuit breaker (QCN) is closed. When the manual switch SA1 is closed (or the remote control switch KA1 / KB1 is closed), the coil KN1 of the first intermediate relay is energized, and the contacts KN1-1 and KN1-2 of the first intermediate relay are closed (in this embodiment, two series contacts are provided for redundancy). The current of the secondary branch flows through the coil KWN of the power contactor and the current-limiting resistor R1, as well as the coil KN2 of the second intermediate relay and the auxiliary contact KWN-2 of the power contactor.

[0041] At this point (referred to as the first state in this embodiment), due to the series connection of the current-limiting resistor R1, the current in the coil KWN of the power contactor is relatively small. Simultaneously, because the current in the coil KWN of the power contactor is small, the auxiliary contact KWN-2 of the power contactor will not actuate and will remain closed. In other words, at startup, the current in the coil KWN of the power contactor is too small to cause the corresponding contact to actuate.

[0042] Immediately afterwards (referred to as the second state in this embodiment), the coil KN2 of the second intermediate relay in the short-circuit control branch is energized, and the contact KN2-1 of the second intermediate relay is energized. Therefore, the short-circuit branch is turned on, thereby short-circuiting the current-limiting resistor R1, which increases the current on the coil KWN of the power contactor. Finally, the main contact KWN-1 of the power contactor on the first power input line X1 is energized, and the first power input line XT1 supplies power to the system.

[0043] Next (referred to as the third state in this embodiment), when the main contact KWN-1 of the power contactor is engaged, the auxiliary contact KWN-2 of the power contactor is disengaged, thereby disconnecting the short-circuit control branch, causing the coil KN2 of the second intermediate relay to lose power. Therefore, the contact KN2-1 of the second intermediate relay is disengaged, allowing the current-limiting resistor R1 to be reconnected to the secondary branch.

[0044] Based on the circuit principle above, the existence of the first state reduces the impact on the coil KWN of the power contactor. Furthermore, since the short-circuit control branch is connected in parallel with the circuit of the coil KWN of the power contactor and the current-limiting resistor R1, the overvoltage on the coil KWN of the power contactor is limited, thereby protecting the coil KWN of the power contactor and the control power supply, extending the life of the power contactor, and reducing safety hazards.

[0045] In the second state, the current-limiting resistor R1 is short-circuited, thus providing sufficient current for the main contact KWN-1 of the power contactor to operate normally.

[0046] Since the current required by the power contactor in the steady state is relatively small (compared to when the power contactor needs to operate), in the third state, the current-limiting resistor R1 is put back into the secondary branch, thereby suppressing the current flowing through the coil KWN of the power contactor in the steady state, thus avoiding the power contactor coil KWN from maintaining a large current for a long time and reducing safety hazards.

[0047] Furthermore, in this embodiment, the remote control switch KA1 / KB1 can be the output contact of the valve cooling control device, and the manual switch SA1 and the remote control switch KA1 / KB1 are connected in parallel with the coil KWN of the power contactor. Therefore, the inrush current of the power contactor at the moment of engagement will not have a significant impact on the output contact of the valve cooling control device, thus extending the service life of the output contact of the valve cooling control device and reducing the probability of failure.

[0048] like Figure 3 As shown, in this embodiment, the short-circuit control branch is connected in parallel with the series circuit portion of the power contactor coil KWN and the current-limiting resistor R1. In other embodiments, the short-circuit control branch can also be connected in parallel with the power contactor coil KWN and in series with the contacts KN1-1 / KN1-2 of the first intermediate relay, thereby ensuring that the short-circuit control branch can be controlled by the contacts of the first intermediate relay.

[0049] As an example, the short-circuit control branch can be directly connected in parallel with the coil KWN of the power contactor. In this case, in the first state, the current-limiting resistor R1 can also limit the current flowing through the coil KWN of the power contactor. In the second state, the short-circuit branch can short-circuit the current-limiting resistor R1. In this case, due to the current shunting of the short-circuit control branch, the current flowing through the coil KWN of the power contactor is smaller.

[0050] Combination Figure 1 , Figure 3 and Figure 4In one embodiment, the system has two power input lines, including a first power input line XT1 and a second power input line XT2. The main branch of the control circuit corresponding to the first power input line is connected to the first control power supply X1, and the main branch of the control circuit corresponding to the second power input line is connected to the second control power supply X2. That is, the first control power supply X1 and the second control power supply X2 are not the same power source. For example, the first control power supply X1 and the second control power supply X2 can come from different AC buses. Therefore, in extreme cases, if either control power supply fails, the dual power supply switching control and protection device can operate with the other control power supply to ensure that one power input line is in operation and does not affect the normal operation of the valve cooling equipment.

[0051] like Figure 4 The circuit shown is Figure 3 The circuit shown is completely corresponding, for example including a third intermediate relay (e.g., KR1) that has the same function as the first intermediate relay, a fourth intermediate relay (e.g., KR2) that has the same function as the second intermediate relay, and a second power contactor (e.g., KWR) that corresponds to the first power contactor (e.g., KWN). Figure 4 The control switches include manual switch SA2 and valve cooling control device output contacts KA2 and KB2. Figure 4 The structure and working principle of the circuit shown are the same as Figure 3 They are basically the same, so I will not go into details here.

[0052] Combination Figure 3 and Figure 4 , Figure 3 The secondary branch shown also includes an interlocking contact KWR-3 of a second power contactor connected in series with the coil KWN of the first power contactor; Figure 4 The secondary branch shown also includes an interlocking contact KWN-3 of the first power contactor, which is connected in series with the coil KWR of the second power contactor. This interlocking design ensures that only one power contactor will operate at a time.

[0053] It should be understood that when the terms "first," "second," "third," and "fourth," etc., are used in the claims, description, and drawings of this application, they are only used to distinguish different objects and not to describe a specific order. The terms "comprising" and "including" used in the description and claims of this application indicate the presence of the described features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or collections thereof.

[0054] It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application. As used in this specification and claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in this specification and claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations.

[0055] As used in this specification and claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if [described condition or event] is detected" may be interpreted, depending on the context, as "once determined," "in response to determination," "once [described condition or event] is detected," or "in response to detection of [described condition or event]."

[0056] Although the embodiments of this application are described above, the content is merely an example adopted for the purpose of facilitating understanding of this application and is not intended to limit the scope and application scenarios of this application. Any person skilled in the art described in this application may make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in this application, but the scope of patent protection of this application shall still be determined by the scope defined in the appended claims.

Claims

1. A dual power switching control protection device for a valve cooling system, wherein the valve cooling system comprises two power supply lines, each of which is provided with a main contact of a corresponding power contactor, characterized in that, the dual power switching control protection device comprises a control circuit corresponding to each of the power supply lines, wherein the control circuit has a main branch and an auxiliary branch; the main branch comprises a control switch and a coil KN1 of a first intermediate relay connected in series; the auxiliary branch is connected in parallel with the coil KN1 of the first intermediate relay, wherein the auxiliary branch comprises a contact of a first intermediate relay, a coil KWN of a power contactor and a current-limiting resistor R1 connected in series; wherein the current-limiting resistor R1 is connected in parallel with a short-circuit branch, the short-circuit branch is used to be turned on after starting and turned off again; further comprising a short-circuit control branch for controlling the short-circuit branch; the short-circuit branch comprises a contact KN2-1 of a second intermediate relay; the short-circuit control branch comprises a coil KN2 of a second intermediate relay and an auxiliary contact KWN-2 of a power contactor connected in series.

2. A dual power switching control protection device for a valve cooling system according to claim 1, characterized in that, The short-circuit control branch is connected in parallel with the coil KWN of the power contactor and in series with the contact of the first intermediate relay.

3. A dual power switching control protection device for a valve cooling system according to claim 1, characterized in that, The short-circuit control branch is connected in parallel with the coil KWN of the power contactor and the current-limiting resistor R1.

4. A dual power switching control protection device for a valve cooling system according to claim 1, characterized in that, Wherein the two power supply lines comprise a first power supply line XT1 and a second power supply line XT2; The main branch of the control circuit corresponding to the first power supply line is connected to a first control power supply X1, and the main branch of the control circuit corresponding to the second power supply line is connected to a second control power supply X2.

5. A dual power switching control protection device for a valve cooling system according to claim 1, wherein The contact of the first intermediate relay is provided with two or more contacts, and the two or more contacts of the first intermediate relay are connected in series.

6. A dual power switching control protection device for a valve cooling system according to any one of claims 1 to 5, characterized in that, The auxiliary branch is further provided with an interlocking contact KWR-3 connected in series with the coil KWN of the power contactor.

7. A dual power switching control protection device for a valve cooling system according to claim 6, characterized in that, The control switch comprises a manual switch and a remote control switch, and the manual switch and the remote control switch are connected in parallel; the remote control switch comprises a valve cooling control device output contact.

8. A dual power switching control protection device for a valve cooling system according to claim 7, characterized in that, The main branch is further connected in series with a circuit breaker.

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