A DC bus switch position indication device based on AC signal injection

Abstract

The present invention provides a DC bus tie switch position indication device based on AC signal injection, which is used to indicate whether the closing state of the DC bus tie switch between two sections of DC bus in a dual-source DC system is successful or failed through an indicator light. The device is composed of an operating handle state indication circuit and a bus tie switch state indication circuit. If the bus tie switch is not closed to the correct position or the closing is not tight, the contact resistance of the bus tie switch becomes large or the circuit is broken, and the closing indicator light of the bus tie switch is not on; if the operating handle of the indicating device is in place and the indicator light is on, but the closing indicator light of the bus tie switch is not on, it can be judged that the operating handle has failed or slipped, and needs to be replaced or repaired.

Description

Technical Field

[0001] The invention relates to the technical field of power supply for substations, and in particular to a direct current busbar switch position indicating device based on alternating current signal injection. Background Art

[0002] The substation dual DC system is equipped with two 110V or 220V DC systems: two groups of batteries, two sets of chargers, each with a section of DC bus. When the two sections of DC bus are normal, they are separated by a DC bus tie switch. When the DC system is under maintenance, the DC bus tie switch is closed to achieve continuous power supply of the two sections of DC bus.

[0003] In a dual DC system, because the busbar is closed very rarely, the operating handle may be used once a year or even longer. For a DC system with a long service life, the handle may have some mechanical properties degraded after long-term storage, resulting in the busbar switch not being closed properly or not tightly engaged after operation.

[0004] When withdrawing a section of DC charger and battery for maintenance, the switch must be made through the operating handle on the panel cabinet. Two sections of busbar DC equipment driven by a set of chargers and batteries. Years of operation and maintenance records show that the operating handle may slip or the busbar switch may not be closed properly. At this time, the position indicated by the operating handle is not the actual position of the DC busbar switch, causing the operator to misjudge that the contact switch has been closed.

[0005] Since the standard DC system operating handle, bus tie switch, and DC system do not have clear indicators, the operator has no clear indication of whether the bus is in a safe working state after switching the switch. At this time, if the charger and battery to be repaired are disconnected, the DC bus section without the charger and battery will lose pressure.

[0006] If the section of the DC system to be repaired is disconnected without the bus tie breaker being fully closed and the on-site operator not noticing it, the DC bus it carries will lose voltage, and all loads on the bus will lose power, which may lead to serious consequences such as protection failure or switch failure.

[0007] There are various indicator products on the market, but none are used for DC systems. Moreover, similar products currently use the power supply line voltage as their driving power supply, so the monitored line needs to be modified during installation so that the indicator device can be connected in series to the power supply line. In this type of working mode, the indicator device not only becomes a load on the power supply line, but once the device fails and disconnects, the power supply of the equipment will be affected, increasing the risk point and reducing safety. Summary of the invention

[0008] In order to determine whether the operating handle of a DC bus tie switch is reliable and whether it can accurately indicate the real position of the DC bus tie switch, the present invention proposes an indicating device that can accurately reflect the position of the DC bus tie switch electrically, and provides a set of closing indicating devices with photoelectric indication to provide photoelectric signals to maintenance personnel during operation: after the operating handle is closed, the handle indicator light is on, indicating that the operating handle is in place; if the bus tie switch reaches the real closing state, the bus tie closing indicator light is on, indicating that the closing is successful and the maintenance personnel can carry out maintenance work; if the bus tie closing indicator light is not on, indicating that the bus tie switch has not yet reached the closing state, the maintenance personnel must check the bus tie switch and the operating handle to eliminate faults before continuing to work.

[0009] A DC bus tie switch position indication device based on AC signal injection comprises two groups of batteries, two sets of chargers and two sections of DC bus, wherein an AC signal is injected into one section of the DC bus; further comprising a handle position state indication circuit, wherein the handle position state indication circuit comprises a bus tie switch state indication circuit and an operating handle state indication circuit; when the operating handle is in a closed position, the bus tie switch is closed or opened, and the operating handle indicator lights are all on; when the bus tie switch is closed, the bus tie switch indicator lights are on; the AC signal is used to drive the bus tie switch state indication circuit and the operating handle state indication circuit to indicate the closing safety of the bus tie switch;

[0010] The bus tie switch state indication circuit includes a first capacitor, a first resistor, a second capacitor, and a third capacitor, a second resistor, a handle contact, a fourth capacitor, a first drive power supply and a filter circuit connected in series in sequence; wherein, one end of the first capacitor is connected to the first resistor, one end of the third capacitor is connected to the second resistor, and the other end of the first capacitor and the other end of the third capacitor are both connected to one section of the DC bus on both sides of the bus tie switch; the bus tie switch state indication circuit also includes a fifth capacitor, a third resistor, a sixth capacitor, and a bus tie switch indicator light connected in series in sequence; wherein, one end of the fifth capacitor is connected to the third resistor, and the other end of the fifth capacitor is connected to another section of the DC bus on both sides of the bus tie switch; one end of the filter circuit is connected to the first drive power supply, one end of the second capacitor is connected to the first resistor, one end of the bus tie switch indicator light is connected to the sixth capacitor, and the other end of the filter circuit is connected to the other end of the second capacitor and the other end of the bus tie switch indicator light.

[0011] Furthermore, the operating handle status indication circuit includes a photoelectric proximity switch, an operating handle indicator light, a second driving power supply, a fourth resistor and an operating handle contact excitation coil, and the photoelectric proximity switch, the operating handle indicator light, the second driving power supply, the fourth resistor and the operating handle contact excitation coil are connected in series to form a loop.

[0012] Furthermore, the AC signal injected into a section of the DC bus on both sides of the bus tie switch is a high-frequency low-voltage signal.

[0013] Furthermore, the filtering circuit is a bandpass filtering circuit: one end of the fifth resistor and one end of the sixth resistor are both connected to the negative input terminal of the amplifier, and one end of the fifth resistor is connected to one end of the sixth resistor, the other end of the fifth resistor is grounded, and the other end of the sixth resistor is connected to the output terminal of the amplifier; one end of the seventh resistor is connected to the input signal, the other end of the seventh resistor is connected to one end of the seventh capacitor and one end of the eighth capacitor, the other end of the eighth capacitor is connected to the positive input terminal of the amplifier and one end of the eighth resistor, the other end of the eighth resistor is grounded, and the other end of the seventh capacitor is connected to the output terminal of the amplifier.

[0014] The present invention has achieved the following technical effects:

[0015] 1. As long as the operating handle is in the closed position, regardless of the position of the DC bus tie switch, whether in the closed position or the open position, the photoelectric proximity switch in front of the operating handle will trigger the main circuit of the indicating device, and the operating handle indicator light will be on;

[0016] 2. If the bus tie switch is not closed to the correct position, or the closing is not tight, the contact resistance of the bus tie switch will increase or short-circuit, and the indicator light of the bus tie switch will not light up; if the indicator light of the operating handle of the indicating device is on but the indicator light of the bus tie switch is not on, it can be judged that the operating handle has failed or slipped and needs to be replaced or repaired;

[0017] 3. The filter circuit of the device ensures that the harmonics of the injected high-frequency signal on the DC bus are less than 0.1%;

[0018] 4. The device is installed on a DC bus of the DC system, and the access terminals are at the same potential, so there is no need to shut down the power during construction and there is no risk of electric shock.

[0019] 5. The device does not use DC system power and will not become a risk point after installation.

[0020] 6. The device has a compact structure and occupies little space, so there is enough space for installation in the current DC system cabinet. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A bus-coupled circuit diagram of a dual DC system in the prior art;

[0022] Figure 2 Functional principle diagram of the present invention;

[0023] Figure 3 The bus tie switch state indicating circuit of the present invention;

[0024] Figure 4The operating handle status indication circuit of the present invention;

[0025] Figure 5 The filter circuit of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0027] Figure 1 The figure shows a bus-coupled circuit diagram of a dual DC system in the prior art. The dual DC system is equipped with two sets of 110V or 220V DC systems: two sets of batteries, two sets of chargers, each with a section of DC bus. The two sections of DC bus are split and operated normally. When the DC system in one section is under maintenance, the two sections of DC bus are continuously powered by closing the DC bus-coupled switch. The dual DC system also includes two sets of balancing bridges, each of which includes two grounding resistors.

[0028] Figure 2 It is shown that the DC busbars on both sides of the bus tie switch are connected to a handle position status indication circuit, and an AC signal is injected into one section of the DC busbar. The handle position status indication circuit includes a bus tie switch status indication circuit and an operating handle status indication circuit; when the operating handle is in the closed position, the bus tie switch is closed or opened, and the operating handle indicator light is on; when the bus tie switch is closed, the bus tie switch indicator light is on. More importantly, as long as the operating handle is in the closed position, regardless of the position of the DC bus tie switch, whether it is in the closed position or the open position, the photoelectric proximity switch in front of the operating handle triggers the main circuit of the indicating device, and the operating handle indicator light is on; the AC signal is used to drive the bus tie switch status indication circuit and the operating handle status indication circuit to indicate the safety of the bus tie switch closing.

[0029] Use one end of the busbar in the DC circuit to connect the device on both sides of the bus tie switch.

[0030] Figure 3A bus tie switch state indication circuit is shown, the bus tie switch state indication circuit comprises a first capacitor C1, a first resistor R1, a second capacitor C2, and a third capacitor C3, a second resistor R2, a handle contact, a fourth capacitor C4, a first drive power supply U1 and a filter circuit which are connected in series in sequence; wherein one end of the first capacitor C1 is connected to the first resistor R1, one end of the third capacitor C3 is connected to the second resistor R2, and the other end of the first capacitor C1 and the other end of the third capacitor C3 are both connected to one section of the DC bus on both sides of the bus tie switch; the bus tie switch state indication circuit also comprises a fifth capacitor C5, a third resistor R3, a sixth capacitor C6, and a bus tie switch indicator light which are connected in series in sequence; wherein one end of the fifth capacitor C5 is connected to the third resistor R3, and the other end of the fifth capacitor C5 is connected to another section of the DC bus on both sides of the bus tie switch; one end of the filter circuit is connected to the first drive power supply, one end of the second capacitor C2 is connected to the first resistor R1, one end of the bus tie switch indicator light is connected to the sixth capacitor C6, and the other end of the filter circuit is connected to the other end of the second capacitor and the other end of the bus tie switch indicator light.

[0031] The first driving power source U1 is an AC signal, and the AC signal is injected into a section of the DC bus on both sides of the bus tie switch.

[0032] Figure 3 The bus tie switch status indication circuit in the bus tie switch is closed to form a loop after the operating handle contacts are triggered, and the bus tie closing indicator light is driven. In the circuit diagram, the main circuit is composed of a current limiting resistor R2, two high-voltage capacitors C3 and C4, and a filter circuit; the two branch circuits are composed of a resistor R1 and two high-voltage capacitors C1 and C2. The high-voltage capacitor acts as a separator between the indicating device and the DC system to ensure that the 110 / 220 volt DC voltage of the DC system will not be directly loaded onto the device to form a loop. Resistors R1 and R2 can limit the current generated by the AC signal, and can also limit the DC current when the capacitor fails and shorts.

[0033] Figure 4 A handle status indication circuit is shown, which includes a photoelectric proximity switch K, an operating handle indicator light, a second drive power supply U2, a fourth resistor R4 and an operating handle contact excitation coil L. The photoelectric proximity switch K, the operating handle indicator light, the second drive power supply U2, the fourth resistor R4 and the operating handle contact excitation coil L are connected in series to form a loop.

[0034] A reflective photoelectric proximity switch is installed next to the closing position on the panel cabinet. Once the operating handle reaches the closing position, the photoelectric switch detects the reflected signal, triggers the sensor to the on state, forms a loop for the handle position circuit, and the handle position indicator lights up; after the handle contact excitation coil conducts, the handle normally open contact of the busbar switch position indication circuit is triggered.

[0035] Figure 5 The structure of the filter circuit is shown, and the filter circuit is a bandpass filter circuit: one end of the fifth resistor R5 and one end of the sixth resistor R6 are both connected to the negative input terminal of the amplifier A, and one end of the fifth resistor R5 and one end of the sixth resistor R6 are connected, the other end of the fifth resistor R5 is grounded, and the other end of the sixth resistor R6 is connected to the output terminal of the amplifier A; one end of the seventh resistor R7 is connected to the input signal, the other end of the seventh resistor R7 is connected to one end of the seventh capacitor C7 and one end of the eighth capacitor C8, the other end of the eighth capacitor C8 is connected to the positive input terminal of the amplifier A and one end of the eighth resistor R8, the other end of the eighth resistor R8 is grounded, and the other end of the seventh capacitor C7 is connected to the output terminal of the amplifier A.

[0036] Figure 5 R7 and C7 in the circuit are low-pass filter circuits, which suppress frequencies lower than 1 / (2πR7C7); R8 and C8 are high-pass filter circuits, which suppress frequencies higher than 1 / (2πC8R8). This circuit has two functions: filtering the harmonics generated by the AC signal; suppressing the high-order harmonics generated by the arc ignition at the moment when the busbar switch is closed.

[0037] A withstand voltage capacitor is connected to both ends of each current suppression resistor of the indicating device of the present invention to cut off the direct current and prevent the device from forming a loop with the direct current system.

[0038] The filter circuit of the indicating device of the present invention filters high-frequency harmonics formed by voltage oscillation formed by a DC signal and an AC signal during the closing period.

[0039] If the main tie switch is not closed to the correct position or the closing position is not tight, the contact resistance of the main tie switch will increase or short-circuit, and the main tie switch closing indicator light will not light up; if the indicator light of the indicator device's operating handle in place is on but the main tie switch closing indicator light is not on, it can be determined that the operating handle has failed or slipped and needs to be replaced or repaired.

[0040] Furthermore, the AC signal injected into the DC busbars on both sides of the bus tie switch is a high-frequency low-voltage signal; the signal and transceiver circuit of the indicating device's transceiver are connected to the DC bus tie switch and the two-section DC system of the substation, and the visual auxiliary contacts of the DC bus tie switch operating handle are connected in series in this circuit, and the indicator light on the signal transceiver turns on or off to indicate the closed or open position of the DC bus tie switch and whether the operating handle is in the closed or open position.

[0041] As long as the operating handle is in the closed position, the photoelectric proximity switch in front of the handle triggers the main circuit of the indicating device, and the indicating device starts to power on to avoid the device working only when the main coupling switch is closed.

[0042] The indicating device of the present invention is installed on the screen where the operating handle is located. The position sensing of the operating handle uses the closed position of the reflective proximity switch. The proximity switch is adjusted to have an effective distance of 2cm to 10cm. When the busbar switch is closed to the closed position, the corresponding indicator light is on.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. After reading this application, technical personnel in the relevant field may make various modifications or changes to the present invention with reference to the above embodiments, which are all within the scope of protection claimed in the pending application of the present invention.

Claims

1. A DC bus switch position indicating device based on AC signal injection, comprising two groups of batteries, two sets of chargers and two sections of DC bus, characterized in that: An AC signal is injected into one section of the DC bus; a handle position state indication circuit is also included, and the handle position state indication circuit includes a bus tie switch state indication circuit and an operating handle state indication circuit; when the operating handle is in the closed position, the bus tie switch is closed or opened, and the operating handle indicator lights are all on; when the bus tie switch is closed, the bus tie switch indicator light is on; the AC signal is used to drive the bus tie switch state indication circuit and the operating handle state indication circuit to indicate the safety of closing the bus tie switch; The bus tie switch state indication circuit includes a first capacitor, a first resistor, a second capacitor, and a third capacitor, a second resistor, a handle contact, a fourth capacitor, a first drive power supply and a filter circuit connected in series in sequence; wherein, one end of the first capacitor is connected to the first resistor, one end of the third capacitor is connected to the second resistor, and the other end of the first capacitor and the other end of the third capacitor are both connected to one section of the DC bus on both sides of the bus tie switch; the bus tie switch state indication circuit also includes a fifth capacitor, a third resistor, a sixth capacitor, and a bus tie switch indicator light connected in series in sequence; wherein, one end of the fifth capacitor is connected to the third resistor, and the other end of the fifth capacitor is connected to another section of the DC bus on both sides of the bus tie switch; one end of the filter circuit is connected to the first drive power supply, one end of the second capacitor is connected to the first resistor, one end of the bus tie switch indicator light is connected to the sixth capacitor, and the other end of the filter circuit is connected to the other end of the second capacitor and the other end of the bus tie switch indicator light.

2. The indicating device according to claim 1, characterized in that: The operating handle state indication circuit includes a photoelectric proximity switch, an operating handle indicator light, a second driving power supply, a fourth resistor and an operating handle contact excitation coil. The photoelectric proximity switch, the operating handle indicator light, the second driving power supply, the fourth resistor and the operating handle contact excitation coil are connected in series to form a loop.

3. The indicating device according to claim 1 or 2, characterized in that: The AC signal injected into a section of the DC busbar on both sides of the bus tie switch is a high-frequency low-voltage signal.

4. The indicating device according to claim 1, characterized in that: The filtering circuit is a bandpass filtering circuit: one end of the fifth resistor and one end of the sixth resistor are both connected to the negative input terminal of the amplifier, and one end of the fifth resistor is connected to one end of the sixth resistor, the other end of the fifth resistor is grounded, and the other end of the sixth resistor is connected to the output terminal of the amplifier; one end of the seventh resistor is connected to the input signal, the other end of the seventh resistor is connected to one end of the seventh capacitor and one end of the eighth capacitor, the other end of the eighth capacitor is connected to the positive input terminal of the amplifier and one end of the eighth resistor, the other end of the eighth resistor is grounded, and the other end of the seventh capacitor is connected to the output terminal of the amplifier.

Images