Low-voltage switch cabinet fault on-line monitoring device

Abstract

A kind of low-voltage switch cabinet fault on-line monitoring device, including existing switch cabinet in isolating switch, circuit breaker, contactor, current transformer and voltage relay, intermediate relay, current limiting resistor and signal acquisition operator composition, through the voltage, current measurement of low-voltage switch cabinet, timely on-line judgment circuit breaker, contactor, connecting joint contact state, avoids the problem that off-line test cannot find that circuit breaker closing is not in place and other circuit breaker loop resistance abnormalities;Comparison using existing equipment can realize all-weather on-line monitoring, timely sensing low-voltage switch cabinet loop resistance abnormal change trend, timely find defects hidden danger, avoid defect to develop into serious fault.The principle of the present application is simple and effective, a kind of low-cost effective method for all-weather on-line monitoring of low-voltage switch cabinet exception.

Description

Technical Field

[0001] This application belongs to the field of switchgear fault monitoring and relates to an online fault monitoring device for low-voltage switchgear. Background Technology

[0002] Low-voltage switchgear, used for power transmission, distribution, and energy conversion, is a crucial component of the power system and one of the most widely used pieces of equipment. Inadequate quality control during manufacturing and on-site installation can lead to poor contact at joints and switch contacts, and increased circuit resistance. While this may not cause serious problems at low load currents, as the load current increases, the heat generated at poorly contacted areas will rapidly worsen the defects, ultimately leading to insulation damage and short-circuit accidents. Parts like circuit breakers and contactors, where contacts are sealed and cannot be observed during normal operation or have their contact temperature measured using infrared thermography, are particularly prone to faults. Traditional testing methods involve periodic power outages, which have long testing cycles and are difficult to detect defects in a timely manner. Furthermore, power outage tests deviate from actual operating conditions, failing to comprehensively detect potential faults. Additionally, power outage testing can disrupt normal power supply. Therefore, effective online monitoring of low-voltage switchgear faults and early detection of potential problems can improve the safety of the power supply system and reduce losses caused by power system failures and unplanned outages. Summary of the Invention

[0003] The purpose of this application is to provide an online fault monitoring device for low-voltage switchgear, comprising an disconnector, circuit breaker, contactor, current transformer, voltage relay, intermediate relay, current-limiting resistor, and signal acquisition and processing unit within the existing switchgear. The input terminal of the disconnector is connected to the power grid, the output terminal of the disconnector is connected to the input terminal of the circuit breaker, the output terminal of the circuit breaker is connected to the input terminal of the contactor, the output terminal of the contactor is connected to the load via the primary side of the current transformer in series, one end of the voltage relay coil is connected to the output terminal of the disconnector, and the other end of the voltage relay coil is connected to the in-phase terminal of the contactor output terminal via the current-limiting resistor. The normally open contact of the voltage relay is connected in series between the intermediate relay coil and the power supply. The secondary side of the current transformer is connected to the current signal terminal of the signal acquisition and processing unit according to the phase sequence. The input voltage signal terminal of the signal acquisition and processing unit is connected to the input terminal of the circuit breaker via the normally closed contacts of the intermediate relays, and the output voltage signal terminal of the signal acquisition and processing unit is connected to the output terminal of the contactor via the normally closed contacts of the intermediate relays.

[0004] Compared with existing technologies, this application provides an online fault monitoring device for low-voltage switchgear. By measuring the voltage and current of the low-voltage switchgear, it can promptly determine the contact status of circuit breakers, contactors, and connecting joints online, avoiding the problem that offline testing cannot detect abnormal circuit breaker circuit resistance, such as incomplete circuit breaker closing. By comparing with existing equipment, it can achieve 24 / 7 online monitoring, promptly detect abnormal changes in the low-voltage switchgear circuit resistance, identify potential defects in a timely manner, and prevent defects from developing into serious faults. This application is simple and effective in principle, providing a low-cost and efficient method for 24 / 7 online monitoring of abnormalities in low-voltage switchgear. Attached Figure Description

[0005] The accompanying drawings, which are included to provide a further understanding of the embodiments of the present invention and form part of this application, do not constitute a limitation on the embodiments of the present invention. In the drawings: Figure 1 This is a single-line schematic diagram provided in Embodiment 1 of this application; Figure 2 This is a single-line schematic diagram provided for Embodiment 2 of this application; Figure 3 This is a single-line schematic diagram provided for Embodiment 3 of this application. Detailed Implementation

[0006] In the following, the terms “comprising” or “may include” as used in various embodiments of this application indicate the presence of the claimed function, operation, or element, and do not limit the addition of one or more functions, operations, or elements. Furthermore, as used in various embodiments of this application, the terms “comprising,” “having,” and their cognates are intended only to indicate a specific feature, number, step, operation, element, component, or combination of the foregoing, and should not be construed as primarily excluding the presence of one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing, or the possibility of adding one or more combinations of the foregoing.

[0007] In various embodiments of this application, the expression "or" or "at least one of B and / or C" includes any combination or all combinations of the words listed simultaneously. For example, the expression "B or C" or "at least one of B and / or C" may include B, may include C, or may include both B and C.

[0008] The terms used in the various embodiments of this application (such as "first," "second," etc.) may modify various constituent elements in the various embodiments, but do not limit the corresponding constituent elements. For example, the above terms do not limit the order and / or importance of the elements. The above terms are only used for the purpose of distinguishing one element from other elements. For example, a first user device and a second user device refer to different user devices, although both are user devices. For example, without departing from the scope of the various embodiments of this application, a first element may be referred to as a second element, and similarly, a second element may also be referred to as a first element.

[0009] It should be noted that if a description refers to "connecting" a component to or "connecting" to another component, then the first component can be directly connected to the second component, and a third component can be "connected" between the first and second components. Conversely, when a component is "directly connected" to or "directly connected" to another component, it can be understood that there is no third component between the first and second components.

[0010] The terminology used in the various embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the various embodiments of this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which the various embodiments of this application pertain. The terms (such as those defined in a generally used dictionary) are to be interpreted as having the same meaning as in the context of the relevant technical field and are not to be interpreted as having an idealized or overly formal meaning, unless clearly defined in the various embodiments of this application.

[0011] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this application are only for explaining this application and are not intended to limit this application.

[0012] Referring to the accompanying drawings and embodiments, this application discloses an online fault monitoring device for low-voltage switchgear, comprising an disconnector switch QS, a circuit breaker QF, a contactor KM, a current transformer TA, a voltage relay KV, an intermediate relay KA, a current-limiting resistor R, and a signal acquisition and processing unit CR within an existing switchgear. The device is characterized in that: the input terminal of the disconnector switch QS is connected to the power grid; the output terminal of the disconnector switch QS is connected to the input terminal of the circuit breaker QF; the output terminal of the circuit breaker QF is connected to the input terminal of the contactor KM; the output terminal of the contactor KM is connected in series with the primary side of the current transformer TA and then connected to the load; one end of the coil of the voltage relay KV is connected to the input terminal of the circuit breaker QF; and the voltage relay KV coil… The other end is connected to the in-phase terminal of the contactor KM output via the current-limiting resistor R. The normally open contact of the voltage relay KV is connected in series between the coil of the intermediate relay KA and the power supply. The secondary side of the current transformer TA is connected to the corresponding current signal terminals of the signal acquisition and processing unit CR according to the phase sequence. The input voltage signal terminals 1Va, 1Vb, 1Vc, and 1Vn of the signal acquisition and processing unit CR are connected to the input terminals A, B, C, and N of the circuit breaker via the normally closed contact of the intermediate relay KA. The output voltage signal terminals 2Va, 2Vb, 2Vc, and 2Vn of the signal acquisition and processing unit CR are connected to the output terminals A, B, C, and N of the contactor KM via the normally closed contact of the intermediate relay KA.

[0013] During operation, when the isolating switch QS is closed and the circuit breaker QF and contactor KM are not closed, the potential difference between the input terminal of circuit breaker QF and the output terminal of contactor KM is high. Voltage relay KV closes through current-limiting resistor R, and intermediate relay KA is energized, disconnecting the signal acquisition and processing unit CR from the voltage signal acquisition circuit of the main circuit. When circuit breaker QF and contactor KM are closed, the potential difference between the input terminal of circuit breaker QF and the output terminal of contactor KM decreases, voltage relay KV releases due to undervoltage, the coil of intermediate relay KA is de-energized, and the signal acquisition and processing unit CR is connected to the voltage signal acquisition circuits of each phase of the main circuit via the normally closed contact of intermediate relay KA. The signal acquisition and processing unit CR then begins to operate, monitoring and calculating the circuit resistance through the following steps: S1, collects the current signals of each phase of the current transformer, namely I A I B I C、 I n ; S2, acquire the phase voltage signals at the QF input terminal of the circuit breaker, which are V 1A V 1B V 1C V 1n ; S3, collects the current signals of each phase at the output terminal of contactor KM, which are I 2A I 2B I 2C I2n ; S4. Calculate the measured circuit resistance of the distribution cabinet based on the collected phase current signals, phase voltage signals at the input of the circuit breaker QF, and phase voltage signals at the output of the contactor KM. Phase A: R A = (V 1A —V 2A ) / I 1A Phase B: R B = (V 1B —V 2B ) / I 1B C phase: R C = (V 1C —V 2C ) / I 1C N:R n = (V 1n —V 2n ) / I 1n The signal acquisition and processing unit CR is equipped with an LCD control display screen, an audible and visual alarm, an internal memory, and a communication interface. It displays the monitored loop resistance in real time, and can issue an alarm according to the set alarm threshold. The display and alarm information are recorded in the memory and can be retrieved at any time for manual judgment of the cable's operating status and timely correction of the threshold.

[0014] The actual threshold should be set according to the specific project and user needs to balance the requirements of sensitivity and reliability.

Claims

1. A low-voltage switchgear fault online monitoring device, comprising an existing switchgear containing a disconnector (QS), circuit breaker (QF), contactor (KM), current transformer (TA), voltage relay (KV), intermediate relay (KA), current limiting resistor (R), and signal acquisition and processing unit (CR), characterized in that: The input terminal of the disconnecting switch (QS) is connected to the power grid, and the output terminal of the disconnecting switch (QS) is connected to the input terminal of the circuit breaker (QF). The output terminal of the circuit breaker (QF) is connected to the input terminal of the contactor (KM). The output terminal of the contactor (KM) is connected in series with the primary side of the current transformer (TA) and then connected to the load. One end of the coil of the voltage relay (KV) is connected to the input terminal of the circuit breaker (QS), and the other end of the coil of the voltage relay (KV) is connected to the in-phase terminal of the output terminal of the contactor (KM) via a current-limiting resistor (R). The normally open contact of the voltage relay (KV) is connected in series between the coil of the intermediate relay (KA) and the power supply. The secondary side of the current transformer (TA) is connected to the corresponding current signal terminal of the signal acquisition and processing unit (CR). The input voltage signal terminals of the signal acquisition and processing unit (CR) are connected to the input terminal of the circuit breaker (QF) via the normally closed contact of the intermediate relay (KA), and the output voltage signal terminals of the signal acquisition and processing unit (CR) are connected to the output terminal of the contactor (KM) via the normally closed contact of the intermediate relay (KA).

2. The online fault monitoring device for low-voltage switchgear according to claim 1, characterized in that: The signal acquisition and processing unit (CR) is equipped with an LCD control display screen, an audible and visual alarm, an internal memory, and a communication interface.

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