An improved phase failure protection device for circuit breakers

Abstract

This utility model relates to an improved circuit breaker phase loss protection device, comprising three intermediate relays KA1, KA2, and KA3, each connected between any two phases of a three-phase power grid, and each intermediate relay protected by a fuse; it also includes three audible and visual alarms HA1, HA2, and HA3, and a UPS uninterruptible power supply; the normally open contacts of the three intermediate relays are connected in series with the undervoltage trip coil Q of the circuit breaker, forming a new undervoltage control circuit. This utility model is technically sound and reliable, with a high reliability rate. It solves the problem that the undervoltage trip of the circuit breaker on the low-voltage side may fail to operate when one phase on the high-voltage side of the main transformer is missing, ensuring that the circuit breaker on the low-voltage side can reliably trip even if any phase on the high-voltage side is missing. This is of great significance for the timely disconnection of low-voltage equipment from the faulty power grid to prevent damage.

Description

Technical Field

[0001] This utility model relates to the field of circuit breaker technology, and in particular to an improved device for phase loss protection of circuit breakers. Background Technology

[0002] Currently, in 10kV power distribution systems, the high-voltage side of transformers commonly uses a combination of load switch and fuse for protection. This combination provides overload and short-circuit protection but lacks undervoltage protection. The low-voltage side main switch typically uses a universal circuit breaker, which, in addition to overload, short-circuit, and single-phase grounding protection, also provides undervoltage protection. However, this undervoltage protection is incomplete; it cannot guarantee that the universal circuit breaker will trip in case of any phase loss, leading to delayed disconnection of line faults and potentially escalating electrical accidents.

[0003] Taking the commonly used universal circuit breaker TGW45-1000 / 3 as an example, according to the product manual, the control wiring diagram (partial) of this universal circuit breaker is as follows: Figure 1 .

[0004] from Figure 1 As can be seen from the diagram, the two ends of the undervoltage coil of the universal circuit breaker TGW45-1000 / 3 are connected to the phase line and the neutral line respectively, and the working voltage is 230V. The undervoltage trip will only be activated when the voltage of the undervoltage coil drops to (35%~70%)Ue. However, in a 10kV power distribution system, taking the common Dyn11 type distribution transformer as an example, when a phase is missing on the high-voltage side, the voltage change reflected on the low-voltage side can be calculated using the symmetrical component method. If phase A on the high-voltage side of the transformer is missing, the voltage on the low-voltage side of the transformer is Ub=230V, Ua=Uc=115V, Uab=Ubc=350V, and Uca=0. If phase B is missing, the voltage reflected on the low-voltage side is Uc=230V, Ua=Ub=115V, Ubc=Uca=350V, and Uab=0. If phase C is missing, the voltage reflected on the low-voltage side is Ua=230V, Ub=Uc=115V, Uab=Uca=350V, and Ubc=0[1]. It can be seen that when a phase is missing on the high-voltage side, the phase voltage of the phase lagging phase remains unchanged, while the phase voltage of the other two phases drops to half.

[0005] The above analysis shows that in the event of a phase loss on a 10kV line, the voltage of the undervoltage release coil of the universal circuit breaker on the low-voltage side of the transformer does not necessarily decrease, thus triggering the undervoltage protection. For example, assuming the undervoltage release coil of the universal circuit breaker is connected to phase A, when phase A or B of the 10kV line is lost, the voltage of the undervoltage release coil drops to 115V, triggering the undervoltage protection. However, if phase C of the 10kV line is lost, the voltage of the undervoltage release coil remains unchanged at 230V, and the undervoltage protection does not activate. This is a common deficiency in the undervoltage protection function of current 10kV power distribution systems. Utility Model Content

[0006] This utility model proposes an improved circuit breaker phase loss protection device to solve the problems mentioned in the prior art.

[0007] To achieve the above objectives, this utility model provides the following technical solution:

[0008] An improved circuit breaker phase loss protection device includes three intermediate relays KA1, KA2, and KA3, each of which is connected between any two phases of a three-phase power grid and is protected by a fuse. It also includes three audible and visual alarms HA1, HA2, and HA3, and a UPS uninterruptible power supply. The normally open contacts of the three intermediate relays are connected in series with the undervoltage trip coil Q of the circuit breaker to form a new undervoltage control circuit. The normally closed contacts of the three intermediate relays are connected in parallel with the three audible and visual alarms, powered by the UPS, to form a phase loss alarm circuit.

[0009] As a further technical solution of this utility model: the intermediate relay is a small 380VAC electromagnetic relay.

[0010] As a further technical solution of this utility model: the sound and light alarm is composed of LED beads and a piezoelectric buzzer.

[0011] As a further technical solution of this utility model: the AC input of the UPS uninterruptible power supply can be any one phase of the three-phase power grid, and the output voltage of 220V is used to power three branches. Each branch consists of a normally closed contact of an intermediate relay and an audible and visual alarm.

[0012] As a further technical solution of this utility model: when the external power grid supply is normal, the three intermediate relays are energized, the normally open contacts are closed, the undervoltage control circuit is energized, and the circuit breaker works normally; when a phase loss occurs on the high-voltage side, among the three-phase line voltages on the low-voltage side, except for two that are slightly reduced, the other drops to 0. The intermediate relay connected between the two phase lines with the line voltage of 0 releases quickly, the normally open contacts open, the undervoltage control circuit is de-energized, and the circuit breaker trips.

[0013] As a further technical solution of this utility model: when a phase loss occurs on the high-voltage side, the corresponding intermediate relay is released, its normally closed contact closes, and the audible and visual alarm is activated to issue an alarm signal.

[0014] The technical effects and advantages provided by this utility model in the above technical solution are as follows:

[0015] This utility model is technologically sound and reliable, with a high guarantee rate. It solves the problem that the low-voltage side circuit breaker may fail to trip when one phase on the high-voltage side of the main transformer is missing. It ensures that the low-voltage side circuit breaker can reliably trip even if any phase on the high-voltage side is missing, which is of great significance for the timely disconnection of low-voltage equipment from the faulty power grid to prevent damage. At the same time, because the power consumption of the circuit breaker's undervoltage trip unit is only 40VA and the current is very small, a 3A relay contact capacity is sufficient. The audible and visual alarm in the alarm circuit uses a combination of LED beads and piezoelectric buzzers, with a power consumption of less than 10W. The UPS uninterruptible power supply can be a low-power integrated product. With three fuses, the budget does not exceed 500 yuan, which greatly saves costs. Moreover, the installation is simple and convenient.

[0016] Water conservancy projects are often located in remote areas, and many rely on 10kV overhead power lines for power supply. A large number of small and medium-sized water conservancy projects use asynchronous motors as their primary power source. If a phase is missing in the power supply, the motor may malfunction or even burn out, causing gates to fail to open and close properly. This severely impacts flood discharge and water diversion safety, and can even lead to personal injury accidents. This utility model addresses this critical issue by significantly improving the safety protection functions of the power distribution system, effectively ensuring the safe operation of the project, and fully realizing its flood control and disaster reduction benefits. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is the control wiring diagram for the universal circuit breaker TGW45-1000 / 3.

[0019] Figure 2 This is the wiring diagram for phase loss protection alarm control. Detailed Implementation

[0020] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0021] It should be noted that the terms "vertical," "horizontal," "up," "down," "left," "right," and similar expressions used in this article are for illustrative purposes only and do not represent the only possible implementation.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention; the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0023] like Figure 2 As shown, this utility model provides an improved circuit breaker phase loss protection device, which mainly utilizes 3 intermediate relays, 3 audible and visual alarms, and a UPS uninterruptible power supply to carry out technical transformation of the undervoltage control of the universal circuit breaker (hereinafter referred to as the circuit breaker), so as to realize the function of timely disconnecting the faulty line and issuing an alarm.

[0024] First, promptly disconnect the faulty function. As analyzed above, when a phase loss occurs on the high-voltage side, the line voltage on the low-voltage side changes systematically, in addition to the phase voltage showing a regular change: if phase A on the high-voltage side is lost, then on the low-voltage side, Uab=Ubc=350V, Uca=0; if phase B is lost, it is reflected on the low-voltage side as Ubc=Uca=350V, Uab=0; if phase C is lost, it is reflected on the low-voltage side as Uab=Uca=350V, Ubc=0. Therefore, when a phase loss occurs on the high-voltage side of the main transformer, the three-phase line voltages on the low-voltage side will decrease slightly for two phases, while the third phase will drop to 0.

[0025] This utility model uses a common small 380AC electromagnetic relay as the intermediate relay. The control wiring diagram is shown below. Figure 2 In the left half, the coil of intermediate relay KA1 is connected between phases A and B, the coil of KA2 is connected between phases B and C, and the coil of KA3 is connected between phases C and A. All three intermediate relay coils are protected by fuse FU. One pair of normally open contacts from each of the three intermediate relays is connected in series with the undervoltage trip coil of the circuit breaker to form a new undervoltage control circuit. When the external power grid supply is normal, all three intermediate relays are energized, their normally open contacts close, the undervoltage control circuit is energized, and the undervoltage trip device is energized, generating sufficient suction to lock the circuit breaker's mechanical mechanism. The main contacts of the circuit breaker normally open and close. When a phase loss occurs on the high-voltage side of the main transformer, as mentioned earlier, the three-phase line voltages on the low-voltage side of the main transformer drop to 0, except for two that decrease slightly. The intermediate relay whose coil is connected between the two phases with zero line voltage quickly releases, the previously closed contacts open again, the undervoltage control circuit is de-energized, the undervoltage trip device loses power and its suction disappears, the mechanical mechanism unlocks, and the circuit breaker's main contacts break.

[0026] Second, alarm function. See the control wiring diagram. Figure 2The right half uses UPS power supply. The UPS AC input can be any one of phases A, B, or C, and the 220V output is connected to three branches. Each branch consists of a normally closed contact of an intermediate relay and an audible and visual alarm. As analyzed earlier, when the external power grid supply is normal, all three intermediate relays are energized, and their normally closed contacts open. When a phase loss occurs on the high-voltage side of the main transformer, as mentioned earlier, the intermediate relay connected between the two phase lines with zero line voltage quickly releases, the previously open contacts close again, the branch is connected, and the audible and visual alarm sounds, alerting the operating personnel to the high-voltage side phase loss fault. Furthermore, the operating personnel can determine which phase is missing based on the activated alarm. Moreover, the audible and visual alarm can be customized with a specific alarm voice to directly announce the phase loss.

[0027] In summary, this utility model is a reasonable and reliable technology with a high reliability. It solves the problem that the low-voltage side circuit breaker may not trip when one phase on the high-voltage side of the main transformer is missing, ensuring that the low-voltage side circuit breaker can reliably trip even if any phase on the high-voltage side is missing. This is of great significance for the timely disconnection of low-voltage equipment from the faulty power grid to prevent damage. Furthermore, because the circuit breaker's undervoltage trip unit consumes only 40VA and has a very small current, a 3A relay contact capacity is sufficient. The alarm circuit uses an LED light bulb + piezoelectric buzzer combination, consuming less than 10W. The UPS uninterruptible power supply can be a low-power integrated product. With three fuses, the budget is less than 500 yuan, significantly saving costs. Moreover, installation is simple and convenient.

[0028] Water conservancy projects are often located in remote areas, and many rely on 1010kV overhead power lines for power supply. A large number of small and medium-sized water conservancy projects use asynchronous motors as their primary power source. If these motors malfunction or burn out due to a phase loss, gates will be unable to open and close properly, severely impacting flood discharge and water diversion safety, or even causing personal injury accidents. This utility model addresses this critical issue by significantly improving the safety protection functions of the power distribution system, effectively ensuring the safe operation of the project, and fully realizing its flood control and disaster reduction benefits.

[0029] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of this invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this invention.

[0030] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style of the specification is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment have been appropriately combined to form other embodiments that are easily understood by those skilled in the art.

Claims

1. An improved circuit breaker phase loss protection device, comprising three intermediate relays KA1, KA2 and KA3, characterized in that, Each intermediate relay is connected between any two phases of the three-phase power grid, and each intermediate relay is protected by a fuse; it also includes three audible and visual alarms HA1, HA2, and HA3 and one UPS uninterruptible power supply; the normally open contacts of the three intermediate relays are connected in series with the undervoltage trip coil Q of the circuit breaker to form a new undervoltage control circuit; the normally closed contacts of the three intermediate relays are connected in parallel with the three audible and visual alarms, which are powered by the UPS uninterruptible power supply to form a phase loss alarm circuit.

2. The improved circuit breaker phase loss protection device according to claim 1, characterized in that: The intermediate relay is a small 380VAC electromagnetic relay.

3. The improved circuit breaker phase loss protection device according to claim 2, characterized in that: The sound and light alarm is composed of LED beads and a piezoelectric buzzer.

4. The improved circuit breaker phase loss protection device according to claim 1, characterized in that: The UPS uninterruptible power supply can take any one phase of the three-phase power grid as its AC input and output 220V voltage to power three branches. Each branch consists of a normally closed contact of an intermediate relay and an audible and visual alarm.

5. The improved circuit breaker phase loss protection device according to claim 4, characterized in that: When the external power grid supply is normal, the three intermediate relays are energized, the normally open contacts close, the undervoltage control circuit is energized, and the circuit breaker operates normally. When a phase loss occurs on the high-voltage side, of the three phase line voltages on the low-voltage side, two are slightly reduced, while the other drops to 0. The intermediate relay connected between the two phase lines with 0 line voltage quickly releases, the normally open contacts open, the undervoltage control circuit is de-energized, and the circuit breaker trips.

6. The improved circuit breaker phase loss protection device according to claim 1, characterized in that: When a phase loss occurs on the high-voltage side, the corresponding intermediate relay is released, its normally closed contact closes, and the audible and visual alarm is activated, sending an alarm signal.

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