Distribution line isolation compensation device
By installing isolation compensation devices in power distribution lines and using coupling windings for fault identification and voltage compensation, the problem of insufficient transition resistance identification in existing devices is solved, enabling rapid elimination of arc discharge and stable operation.
Patent Information
- Application Number
- CN202520115221.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-17
- Publication Date
- 2026-01-23
- Estimated Expiration
- 2035-01-17
AI Technical Summary
Existing active grounding fault compensation devices cannot effectively identify transient and permanent faults, especially lacking the ability to identify transition resistance, which leads to system instability, inability to quickly eliminate arc discharge, and the risk of electric shock to personnel.
Design a power distribution line isolation compensation device, which forms a local isolation system between the system bus and the protection line, and uses coupled primary winding, load winding and compensation winding to perform fault identification and full compensation of voltage and current, improves the transition resistance identification capability, and injects reverse voltage into the faulty phase to eliminate arc discharge.
It enables rapid identification and full compensation of single-phase grounding faults, improves the ability to identify broken wires, avoids the dangers of arc discharge and electric shock, and reduces system operating costs and equipment maintenance complexity.
Smart Images
Figure CN223829024U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the technical field of single-phase grounding protection devices for power distribution networks, and in particular to a power distribution line isolation compensation device. Background Technology
[0002] In 6-66kV power systems, single-phase grounding faults account for more than 80% of all faults, and the grounding current is mainly capacitive current. In order to prevent excessive capacitive current from causing grounding arcs that break down equipment insulation and cause power outages, arc suppression measures should be taken in a timely manner to promote the recovery of transient faults and curb the deterioration of permanent faults. Furthermore, the effective handling of single-phase grounding faults plays a crucial role in preventing wildfires caused by arcs and accidents such as casualties caused by broken wires and grounding.
[0003] Most existing active ground fault compensation devices consist of power transformers, step-up transformers, vacuum contactors, active power compensators, controllers, etc. They can compensate the voltage and current at the single-phase ground fault point to near zero and completely eliminate arcing when a single-phase ground fault occurs, making them the optimal solution for solving single-phase ground faults.
[0004] However, in actual operation, single-phase grounding faults in distribution networks are mainly transient, and the arc suppression process changes the transition resistance as the fault recovers. Therefore, if a transient fault recovers, timely disengagement of the arc suppression coil from full compensation can effectively prevent the system from operating in a resonant overvoltage state; while for permanent faults, the arc suppression coil should maintain full compensation arc suppression to prevent the fault from worsening. Thus, the key to the scientific activation and deactivation of full compensation for arc suppression coils lies in quickly identifying the grounding resistance to determine the type of grounding fault.
[0005] Because the initial fault transition resistance of grounding failures and wildfires caused by electric arcs is often very large, reaching 50kΩ or even exceeding 100kΩ, while the existing active full compensation device for grounding faults can only identify the transition resistance of grounding faults at around 10kΩ, it cannot adapt to the impact of rapid compensation by the arc suppression coil on fault information, and the real-time performance of transition resistance identification is also poor; therefore, it cannot meet the requirements for stable system operation. Utility Model Content
[0006] The technical problem to be solved by this utility model is to provide a power distribution line isolation compensation device to achieve isolation between the protection line and the original system when a single-phase ground fault occurs. It also provides full compensation for the voltage and current at the fault point by injecting a reverse voltage into the local isolation system of the isolated protection line, thereby improving the ability to identify broken wires, eliminating arc discharge as soon as possible, and avoiding the occurrence of electric shock hazards.
[0007] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows.
[0008] A power distribution line isolation and compensation device is provided. The isolation and compensation device is connected between the system bus and the protection line to isolate and compensate the protection line when a single-phase ground fault occurs. The isolation and compensation device includes a primary winding, a load winding and a compensation winding coupled to each other. The primary winding is connected to each phase of the system bus; the load winding is connected to each phase of the protection line to supply power to the power distribution equipment of the protection line; the compensation winding has the opposite polarity to the load winding and is grounded at its neutral point.
[0009] Preferably, the load winding and compensation winding of the isolation compensation device are both star-connected, and the three-phase output terminals of the compensation winding are respectively connected to one end of three single-phase switches; the other ends of the three single-phase switches are short-circuited to each other and then connected to the neutral point of the load winding.
[0010] Preferably, the turns ratio of the primary winding to the load winding and the primary winding to the compensation winding are both 1:1.
[0011] Preferably, the capacity of the load winding is matched with the total load of the local isolation system of the protection line, the capacity of the primary winding and the load winding are equal, and the capacity of the compensation winding is not less than the capacitive current compensation capacity of the local isolation system of the protection line.
[0012] The technological advancements achieved by this utility model are as follows, due to the adoption of the above technical solutions.
[0013] The isolation compensation device of this utility model can isolate the protected line from the original power distribution system when a single-phase ground fault occurs. A local isolation system is formed between the isolation compensation device and the protected line. The ground capacitance of this local isolation system is only one percent or even a fraction of one percent of the ground capacitance of the original system. Line identification is performed according to the same displacement voltage threshold. Compared with the resonant grounding method with the best sensitivity in traditional technology, the identification capability of the transition resistance is improved by 20 times or more, which greatly improves the line breakage identification capability. At the same time, after the single-phase switch of the faulty phase corresponding to the single-phase ground fault is closed, the reverse voltage of the faulty phase voltage is injected into the isolated local isolation system of the protected line, so that the voltage of that phase line to ground becomes "zero" volts, realizing the full compensation of the voltage and current of the fault point, quickly eliminating arc discharge, and avoiding the danger of electric shock to personnel. Attached Figure Description
[0014] Figure 1 This is a schematic diagram of the power distribution line system described in this utility model;
[0015] Figure 2 This is a voltage vector diagram of the system under a single-phase ground fault as described in this utility model.
[0016] Wherein: P. Primary winding, SL. Load winding, SC. Compensation winding. Detailed Implementation
[0017] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.
[0018] A power distribution line isolation compensation device is connected between the system busbar and the protected line, forming a local isolation system for the protected line. The isolation compensation device isolates the protected line from the original system and can compensate for the local isolation system in the event of a single-phase ground fault. The power distribution line system schematic diagram is shown below. Figure 1 As shown in the figure, the device within the dashed box is the isolation compensation device.
[0019] In this invention, the isolation compensation device includes a primary winding P, a load winding LS, and a compensation winding SC that are coupled together, as well as three single-phase switches K respectively disposed on the three-phase output terminals of the compensation winding SC. A K B and K C .
[0020] Among them, the primary winding P is a delta-connected or star-connected structure, and it is connected to each phase A of the system busbar. s B s C s Connect them separately; the system bus capacitance to ground is C respectively. OAS C OBS C OCS .
[0021] The load winding LS has a star connection structure and is connected to each phase A, B, and C of the protection line to supply power to the various power distribution equipment connected to the protection line. The protection line can be an overhead line that crosses forest areas, grasslands, or densely populated areas, etc., which are key areas for protection.
[0022] The compensating winding SC has a star connection, with polarity opposite to that of the load winding LS, and its neutral point is grounded. The three-phase output terminals of the compensating winding SC are connected to one end of each of three single-phase switches, i.e., the A-phase output terminal of the compensating winding SC is connected to single-phase switch K. A One end is connected to the other, and the B-phase output terminal of the compensation winding SC is connected to the single-phase switch K. B One end is connected to the C-phase output terminal of the compensation winding SC and the single-phase switch K. C One end of each single-phase switch is connected to the other end of the three single-phase switches; the other ends of the three single-phase switches are short-circuited to each other and then connected to the neutral point of the load winding LS.
[0023] In this invention, to ensure that the compensation winding can fully compensate the load system, the turns ratio of the primary winding P to the load winding LS and the primary winding P to the compensation winding SC of the isolation compensation device are both 1:1.
[0024] Regarding capacity settings, the capacity of the load winding LS should match the total load carried by the local isolation system of the protection line. Of course, it can also be 1.0 to 1.5 times depending on the subsequent load capacity increase. The capacity of the primary winding P and the load winding LS should be equal. The capacity of the compensation winding SC should not be less than the capacitor current compensation capacity of the local isolation system of the protection line.
[0025] The specific method of this utility model for isolating and compensating a protective line when a single-phase ground fault occurs in the protective line includes the following steps:
[0026] S1. An isolation compensation device is installed between the system busbar and the protection line to form a local isolation system for the protection line between the isolation compensation device and the protection line. The isolation compensation device achieves isolation of the protection line.
[0027] S2. When a single-phase ground fault occurs in the protected line, the isolation compensation device identifies the ground fault and the broken line.
[0028] The identification of single-phase ground faults mainly uses zero-sequence voltage. U 0 Exceeding the limit is the criterion. U 0 The calculation formula is:
[0029] (1)
[0030] In the formula: U 0 —Displacement voltage of the system during a ground fault;
[0031] E A —Power supply voltage of phase A (assuming it is a faulty phase);
[0032] C 0 —System single-phase ground capacitance;
[0033] R f —Grounding transition resistance.
[0034] As can be seen from equation (1), when a single-phase ground fault occurs, the displacement voltage is inversely proportional to the system's capacitance to ground.
[0035] In this invention, the isolation compensation device isolates the overhead line under key protection from the original power distribution system, forming a local isolation system between the isolation compensation device and the protected line. The ground capacitance C of this local isolation system is... OA C OB C OCIt is only one percent or even a fraction of a percent of the original system's capacitance to ground. Using the same displacement voltage threshold for line selection and identification, compared to the most sensitive resonant grounding method in traditional technology, the transition resistance identification capability is improved by 20 times or more, reaching over 50kΩ to 100kΩ.
[0036] In addition, the unbalanced voltage caused by a single-phase ground fault can also be calculated using the following formula:
[0037] (2)
[0038] In the formula: U 0 —Displacement voltage of the system during a ground fault;
[0039] E—System power supply phase voltage;
[0040] Δ — Capacitance decreases due to a broken wire.
[0041] As can be seen from equation (2), the ratio of the displacement voltage of the system during a ground fault to the reduction in capacitance caused by the phase disconnection is approximately proportional to the total capacitance to ground of the system. Obviously, after isolation, the total capacitance to ground of the local isolation system of the protection line is significantly reduced, and the ability to identify disconnection is greatly improved.
[0042] S3. When a single-phase ground fault is detected, the faulty phase is identified, and the single-phase switch of the identified faulty phase is closed.
[0043] According to formula (1), during a ground fault, the transition resistance... R f When the voltage changes from 0 to infinity, the displacement voltage is obtained. U 0 The trajectory is EA A semicircle with diameter located in the upper half, such as Figure 2 As shown.
[0044] Depend on Figure 2 It can be intuitively determined that the lagging phase of the highest voltage phase is the faulty phase. Therefore, after a single-phase ground fault, the isolation compensation device will close the single-phase switch corresponding to the faulty phase based on the determined faulty phase.
[0045] S4. Inject the reverse voltage of the fault phase voltage into the neutral point of the local isolation system of the protection line for full compensation.
[0046] In this embodiment, it is assumed that the faulty phase is phase A, and after a single-phase ground fault, the single-phase switch K... A When the circuit is closed, according to circuit principles, the phase-to-ground voltages of each phase of the protected line are:
[0047]
[0048]
[0049]
[0050] So, U 0 That is to say, the voltage injected into the neutral point of the local isolation system of the protection line is -E A At this time, the voltage to ground of the faulty phase line is:
[0051] (3)
[0052] As can be seen from equation (2), in this utility model, when a single-phase ground fault occurs in the protected line, the isolation compensation device can inject the reverse voltage of the fault phase voltage into the neutral point of the isolation system of the key protected line, so that the voltage of that phase line to ground is "zero" volts. According to the circuit principle, the grounding transition resistor R flows through the fault point. g The current must be "zero", thus achieving complete compensation of the voltage and current at the fault point to "zero".
[0053] This invention enables isolation and compensation of a protected circuit in the event of a single-phase ground fault using a single device, achieving rapid arc extinguishing. This not only improves efficiency and avoids the danger of electric shock, but also significantly reduces system construction and maintenance costs. It also avoids various faults caused by the cooperation between multiple devices, providing a reliable guarantee for the stable operation of the system.
Claims
1. A power distribution line isolation compensation device, characterized in that: The isolation and compensation device is connected between the system bus and the protection line to isolate and compensate the protection line when a single-phase ground fault occurs. The isolation and compensation device includes a primary winding (P), a load winding (LS), and a compensation winding (SC) that are coupled to each other. The primary winding (P) is connected to each phase of the system bus; the load winding (LS) is connected to each phase of the protection line to supply power to the power distribution equipment of the protection line; the compensation winding (SC) has the opposite polarity to the load winding (LS) and its neutral point is grounded.
2. The power distribution line isolation compensation device according to claim 1, characterized in that: The load winding (LS) and compensation winding (SC) of the isolation compensation device are both star-connected. The three-phase output terminals of the compensation winding (SC) are connected to one end of each of the three single-phase switches. The other ends of the three single-phase switches are short-circuited and connected to the neutral point of the load winding (LS).
3. The power distribution line isolation compensation device according to claim 1, characterized in that: The turns ratio of the primary winding (P) to the load winding (LS) and the primary winding (P) to the compensation winding (SC) are both 1:
1.
4. The power distribution line isolation compensation device according to claim 1, characterized in that: The capacity of the load winding (LS) is matched with the total load of the local isolation system of the protection line. The capacity of the primary winding (P) and the load winding (LS) are equal, and the capacity of the compensation winding (SC) is not less than the capacitive current compensation capacity of the local isolation system of the protection line.