Anti-interference circuit structure for reducing zero sequence current protection maloperation
By connecting the high-voltage transformer circuit in series on the primary side of the current transformer and grounding through the transformer neutral terminal strip, combining the insulating sleeve and reducing the current transformer ratio, the problem of zero-sequence current protection error of the main transformer is solved, and the anti-interference ability of the system and the accuracy of the protection device are improved.
Patent Information
- Application Number
- CN202422399312.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-30
- Publication Date
- 2025-08-26
- Estimated Expiration
- 2034-09-30
AI Technical Summary
The zero-sequence current protection device of the main transformer is prone to erroneous movement after the insulation of the secondary cable of the current loop is damaged, resulting in the generator set being non-stopped, and the existing technology lacks an effective solution.
By connecting the transformer high-voltage circuit in series on the primary side of the current transformer, connecting the protection cabinet on the secondary side and grounding through the transformer neutral terminal strip, increasing the insulating sleeve and reducing the current transformer ratio, improving the system's anti-interference ability.
It effectively reduces the interference voltage of the zero-sequence circulation, reduces the impact of the external electromagnetic field on the current loop, improves the accuracy and reliability of the protection device, and avoids malfunctions.
Smart Images
Figure CN223273850U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the field of electrical technology, in particular to an anti-interference circuit structure for reducing false operation of zero-sequence current protection. Background Art
[0002] In the power system, the stable operation of the main transformer is crucial to the safe operation of the entire power grid. However, due to reasons such as the damage of the insulation sheath of the secondary cable in the current loop, a circulating current is generated through the secondary circuit of the current transformer under the action of the ground potential voltage difference, resulting in frequent false tripping of the main transformer current protection, which seriously affects the stable operation of the generator set. Specifically, the insulation layer of the secondary cable connected to the 1S1 terminal of the zero-sequence current transformer on the high-voltage side of the main transformer is damaged and grounded through the terminal box (the main grounding grid in the main transformer area), and the secondary cable ground wire in the protection room is grounded at the protection panel cabinet in the relay protection room (the equipotential copper busbar in the protection room). Since there is a potential difference (i.e. voltage) between the two grounding points at this time and the value is large enough, the generated zero-sequence circulating current is introduced into the protection device through the secondary cable, causing the protection device to trip, resulting in the serious consequence of the unit not stopping. At present, there is a lack of a solution on the market that can effectively solve the above problems. Utility Model Content
[0003] The utility model provides an anti-interference circuit structure for reducing false operation of zero-sequence current protection, so as to solve the technical defects of the above-mentioned prior art.
[0004] In order to solve the above technical problems, the technical solution of the utility model is an anti-interference circuit structure for reducing the false operation of zero-sequence current protection, which is characterized in that it includes a transformer, a current transformer, and a protection cabinet. The primary side of the current transformer is connected in series in the high-voltage line of the transformer, the secondary side of the current transformer is connected to the protection device in the protection cabinet through a cable, the primary side of the current transformer is grounded through the neutral point on the high-voltage line side of the transformer, and the secondary side of the current transformer is grounded through the zero-line terminal block of the transformer.
[0005] Specifically, the secondary circuit line of the current transformer is covered with an insulating sleeve.
[0006] Specifically, the insulating sleeve is a yellow wax tube.
[0007] Specifically, the wire threading holes of the current transformer junction box are treated to prevent wear.
[0008] Specifically, the current transformer ratio is reduced.
[0009] Specifically, the reduced current transformer ratio is 300.
[0010] Specifically, the zero-sequence current overcurrent setting is increased.
[0011] Specifically, the increased zero-sequence current overcurrent setting is 1.0A.
[0012] Since the ground wire in the zero-sequence current secondary circuit is grounded at one point inside the protective screen and transformed into grounding through the transformer neutral terminal block, the value of the interference voltage is reduced, the influence of the external electromagnetic field on the current circuit is reduced, and the anti-interference ability of the system is improved. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings described below only relate to some embodiments of the present application, and are not limitations to the present application.
[0014] Figure 1 This is a diagram of the anti-interference circuit structure for reducing false operation of zero-sequence current protection in the embodiment.
[0015] Figure 2 Schematic diagram of zero-sequence circulating current caused by insulation damage of the secondary cable at 1S1 DETAILED DESCRIPTION
[0016] To make the purpose, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below in conjunction with the drawings of the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the described embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.
[0017] Unless otherwise defined, technical or scientific terms used herein shall have the same meaning as commonly understood by a person having ordinary skills in the field to which this application belongs.
[0018] The specific embodiments of the present invention are described in detail and completely below with reference to the accompanying drawings.
[0019] like Figure 1 As shown, an anti-interference circuit structure for reducing false zero-sequence current protection operation is characterized by including a transformer, a current transformer, and a protection cabinet. The primary side of the current transformer is connected in series with the high-voltage line of the transformer, and the secondary side of the current transformer is connected to the protection device in the protection cabinet via a cable. The primary side of the current transformer is grounded through the neutral point on the high-voltage line side of the transformer, and the secondary side of the current transformer is grounded through the transformer neutral terminal block. The reason for the false zero-sequence protection operation is that after the insulation layer of the secondary cable is damaged and grounded, there is a potential difference between the grounding point of the secondary ground wire, forming a zero-sequence circulating current between the two grounding points. The zero-sequence circulating current I0 is:
[0020] When the zero-sequence circulating current reaches the zero-sequence current protection setting value, the zero-sequence protection operates. If the secondary circuit insulation is intact, there will be no zero-sequence circulating current I0. Even if the secondary circuit insulation is damaged and a zero-sequence circulating current is generated, the magnitude of the zero-sequence circulating current is proportional to the voltage difference between the two grounding points and inversely proportional to the loop resistance. We can seek solutions to the problem by improving the reliability of the secondary circuit, reducing the value of the interference voltage, increasing the loop resistance, and increasing the protection setting value d. In terms of reducing the value of interference voltage, before the transformation, the ground wire in the zero-sequence current secondary circuit was grounded at one point inside the protection screen. After the transformation, the grounding point of the zero-sequence current secondary circuit was changed from the protection screen to the neutral terminal block of the transformer. When the L line close to the local junction box side is grounded due to insulation damage (the environment of the secondary cable on the local junction box side is worse than the environment of the cable inside the protection screen, and the probability of insulation damage is higher), the potential difference between the two grounding points will generate current in the secondary circuit. The current flowing into the protection device through the L and N secondary lines is significantly smaller than the current flowing into the protection device mainly through the L line when the secondary circuit grounding point is inside the protection screen. This can greatly reduce the risk of false operation of the zero-sequence overcurrent protection.
[0021] Specifically, the secondary circuit of the current transformer is covered with an insulating sleeve. This method is used to enhance the insulation level of the secondary circuit by adopting high-insulation cable materials, adding insulation barriers or insulating sleeves, etc., to reduce leakage current in the current circuit and improve the insulation performance of the system.
[0022] Specifically, the insulating sleeve is a yellow wax tube, which has excellent insulation performance, high temperature resistance, good flexibility, wear resistance and corrosion resistance, and also has certain flame retardant properties.
[0023] Specifically, the wire through-holes of the current transformer junction box are treated to prevent wear. The space of the wire through-holes of the original junction box is narrow, which is very easy to squeeze and damage the cable core. The through-holes are now treated to prevent wear, so as to avoid squeezing and damage to the cable core.
[0024] Specifically, the current transformer ratio is reduced to increase the current allowed to pass through the secondary line, thereby improving the accuracy and reliability of the protection function.
[0025] Specifically, the reduced current transformer ratio is 300, and the current transformer ratio of 300 best balances ensuring normal operation of the protection device and avoiding malfunction of the protection device.
[0026] Specifically, the zero-sequence current overcurrent setting is increased to increase the current allowed to pass through the secondary line, thereby improving the accuracy and reliability of the protection function.
[0027] Specifically, the increased zero-sequence current overcurrent setting is 1.0 A. The zero-sequence current overcurrent setting of 1.0 A best balances ensuring the normal operation of the protection device and avoiding malfunction of the protection device.
[0028] The above description is merely an exemplary embodiment of the present application and is not intended to limit the scope of protection of the present application. The scope of protection of the present application is determined by the appended claims.
Claims
1. An anti-interference circuit structure for reducing false operation of zero-sequence current protection, characterized in that It includes a transformer, a current transformer, and a protection cabinet. The primary side of the current transformer is connected in series in the high-voltage line of the transformer. The secondary side of the current transformer is connected to the protection device in the protection cabinet through a cable. The primary side of the current transformer is grounded through the neutral point on the high-voltage line side of the transformer, and the secondary side of the current transformer is grounded through the zero-line terminal block of the transformer.
2. The anti-interference circuit structure for reducing false operation of zero-sequence current protection according to claim 1 is characterized in that The secondary circuit of the current transformer is covered with an insulating sleeve.
3. The anti-interference circuit structure for reducing false operation of zero-sequence current protection according to claim 2 is characterized in that The insulating sleeve is a yellow wax tube.
4. The anti-interference circuit structure for reducing false operation of zero-sequence current protection according to claim 1 is characterized in that The wire threading holes of the current transformer junction box are treated to prevent wear.
5. The anti-interference circuit structure for reducing false operation of zero-sequence current protection according to claim 1 is characterized in that The current transformer ratio is reduced.
6. The anti-interference circuit structure for reducing false operation of zero-sequence current protection according to claim 5, characterized in that The reduced current transformer ratio is 300.
7. The anti-interference circuit structure for reducing false operation of zero-sequence current protection according to claim 1 is characterized in that Added zero-sequence current overcurrent setting.
8. The anti-interference circuit structure for reducing malfunction of zero-sequence current protection according to claim 7, characterized in that The added zero sequence current overcurrent setting is 1.0A.