An inter-turn protection method based on absolute value comparison

Abstract

The application provides a kind of turn-to-turn protection method based on absolute value comparison, and existing turn-to-turn protection is amplitude comparison type, so when fault, the position of zero sequence source in system zero sequence loop determines the fault position, only reliable action in 0°-180° direction can be realized, and the action equation is absolute value, full-angle action can be realized, the new principle turn-to-turn protection adopted by the method can correctly distinguish internal and external faults of reactor, has high sensitivity to internal turn-to-turn short-circuit fault of reactor, and for external fault and other abnormal operating conditions, the protection is reliable and does not act. In addition, the turn-to-turn protection is also provided with a reactor empty charging processing element to eliminate the influence of low-order harmonics in zero sequence unbalanced voltage and current, ensure that the protection is reliable and does not misoperate when normal empty charging, non-full-phase empty charging and external fault during empty charging, and the protection is sensitive and fast when internal fault during empty charging.

Description

Technical Field

[0001] This invention relates to the field of management system technology, and in particular to an inter-turn protection method based on absolute value comparison. Background Technology

[0002] Inter-turn protection is a specialized protection measure in power systems used to protect against inter-turn short circuits in the windings of equipment such as motors and transformers. Existing inter-turn protection systems are amplitude comparison type; during a fault, the location of the fault is determined by the location of the zero-sequence source in the system's zero-sequence circuit. This system can only achieve reliable operation in the 0°–180° direction, and its operating equation is as follows: Therefore, it is difficult to correctly distinguish between internal and external faults of the reactor. In addition, most high-voltage parallel reactors adopt a phase-separated structure, and the common faults are inter-turn short circuits or single-phase ground faults. However, when the number of short-circuit turns is small, the three-phase current imbalance caused by a single-phase inter-turn short circuit may be very small and difficult to detect. Furthermore, differential protection does not detect inter-turn short circuit faults in principle. Therefore, an inter-turn protection method based on absolute value comparison is proposed to solve the above problems. Summary of the Invention

[0003] Therefore, the purpose of this invention is to provide an inter-turn protection method based on absolute value comparison, so as to at least solve the above problems.

[0004] The technical solution adopted in this invention is as follows:

[0005] An inter-turn protection method based on absolute value comparison, the method comprising the following steps:

[0006] S1. Collect the ohmic data of the primary zero-sequence impedance of the reactor and the primary zero-sequence impedance of the system;

[0007] S2. Compare the ohmic data of the primary zero-sequence impedance of the reactor with the primary zero-sequence impedance of the system.

[0008] S3. If the primary zero-sequence impedance ohm data of the reactor falls into the set first interval value, it is classified as an external grounding fault of the reactor.

[0009] S4. If the zero-sequence impedance ohm data of the system falls into the set second interval value, it is classified as an inter-turn short circuit fault of the reactor or an internal grounding fault of the reactor.

[0010] Furthermore, in step S3, the first interval value is 1000-7000Ω.

[0011] Furthermore, in step S4, the second interval value is 10-100Ω.

[0012] Furthermore, the protection mechanisms categorized as external grounding faults of reactors and those categorized as inter-turn short-circuit faults and internal grounding faults of reactors are as follows:

[0013] Zero-order action element: 3I0>I set In the formula, 3I0 is the zero-sequence current generated by the CT at the first end of the reactor, I set The threshold for operation of zero-sequence current element; operating equation In the formula, 3U0 is the zero-sequence voltage generated by the PT, 3I0 is the zero-sequence current generated by the CT at the beginning of the reactor, and X L0 X is the zero-sequence reactance of the reactor. S0 This is the zero-sequence reactance of the system.

[0014] Furthermore, in step 4, when an inter-turn short-circuit fault occurs inside the reactor, the zero-sequence source is inside the reactor, and the reactor sends zero-sequence power to the system. At this time, the zero-sequence voltage measured by the inter-turn protection is... The amount of protective action is Braking amount It is zero.

[0015] Furthermore, when a ground fault occurs inside the reactor, the zero-sequence source is inside the reactor, and the reactor supplies zero-sequence power to the system. At this time, the zero-sequence voltage measured by the inter-turn protection is... The amount of protective action is Braking amount It is zero.

[0016] Furthermore, when an external ground fault occurs in the reactor, the zero-sequence source is outside the reactor, and the zero-sequence power flows into the reactor from the outside. At this time, the zero-sequence voltage measured by the inter-turn protection is... Protective action amount It is zero.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] This invention proposes an inter-turn protection method based on absolute value comparison. This invention can achieve full-angle operation, and the operation equation is as follows: The new principle of inter-turn protection adopted in this method can correctly distinguish between internal and external faults of the reactor. It has high sensitivity to internal inter-turn short circuit faults of the reactor, while the protection reliably does not operate under abnormal operating conditions such as external faults.

[0019] In addition, the inter-turn protection is equipped with a reactor no-charge processing element to eliminate the influence of low-order harmonics in zero-sequence unbalanced voltage and current, ensuring that the protection is reliable and does not malfunction during normal no-charge, non-full-phase no-charge, and external no-charge faults, while the protection is sensitive and fast during internal no-charge faults. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only preferred embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the overall process of an inter-turn protection method based on absolute value comparison proposed in an embodiment of the present invention.

[0022] Figure 2 This is a schematic diagram of an in-zone and out-of-zone fault of a reactor based on an inter-turn protection method using absolute value comparison proposed in an embodiment of the present invention.

[0023] Figure 3 This invention relates to an inter-turn protection method based on absolute value comparison for reactors during inter-turn short-circuit faults. and Schematic diagram.

[0024] Figure 4 This invention proposes an inter-turn protection method based on absolute value comparison for reactor internal grounding faults. and Schematic diagram.

[0025] Figure 5 This invention relates to an inter-turn protection method based on absolute value comparison proposed in an embodiment of the present invention for external ground fault protection. and Schematic diagram. Figure 6 This is a schematic diagram of the inter-turn absolute value comparison element operating in the shaded area of ​​the zero-sequence impedance in an inter-turn protection method based on absolute value comparison proposed in an embodiment of the present invention. Detailed Implementation

[0026] The principles and features of the present invention are described below with reference to the accompanying drawings. The listed embodiments are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0027] Reference Figures 1-6 This invention provides an inter-turn protection method based on absolute value comparison, the method comprising the following steps:

[0028] S1. Collect the ohmic data of the primary zero-sequence impedance of the reactor and the primary zero-sequence impedance of the system;

[0029] S2. Compare the ohmic data of the primary zero-sequence impedance of the reactor with the primary zero-sequence impedance of the system.

[0030] S3. If the primary zero-sequence impedance ohm data of the reactor falls into the set first interval value, it is classified as an external grounding fault of the reactor.

[0031] S4. If the zero-sequence impedance ohm data of the system falls into the set second interval value, it is classified as an inter-turn short circuit fault of the reactor or an internal grounding fault of the reactor.

[0032] In step S3, the first interval value is 1000-7000Ω.

[0033] In step S4, the value of the second interval is 10-100Ω.

[0034] The protection mechanisms for external grounding faults of reactors and for inter-turn short-circuit faults and internal grounding faults of reactors are as follows:

[0035] Zero-order action element: 3I0>I set In the formula, 3I0 is the zero-sequence current generated by the CT at the first end of the reactor, I set The threshold for operation of zero-sequence current element; operating equation In the formula, 3U0 is the zero-sequence voltage generated by the PT, 3I0 is the zero-sequence current generated by the CT at the beginning of the reactor, and X L0 X is the zero-sequence reactance of the reactor. S0 This is the zero-sequence reactance of the system.

[0036] In step 4, when an inter-turn short-circuit fault occurs inside the reactor, the zero-sequence source is inside the reactor, and the reactor sends zero-sequence power to the system. At this time, the zero-sequence voltage measured by the inter-turn protection is... The amount of protective action is Braking amount It is zero.

[0037] When a ground fault occurs inside the reactor, the zero-sequence source is inside the reactor, and the reactor supplies zero-sequence power to the system. At this time, the zero-sequence voltage measured by the inter-turn protection is... The amount of protective action is Braking amount It is zero.

[0038] When an external ground fault occurs in the reactor, the zero-sequence source is outside the reactor, and the zero-sequence power flows into the reactor from the outside. At this time, the zero-sequence voltage measured by the inter-turn protection is... Protective action amount It is zero.

[0039] For example, most high-voltage shunt reactors adopt a phase-separated structure. Common faults are inter-turn short circuits or single-phase ground faults. However, when the number of short-circuited turns is small, the three-phase current imbalance caused by a single-phase inter-turn short circuit may be very small and difficult to detect. Since differential protection does not detect inter-turn short circuit faults in principle, this method uses a new principle of inter-turn protection, which can sensitively detect inter-turn short circuits and single-phase ground faults in the reactor. Because the primary zero-sequence impedance of a reactor is generally around several thousand ohms, while the primary zero-sequence impedance of the system is generally around tens of ohms, the presence of an inter-turn fault can be determined by measuring the zero-sequence impedance at the reactor port. When a reactor experiences an inter-turn short circuit or an internal single-phase ground fault, the zero-sequence impedance measured at the reactor port is the system's zero-sequence impedance. When a reactor experiences an external single-phase ground fault, the zero-sequence impedance measured at the reactor port is the reactor's zero-sequence impedance. The significant difference between these two measured values ​​can be used to distinguish between reactor faults: K1—inter-turn short circuit fault; K2—internal ground fault; and K3—external ground fault. This method can sensitively detect faults.

[0040] In order to meet low impedance The experiment will be conducted under the specified conditions.

[0041] These represent phases a, b, and c, respectively. Z n This represents the neutral point reactance value. Z e This represents the phase reactance value of the main reactor. If 2I min <0.5I e When k is 0.5, I min ≥0.5I e When k is 0.9. Where I min I is the minimum value of the first-phase current. e This refers to the secondary rated current of the main reactor.

[0042] The equation of motion of the inter-turn absolute value comparator Can be launched Z0 is the zero-sequence reactance of the reactor, X L0 For the rated zero-sequence reactance of the reactor, X S0 The zero-sequence reactance on the system side is fixed at 0.05X. L0 ;

[0043] K1—Inter-turn short-circuit fault in the reactor; the zero-sequence voltage measured by the inter-turn protection at this time. The amount of protective action is Braking amount It is zero. Even when the number of short-circuit turns is small, due to the zero-sequence reactance X of the reactor... L0 The system's zero-sequence reactance X is very large. S0The voltage is relatively small, so the protection's operating amount is much greater than the braking amount, and the protection can also operate sensitively. K2—Internal grounding fault in the reactor; the zero-sequence voltage measured by the inter-turn protection at this time... The amount of protective action is Braking amount It is zero. Because the zero-sequence reactance X of the reactor is zero. L0 The system's zero-sequence reactance X is very large. S0 Because the amount of force applied is relatively small, the amount of force applied by the protection mechanism is much greater than the amount of force applied by the braking mechanism, and the protection mechanism can also act sensitively.

[0044] K3—External grounding fault of the reactor. When the reactor is short-circuited to an external ground, the zero-sequence source is outside the reactor, and the zero-sequence power flows into the reactor from the outside. At this time, the zero-sequence voltage measured by the inter-turn protection is... Protective action amount The braking amount is zero. Approximately equal to The amount of action is much smaller than the amount of braking, so the protection is reliable and does not activate.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A turn-to-turn protection method based on absolute value comparison, characterized in that, The method includes the following steps: S1. Collect the ohmic data of the primary zero-sequence impedance of the reactor and the primary zero-sequence impedance of the system; S2. Compare the ohmic data of the primary zero-sequence impedance of the reactor with the primary zero-sequence impedance of the system. S3. If the primary zero-sequence impedance ohm data of the reactor falls into the set first interval value, it is classified as an external grounding fault of the reactor. S4. If the zero-sequence impedance ohm data of the system falls into the set second interval value, it is classified as an inter-turn short circuit fault of the reactor or an internal grounding fault of the reactor.

2. The inter-turn protection method based on absolute value comparison according to claim 1, characterized in that, In step S3, the first interval value is 1000-7000Ω.

3. The inter-turn protection method based on absolute value comparison according to claim 2, characterized in that, In step S4, the value of the second interval is 10-100Ω.

4. The inter-turn protection method based on absolute value comparison according to claim 3, characterized in that, The protection mechanisms for external grounding faults of reactors and for inter-turn short-circuit faults and internal grounding faults of reactors are as follows: Zero-order action element: 3I0>I set In the formula, 3I0 is the zero-sequence current generated by the CT at the first end of the reactor, I set The threshold for operation of zero-sequence current element; operating equation In the formula, 3U0 is the zero-sequence voltage generated by the PT, 3I0 is the zero-sequence current generated by the CT at the beginning of the reactor, and X L0 X is the zero-sequence reactance of the reactor. S0 This is the zero-sequence reactance of the system.

5. The inter-turn protection method based on absolute value comparison according to claim 4, characterized in that, In step 4, when an inter-turn short-circuit fault occurs inside the reactor, the zero-sequence source is inside the reactor, and the reactor sends zero-sequence power to the system. At this time, the zero-sequence voltage measured by the inter-turn protection is... The amount of protective action is Braking amount It is zero.

6. The inter-turn protection method based on absolute value comparison according to claim 5, characterized in that, When a ground fault occurs inside the reactor, the zero-sequence source is inside the reactor, and the reactor supplies zero-sequence power to the system. At this time, the zero-sequence voltage measured by the inter-turn protection is... The amount of protective action is Braking amount It is zero.

7. The inter-turn protection method based on absolute value comparison as described in claim 6, characterized in that, When an external ground fault occurs in the reactor, the zero-sequence source is outside the reactor, and the zero-sequence power flows into the reactor from the outside. At this time, the zero-sequence voltage measured by the inter-turn protection is... Protective action amount It is zero.

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