A single-phase grounding fault judgment and protection system and method for a new energy power station

Abstract

The present invention provides a single-phase grounding fault judgment and protection system and method for a new energy power station, which can accurately detect and cut off single-phase grounding faults and ensure the normal operation of the power system; the high-voltage side of the main transformer is connected to the power grid after passing through the main transformer high-voltage side circuit breaker, the low-voltage side of the main transformer is connected to the power supply and distribution bus through the incoming line circuit breaker, and the high-voltage side of the grounding transformer is connected to the power supply and distribution bus through the grounding transformer circuit breaker. It includes: a main transformer low-voltage side voltage transformer arranged between the low-voltage side of the main transformer and the incoming line circuit breaker; a grounding transformer zero-sequence current transformer arranged between the low-voltage side of the grounding transformer and the ground; and a drive controller that judges faults according to the zero-sequence current detected by the grounding transformer zero-sequence current transformer and the zero-sequence voltage detected by the main transformer low-voltage side voltage transformer, and outputs a control signal when the detected zero-sequence current or zero-sequence voltage exceeds the limit to make the high-voltage side switch and / or the low-voltage side switch of the main transformer act.

Description

Technical Field

[0001] The present invention relates to the technical field of power system fault protection, and specifically to a single-phase grounding fault judgment and protection system and method for a new energy power station. Background Art

[0002] In the new energy power station, the in-station collector lines have voltage levels of 35 kV and 10 kV, including an ungrounded system, an arc suppression coil grounded system, and a resistance grounded system. Among them, the resistance grounded system is widely used. The grounding transformers equipped with grounding resistors are mostly installed on the 35 kV and 10 kV distribution buses. If a single-phase grounding fault occurs on the low-voltage side of the transformer, the zero-sequence protection of the grounding transformer will act. Although the grounding transformer is cut off and the grounding fault quantity disappears, the single-phase grounding fault on the low-voltage side of the transformer still cannot be cut off. In some power stations, the grounding transformer is installed on the low-voltage side of the bus. When a single-phase grounding fault occurs on the low-voltage side of the transformer, the single-phase grounding fault on the low-voltage side of the transformer can be cut off through the action of the zero-sequence protection of the grounding transformer. However, some faults of the grounding transformer will cause the action of protections such as the differential protection of the main transformer, resulting in the power outage of the main transformer and the expansion of the accident power outage range, thus affecting the operation of the power system. Summary of the Invention

[0003] In view of the above problems, the present invention provides a single-phase grounding fault judgment and protection system and method for a new energy power station, which can accurately detect and cut off single-phase grounding faults and ensure the normal operation of the power system.

[0004] The technical solution is as follows:

[0005] A single-phase grounding fault judgment and protection system for a new energy power station, which includes a main transformer and a grounding transformer. The high-voltage side of the main transformer is connected to the power grid through a main transformer high-voltage side circuit breaker. The low-voltage side of the main transformer is connected to the power supply and distribution bus through an incoming line circuit breaker. The high-voltage side of the grounding transformer is connected to the power supply and distribution bus through a grounding transformer circuit breaker. It is characterized in that it further includes:

[0006] A main transformer low-voltage side voltage transformer arranged between the low-voltage side of the main transformer and the incoming line circuit breaker;

[0007] A grounding transformer zero-sequence current transformer arranged between the low-voltage side of the grounding transformer and the ground;

[0008] And a drive controller that judges faults according to the zero-sequence current detected by the grounding transformer zero-sequence current transformer and the zero-sequence voltage detected by the main transformer low-voltage side voltage transformer, and outputs a control signal when the detected zero-sequence current or zero-sequence voltage exceeds the limit to make the high-voltage side switch and / or low-voltage side switch of the main transformer act.

[0009] It is further characterized in that:

[0010] When the zero-sequence current detected by the zero-sequence current transformer of the earthing transformer exceeds the first protection limit value, the drive controller controls the incoming line breaker and the earthing transformer breaker to trip, and memorizes and holds the zero-sequence current for a certain period of time;

[0011] When the zero-sequence voltage detected by the zero-sequence voltage transformer on the low-voltage side of the main transformer exceeds the second protection limit value, the drive controller controls the breaker on the high-voltage side of the main transformer to trip;

[0012] The voltage on the power supply and distribution bus is 10 kV or 35 kV;

[0013] A single-phase grounding fault judgment and protection method for a new energy power station, characterized in that it includes the following steps:

[0014] S1. Collect the zero-sequence current I through the zero-sequence current transformer of the earthing transformer 0 , and collect the zero-sequence voltage U through the zero-sequence voltage transformer on the low-voltage side of the main transformer 0 ;

[0015] S2. Collect the position information of the incoming line breaker. If the zero-sequence current I 0 exceeds the first protection limit value, it is judged that there is a fault on the low-voltage side of the main transformer. The drive controller controls the incoming line breaker and the earthing transformer breaker to trip, cuts off the fault line on the low-voltage side of the main transformer, and memorizes and holds the zero-sequence current for 5 s to 10 s;

[0016] S3. After cutting off the fault line, if the fault still exists and meets the fault judgment conditions, the drive controller controls the breaker on the high-voltage side of the main transformer to trip.

[0017] It is further characterized in that:

[0018] In the step S3, the fault judgment includes the logical AND of the following conditions:

[0019] The breaker on the high-voltage side of the main transformer is in the closed position, and the incoming line breaker is in the open position;

[0020] The zero-sequence voltage transformer on the low-voltage side of the main transformer has no disconnection;

[0021] The positive-sequence voltage U of the power supply and distribution bus 1 > 30 V, and the negative-sequence voltage U 2 < 8 V;

[0022] 3U 0 > 60 V.

[0023] The beneficial effects of the present invention are as follows. By installing a voltage transformer on the low-voltage side of the main transformer and a zero-sequence current transformer on the low-voltage side of the grounding transformer, zero-sequence voltage and zero-sequence current are collected, and a grounding protection jointly affected by the zero-sequence voltage and the memory zero-sequence current can be formed. When a single-phase grounding fault occurs on the low-voltage side of the main transformer, the incoming line breaker and the grounding transformer breaker trip, and the grounding transformer exits operation. If the fault still exists and meets the fault judgment conditions, the breaker on the high-voltage side of the main transformer is tripped to cut off the faulty line on the high-voltage side of the main transformer, thereby accurately judging and cutting off the single-phase grounding fault, ensuring the normal operation of the power system, and having good economic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic diagram of the principle of the present invention;

[0025] Figure 2 is a schematic diagram of the control logic of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments, and are not intended to limit the scope of the present invention. In addition, in the following description, the descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts disclosed in the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0027] The structural schematic diagrams according to the disclosed embodiments of the present invention are shown in the drawings. These figures are not drawn to scale, and for the purpose of clear expression, some details are enlarged and some details may be omitted. The shapes of various regions and layers shown in the figures and their relative sizes and positional relationships are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art can design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0028] As Figure 1 , Figure 2 shown, a single-phase grounding fault judgment and protection system for a new energy power station includes a main transformer 1 and a grounding transformer 2. The high-voltage side of the main transformer 1 is connected to the power grid (not shown in the figure) through a breaker on the high-voltage side of the main transformer 3. The low-voltage side of the main transformer 1 is connected to the power supply and distribution bus 5 through an incoming line breaker 4. The high-voltage side of the grounding transformer 2 is connected to the power supply and distribution bus 5 through a breaker of the grounding transformer 6. The voltage on the power supply and distribution bus 5 is 10 kV or 35 kV; it further includes:

[0029] A voltage transformer 7 on the low-voltage side of the main transformer 1 between the low-voltage side of the main transformer 1 and the incoming line breaker 4;

[0030] A zero-sequence current transformer 8 of the grounding transformer 2 between the low-voltage side of the grounding transformer 2 and the ground;

[0031] And a drive controller (not shown in the figure) that judges faults based on the zero-sequence current detected by the zero-sequence current transformer 8 of the grounding transformer and the zero-sequence voltage detected by the voltage transformer 7 on the low-voltage side of the main transformer, and outputs a control signal when the detected zero-sequence current or zero-sequence voltage exceeds the limit to cause the high-voltage side switch and / or low-voltage side switch of the main transformer 1 to act. The drive controller uses an existing controller, that is, when the zero-sequence current detected by the zero-sequence current transformer 8 of the grounding transformer exceeds the first protection limit value, the drive controller outputs a control signal to trip the incoming line breaker 4 and the grounding transformer breaker 6, and memorizes and holds the zero-sequence current for a certain period of time;

[0032] When the zero-sequence voltage detected by the voltage transformer 7 on the low-voltage side of the main transformer exceeds the second protection limit value, the drive controller outputs a control signal to trip the high-voltage side breaker 3 of the main transformer.

[0033] The first protection limit value and the second protection limit value in the present invention can be set according to actual situations.

[0034] A single-phase grounding fault judgment and protection method for a new energy power station, comprising the following steps:

[0035] S1. Collect the zero-sequence current I through the zero-sequence current transformer 8 of the grounding transformer 0 , and collect the zero-sequence voltage U through the voltage transformer 7 on the low-voltage side of the main transformer 0 ;

[0036] S2. Collect the position information of the incoming line breaker 4. If the zero-sequence current I 0 exceeds the first protection limit value, it is judged that there is a fault on the low-voltage side of the main transformer. The drive controller controls the incoming line breaker 4 and the grounding transformer breaker 6 to trip, and cuts off the fault line on the low-voltage side of the main transformer 1 (such as Figure 1 at the position of the lightning arrow in the figure), and memorizes and holds the zero-sequence current for 5 s to 10 s;

[0037] S3. After cutting off the fault line, if the fault still exists and meets the fault judgment conditions, the drive controller controls the high-voltage side breaker 3 of the main transformer to trip;

[0038] Specifically, the fault judgment includes the logical AND of the following conditions:

[0039] The high-voltage side breaker 3 of the main transformer is in the closed position, and the incoming line breaker 4 is in the open position;

[0040] The voltage transformer 7 on the low-voltage side of the main transformer has no disconnection;

[0041] The positive-sequence voltage U of the power supply and distribution bus 5 1 > 30V, and the negative-sequence voltage U 2 < 8V;

[0042] 3U 0 > 60V.

[0043] Through the voltage transformer 7 on the low-voltage side of the main transformer 1 and the zero-sequence current transformer 8 on the low-voltage side of the grounding transformer 2 installed in the present invention, the zero-sequence voltage and zero-sequence current are collected, and a grounding protection jointly acting on the zero-sequence voltage and the memory zero-sequence current can be formed. When a single-phase grounding fault occurs on the low-voltage side of the main transformer 1, the incoming line breaker 4 and the grounding transformer breaker 6 trip, and the grounding transformer exits the operation. If the fault still exists and meets the fault judgment conditions, the main transformer high-voltage side breaker 3 is tripped to cut off the faulty line on the high-voltage side of the main transformer, so as to accurately judge and cut off the single-phase grounding fault, and thus ensure the normal operation of the power system.

[0044] Such as Figure 1 In, if the present invention still needs to perform fault judgment protection on the collector line, the method of the present invention can still be used. A collector line breaker 9 and a collector line zero-sequence current transformer 10 are installed on the collector line. The collector line breaker 9 is connected to the power supply and distribution bus 5, and the collector line zero-sequence current transformer 10 is located at the beginning of the collector line.

[0045] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0046] In addition, it should be understood that although this specification is described according to the embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A single-phase grounding fault judgment and protection system for a new energy power station, which includes a main transformer and a grounding transformer. The high-voltage side of the main transformer is connected to the power grid after passing through the main transformer high-voltage side circuit breaker. The low-voltage side of the main transformer is connected to the power supply and distribution bus through the incoming line circuit breaker. The high-voltage side of the grounding transformer is connected to the power supply and distribution bus through the grounding transformer circuit breaker. Characterized in that, It further includes: A main transformer low-voltage side voltage transformer arranged between the low-voltage side of the main transformer and the incoming line circuit breaker; A grounding transformer zero-sequence current transformer arranged between the low-voltage side of the grounding transformer and the ground; And a drive controller that judges faults based on the zero-sequence current detected by the grounding transformer zero-sequence current transformer and the zero-sequence voltage detected by the main transformer low-voltage side voltage transformer, and outputs a control signal when the detected zero-sequence current or zero-sequence voltage exceeds the limit to cause the high-voltage side switch and / or low-voltage side switch of the main transformer to act. When the zero-sequence current detected by the grounding transformer zero-sequence current transformer exceeds the first protection limit value, the drive controller controls the incoming line circuit breaker and the grounding transformer circuit breaker to trip, and memorizes and holds the zero-sequence current for a certain period of time. When the zero-sequence voltage detected by the main transformer low-voltage side voltage transformer exceeds the second protection limit value, the drive controller controls the main transformer high-voltage side circuit breaker to trip.

2. A single-phase grounding fault judgment and protection system for a new energy power station according to claim 1, Characterized in that: The voltage on the power supply and distribution bus is 10KV or 35kV.

3. A single-phase grounding fault judgment and protection method for a new energy power station, Characterized in that: It includes a single-phase grounding fault judgment and protection system for a new energy power station as described in claim 1 or 2, The method further includes the following steps: S1. Collect zero-sequence current through the zero-sequence current transformer of the grounding transformer I 0 , and collect zero-sequence voltage through the voltage transformer on the low-voltage side of the main transformer U 0 ; S2. Collect the position information of the incoming line circuit breaker. If the zero-sequence current I 0 exceeds the first protection limit value, it is determined that there is a fault on the low-voltage side of the main transformer. The drive controller controls the incoming line circuit breaker and the grounding transformer circuit breaker to trip, cuts off the faulty line on the low-voltage side of the main transformer, and memorizes and holds the zero-sequence current for 5 s to 10 s; S3. After cutting off the faulty line, if there is still a fault and the fault judgment conditions are met, the drive controller controls the main transformer high-voltage side circuit breaker to trip.

4. A single-phase grounding fault judgment and protection method for a new energy power station according to claim 3, Characterized in that: Characterized in that: In the step S3, the fault judgment includes the logical AND of the following conditions: The main transformer high-voltage side circuit breaker is in the closed position, and the incoming line circuit breaker is in the open position; The main transformer low-voltage side voltage transformer has no disconnection; Positive-sequence voltage of the power supply and distribution bus U 1 > 30V, negative-sequence voltage U 2 < 8V; 3U 0 > 60V.

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