A protection device for low-voltage side of main transformer of offshore booster station

Abstract

The utility model provides a kind of offshore booster station main transformer low voltage side protection device, the three sides of main transformer are all set circuit breaker, at least one set of bushing protection level current transformer, first main backup integrated protection device, second main backup integrated protection device are equipped between main transformer and low voltage side circuit breaker, the bushing protection level current transformer is respectively connected with first low voltage side current sampling loop, second low voltage side current sampling loop.Adding two groups of main transformer low voltage side bushing current transformer, access the low voltage side reserved current sampling loop of original protection device and set protection device program, the problem of insufficient sensitivity of low voltage side backup protection is solved at lower cost;A three-phase voltage transformer is configured on the upper end of the incoming line switch cabinet circuit breaker of the low voltage side of the main transformer, for detecting single-phase ground fault occurring on the low voltage side, especially the low voltage lead, and can send out alarm or tripping signal in time, improving the operation reliability of the unattended offshore booster station.

Description

Technical Field

[0001] This utility model relates to the field of offshore wind power generation, specifically to a low-voltage side protection device for the main transformer of an offshore substation. Background Technology

[0002] In my country, offshore wind power is developing towards large capacity and deep-sea applications. Currently, the voltage level of the collection system in offshore substations is generally 66kV, while the high-voltage transmission voltage level is 220kV or 500kV. Considering the compact layout of offshore substations, reducing platform size and weight, and lowering project costs, the power supply system for offshore substations is drawn from the 10kV third winding of the main transformer, and then stepped down to 380V by the auxiliary transformer. Therefore, the main transformer is usually a three-winding transformer of 220kV / 66kV / 10kV or 500kV / 66kV / 10kV. Due to the large impedance voltage between the high-voltage side and the low-voltage side of this three-winding transformer, the short-circuit current referred to the high-voltage side in the event of a two-phase or three-phase short-circuit fault on the low-voltage side is small. The high-voltage side backup protection of the main transformer is not sensitive enough to the low-voltage side protection, causing the high-voltage side backup protection to fail to operate. In addition, the low-voltage side is an ungrounded system, and there is a lack of effective detection methods for single-phase ground faults on the low-voltage side leads. Utility Model Content

[0003] The main objective of this invention is to provide a low-voltage side protection device for the main transformer of an offshore substation, which aims to effectively solve the problems in the background technology.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A low-voltage side protection device for a main transformer in an offshore substation is disclosed. The main transformer has a high-voltage side circuit breaker on its high-voltage side, a low-voltage side circuit breaker on its low-voltage side, and a medium-voltage side circuit breaker on its medium-voltage side. Two sets of main transformer low-voltage side bushing protection level current transformers, a first set of integrated main and backup protection devices, and a second set of integrated main and backup protection devices are provided between the main transformer and the low-voltage side circuit breakers. The first set of integrated main and backup protection devices includes a first low-voltage side current sampling circuit, and the second set of integrated main and backup protection devices includes a second low-voltage side current sampling circuit. The main transformer low-voltage side bushing protection level current transformers are connected to the first low-voltage side current sampling circuit and the second low-voltage side current sampling circuit, respectively.

[0006] While adopting the above technical solutions, this utility model may also adopt or combine the following technical solutions:

[0007] A three-phase voltage transformer is also provided between the main transformer and the low-voltage side circuit breaker.

[0008] The first set of integrated main and backup protection devices also includes a first low-voltage side voltage sampling circuit, and the second set of integrated main and backup protection devices also includes a second low-voltage side voltage sampling circuit.

[0009] The three-phase voltage transformers are respectively connected to the first low-voltage side voltage sampling circuit and the second low-voltage side voltage sampling circuit.

[0010] This utility model provides a low-voltage side protection device for the main transformer of an offshore substation, which has the following advantages: By adding two sets of low-voltage side bushing current transformers to the original protection device and connecting them to the low-voltage side reserved current sampling circuit (factory-preset current protection program), the problem of insufficient sensitivity of the low-voltage side backup protection is solved at a lower cost, supporting the promotion and application of this type of three-winding transformer in offshore wind farms, promoting the miniaturization and lightness of offshore substations, and improving the economic efficiency of projects; In addition, a three-phase voltage transformer is configured at the upper end of the circuit breaker of the low-voltage side incoming switchgear of the main transformer to detect single-phase grounding short-circuit faults occurring on the low-voltage side, especially on the low-voltage leads, and can promptly issue alarm or trip signals, improving the unattended operation reliability of the offshore substation. Attached Figure Description

[0011] Figure 1 This utility model provides a low-voltage side protection device for the main transformer of an offshore substation.

[0012] Figure 2 The protection principle diagram of the low-voltage side protection device of the main transformer;

[0013] Figure 3 Flowchart of protection operation of the low-voltage side protection device of the main transformer;

[0014] In the diagram: 1-High-voltage side circuit breaker; 2-Low-voltage side circuit breaker; 3-Medium-voltage side circuit breaker; 4-Main transformer; 5-Main transformer low-voltage side bushing protection stage current transformer; 6-Three-phase voltage transformer; 7-First set of main and backup integrated protection device; 8-Second set of main and backup integrated protection device; 71-First low-voltage side current sampling circuit; 72-First low-voltage side voltage sampling circuit; 81-Second low-voltage side current sampling circuit; 82-Second low-voltage side voltage sampling circuit. Detailed Implementation

[0015] The present invention will be further described in detail with reference to the accompanying drawings and specific embodiments.

[0016] like Figure 1As shown, a low-voltage side protection device for a main transformer in an offshore substation includes a high-voltage side circuit breaker 1 on the high-voltage side of the main transformer 4, a low-voltage side circuit breaker 2 on the low-voltage side of the main transformer 4, and a medium-voltage side circuit breaker 3 on the medium-voltage side of the main transformer 4. Two sets of main transformer low-voltage side bushing protection stage current transformers 5, a first set of main and backup integrated protection devices 7 (e.g., PCS-978T2), and a second set of main and backup integrated protection devices 8 (e.g., PCS-978T2) are provided between the main transformer 4 and the low-voltage side circuit breaker 2. The first set of main and backup integrated protection devices 7 includes a first low-voltage side current sampling circuit 71, and the second set of main and backup integrated protection devices... The device 8 includes a second low-voltage side current sampling circuit 81. The current transformer 5 of the main transformer low-voltage side bushing protection stage is connected to the first low-voltage side current sampling circuit 71 and the second low-voltage side current sampling circuit 81 respectively. The internal program and internal wiring of the protection device are updated by the protection manufacturer. The newly set overcurrent protection at the bushing of the main transformer 4 serves as backup protection for two-phase or three-phase short circuits of the low-voltage side leads of the main transformer 4. The protection trips the main transformer low-voltage side circuit breaker 2 in the first time limit to clear the fault below the low-voltage side circuit breaker 2 of the main transformer 4. The protection trips the circuit breakers on each side of the main transformer in the second time limit to clear the fault in the leads between the transformer bushing and the low-voltage side circuit breaker 2.

[0017] A three-phase voltage transformer 6 is also installed between the main transformer 4 and the low-voltage side circuit breaker 2.

[0018] The first set of integrated main and backup protection device 7 also includes a first low-voltage side voltage sampling circuit 72, and the second set of integrated main and backup protection device 8 also includes a second low-voltage side voltage sampling circuit 82.

[0019] like Figure 2-3 As shown, the first set of main and backup integrated protection devices 7 and the second set of main and backup integrated protection devices 8 collect the fault current signal of the protection level current transformer 5 at the low-voltage side bushing through the first low-voltage side current sampling circuit 71 and the second low-voltage side current sampling circuit 81, and the overcurrent protection of the first set of main and backup integrated protection devices 7 and the second set of main and backup integrated protection devices 8 is activated.

[0020] The three-phase voltage transformer 6 is connected to the first low-voltage side voltage sampling circuit 72 and the second low-voltage side voltage sampling circuit 82 respectively, and serves as a signal for a single-phase ground fault on the low-voltage side lead of the main transformer 4, for alarm or tripping.

[0021] The above specific embodiments are used to explain and illustrate the present utility model, and are only preferred embodiments of the present utility model, and are not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc. made to the present utility model within the spirit and protection scope of the claims shall fall within the protection scope of the present utility model.

Claims

1. A low-voltage side protection device for a main transformer in an offshore substation, characterized in that: The main transformer (4) is equipped with a high-voltage side circuit breaker (1) on the high-voltage side, a low-voltage side circuit breaker (2) on the low-voltage side, and a medium-voltage side circuit breaker (3) on the medium-voltage side. Two sets of main transformer low-voltage side bushing protection level current transformers (5), a first set of main and backup integrated protection devices (7), and a second set of main and backup integrated protection devices (8) are provided between the main transformer (4) and the low-voltage side circuit breaker (2). The first set of main and backup integrated protection devices (7) includes a first low-voltage side current sampling circuit (71), and the second set of main and backup integrated protection devices (8) includes a second low-voltage side current sampling circuit (81). The main transformer low-voltage side bushing protection level current transformers (5) are connected to the first low-voltage side current sampling circuit (71) and the second low-voltage side current sampling circuit (81) respectively.

2. The low-voltage side protection device for the main transformer of an offshore substation according to claim 1, characterized in that: A three-phase voltage transformer (6) is also provided between the main transformer (4) and the low-voltage side circuit breaker (2); The first set of main and backup integrated protection device (7) also includes a first low-voltage side voltage sampling circuit (72), and the second set of main and backup integrated protection device (8) also includes a second low-voltage side voltage sampling circuit (82); The three-phase voltage transformer (6) is connected to the first low-voltage side voltage sampling circuit (72) and the second low-voltage side voltage sampling circuit (82), respectively.

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