Marine generator demagnetization protection method

Abstract

This invention relates to a method for protecting marine generators from excitation loss. It combines the reduction of the generator's current excitation current with the generator's reverse reactive power state as a condition for determining excitation loss faults, triggering the excitation loss protection action. This method quickly and accurately identifies excitation loss faults, preventing the generator from switching to asynchronous phase-advancing operation and thus avoiding safety and stability risks to the system. It fills the gap in current excitation loss protection for high-power marine generator sets, improves the reliability of marine power supply systems, and avoids safety hazards caused by generator excitation loss.

Description

Technical Field

[0001] This invention relates to the field of marine power system protection technology, and in particular to a method for protecting marine generators from loss of excitation. Background Technology

[0002] Currently, marine integrated protection devices have achieved a fully digital mode, generally possessing protection functions such as differential protection, overcurrent protection, voltage protection, zero-sequence protection, and frequency protection. For marine generator protection, differential protection, overcurrent protection, voltage protection, zero-sequence protection, frequency protection, and reverse power protection are typically configured to ensure rapid disconnection of the generator's main switch in the event of a short circuit or abnormal condition, guaranteeing the reliability and continuity of the power supply system. However, for high-power marine generator sets, over-excitation protection is currently not configured; when a generator set experiences an over-excitation fault, it may pose a safety hazard to the operation of the power system. Summary of the Invention

[0003] A method for protecting marine generators from demagnetization faults is proposed.

[0004] The technical solution of the present invention is: a method for protecting a marine generator from excitation loss, which combines the current reduction of the generator's excitation current with the generator's reverse reactive power state as a condition for judging excitation loss fault and triggering the excitation loss protection action.

[0005] The method for protecting the marine generator from excitation specifically includes the following steps:

[0006] 1) The integrated protection device obtains the current excitation current information of the generator through the CAN communication interface;

[0007] 2) The integrated protection device collects the three-phase voltage and three-phase current at the generator terminals to calculate the reactive power.

[0008] 3) When the following four conditions are met simultaneously, a demagnetization fault is determined to have occurred, and alarm and protection actions are executed:

[0009] Condition 1: 0 < excitation current Im < excitation current threshold Iset;

[0010] Condition 2: Reactive power Q < 0 and |reactive power Q| < reactive power threshold Qset;

[0011] Condition 3: CAN communication interface is functioning normally;

[0012] Condition 4: Conditions 1, 2, and 3 are continuously met for more than the protection set delay time Tset;

[0013] 4) The return condition for demagnetization fault is: any one of the above conditions 1, 2, or 3 is not met for 1 second.

[0014] Furthermore, the excitation current threshold Iset value is equal to the no-load excitation current of the generator.

[0015] Furthermore, the reactive power threshold Qset value is equal to the generator's rated reactive power.

[0016] Furthermore, the CAN communication interface communication status judgment method is as follows: the generator sends an excitation current message to the integrated protection device every 500ms. After receiving a correct message, the excitation current is extracted, indicating that the CAN communication is normal; if the generator's excitation current message is not received for more than 2 seconds, the CAN communication is determined to be abnormal.

[0017] The beneficial effects of this invention are as follows: the marine generator demagnetization protection method of this invention can quickly and accurately identify demagnetization faults and avoid the safety and stability risks to the system caused by the generator changing to asynchronous phase-advancing operation; it fills the gap in the current demagnetization protection of high-power marine generator sets; it improves the reliability of marine power system power supply and avoids safety hazards caused by generator demagnetization. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the demagnetization protection method for marine generators according to the present invention. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0020] A method for protecting marine generators from demagnetization has been invented that comprehensively utilizes the operating quadrant characteristics of generator excitation current and reactive power at the generator terminals.

[0021] (1) The integrated protection device obtains the current excitation current information of the generator through the CAN communication interface;

[0022] (2) The integrated protection device collects the three-phase voltage and three-phase current at the generator terminals to calculate the reactive power;

[0023] (3) When the following four conditions are met simultaneously, a demagnetization fault is determined to have occurred, and alarm and protection actions are executed:

[0024] Condition 1: 0 < excitation current Im < excitation current threshold Iset, where the value of excitation current threshold Iset is the no-load excitation current of the generator;

[0025] Condition 2: Reactive power Q < 0 and |reactive power Q| < reactive power threshold Qset, where the value of reactive power threshold Qset is the rated reactive power of the generator;

[0026] Condition 3: CAN communication interface is functioning normally;

[0027] Condition 4: Conditions 1, 2, and 3 are continuously met for more than the protection set delay time Tset. The protection set delay time Tset is generally set within the range of 5s to 10s.

[0028] (4) The return condition for demagnetization fault is: any one of the above conditions 1, 2, or 3 is not met for 1 second. See the specific execution process. Figure 1 As shown.

[0029] When a generator excitation device malfunctions, the excitation current decreases, and the generator cannot maintain its output voltage. After losing excitation, the generator will absorb a large amount of reactive power from the grid, exhibiting a reverse reactive power state. Therefore, excitation current and reactive power are used as judgment conditions to jointly confirm the occurrence of a loss-of-excitation fault.

[0030] The CAN communication status judgment logic is as follows: the generator sends an excitation current message to the integrated protection device every 500ms. After receiving a correct message, the excitation current is extracted, indicating that the CAN communication is normal; if the generator's excitation current message is not received for more than 2 seconds, the CAN communication is judged to be abnormal.

[0031] The embodiments described above merely illustrate specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for protecting a marine generator from loss of excitation, characterized in that, The current reduction of the generator's excitation current and the generator's reverse reactive power state are combined as the conditions for judging the loss of excitation fault, and the loss of excitation protection action is initiated. Specifically, the steps include the following: 1) The integrated protection device obtains the current excitation current information of the generator through the CAN communication interface; 2) The integrated protection device collects the three-phase voltage and three-phase current at the generator terminals to calculate the reactive power. 3) When the following four conditions are met simultaneously, a demagnetization fault is determined to have occurred, and alarm and protection actions are executed: Condition 1: 0 < excitation current Im < excitation current threshold Iset; Condition 2: Reactive power Q < 0 and |reactive power Q| < reactive power threshold Qset; Condition 3: CAN communication interface is functioning normally; Condition 4: Conditions 1, 2, and 3 are continuously met for more than the protection set delay time Tset; 4) The return condition for demagnetization fault is: any one of the above conditions 1, 2, or 3 is not met for 1 second; The method for judging the communication status of the CAN communication interface is as follows: the generator sends an excitation current message to the integrated protection device every 500ms. After receiving a correct message, the excitation current is extracted, indicating that the CAN communication is normal. If no excitation current message from the generator is received for more than 2 seconds, the CAN communication is deemed abnormal.

2. The method for protecting a marine generator from excitation according to claim 1, characterized in that, The excitation current threshold Iset value is the no-load excitation current of the generator.

3. The method for protecting a marine generator from excitation according to claim 1, characterized in that, The reactive power threshold Qset value is equal to the generator's rated reactive power.

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