Field loss protection method for marine generator

Abstract

The invention relates to an excitation loss protection method for a marine generator, which combines the current excitation current reduction of the generator and the inverse reactive power state of the generator as an excitation loss fault judgment condition, and enters an excitation loss protection action. Field loss faults can be quickly and accurately identified, and safety and stability risks of the system caused by asynchronous phase operation of the generator can be avoided; the blank of field loss protection of the current high-power marine generator set is filled; the reliability of power supply of a marine power system is improved, and potential safety hazards caused by magnetic loss of the generator are avoided.

Description

Technical Field

[0001] The invention relates to the technical field of ship power system protection, and in particular to a demagnetization protection method for a ship generator. Background Art

[0002] At present, the integrated marine protection device has realized the full digital mode, and generally has the protection functions of differential protection, overcurrent protection, voltage protection, zero sequence protection, frequency protection, etc. For marine generator protection, differential protection, overcurrent protection, voltage protection, zero sequence protection, frequency protection, and reverse power protection are generally configured at present to ensure that the main switch of the generator is quickly cut off when a short circuit or abnormal state occurs, and to ensure the reliability and continuity of the power supply of the power system. For high-power marine generator sets, demagnetization protection is not yet configured. When the unit has a demagnetization fault, it may bring safety risks to the operation of the power system. Summary of the invention

[0003] Aiming at the problem of demagnetization fault of generator set, a demagnetization protection method for marine generator is proposed.

[0004] The technical solution of the present invention is: a demagnetization protection method for a marine generator, which combines the current excitation current reduction of the generator and the reverse reactive power state of the generator as demagnetization fault judgment conditions to enter the demagnetization protection action.

[0005] The marine generator demagnetization protection method specifically comprises 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 end to calculate the reactive power;

[0008] 3) When the following four conditions are met at the same time, it is determined that a demagnetization fault has occurred, and an alarm and protection action output 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 communication is normal;

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

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

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

[0015] Furthermore, the value of the reactive power threshold Qset is the rated reactive power of the generator.

[0016] Furthermore, 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, and extracts the excitation current after receiving the correct message, which means that the CAN communication is normal; when the excitation current message of the generator is not received for more than 2s, it is determined that the CAN communication is abnormal.

[0017] The beneficial effects of the present invention are as follows: the demagnetization protection method for a marine generator of the present invention can quickly and accurately identify demagnetization faults, thereby preventing the generator from changing to asynchronous phase-forward operation and bringing safety and stability risks to the system; it fills the gap in the current demagnetization protection of high-power marine generator sets; it improves the reliability of power supply of a marine power system and avoids the safety hazards caused by demagnetization of the generator. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a flow chart of the execution of the demagnetization protection method for a marine generator of the present invention. DETAILED DESCRIPTION

[0019] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0020] A method for protecting marine generators from demagnetization by comprehensively utilizing the operating quadrant characteristics of the generator excitation current and the reactive power at the machine end is invented:

[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 end to calculate the reactive power;

[0023] (3) When the following four conditions are met at the same time, it is determined that a demagnetization fault has occurred, and an alarm and protection action output are executed:

[0024] Condition 1: 0<excitation current Im<excitation current threshold Iset, the value of the 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, the value of reactive power threshold Qset is the rated reactive power of the generator;

[0026] Condition 3: CAN communication interface communication is normal;

[0027] Condition 4: Continuously meet conditions 1, 2, and 3 for more than the protection setting delay time Tset. The protection setting delay time Tset is generally set in the range of 5s to 10s.

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

[0029] When the excitation device of the generator fails, the excitation current decreases, the generator cannot maintain the output voltage, and the generator will absorb a large amount of reactive power from the power grid after demagnetization, showing a reverse reactive power state. Therefore, the excitation current and reactive power are used as judgment conditions to jointly confirm that a demagnetization fault has occurred.

[0030] The CAN communication status judgment logic is: the generator sends an excitation current message to the integrated protection device every 500ms, and extracts the excitation current after receiving the correct message, which means the CAN communication is normal; when the excitation current message of the generator is not received for more than 2s, the CAN communication is judged to be abnormal.

[0031] The above-mentioned embodiments only express the specific implementation of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. A method for protecting a marine generator from demagnetization, characterized in that: The current excitation current reduction of the generator and the reverse reactive power state of the generator are combined as the demagnetization fault judgment conditions to enter the demagnetization protection action.

2. The method for protecting a marine generator from demagnetization according to claim 1, characterized in that: The specific steps include: 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 end to calculate the reactive power; 3) When the following four conditions are met at the same time, it is determined that a demagnetization fault has occurred, and an alarm and protection action output 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 communication is normal; Condition 4: Conditions 1, 2, and 3 are continuously met and exceed the protection delay time Tset; 4) The return condition for demagnetization fault is: any one of the above conditions 1, 2, and 3 is not met for 1 second.

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

4. The method for protecting a marine generator from demagnetization according to claim 2, characterized in that: The value of the reactive power threshold Qset is the rated reactive power of the generator.

5. The method for protecting a marine generator from demagnetization according to claim 2, characterized in that: 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, and extracts the excitation current after receiving the correct message, indicating that the CAN communication is normal; When the excitation current message of the generator is not received for more than 2 seconds, it is determined that the CAN communication is abnormal.

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