Self-adaptive power grid power supply protection method suitable for ship working condition change

Abstract

The invention relates to a self-adaptive power grid power supply protection method suitable for ship working condition change, which establishes a directional overcurrent protection system based on composite voltage locking, is used for self-adaptive system working condition change under the conditions of power flow direction change and large-capacity different-power ratio of a grid unit, and realizes sensitivity and selectivity of protection. A power direction judgment element and a voltage judgment element are added to a high-capacity different-power-ratio unit line to judge whether overcurrent protection is enabled or not, so that self-adaptive direction overcurrent protection and self-adaptive composite voltage overcurrent protection of a high-capacity different-power-ratio unit in different operation modes are realized; the power grid power supply protection problem of a ship complex power supply network structure is solved.

Description

Technical Field

[0001] The present invention relates to the field of power supply system protection, and in particular to an adaptive power grid power supply protection method suitable for changes in ship operating conditions. Background Art

[0002] Traditional ship power grids use dry-feed power supply networks. In this network, the power supply path of load equipment is single, and the topology structure does not change much under different working conditions. The power supply protection of the power grid is mainly based on the current-time principle. The current setting value determined based on the current-time principle usually ensures the selectivity of the protection action according to the maximum operating mode, and verifies the sensitivity of the protection action according to the minimum operating mode. The protection scheme needs to take into account the selectivity and sensitivity of the protection action. However, if the system operating mode changes greatly, it will be difficult to take into account the requirements of selectivity and sensitivity. Especially in the minimum operating mode, the protection may refuse to operate.

[0003] The dry-feed grid layout is feasible when the grid power supply protection is based on the current-time principle when the network scale is small. However, with the continuous development of ships and the increase in electrical equipment, its disadvantages are gradually emerging, such as the airtightness problem between cabins caused by too many cables passing through the cabin. Therefore, the ring grid came into being. While shortening the power supply path, it also greatly improved the power supply continuity of the ship's power supply system and the vitality and combat effectiveness of the ship. However, the overcurrent protection based on the current-time principle can no longer fully adapt to the ring power supply network, and it is necessary to propose a new protection strategy suitable for complex power supply network structures.

[0004] Adaptive protection can adjust the protection performance in real time according to the changes of the grid structure and operation mode, and has been developed for many years in land power grids. Ships have multiple operation modes such as berthing, cruising, fighting, and anchoring, and the original grid topology may be destroyed due to fighting. In order to ensure that the ship protection system can perform the protection function normally in multiple operation modes, it is particularly important to realize the application of the adaptive protection concept of land power grid in the ship protection system. Summary of the invention

[0005] Aiming at the power supply protection problem of the above-mentioned complex power supply network structure, an adaptive power supply protection method suitable for changing ship operating conditions is proposed.

[0006] The technical solution of the present invention is: an adaptive power grid power supply protection method suitable for ship operating condition changes, specifically comprising

[0007] 1) Power supply status: Under normal circumstances, the power direction of the emergency jumper line flows from the main busbar to the emergency busbar; in the emergency mode, the power direction flows from the emergency busbar to the main busbar; a short-circuit power direction element is installed in the protection device of the emergency jumper line to enable the protection setting to be put into use, so as to realize adaptive overcurrent protection with different setting groups to adapt to the changes in the system operation mode. Specifically, when the single-phase current setting judgment and the corresponding direction judgment in the protection device of the emergency jumper line are both satisfied and the PT line is not locked, the output is output to accumulate the action time, and the tripping action is performed when any action time of the three phases is reached;

[0008] 2) Line status at fault: when a short circuit occurs when the high-power power generation module supplies power to the system, the voltage on the main jumper and bus tie lines decreases, and the current increases; when a short circuit occurs when the emergency ordinary power generation module supplies power to the system, the voltage on the main jumper and bus tie lines decreases, and the current increases; on the basis of the protection devices of the main jumper, bus tie and other lines, composite voltage elements are added to realize the adaptive composite voltage directional overcurrent protection that unifies the setting group to adapt to the system operation mode, specifically: when both the single-phase current setting judgment and the composite voltage judgment criteria in the protection device of the non-emergency jumper line are met, and the PT line is not locked, the output is used to accumulate the action time, and the tripping action is performed when the action time of any one of the three phases is reached.

[0009] Furthermore, the adaptive overcurrent protection implementation method in 1) is as follows: the overcurrent short-time delay protection detects the overcurrent and disconnects it step by step through a time-limited step delay, starting from the power supply end according to the power supply direction, and passing through the protection switches in sequence along the line, and finally to the main switch of the unit, delaying and disconnecting step by step, so as to achieve coordination and cooperation between the upper and lower level protections.

[0010] Furthermore, the composite voltage element in 2) is composed of a negative-sequence voltage element and a phase-to-phase low-voltage element, which form an OR logic, wherein the negative-sequence voltage element can sensitively reflect the asymmetric short circuit of two phases in the system, and the low-voltage element can sensitively reflect the symmetrical short circuit of three phases in the system.

[0011] Further, the adaptive composite voltage direction overcurrent protection implementation method in 2) is as follows: the adaptive composite voltage and overcurrent protection of the busbar and the main crossover unifies the protection current setting groups of the two different power supply modes of the high-power generation module and the emergency ordinary generation module through the following table, where I DG is the rated current of the diesel generator set, U is the system’s arbitrary phase-to-phase voltage, U n is the rated voltage of the power supply system, U2 is the negative sequence voltage of the system,

[0012]

[0013]

[0014] The beneficial effects of the present invention are as follows: the present invention is applicable to an adaptive power grid power supply protection method for changes in ship operating conditions, establishes a directional overcurrent protection system based on composite voltage blocking, and is used to adapt to changes in system operating conditions under changes in power flow direction and large-capacity power ratios of network units, thereby achieving protection sensitivity and selectivity. By adding power direction discrimination elements and voltage discrimination elements to the lines of large-capacity power ratio units to determine whether overcurrent protection is enabled, adaptive directional overcurrent protection and adaptive composite voltage overcurrent protection of large-capacity power ratio units in different operating modes can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram of an exemplary power supply network and adaptive directional overcurrent protection of the present invention;

[0016] Figure 2 This is a schematic diagram of the adaptive directional overcurrent protection principle of the present invention;

[0017] Figure 3 This is a schematic diagram of the composite voltage overcurrent protection principle of the present invention. DETAILED DESCRIPTION

[0018] 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.

[0019] The present invention discloses an adaptive protection technology suitable for ship operating condition changes, based on a directional overcurrent protection system with composite voltage blocking, which is used to realize the sensitivity and selectivity of protection when the power flow direction changes and the operating condition changes of the adaptive system under the condition of large capacity and different power ratio of the network unit. By adding power direction discrimination elements and voltage discrimination elements to the line of the large capacity and different power ratio unit to judge whether the overcurrent protection is enabled, the adaptive directional overcurrent protection and adaptive composite voltage overcurrent protection of the large capacity and different power ratio unit under different operating modes can be realized.

[0020] Take the power supply network structure of a ship as an example. Figure 1 As shown, two high-power generation module power stations are set up in the power supply network, each power station is equipped with two high-power generation modules (TG) and two sets of medium-voltage main switchboard control panels. In order to improve the power supply continuity of the power supply network, the main busbar of each high-power generation module is connected to the emergency busbar of the emergency general generation module (DG) through an emergency jumper line to supply power to the emergency load of the entire ship when the power supply capacity of the high-power generation module is lost. Among them, the capacity of the emergency general generation module is much smaller than that of the high-power generation module. Under the same voltage level, the current of the emergency general generation module is much smaller than that of the high-power generation module.

[0021] (1) In normal mode, the entire ship's load is powered by the high-power power generation module; in emergency mode, the entire ship's emergency load is powered by the emergency general power generation module.

[0022] (2) If the power supply network only adopts overcurrent protection based on the current-time principle, the protection setting value cannot be unified when different power units supply power to the power supply network in normal mode and emergency mode.

[0023] (3) Power supply status: Under normal circumstances, the power direction of the emergency jumper line flows from the main busbar to the emergency busbar. In emergency mode, the power direction flows from the emergency busbar to the main busbar.

[0024] (4) Line status at the time of fault: when a short circuit occurs when the high-power power generation module is supplying power to the system, the voltage on the main jumper and bus tie lines decreases and the current increases; when a short circuit occurs when the emergency ordinary power generation module is supplying power to the system, the voltage on the main jumper and bus tie lines decreases and the current increases.

[0025] (5) Based on the situation (3), a short-circuit power directional element can be added to the protection device of the emergency jumper line to enable the protection setting to be activated to realize adaptive overcurrent protection with different setting groups to adapt to changes in system operation mode. The protection principle of adaptive directional overcurrent protection is as follows: Figure 2 As shown, when the single-phase current setting judgment and the corresponding direction judgment in the protection device of the emergency jumper line both meet (and), and the PT line is broken and not locked, the output is used to accumulate the action time. When any action time of the three phases is reached (or), the tripping action is performed.

[0026] (6) Based on the situation in (4), the protection devices of the main jumper, busbar and other lines can be equipped with composite voltage elements on the basis of (5) to achieve adaptive composite voltage directional overcurrent protection that can adapt to the system operation mode by unifying the setting group. The principle of adaptive composite voltage directional overcurrent protection is as follows: Figure 3 As shown, in the protection device of the non-emergency jumper line, both the single-phase current setting judgment and the composite voltage judgment criteria are satisfied (and), and the PT line is broken and not locked, the output is used to accumulate the action time, and the tripping action is performed when any action time of the three phases is reached (or).

[0027] Specific implementation of (5) and (6):

[0028] Adaptive directional overcurrent protection:

[0029] The overcurrent short-time delay protection detects overcurrent and disconnects it step by step through the time-limited step delay. It starts from the power supply end according to the power supply direction, passes through the protection switches in sequence along the line, and finally disconnects the main switch of the unit step by step to achieve coordination between the upper and lower protections. After the emergency jumper switch is configured with adaptive directional overcurrent protection, the coordination between the upper and lower protections of the system can be achieved through Figure 1 Further explanation:

[0030] a. It is stipulated that the short-circuit power direction at the emergency jumper QF1 is from the medium-voltage main bus to the line in the positive direction (as shown by the blue arrow). Only when it is judged to be powered in the positive direction, the overcurrent protection of the emergency jumper QF1 is enabled, thereby forming a step time limit characteristic of "emergency jumper switch t+Δt→bus tie switch t+2Δt→main jumper switch t+3Δt→high-power generation module switch t+4Δt" in the high-power generation module power supply mode;

[0031] b. It is stipulated that the direction of short-circuit power at the emergency jumper QF2 is the positive direction from the medium-voltage emergency bus to the line (as shown by the red arrow). Only when it is judged that the power supply is in the positive direction, the overcurrent protection of the emergency jumper QF2 is enabled, thereby forming a step time limit characteristic of "load panel connecting switch t+Δt→main jumper switch t+2Δt→bus tie switch t+3Δt→emergency jumper switch t+4Δt→emergency ordinary power generation module switch t+5Δt" in the emergency ordinary power generation module power supply mode.

[0032] Adaptive composite voltage overcurrent protection:

[0033] The adaptive composite voltage and overcurrent protection of the busbar and main crossover can be described in Table 1 (Adaptive Protection-Setting Group), which unifies the protection current setting groups of the two different power supply modes of the large power generation module and the emergency ordinary generation module. DG is the rated current of the diesel generator set, U is the system’s arbitrary phase-to-phase voltage, U n is the rated voltage of the power supply system, and U2 is the negative sequence voltage of the system.

[0034] Table 1

[0035]

[0036] a. When the high-power generation module is supplying power normally, the integrated protection device does not operate (the voltage criterion is not met, and the setting group is not put into operation), and the protection is reliable and does not operate;

[0037] b. When a short circuit occurs in the power supply system of the high-power generation module, the comprehensive protection device will be activated and the protection will be reliable;

[0038] c. When the emergency ordinary power generation module is supplying power normally, the comprehensive protection device does not operate (the voltage criterion is not met, and the setting group is not put into operation), and the protection is reliable and does not operate;

[0039] d. When a short circuit occurs in the emergency general power generation module power supply system, the comprehensive protection device will be activated and the protection will be reliable.

[0040] The above analysis shows that the use of adaptive composite voltage overcurrent protection for the busbar and main jumper can ensure reliable operation when a fault occurs in different operating modes and reliable non-operation during normal power supply.

[0041] The composite voltage element is composed of a negative-sequence voltage element and a phase-to-phase low-voltage element, which form an OR logic. The negative-sequence voltage element can sensitively reflect the asymmetric short circuit of two phases in the system, and the low-voltage element can sensitively reflect the symmetrical short circuit of three phases in the system.

[0042] 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. An adaptive power grid power supply protection method suitable for ship operating condition changes, characterized in that: Specifically include 1) Power supply status: Under normal circumstances, the power direction of the emergency jumper line flows from the main busbar to the emergency busbar; in the emergency mode, the power direction flows from the emergency busbar to the main busbar; a short-circuit power direction element is installed in the protection device of the emergency jumper line to enable the protection setting to be put into use, so as to realize adaptive overcurrent protection with different setting groups to adapt to the changes in the system operation mode. Specifically, when the single-phase current setting judgment and the corresponding direction judgment in the protection device of the emergency jumper line are both satisfied and the PT line is not locked, the output is output to accumulate the action time, and the tripping action is performed when any action time of the three phases is reached; 2) Line status at the time of fault: when a short circuit occurs when the high-power power generation module supplies power to the system, the voltage on the main jumper and bus tie lines decreases and the current increases; when a short circuit occurs when the emergency ordinary power generation module supplies power to the system, the voltage on the main jumper and bus tie lines decreases and the current increases; Composite voltage elements are installed on the basis of the protection devices of the main jumper, bus tie and other lines to realize the adaptive composite voltage directional overcurrent protection that unifies the setting group to adapt to the system operation mode. Specifically: when both the single-phase current setting judgment and the composite voltage judgment criteria in the protection device of the non-emergency jumper line are met, and the PT line is broken and not locked, the output is used to accumulate the action time. When the action time of any one of the three phases is reached, the tripping action is performed.

2. The adaptive power grid power supply protection method applicable to ship operating condition changes according to claim 1 is characterized in that: The implementation method of the adaptive overcurrent protection in 1) is as follows: the overcurrent short-time delay protection detects the overcurrent and disconnects it step by step through a time-limited step delay, starting from the power supply end according to the power supply direction, and passing through the protection switches in sequence along the line, and finally to the main switch of the unit, and disconnects it step by step with a delay, so as to achieve coordination between the upper and lower protections.

3. The adaptive power grid power supply protection method applicable to ship operating condition changes according to claim 1 is characterized in that: The composite voltage element in 2) is composed of a negative-sequence voltage element and a phase-to-phase low-voltage element, which form an OR logic, wherein the negative-sequence voltage element can sensitively reflect the asymmetric short circuit of two phases in the system, and the low-voltage element can sensitively reflect the symmetrical short circuit of three phases in the system.

4. The adaptive power grid power supply protection method applicable to ship operating condition changes according to claim 3 is characterized in that: The implementation method of the adaptive composite voltage direction overcurrent protection in 2) is as follows: The adaptive composite voltage and overcurrent protection of the busbar and the main crossover unifies the protection current setting groups in two different power supply modes of the high-power generation module and the emergency ordinary generation module through the following table, where I DG is the rated current of the diesel generator set, U is the system’s arbitrary phase-to-phase voltage, U n is the rated voltage of the power supply system, U2 is the negative sequence voltage of the system,

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