Marine power station area protection method with dead zone protection

Abstract

The present invention relates to a marine power station area protection method with dead zone protection. The newly added bus differential protection can correctly identify the faults inside and outside the bus area of ​​the busbar, and can effectively identify the arcing fault in the cable room of the distribution board as an out-of-area short circuit, solving the protection dead zone problem of arc protection; adding bus dead zone protection solves the bus protection dead zone problem between the current transformer and the circuit breaker; bus differential protection and arc protection are used as two sets of main protection for bus protection, and the two sets of main protection are exported through the "AND" gate to ensure that the bus protection is reliable and does not malfunction. In this way, the hazards of busbar faults can be reduced and the expansion of the fault area can be effectively prevented.

Description

Technical Field

[0001] The present invention relates to the technical field of power protection, and in particular to a method for protecting a ship power station area with dead zone protection. Background Art

[0002] At present, the load capacity of ship electrical equipment has increased significantly. Many large ships have adopted medium-voltage AC power systems. The system structure is becoming more and more complex, and higher requirements are placed on the reliability, speed and reliability of ship power system protection.

[0003] Among the various types of short-circuit faults in the medium-voltage AC power system of ships, the possibility of busbar short-circuit faults is relatively small, but the harm after it occurs is extremely great, and it may cause arcing in the switchboard. The causes of busbar short circuits include aging of switchboard insulators, failure of voltage and current transformers in the switchboard, and rodent infestation in the cabin. As the power flow convergence point of the system and the hub for distributing electric energy, the busbar connects generators, various medium-voltage loads, load centers, and lines connecting other power stations. Once it is mistakenly cut off without fault, it will cause a large-scale power outage in the system. When a busbar short-circuit fault occurs and is not removed in time, the internal fault arcing will continue to burn the switchboard and release huge energy, damaging the components in the switchboard and posing a serious threat to the safety of the crew.

[0004] Differential relays have been used in generator protection, line protection, and grounding protection in ship power systems, but have not yet covered busbar protection. Differential protection can be used as the main protection for busbar differential protection, but formal differential protection alone cannot fully meet the selectivity requirements. It is necessary to further analyze the characteristics of busbar short-circuit faults and increase the reliability of busbar protection.

[0005] Currently, there are three main countermeasures for busbar short-circuit faults: arc protection, short-delay overcurrent protection, and busbar protection.

[0006] Arc protection is a sensitive and fast form of protection. It relies on optical probes to detect arc faults released by arcing inside the distribution board. In order to improve the reliability of arc protection, arc monitoring equipment generally has two input signal channels, one is the current signal channel, and the other is the arc signal channel. The protection uses arc and current signal dual judgment criteria. When the equipment detects arcing in a certain medium-voltage room (busbar room, circuit breaker room, cable room), and at the same time detects a surge in current value of at least one way, it is judged as an arcing fault, and then a trip signal is sent to the corresponding circuit breaker. Arc protection has a significant disadvantage, that is, there is a large area of ​​protection dead zone. When arcing occurs in the cable room, the arc protection will trip the circuit breakers connected to the busbar, causing all loads on this section of the busbar to lose power, resulting in the expansion of the fault area, so it is called the protection dead zone of arc protection.

[0007] The short-delay overcurrent protection is based on the short-delay protection in the three-stage overcurrent protection. It relies on the delay coordination to realize the step-by-step disconnection of each circuit breaker connected to the busbar. This method will generally cause the arc in the cabinet to last for hundreds of milliseconds before the fault can be disconnected. It does not help to suppress damage to the cabinet. At the same time, it puts forward high requirements on the tolerance of the distribution board itself, so it can only be used as backup protection.

[0008] Busbar protection is a special busbar protection for busbar faults, which can be realized based on microcomputer protection and differential protection principle. As a protection form with excellent speed and selectivity, differential protection has gained operating experience in generator protection, line protection and grounding protection in ship power systems, but the main protection system of ship power systems composed of differential protection has not yet covered busbars. Summary of the invention

[0009] Aiming at the problems of busbar protection speed, selectivity and dead zone protection, a ship power station regional protection method with dead zone protection is proposed to reduce the harm of busbar fault and effectively prevent the expansion of fault area.

[0010] The technical solution of the present invention is: a method for protecting a marine power station area with dead zone protection, wherein the newly added bus differential protection and the existing arc protection are used together as two sets of main protection for bus protection, and the two sets of main protection jointly realize bus protection through an "AND" gate, wherein the bus differential protection realization method is:

[0011] The main busbar and its connected branches are divided into different protection areas. The area to which the main busbar belongs is independently equipped with a set of bus differential protection, and other areas are equipped with differential protection as the main protection for phase-to-phase short circuit in the area;

[0012] The operating characteristics of busbar differential protection are as follows:

[0013]

[0014] In the formula, is the current flowing into the busbar from branch j connected to the busbar; n is the total number of branches connected to the busbar; I qd To protect the starting threshold; K r is the ratio braking coefficient;

[0015] The two conditions in formula (3) are satisfied to form the action characteristics of bus differential protection, indicating that a fault occurs in the area. At this time, the action current of the differential protection is the short-circuit current at the fault point, and the differential protection can be reliably operated.

[0016] The current transformer TA is installed in the connection section between each branch and the main busbar, and in the corresponding area outside the branch circuit breaker adjacent to the main busbar. This is the busbar dead zone of the busbar differential protection.

[0017] The busbar dead zone protection method is:

[0018] 1) After judging the action characteristics of the busbar differential protection, the regional differential protection is judged as an internal fault and the corresponding protection action is performed;

[0019] 2) If the fault is in the bus dead zone, that is, the fault has not been eliminated, the faulty bus current transformer will always have current flowing through it. At this time, the bus differential protection and overcurrent protection will not return, and the protection device can accurately determine that the fault is in the dead zone;

[0020] 3) Busbar dead zone protection after setting delay t sq After that, the busbar current transformer where the fault is located is blocked, and the busbar current in this area is not included in the busbar differential protection, that is, the busbar current in this area is removed from the action characteristic judgment equation (3) of the busbar differential protection. The busbar differential protection can continue to judge it as an internal fault, and trip the branch circuit breakers connected to the busbar to achieve fault removal.

[0021] Furthermore, the protection start threshold I qd And the ratio braking characteristic K r , it is set according to the transmission error caused by the different current transformer characteristics of each busbar connection element.

[0022] A protection system for realizing a marine power station area protection method with dead zone protection includes:

[0023] Local comprehensive protection unit: collects local voltage and current analog signals and switch signals, and transmits them point-to-point to the upper-layer merging unit MU in the form of messages through the optical fiber serial port; receives the action instructions issued by the upper-layer merging unit to control the local circuit breaker; the local comprehensive protection unit is also responsible for realizing the equipment protection of the generator, transformer, and line unit level of this branch;

[0024] Merging unit MU: As the extended acquisition front end of the comprehensive security device centralized control unit, it synchronizes and merges the multi-channel sampling data uploaded by the local comprehensive security unit, and then transmits it point-to-point to the comprehensive security centralized control unit in the form of messages through the optical fiber serial port; receives the action instructions of the comprehensive security centralized control unit and sends them to the local comprehensive security unit;

[0025] Comprehensive protection centralized control unit: the decision-making center of bus differential protection, one set is set for each section of medium-voltage bus, which performs centralized logic judgment and action output of bus differential protection. The action instructions are sent point-to-point to the merging unit in the form of messages through the optical fiber serial port; each power station panel of the medium-voltage main distribution board control panel is equipped with one comprehensive protection centralized control unit and two merging units to realize bus differential protection.

[0026] The beneficial effects of the present invention are as follows: the present invention has a marine power station area protection method with dead zone protection, the bus differential protection can correctly identify the busbar faults inside and outside the area, and can effectively identify the arcing fault in the cable room of the distribution board as an outside short circuit, which solves the protection dead zone problem of arc protection; the bus dead zone protection is added to solve the bus protection dead zone problem between the current transformer and the circuit breaker; the bus differential protection and arc protection are used together as two sets of main protections for bus protection, and the two sets of main protections are exported through the "AND" gate to ensure that the bus protection is reliable and does not malfunction. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the division of the busbar protection area of ​​the power supply network of the present invention;

[0028] Figure 2 It is the action characteristic diagram of the busbar protection of the present invention;

[0029] Figure 3 This is a schematic diagram of the implementation form of the bus differential protection of the present invention;

[0030] Figure 4 This is a schematic diagram of determining the direction element of the present invention. DETAILED DESCRIPTION

[0031] 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.

[0032] This paper invented a method for regional protection of ship power stations with dead zone protection. Based on the photoelectric signal, the electrical information of nodes in each power station area is collected, which is used to quickly and reliably remove the fault when a fault occurs in the bus area to avoid expanding the fault range and causing large-scale power outages. At the same time, with the help of bus dead zone protection, the problem that the bus dead zone is difficult to be covered by protection when a fault occurs is solved. The reliability of regional protection technology is improved by coordinating with arc protection and anti-current transformer saturation measures.

[0033] Take a typical ship power supply network as an example Figure 1 As shown, the specific implementation plan of busbar protection is introduced.

[0034] The main busbar and its connected branches are divided into different protection areas, denoted as Area 1 to Area 10. Figure 1 As shown, the main busbar (area 1) is independently configured with a set of bus differential protection, and other areas are configured with differential protection as the main protection for phase-to-phase short circuit in the area.

[0035] Different from line differential protection and generator differential protection, the current input to bus differential protection has multi-port characteristics. Bus differential protection takes the current phasor sum of each connected branch flowing into the bus as the differential current I d , the scalar sum of each branch current is taken as the braking current I r .

[0036]

[0037] The operating characteristics of the busbar differential protection are as follows:

[0038]

[0039] In the formula, is the current flowing into the busbar from branch j connected to the busbar; n is the total number of branches connected to the busbar; I qd To protect the starting threshold; K r is the ratio braking coefficient. Both conditions in formula (3) are satisfied to form the action characteristics of bus differential protection. When the bus operates normally or an out-of-zone fault occurs, the current flowing into the bus should be equal to the current flowing out of the bus. When the transmission error of the current transformer is not considered, the action current of the differential protection is 0. In actual situations, the current transformer characteristics of each bus connection element are different, and the transmission error constitutes the differential current. Therefore, the protection start threshold I is set. qd And the ratio braking characteristic K r .

[0040] The operating characteristics of busbar differential protection are as follows: Figure 2 As shown, Figure 2 The middle shaded area is the action area. Therefore Figure 2 The area above the action curve with a slope of 1 is outside the definition domain. When the busbar is operating normally or an out-of-area fault occurs, the current flowing into the busbar should be equal to the current flowing out of the busbar. When the transmission error of the current transformer is not considered, the action current of the differential protection is 0. In actual situations, the current transformer characteristics of each busbar connection element are different, and the transmission error constitutes the differential current, so the action threshold I is set. qd And the ratio braking characteristic K r When a busbar fault occurs, the current of each connected unit flows into the busbar. At this time, the action current of the differential protection is the short-circuit current at the fault point, and the differential protection can be reliably operated. As a unit protection, the protection range of the differential protection is defined by the value collected by the current transformer TA (such as Figure 1 As shown in the figure, TA should generally be located in the connection section between each branch and the main busbar, and in the corresponding area outside the branch circuit breaker adjacent to the main busbar.

[0041] When a busbar fault occurs, the current of each connected unit flows into the busbar. At this time, the action current of the differential protection is the short-circuit current at the fault point, and the differential protection can be reliably operated. Therefore, the busbar differential protection can effectively identify the arcing fault in the cable room of the distribution board as an out-of-zone short circuit, solving the protection dead zone problem of arc protection.

[0042] Busbar protection adopts Figure 3 The implementation shown mainly includes the following devices:

[0043] (1) Local comprehensive protection unit: collects local voltage and current analog signals and switch signals, and transmits them point-to-point to the upper-layer merging unit (MU) in the form of messages through the optical fiber serial port; receives the action instructions issued by the upper-layer merging unit to control the local circuit breaker. The local comprehensive protection unit is also responsible for realizing the unit-level equipment protection of the generator, transformer, line, etc. of this branch;

[0044] (2) Merging Unit (MU): As the extended acquisition front end of the comprehensive security device centralized control unit, it synchronizes and merges the multi-channel sampling data uploaded by the local comprehensive security unit, and then transmits it point-to-point to the comprehensive security centralized control unit in the form of messages through the optical fiber serial port; receives the action instructions of the comprehensive security centralized control unit and sends them to the local comprehensive security unit;

[0045] (3) Integrated protection centralized control unit: the decision center of bus differential protection. One set is set for each medium-voltage bus. It performs centralized logic judgment and action output of bus differential protection. The action command is sent point-to-point to the merging unit in the form of a message through the optical fiber serial port. Each power station panel of the medium-voltage main switchboard control panel is equipped with one integrated protection centralized control unit and two merging units to realize the bus differential protection function.

[0046] like Figure 1 As shown, when a fault occurs at F-A1, the bus differential protection composed of current transformers TA-G3, TA-M1, TA-X1 to TA-X7 as inputs will significantly determine that F-A1 is an internal fault, and disconnect QF-G3, QF-M1, QF-X1 to QF-X7 to clear the fault; when a fault occurs at F-SM, the bus differential protection is determined to be an out-of-zone fault, while the area 3 differential protection composed of TA-M1 and TA-M2 as inputs is determined to be an internal fault, and disconnects QF-M1 and QF-M2 to clear the fault.

[0047] The input of bus differential protection is collected by current transformer TA, that is, the protection range is defined by the transformer, and the fault is disconnected by medium voltage circuit breaker QF. Due to the layout of the cabinet, there is inevitably a small section of busbar between the transformer TA and the circuit breaker QF inside the medium voltage distribution board, such as Figure 1When faults occur at F-SG, F-SM, F-S1 to F-S7 in the busbar, the busbar differential protection will fail and cannot cover these fault locations.

[0048] Take the fault at the busbar F-SM as an example for analysis. Figure 1 From the above, it can be seen that the minimum means of isolating the fault is to disconnect QF-G3, QF-M1, QF-X1 to QF-X7, but Figure 1 It can be seen that at this time, the bus differential protection of area 3 will be judged as an internal fault and disconnect QF-M1 and QF-M2, but the fault is not actually removed. At the same time, since the bus differential protection range of area 1 cannot cover F-SM, it will always be judged as an external fault, so F-SM is called the bus protection dead zone. Figure 1 F-SG, F-S1 to F-S7 are also busbar protection dead zones.

[0049] The solution to the bus dead zone fault needs to be supplemented by bus dead zone protection. Taking the fault at the bus coupler F-SM as an example, its action logic is:

[0050] 1) The differential protection of area 3 is judged as an internal fault, and the busbar circuit breakers QF-M1 and QF-M2 are tripped;

[0051] 2) Since the fault has not actually been cleared, current will always flow through the bus-coupler transformer TA-M1. At this time, the bus-coupler differential protection and overcurrent protection will not return, and the protection device can accurately determine that the fault is in the dead zone;

[0052] 3) Busbar dead zone protection after setting delay t sq After that, the busbar current transformer TA-M1 is blocked, and the busbar current in this area 3 is not included in the busbar differential protection, that is, the busbar current in this area 3 is withdrawn from the action characteristic judgment equation of the busbar differential protection (Formula (3)). The busbar differential protection can continue to judge it as an internal fault, and trip the branch circuit breakers connected to the busbar to achieve fault removal.

[0053] The present invention uses bus differential protection and arc protection as two sets of main protection for bus protection. The two sets of main protection are connected through the "AND" gate to prevent false operation due to interference at the same time, and try to improve the reliability of protection without false operation. At this time:

[0054] 1) When arcing occurs in the cable compartment of the distribution board, such as Figure 4 , the busbar differential protection is judged as an out-of-zone fault, and the busbar protection will not malfunction; the line differential is identified as an in-zone fault, and the fault is quickly removed, effectively solving the problem of busbar protection selectivity when arcing in the cable room;

[0055] 2) Consider the extreme case where the arc light generated by arcing in the cable room leaks to the adjacent circuit breaker room and busbar room. Figure 4, it may trigger the arc protection to malfunction, but at this time the bus differential protection can be effectively judged as an out-of-zone fault and will not operate. After the two are exported through the "AND" gate, it can ensure that the bus protection is reliable and will not malfunction, effectively improving the reliability and selectivity of the bus protection under extreme conditions.

[0056] 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 ship power station area with dead zone protection, characterized in that: The newly added bus differential protection and the existing arc protection are used as two sets of main protection for bus protection. The two sets of main protection realize bus protection through "AND" gate. The bus differential protection is realized as follows: The main busbar and its connected branches are divided into different protection areas. The area to which the main busbar belongs is independently equipped with a set of bus differential protection, and other areas are equipped with differential protection as the main protection for phase-to-phase short circuit in the area; The operating characteristics of busbar differential protection are as follows: In the formula, is the current flowing into the busbar from branch j connected to the busbar; n is the total number of branches connected to the busbar; I qd To protect the starting threshold; K r is the ratio braking coefficient; The two conditions in formula (3) are satisfied to form the action characteristics of bus differential protection, indicating that a fault occurs in the area. At this time, the action current of the differential protection is the short-circuit current at the fault point, and the differential protection can be reliably operated. The current transformer TA is installed in the connection section between each branch and the main busbar, and in the corresponding area outside the branch circuit breaker adjacent to the main busbar. This is the busbar dead zone of the busbar differential protection. The busbar dead zone protection method is: 1) After judging the action characteristics of the busbar differential protection, the regional differential protection is judged as an internal fault and the corresponding protection action is performed; 2) If the fault is in the bus dead zone, that is, the fault has not been eliminated, the faulty bus current transformer will always have current flowing through it. At this time, the bus differential protection and overcurrent protection will not return, and the protection device can accurately determine that the fault is in the dead zone; 3) Busbar dead zone protection after setting delay t sq After that, the busbar current transformer where the fault is located is blocked, and the busbar current in this area is not included in the busbar differential protection, that is, the busbar current in this area is removed from the action characteristic judgment equation (3) of the busbar differential protection. The busbar differential protection can continue to judge it as an internal fault, and trip the branch circuit breakers connected to the busbar to achieve fault removal.

2. The method for protecting a ship power station area with dead zone protection according to claim 1, characterized in that: The protection start threshold I qd And the ratio braking characteristic K r , it is set according to the transmission error caused by the different current transformer characteristics of each busbar connection element.

3. A protection system for realizing the ship power station area protection method with dead zone protection according to claim 1 or 2, characterized in that: include: Local comprehensive protection unit: collects local voltage and current analog signals and switch signals, and transmits them point-to-point to the upper-layer merging unit MU in the form of messages through the optical fiber serial port; Receive action instructions from the upper-layer merging unit to control the local circuit breaker; the local comprehensive protection unit is also responsible for implementing the equipment protection of the generator, transformer, and line unit level of this branch; Merging unit MU: As the extended acquisition front end of the comprehensive security device centralized control unit, it synchronizes and merges the multi-channel sampling data uploaded by the local comprehensive security unit, and then transmits it point-to-point to the comprehensive security centralized control unit in the form of messages through the optical fiber serial port; receives the action instructions of the comprehensive security centralized control unit and sends them to the local comprehensive security unit; Comprehensive protection centralized control unit: the decision-making center of bus differential protection, one set is set for each section of medium-voltage bus, which performs centralized logic judgment and action output of bus differential protection. The action instructions are sent point-to-point to the merging unit in the form of messages through the optical fiber serial port; each power station panel of the medium-voltage main distribution board control panel is equipped with one comprehensive protection centralized control unit and two merging units to realize bus differential protection.

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