Open logic control method and device for over-current protection in re-voltage locking direction of transformer

Abstract

The invention discloses a method and a device for controlling over-current protection open logic in a repressing locking direction of a transformer, and the open logic of the repressing locking direction of the transformer meets any one of the following conditions: when the two conditions of the action of a combined voltage element at the side and no PT disconnection or PT quit at the side are met at the same time, the repressing action at the side is carried out, and the element should be normally opened; the composite voltage elements on the other sides act, TWJ of the other sides is not equal to 1, when TWJ = 1, the switch is in an off position, and when TWJ = 0, the switch is in an on position; therefore, only when other sides are closed and the re-voltage is opened, the re-voltage of the side can receive voltage opening signals of the other sides, so that the re-voltage over-current protection of the side can reliably act when a fault occurs; when the PT on each side is broken or the voltage pressing plate is not switched on, the protection on the side cannot receive the voltage on each side, and the re-pressing element is opened. The re-pressing over-current direction protection action needs to meet three conditions of re-pressing opening, direction element opening and over-current element action at the same time. The load scheduling flexibility is improved, and the risk that operation and maintenance personnel mistakenly put and withdraw the voltage pressing plate is eliminated.

Description

Technical Field

[0001] The invention relates to a transformer re-pressure locking direction overcurrent protection opening logic control method and device, belonging to the technical field of power grid relay protection. Background Art

[0002] The transformer re-pressure lockout overcurrent protection is not only the backup protection for the transformer main protection, but also the backup protection for the phase-to-phase short-circuit fault of the adjacent busbar or line. The protection principle is relatively complex and involves many pressure plate operations. When the main transformer operation mode is adjusted, in order to ensure the correct action of the protection, the operation and maintenance personnel need to timely put in and out the relevant voltage pressure plates, which affects the flexibility of the grid load dispatching. At the same time, the wrong putting in and out of the pressure plate may cause the fault to be removed in time and the protection to malfunction.

[0003] In order to improve the flexibility of power grid dispatching, enhance the efficiency of operation and maintenance, and reduce the risk of personnel operating the pressure plate, an improved transformer re-pressure locking direction overcurrent protection opening logic is proposed. Summary of the invention

[0004] The purpose of the present invention is to provide a method and device for controlling the open logic of overcurrent protection in the direction of transformer re-voltage locking, which aims to improve the flexibility of load scheduling and eliminate the risk of operation and maintenance personnel mistakenly switching on and off the voltage pressure plate.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A transformer re-voltage locking direction overcurrent protection open logic control method, comprising:

[0007] The composite voltage opening logic meets any of the following conditions, that is, the composite voltage element is opened:

[0008] 1.1 When the two conditions of the composite voltage element on this side acting and the PT on this side not being disconnected or exiting are met at the same time, the composite voltage element on this side acts and the element should open normally;

[0009] 1.2 The composite voltage element on the other side is actuated and TWJ on the other side is ≠1. The TWJ is a trip position relay. When TWJ=1, it indicates that the switch is in the open position, and when TWJ=0, it indicates that the switch is in the closed position. This means that only when the other side is in the closed position and the re-pressure is open, the re-pressure on this side will receive the voltage opening signal on the other side, so that the re-pressure overcurrent protection on this side can reliably operate in the event of a fault.

[0010] 1.3 The PTs on each side are disconnected or the voltage pressure plate is not put into operation. At this time, the protection on this side cannot receive the voltage on each side, and the re-pressure element is opened;

[0011] The re-pressure overcurrent directional protection action must simultaneously meet the following three conditions: re-pressure opening, directional element opening, and overcurrent element action:

[0012] 2.1 Among them, the operating condition of the overcurrent component needs to meet that the current value reaches the setting value under the condition that the backup protection hard pressure plate, soft pressure plate, and control word are input;

[0013] 2.2 The opening conditions of the complex voltage component on this side are as described in 1.1 - 1.3. At the same time, when the switch on this side is in the off position, since the collected voltage is the bus voltage, and since the collected voltage and current do not originate from the same system, the bus voltage will not change significantly during a fault, resulting in the non-opening of the complex voltage and the unreliable operation of the protection. Therefore, the following logic is added. When TWJ = 1, that is, when the switch is in the off position, the opening logic of the complex voltage overcurrent directional protection no longer needs to meet the complex voltage condition;

[0014] 2.3 When the PT on this side is disconnected, since the voltage cannot be collected, the directional component automatically opens; in addition, when the switch is in the off position, that is, when TWJ = 1, since the collected voltage and current do not originate from the same system, the opening condition of the directional component may not be met. Therefore, when the switch is in the off position, the opening logic of the complex voltage overcurrent directional protection no longer needs to meet the directional component condition; at this time, the complex voltage condition also does not need to be met. Therefore, the complex voltage overcurrent directional protection on this side becomes a pure overcurrent protection when the switch on this side is in the off position, which can effectively avoid the problem that the directional component or the complex voltage component cannot open correctly, resulting in the inability of the protection on that side to act in time, thereby improving the timeliness and reliability of fault removal.

[0015] A control device for the opening logic of the complex voltage blocked directional overcurrent protection of a transformer, comprising: at least one processor; and a memory communicatively connected to at least one of the processors; wherein the memory stores instructions executable by the processor, and the instructions are used for the processor to execute the foregoing control method for the opening logic of the complex voltage blocked directional overcurrent protection of the transformer.

[0016] Compared with the prior art, the beneficial effects of the present invention are: The control method and device for the opening logic of the complex voltage blocked directional overcurrent protection of the transformer of the present invention improve the flexibility of load dispatching and eliminate the risk of misoperation of voltage pressure plates by maintenance personnel. The present invention can ensure the correct operation of the complex voltage blocked directional overcurrent protection of the transformer without the need for maintenance personnel to manually operate the voltage pressure plates, effectively improving the operation and maintenance efficiency and the safety level of the power grid. Brief Description of the Drawings

[0017] Figure 1 It is a wiring diagram of a 220kV three-winding transformer in Embodiment 2;

[0018] Figure 2 It is an improved complex voltage opening logic diagram of the present invention;

[0019] Figure 3 It is an action logic diagram of the complex voltage overcurrent directional protection. Detailed Embodiment

[0020] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0021] 1. The functions and defects of the existing overcurrent protection with voltage compound blocking are analyzed as follows:

[0022] The overcurrent protection with voltage compound blocking for transformers is the backup protection for the main protection of transformers and the medium and low voltage side busbars. To improve the sensitivity of the protection, it is necessary to pass through voltage compound blocking, that is, negative sequence voltage and low voltage blocking. The overcurrent protection with voltage compound blocking can be set according to the rated current of the transformer to avoid, and the setting value is relatively low. In order to improve the sensitivity of the overcurrent protection with voltage compound blocking on each side of the transformer, the protection on the high and medium voltage sides is opened through a three-side voltage OR gate. As long as the voltage value on any side reaches the blocking voltage setting value, the voltage compound on the high and medium voltage side protections will start. The low voltage side is only blocked by the voltage on its own side. For a 220 kV transformer in a multi-source network, in order to meet the selectivity of the protection, a direction element is also set for the overcurrent protection with voltage compound blocking.

[0023] The principle of the overcurrent direction protection with voltage compound blocking for transformers is relatively complex. Voltage input hard pressure plates are set on various types of protection devices, and maintenance personnel need to change the operation pressure plates according to the operation mode. On the one hand, it affects the real-time performance of load dispatching. On the other hand, there may be problems with incorrect operation of the pressure plates, affecting the correct operation of the protection and leading to the occurrence of human events.

[0024] If the voltage compound pressure plates are incorrectly operated and withdrawn under different operating states of the main transformer (when the main transformer has no independent voltage transformer and the bus voltage is adopted), the following effects will occur:

[0025] When the switches on the three sides of the main transformer are all in operation, if the voltage compound pressure plate on the low voltage side is not put in, the voltage compound direction on the low voltage side will be open, and the low voltage side will become a pure overcurrent protection. Since the protection current value is set according to the rated current and the setting value is relatively low, it is easy to cause incorrect operation of the protection. It will trip the local side in one time limit and trip the three sides of the main transformer in the second time limit. If the voltage pressure plate on the high voltage side or the medium voltage side is not put in, the direction element on that side will be open, and the voltage compound element can still be blocked by the other two sides.

[0026] Due to the adjustment of the power grid operation mode, when the medium voltage side switch is in cold standby, since the bus side knife switch is in the off position, the medium voltage side voltage is 0 at this time and the low voltage is open. If the voltage compound pressure plate is not withdrawn at this time, it will cause the voltage compound on the high voltage side to be open and easily cause incorrect operation of the protection.

[0027] When the medium-voltage side switch is in hot standby, or the low-voltage side switch is in hot (cold) standby, if the complex voltage pressure plate is not withdrawn, although the switch is in the off position at this time, the main transformer protection can collect the bus voltage. There are two situations at this time. (1) If a fault occurs in the low / medium-voltage side bus or outgoing line, resulting in the opening of the voltage lockout, it will cause the complex voltage on the normally operating high-voltage side to open. If there is a transient fault in the power grid at this time, it is easy to cause the misoperation of the complex voltage blocked overcurrent protection on the high-voltage side. (2) If a fault occurs between the hot standby switch of the main transformer and the current transformer, for the main transformer differential protection, the fault is outside the zone and cannot operate. Although the complex voltage on the high-voltage side is open and the conditions for the complex voltage on the hot standby side to open are met at this time, since the bus voltage on the hot standby side and the fault current come from different systems, it may cause its power direction element not to open, and the complex voltage blocked overcurrent direction protection on the medium-voltage side cannot operate correctly. It is necessary to rely on the complex voltage overcurrent direction protection on the high-voltage side to cut off the fault. This results in one less reliable backup protection for the transformer, prolongs the fault existence time, and is prone to causing damage to the main transformer and equipment failure.

[0028] 2. Functions that the logic control method of the present invention needs to achieve:

[0029] According to the above analysis, when the medium-voltage side switch is in hot standby (low-voltage side hot standby or cold standby), the complex voltage blocking function of the protection on this side, as well as the direction element on this side, should be withdrawn and become pure overcurrent protection, so that the medium-voltage side protection can operate effectively. At the same time, the complex voltage blocking on the other two sides should not collect the voltage on this side and should not be affected by the voltage on this side. Analyzing the root cause of the above problems lies in a series of problems caused by the inconsistency between the actual voltage on the standby side of the main transformer and the voltage collected in the protection device. Therefore, the TWJ contact of the circuit breaker can be introduced. When the switch on a certain side is in the off position, at this time, the main transformer voltage is inconsistent with the collected voltage, directly opening the complex voltage condition and the direction condition of the complex voltage overcurrent protection on this side, and the protection on this side becomes pure overcurrent. At the same time, the complex voltage conditions on the other sides are no longer opened through the complex voltage on the hot standby side, avoiding affecting the normally operating protection.

[0030] 3. The present invention improves the opening logic of the complex voltage blocked overcurrent direction protection of the main transformer.

[0031] As Figure 1 shown is the wiring schematic diagram of the 220kV three-winding transformer applied in the present invention;

[0032] As Figure 2 is the improved complex voltage opening logic diagram of the present invention;

[0033] The complex voltage opening logic satisfies any of the following conditions to open the complex voltage element:

[0034] (1) When both the complex voltage element on this side operates and there is no PT disconnection or PT withdrawal on this side at the same time, the complex voltage on this side operates at this time, and the element should be normally opened.

[0035] (2) The composite voltage element on the other side operates and TWJ≠1 on the other side. Here, TWJ is the trip position relay. When TWJ = 1, it indicates that the switch is in the open position. Conversely, when TWJ = 0, the switch is in the closed position. This means that only when the other side is in the closed position and the composite voltage is open, the composite voltage on this side will receive the voltage open signal from the other side, so that the composite voltage overcurrent protection on this side will operate reliably during a fault. Taking the low-voltage side as an example, when the low-voltage side switch of the main transformer is in the open position, if a fault occurs on the low-voltage side bus, it will cause the composite voltage on the low-voltage side to meet the open condition, which may cause the composite voltage overcurrent protection on the medium-voltage side or high-voltage side to malfunction and cut off the normal load. After the condition of TWJ≠1 is introduced in the present invention, when the switch on a certain side is in the open position, the voltage open logic on the other side will no longer be affected by the voltage on the cold standby or hot standby side, thus improving the reliability of the protection action.

[0036] (3) The PT is broken on each side or the voltage pressure plate is not inserted. At this time, the protection on this side cannot receive the voltage on each side, and the composite voltage element is open.

[0037] As Figure 3 shown is the action logic diagram of the composite voltage overcurrent directional protection;

[0038] The action of the composite voltage overcurrent directional protection needs to meet three conditions simultaneously: the composite voltage is open, the directional element is open, and the overcurrent element operates.

[0039] (1) Among them, the action condition of the overcurrent element needs to meet that when the hard pressure plate, soft pressure plate, and control word of the backup protection are input, the current value reaches the setting value.

[0040] (2) The open condition of the composite voltage element on this side is as described above. At the same time, when the switch on this side is in the open position, because the collected voltage is the bus voltage, and because the collected voltage and current do not originate from the same system, the bus voltage may not change significantly during a fault, resulting in the composite voltage not being open and the protection not operating reliably. Therefore, the following logic is added. When TWJ = 1, that is, when the switch is in the open position, the open logic of the composite voltage overcurrent directional protection no longer needs to meet the composite voltage condition.

[0041] (3) When the PT on this side is broken, because the voltage cannot be collected, the directional element is automatically open. In addition, when the switch is in the open position, that is, TWJ = 1, because the collected voltage and current do not originate from the same system, the open condition of the directional element may not be met. Therefore, when the switch is in the open position, the open logic of the composite voltage overcurrent directional protection no longer needs to meet the directional element condition. At this time, the composite voltage condition does not need to be met either. Therefore, the composite voltage overcurrent directional protection on this side becomes a pure overcurrent protection when the switch on this side is in the open position, which can effectively avoid the problem that the directional element or the composite voltage element cannot be correctly opened, resulting in the protection on this side not being able to act in time, thus improving the timeliness and reliability of fault removal.

[0042] In addition to the above embodiments, the present invention may have other embodiments. Any technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope required by the present invention.

Claims

1. A transformer re-voltage locking direction overcurrent protection open logic control method, characterized in that: include: The composite voltage opening logic meets any of the following conditions, that is, the composite voltage element is opened: 1.1 When the two conditions of the composite voltage element on this side acting and the PT on this side not being disconnected or exiting are met at the same time, the composite voltage element on this side acts and the element should open normally; 1.2 The composite voltage element on the other side is actuated and TWJ on the other side is ≠1. The TWJ is a trip position relay. When TWJ=1, it indicates that the switch is in the open position, and when TWJ=0, it indicates that the switch is in the closed position. This means that only when the other side is in the closed position and the re-pressure is open, the re-pressure on this side will receive the voltage opening signal on the other side, so that the re-pressure overcurrent protection on this side can reliably operate in the event of a fault. 1.3 The PTs on each side are disconnected or the voltage pressure plate is not put into operation. At this time, the protection on this side cannot receive the voltage on each side, and the re-pressure element is opened; The re-pressure overcurrent directional protection action must simultaneously meet the following three conditions: re-pressure opening, directional element opening, and overcurrent element action: 2.1 Among them, the overcurrent element action condition must meet the backup protection hard pressure plate, soft pressure plate, control word input, and the current value reaches the set value; 2.2 The opening conditions of the re-pressure element on this side are as described in 1.1-1.

3. At the same time, when the switch on this side is in the open position, because the collected voltage is the bus voltage, and because the collected voltage and current are not from the same system, the bus voltage will not change significantly when a fault occurs, resulting in the re-pressure not being opened and the protection cannot be reliably operated. Therefore, the following logic is added: when TWJ=1, that is, when the switch is in the open position, the re-pressure overcurrent direction protection opening logic no longer needs to meet the re-pressure condition; 2.3 When the PT on this side is disconnected, the directional element automatically opens because the voltage cannot be collected. In addition, when the switch is open, that is, TWJ=1, the directional element opening condition may not be met because the collected voltage and current are not from the same system. Therefore, when the switch is open, the re-voltage overcurrent directional protection opening logic no longer needs to meet the directional element condition. At this time, the re-voltage condition does not need to be met. Therefore, the re-voltage overcurrent directional protection on this side becomes a pure overcurrent protection when the switch on this side is open, which can effectively avoid the problem that the directional element or the re-voltage element cannot be opened correctly, resulting in the protection on this side cannot be activated in time, thereby improving the timeliness and reliability of fault removal.

2. A transformer re-pressure locking direction overcurrent protection open logic control device, characterized in that: include: at least one processor; And, a memory communicatively connected to at least one of the processors; wherein the memory stores instructions executable by the processor, and the instructions are used by the processor to execute the transformer re-voltage locking direction overcurrent protection open logic control method as described in claim 1.

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