CN201789272U - Relay protection circuit preventing transformer differential protection malfunction - Google Patents

Abstract

The utility model relates to a relay protection circuit, in particular to a relay protection circuit preventing transformer differential protection malfunction, which aims at providing a relay protection device preventing transformer differential protection malfunction. The relay protection device automatically locks a secondary current loop by the aid of the running state of a primary device, and is simultaneously assisted by external connection to eliminate blind zone failure. The technical scheme of the relay protection circuit preventing transformer differential protection malfunction includes that 1 the relay protection circuit comprises a main transformer differential protection device 1, and 2 connection points of all circuit breakers on all sides of a transformer with a tripping position in an isolating switch are arranged in corresponding switching value input loops in the differential protection device, the differential protection device adopts input values of a terminal of the differential protection device as locking values of corresponding sides, and when the input values of the differential protection device indicate potential input, the differential protection device locks current of the corresponding side by the aid of internal program.

Description

Relay protection circuit to prevent maloperation of transformer differential protection

technical field

The utility model relates to a relay protection circuit, in particular to a relay protection circuit for preventing maloperation of transformer differential protection. the

Background technique

According to the requirements of "Technical Regulations for Relay Protection and Safety Automatic Devices" (DL400-91), the power equipment in the power system must be installed to meet the system safety and equipment safety, and can selectively cut off the main protection of the protected equipment at the fastest speed. . As a key main equipment, the power transformer occupies an extremely important position in the power system. The reliability of power transformer operation is an important guarantee for the safety of the entire power system; therefore, the correct and reliable action of transformer relay protection is extremely important. When the transformer fails, its protection device refuses to operate or cannot act quickly within the required time, which may cause damage to the transformer to varying degrees, or even burn out; Unnecessary power outage losses. the

The existing transformer differential protection principle is Kirchhoff's first law. When the transformer is in normal operation or an external fault occurs, the current flowing into the transformer is equal to the current flowing out of the transformer, and the differential protection does not operate; when the transformer is internally faulty, only the current flowing If the current entering the transformer does not flow out of the transformer, the differential protection operates to disconnect the circuits on each side and isolate the fault point. According to the operation principle of differential protection and external wiring, it can be clearly known that the protection range of differential protection is all equipment between the transformers connected to the differential secondary current. The specific protection configuration is shown in Figure 1. the

In order to ensure the reliability and continuity of power supply, when the current transformer on the high-voltage side of the main transformer connected to the inner bridge fails or needs to be replaced, the bridge switch is generally used to reduce the downtime of the main transformer. According to the "Regulations on Inspection of Relay Protection and Power Grid Safety Automatic Devices", the inspection content of the current transformer circuit includes testing the polarity of the winding, checking the transformation ratio of the working tap from the primary input of the current transformer, and surveying and mapping the secondary winding. The excitation characteristic curve, etc. (see Figure 2). If the current circuit of the main transformer protection is not effectively isolated due to the negligence of the test personnel during the construction, in the subsequent through-current test, a differential current will be artificially generated in the differential protection, causing the protection to malfunction, disconnecting the operating transformer, and the backup protection Due to the complex voltage blocking function, there will be no malfunction. the

When the electrical equipment on each side of the transformer (including circuit breakers, isolation switches, current transformers, etc.) Take the replacement of the #1 main transformer high-voltage side circuit breaker in the 110kV inner bridge substation as an example. With #1 main transformer load, conduct the impact main transformer circuit breaker test to the substation through the switch on the opposite side of the line. If a short-circuit accident occurs in the circuit breaker during the impact process, not only the circuit breaker on the opposite side will trip, but also because the fault point is within the differential protection range of #1 main transformer, the differential protection will be activated, and the high-voltage side bus and low-voltage side will be tripped The circuit breaker causes the #1 main transformer to quit running under normal conditions, as shown in Figure 3. In the actual scheduling operation process, in order to prevent such a situation from happening, the method of exiting the differential protection during the impact of the equipment is adopted. Although this measure can avoid the possibility of differential protection misoperation, it will also reduce the safety of the main transformer equipment. The reliability and system operation reliability are very different from the requirements of the power grid safety regulations. the

From the composition of the main transformer differential protection and the occurrence of maloperation, it can be known that the current required for abnormal protection flows into the current transformer connected to the differential protection, which is the main cause of maloperation. The existing methods to solve the above faults mainly include: 1. Implement temporary isolation measures on site, that is, arrange professionals to come to the Disconnect the corresponding secondary current loop on site. In order to ensure the safety of personnel and equipment, it is necessary to use a special short wire to complete the short circuit on the protection terminal block, as shown in Figure 4. The main problem of implementing temporary isolation measures on site is that it is necessary to specially arrange maintenance personnel to perform isolation and short-circuit work on different substations and different differential protection device current circuits according to the requirements of the operation mode, which requires high technical level of personnel and heavy workload. And dangerous, prone to omissions and "three mistakes" accidents, at the same time, due to long distances, insufficient personnel lead to low efficiency, seriously restricting the normal dispatch of the power grid. 2. The method of isolation by the operator using the short-circuit terminal, that is, the method of isolation by the operator of the substation using the current circuit short-circuit terminal can effectively reduce working hours and improve operational efficiency, and does not need to specially arrange maintenance personnel to follow the shift to perform short-circuit work. However, the premise of this method is that the current loops on each side of the main transformer differential protection need to be equipped with high-current short-circuit terminals that are convenient for operators to operate. According to the current actual situation, most of the differential protection does not have such terminals installed; at the same time, according to the requirements of the operating regulations, when the equipment is not in maintenance, the operating personnel are not allowed to perform this operation, so this method cannot be effectively implemented. the

The above two troubleshooting methods put forward higher requirements on the operation mode, personnel quality, and equipment configuration. With the increase of equipment in the power grid, the workload of such situations will inevitably increase greatly; According to the operation mode of the power grid, the relay protection device with automatic discrimination can fundamentally solve the above problems. the

Utility model content

The utility model aims at the transformer with the above-mentioned problems, and provides a relay protection device for preventing misoperation of the transformer differential protection. Wiring to eliminate dead zone faults. the

The utility model is implemented through the following technical solutions: a relay protection circuit for preventing maloperation of transformer differential protection, including:

1) The main transformer differential protection device 1, its analog input terminal is respectively connected to the secondary current of the high-voltage side line current transformer, the high-voltage side bus-division current transformer and the main transformer 1 low-voltage side current transformer;

2) The main transformer differential protection device 1, its digital input terminal is respectively connected to the main transformer 1 high-voltage side line circuit breaker, bus isolating switch, line isolating switch position contact, high-voltage side bus sub-switch, section I bus isolating switch, II The position contact of the section bus isolating switch, the main transformer 1 low-voltage side circuit breaker, the bus switch knife, and the main transformer switch knife open position contact;

The opening position contacts of the circuit breaker on each side of the transformer and the isolating switch are set in the corresponding switching value input circuit in the differential protection device, and the input value of the terminal in the differential protection device is used as the blocking value of the corresponding side, When the binary input in the differential protection device shows potential input, the current of the corresponding side is blocked through the internal program. the

In the above differential protection device, the position contacts of the high-voltage side circuit breaker, the position contacts of the high-voltage side busbar isolating switch and the position contacts of the high-voltage side line isolating switch are connected in parallel in the high-voltage side switch terminal box and then input and withdrawn through the photocoupler at the position of the high-voltage side. The pressure plate enters the differential protection device. the

The switch terminal box on the high-voltage section side in the above-mentioned differential protection device includes the position contact of the circuit breaker on the high-voltage section side, the position contact of the busbar isolating switch on the high-voltage section side, and the position contact of the line isolating switch on the high-voltage section side; In the protection device, the position contacts of the circuit breaker on the high-voltage section side, the position contacts of the busbar isolating switch of the high-voltage section I section and the position contacts of the busbar isolating switch of the high-voltage section II section are connected in parallel in the high-voltage side section switch terminal box and pass through the high-voltage The optocoupler at the side section position inputs the input of the throwing and withdrawing pressure plate into the differential protection device. the

In the above-mentioned differential protection device, the position contact of the low-voltage side circuit breaker, the position contact of the busbar isolation switch on the low-voltage side and the position contact of the line isolation switch on the low-voltage side are connected in parallel in the terminal box of the low-voltage side switch, and then input and withdraw through the optocoupler at the position of the low-voltage side. The pressure plate enters the differential protection device. the

When using the utility model, after changing the differential protection logic of the main transformer and the corresponding wiring, first check whether the position input of the circuit breakers on each side and the isolation switch knife in the differential protection is correct; secondly, ensure that the differential protection On the basis of the correct connection of the current loops on each side, pass in the test current, and check the sampling value and differential current display of the corresponding current in the differential protection by simulating the closure of each external contact. The correct situation should be that the current sampling value of the corresponding side is zero. Simultaneously there are differential flow values of the same magnitude. the

The main transformer differential protection logic is as follows: set up a logic circuit with the function of switching value blocking current, the logic is: when the high-voltage side circuit breaker or any isolating switch on the high-voltage side is disconnected, the current circuit of the high-voltage side of the differential protection is blocked; when the high-voltage section When the side circuit breaker or any isolating switch on the high-voltage section side is disconnected, the current loop on the high-voltage section side is blocked for differential protection; when the low-voltage side circuit breaker or any isolating switch on the low-voltage side is disconnected, the current loop on the low-voltage side of the differential protection is blocked; its logic The circuit is shown in Figure 5. the

The beneficial effects of the utility model are: the relay protection device provided by the utility model can effectively maintain the unity of the primary and secondary equipment by combining the position of the circuit breaker on each side of the transformer, the position of the isolation knife and changing the corresponding differential protection program logic. Avoid the misoperation of the main transformer differential protection. the

Description of drawings

Figure 1 is a schematic diagram of a transformer differential protection configuration. the

Fig. 2 is the maintenance diagram of the current transformer on the high voltage side of the transformer main transformer 1. the

Fig. 3 is a fault schematic diagram of the circuit breaker on the high-voltage side of the main transformer 1 of the transformer. the

Figure 4 is a schematic diagram of professional maintenance personnel disconnecting the secondary current loop. the

Fig. 5 is a logic diagram for locking the differential current circuit of the transformer. the

Figure 6 is a wiring diagram of the position input of the equipment on the high voltage side of the transformer. the

Detailed ways

The technical solutions of the present utility model will be further described below through specific embodiments. the

Embodiment 1: Take the high-voltage side part of the 110kV transformer RCS-9671 differential protection device of Narui Jibao Company as an example. As shown in Figure 1-4, the relay protection device to prevent maloperation of transformer differential protection includes:

1) Main transformer differential protection device 1, whose input terminals are respectively connected to the secondary current of the high-voltage line current transformer, high-voltage bus-division current transformer and main transformer 1 low-voltage side current transformer;

2) The main transformer differential protection device 1, whose output terminals are respectively connected to the main transformer 1 high voltage side line circuit breaker, bus isolating switch, line isolating switch opening position contact, high voltage side bus isolating switch, section I bus isolating switch, Contact for the opening position of the bus isolating switch of section II, the contact for the opening position of the main transformer 1 low-voltage side circuit breaker, busbar switch blade, and main transformer switch blade;

It is characterized in that: the opening contacts of the circuit breaker on each side of the transformer and the isolating switch are set in the corresponding switch value input circuit in the differential protection device, and the input value of its terminal is the corresponding side in the differential protection device. Blocking amount, when the binary input in the differential protection device shows potential input, the current amount of the corresponding side is blocked through the internal program. the

As shown in Figure 6, in the high-voltage side switch terminal box, the trip position contacts in the high-voltage side circuit breaker of the transformer, the high-voltage side busbar isolating switch, and the high-voltage side line isolating switch are connected in parallel, and then the differential input is introduced through the switch input and withdrawal pressure plate. In the corresponding switching value input circuit of the protection, and define the input value of this terminal as the high-voltage side blocking value in the differential protection program, when the differential protection senses that the binary input value has a potential input, it will block the electric current of the high-voltage side through the internal program. flow. the

The principle of using the high-voltage section side of the differential protection device and the low-voltage side of the differential protection device, as shown in Figure 5 , will not be repeated here. the

The specific embodiments described herein are only examples to illustrate the spirit of the present invention. Those skilled in the technical field to which the utility model belongs can make various modifications or supplements to the described specific embodiments or adopt similar methods to replace them, but they will not deviate from the spirit of the utility model or go beyond what is stated in the appended claims. defined range. the

Claims (4)

1. A relay protection circuit for preventing maloperation of transformer differential protection, comprising: The input terminals of the main transformer differential protection device 1 are respectively connected to the line current transformer, the bus-division current transformer and the secondary current of the main transformer 1 low-voltage side current transformer; The output terminal of the main transformer differential protection device 1 is respectively connected to the main transformer 1 high-voltage side line circuit breaker, bus isolating switch, line isolating switch opening position contact; Switch opening position contact, main transformer 1 low-voltage side circuit breaker, busbar switch knife, main transformer switch knife opening position contact; It is characterized in that: the opening position contacts of the circuit breakers on each side of the transformer and the isolating switch are set in the corresponding switch value input circuits in the differential protection device, and the input value of its terminals is used as the corresponding input value in the differential protection device. Side blocking amount, when the binary input in the differential protection device shows that there is potential input, the current amount of the corresponding side is blocked through the internal program. 2. The relay protection device for preventing maloperation of transformer differential protection according to claim 1, characterized in that: the high-voltage side switch terminal box in the differential protection device includes a position contact of a high-voltage side circuit breaker, a high-voltage The position contact of the side bus isolating switch and the position contact of the high-voltage side line isolating switch; the three are connected in parallel to each other and then input into the differential protection device through the position optocoupler of the high-voltage side. 3. The relay protection device for preventing maloperation of transformer differential protection according to claim 1 or 2, characterized in that: the high voltage segment side switch terminal box in the differential protection device includes a high voltage segment side open circuit The divider contact, the divider contact of the busbar isolating switch on the high-voltage segment side and the divider contact of the line isolating switch on the high-voltage segment side; after the three are connected in parallel, they are input into the differential protection device through the optocoupler at the segment position on the high-voltage side. . 4. The relay protection device for preventing maloperation of transformer differential protection according to claim 3, characterized in that: the low-voltage side switch terminal box in the differential protection device includes a position contact of a low-voltage side circuit breaker, a low-voltage The position contact of the side bus isolating switch and the position contact of the line isolating switch of the low-voltage side; the three are connected in parallel and then input into the differential protection device through the position optocoupler of the low-voltage side. the

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