CN109787190B - Oil flow velocity variation-based digital non-electric quantity protection method for oil-immersed transformer - Google Patents
Oil flow velocity variation-based digital non-electric quantity protection method for oil-immersed transformer Download PDFInfo
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Abstract
The digital non-electric quantity protection method of the oil-immersed transformer based on the oil flow speed variation comprises the following steps that firstly, a digital flow velocity sensor arranged at a connecting pipe of the oil-immersed transformer continuously measures the oil flow speed in the connecting pipe in real time; then, the digital gas relay judges whether a speed variation calculation program is started or not by utilizing the received oil flow speed data, if so, the oil flow speed variation is calculated, and the variation measured value is compared with the variation setting value in size; and determining whether the protection acts according to the comparison result. The method can effectively start when the oil-immersed transformer has internal faults, and protects reliable actions; and prevent the maloperation when the oil-immersed transformer has an external fault.
Description
Technical Field
The invention relates to the technical field of protection of oil-immersed transformers, in particular to a digital non-electric quantity protection method of an oil-immersed transformer based on oil flow speed variation.
Background
Since the 20 s of the last century, the transformer gas protection has become the mainstream non-electric quantity protection mode of the transformer, and is used as a supplement for the electric quantity protection of the transformer, mainly for the situation of short circuit fault inside the transformer. Compared with the electrical quantity protection of the transformer, the non-electrical quantity protection which reflects the generation of the fault gas can more comprehensively and directly reflect the running state of the protected object, and has unique advantages in the aspect of sensitivity and the like.
Original oil-immersed transformer's buchholz relay is mechanical type protection, and its protection principle based on oil flow speed size information does, can produce the flow of oil flow under the inside trouble condition, strikes the preceding baffle of float down, then the baffle rotates, and following dry spring contact is closed, then the circuit breaker tripping operation. However, due to the lack of sufficient attention and research for a long time, the gas relay used in the current system has the defects of low reliability, insufficient threshold value by experience, mechanical structure and speed, etc., and the gas protection malfunction and malfunction accidents occur. According to statistics, in recent years, accidents of false operation tripping caused by external faults of 500kV transformer gas protection have occurred in China; moreover, the conventional gas relay has the problems that the whole process from sensing the flow rate to triggering protection to tripping is too long in delay and the optimal tripping time is possibly missed, once serious turn-to-turn short circuit or internal arc short circuit fault of a sleeve occurs in a transformer, fault arc energy is rapidly released, the gas relay arranged at the connecting pipe of the oil conservator is usually difficult to timely sense the change of oil flow surge, the conventional gas relay cannot act in time, and the wall of an oil tank near the fault point is subjected to plastic deformation, cracking and even explosion.
Disclosure of Invention
In order to solve the problems in the prior art, an object of the present invention is to provide a digital protection method capable of quickly reflecting the variation of the oil flow speed in a connection pipe when an internal fault occurs in an oil-immersed transformer, that is, a digital non-electric quantity protection method for an oil-immersed transformer based on the variation of the oil flow speed, which can quickly detect the variation of the oil flow speed in the connection pipe of the oil-immersed transformer, output digital information to compare with a setting value, and make a quick judgment to quickly isolate the fault.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
the digital non-electric quantity protection method of the oil-immersed transformer based on the oil flow speed variation comprises the following steps:
step 1: the digital flow velocity sensor arranged at the connecting pipe of the oil-immersed transformer continuously measures the speed of the oil flow in the connecting pipe in real time, the digital gas relay of the oil-immersed transformer transmits the digital information of the primary oil flow velocity every interval delta t, and the velocity value is recorded as vn；
Step 2: digital gas relay judging speed vnWhether the starting value v is more than or equal to the starting value v of the digital gas relayopenI.e. to judge vn≥vopenIf yes, starting a speed variation calculation program and entering step 3; if not, not starting the speed variation calculation program;
and step 3: the digital gas relay receives the oil flow velocity vnAnd the last received oil flow velocity vn-1According to the formula Δ voil＝vn-vn-1Calculating the oil flow velocity variation quantity delta v of the oil flow velocity in the past delta toil。
And 4, step 4: the digital gas relay calculates the speed variation delta voilAnd a setting value delta vsetComparing to judge whether the oil flow speed variation is larger than or equal to the set value, namely to judge delta voil≥ΔvsetWhether or not it is satisfied;
and 5: if Δ v appears twice in successionoil≥ΔvsetIf the fault is judged to occur in the oil immersed transformer, the digital gas relay acts to trip the breaker; otherwise, the digital gas relay does not act and returns to wait for the next flow calculation program to be started.
Flow velocity variation setting value delta v for starting digital gas relaysetK of maximum flow rate variation in sampling interval possibly caused by external fault of oil-immersed transformerrelMultiple, KrelFor reliability factor, it is generally slightly larger than 1.
The method needs a digital flow velocity sensor to continuously measure the oil flow velocity in the connecting pipe of the oil-immersed transformer, and transmits the velocity information to a digital gas relay in real time, and the digital gas relay continuously calculates the variation of the oil flow velocity. The setting value is set on the principle of the maximum variation of the flow velocity of the oil flow when the external fault is avoided, so that once the measured flow velocity variation is larger than the setting value, the internal fault of the oil-immersed transformer is judged, the judgment result is output, the breaker is tripped, the internal fault of the oil-immersed transformer is reliably protected, the misoperation of the oil-immersed transformer when the external fault is avoided, the protection reliability of the gas relay on the internal fault of the oil-immersed transformer is effectively improved, and the gas relay has good speed.
Drawings
FIG. 1 is a flow chart of a method of implementing the present invention.
Fig. 2 is a schematic view of the installation position of a digital buchholz relay suitable for the present invention.
Fig. 3 is a diagram illustrating an embodiment of the method of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
As shown in fig. 1, the digital non-electric quantity protection method for the oil-immersed transformer based on the oil flow velocity variation according to the present invention includes the following steps:
step 1: as shown in fig. 2, the digital flow rate sensor installed at the connection pipe of the oil immersed transformer continuously measures the speed of the oil flow in real time, the digital buchholz relay of the oil immersed transformer transmits digital information of the oil flow speed every time at, and the speed value is recorded as vn；
Step 2: digital gas relay judging speed vnWhether the starting value v is more than or equal to the starting value v of the digital gas relayopenI.e. to judge vn≥vopenIf yes, starting a speed variation calculation program and entering step 3; if not, not starting the speed variation calculation program;
and step 3: the digital gas relay receives the oil flow velocity vnAnd the last received oil flow velocity vn-1According to the formula Δ voil＝vn-vn-1Calculating the oil flow velocity variation quantity delta v of the oil flow velocity in the past delta toil；
And 4, step 4: the digital gas relay calculates the speed variation delta voilAnd a setting value delta vsetComparing, and judging whether the oil flow speed variation is larger than or equal to a set value; i.e. determining Δ voil≥ΔvsetWhether or not it is satisfied;
and 5: if Δ v appears twice in successionoil≥ΔvsetIf the fault is judged to occur in the oil immersed transformer, the digital gas relay acts to trip the breaker; otherwise, the digital gas relay does not act and returns to wait for the next flowAnd starting the calculation program.
The flow rate variation setting value for starting the gas relay is K of the maximum flow rate variation in a sampling interval possibly caused by external faults of the transformerrelMultiple, KrelFor reliability factor, it is generally slightly larger than 1.
Examples
As shown in FIG. 3, a radial grid, hereinafter referred to as an oil-immersed transformer T1The method is illustrated by way of example.
Step 1: mounted on an oil-immersed transformer T1The digital flow velocity sensor at the connecting pipe continuously measures the speed of the oil flow in the connecting pipe in real time, digital information of the oil flow velocity is transmitted to the digital gas relay of the oil-immersed transformer at intervals of delta t, and the velocity value is recorded as vn；
Step 2: digital gas relay judging speed vnWhether the starting value v is more than or equal to the starting value v of the digital gas relayopenI.e. to judge vn≥vopenIf yes, starting a speed variation calculation program and entering step 3; if not, not starting the speed variation calculation program;
and step 3: the digital gas relay receives the oil flow velocity vnAnd the last received oil flow velocity vn-1According to the formula Δ voil＝vn-vn-1Calculating the oil flow velocity variation quantity delta v of the oil flow velocity in the past delta toil；
And 4, step 4: the digital gas relay calculates the speed variation delta voilAnd a setting value delta vsetComparing to judge whether the oil flow speed variation is larger than or equal to the set value, namely to judge delta voil≥ΔvsetWhether or not it is satisfied;
and 5: if Δ v appears twice in successionoil≥ΔvsetThen, it is determined as the oil-immersed transformer T1When an internal fault occurs, the digital gas relay acts to trip the breaker; otherwise, the digital gas relay does not act and returns to wait for the next flow calculation program to be started.
The flow speed variation setting value for starting the gas relay is set as the transformer T1K of maximum flow rate variation in sampling interval possibly caused by external faultrelMultiple, KrelFor reliability factor, it is generally slightly larger than 1.
By adopting the protection scheme of the invention, reasonable v is set for the oil-immersed power transformeropenValue sum Δ vsetThe value may effectively distinguish between internal and external faults. When the external circuit has a fault, the misoperation can be effectively prevented; when the transformer has an internal fault, the transformer can reliably act.
Claims (3)
1. The digital non-electric quantity protection method of the oil-immersed transformer based on the oil flow speed variation is characterized by comprising the following steps: the method comprises the following steps:
step 1: the digital flow velocity sensor arranged at the connecting pipe of the oil-immersed transformer continuously measures the speed of the oil flow in the connecting pipe in real time, the digital gas relay of the oil-immersed transformer transmits the digital information of the primary oil flow velocity every interval delta t, and the velocity value is recorded as vn；
Step 2: digital gas relay judging speed vnWhether the starting value v is more than or equal to the starting value v of the digital gas relayopenI.e. to judge vn≥vopenIf yes, starting a speed variation calculation program and entering step 3; if not, not starting the speed variation calculation program;
and step 3: the digital gas relay receives the oil flow velocity vnAnd the last received oil flow velocity vn-1According to the formula Δ voil＝vn-vn-1Calculating the oil flow velocity variation quantity delta v of the oil flow velocity in the past delta toil；
And 4, step 4: the digital gas relay calculates the speed variation delta voilAnd a setting value delta vsetComparing to judge whether the oil flow speed variation is larger than or equal to the set value, namely to judge delta voil≥ΔvsetWhether or not it is satisfied;
and 5: if Δ v appears twice in successionoil≥ΔvsetIf the fault is judged to occur in the oil immersed transformer, the digital gas relay acts to trip the breaker; otherwise, the digital gas relay does not act and returns to wait for the next flow calculation program to be started.
2. The oil-filled transformer digital non-electric quantity protection method based on the oil flow velocity variation quantity according to claim 1, characterized in that: the speed variation threshold value of the protection action is a setting value delta vsetIs set based on avoiding an external fault.
3. The oil-filled transformer digital non-electric quantity protection method based on the oil flow velocity variation quantity according to claim 1, characterized in that: the calculation of the oil flow rate variation in step 3 is continuously performed.
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