CN106094930A - A kind of intelligent control method of transformer cooler - Google Patents

Abstract

The invention discloses the intelligent control method of a kind of transformer cooler, first the method obtains the real time temperature T of Transformer Winding；Reset the constant temperature angle value that transformator runs；Control unit determines cooler control strategy according to real time temperature T and rate of temperature change DT/Dt, according to this strategy output control signal to transformer cooler.The present invention can control transformer cooler work timely and effectively, thus reduces the temperature of transformator, it is ensured that transformator is not damaged by, and improves its service life；The cooler package of cooler can be carried out switching operation, it is to avoid the frequent switching of cooler package, it is to avoid the generation of switch fault, it is ensured that the stable operation of whole cooler, also make the operation that transformator is more stable.

Description

An Intelligent Control Method for Transformer Cooler

technical field

The invention belongs to the technical field of power cooling control, and in particular relates to an intelligent control method for a transformer cooler.

Background technique

During the actual operation of the transformer, a large amount of heat is generated, which makes the internal temperature of the transformer rise, the insulation system of the transformer ages, and even the equipment is damaged due to high temperature. Therefore, for large oil-immersed transformers, it is generally equipped with a forced oil circulation air-cooled cooler or a forced oil circulation water-cooled cooler to enhance the heat dissipation effect of the transformer and reduce the operating temperature of the transformer.

The "110 (66) kV ~ 500kV oil-immersed transformer (reactor) operation specification" issued by the State Grid Corporation of China stipulates that the oil temperature of the upper layer of the oil-immersed air-cooled and self-cooled transformer should not exceed 85 ℃ frequently, and the maximum should not exceed 95 ℃; The control box of the immersed air-cooled transformer must meet the requirements that when the upper oil temperature reaches 55°C or when the operating current reaches the specified value, the fan will be automatically turned on; when the oil temperature drops to 45°C and the operating current drops to the specified value, the fan will stop running.

Today's control methods for transformer coolers operate primarily based on top-level temperature or actual load. When the temperature of the oil top layer reaches a certain temperature or the actual load reaches a certain amount, the traditional electromagnetic relay is used to control the AC contactor to realize the group switching control of the transformer cooler (the cooler includes several cooler groups) . This method cannot smoothly adjust the switching of the cooler with the change of temperature and load current. When several cooler groups are put into operation at the same time, it is easy to cause oil flow impact, and the high-speed flow of transformer oil is easy to cause oil flow electrification, which is easy to form a transformer. Hidden dangers of internal failures affect its safe and stable operation.

Transformer coolers start and stop frequently with changes in internal temperature, and switch failures are prone to occur. Several groups of coolers are turned on or off at the same time, and sometimes it is impossible to effectively control the cooling system in real time for the hot spots of the transformer, which may be due to local high temperatures. As a result, the aging of insulation in local areas inside the transformer is accelerated, and even damage occurs.

Moreover, the temperature of the top layer of the transformer or the actual load of the transformer cannot fully explain the temperature condition of the hottest point of the inner winding of the transformer.

Therefore, we urgently need a new control method for the transformer cooler, so as to better realize the control of the transformer cooler, and reduce the temperature of the transformer in a timely and effective manner.

Contents of the invention

The object of the present invention is to provide an intelligent control method for a transformer cooler, which can timely and effectively control the operation of the transformer cooler, thereby reducing the temperature of the transformer, ensuring that the transformer is not damaged, and improving its service life.

The invention can make the transformer cooler group follow the temperature of the transformer and the temperature change rate of the transformer (the change of the load current) to continuously and smoothly adjust, so that the loss of the transformer and the heat dissipation power can reach a balanced relationship, and realize the switching of the transformer cooler group best control.

An intelligent control method for a transformer cooler, comprising the following steps:

1. Obtain the real-time temperature T of the transformer winding;

2. Set the constant temperature value for transformer operation, the constant temperature value is 50°C;

3. The control unit determines the cooler control strategy based on the real-time temperature T of the transformer winding in step 1 and the temperature change rate DT/Dt, where DT=△T is the temperature change, Dt=△t is the time interval, and △t is 0.5min -1.5min;

When T-50≥5 and DT/Dt≥0, a set of cooler groups will be put into operation; if all cooler groups have been put into operation, this state will be maintained;

When T-50≥5 and DT/Dt<0, maintain the original state;

When -5<T-50<5, maintain the original state;

When T-50≤－5 and DT/Dt>0, maintain the original state;

When T-50≤－5 and DT/Dt≤0, one cooler group will exit; if all cooler groups have exited, this state will be maintained.

A further solution is that the time interval Δt is 1 min.

A further solution is that when T≥105°C, all cooler groups have been put into operation, and the control unit sends an alarm signal to the alarm to alarm.

A further solution is that if the transformer is switched from running to standby, or the transformer is in a zero-load state after the transformer trips due to an external fault, all cooler groups will exit.

A further solution is that in step 3, the control unit records the number of operations of each cooler group;

When a group of cooler groups needs to be put into operation, the control unit selects the cooler group with the least number of times of operation among the cooler groups not put into operation;

When it is necessary to withdraw from a group of cooler groups, the control unit selects the cooler group that has been put into operation with the largest number of times among the cooler groups that have been put into operation to shut down.

The transformer starts to run, the sensor collects the real-time temperature T of the transformer winding in real time, the sensor transmits the collected real-time temperature T of the transformer winding to the control unit, and the control unit receives the real-time temperature T of the transformer winding from the sensor, and compares the temperature with the set temperature The value is compared, and the control unit outputs a control signal to the cooler according to the comparison value and the temperature change rate, thereby controlling the work of the cooler group in the cooler. If no sensor is installed in the present invention, the winding temperature calculation method described in "GB1094.2-1996 Power Transformer Part 2 Temperature Rise" can be used to calculate the real-time temperature T of the transformer winding.

The transformer starts to work, the control unit receives the real-time temperature T of the transformer winding from the sensor in real time, and the control unit calculates the temperature change rate DT/Dt every 0.5min-1.5min. The temperature rises slowly, when T-50≤－5 and DT/Dt>0, the control unit does not send commands to the cooler, and the cooler group does not work; the temperature continues to rise, when -5<T-50<5 , the control unit does not send commands to the cooler, and the cooler group does not work; when T-50≥5 and DT/Dt≥0, the control unit sends a command to the cooler and puts in a group of cooler groups; the temperature continues to rise , that is, T-50≥5 and DT/Dt≥0, put in a set of cooler groups every 0.5min-1.5min until all the cooler groups are put into use; the temperature continues to rise, that is, T-50≥5 and DT/Dt ≥0, the control unit continues to make all cooler groups work. The temperature decreases slowly, when T-50≥5 and DT/Dt<0, the control unit continues to make all cooler groups work; the temperature continues to drop, when -5<T-50<5, the control unit continues to make all cooler groups work Working; the temperature continues to decrease, when T-50≤－5 and DT/Dt≤0, the control unit sends a command to the cooler to exit a group of coolers; the temperature continues to decrease, T-50≤－5 and DT/Dt≤ 0, every 0.5min-1.5min, exit a group of cooler groups until all cooler groups exit; the temperature continues to drop, T-50≤-5 and DT/Dt≤0, the control unit continues to maintain the exit of all cooler groups state.

When T≥105°C, all cooler groups have been put into operation, and the control unit sends an alarm signal to the alarm. When the transformer changes from operation to standby, or the transformer trips due to an external fault, the transformer is in a zero-load state, and the control unit stops all cooler groups from working.

The present invention selects the real-time temperature of the transformer winding as the judgment basis instead of using the oil temperature of the top layer as the basis for starting and stopping the cooler group. This is mainly because during short-term emergency loads and external accidents, the current flowing through the transformer winding increases sharply, and the temperature difference between the winding and the top oil of the transformer increases rapidly. The time constant of transformer oil is very long (up to 200 minutes), so it may happen that the temperature of the oil on the top layer of the transformer has not yet risen enough to start the cooler group, and the hot spot temperature of the winding has reached a level sufficient to endanger the solid insulation. And because the cooler group is not put in in time, this high temperature will last for a longer time. Using the transformer winding temperature as the basis for starting and stopping the fan will dissipate more heat caused by high current in a timely manner and reduce damage to solid insulation.

The present invention selects the constant temperature value of transformer operation as 50°C. Under possible conditions, the operating temperature of the transformer should be within a relatively constant range to reduce the frequent exchange of moisture between the transformer oil and the solid insulation due to temperature changes, resulting in accelerated aging of the transformer solid insulation. The value of this constant temperature should not be too low, because the cooling capacity may not be able to maintain the temperature at a very low position under operating conditions; The situation will intensify. Moreover, when the ambient temperature is low and the load is not large, the high temperature cannot be achieved. Under the test conditions, the insulating paper has good insulating properties between 44 and 52 °C, and the value of the dielectric coefficient ε is the largest; the insulating paper has the largest dielectric loss tangent at 50 °C. Based on the above analysis and the actual operation data on site, the constant temperature value of the transformer operation is 50°C as the best.

The invention determines the control strategy of the cooler according to the real-time temperature T of the winding and the temperature change rate DT/Dt. Compare the real-time temperature T of the winding with the set constant temperature value of the transformer, and control the temperature of the transformer within the range of 50±5°C by controlling the switching of the cooler. The reason why the deviation of ±5°C is added is mainly to consider the possible existence of various errors. The time for calculating the rate of change DT/Dt can be calculated at intervals of one minute, and the accuracy can be guaranteed at this calculation interval. If the calculation interval is too short, there will be disadvantages of frequent adjustments. For the control of each cooler group, record the running times and status of each cooler group, and evenly distribute the switching times of each cooler group to avoid frequent switching of a single cooler group.

The purpose of the supplementary control rules of the present invention is to take into account abnormal conditions such as transformer defects and power outages. If the operating winding temperature of the transformer is higher than 105°C, it has exceeded the limit value of the winding temperature, and there is a potential safety hazard. Therefore, it is necessary to ensure that all cooler groups are turned on at this time, and an early warning is issued to eliminate risks. When the transformer is switched from running to standby, or after tripping due to an external fault, all fans will be withdrawn. The purpose is to slow down the temperature drop and prevent the water in the transformer oil from being separated out due to the temperature drop to form free water and damage the insulation.

The output terminals of the control unit are respectively connected with the relay coils of each cooler group to realize switching control of the coolers.

The beneficial effects produced by the present invention are: it can timely and effectively control the operation of the transformer cooler, thereby reducing the temperature of the transformer, ensuring that the transformer is not damaged, and improving its service life; it can switch the cooler group of the cooler to avoid It avoids the frequent switching of the cooler group, avoids the occurrence of switch failure, ensures the stable operation of the entire cooler, and makes the transformer run more stably.

Description of drawings

The present invention will be further described below in conjunction with accompanying drawing and embodiment, in the accompanying drawing:

Fig. 1 is the flowchart of the intelligent control method of transformer cooler of the present invention;

Figure 2 is the winding temperature change diagram of intelligent control and traditional control when the load fluctuates;

Figure 3 is a comparison chart of transformer cooler control for short-term emergency load.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

As shown in Figure 1, an intelligent control method for a transformer cooler includes the following steps:

1. The sensor collects the real-time temperature T of the transformer winding in real time;

2. Set the constant temperature value for transformer operation, the constant temperature value is 50°C;

3. The control unit determines the cooler control strategy based on the real-time temperature T of the transformer winding and the temperature change rate DT/Dt in step 1, where DT=△T is the temperature change, Dt=△t is the time interval, in order to avoid frequent start-stop cooling device group, the Δt is 1min;

When T-50≥5 and DT/Dt≥0, a set of cooler groups will be put into operation; if all cooler groups have been put into operation, this state will be maintained;

When T-50≥5 and DT/Dt<0, maintain the original state;

When -5<T-50<5, maintain the original state;

When T-50≤－5 and DT/Dt>0, maintain the original state;

When T-50≤－5 and DT/Dt≤0, one group of cooler groups will exit; if all cooler groups have exited, this state (self-cooling state) will be maintained.

In order to better realize the switching operation, the time interval Δt is 1 min.

In order to protect the transformer from being damaged, when T≥105°C, all cooler groups have been put into operation, and the control unit sends an alarm signal to the alarm to alarm.

In order to save energy, if the transformer is switched from running to standby, or the transformer is in a zero-load state after the transformer trips due to an external fault, all cooler groups will exit.

In order to better optimize the switching operation, in step 3, the control unit records the operation times and status of each cooler group;

When a group of cooler groups needs to be put into operation, the control unit selects the cooler group with the least number of times of operation among the cooler groups not put into operation;

When it is necessary to withdraw from a group of cooler groups, the control unit selects the cooler group that has been put into operation with the largest number of times among the cooler groups that have been put into operation to shut down.

The present invention adopts the hot spot temperature of the transformer winding as the judgment basis. Winding hot spot temperature (real-time temperature) can be obtained by using transformer winding optical fiber temperature measurement as a measurement method. If the transformer winding optical fiber temperature measurement device is not installed, the winding described in "GB 1094.2-1996 Power Transformer Part 2 Temperature Rise" can be used Temperature calculation method, the real-time temperature T of the transformer winding is obtained through calculation. When the present invention calculates DT/Dt, the time interval Δt is selected as one minute, so as to ensure measurement accuracy and avoid frequent start-up of cooler groups.

The transformer starts to work, the control unit receives the real-time temperature T of the transformer winding from the sensor in real time, and the control unit calculates the temperature change rate DT/Dt every 0.5min-1.5min. The temperature rises slowly, when T-50≤－5 and DT/Dt>0, the control unit does not send commands to the cooler, and the cooler group does not work; the temperature continues to rise, when -5<T-50<5 , the control unit does not send commands to the cooler, and the cooler group does not work; when T-50≥5 and DT/Dt≥0, the control unit sends a command to the cooler and puts in a group of cooler groups; the temperature continues to rise , that is, T-50≥5 and DT/Dt≥0, put in a set of cooler groups every 0.5min-1.5min until all the cooler groups are put into use; the temperature continues to rise, that is, T-50≥5 and DT/Dt ≥0, the control unit continues to make all cooler groups work. When T≥105°C, all cooler groups have been put into operation, and the control unit sends an alarm signal to the alarm. The temperature decreases slowly, when T-50≥5 and DT/Dt<0, the control unit continues to make all cooler groups work; the temperature continues to drop, when -5<T-50<5, the control unit continues to make all cooler groups work Working; the temperature continues to decrease, when T-50≤－5 and DT/Dt≤0, the control unit sends a command to the cooler to exit a group of coolers; the temperature continues to decrease, T-50≤－5 and DT/Dt≤ 0, every 0.5min-1.5min, exit a group of cooler groups until all cooler groups exit; the temperature continues to drop, T-50≤-5 and DT/Dt≤0, the control unit continues to maintain the exit of all cooler groups state.

When the transformer changes from operation to standby, or the transformer trips due to an external fault, the transformer is in a zero-load state, and the control unit stops all cooler groups from working.

Below by Fig. 2, Fig. 3 the implementation effect of the present invention is described in detail:

Based on the capacity of the transformer in the self-cooling state, the transformer load changes as follows: the load factor is 0.625 for 15 minutes, the load factor is 0.8 for 40 minutes, and the load factor is 0.4 for 20 minutes. Figure 2 is a diagram of the temperature change of the windings under intelligent control and traditional control when the load fluctuates.

Based on the capacity of the transformer in the self-cooling state, consider the cooler control results at the short-term emergency load with a 30-minute load factor of 1.5. Figure 3 is a comparison chart of transformer cooler control for short-term emergency load.

A comprehensive analysis of the two figures shows that according to the traditional control method, the temperature of the transformer winding will fluctuate greatly when the load changes, but under the control of the new control method, the temperature of the transformer winding can maintain a good stability. Under the influence of a 30-minute short-term emergency load, according to the traditional control method, the temperature of the transformer winding will rise to about 130°C and remain above 100°C for 60 minutes. However, according to the control method, the highest temperature of the transformer winding will not reach 100°C.

It can be seen that whether the intelligent control method of the transformer cooler keeps the winding temperature approximately constant when the load fluctuates, or prevents the transformer winding from overheating in the case of short-term emergency load, its effect is obviously better than the traditional control method .

It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the protection scope of the appended claims of the present invention.

Claims (5)

1. the intelligent control method of a transformer cooler, it is characterised in that comprise the steps:

One, the real time temperature T of Transformer Winding is obtained；

Two, set transformator run constant temperature angle value as, this constant temperature angle value is 50 DEG C；

Three, control unit determines cooler control according to the real time temperature T and rate of temperature change DT/Dt of the Transformer Winding of step one System strategy, wherein, DT=△ T is variations in temperature, and Dt=△ t is time interval, and △ t is 0.5min-1.5min；

When T-50 >=5 and DT/Dt >=0, then put into one group of cooler package；If all cooler package has been put into running, then tie up Hold this state；

As T-50>=5 and DT/Dt<0, then state of remaining stationary；

When-5 < T-50 < 5, then state of remaining stationary；

As T-50≤-5 and DT/Dt > 0, then state of remaining stationary；

When T-50≤-5 and DT/Dt≤0, then exit one group of cooler package；If all cooler package has dropped out operation, then tie up Hold this state.

The intelligent control method of transformer cooler the most according to claim 1, it is characterised in that: described time interval △ T is 1min.

The intelligent control method of transformer cooler the most according to claim 1, it is characterised in that: when T >=105 DEG C, entirely Portion's cooler package has been put into running, and control unit sends alarm signal to alarm equipment alarm.

The intelligent control method of transformer cooler the most according to claim 1, it is characterised in that: if transformator is by running Transfer to standby, or after transformator trips because of external fault, transformator is in 0 load condition, then all cooler package exit.

The intelligent control method of transformer cooler the most according to claim 1, it is characterised in that: in step 3, control The number of run of cooler package is often organized in unit record；

When needs put into one group of cooler package, control unit selects to put into operation in the cooler package that do not puts into operation number of times Few cooler package puts into；

When needs exit one group of cooler package, control unit selects to put into operation in the cooler package that put into operation number of times Many cooler package are closed.