阅读说明：本技术 一种电压互感器绕组内部温度监测系统和方法 (System and method for monitoring internal temperature of voltage transformer winding ) 是由 杨志祥 冯喜军 孙勇卫 *** 曹奇 唐璐 黄天佑 于 2020-05-25 设计创作，主要内容包括：本发明涉及一种电压互感器绕组内部温度监测系统和方法。一种电压互感器绕组内部温度监测系统,包括配电控制器、电流表、电压表和瞬间负载；所述配电控制器具有配电处理器；所述电流表和电压表,装设在配电控制器的一次端,与电压互感器的绕组输出端连接,还与所述配电处理器连接；所述瞬间负载装设在配电控制器的二次端,与所述配电处理器连接,通过所述配电处理器驱动与所述二次端的通断。本发明通过配电处理器精准的控制瞬时负载在检测电压互感器的内部绕组温度时与配电控制器二次端的接通与关断,使电压互感器内部绕组的等效电阻快速计算得到,即时发现电压互感器内部绕组的温度过限危害。(The invention relates to a system and a method for monitoring the internal temperature of a voltage transformer winding. A system for monitoring the internal temperature of a voltage transformer winding comprises a power distribution controller, an ammeter, a voltmeter and an instant load; the power distribution controller is provided with a power distribution processor; the ammeter and the voltmeter are arranged at the primary end of the power distribution controller, connected with the winding output end of the voltage transformer and also connected with the power distribution processor; the instant load is arranged at the secondary end of the power distribution controller, is connected with the power distribution processor, and is driven by the power distribution processor to be switched on or off at the secondary end. According to the invention, the switching-on and switching-off of the instantaneous load and the secondary end of the distribution controller are accurately controlled by the distribution processor when the temperature of the internal winding of the voltage transformer is detected, so that the equivalent resistance of the internal winding of the voltage transformer is rapidly calculated, and the over-limit damage of the temperature of the internal winding of the voltage transformer is immediately discovered.)

1. A system for monitoring the internal temperature of a voltage transformer winding is characterized by comprising a power distribution controller, an ammeter, a voltmeter and an instant load; the power distribution controller is provided with a power distribution processor;

the ammeter and the voltmeter are arranged at the primary end of the power distribution controller, connected with the winding output end of the voltage transformer and also connected with the power distribution processor; the instant load is arranged at the secondary end of the power distribution controller, is connected with the power distribution processor, and is driven by the power distribution processor to be switched on or off at the secondary end.

2. The voltage transformer winding internal temperature monitoring system of claim 1, wherein the transient load comprises a control component and a load component; the load assembly is erected at the secondary end of the power distribution controller;

the control assembly comprises a relay and a current limiter; the relay is provided with a normally open switch, and meanwhile, one end of the relay is connected with the current limiter, and the other end of the relay is grounded; the current limiter is connected with the power distribution processor;

the load component is provided with a protection resistor; and one end of the protection resistor is connected with one end point of the secondary end of the power distribution controller through the normally open switch.

3. The system of claim 2, wherein the protection resistor comprises a first protection resistor and a second protection resistor connected in parallel.

4. The system according to claim 3, wherein said first protection resistor is a fuse tube; the second protection resistor is a thermistor.

5. The system for monitoring the internal temperature of the winding of the voltage transformer according to claim 1, further comprising an alarm device connected to the power distribution processor for sending an alarm message to the outside according to the signal of the power distribution processor.

6. A method for monitoring the internal temperature of a winding of a voltage transformer adapted for use in the system for monitoring the internal temperature of a winding of a voltage transformer according to any one of claims 1 to 5, comprising the steps of:

s1, the power distribution processor drives the instant load and the secondary end of the power distribution controller to be switched on and off according to a preset strategy; the ammeter detects current detection data of the output end of the voltage transformer winding; the voltmeter detects voltage detection data of the output end of the voltage transformer winding;

s2, the power distribution processor receives the current detection data and the voltage detection data, and calculates an equivalent resistance value of the voltage transformer winding according to an equivalent resistance algorithm;

s3, the power distribution processor judges whether the equivalent resistance exceeds an alarm threshold value, if so, alarm information is sent out; if not, step S1 is executed.

7. The method for monitoring the internal temperature of the winding of the voltage transformer according to claim 6, wherein in the step S2, the equivalent resistance algorithm is as follows:

wherein R is_iIs an equivalent resistance value; u shape_nDetecting data for said pre-transient load turn-on voltmeter; u shape_sDetecting data for a voltmeter when the instantaneous load is switched on, namely the voltage detection data; i is_sAnd detecting data for an ammeter when the instantaneous load is switched on, namely the current detection data.

8. The method for monitoring the internal temperature of the voltage transformer winding according to claim 7, wherein in step S3, the equivalent resistance is calculated by the distribution processor for multiple times, and then an average of the multiple equivalent resistance values is found as the final equivalent resistance value.

9. The method for monitoring the internal temperature of the winding of the voltage transformer according to claim 6, wherein in step S1, the predetermined policy is: the instantaneous load instantaneous short-circuit duration is 100-300ms, and the two-time monitoring time interval is 1-5 h.

10. The method for monitoring the internal temperature of the winding of the voltage transformer according to claim 6, wherein before the step S1, the method further comprises:

and S0, the power distribution controller is powered on for the first time, and the steps S1-S2 are executed to obtain the equivalent resistance value of the voltage transformer winding as a sampling calculation initial value.

Technical Field

The invention relates to the field of transformer monitoring, in particular to a system and a method for monitoring the internal temperature of a voltage transformer winding.

Background

The intelligent switch of the power distribution network is used as important line load management and control equipment of a 10kV overhead line, has automatic positioning and cutting functions of line short circuit and earth fault, is typically applied to T joints of line head ends, segmentation points, large branch line head ends, trunk line ends and user lines, limits fault power failure range and power failure time to the minimum degree, and effectively improves power supply reliability of the power distribution network.

The device mainly comprises the following components: the common box type vacuum switch, the distribution controller, the voltage transformer and the control cable are shown in the lower drawing. The control cables are divided into two types, namely a power cable and a switch measurement and control cable; the power supply cable is used for electrically connecting the voltage transformer and the distribution controller, and the switch measuring cable is used for electrically connecting the vacuum circuit breaker and the feeder terminal.

The voltage transformer (PT for short) mainly realizes voltage monitoring of the power distribution overhead line and provides a power supply to the power distribution controller. Before and after 2006, a design scheme that a voltage transformer is arranged in a vacuum switch is designed, and due to the fact that the design scheme is convenient to install (a process of another voltage transformer, a supporting bracket and the like are omitted), the design scheme is widely used by provincial and municipal electric power companies with earlier power distribution automation construction such as Beijing and Shandong, and is counted by a certain company, and the number of the voltage transformers is not less than 2 ten thousand for the Shandong provincial electric power companies. With continuous operation, some problems of the built-in voltage transformer are gradually revealed.

Other accessories such as a current transformer (used for measuring and monitoring line current), a vacuum arc-extinguishing chamber (used for cutting off normal power supply load current and cutting off fault current when in fault) and an operating mechanism are integrated in the conventional switch;

from the anatomical view of the existing malfunctioning product, the source of the malfunction is directed to the built-in PT. In a fault recurrence test, the project group finds that the fault characteristics of the built-in PT are basically the same as the characteristics of the PT caused by turn-to-turn short circuit or interlayer short circuit. And meanwhile, the test also shows that the PT can continuously run for more than 3-7 hours even if the interlayer is short-circuited. In the process, the most obvious fault characteristics are that the temperature of the coil rises and the internal resistance becomes large.

Because built-in PT installs in high-pressure environment, current temperature sensor all has various drawbacks: for example, a wireless temperature sensor needs a built-in battery, and the battery needs to be replaced by regularly power failure due to the influence of the service life of the battery; due to the cost, the wireless passive temperature sensor and the optical fiber sensor are difficult to be applied in the field of distribution networks on a large scale. Moreover, they all have one of the biggest problems: the temperature measured by all the temperature sensors is the surface temperature. The internal temperature of the PT winding is transmitted to the surface through the thick epoxy resin insulating layer, so that the transmission speed is low, and the existing temperature difference is large. It is difficult for the conventional temperature sensor to accurately measure the internal temperature of the PT winding.

Patent document No. ZL201510429451.1 discloses an online temperature monitoring device for a voltage transformer, which is characterized by comprising a transformer for transforming voltage grades, a current collecting module for collecting primary current of the transformer, a voltage collecting module for collecting primary voltage of the transformer, an instantaneous load, and a control unit for calculating equivalent internal resistance variation of the voltage transformer side, controlling the input of the instantaneous load and controlling the on-off of primary equipment in the interval; the control unit controls the instantaneous load to be put in at regular time, and simultaneously collects the primary current and the primary voltage of the transformer, calculates the equivalent internal resistance variable quantity of the voltage transformer side according to the variable quantity of the current and the voltage, and deduces the temperature rise value of the internal winding of the voltage transformer according to the temperature coefficient of the lead material.

However, the temperature rise value derived from the temperature coefficient of the wire material generally has errors, so that the internal temperature monitoring of the existing voltage transformer is insufficient and needs to be improved.

Disclosure of Invention

In view of the defects of the prior art, the invention aims to provide a system and a method for monitoring the internal temperature of a voltage transformer winding, which can quickly identify whether the internal temperature of the voltage transformer is over-limit.

In order to achieve the purpose, the invention adopts the following technical scheme:

a system for monitoring the internal temperature of a voltage transformer winding comprises a power distribution controller, an ammeter, a voltmeter and an instant load; the power distribution controller is provided with a power distribution processor;

the ammeter and the voltmeter are arranged at the primary end of the power distribution controller, connected with the winding output end of the voltage transformer and also connected with the power distribution processor; the instant load is arranged at the secondary end of the power distribution controller, is connected with the power distribution processor, and is driven by the power distribution processor to be switched on or off at the secondary end.

Preferably, the voltage transformer winding internal temperature monitoring system, the instant load comprises a control component and a load component; the load assembly is erected at the secondary end of the power distribution controller;

the control assembly comprises a relay and a current limiter; the relay is provided with a normally open switch, and meanwhile, one end of the relay is connected with the current limiter, and the other end of the relay is grounded; the current limiter is connected with the power distribution processor;

the load component is provided with a protection resistor; and one end of the protection resistor is connected with one end point of the secondary end of the power distribution controller through the normally open switch.

Preferably, in the system for monitoring the temperature inside the voltage transformer winding, the protection resistor includes a first protection resistor and a second protection resistor connected in parallel.

Preferably, in the internal temperature monitoring system of the voltage transformer winding, the first protection resistor is a fuse tube; the second protection resistor is a thermistor.

Preferably, the system for monitoring the temperature inside the voltage transformer winding further comprises an alarm device connected with the power distribution processor and used for sending alarm information to the outside according to the signal of the power distribution processor.

A voltage transformer winding internal temperature monitoring method suitable for the voltage transformer winding internal temperature monitoring system comprises the following steps:

s1, the power distribution processor drives the instant load and the secondary end of the power distribution controller to be switched on and off according to a preset strategy; the ammeter detects current detection data of the output end of the voltage transformer winding; the voltmeter detects voltage detection data of the output end of the voltage transformer winding;

s2, the power distribution processor receives the current detection data and the voltage detection data, and calculates an equivalent resistance value of the voltage transformer winding according to an equivalent resistance algorithm;

s3, the power distribution processor judges whether the equivalent resistance exceeds an alarm threshold value, if so, alarm information is sent out; if not, step S1 is executed.

Preferably, in the method for monitoring the internal temperature of the voltage transformer winding, in step S2, the equivalent resistance algorithm is as follows:

wherein R is_iIs an equivalent resistance value; u shape_nDetecting data for said pre-transient load turn-on voltmeter; u shape_sDetecting data for a voltmeter when the instantaneous load is switched on, namely the voltage detection data; i is_sAnd detecting data for an ammeter when the instantaneous load is switched on, namely the current detection data.

In step S3, the equivalent resistance is calculated by the distribution processor calculating the equivalent resistance value a plurality of times, and then calculating an average of the equivalent resistance values as a final equivalent resistance value.

Preferably, in the method for monitoring the internal temperature of the winding of the voltage transformer, in step S1, the predetermined policy is: the instantaneous load instantaneous short-circuit duration is 100-300ms, and the two-time monitoring time interval is 1-5 h.

Preferably, before the step S1, the method for monitoring the internal temperature of the winding of the voltage transformer further includes:

and S0, the power distribution controller is powered on for the first time, and the steps S1-S2 are executed to obtain the equivalent resistance value of the voltage transformer winding as a sampling calculation initial value.

Compared with the prior art, the system and the method for monitoring the internal temperature of the voltage transformer winding provided by the invention have the advantages that the power distribution processor accurately controls the connection and disconnection of the instantaneous load and the secondary end of the power distribution controller when the internal winding temperature of the voltage transformer is detected, so that the equivalent resistance of the internal winding of the voltage transformer is quickly calculated, and the over-limit damage of the temperature of the internal winding of the voltage transformer is immediately discovered.

Drawings

FIG. 1 is a block diagram of an internal temperature monitoring system provided by the present invention;

FIG. 2 is a circuit diagram of a transient load provided by the present invention;

FIG. 3 is a flow chart of an internal temperature monitoring method provided by the present invention;

FIG. 4 is a data line graph of internal resistance values for 1# and 2# PTs measured using a bridge according to the present invention;

FIG. 5 is a data line graph of internal resistance values measured for 1# and 2# PTs using an internal temperature monitoring method provided by the present invention;

fig. 6-8 are line graphs of test data for instantaneous load access times of 100ms, 200ms, and 300ms, respectively, as provided by the present invention.

Detailed Description

In order to make the objects, technical solutions and effects of the present invention clearer and clearer, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Referring to fig. 1-3, the present invention provides a system for monitoring the internal temperature of a winding of a voltage transformer, which comprises a distribution controller TRAN2, an ammeter a1, a voltmeter V and an instantaneous load SS; said power distribution controller TRAN2 having a power distribution processor (not shown);

the ammeter A1 and the voltmeter V are arranged at the primary end of a distribution controller TRAN2, connected with the winding output end of the voltage transformer and further connected with the distribution processor; the instantaneous load SS is arranged at the secondary end of a distribution controller TRAN2, is connected with the distribution processor, and is driven by the distribution processor to be switched on and off with the secondary end.

Specifically, the power distribution processor is an original device in a power distribution controller TRAN2, and is not limited; the ammeter A1 and the voltage are common detection devices in the field, and are not limited, the detection periods of the ammeter A1 and the voltage are the same and are both 10-50ms once, and the preferred detection period is 20ms for detecting data once; the instant load SS can be switched on and off accurately by the power distribution processor. An ammeter A1 and a voltmeter V measuring loop are added at the primary end of a transformer TRAN2 (transformation ratio 220:35) in a distribution controller TRAN 2; the secondary end is provided with an instantaneous load adjusting loop, and the impedance of the instantaneous load and the internal resistance of the voltage transformer are in the same order of magnitude (generally, several omega levels). The distribution processor of the distribution controller TRAN2 controls the instantaneous load to be put into use at regular time, detects the variable quantities of the current and the voltage of the primary circuit of the transformer (TRANs2), calculates the equivalent internal resistance variable quantity of the PT side according to the variable quantities of the parameters, and can judge the risk state of the internal temperature of the internal winding of the voltage transformer in advance according to the equivalent internal resistance variable quantity so as to give an alarm.

Correspondingly, the invention also provides a method for monitoring the internal temperature of the voltage transformer winding, which comprises the following steps:

s1, the power distribution processor drives the instantaneous load SS and the secondary end of the power distribution controller TRAN2 to be switched on and off according to a preset strategy; the ammeter A1 detects current detection data of the output end of the voltage transformer winding; the voltmeter V detects voltage detection data of the output end of the voltage transformer winding;

s2, the power distribution processor receives the current detection data and the voltage detection data, and calculates an equivalent resistance value of the voltage transformer winding according to an equivalent resistance algorithm;

s3, the power distribution processor judges whether the equivalent resistance exceeds an alarm threshold value, if so, alarm information is sent out; if not, step S1 is executed.

Preferably, in step S3, the power distribution processor may calculate the temperature inside the voltage transformer at that time according to the equivalent resistance and the temperature coefficient of resistivity of the winding material (e.g., copper) inside the voltage transformer, and further display the temperature to the outside, where the display mode may be a fuzzy display (e.g., displaying different colors to indicate the temperature) or an accurate display (displaying different data to indicate the temperature).

Preferably, in this embodiment, the instant load SS includes a control component and a load component; the load assembly is erected at the secondary end of the distribution controller TRAN 2;

the control assembly comprises a relay FZ and a current limiter D2; the relay FZ is provided with a normally open switch, one end of the relay FZ is connected with the current limiter D2, and the other end of the relay FZ is grounded; the current limiter D2 is connected with the power distribution processor;

the load component is provided with a protective resistor R1/R2; one end of the protection resistor R1/R2 is connected with one end point of the secondary end of the distribution controller TRAN2 through the normally open switch.

In the voltage transformer winding internal temperature monitoring system, the protection resistor comprises a first protection resistor R1 and a second protection resistor R2 which are connected in parallel.

Preferably, in this embodiment, the first protection resistor is a fuse tube; the second protection resistor is a thermistor.

Specifically, in fig. 2, the wiring diagram of the secondary side of the distribution controller TRAN2 and the distribution processor is not directly shown, but a load terminal X1 and a control terminal X2 are used as intermediate connection devices; the control component is directly controlled by the power distribution processor, the control component can be activated by a control signal DO05 (for example, 24V voltage) after the power distribution processor outputs a certain high level, after the current limiter D2 is passed, the relay FZ is electrified, and then a normally open switch 3-4/5-6 on the relay FZ is closed; meanwhile, in order to make the control component form a loop, the relay FZ is grounded, in this embodiment, the grounding is implemented by connecting the terminal 24VGND to ground; thereby controlling the passage of the load assembly and the secondary end of the distribution controller TRAN 2; the time for maintaining the load assembly on can be set to 0-1000 ms. In this embodiment, the connection terminal AC35VL in the load component is connected to the phase line in the secondary side of the distribution controller TRAN2, and the connection terminal AC35VN is connected to the neutral line in the secondary side; two normally open switches 3-4/5-6 are arranged on the relay FZ in the control assembly, and after the relay FZ is electrified, the normally open switches are closed, so that the short circuit of the secondary end of the distribution controller TRAN2 is finally realized, and the equivalent resistance of the internal winding of the voltage transformer is realized. The corresponding working principle of the transient load is as follows: referring to fig. 2, DO05 is a control signal (off) for the distribution processor to control the operation of the relay FZ (preferably, model G2R-1A-E-24VDC) to receive the trigger signal of the distribution processor, so that the secondary terminal of the distribution controller TRAN2 (AC 35VL and AC35VN in fig. 2, respectively) simulates the switching on/off of the instantaneous load according to the DO05 pulse time. Wherein protection resistance R1/R2 is in order to prevent relay FZ's normally open switch bonding setting, respectively with the two normally open switches of relay FZ wherein, protection resistance R1 is the fuse tube, and protection resistance R2 is PTC thermistor.

Preferably, in this embodiment, the power distribution system further includes an alarm device (not shown) connected to the power distribution processor, and configured to send an alarm message to the outside according to a signal of the power distribution processor. It should be noted that the alarm manner of the alarm device described herein includes sound, LED lamp or screen display; if the LED lamps are used for displaying, a plurality of LED lamps can be used for displaying different temperature levels, and lamps with different colors can also be used for displaying different temperature levels; if the LED screen displays, the internal temperature value and the danger level (the high, the low and the medium can be positioned) can be directly displayed.

Preferably, in this embodiment, in step S2, the equivalent resistance algorithm is:

wherein R is_iIs an equivalent resistance value; u shape_nDetecting data for voltmeter V before the instantaneous load is switched on; u shape_sVoltage meter V detection data when the instantaneous load is on, i.e. the voltage detection data; i is_sThe current meter a1 detects data for the instant load on, i.e., the current detection data.

Preferably, in step S3, in the embodiment, the equivalent resistance is calculated by the power distribution processor calculating the equivalent resistance value a plurality of times, and then calculating an average of the plurality of equivalent resistance values as the final equivalent resistance value. Here, in the case where the instantaneous load is turned on, the current data and the voltage data are detected several times during the time period in which the load is continuously turned on, and further, the current data and the voltage data are calculated several times to obtain a plurality of equivalent resistance values, and an average value is obtained to prevent erroneous determination.

Preferably, in this embodiment, in step S1, the predetermined policy is: the instantaneous short-circuit duration of the instantaneous load SS is 100-300ms, and the time interval of two-time monitoring is 1-5 h. Preferably, the short-circuit duration is 100ms, and the two-time monitoring time interval is 5 h. Preferably, in step S3, after the alarm message is sent out, step S1 needs to be executed, but the corresponding predetermined policy needs to be changed, wherein the two-time monitoring time interval is modified to 10-30min, so that the equivalent resistance value of the internal winding of the voltage transformer can be ensured to be grasped in real time.

Referring to fig. 6-8, the instant load access time is 100mS, 200mS, and 300mS, respectively, the interval time is 10 minutes, and the test is performed for more than 4 hours, it can be clearly known that the instant load access has little influence on the temperature rise of the PT itself, and the lateral deviation of the test result is about ± 0.6 Ω, which meets the requirement of the test precision. The final preferred mode is 100ms in view of the increased efficiency.

Preferably, in this embodiment, before the step S1, the method further includes:

and S0, electrifying the distribution controller TRAN2 for the first time, executing the steps S1-S2, and obtaining the equivalent resistance value of the voltage transformer winding as a sampling calculation initial value. Generally, the initial value of the sampling calculation is approximate to 0, and is set to 0 in the initial stage of the equipment, and the initial value of the sampling calculation is performed once in the first working of the low-voltage controller and is used for performing one evaluation on the self device of the equipment.

Comparing the internal resistance result of the voltage Transformer measured by the bridge with the test result of the internal temperature monitoring method provided by the invention, please refer to fig. 4-5, wherein, two PTs (Potential transformers) are kept at a constant temperature of 110 ℃, and after the constant temperature is kept for 5 hours, the measured resistance value of the bridge is changed (measured once in half an hour) in the cooling process of the two PTs as shown in fig. 4; the resistance changes (measured once in half an hour) measured for the two PT cooling processes using the internal temperature monitoring method provided by the present invention are shown in fig. 5; therefore, the result obtained by the method for monitoring the internal temperature of the voltage transformer is similar to the result obtained by the actual measurement of the bridge, and the accurate measurement of the internal winding of the voltage transformer can be realized.

It should be understood that equivalents and modifications of the technical solution and inventive concept thereof may occur to those skilled in the art, and all such modifications and alterations should fall within the scope of the appended claims.