RU108855U1 - STATIONARY DEVICE FOR MONITORING, DIAGNOSTICS AND PROTECTION OF POWER TRANSFORMERS WITHOUT DISCONNECTING THEM FROM LOAD - Google Patents

Abstract

A device for monitoring, diagnostics, protection of transformers against deformations of windings and damage (deterioration of properties) of winding insulation, moisture content of insulation, calculation of the temperature of the most heated points of winding insulation without disconnecting them (transformers) from the mains and load, characterized by the fact that it contains sensors for the state of insulation resistance and the moisture content of the winding, in series with which the reacting organ is connected, characterized in that the sensors of the resistance state and moisture content of the winding insulation are made in the form of electrodes made of electrically conductive foil located between the insulation layers of each phase and all voltages, and the reacting organ is made in the form of LEDs according to the number of sensors , the first conclusions of which are the inputs of the reacting organ, the second outputs are combined and connected to the first input of the unit for measuring the resistance and moisture content of the winding insulation, a current control unit in the neutral of the winding is introduced, which is connected between the case and the neutral of the transfo winding The output of the said block is connected to the second input of the winding insulation resistance measuring unit, the first output of which is connected to the input of the block for collecting information from all diagnostic systems and making a decision, and a block for measuring and controlling the temperature of the hottest point is connected to this block, which receives information from the ammeter and, for example, a trip unit of a protective device of a transformer and / or a relay about the load factor of a transformer, a communication unit with a neutral of a transformer, output signals from a unit for calculating the temperature of the hottest point and an insulation resistance monitoring unit go

Description

This utility model relates to electrical engineering and can be used for on-line monitoring, diagnostics, protection of power transformer windings according to a number of parameters, such as the temperature of the most heated insulation point of the winding, insulation resistance, moisture insulation during operation without disconnecting them from the network and load.

The invention is known from the prior art (patent RU No. 2392684) for controlling the quality of paper insulation of a transformer, which consists in transmitting photo-images from the insulation of a transformer using fiber optic cables to determine its color coordinates and calculate the degree of polymerization. The degree of polymerization is estimated in relation to the paper insulation of the transformer without disconnecting the transformer using non-destructive testing methods. The degree of polymerization of paper insulation is calculated by determining the chromaticity coordinates x and y and their dependence on the degree of polymerization. The disadvantages of this invention are as follows: the transformation of an optical signal into an electronic signal is an extremely expensive procedure (up to 10% of the cost of the transformer), the cost and complexity of manufacturing the sensors is very high, the sensors do not allow to identify the damaged section of the winding and the type of damage to its insulation.

A device is known (patent RU 2393494) for continuous monitoring of the signal of partial discharges in the isolation of three-phase high-voltage devices in operating conditions. This device is used to measure partial discharge (PD) signals in the electrical insulation of three-phase high-voltage devices under operating voltage in order to diagnose the occurrence of insulation defects. The essence is that the active part of a three-phase high-voltage apparatus is used as a sensor-receiver of PD signals. In this case, PD signals are measured simultaneously on all three phases of the high-voltage apparatus at the common point of the active part of this apparatus using low-voltage voltage transformers connected according to an open triangle circuit. This method has several disadvantages associated with various interference, the level of which is very high when the transformers are working. Devices for measuring PD do not provide the proper level of separation of PD signals from interference, because of this the reliability of determining insulation defects in real conditions is not ensured. Control devices do not allow recording the amplitude-phase distributions of PD signals, and without this, the determination of insulation defects is practically impossible.

Known CN patent No. 101726514 which describes a method for assessing the moisture content of insulation. The essence is that the moisture content is estimated by the polarized spectrum curve, which is based on the return voltage. The disadvantages of this method are that it is not possible to accurately determine the moisture content of certain parts of the insulation, there is a strong dependence of the measurement results on the physicochemical parameters of the oil, which carries an error due to the decomposition products of the oil and solid insulation.

The purpose of the utility model is to develop a more reliable and efficient method for monitoring, diagnosing insulation resistance, temperature of the warmest points of the winding, moisture content of the insulation of the transformer windings during its operation, regardless of its design features and providing continuous protection of the transformer during operation and its operational disconnection from network in the event of the occurrence of deformations of the transformer windings or their damage, as well as the rational use of cooling systems transformer.

This problem is solved due to the fact that the claimed device for monitoring, diagnostics, protection of transformers from winding deformations and damage (deterioration) of winding insulation, moisture insulation, temperature calculation of the most heated winding insulation points without disconnecting them (transformers) from the mains and load, characterized in that it contains sensors of the state of insulation resistance and moisture content of the winding, in series with which a reacting organ is switched on, characterized in that, in order to increase reliability in operation, the sensors of the resistance and moisture state of the insulation of the winding are made in the form of electrodes of conductive foil located between the insulation layers of each phase and all voltages, and the reacting body is made in the form of LEDs according to the number of sensors, the first conclusions of which are the inputs of the reacting body, the second conclusions combined and connected to the first input of the winding insulation resistance and moisture measurement unit, a current monitoring unit is introduced in the neutral of the winding, which is connected between the case and the neutral transformer windings, the output of the indicated unit is connected to the second input of the winding insulation resistance measuring unit, the first output of which is connected to the input of the information collection unit from all diagnostic systems and making the decision, the temperature measurement and control unit of the most heated point receiving information is also connected to this unit from the ammeter and, for example, the trip unit of the transformer protective device and / or relay on the load factor of the transformer, the communication unit with the transformer neutral, the output signals go to information gathering device and from there to the monitor (display), with the help of which people are informed about the condition of the equipment, to the cooling control system, to the shunt trip of the circuit breaker or other protective device of the transformer on the high voltage side, the same way the diagnosis is made according to the following symptoms: the percentage of moisture content within normal limits is 0.6% of the mass of solid insulation, over 1.8% the electric strength begins to decrease, aging increases azhnoy isolation, enhanced oil oxidation rate more than 3.5% of the paper begins to flake, 8% - requires urgent output transformer repair; Significant aging occurs at temperatures above 130 ° C, in connection with this, a number of temperatures were determined in the device, upon reaching which the cooling system functioned with enhanced power: starting from 90 ° C, the first signal was given, when the temperature reached 115-120 ° C at full power, upon reaching 135 ° C a signal is sent to the operator, at 140 ° C the transformer is switched off; gas is released at temperatures above 140 ° C, bubbles reduce the electric strength by 25-40%, but an increase in moisture to 3.5% leads to a decrease in the temperature of the occurrence of bubbles to 120 ° C; the critical temperatures of the most heated winding insulation points in the absence of overload are 120 ° C, for a short-term 160 ° C, for a long 130 ° C.

The technical result provided by the given set of features is to instantly obtain a reliable information picture about the equipment resource and condition (diagnosis) of the power transformer windings according to a number of the most important parameters, such as the temperature of the most heated point of the winding insulation, insulation resistance, insulation moisture, by a method that does not susceptible to external negative influences, transformer protection, optimal use of the cooling system, prevention emergency outages of transformer equipment, increasing the reliability of the operation of the transformer.

The essence of the utility model is illustrated by drawings, which depict:

- figure 1 is a diagram of the installation of the electrodes and the connection of a stationary monitoring and diagnostic device (UMDS) to the power transformer;

- figure 2 is a diagram of UMDS;

- figure 3 is an electric diagram for calculating the temperature of the most heated insulation points of the winding.

Table 1 provides a description of the blocks (elements) of the UMDS device.

Table 2 shows the elements geographically located in the power transformer.

Disclosure and implementation of a utility model.

The first essential sign to achieve the above technical result is the presence of sensors for monitoring the insulation resistance, moisture content of the insulation, which are made in the form of electrodes of conductive foil located between the insulation layers of all phases and for all voltages.

The second significant feature is that there is a unit in which the temperature is calculated and controlled by the most heated insulation points of the windings, which receives information from the ammeter and, for example, the release of the circuit breaker and / or relay about the load factor of the transformer. The output signals from this unit go to the transformer cooling control system and to turn off the transformer.

The third significant feature is that the connection of the electrodes with the UMDS is carried out by a wire that is resistant to vibration, shock and linear loads, acoustic noise resistant to aggressive environments, having an electric shield that protects the wire from electromagnetic fields.

The fourth significant feature is that the UMDS contains a unit for protecting the device itself from excessively high voltage when a short circuit occurs in the windings or if it gets on the electrodes.

This device UMDS refers to the stationary type, i.e. it must first be installed in a transformer that is temporarily disconnected from the network during the installation of this device, and then this device allows the desired parameters during the operation of the transformer over its life of 20 years.

We list the elements (table 1) included in the UMDS, then describe the principle of operation of the device.

The principle of UMDS is that the sensors for monitoring the insulation resistance, moisture content of the insulation are made in the form of electrodes from an electrically conductive foil, the unit for measuring and monitoring the temperature of the most heated point is also installed, which receives information from the ammeter and, for example, the trip unit and relay, on the load factor of the transformer, communication unit with transformer neutral. The output signals go to the information collection device and from there to the monitor, to the cooling control system, to the release of the circuit breaker or other protective device of the transformer.

This placement of the electrodes shown in figure 2, due to the fact that the most heated part of the winding is at a level of from 0.7 to 0.8 of its height.

The control sensor is an electrode made of conductive foil. It is located between the insulation layers and covers both sides. The peculiarity of the foil is that its thickness and weight are 1.5-2 times less than the smallest fiber optic sensors, high mechanical strength, it is more elastic, stable electrochemical and electrophysical characteristics.

Table 1.
The purpose of the blocks UMDS Item number Appointment one calculation of the temperature of the most heated point 2 measured harmonic current on the low voltage side (LV) 3 measured transformer load factor four rated current on the LV side 5 nominal eddy current loss at the location of the warmest point 6 reactive organ 7 insulation resistance 8 communication 9 display (monitor) 10 signaling 11, 12 Light-emitting diode 13 protection of a controlled power transformer 14, 15 relay 16, 17 control button 18, 19 adjustable resistor twenty current source 21, 22, 23, 24 contact 25 collecting information from diagnostic systems, making decisions

Indicated in figure 2, the placement of the sensors allows you to control the insulation resistance of the layers (electrode-winding; electrode-case). Each of the electrodes sends a signal to the reacting organ 6. It is designed for all sensors and sends a signal to the display about the readings of each of the sensors. Block 6 is also connected to the first input of block 7. The neutral of the power transformer is connected to the second input of block 7, through block 8. The first output of block 7 is connected to block 10 (LEDs), and the second to the trip circuit 13, through block 25, to an independent release of the circuit breaker.

Table 2.
Additional items 26 LV transformer winding 27 electrode (foil) 28 transformer high voltage (HV) winding 29th transformer housing thirty transformer neutral 31 transformer magnetic circuit

Block 8 contains a resistor, surge suppressor or arrester, capacitor. This is necessary to limit the voltage at the second input of block 7 in the event of a neutral potential displacement with respect to the ground caused by a short circuit, as well as when an unacceptably high voltage gets on the electrodes.

Block 7 includes a relay 14 and 15 and the control buttons 16 and 17 with a light indicator. When a current greater than their settings flows through the relay, they operate and become self-holding via contacts 21 and 22. The buttons 16 and 17 are returned to the initial state. The settings of the relays 14 and 15 are set by the resistors 18 and 19. The LEDs 11 and 12 indicate the type of insulation damage. The device is powered from a current source 20, but can also from the operating current selected at the substation.

When moisture enters the oil, the insulation of the windings is wetted. Insulation resistance drops sharply. The current flowing through the housing, insulation, sensor, block 6, relay 14, increases. Relay 12 is activated and through pin 21 it becomes self-holding, and LED 11 lights up, indicating moisture insulation. The location is determined by the glow of one of the LEDs of block 6.

When a circuit is closed due to the arc and ionization in the insulation layers, due to partial or complete burnout, the resistance of the insulation layer 3 decreases sharply and the current in the circuit increases: neutral 9, relay 15, block 6, electrode and insulation. The relay 15 is activated and through pin 22 it becomes self-holding. The turn-on LED is illuminated. In circuit 13 through contacts 23 and 24, a trip signal is sent to the circuit breaker. The defective element is determined by the glow of the LED block 6.

When an earth fault occurs, the insulation resistance drops rapidly due to the earth fault current. Together, relays 14 and 15 are activated and become self-holding. LEDs 11 and 12 light up, signaling a short circuit. A damaged element is determined by block 6.

The connection of the electrodes with UMDS is carried out by a wire that is resistant to vibration, shock and linear loads and to acoustic noise, resistant to low atmospheric pressure up to 0.13 kPa and high atmospheric pressure up to 295 kPa. To give flexibility, conductors twisted from many wires of small diameters can be used. The wire is coated with an external protective coating, which protects it from oxidation. Nickel, tin or silver are used as such a coating. Silver-plated wire is used, since this metal has a complex of unique properties. Firstly, silver is a good conductor (it has the highest electrical conductivity among metals). Secondly, it has high resistance to aggressive environments. Thirdly, silver has excellent solderability. For insulation, fluoroplastic films of various classes are used, which have unique electrical, mechanical, anti-corrosion properties. The use of polyimide-fluoroplastic films allows for flexibility and weight reduction. The insulation of the wire should consist of one or more materials, one of which carries an electric load, and the others give the composition the necessary mechanical strength (resistance to bursting, abrasion, etc.) and other specific properties. An electric shield protects the wire from electromagnetic fields. To do this, a braid of copper, tinned copper, nickel-plated copper or silver-plated copper wire is applied to the product. The protective cover of the wire is made of heat-resistant fibers or tapes, which are impregnated with special compounds. The wires are resistant to atmospheric condensed precipitation (frost and dew), solar radiation, oils, fuels and molds and they do not spread combustion. The service life of the wires is about 20 years.

The temperature of the warmest insulation points of the winding determines the reduction in insulation life and the potential risk of gas bubbles during overloading. Having information about the temperature of the most heated points at each moment of the transformer’s operation under various loads and constantly changing environmental conditions, it becomes possible to diagnose the condition of the transformer most quickly and accurately.

The temperature measurement element of the most heated points 1, including blocks 2, 3, 4, 5. From the ammeter installed on the low side, current data from each of the three phases is supplied. Block 3 determines the load factor of the transformer or receives data about it. In most modern circuit breakers or relay protection devices installed on the high voltage (HV) side, there is a function for determining K. Based on the data on K, the values of the rated currents and the nominal loss of eddy currents at the location of the most heated point are taken from blocks 4 and 5. In block 1, the temperature of the most heated points is calculated. The calculation is made for winding LV, because the temperature in it is much higher due to worse cooling conditions. The temperature data is sent to block 25, to display 9. In block 25, the temperature data of the most heated points are analyzed and the corresponding signal is supplied to the cooling system to enhance or attenuate its work intensity. This will allow more efficient use of it, increase the life of the cooling system, reduce energy costs for its operation.

An increase in the temperature of the upper layers of oil with respect to the ambient temperature consists in the fact that an increase in current in the transformer will lead to an increase in losses in the transformer and this will lead to an increase in temperature as a whole. This temperature change depends on the mass of the main structural elements of the transformer: magnetic circuit, winding, oil, as well as the inertia of the heat transfer of the transformer elements.

Due to the similarity between heat transfer and electric charge transfer, an equivalent electrical circuit can be used to solve the heat transfer problem.

The heat generated by the losses in the transformers is absorbed by the oil and transferred to a heat exchanger, which in most cases is an oil air cooler. The fan, if provided by the design, forcibly dissipates heat into the environment. Nonlinear properties of heat resistance are associated with many physical parameters of a real transformer.

The thermal equation of the hottest point is based on the circuit shown in figure 3.

Differential equation for an equivalent circuit

where q _w is the heat generated by losses at the location of the most heated point, W;

C _{th-H B} - winding specific heat at the location of the most heated point of phase B, W. min / ° C;

C _{th-H C} - winding specific heat at the location of the most heated point of phase C, W. min / ° C;

R _{hH B} - heat resistance at the location of the most heated point of phase B, ° C / W;

R _{hH C} - heat resistance at the location of the most heated point of phase C, ° C / W;

t is the time, s;

n is a well-known parameter that depends on the cooling method;

Θ _HB - temperature at the location of the most heated point of phase B, ° С;

Θ _HC - temperature at the location of the most heated point of phase C, ° C;

Θ _H is the temperature of the most heated point;

Θ _{oil B} - temperature of the upper layers of oil of phase B, ° С;

Θ _{oil C} is the temperature of the upper layers of oil of phase C, ° C.

Equation (1) is reduced to the following equation:

where P _EC-R is the nominal eddy current loss at the location of the most heated point (determined at the factory of the equipment manufacturer);

I _h is the rms current in a harmonic of order h;

I _R is the rms current at rated frequency and rated load;

h is the harmonic order;

I _pu - load current per unit value;

K is the load factor of the transformer.

Nonlinear heat resistance is associated with many physical parameters of a real transformer:

where ΔΘ is the temperature change of the most heated point in a certain period of time.

Diagnosis occurs by the following symptoms.

The percentage of moisture within normal limits is 0.6% by weight of solid insulation. Over 1.8%, the electric strength begins to decrease, the aging of paper insulation increases, and the rate of oil oxidation increases. Over 3.5% of the paper begins to peel. More than 8% - urgent need for a transformer for repair.

Substantial aging occurs at temperatures above 130 ° C. In this regard, a number of temperatures were determined in the device, upon reaching which the cooling system operated with enhanced power. Starting at 90 ° C, the first signal was applied. Upon reaching 115-120 ° C, the cooling system operates at full capacity. Upon reaching 135 ° C, a signal is given to the operator. At 140 ° C, the transformer is switched off.

Gas is released at temperatures above 140 ° C. Bubbles reduce electrical strength by 25-40%. But an increase in moisture to 3.5% leads to a decrease in the temperature of the appearance of bubbles to 120 ° C.

Critical temperatures of the most heated winding insulation points in the absence of overload were detected - 120 ° C, for a short-term 160 ° C, for a long 130 ° C.

When monitoring and diagnosing, the ratio of the parameters controlled by the device to each other is also taken into account, which avoids false alarms and improves the accuracy of the device.

The advantages of the above device.

The above device will allow you to monitor, diagnose and protect the power transformer according to a number of parameters, such as the temperature of the most heated point, insulation resistance, insulation moisture without disconnecting the transformer from the network (but this device is previously installed), taking into account the non-linearity of the load, the changing ambient temperature medium with a signal to the cooling system based on sensors of conductive foil connected to the device by means of a wire resistant to Sem aggressive influences, as well as a device capable of protecting itself in case of contact of high voltage to the sensing sensor. The device allows you to get a reliable picture of the resource of equipment, protects the transformer by supplying a signal to trip the opening circuit breaker, as well as low cost and simplicity. This increases the uninterrupted power supply of consumers of electric energy.

List of sources for consideration during the examination

1) Kozlov V.K., Sabitov A.Kh., Sabitov I.Kh. A method of controlling the quality of paper insulation of a transformer. Patent for invention RU 2392684, cl. H01F 41/12, G01R 31/12, 2009

2) Poles B.C. A device for continuous monitoring of the signal of partial discharges in the isolation of three-phase high-voltage devices in operating conditions. Patent for invention RU 2393494, cl. G01R 31/02, 2009.

3) Ming Dong, Shiqiang Wang, Jianlin Wei, Shuangsuo Yang, Zheng Yu, Guanjun Zhang, Xiangquan Zhang. Oil-immersed type transformer solid insulation moisture content assessment method based on return voltage. Patent CN 101726514 (A), CL G01N 27/00: G01R 31/00, 2009.

Claims (1)

A device for monitoring, diagnostics, protection of transformers from winding deformations and damage (deterioration) of winding insulation, insulation moisture, temperature calculation of the most heated winding insulation points without disconnecting them (transformers) from the mains and load, characterized in that it contains insulation resistance state sensors and humidity of the winding, in series with which a reacting organ is turned on, characterized in that the sensors of the resistance state and moisture content of the winding insulation are made in the form of electrodes of conductive foil located between the insulation layers of each phase and all voltages, and the reacting body is made in the form of LEDs according to the number of sensors, the first conclusions of which are the inputs of the reacting organ, the second conclusions are combined and connected to the first input of the insulation resistance and moisture measurement unit winding, a current monitoring unit is introduced in the neutral of the winding, which is connected between the housing and the neutral of the transformer winding, the output of this unit is connected to the second input of the measurement unit with insulation resistance of the winding, the first output of which is connected to the input of the information collection unit from all diagnostic systems and making the decision, also the temperature measurement and control unit of the most heated point is connected to this unit, receiving information from the ammeter and, for example, the trip unit of the transformer protective device and / or a relay about the load factor of the transformer, a communication unit with the neutral of the transformer, the output signals from the temperature calculation unit of the most heated point and the insulation resistance control unit go a data acquisition device and from there to a monitor (display) with which people are informed about the state of the equipment to a cooling control system for shunt trip circuit breaker or other protective device to the transformer high voltage side.