RU105536U1 - MOBILE 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 from winding deformation and damage (deterioration) of the insulation of the windings without disconnecting them (transformers) from the mains and load, characterized in that it contains the outputs of the measuring elements (current, voltage, frequency) included in each circuit phases of the primary and secondary windings, which are connected to the output of the element that sets the time for receiving data and calculation, with the inputs of the blocks for calculating the active resistance, bringing the primary voltage to the secondary, calculating the voltage difference, calculating the voltage drop across the active resistances, bringing the inductance value to the nominal frequency, the outputs of which are connected to the corresponding inputs of the current derivative calculation blocks for the primary and secondary voltages, calculating the average voltage value, calculating the inductance, calculating the average inductance values for all voltages, all phases for a specified period of time, calculating the deviations of the active resistance and inductance for all voltages, in all phases for a specified period of time, relative to the phases and nominal values, which are determined by the manufacturer of the equipment during appropriate tests, after which the data are transmitted to the inductance and active resistance control unit for primary and secondary voltages and all phases, from where information is transmitted to the unit uniting information from all control, monitoring and diagnostic devices, makes a decision on the obtained values (deviations) (deviation for active and inductive

Description

This utility model relates to electrical engineering and can be used for operational monitoring, diagnostics of windings and protection of power transformers during operation without disconnecting them from the network and load.

From the existing level of technology the invention is known (patent No. 2388004) for the diagnosis of inductive windings, which consists in comparing, at the rated reactive current, the tested inductive winding with the reactance of a faultless induction coil of the same type. Comparison of the reactance of the tested inductive winding is carried out by turning it on with the help of auxiliary electric circuits to the terminals of the secondary winding of a three-phase transformer with an adjustable voltage. The disadvantages of this technical solution are the high complexity (the need for a transformer to test), the lack of instant monitoring (the need to disconnect the load of the tested device), low accuracy and reliability, due to the fact that the results on a power transformer disconnected from the network are very different from the results obtained in operating mode (due to temperature conditions, electric field strength).

A known device (patent CN 101707127) carries out continuous monitoring of the insulation status of the oil-filled transformer. The principle is that when the insulation is in a state close to breakdown, a change in the value of the capacitance occurs. The change in capacitance is calculated and it determines the degree of aging and damage to the insulation of the winding. The disadvantages of this device are as follows: high error due to the influence of electromagnetic fields (the device is connected to the windings and during the process of receiving and transmitting data, an external negative effect on the data occurs), the inability to use it for powerful transformers, the need to disconnect the transformer from the network and install this device, which leads to an increased risk of transformer failure and is of great complexity.

Closest to the proposed invention is a device (ed. Certificate. USSR N 1821759) - a prototype. It serves to control and protect the windings of the power transformer during the test. This device measures the voltage on the high and low voltage side, as well as the current on the low side. The control is carried out by the magnitude of the inductance of the transformer, which is calculated as the ratio of the average voltage to the derivative of the current, the average value of the inductance and the deviation of the obtained value of the inductance from the nominal rate. The disadvantage of this device is its low accuracy, due to the lack of control of other parameters, the effect of non-linear loads (harmonics) is not taken into account, narrow applicability in view of the binding to a number of design features of powerful transformers.

The purpose of the utility model is to develop a more reliable and efficient method for monitoring, diagnosing windings, including insulation, of a transformer during its operation, regardless of its design features and ensuring continuous protection of the transformer during operation, and in the event of deformation of the transformer windings or their damage to the emergency disconnection of the transformer from the network.

This problem is solved due to the fact that the claimed device for monitoring, diagnostics, protection of transformers from deformation of the windings and damage (deterioration) of insulation of the windings without disconnecting them (transformers) from the mains and load, characterized in that it contains the outputs of the measuring elements (current, voltage, frequency) included in the circuit of each phase of the primary and secondary windings, which are connected to the output of the element that sets the time for receiving data and calculation, with the inputs of the active resistance calculation blocks reducing the primary voltage to the secondary, calculating the voltage difference, calculating the voltage drop across the active resistances, bringing the inductance value to the nominal frequency, the outputs of which are connected to the corresponding inputs of the current derivative calculation blocks for the primary and secondary voltages, calculating the average voltage value, calculating the inductance, calculating the average values of the inductance for all voltages, all phases for a specified period of time, calculating the deviations of the active resistance and inductance for all voltages, all phases for a specified period of time, relative to the phases and nominal values, which are determined by the manufacturer of the equipment during appropriate tests, after which the data are transmitted to the inductance and active resistance control unit for primary and secondary voltages and all phases, from where information is transmitted to a unit that combines information from all control, monitoring and diagnostic devices, makes a decision on the received values (deviations) (about deviation for active and inductive resistances within 2.5% is normal; deviations within 5% indicate the initiation of destructive processes, but it does not require disconnecting it from the network and repair; deviations of 6-15% signal a danger, a signal is sent to the operator, it is necessary to take measures to bring the transformer into repair without disconnecting responsible consumers from the network; deviations of 25% - emergency shutdown of the transformer from the network; the deviation between the phases of the measured values of the active resistance and inductance for the normal state should not exceed 2%) for continued operation or disconnecting the transformer from the network, by supplying a signal to the trip unit and / or relay of the input circuit breaker or other protective device of the transformer, all information is also supplied on the monitor (display), with the help of which people are informed about the condition of the equipment.

The technical result provided by the given set of features is the instant determination of the resource and condition (diagnosis) of the windings of the power transformer, protection of the transformer, prevention of emergency failures of transformer equipment, as well as giving mobility to the desired device, increasing the reliability of operation of the transformer.

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

- figure 1 is a connection diagram of a mobile monitoring and diagnostic device (UDMM) to measuring instruments of a power transformer;

- figure 2 is a diagram of UDMM.

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

Disclosure and implementation of a utility model.

The first essential sign to achieve the above technical result is the calculation of the deviation of the active resistance for each phase on the high and low voltage side in blocks 22, 23, 24 with any time interval and taking into account non-linear components (harmonics).

The second essential feature is that the inductance deviation is calculated for each phase on the high and low voltage side in blocks 7, 8, 9, 10 with any time interval and taking into account nonlinear components (harmonics).

The third essential sign is that the deviations of the values of the active resistance and inductance are compared with the nominal values set by the manufacturer of the equipment and between the phases, which allows, having data on the magnitude of the deviation (the diagnostic system shown below), to carry out diagnostics, monitoring and protection power transformer.

This device UDMM refers to the mobile type, i.e. allows you to freely carry the device and apply to transformers of any design.

Figure 1 shows the General connection diagram of the device UDMM. It is most optimal, in terms of initial provision of auxiliary equipment, to use this device for complete transformer substations, but it can also be used for transformer substations with a separate high-voltage switchgear. A transformer substation, as a rule, consists of a power transformer powered by a three-phase power supply, a high voltage switchgear (LVRN), a low voltage switchgear (LVRN) supplying a load.

The switchgear cell supplying the transformer contains a high-voltage circuit breaker and, as a rule, a relay protection device that also measures the voltage on the high-voltage side. In addition, in case of stationary execution of the diagnostic and monitoring device, an independent release can be installed, which allows disconnecting the transformer from the mains. In some switches, this function is already integrated. If there is no possibility of measuring voltage, then a voltage transformer is connected to the mains. It can be installed either in a separate cell or in a free space in an existing cell.

RUNN consists of an introductory cabinet and a distribution cabinet that feeds the load. The RUNN scheme in this case is not fundamental. The opening cabinet includes a circuit breaker, current transformers, an ammeter and a voltmeter. As a rule, they are already contained in most opening cabinets, as serve to control. A frequency meter is also needed. In practice, it will need to be additionally installed. But there will be no interruption in power supply if the RUNN consists of several, for example, two, sections, because during installation, power will be supplied to another section.

Network parameters (voltage, frequency) do not matter, because monitoring and diagnostic device can be configured to any parameters.

Figure 2 displays a schematic diagram of UDMM. The device contains a number of blocks (table 1) that collect certain information and perform the necessary calculations. Signals come from all three phases, which allows you to determine the location of the defect.

First we list them, then we describe the principle of operation of the device.

Table 1.
The purpose of the blocks UDMM Block number Appointment one leads primary voltage to secondary voltage 2 calculates the voltage difference 3 calculates average stress values four calculates current derivatives for low voltage (LV) windings 5 calculates voltage drops at active resistances 6 low voltage winding resistance settings 7 calculates inductance 8 converts inductance values to rated frequency 9 calculates the average inductance over a period of time 10 calculates inductance deviations eleven LV winding inductance settings 12 control of deviation of inductance, active resistance

Block number Appointment 13 protection of a controlled power transformer fourteen collecting information from diagnostic systems, making decisions fifteen display (monitor) 16 network harmonic analysis 17 calculates current derivatives for high voltage (VH) windings eighteen calculates voltage drops at active resistances 19 time setting twenty VN winding resistance settings 21 HV winding inductance settings 22 calculates the active resistance of the HV winding 23 calculates the active resistance of the LV winding 24 calculates the deviation of the active resistance Tv HV voltage transformer Ti current transformer (1 - VN, 2 - VN) V voltmeter (1 - VN, 2 - VN) A ammeter (1 - VN, 2 - VN) Hz frequency meter

The principle of operation of a mobile device for monitoring and diagnosing a power transformer UDMM is as follows.

Constant or periodic monitoring of the status of the windings of the power transformer is ensured by determining the deviation of the inductance and active resistance in blocks 10 and 24 from the basic values that are determined at the factory of the equipment for a certain period of time, which can be set in the corresponding blocks, as well as the deviation the values of these values between phases.

During operation of the power transformer supplying the load, the primary voltage U ₁ and the secondary voltage U ₂ are measured, for example, using V ₁ and V ₂ . The signal from V ₁ enters the input of block 1. In block 1, the reduced to the secondary value of the primary voltage is calculated

where K _t is the transformation coefficient of the power transformer.

The input of block 2 receives signals from V ₂ and the signals from the output of block 1. In block 2, the calculation of the voltage difference is given to the secondary side. ΔU ^* is determined by the formula

where U ₂ is the value of the secondary voltage measured by V ₂ .

In block 3, the calculation is performed at a given time interval, which can be changed over a wide range in block 19

Where,

- ΔU ^* j are the values of the difference of the reduced voltages at the power transformer;

- t ₁ and t ₂ are the time boundaries of the partition interval.

In block 17 and 4, the current increment is calculated for a given time interval for the HV and LV voltage windings, respectively

where ij is the current value in the primary or secondary winding of the power transformer, measured by A ₁ and A ₂ .

In block 18 and 5, the voltage drop across the active resistance of the transformer for the HV and LV voltage windings, respectively, is calculated as the product

where R _m is the value of the active resistance of the transformer, which is calculated by the formula for the HV and LV voltage windings (the calculation occurs in blocks 22 and 23, respectively).

In block 7 is determined by the instantaneous value of the inductance at a given time interval for the windings HV and LV

In block 8, the instantaneous inductance value calculated to the rated frequency for the HV and LV voltage windings is calculated

Where,

- f _a is the frequency value measured by the frequency meter;

- f _r - the nominal value of the frequency (f _nom = 50 Hz).

In block 16, the voltage and current are analyzed for harmonics. Harmonic data is sent to, for example, a filter for fine-tuning it to match the real network performance.

In block 9, the average value of the inductance for each period for the HV and LV voltage windings is calculated

where N is the number of partition intervals.

In block 10, a comparison is made of the value of L _a for the period with the setting value of L _oj from block 21 and 11 for the HV and HV windings, respectively, and their difference is calculated

Where,

- L _a - the average value of the inductance for the period;

- L _r is the value of the inductance setting of the power transformer for the HV and LV voltage windings, determined experimentally at the equipment manufacturer.

In block 24, the value of R _a for the period is compared with the set value R _r from block 6 and 20 for the HV and LV windings, respectively, and their difference is calculated

Where,

- R _a - the average value of the active resistance for the measurement period (from block 22 and 23);

where R _r is the value of the setpoint resistance of the transformer. They are determined by the results of an experiment at the equipment manufacturer.

Deviation for active and inductive resistances within 2.5% is normal. Deviations within 5% indicate the emergence of destructive processes, but it does not require disconnecting it from the network and repair. Deviations of 6-15% signal a danger, a signal is sent to the operator. It is necessary to take measures to bring the transformer into repair without disconnecting the responsible consumers from the network. Deviations 25% - emergency disconnection of the transformer from the network.

In the event of initial deformations, as well as in the case of an internal winding circuit in the transformer windings, a developing increase or decrease in the ΔL, ΔR value from period to period occurs, which accompanies the irreversible destruction of the power transformer windings. At the same time, a signal is sent from block 12 to block 14, which analyzes the received data and makes decisions, such as the need for an emergency disconnection from the supply network, continuing measurements, signaling that destruction has begun, etc. At the same time, light or text information is displayed on display 15 , which indicates the operation mode and condition of the transformer windings. Block 14 also allows you to receive data from other diagnostic systems, analyze (with the appropriate settings) and make more accurate diagnostic decisions. In case of an emergency, a signal is sent from block 14 to the protection block 13, where a signal is generated to trip the circuit breaker, and sent to a relay or shunt trip. The display (monitor) (block 15) allows you to control the entire process of monitoring and diagnosis. When additional modules are connected to it, it is possible to transmit data at a distance to the central control room or to local operators. Block 16, which analyzes the quality of the network, namely the presence of harmonics, allows you to identify them and transmit this information to the harmonics filter, which will improve the quality of electricity and the life of the equipment.

Taking into account the value of the active resistance of the power transformer in block 5 and 18, and then when calculating the inductance in block 7, it allows to increase the accuracy of measuring the magnitude of the inductance of the transformer and to increase the reliability of the device as a whole.

During operation, the clock signals from block 12 synchronize the measurement of the values of di / dt and u _a with the corresponding sampling step.

In blocks 10 and 24, the inductance and the active resistance between the phases are also compared, which allows, in the absence of information on a number of parameters from equipment manufacturers, to evaluate the condition of the equipment. Differences between the values of these parameters should not be more than 2% for a normal state. Excess indicates a defect.

Block 19 allows you to set any time intervals, decreasing and increasing which you can control every minute, every other day, etc.

The advantages of the above device.

The above device will allow you to monitor the status of the windings of power transformers without disconnecting them (transformers) from the network, as well as to protect them in the event of deformation of the windings or their damage, it will allow sending information to dispatchers, i.e. carry out remote control. This increases the uninterrupted power supply of consumers of electric energy.

The list of sources for consideration during the examination 1. Bogdanov VI, Bogdanov VV, Stepanenko EB A method for diagnosing inductive windings. Patent for invention RU No. 2388004, class. G01R 31/06, 2009.

2. Schlegel O.A., Khrennikov A.Yu., Zhnjakin O.V. Device for testing transformer with short circuit currents. Auth. testimonial. USSR N 1821759, class G01R 31/02, 1993

3. Yaya Liu; Ning Wang; Jianzhou Zhao. Oil-immersed inverted current transformer with function of insulation online monitoring. CN Patent No. 101707127 (A), CL G01R 15/18; H01F 27/28; H01F 27/30; H01F 38/28, 2010.

Claims (1)

A device for monitoring, diagnostics, protection of transformers from winding deformation and damage (deterioration) of the insulation of the windings without disconnecting them (transformers) from the mains and load, characterized in that it contains the outputs of the measuring elements (current, voltage, frequency) included in each circuit phases of the primary and secondary windings, which are connected to the output of the element that sets the time for receiving data and calculation, with the inputs of the blocks for calculating the active resistance, bringing the primary voltage to the secondary, calculating the voltage difference, calculating the voltage drop across the active resistances, bringing the inductance value to the nominal frequency, the outputs of which are connected to the corresponding inputs of the current derivative calculation blocks for the primary and secondary voltages, calculating the average voltage value, calculating the inductance, calculating the average inductance values for all voltages, all phases for a specified period of time, calculating the deviations of the active resistance and inductance for all voltages, in all phases for a specified period of time, relative to the phases and nominal values, which are determined by the manufacturer of the equipment during appropriate tests, after which the data are transmitted to the inductance and active resistance control unit for primary and secondary voltages and all phases, from where information is transmitted to the unit uniting information from all control, monitoring and diagnostic devices, makes a decision on the received values (deviations) (deviation for active and inductive minutes within 2.5% is normal; deviations within 5% indicate the initiation of destructive processes, but it does not require disconnecting it from the network and repair; deviations of 6-15% signal a danger, a signal is sent to the operator, it is necessary to take measures to bring the transformer into repair without disconnecting responsible consumers from the network; deviations of 25% - emergency shutdown of the transformer from the network; the deviations between the phases of the measured values of the active resistance and inductance for the normal state should not exceed 2%) for continued operation or disconnecting the transformer from the network by supplying a signal to the trip unit and / or relay of the input circuit breaker or other protective device of the transformer, all information is also sent to monitor (display), with the help of which people are informed about the condition of the equipment.