SU691787A1 - Apparatus for measuring wear of power transformers - Google Patents

Description

(54) DEVICE FOR MEASURING THE WEAR OF POWER TRANSFORMERS

The invention relates to the field of automation of technological processes in the power industry and is intended for use in determining the wear of power transformers and autotransformers. In addition, the device can be used to fix the wear of other electrically-powered machines and components, for example, generators, motors, special high-voltage cables. The wear and tear of the SIO transformers is practically not measured because of the difficulties associated with obtaining information about the temperature of the hottest point of the winding and the implementation of the device for automatic processing and displaying wear data about the insulation of transformers in accordance with the accepted law of aging. . A device for measuring the wear of power transformers is known, comprising a temperature to voltage transducer located in the upper layers of the oil and a load current to voltage transducer included in the load circuit of the transformer 11. However, the known device is rather cumbersome, expensive and difficult to manufacture. The purpose of the invention is to simplify the device. For this purpose, a device for measuring the wear of power transformers, containing a temperature to voltage converter and a load current to voltage converter, is used to introduce a control unit and a series-connected adder, n parallel threshold elements, a pulse generator and a counter, and the outputs of temperature converters The generator is connected to an adder, and the control unit is connected to a pulse generator. The drawing shows the block diagram of the device for. wear measurement of power transformers. The device contains a functional load current converter 1 connected to a measuring current transformer 2, which is installed in phase, a power transformer, a torus 3, a sensor 4 for the temperature of the upper oil layers, a temperature converter 5 for voltage, cyvwaTop 6,

threshold elements 7, /. . ., 7 ", pulse generator 8, electromechanical pulse counter 9 and control unit 10.

The current values of the current converter 1, proportional to the load current of the power transformer 3, from the current transformer 2 are fed to a functional converter 1, made, for example, according to the quad diode circuit, which converts the current I to the signal H (1) according to the overheating of the transformer winding above the oil temperature from the load current.

The current values of the cooling oil temperature T from the temperature sensor 4, immersed — the upper layers of oil in the tank of the power transformer, go to the linear converter 5, which converts the current temperature 8 to a signal, in accordance with the accepted law of insulation aging. With the help of adder b, the signals if. (D) and H are summed. At the output of the adder, several threshold elements 7, 7, ... 7 are set, which determine the operating mode of the generator 8, the output of which includes an electromechanical pulse counter 9.

In order to prevent the counter from overflowing over a long integration period, especially for large values of b, the pulse generator is powered through the contacts of the unit 10, which turns on the device for a predetermined recording time of transformer wear, for example, for 1 min for 0.5 h.

As a law to isolate transformer windings, the Montzinger equation can be used.

and 1 "e-ssv -.,. e-c1 (

o - where L is the longevity

isolation; L is the service life (life) of the insulation, corresponding to a constant temperature, and, as standardized, is the standard service life of the transformer;

 - coefficient taking into account the change in the service life of the insulation with a change in temperature at the most heated point of the insulation;

& —the temperature of the hottest point of insulation above the oil temperature — the oil temperature. The temperature rise of the winding E taking into account the possibility of neglect

its constant heating time can be written as

where z is the coefficient taking into account the temperature difference between the middle and the most heated points of the windings; T is the established average overheating of the winding over the oil temperature in the nominal mode; K - the multiplicity of the load current

transformer;

n is the coefficient depending on the transformer cooling system.

In accordance with equation (1), the instantaneous aging of the isolation of transformers is determined by the exponential function with a degree equal to the sum (+ e / w).

Then, the total value of transformer wear (insulation aging) over a period of time is determined as

and.,.

where m is the scale factor.

Based on equation (2), the signal f (l) at the output of the functional converter 1 when changing the ratio of the load current K should change in accordance with a power function of the form k, and the signal V (at) at the output of converter 5 when the temperature of the cooling oil changes, expression (3) should be linear.

It follows from expression (3) that the signals from transducers 1 and 5 must be fed to adder 6, after which the soli signal must be converted into an exponential function and integrated.

In the proposed device, depending on the output signal of the adder .6, proportional to the sum + vd, one of the threshold elements 7-7 is triggered, which by its output contacts prepares the pulse generator circuits 8. The latter generates pulses with a frequency proportional to the value of g ".c -) JJ characterizing the dependence of insulation aging on temperature. .

This device compares favorably with the known analogs of increased accuracy, extended measurement range, manufacturability, due to the use of elements of discrete and analog equipment, especially in the implementation of the integrating node with high resolution for long

the integration period, measured in hundreds, thousand hours.

The device will make it possible to significantly increase the efficiency of using the installed capacity of the transformer fleet of the country, to extend the service life of transefo umators at substations, which will give a significant economic effect.

Claims (1)

Invention Formula A device for measuring the wear of power transformers, comprising a temperature to voltage transducer located in the upper oil, and a load current to voltage transducer included in transformer load circuit, which, in order to simplify the device, introduces a control unit and a series-connected adder, n parallel-connected threshold elements, a pulse generator and a counter, with the outputs of temperature converters in voltage and load current in voltage connected to the adder, and the control unit is connected 0 with pulse generator. Sources of information (matsie taken into account during the examination 1. Proceedings of the Moscow Institute of Railway Transport Engineers, 1971, vol. 388, p. 42-47 (prototype).