RU4171U1 - DEVICE FOR MONITORING THE STATE OF INSULATION OF HIGH VOLTAGE N-PHASE ELECTRICAL EQUIPMENT - Google Patents

Abstract

1. A device for monitoring the state of insulation of high-voltage N-phase electrical equipment, containing N input terminals for connecting the measuring leads of the corresponding phases of the controlled object, an adder with N inputs and an information block, the input of which is connected to the output of the adder, characterized in that N circuits of temperature stabilization of the corresponding input currents of the adder, which are connected between the input terminals of the device and the corresponding inputs of the adder. 2. The device according to claim 1, characterized in that each of the N temperature stabilization circuits is made in the form of a parallel connected capacitor and a thermistor installed at the corresponding phase of the controlled object.

Description

DEVICE FOR MONITORING THE STATE OF INSULATION OF HIGH VOLTAGE N-PHASE ELECTRICAL EQUIPMENT

The utility model relates to electrical engineering, namely, to the field of diagnostics of high-voltage insulation by measuring its conductivity current.

State of the art

A device for monitoring the state of insulation of high-voltage equipment C, containing current regulators connected to the monitored object (for example, the measurement leads of the high voltage inputs), a current adder and a measuring unit. The disadvantage of this device is its low sensitivity.

A more sensitive device is known for automatic monitoring of the insulation state of high-voltage equipment 23, adopted as a prototype. It contains input terminals for connecting the test leads of the corresponding phases of the monitored object, a multi-input adder, a measuring (information) unit, as well as a voltage transformer, secondary

The field of technology of the winding of which is connected to the inputs of the adder, which allows you to compensate for errors caused by the asymmetry or non-sinusoidality of the voltage on the high voltage buses.

However, the prototype device also does not provide the required control accuracy, since there is another type of instability of the conductivity currents of the insulation. We are talking about temperature dependences of the dielectric loss tangent (active component of the insulation conductivity current) known from C1, which can be different for different objects, for example, due to the different moisture content of the insulation of high-voltage devices (inputs, current transformers, etc.).

So, according to 11, the loss tangent of oil-soaked cellulose at a temperature of approximately 10% with a cellulose moisture content of S, 5% and equal to 1% for a moisture content of 1%. At a temperature of 20 ° С, the tangents of the loss angles of one and the other insulation, although different, are very small, about 0.5%. The indicated moisture content of insulation is not a sign of defective devices. Therefore, it is quite possible that one of the high-voltage phase inputs will be moistened more than others.

In this case, adjusting the device at any particular temperature does not preclude its unbalance when the temperature changes. Calculations show that such an imbalance (i.e., the unbalance current of the device caused by a change in temperature with different insulation humidity) may well amount to several percent from full current controlled isolation. This circumstance forces us to artificially reduce the sensitivity of the device in order to avoid false alarms when the temperature changes. It does not allow

sensitivity of the order of 1% of the capacitive current, which, according to the SZ, is required for the timely detection of defects, in particular, in high-voltage bushings.

The objective of this proposal is to create a highly sensitive device that is free from false positives when monitoring the insulation state of high-voltage multiphase devices with phase-dependent temperature dependences of the active components of the insulation conductivity current.

Utility Model Disclosure

The subject of a utility model is a device for monitoring the insulation state of high-voltage N-phase electrical equipment, containing N input terminals for connecting the measurement leads of the corresponding phases of the controlled object, an adder with N inputs and an information block whose input is connected to the output of the adder, characterized in that N temperature circuits are introduced stabilization of the corresponding input currents of the adder, which are connected between the input terminals of the device and the corresponding inputs of the adder.

This allows you to compensate for the temperature dependence of the dielectric loss tangent of the insulation on the imbalance of the control device and thereby increase its sensitivity.

A utility model has been developed regarding the most preferred implementation of temperature stabilization circuits and that each of the N temperature stabilization circuits is made in the form of a parallel-connected capacitor and

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a thermistor installed on the corresponding phase of the controlled object.

The essence of the utility model is illustrated by the drawing of figure 1, which shows a block diagram of a device for N-3 with the most preferred implementation of the temperature stabilization circuits.

Description of Utility Model Implementation

The device of Fig. 1 contains input terminals 1, an adder S with input terminals 3, an information block 4, the input of which is connected to the output of the adder 2, and a temperature stabilization circuit 5 of the input currents of the adder 2, connected between the terminals 1 and conclusions 3. Each of the circuits 5 contains a capacitor 6 and a thermistor 7.

Terminals 1 are intended for connection to the measuring phase terminals 8 of the controlled object 9.

The device of FIG. A works as follows.

At terminal 1 from pins 8, a controlled conductivity current of the phase insulation of the object 9 is energized. This current has an active and capacitive components, while the active component depends on the temperature of the object 9.

At low temperatures (10-SO ° C), the active components are negligible and the device is balanced by the appropriate choice of capacitors 6. Maintaining the device balance at a high temperature of the object 9, which does not have an insulation defect, is achieved by the corresponding choice of resistance of thermistors 7 at a relatively high temperature facility 9, close to the limit in operation. As a result, when the insulation of the object 9 is intact, the device is balanced, i.e. lack of current at the output of the adder 2, in the entire range of operating temperatures.

If there is an insulation defect in any phase of the object 9, a current appears at the output of the adder 2, which is recorded by the unit 4.

The main positive - an increase in the sensitivity of the control device compared to the prototype can be achieved with a different internal structure of circuit 5 than in FIG. 1, for example, when a capacitor and a thermistor are connected in series.

Industrial applicability

In accordance with the proposal according to the scheme of figure 1 was assembled a mock control device.

The phase of the controlled object 9 was modeled by a 0.1 μF capacitor shunted by a resistor whose resistance was regulated from 50 kΩ to 1 MΩ. Temperature stabilization circuit 5 consisted of a capacitor with an adjustable capacitance and a KMT-1 thermistor.

The setup of the circuit was carried out at temperatures of 20 ° C and 90 ° C, after which the unbalance current was measured at temperatures of 40 ° C, 60 ° C and 80 ° C. At each temperature, the phase model resistances of the controlled object were set in accordance with curves 13 at different humidity values insulation, and thermistors of 7 phases were heated to their corresponding temperature.

Measurements showed that the unbalance currents of the device at different temperatures do not exceed 0.2% of the capacitive current of the phase of the controlled object.

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- 6 Formula Information Sources

1.Swi P.M. Insulation control of high voltage equipment. Moscow, Energoatomizdat, 1988, pL14.

2.Auto St. USSR N 2003127, SC G01R 31/02, publ. 1993

3. Electric stations, N 11, 1989, pp. 83-92.

Claims (2)

1. A device for monitoring the state of insulation of high-voltage N-phase electrical equipment, containing N input terminals for connecting the measurement leads of the corresponding phases of the controlled object, an adder with N inputs and an information block, the input of which is connected to the output of the adder, characterized in that N temperature stabilization circuits of the corresponding the input currents of the adder, which are connected between the input terminals of the device and the corresponding inputs of the adder.  2. The device according to claim 1, characterized in that each of the N temperature stabilization circuits is made in the form of a parallel-connected capacitor and a thermistor installed on the corresponding phase of the controlled object.