RU2099725C1 - Measurement of loss angle tangent of high-voltage equipment and device for its implementation - Google Patents

Abstract

FIELD: electrical engineering, aids measuring high voltages. SUBSTANCE: technical problem solved by invention consists in possibility of conducting measurements on operating equipment, in increased accuracy of measurements and diminished dimensions of proposed device. Measurement is carried out by comparison of information and reference signals. Information signal is received from output terminal of tested high-voltage equipment and reference signal is obtained by measurement of intensity of field accompanying voltage feeding tested high-voltage equipment. Device for implementation of measurement has information signal converter, reference signal converter which outputs are connected to inputs of comparator which output is linked to indicator. Reference signal converter is manufactured in the form of meter of intensity of electric field. Comparator is made in the form of phase meter. EFFECT: increased accuracy of measurements and diminished dimensions of device. 3 cl, 2 dwg

Description

 The invention relates to high voltage technology and electrical measuring equipment serving high-voltage installations.

 A known method that allows to measure the loss tangent of the insulation loss of high-voltage installations [1] by comparing the phase of the information signal specified by the monitored installation with the phase of the reference signal, followed by obtaining the phase difference of the two signals, which is used to judge the value of the loss tangent. There are a number of devices that implement this method. For example, a device [2] used to determine the loss tangent of capacitors, containing a generator, the output terminal of which is connected via an active load to a terminal for connecting a capacitor, a switch, an analog-to-digital converter, a computer, a reference unit, a comparator, and an encoder that synchronize the operation of devices .

 However, using this device, it is impossible to take measurements on an object connected to a high voltage. In this case, a Shering’s measuring high-voltage bridge is used [1, 3] containing an information signal converter, a reference signal converter, the outputs of which are connected to the inputs of the comparison device, the output of the comparison device is connected to a indicating device, the reference signal converter is galvanically connected to a high voltage supplying the electrical equipment under study , and as a comparison device use a zero-organ (galvanometer). The trimming elements of this bridge achieve its equilibrium when comparing two signals of information (specified by equipment with the studied insulation) and reference. By the value of the parameters of the tuning elements in the equilibrium position of the bridge, the tangent of the loss angle is judged.

 It is necessary to dwell on the means of obtaining a reference signal. Usually, a voltage divider (for example, capacitive type) is used here, which relates to high-voltage equipment, since it must be connected directly to a high voltage, to which the studied high-voltage equipment is also connected. When receiving a reference signal, the divider implements the following conversion chain: specified high voltage current voltage at the output element of the circuit. Such converters are a source of a reference signal error. The described system for measuring the tangent of the loss angle includes high-voltage equipment, is cumbersome, expensive, subject to a number of interfering factors (for example, a strong electric field), which cause additional measurement errors. It should be noted that with this cumbersomeness, it is difficult to measure the loss tangent of the equipment in operation.

 The technical problem solved by the invention consists in the possibility of measuring on electrical equipment during its operation, increasing the accuracy of measurement and reducing the size and weight of the device that takes measurements.

 For this, in the known method for measuring the loss tangent of electrical equipment, in which the phase of the information signal specified by this equipment is compared with the phase of the reference signal, the value of the loss tangent is judged by the phase difference of the two signals, according to the invention, the signal obtained is used as a reference by measuring the intensity of the electric field accompanying the voltage supplying the electrical equipment under study.

 The problem is solved in a device that serves to implement the proposed method, comprising an information signal converter and a reference signal converter, the outputs of which are connected to the inputs of the comparison device, and its output is connected to a indicating device, in which, according to the invention, the reference signal converter is made in the form of a meter electric field intensity, to the input of which a field intensity sensor is connected, and the comparison device is made in the form of a phase meter. In addition, the device tension sensor is located on a grounded surface, and the indicating device is graduated with a tangent function.

 The invention is illustrated in the drawing. Figure 1 shows the topography of the power electric field of a wire located above a conductive surface, and also presents conventionally high-voltage equipment connected to this wire. In FIG. 2 is a structural diagram of a device that implements a scheme for measuring the loss tangent.

 To measure the loss tangent (tanδ), two signals are required, one of which is informational, proportional to the total current through insulation (this current has two components: reactive and active); the second reference, having the phase of the supply high voltage. To calculate the loss angle δ, the phases of these signals, or rather the phase shift of one signal relative to another, are needed. In this case, the magnitudes (amplitudes) of the signals are not significant.

 The information signal is taken directly from the investigated high-voltage equipment 1 (Fig. 1). For example, the high-voltage input has a special measuring electrode, with which the insulation current flows to the ground.

(x, y, z) известна

где k₁ константа,

элемент интегрирования.It is convenient to obtain information about the phase of the supply voltage without converting it to current. It is known that when a charged conductor 2 (for example, a wire connected to a voltage) is located in space, an electric field 3 takes place near it (Fig. 1). The relationship between the potential of wire 2 and the function of the tension vector

(x, y, z) is known

where k _{1 is a} constant,

integration element.

причем величина напряженности пропорциональна напряжению провода.On the conductive surface 4 (Fig. 2) there is only a normal component

moreover, the magnitude of the tension is proportional to the voltage of the wire.

где k₂ коэффициент пропорциональности, а

комплексные представления напряженности и напряжения.

where k _{2 is the} coefficient of proportionality, and

complex representations of tension and tension.

 Thus, the tension vector, measured for example at a grounded conductive surface 4, has information about the phase of the voltage. Therefore, it is convenient to take the electric field strength as a reference signal for measuring tanδ. To obtain it, a field strength meter is used, for example, according to the type of [4] This eliminates the cumbersome scheme of converting high voltage into a reference signal inherent in the prototype (high voltage current output voltage). The electric field together with the charge of the wire is a single whole, therefore, in the proposed measurement method, there is no conversion of high voltage to a signal at all, but there is a direct measurement of this field (intensity E).

 A device for implementing the proposed method for measuring the loss tangent comprises a tension sensor 5 (FIG. 2) located on a grounded surface 4 and connected to an electric field strength meter 6. Terminal 7 of the high-voltage equipment is connected to the input of the primary measuring transducer (PIP) 8. The meter outputs tension 6 and PIP 8 are connected to the inputs of the phase meter 9, the output of which is connected to the indicating device 10. The primary measuring transducer can be made in the form of an electric Nogo amplifier, and the indicating device in the form of micro-ammeter or voltmeter. The device operates as follows. An information signal 7 having a harmonic shape is processed in the primary measuring transducer 8. At the same time, a harmonic reference signal is supplied to the voltage meter 6 from the voltage sensor 5 located in the field 3 on the grounded surface 4. Both the converter 8 and the voltage meter 6 change the voltage parameters encoding the information and reference signals, to values that can be perceived by the phase meter 9. Phase 9 compares the phases of the information and reference signals, forming their difference, to Thoraya is "loss angle". The comparison result is sent to the indicating device 10, which is pre-graduated by the angle tangent function. Thus, the value of the tangent of the loss angle in the insulation of high-voltage equipment is read from the output of the indicating device 10.

 So, using the described device that implements the actions that make up the essence of the method, the tasks are solved, namely: the measurement accuracy is improved by eliminating intermediate transformations of high voltage into a reference signal; the dimensions and weight of the device are significantly reduced due to the exclusion of high voltage from the measuring system; conditions have been created for taking measurements on electrical equipment without decommissioning it. In addition, due to the exclusion of high voltage contact, personnel work is ensured, as a loss tangent measuring device is typically an electronic device with a voltage level of several volts.

Sources of information
1. Lokshin M.V. Sweet P.M. Measurement of dielectric loss of high voltage insulation. M. Energy, 1973, 144 p.

 2. A.S. N 1693566, G 01 R 27/26. publ. 1991.

 3. Installation for measuring losses and capacitance with an AC bridge (type P 525) (technical description and instructions for use). Kiev: Factory "Tochelectropribor", p. 2-4, 1959.

 4. A.S. N 930162, G 01 R 29/12, publ. 1982.

Claims (3)

 1. The method of measuring the loss tangent of high-voltage equipment, in which the phase of the information signal specified by this equipment is compared with the phase of the reference signal, the phase difference of the two signals is obtained, which is used to judge the value of the loss tangent, characterized in that the signal is used as the reference obtained by measuring the intensity of the electric field accompanying the voltage supplying the investigated high-voltage equipment.  2. A device for implementing a method for measuring the loss tangent of high-voltage equipment, comprising an information signal converter, a reference signal converter, the outputs of which are connected to the inputs of the comparison device, and its output is connected to a indicating device, characterized in that the reference signal converter is made in the form of a voltage meter electric field, the input of which is connected to a field strength sensor, and the comparison device is made in the form of a phase meter.  3. The device according to claim 2, characterized in that the tension sensor is located on a grounded surface, and the indicating device is calibrated with a tangent function.

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