RU2306573C1 - Device for evaluating non-linear overvoltage limiter reliability - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: device has electric voltage source, one nonlinear resistor, electric voltage source, resistor, meter-voltage circuit, additional nonlinear resistor having hole in its central part, making electric contact with its upper end face surface to bottom face surface, at least one nonlinear resistor of nonlinear overvoltage limiter under test. Additional nonlinear resistor has its height considerably less than height of at least one nonlinear resistor of the nonlinear overvoltage limiter under test, and has capacitance much greater, than resistor resistance under nominal voltage of electric voltage source. Its dynamic resistance is much less than resistor resistance under occurred overvoltage above operation threshold of the nonlinear overvoltage limiter under test and additional nonlinear resistor.

EFFECT: simplified design.

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Description

The proposed technical solution relates to the field of measurement technology and can be used to assess the reliability of a non-linear overvoltage limiter, constantly under operating voltage, with a simple structural implementation.

A similar technical solution is known (see, for example, Energy and Industry of Russia, newspaper No. 2 (54) February 2005. Fig. 1c), which describes a similar technical solution and which contains:

- source of electrical voltage;

- non-linear surge suppressor, connected by its first output to a source of electrical voltage;

- a metal ring connected to the lower end surface of the lower non-linear non-linear surge suppressor resistor;

- a switch connected by its first terminal to the metal ring and its second terminal to the second (Ground) terminal of the voltage source;

- a measurement circuit connected by its inputs parallel to the switch.

Common features of the proposed technical solution and the above-described analogue are:

- source of electrical voltage;

- non-linear surge suppressor, connected by its first output to the first output of the voltage source;

- measurement scheme.

A similar technical solution is also known (see publication of the Spectrum-Energo Scientific and Technical Center, Moscow, Non-linear surge arresters in polymer cases for 1-35 kV AC networks, which is selected as a prototype and which contains:

- source of electrical voltage;

- non-linear surge suppressor, containing at least one non-linear resistor (varistor) connected with its first output to the first output of the voltage source;

- a switch connected by one of its terminals to the second terminal of the non-linear surge suppressor and by its other terminal to the second (ground) terminal of the voltage source;

- a resistor connected by its first terminal to the second terminal of the non-linear surge suppressor and by its second terminal to the second (ground) terminal of the voltage source;

- arrester connected in parallel with the resistor;

- a measurement circuit connected by its first input to the first terminal of the resistor and its second input to the second (ground) terminal of the voltage source.

Common features of the proposed technical solution and prototype are:

- source of electrical voltage;

- non-linear surge suppressor, containing at least one non-linear resistor (varistor) connected with its first output to the first output of the voltage source, resistor connected with its first output to the second output of the non-linear surge suppressor and its second output to the second ground terminal of the electric source voltage;

- a measurement circuit connected by its first input to the first terminal of the resistor and its second input to the second ground terminal of the voltage source.

The technical result that cannot be achieved by any of the similar technical solutions, while providing an assessment of the reliability of the non-linear surge suppressor, which is constantly under operating voltage and constantly provides protection against arising overvoltages, consists in eliminating complex technical and constructive implementation of devices for assessing the reliability of a non-linear surge suppressor, associated with the use of powerful high-voltage switches and arresters.

The reason for the impossible achievement of the technical result indicated above is that the prevailing practice when evaluating the reliability of non-linear surge suppressors involves measuring the conductivity current of a non-linear surge suppressor only after disconnecting the non-linear surge suppressors from the ground wire and, for example, connecting to the free terminal of the surge suppressor non-linear measurement scheme, which in turn is associated with both significant technical and uktivnymi difficulties, and unsafe working conditions during the measurements to assess the reliability of nonlinear surge arresters.

Given the characterization and analysis of known similar technical solutions, we can conclude that the task of creating tools for assessing the reliability of non-linear surge arresters, which are constantly under operating voltage, have a less complicated technical and constructive implementation, as well as safe measurement conditions, is relevant today.

The technical result indicated above is achieved by the fact that the device for evaluating the reliability of a non-linear overvoltage limiter, which is constantly under operating voltage, contains an electric voltage source, a non-linear overvoltage limiter, which includes at least one non-linear resistor (varistor) connected by its the first terminal to the first potential terminal of the voltage source, a resistor connected by its first terminal to the second terminal of the surge suppressor an additional and non-linear resistor (varistor) with an opening made in it, linear and with its second output to the second ground terminal of the voltage source and the measurement circuit connected by its first input to the first terminal of the resistor and its second input to the second ground terminal of the voltage source the central part, which is electrically contacted by its upper end surface on the lower end surface of at least one non-linear resistor (varistor) is limited Overvoltage of Tell nonlinear and its lower end connected to the second surface of the ground terminal, a voltage source, a first terminal of the resistor is electrically insulated from the inner surface of the hole and the lower end surface of the additional non-linear resistor (varistor).

The introduction of an additional nonlinear resistor (varistor) with a hole made in its central part, its location and connection, as indicated above, allows, due to the applied voltage from the terminals of the voltage source to the terminals of the non-linear overvoltage limiter, containing at least one non-linear resistor ( varistor), obtain from its output a conductivity current which, when passing through the resistor, creates a voltage drop in this resistor proportional to the conductivity current of the limiter ne non-linear overvoltage and clearly characterizes the reliability of the non-linear overvoltage limiter, therefore, by measuring this voltage drop across the resistor, it can always be used to determine the reliability of the non-linear overvoltage limiter that is constantly under the operating voltage without affecting the performance and protective properties of the non-linear overvoltage limiter. In this, the achievement of the technical result indicated above is manifested.

The analysis of the known technical solutions showed that not one of them contains both the totality of features and the distinctive features of the proposed technical solution, which allowed us to conclude that there is a "novelty" and "inventive step" of the proposed technical solution.

The proposed device for evaluating the reliability of the non-linear surge suppressor, which is under operating voltage, contains:

- source of electrical voltage - 1, for example, a high voltage power line;

- non-linear surge suppressor, made, for example, in the form of at least one main non-linear resistor (varistor) - 2 and connected with its first output to the first output of the voltage source - 1;

- an additional non-linear resistor (varistor) - 3 with an opening - 4 made in its central part, electrically contacted with its upper end surface on the lower end surface of at least one main non-linear resistor - 2 non-linear surge arresters and connected with its lower end surface to the second output of the voltage source - 1;

- resistor - 5, the first terminal of which is electrically insulated relative to the inner surface of the hole - 4 and the lower end surface of the additional nonlinear resistor (varistor) - 3 and connected with its first output to the lower end surface of at least one main nonlinear resistor (varistor) - 2 limiters non-linear overvoltage and its second output to the second output of the voltage source - 1;

- measurement circuit - 6, connected by its first input to the first output of the resistor - 5 and its second input to the second output of the voltage source - 1.

The proposed device for evaluating the reliability of a non-linear surge suppressor under operating voltage operates as follows.

When the rated voltage of the source of electric voltage is 1, a conductivity current of magnitude (fractions of a milliampere) flows through a non-linear overvoltage limiter, which is calculated by the formula:

, где

- модуль тока проводимости, U_p - рабочее напряжение и

- модуль комплексного сопротивления, как минимум, одного основного нелинейного резистора - 2. При этом ток проводимости при номинальном напряжении источника электрического напряжения - 1 имеет в основном емкостной характер. В общем случае ток проводимости:

, где

- емкостной ток и

- активный ток.

where

is the conductivity current module, U _p is the operating voltage and

- the complex resistance module of at least one main non-linear resistor - 2. In this case, the conduction current at the rated voltage of the source of electric voltage - 1 is mainly capacitive in nature. In general, conductivity current:

where

- capacitive current and

- active current.

,

,

говорят о том, что сложение векторное.Points over

,

,

say that addition is vector.

где

- модуль тока проводимости. То есть модуль тока проводимости практически совпадает с емкостным током I_с.In a normally operating non-linear surge suppressor, active current: I _R ≤0.31 _{s of} capacitive current. Hence:

Where

- conductivity current module. That is, the conductivity current module practically coincides with the capacitive current I _s .

An additional non-linear resistor (varistor) - 3 with a central hole - 4 has a height much smaller than the height of at least one main non-linear resistor (varistor) - 2 and, accordingly, has a much lower capacitive resistance, so the conductivity current of the non-linear overvoltage limiter will be determined by the capacitance of at least one main non-linear resistor (varistor) - 2.

The conductivity current flowing through the resistor - 5 (the value of which is much less than the capacitance of the additional nonlinear resistor (varistor) - 3) creates a voltage drop across the resistor - 5, proportional to this conductivity current, which is fed to the inputs of the measurement circuit - 6 and is fixed as a specific value corresponding to the level of reliability assessment of a non-linear surge suppressor under operating voltage.

When overvoltages occur above the threshold of operation of nonlinear resistors (varistors) - 2 and 3 of the nonlinear overvoltage limiter, their dynamic resistance decreases sharply. In this case, the dynamic resistance of the additional non-linear resistor (varistor) - 3 becomes many times smaller than the resistor - 5 and the current during overvoltage passes through the circuit: output - 1 non-linear overvoltage limiter, its main non-linear resistor (varistor) - 2, the introduced non-linear resistor (varistor) ) - 3, grounding terminal - 2 sources of electrical voltage. So there is a restriction of arising overvoltages.

But due to the frequent effects of overvoltages, the current-voltage characteristic of non-linear resistors (varistors) - 2, 3 changes, which leads to an increase in the active conductivity current and when the active component of the conductivity current reaches a value 2-3 times higher than the value of the capacitive component of the current, a pre-emergency situation occurs . Since an increase in the active conduction current leads to an increase in the power loss of the non-linear overvoltage limiter and, accordingly, to an increase in temperature. And since the temperature coefficient of the current of nonlinear resistors (varistors) is positive, an increase in temperature causes an increase in the active conduction current, which subsequently leads to thermal breakdown of the nonlinear overvoltage limiter.

Moreover, if the value of the conductivity current of the non-linear overvoltage limiter under the operating voltage reaches the maximum permissible value, which also corresponds to the maximum permissible value of the voltage drop across the resistor - 5, then in order to avoid further emergency situations, timely replacement of this unreliable overvoltage limiter should be carried out nonlinear to another having the required level of reliability.

Thus, the proposed device for evaluating the reliability of a non-linear overvoltage limiter under operating voltage allows, without violating its protective properties against the occurrence of various overvoltages, to measure the voltage drop at any time, which is proportional to the conductivity current of the non-linear overvoltage limiter under operating voltage , and corresponds to the reliability level of the non-linear surge suppressor, which is under operating voltage.

Claims (1)

A device for evaluating the reliability of a non-linear surge suppressor, comprising a voltage source connected to a non-linear surge arrester under test, which includes at least one non-linear resistor connected by its first terminal to a first potential terminal of an electric voltage source, a resistor connected by its first terminal to a second terminal the tested non-linear surge suppressor and its second output to the second ground terminal source and an electrical voltage, a measurement circuit connected to its first input to the first output of the resistor and its second input to the second grounding terminal of the voltage source, characterized in that an additional non-linear resistor is inserted into it with a hole made in its central part, electrically mounted at its top end surface on the bottom end surface of at least one non-linear resistor of the tested non-linear surge suppressor and connected the lower end surface to the second ground terminal of the voltage source, and the first resistor terminal is insulated from the inner surface of the hole and the lower end surface of the additional non-linear resistor, while the additional non-linear resistor is made with a height much less than the height of at least one non-linear resistor of the tested non-linear voltage limiter , and has a capacitance much greater than the resistance of a resistor at rated voltage source of electrical voltage, and the dynamic resistance is much smaller than the resistance of the resistor when an overvoltage occurs above the threshold of the test overvoltage limiter of a nonlinear and additional nonlinear resistor.