SU1480003A1 - Method of protection against current leaks in mine contact networks - Google Patents

Abstract

The invention relates to electrical engineering and is intended to provide a safe operating environment for contact networks of ore and coal mines. The purpose of the invention is to increase the reliability and reliability of monitoring current leakage. In multiplying circuits 3 and 4, the alternating component of the network current is multiplied by the orthogonal reference variables, the network voltage components, and the R C filters 5 and 6 convert the signals obtained after multiplying into proportional DC signals. Comparator 7 compares the output signals from the filters 5 and 6, the ratio of which reveals the phase sign of the variable component of the current in the contact network or its increment. In case of exceeding a predetermined level, the measured ratio generates a signal to turn off the power. When the measured value exceeds a predetermined level, a special compensating signal is not required, since the DC signals are automatically attenuated in the active-capacitive measuring circuit and each new increment of the variable component of the current will be perceived without taking into account the previously achieved level, for example, due to technological loads electric locomotives. 1 il.

Description

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The invention relates to electrical engineering, in particular, to the protection of contact networks against current leakage, and can be used in the development of systems that ensure the safe operating conditions of contact networks of ore and coal mines.

The purpose of the invention is to increase the reliability and reliability of monitoring current leakage.

The drawing shows a functional diagram implementing the proposed method.

The circuit consists of a current sensor 1, a block of 2 reference voltages, multiplying circuits 3 and 4, LS filters 5 and 6, and a comparator 7.

The method is implemented as follows.

The voltage due to the variable component of the current in the contact network UCT sin (wt + H), where UCT, u ;, M is, respectively, amplitum, the angular frequency and the initial phase of the signal proportional to the conductivity of the contact network, multiplied by multiplying circuits 3 and 4 orthogonal reference voltages Uomsinwt and Uomcoso / t, where Uom is the amplitude of the reference voltage. These voltages are supplied from a reference voltage block, which either converts a variable component of a voltage in a contact network, or it can itself be the source of this variable component and inject it into a contact network. At the output of the multiplying schemes, we have the signals K, if-cos (+ 4) 3 and K1U0Uc sin if-, respectively.

-sin (2u) t +) J, where U 0 and Uc are respectively the effective values of the reference voltage and a signal proportional to the conductivity of the catenary network. The coefficient K, is the double value of the proportionality coefficient of the multiplying circuit 3, in the course of adjustment is set to 0.1-0.2. Coefficient K is the doubled value of the proportionality coefficient of the multiplying circuit.

4 and in the process of adjusting the latter is set to K ,. These signals are fed to the input of RC filters, where they are converted into signals KjUccos tf (e) and K4Ucsi.n m (ee), where Ke, K are the transfer coefficients of the RC filters.

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The absolute values of the coefficients K3 and K4 are of no fundamental importance. Their K4 / KE ratio is decisive. These signals are compared by a comparator, which produces a tripping signal only under the condition K3cosw K 4. sin if. By setting the corresponding values of the coefficients Kj and K +, set the preset level of phase shift between the variable components of the current and: voltage in the contact network.

The output signals of the RC filters naturally decay in time, which follows from their analytic description. Thus, the steady-state value of the variable component of the current in the contact network, caused, for example, by technological loads, has no effect on the control of the increments of the variable component, which is achieved in the known method in a more complicated and less reliable way.

The technological advantages of the invention in comparison with the prototype are as follows: a simpler method of setting a predetermined phase shift level ensuring natural attenuation of signals proportional to the variable component of the current in the contact network, which eliminates the need to use complex and insufficiently reliable nodes producing a compensating signal.

Claims (1)

Invention Formula A method of protecting against leakage of current to earth in mine contact networks, including the separation of variable components of current and voltage in a protected network, measurement of a signal proportional to the phase shift between the components of current and voltage, comparison of the measured signal with a given level and forming a tripping signal when a specified signal level exceeds a predetermined signal level, characterized in that, in order to increase the reliability and reliability of current leakage monitoring, after the selection of the variable components, the components are multiplied s signal proportional to the variable component of the current network being protected, on two orthogonal signal pro314800034 the proportional variable is the constitutional signals of the direct current, and in the quality of the voltage of the protected network, the signal proportional to the phase formation of the polbins after the shift is taken as the ratio of signal multiplications in proportional dc signals.