RU2260812C2 - Device for determining the place of one-phase ground in the networks with insulated neutral - Google Patents

Abstract

FIELD: engineering of electric power supply of railroads.

SUBSTANCE: proposed device is related to ensuring the normal functioning of the railroad high-voltage lines of longitudinal electric power supply with insulated neutral. A current transducers is switched into one from undamaged phases, closed with the damaged phase on the near end of line. The switch is located on the far end of line and has possibility closing and breaking of the undamaged and damaged phases with the current transducer. The measuring part is carried out with successively switched arithmetical device, functional corrector and indicator. The device has also a stabilized constant-current source, intended for supplying two measuring circuits by the current of equal value. The constant-current source is switched between the ground and phases, closed on the near end of line. This measuring part has also a control device and voltmeter with parallel connection to the stabilized constant-current source. The control device ensures possibility to control the voltmeter operation for realization of the peaking-difference function of this voltmeter in the modes with broken and closed switch. Besides the control device has possibility to control the arithmetical device, obtaining the information from the voltmeter on fulfillment the subtraction function of voltage, obtained in the second mode, from the first mode voltage, loaded preliminary into memory. The arithmetic device has possibility to realize the division of obtained voltage difference by the current, measured with current transducer, and to transmit the division result into the functional corrector. The last has possibility to take into account the line parameters and to convert the division result into a signal, convenient for readout on the indicator of information about the distance from substation up to the place of phase ground.

EFFECT: high functional possibilities; in particular, possibility to determine the places of phase ground in the low power lines at small tested currents and at large contact resistance in a place of ground.

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Description

The invention relates to equipment that ensures the normal functioning of high-voltage lines of longitudinal power supply of railways with isolated neutral. On railways, the power supply of the signaling system of the signaling system is provided by high-voltage lines of the overhead line of the signaling system of 6-10 kV. Due to the special importance of uninterruptible power supply, the alarm systems of the line are designed according to the scheme with isolated neutral. Therefore, the phase to earth fault does not lead to the disconnection of the entire line, and there is a time gap for troubleshooting. The prolonged state of the overhead line signaling with a grounded phase is unacceptable. The occurrence of the second of the same circuit on another phase, at any point in the network, leads to a two-phase short circuit through the ground and represents a serious accident, respectively, the inability to power the signaling equipment. This leads to a de-energization of the signal points and, as a result, the stoppage of trains. The problem is not solved by measuring the parameters of the earth fault current, since, due to the specifics of its formation, the magnitude and phase of the current do not depend on the distance to the place of the earth fault. In most cases, the phase-to-earth fault location of the overhead line of the central bank has a large transition resistance, which ranges from units of ohms to kOhms. Hidden earth faults (as a rule, with a large transition resistance) cannot be visually determined, which leads to large losses of working time of repair crews for troubleshooting, which negatively affects the smooth operation of trains. Currently, devices are used to find the place of a fault on the ground, directly or indirectly, according to the measurement results. Their use also requires large expenditures of working time, highly qualified staff or produces obviously inaccurate results due to not taking into account many influencing factors.

A device for determining the distance to the place of a single-phase earth fault in networks of 6-35 kV electrical systems with isolated or compensated neutral (options) [1]. The device is a complex of a measuring circuit, switching devices and a measuring and computing microprocessor device for recording and processing information. This device is adopted as a prototype. In the prototype, the assembly of the measuring circuit is carried out by disconnecting the damaged phase of the line from the power supply and connecting it on both sides to the intact phase. A current-limiting resistor is connected to the released pole of the switch, between it and the ground. The currents are measured by the phases of the line participating in the measurements, and the distance to the place of damage is determined by the ratio of these currents. The circuit is powered by a working AC source. However, currents occur through interphase capacitances. The component of this current is closed through the phase-to-earth capacitance of the wires of the undamaged phases of the line. The influence of this cannot be neglected, since the wire through which the current returns to the substation is located close to the wires involved in the measurement. The resulting absolute error curve characterizes that the measuring currents of less than 1 A give an error of more than 30%. For this reason, for measurements, a current value of more than 100 A is used, which is unacceptable for low-power transmission lines, which are signaling lines. In addition, if the value of the short circuit transition resistance is about 1 kOhm and the required current is more than 100 A, then the measuring voltage will far exceed the isolation capacity of the line, which can lead to irreparable consequences [2].

The aim of the invention is to determine the location of the phase short circuit to ground for low-power electric networks of longitudinal power supply of railways with insulated neutral, which is a high voltage signaling system.

This goal is achieved by jointly measuring the parameters of two line connection circuits (see drawing) with subsequent processing of the received information and transferring the distance from the substation to the place of the phase short circuit to ground, rather than measuring the parameters of one line connection circuit with subsequent processing of information, as in the prototype. The assembly of two line measurement circuits is carried out with the key K included at the end of the line. The measurement of the parameters of two circuits with information processing is carried out by a measuring device included in the substation at the beginning of the line. The measuring device has: a stabilized DC current source 1 connected between the near end of the line and the ground, a control device 2, a voltmeter 3, a current sensor 4, an arithmetic device 5, a functional corrector 6, and an information indicator 7.

The device works as follows: the first measuring circuit is assembled, in which the line power is turned off and at the near end at the substation, the damaged phase is connected to any of the undamaged phases. In the undamaged phase, the current sensor 4 (measuring shunt) is connected in series. At the far end of the line, a key K (any switching device 1 A or higher) is connected in the open position. The measuring device is connected with the switch K open, which supplies the circuit with direct current stabilized by the magnitude of the current (less than 1 A). The voltmeter 3 performs the peak-difference function of the peak voltmeter and is connected in parallel with the DC current source, which is triggered by the control device 2, measures the level of the received voltage and writes it to its memory. After the voltmeter receives information about the voltage of the DC current source 1 at the far end of the line, key K is turned on and collects a second measurement circuit. The control device 2 re-submits a command to the voltmeter 3, which performs a new measurement of the voltage of the DC current source and performs the function of subtracting the received voltage from the voltage stored previously in the memory. The magnitude of the difference of these voltages is supplied to the arithmetic device 5. The arithmetic device 5 performs the function of dividing the obtained voltage difference by current, the level of which is removed from the current sensor 4, connected in series in the undamaged phase of the line. The current value of the sensor 4 is the difference between the total stabilized supply current and the current of the damaged line. The obtained signal value after the division function is proportional to the value of the line resistance from the near end of the line at the substation where the measuring device is turned on, to the point of phase to ground fault. Subsequently, this signal is converted into functional corrector 6, according to a pre-existing program for this overhead line, taking into account the longitudinal heterogeneity of the line (cable inserts, different types and diameters of wires). In addition, the corrector 6 translates the resistance value into the distance from the near end of the line to the point of earth fault and subsequently displays information 7 on the indicator. The measuring and computing and control parts of the device, in addition to a stabilized constant current source of direct current, can be performed on the basis of computing complexes (CPI).

The proposed device, in contrast to the prototype, provides the determination of the place of a short circuit in low power lines at very small test currents, and a large transition resistance in the place of a phase short to ground.

LITERATURE

1. RF patent No. 2096795 for the invention. A device for determining up to the place of a single-phase earth fault in 6-35 kV networks of electrical systems with isolated or compensated neutral (options) (Pupynin V.N., Nguyen V.Kh. (Russia), 1998)

2. Nguyen V.Kh. Determination of the distance to the earth fault location in 6-35 kV networks with isolated or compensated neutral. The dissertation for the degree of candidate of technical sciences. UDC. 621.316.13. M .: 1998

Claims (1)

A device for determining the distance from the near end of the line at the substation to the place of a single-phase earth fault in networks with isolated neutral, containing a current sensor included in one of the intact phases, closed at the near end of the line with a damaged phase, a key installed at the far end of the line with the possibility of short circuiting between themselves and opening of the damaged phase and the undamaged phase with the current sensor, and the measuring part with the arithmetic device, functional corrector and indicator connected in series ohm, characterized in that it further comprises a stabilized DC current source designed to power the generated measurement circuits with the same current value and connected between the ground and the phases closed at the near end of the line, and a control device and connected in parallel to the measuring part stabilized DC current source voltmeter, and the control device is configured to control the operation of the voltmeter to implement peak peak function voltmeter for modes with open and closed key and with the ability to control an arithmetic device that receives information from the voltmeter on the function of subtracting the voltage obtained in the second mode from the voltage of the first mode, previously stored in memory, the arithmetic device is configured to divide the resulting voltage difference by the current measured by the current sensor and transmitting the division result to the functional corrector, and the latter is configured to take into account the parameter in line and converting the result of dividing into a signal convenient for output to display information about the distance from the substation to the fault location phase to earth.