RU191462U1 - SOURCE OF SUPPLIED VOLTAGE OF THE SYSTEM OF SELECTIVE CONTROL OF THE STATE OF INSULATION OF THE GROUP OF ELECTRIC MOTORS WITH VOLTAGE ABOVE 1 KV - Google Patents

Abstract

The utility model relates to the electric power industry and can be used in auxiliary systems of thermal and nuclear power plants as part of a selective monitoring system for the insulation state of a group of electric motors (ED). An improved source of applied voltage (TIN) is proposed, which is part of the selective control system for the insulation state of a group of electric motors with voltage above 1 kV under operating voltage using the applied alternating current method. The TIN includes a voltage transformer (VT), the high voltage windings of which are connected to a star with a grounded neutral, and the low voltage windings are connected into an open triangle. In this case, between the output terminals of the additionally introduced static alternator (UHF) and the input terminals of the lower voltage windings of the specified transformer connected into an open triangle, an additionally introduced inductor is connected in series, parallel to the terminals of which an additionally introduced surge protector is connected, and an additionally introduced circuit breaker with an additional entered maximum current release. Due to the use of commercially available VTs and additionally introduced elements as part of the TIN, the dimensions and weight of the TIN are significantly reduced, which allows you to place the TIN in the cell of the complete switchgear of this VT, while ensuring the imposed current level required in the sensitivity of the insulation isolation control device in the circuit of these EDs and excluding the possibility of leakage through the elements of the INN, including along the windings of the VT, of unacceptable currents arising from a single-phase earth fault in the electrical network needs, reducing to an acceptable level the values of switching overvoltages on the throttle and RHF. 1 ill.

Description

The utility model relates to the electric power industry and can be used in auxiliary systems of thermal and nuclear power plants as part of a selective monitoring system for the insulation state of a group of electric motors (EM) for auxiliary needs of alternating current voltage above 1 kV under operating voltage, based on the applied alternating current method.

Known source of superimposed voltage (TIN), which is part of the alarm system and protection of the stator winding of a synchronous generator with a single-phase earth fault (OZZ), based on the method of superimposed alternating current, described in the operation manual [Siemens Siprotec 4, 7UM62, Manual C53000- G1176-C149-A, Edition 11.2017] and on p. 449-452 books [Schneerson E.M. Digital relay protection. - M .: Energoatomizdat, 2007. - 549 p.], Containing a static alternating current generator (RHF) as an alternating current generator, emitting alternating pulses, a resonant circuit tuned to the applied current frequency, a load resistor and a grounding transformer, through the windings of which The applied current enters the electric network with a controlled synchronous generator. A static alternator is connected in series with the resonant circuit. In parallel, a load resistor is connected, in parallel with which a low voltage (LV) winding of the grounding transformer is connected, connected in an open triangle.

The disadvantage of the described source is the use of non-standard equipment - a grounding transformer, not intended for installation on a withdrawable trolley of a cell of a complete switchgear (switchgear).

Known TIN, devoid of this drawback, used in the device alarm and protection against OZZ, based on the method of superimposed alternating current [Weinstein R.A., Kolodyazhny V.V., Yudin S.M. Device for protecting the generator-transformer block from earth fault. USSR author's certificate No. 1010690, Н02Н 7/06. Tomsk Order of the October Revolution and the Order of the Red Banner of Labor Polytechnic Institute. CM. Kirova, SU. Priority Date: 12/17/1980. Published: 04/07/1983]. The specified source of superimposed voltage as a generator of superimposed current contains a ferromagnetic frequency divider (DF), a high-quality resonant circuit tuned to the frequency of the superimposed current, and a commercially available voltage transformer (VT), through the windings of which the superimposed current enters the electric network with controlled electrical equipment. A ferromagnetic frequency divider is connected through a high-quality resonant circuit to the LV winding of a voltage transformer connected to an open triangle.

The ferromagnetic frequency divider and high-quality resonant circuit included in the specified TIN have large dimensions and weight and cannot be placed in the relay compartment of the switchgear switchgear VT, which is a disadvantage of this device.

The closest in technical essence to the proposed technical solution (prototype) is the applied voltage source used in the insulation monitoring, signaling and stator winding protection system of a synchronous generator in the case of OZZ based on the applied alternating current method [Sirota IM, Shapoval A.P. ., Bogachenko A.E., Dovbnya G.N. Protection against earth faults of the stator winding of block generators: Type KZS-25. - Kiev: IED, USSR Academy of Sciences, 1981. - 38 pp.], Containing a ferromagnetic frequency divider that produces superimposed current signals, a resonant circuit tuned to the superimposed current frequency, and a commercially available voltage transformer. A ferromagnetic frequency divider through a resonant circuit is connected to the LV winding of the specified voltage transformer connected in an open triangle.

The above TIN is used as part of an OZZ protection device, where high sensitivity to insulation resistance is not required, therefore, the imposed current created by it in the auxiliary electrical network is insufficient to perform selective monitoring of the insulation of electric motors with voltages above 1 kV. An increase in the level of the applied current in the auxiliary supply network with a voltage above 1 kV by increasing the power of this TIN will lead to an unacceptable increase in its dimensions and weight without the possibility of subsequent placement of this TIN in the relay compartment of the switchgear cell of the VT.

The objective of the utility model is to provide selective monitoring of the insulation of a group of auxiliary electric motors with a voltage above 1 kV using the superimposed alternating current method when placing the superimposed voltage source in the switchgear cell.

The technical result obtained by using the utility model is to provide the required level of the applied current in the auxiliary electric motor circuit and to avoid overloading the applied voltage source located in the switchgear cell.

The problem is solved in that an improved source of superimposed voltage is proposed, which is part of the selective control system for the insulation state of a group of electric motors with voltage above 1 kV under operating voltage using the method of superimposed alternating current. The specified TIN includes a static alternating current generator that generates bipolar impulses of superimposed current at the output, a choke connected in series with it, parallel to the clamps of which an overvoltage limiter is connected, a circuit breaker with a maximum current release and a commercially available voltage transformer whose LV windings are connected in an open triangle . A commercially available VT is installed on the withdrawable trolley of the switchgear cell, and the MHF, a choke with a surge suppressor and a circuit breaker with a maximum current release are installed in the relay compartment of the switchgear cell of this VT. The superimposed voltage source, the terminals of which are the terminals of the higher voltage winding (HV) connected to the star with a grounded neutral, commercially available by the VT, is connected to the auxiliary busbar section with controlled electric motors.

In FIG. 1 shows a diagram of the proposed TIN.

The TIN includes: a static alternating current generator RNG, which generates bipolar rectangular pulses at the output, an LR inductor with an FV surge suppressor, a QF circuit breaker with a maximum current release SQF and a commercially available TV voltage transformer.

The RHF static alternator is connected to the LV winding circuit of the voltage transformer TV, connected in an open triangle, through a series reactor LR, parallel to the terminals of which the surge suppressor FV is connected, and a circuit breaker QF with a maximum current release SQF. HV windings connected to a star with a grounded neutral of a commercially available voltage transformer TV are the TIN terminals. The superimposed voltage source is connected to the auxiliary supply buses A, B, C with voltages above 1 kV (usually 6 kV) and generates the superimposed current into the electric network with controlled electric motors.

The proposed device operates as follows.

In the normal mode, in the absence of defects in the insulation of the windings of the stators of the controlled motors, the superimposed voltage TIN source generates almost capacitive current on the A, B, C buses of the auxiliary section with voltages above 1 kV. This current is due to the capacitive conductivity of the insulation of equipment connected to the A, B, C buses of auxiliary power supply voltage above 1 kV. The voltage at the inductor LR does not reach the operating level of the surge suppressor FV. The current in the LV winding circuit of the voltage transformer TV connected in an open triangle does not reach the operation level of the maximum current release SQF. The maximum current release SQF does not operate and does not affect the opening of the QF circuit breaker. The power contact of the QF circuit breaker is closed.

With the deterioration of the insulation state of the electrical equipment connected to the auxiliary busbars A, B, C of the auxiliary section voltage above 1 kV, the applied current level in the circuit of this electrical equipment increases with an increase in the active component in this current, while the applied current level in the RHP alternator circuit is negligible declining. With a significant decrease in the insulation resistance of electrical equipment connected to buses A, B, C, in an auxiliary electrical network with a voltage above 1 kV, a voltage of zero sequence of industrial frequency appears, which is applied to the HV windings connected to the star with a grounded neutral voltage transformer TV. In this case, in the winding circuit of the LV voltage transformer TV connected in an open triangle, an industrial frequency current appears, limited by the inductor LR. Thus, a current consisting of a superimposed current and an industrial frequency current flows through the TIN elements. The level of this current is not enough to operate the maximum current release SQF, therefore, it does not act to trip the QF circuit breaker. The power contact of the QF circuit breaker is closed. The voltage at the inductor LR, caused by the superimposed current and the current of industrial frequency, does not reach the level of operation of the surge suppressor FV.

In the case of a single-phase earth fault in the auxiliary electric network with a voltage above 1 kV, the current in the LV winding circuit of the voltage transformer TV connected into an open triangle bounded by an inductor LR increases sharply and reaches the response level of the maximum current release SQF. The latter operates and acts to trip the QF circuit breaker. The voltage that occurs on the inductor LR when the circuit breaker QF is turned off rises to an unacceptable value and is limited at the level of the remaining voltage of the surge suppressor FV. Thus, the use of additionally introduced elements, namely, an LR reactor with an overvoltage limiter FV and a QF circuit breaker with a maximum current release SQF, eliminates the possibility of an unacceptable current flowing through an SIR, and reduces switching overvoltage when the LR inductor is turned off. Thanks to the proposed technical solution, the operability of the TIN located in the relay compartment and on the roll-out trolley of the switchgear cell of the commercially available VT is ensured.

The proposed source of superimposed voltage, used as part of a system for selective monitoring of the insulation state of auxiliary electric components of voltage above 1 kV under operating voltage, based on the method of superimposed alternating current, has the following set of advantages:

- the dimensions and weight of the superimposed voltage source are significantly reduced, the commercially available voltage transformer of which is installed on the withdrawable trolley of the switchgear cell of the VT, and the rest of the TIN equipment is installed in the relay compartment of the switchgear cell of this VT;

- excludes the possibility of leakage through the elements of the INN, including along the windings of the inverter, of unacceptable currents that occur during OZZ in an electrical network with controlled electric motors with voltages above 1 kV;

- the elements additionally introduced into the INN provide the level of superimposed current in the circuit of these electric motors required by the sensitivity conditions of the insulation insulation device for the electric motors and reduce the values of switching overvoltages on the LR inductor and the RHF alternator to an acceptable level.

Claims (1)

The applied voltage source, which is part of the selective monitoring system for the insulation of a group of electric motors with voltages higher than 1 kV under operating voltage using the applied alternating current method, comprising a voltage transformer, the high voltage windings of which are connected to a star with a grounded neutral, and the low voltage windings are connected to open a triangle, characterized in that between the output terminals of the additionally introduced static alternator and the input the presses of the low voltage windings connected in an open triangle of the specified voltage transformer include an additionally introduced inductor, parallel to the clamps of which an additionally introduced surge protector is connected, and an additionally inserted circuit breaker with an additionally entered maximum current release.

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