RU54210U1 - DEVICE FOR CONTINUOUS MONITORING THE STATE OF INSULATION OF HIGH VOLTAGE EQUIPMENT UNDER OPERATING VOLTAGE - Google Patents

Abstract

A device for continuous monitoring of the insulation state of high-voltage equipment under operating voltage, comprising an input unit, an adder, the inputs of which are connected to the outputs of the input unit, the first measuring and first signal units connected to the output of the adder, characterized in that a second measuring unit is additionally introduced into it, connected to the output of the adder, three threshold elements and a mini selector, the inputs of which are connected to the outputs of the input block, four elements AND, four elements NOT, the element BAN and second signal block, the outputs of the adder and mini-selector are connected, respectively, to the first and second inputs of the first and second measuring units, the outputs of the three threshold elements are connected, respectively, to the first inputs of the first, second and third elements And through the first, second and third elements NOT, the second inputs of the first, second and third elements AND are connected to the output of the second measuring unit, in addition, the outputs of all threshold elements are connected to the inputs of the fourth element And, the output of which is through the fourth element NOT connected to the blocking input of the BAN element, the input and output of which is connected between the output of the first metering unit and the input of the first signal block, and the outputs of the first, second and third elements AND are connected to the inputs of the second signal block.

Description

The utility model relates to the field of electric power industry and can be used at power plants and substations for continuous operational monitoring of the insulation state of high-voltage equipment under operating voltage by measuring leakage currents through its capacities.

At present, operational insulation monitoring is carried out using alternating current bridges by periodically measuring the dielectric loss tangent (tanδ) at a voltage of 10 kV [Collection of methodological manuals for monitoring the state of electrical equipment. - M .: 1998, p.198-205]. The disadvantages of this control are:

- the need to decommission equipment for production control;

- the practical impossibility of detecting insulation damage at an early stage of their development due to relatively rare control.

More promising are devices that monitor the state of insulation under operating voltage. Such devices implement the following control methods:

- nonequilibrium-compensation [Sw. P. M. Methods and diagnostic tools for high voltage equipment. M .: Energoatomizdat, 1992, p. 78-82];

- measurement of tanδ and insulation capacity under operating voltage [Collection of methodological manuals for monitoring the state of electrical equipment. - M .: 1998, p.69-72.];

- control of the level of partial discharges in the insulation of high voltage electrical equipment.

In recent years, devices that detect acoustic, thermal, light and radio frequency radiation, as well as performing chromatographic analysis of gases dissolved in oil, have also gained popularity. With the help of such devices periodically monitor the state of insulation. However, operating experience shows that the development of defects in the insulation of oil-filled equipment is avalanche-like in nature and in some cases from the appearance of the first signs of damage to the destruction of the equipment takes no more than two to three weeks. As a result, periodic monitoring is not always effective. The increase in the frequency of control is associated with a load of personnel and for this reason is not always possible. In connection with the aforementioned, devices that carry out continuous monitoring of insulation under operating voltage are more promising.

A known system for monitoring the insulation of high-voltage bushings [Russian Patent No. 2145420 of 1997.03.12], comprising a device for connecting to high-voltage bushings of three phases, the outputs of which are connected to the inputs of the corresponding instrument transformers, a voltage transformer of a three-phase system of high-voltage buses, the outputs of which are connected to the inputs of the corresponding instrument voltage transformers, signaling device, two phase shifters (PV) connected to the outputs of two of the three instrument current transformers, six low-pass filters ), a multiplexer, an ADC and a microprocessor, while the inputs of the two low-pass filters are connected to the outputs of the corresponding high-pass filters, and the inputs of the remaining low-pass filters are connected to the outputs of the corresponding instrument current and voltage transformers, the outputs of all the low-pass filters are connected to the corresponding inputs of the multiplexer, the output of which through the ADC is connected to the input of the microprocessor whose output is connected to signaling devices. An additional feature of the control system is that the PVs rotate the input leakage current vectors by 120 ° and 240 °.

The disadvantage of this device is the possibility of a false alarm about input malfunction when disconnecting a controlled connection. This is due to the fact that due to capacitive coupling in a disconnected connection, leakage currents may occur that are sufficient for a false alarm of the monitoring system about a malfunction in the insulation of the high voltage input.

The closest in technical essence to the proposed utility model (prototype) is a device for automatically monitoring the state of insulation of high-voltage equipment [A.S. USSR No. 296062].

This device automatically controls the insulation under operating voltage by measuring the magnitude and phase of the current through its capacitance and contains input, measuring and signal units, two adders, which summarize the currents of two monitored objects, and the measuring and signal units are connected to the difference of the input currents of these adders.

The description of the prototype invention provides theoretical calculations proving the possibility of improving the accuracy of control by increasing noise immunity. It is shown that, by subtracting the total leakage currents of two controlled objects after their preliminary alignment, the prototype of the device proposed by the authors eliminated the influence on the results of monitoring the voltage of the zero sequence of the network. However, compensation for interference caused by currents of influences does not occur. In particular, when a controlled object is turned off, in its leakage currents there are only influence currents, and at the input of the adder of the second controlled object, the influence currents may be different (when the object is running, they are close to zero). As a result, the device will give a false signal about the malfunction of the controlled object.

The possibility of generating a false signal about insulation failure when the controlled object is turned off is justified below.

The currents of influence in isolation are mainly due to capacitive coupling between the linear wires of neighboring objects. The capacity of the effects can be calculated by the formula:

where ε = ε ₀ = 8.85 · 10 ^-12 F / m is the dielectric constant of air;

l is the length of the length of wire on which the EMF of the effects is induced;

D is the distance between the linear wire of the controlled object and the wire of the adjacent (influencing) object;

R is the equivalent radius of the wire.

For existing open switchgears of power plants and substations, for example, 330 kV at a piece of wire de-energized on both sides with a length of l = 10 m C _ow = 46.3 · 10 ^-12 F. Then, for example, the leakage current through the insulation of a current transformer of 330 kV due to influences, with insulation capacitance C _of = 700 · 10 ^-12 F will be 2.6 mA. The current of influences, as the analysis shows, exceeds 6% of the normal leakage current. Operating experience has shown that the maximum permissible change in the leakage current of a current transformer with a voltage of 330 kV does not exceed 2%. Thus, the device will give a false signal about a malfunction in the insulation of the controlled object.

Under normal conditions (with the controlled object turned on), the capacitive conductivity of its insulation is shunted by the phase resistances of the transformers and autotransformers of the power plant or substation relative to the ground and the influence current, as the calculation shows, is not more than 0.001% of the normal leakage current.

The objective of the utility model is to create a device for continuous monitoring of the isolation of high-voltage equipment under operating voltage, causing the trust of operating personnel to the data received from this device by increasing its selectivity.

The technical result obtained by using the proposed device is to increase the recognition efficiency at an early stage of development of insulation damage of the controlled object, which, in turn, eliminates the possibility of its sudden failure and eliminates false alarms of the device for continuous monitoring of insulation caused by currents of influences when the controlled object is turned off, as well as damage (short circuits or breaks) of the input circuits of the specified device.

The problem is solved in that in the device for continuous monitoring of the insulation state of high-voltage equipment under operating voltage, containing an input unit, an adder, the inputs of which are connected to the outputs of the input unit, the first measuring and first signal units connected to the output of the adder, an additional second measuring unit is introduced connected to the output of the adder, three threshold elements and a mini selector, the inputs of which are connected to the outputs

input block, four AND elements, four NOT elements, the PROHIBIT element and the second signal block, the outputs of the adder and mini-selector are connected, respectively, to the first and second inputs of the first and second measuring blocks, the outputs of three threshold elements are connected, respectively, to the first the inputs of the first, second and third elements AND through the first, second and third elements are NOT, the second inputs of the first, second and third elements And are connected to the output of the second measuring unit, in addition, the outputs of all threshold elements are connected are connected to the inputs of the fourth AND element, the output of which through the fourth element is NOT connected to the blocking input of the FORBID element, the input and output of which are connected between the output of the first measuring unit and the input of the first signal unit, and the outputs of the first, second, and third AND elements are connected to the inputs of the second signal block.

The figure shows a functional diagram of the proposed device 1. Three-phase controlled object 2 (hereinafter referred to as the controlled object), represented by three conductivities (Y _A ) - 3, (Y _B ) - 4, (Y _C ) - 5, connected to a three-phase supply voltage , , . The input unit 6 of device 1 contains in its composition measuring transducers of leakage currents of phases A, B, C of the controlled object (IPA) - 7, (IPV) - 8, (IPA) - 9 (for example, resistive shunts or intermediate current transformers), which connected by the primary side in the circuit of the phase leakage currents of the monitored object, and the secondary side to the inputs of the adder (Σ) - 10. The output of the adder 10 is connected to the first input of the first measuring unit (IB1) - 11, the output of which is connected via additional connections to the input of the first signal unit (SB1) - 12. To the output of the adder 1 0 the first input of the second measuring unit (IB2) is also connected. 13. The outputs of the measuring transducers of the leakage currents of phases A, B, C of the monitored object (IPA) are 7, (IPV) are 8, and (IPS) are 9, the three threshold inputs are also connected phase elements A, B, C (PEA) - 14, (SEW) - 15, (PES) - 16, respectively, and mini selector (MIN) - 17 leakage currents of the three phases of the controlled object, the output of which is connected to the second inputs of the measuring blocks (IB1) - 11 and (IB2) - 13. The outputs of the three threshold elements (PEA) - 14, (SEA) - 15, (PES) - 16 are connected, respectively, to the first inputs of the first, second of the third and third elements And - 18, 19 and 20, as well as to the inputs of the fourth element And - 21, and the first inputs of the elements And - 18, 19 and 20 are connected with the outputs of the threshold elements (PEA) - 14, (SEW) - 15 and (PES) - 16 through the first, second and third elements NOT - 22, 23, 24. The second inputs of the elements AND - 18, 19 and 20 are connected to the output of the second measuring unit (IB2) - 13. The output of the fourth element And - 21 through the fourth element NOT - 25 is connected to the blocking input of the element PROHIBITION - 26, the input and output of which are connected between the output of the first measuring unit (IB1) - 11 and the input of the first signal block (SB1) - 12. The outputs of the first, second and third elements

And - 18, 19 and 20 are connected to the inputs of the second signal unit (SB2) - 27.

Device 1 operates as follows.

In the normal operation mode of a functioning controlled object 2, the phase conductivity flows through the phase conductivities (Y _A ) - 3, (Y _B ) - 4, (Y _C ) - 5 , , . In the input unit 6 of the device 1 by measuring transducers of leakage currents of phases A, B, C 7, 8, 9 of the controlled object 2, these currents are converted to levels convenient for further processing. The signals proportional to the phase leakage currents are summed by the adder (Σ) - 10. The resulting unbalance signal is small, and the ratio of the γ signal at the output of the adder 10 to the signal at the output of the mini-selector 17 does not exceed the response level of the first and second measuring units (IB1) - 11 and (IB2) - 13; at the outputs of the measuring units (IB1) - 11 and (IB2) - 13, the signals are 0. The threshold elements (PEA) - 14, (SEA) - 15 and (PES) - 16 are in the activated state; at the outputs of the first three elements And - 18, 19 and 20, the signals are zero due to the presence of elements NOT - 22 23 and 24, and also because the signal at the output of the second measuring unit 13 is zero. At the output of the fourth element And - 21, the signal is 1; due to the presence of the fourth element NOT - 25, at the blocking input of the element FORBID - 26 there is no signal, the internal key of the element FORBID - 26 is closed. The first signal unit 12 is in an unworked state, since the signal is equal to zero at the output of the first measuring unit 11, and there is no alarm about a malfunction of the controlled object 2. The signal at the output of the second signal unit 27 about a short circuit or open circuit of the input unit 6 of the device 1 is also absent.

With an unacceptable deterioration in the insulation of one or two phases of the controlled object 2 under operating voltage, the unbalance signal at the output of the adder 10 increases, the ratio of the γ signal at the output of the adder 10 to the signal at the output of the mini-selector 17 exceeds the response level of the first measuring unit (IB1) - 11, comprising 0.01 ... 0.08 relative units. The response level of the second measuring unit (IB2) - 13 is 0.5 ... 1.0 relative units, so the second measuring unit (IB2) - 13 does not work. Since the leakage currents in all phases exceed the thresholds of the threshold elements 14, 15 and 16, the latter are triggered and the signal is equal to 1 at the output of the fourth element And - 21. Due to the presence of the element NOT - 25, the internal key of the element BAN - 26 is closed and the first signal unit 12 gives a signal about the malfunction of the controlled object 2. Due to the failure of the second measuring unit 13 and the presence of the elements NOT - 22, 23 and 24, there are no signals at the outputs of the elements I - 18, 19 and 20, and a signal does not appear at the output of the second signal unit 27 and an input circuit block.

In case of disconnection of the controlled object 2 from the supply voltage , , with the output of the adder 10, a signal may appear due to the influence currents and exceeding the response threshold of the first measuring unit 11. However, none of the phase leakage currents exceeds the response thresholds of the threshold elements 14, 15 and 16. Due to this, the output of the fourth element And 21 signal is zero. At the output of element NOT 25, a signal equal to 1 appears, which causes the internal key of the element to PROHIBIT 26 to open and the first signal unit 12 does not give a false signal about a malfunction of the controlled object 2. The second signal block 27 also does not give a false signal about a malfunction of the circuits of the input unit 6 of the device 1, since the signal at the output of the second measuring unit 13 is equal to zero and, accordingly, at the outputs of the first three elements And - 18, 19 and 20, the signals are equal to zero.

In the event of a break or short circuit of the circuits in the input unit 6 of the device 1 (circuits of one or two measuring transducers of leakage currents of phases 7, 8, 9) in the normal operation of the controlled object 2 with intact isolation, the ratio γ significantly exceeds the response threshold of the first measuring unit 11 and it is enough for the second measuring unit 13 to operate. The signals at the outputs of the indicated blocks 11 and 13 are equal to 1. However, one or two of the threshold elements 14, 15, 16 do not work, namely, those connected to the measuring to browsers (out of 7, 8, 9) with damaged circuits, due to which the internal key of the PROHIBIT element is 26 open, and at the output of the first signal block 12 there is no false signal about a malfunction of insulation of the controlled object 2. At the output of one or two of the three elements And - 18, 19, 20, namely, associated with the measuring transducers (out of 7, 8, 9) of the leakage currents of a serviceable controlled object 2 having damaged circuits, a signal appears equal to unity. Due to this, the second signal unit 27 gives a signal about the malfunction of the circuits of the input unit 6 of the device 1.

Other modes of operation of the controlled object 2 and device 1, for example, a combination of damage to the circuits of the input unit 6 and the disconnected state of the specified object or a combination of damage to the circuits of the input unit 6 and the operation of the controlled object 2 with poor insulation, are not considered, since such modes are rare events that not difficult to show using methods of probability theory.

Thus, the proposed device for continuous monitoring of the insulation state of high-voltage equipment under operating voltage does not act falsely due to influence currents when the state of the monitored object is switched off and signals a circuit malfunction in the input unit of the device in the normal mode of operation of the monitored object with good insulation.

The proposed device has the following set of properties that none of the known devices of the same purpose have:

- the maximum simplicity of the device, which is achieved by measuring the leakage currents of the insulation of the phases of the controlled object and the unbalance signal (rather than measuring, for example, high-frequency currents of partial discharges or comparing the characteristics of the controlled object and the reference);

- alarm about unacceptable deterioration of insulation of various high-voltage equipment (oil-filled bushings of transformers and switches, oil-filled current transformers, voltage transformers and surge arresters);

- the absence of a false alarm in case of asymmetric damage in the high-voltage network, which is achieved due to a time delay exceeding the maximum response time of the backup relay protection of the network;

- the absence of a false alarm due to currents of influences when the controlled object is disconnected from the supply network;

- the presence of an alarm about the malfunction of the circuits of the input unit of the device in the normal mode of operation of the controlled object having intact isolation.

Claims (1)

A device for continuous monitoring of the insulation state of high-voltage equipment under operating voltage, comprising an input unit, an adder, the inputs of which are connected to the outputs of the input unit, the first measuring and first signal units connected to the output of the adder, characterized in that a second measuring unit is additionally introduced into it, connected to the output of the adder, three threshold elements and a mini selector, the inputs of which are connected to the outputs of the input block, four elements AND, four elements NOT, the element BAN and second signal block, the outputs of the adder and mini-selector are connected, respectively, to the first and second inputs of the first and second measuring units, the outputs of the three threshold elements are connected, respectively, to the first inputs of the first, second and third elements And through the first, second and third elements NOT, the second inputs of the first, second and third elements AND are connected to the output of the second measuring unit, in addition, the outputs of all threshold elements are connected to the inputs of the fourth element And, the output of which is through the fourth element NOT connected to the blocking input of the BAN element, the input and output of which is connected between the output of the first measuring unit and the input of the first signal unit, and the outputs of the first, second, and third AND elements are connected to the inputs of the second signal unit.