RU2662639C1 - Method of the backup power supply fast switching on and device for its implementation - Google Patents

Abstract

FIELD: electrical equipment.

SUBSTANCE: backup power supply fast switching on method and device for its implementation relates to electrical equipment and, in particular, to the substations with the 6–35 kV voltage emergency control devices. Method consists in measuring of the main and backup power supply buses direct sequence voltage and current, angle between the main and backup power buses direct sequence voltage vectors, determination of the power direction at the main and backup sources input, switching the bus section from the main to the backup power source with the at least one phase power sign changing or reducing the input current of any phase below the set value and simultaneous decreasing the main power supply busbars direct sequence voltage below the predetermined level, or with the angle between the direct input sequence voltage vectors increase above the predetermined value, while the voltages on the backup input line exceed the predetermined value; according to the invention, with reduction of one or more line voltages in the main input below the predetermined value and the absence of conditions for the starting device triggering during the predetermined time interval T, blocking the starting device until voltages at this input are restored, and to determine the power direction, the phase current values are multiplied by the delayed linear voltage values for time T between the same input two other phases, obtained values are integrated, determining the sign of the result, at that, the delay time T is selected taking into account of the industrial frequency period and the set maximum sensitivity angle. Device contains main [1] and backup [2] power supplies, operating inputs [3] and [4] input circuit breakers, sectional switch [5], substation bus sections [6] and [7], three-phase current transformer [8] at the input of the main power sources, voltage transformers [9], [10] on the main and backup power supplies buses, high-speed starting device (SD), circuit breakers control unit [26]. Quick acting starting device includes: minimum voltage relay unit [11], time delay element [12], angle between the main and backup power sources [13] – [15] direct sequence vectors determining relay units, maximum voltage relay unit [16], “4OR” logic element [17], “4AND” logic element [18], phase power direction determination units P1–P3, each of which consists of delay line [19], multiplier [20], adder-accumulator [21], sign determination unit [22], minimum current detection unit [23], “2OR” logic element [24], which outputs are combined by the “3OR” logic element [25]. By its inputs the “4AND” logic element combines the time delay element [12] inverted output, the of “4OR” logic element [17] output, maximum voltage relay unit [16] output, “3OR” logic element [25] output.

EFFECT: method and device allow to increasing the emergency modes in substation power supply circuits detection reliability, eliminate false alarms and reduce the consumers to backup source switching times.

2 cl, 1 dwg

Description

The invention relates to electrical engineering and, in particular, to emergency control devices for substations with a voltage of 6-35 kV. The proposed method can be used to detect damage to the power supply network of the switchgear immediately at the time of their occurrence in order to implement fast switching consumers to a backup power source.

A known method of turning on the backup power of consumers [Patent for the invention of the Russian Federation No. 2326481, IPC H02J 9/06, publ. 06/10/2008], in which the voltage of the direct sequence voltage of the buses of the main and backup power supply is measured, the angle between the voltage vector of the direct sequence voltage of the buses of the main and backup power supply is measured, the direction of the active power at the input of the buses of the main power supply is determined, the buses of the main power supply are switched on standby when the voltage on the buses of the main power source decreases below a predetermined level or when the angle between the direct sequence voltage vector is exceeded more than 3 and this direction of active power from the tire to the main power source, moreover, measured minimum current input of each section by comparing it with a predetermined input current value, and when exceeding a given current also switches to a backup power source.

This method has a low speed of its work and low reliability when asymmetrical short circuit in the power supply, due to the inability to correctly determine the direction of the reactive component of power.

A device for automatically turning on the backup power supply to consumers [Patent for the invention of the Russian Federation No. 2447565, IPC H02J 9/06, publ. 04/10/2012], containing a main and backup power supply, input switches of working inputs, a section switch, substation busbar sections, three-phase current transformers at the inputs of the main and backup power supplies, voltage transformers on the buses of the main and backup power supplies, a starting device, containing blocks for generating vectors of phase currents and linear voltages, blocks for checking the values of phase currents for compliance with the minimum value, blocks for determining the minimum values of linear voltages on sections of the main and backup power supplies, power direction determination blocks in the phases of inputs from the primary and backup sources, “AND” logic elements, “OR” logic elements, circuit breaker control unit, protection relay and automation relay signal blocks.

Such a device has a low speed due to the complexity of the implementation of all elements of the starting device and the lack of a diagnostic function of the health of the measuring circuits.

The closest in technical essence is the way to automatically turn on the backup power supply to consumers [RF patent No. 2398338, IPC H02J 9/06, publ. August 27, 2010], which consists in measuring the voltage of the direct sequence on the buses of the main and backup power sources, the angle between the vectors of the voltage of the direct sequence of the buses of the main and backup power sources, measuring separately for each of the three phases at the input of the main source the values of the effective current in the phase and the angle between the vector of the complex effective current in the same phase and the vector sum of the complex effective voltage between the two other phases on the buses of the main source and is accepted equal to from 0 to 50% of the share of the same complex effective voltage on the buses of the backup source, measuring the change in the angle between the voltage vectors of the direct sequence of buses of the main and backup sources for a given period of time and switching the power supply of the buses of the main source to the backup when any of the measured voltages on the tires of the main the source is lower than the specified value or when the angle between the voltage vectors of the direct sequence of buses of the main and backup sources is increased above value or when changing the angle between the voltage vectors of the direct sequence of buses of the main and backup sources for a given period of time above a specified value, when at the same time the value of the effective current in any of the phases at the input of the main power source and the angle between the vector of the complex effective current in this the same phase and the above vector sum reaches the specified range of values, and the voltage of the direct sequence on the buses of the backup power source exceeds the specified value Eden.

However, with this method, for a short-time separation of networks with a loss of synchronism between the main and backup inputs, a false triggering of the PU can occur with subsequent non-synchronous switching on of the load due to fluctuations in the resulting voltage vector of the blocks of special relay bodies. In addition, the method has a low speed, since it requires significant computational costs for processing complex values of current and voltage at each input for a phase-by-phase analysis of the power direction and switching conditions to the reserve.

A device for automatically turning on the backup power supply to consumers [Patent for the invention of the Russian Federation No. 2398338, IPC H02J 9/06, publ. August 27, 2010] to automatically turn on the backup power supply to consumers, containing the main and backup power supplies, input switches of the main and backup power supplies, a section switch, buses of the main and backup power supplies, a set of current measuring transformers at the input of the main power supply, measurement kits voltage transformers on the buses of the main and backup power sources, a starting device for automatically switching on the reserve, containing the recovery unit the third phase current, equipped with three output channels, an analog-to-digital current converter, the input of which is connected to the output of the set of measuring current transformers through the recovery unit of the third phase current, equipped with three output channels, analog-to-digital voltage converters, the inputs of which are connected to the outputs of the sets of measuring transformers voltage on the tires of the main and backup power supplies, direct sequence voltage detection units on the tires of the main and reserve power supply sources, the inputs of which are connected to the output channels of analog-to-digital voltage converters on the buses of the main and backup power sources, respectively, the maximum voltage relay unit, the input of which is connected to the output of the direct sequence voltage detecting unit on the buses of the backup power source, the relay unit for determining the angle between direct sequence voltage vectors on the buses of the main and backup power supplies, the inputs of which are connected to the blocks for determining direct sequence voltage on the buses of the main and backup power sources, a device that switches to the backup power source with the main contacts of the section switch closed at the moment close to common mode between the same voltage on the buses of the main and backup power sources, activated when a command is received from the starting device inclusion of reserve.

In such a device, with an interphase short circuit in the power supply circuit of the section, one of the line voltages on the first section of the switchgear will be zero and the device will not work. In addition, the device is not operable in the absence of synchronism between the inputs of the main and backup power sources, the device does not have diagnostic functions for the health of the measuring circuits.

The technical result of the invention is to increase the reliability of identifying emergency conditions in the power supply circuit of the substation, eliminating false alarms and reducing the time that consumers switch to a backup source.

This is achieved by the fact that in the method for quickly turning on the backup power supply, which consists in measuring the voltage and current of the direct sequence of buses of the main and backup power sources, the angle between the voltage vectors of the direct sequence of buses of the main and backup power sources, determining the direction of power at the input of the main and backup sources, switching the bus section from the main to the backup power source when changing the sign of power in at least one phase or reducing the input current phase lower than the specified value and at the same time decreasing the voltage of the direct sequence of buses of the main power source below the specified level or with an increase in the angle between the voltage vectors of the direct sequence of inputs is greater than the specified value, while the line voltage at the backup input exceeds the specified value; according to the invention, when one or several line voltages decrease at the main input below a predetermined value and there are no conditions for the triggering device to operate within a specified time interval T, the starting device is blocked until the voltage is restored at this input, and to determine the direction of power, the phase current values are multiplied by the values of the linear voltage delayed by time T between two other phases of the same input, the obtained values are integrated, they determine the sign of the result, while in emya delay T is selected taking into account the period of the power frequency and a predetermined angle of maximum sensitivity.

The specified technical result is achieved by the creation of a device for the fast switching on of the backup power supply, containing input switches of the main and backup power sources, a section switch, voltage measuring transformers on the buses of the main and backup sources, a current transformer at the input of the main power source, a starting device, the outputs of which are connected via the control unit to the input and section switches, the relay block of the maximum voltage, the input of which is connected with the output of the measuring voltage transformer of the backup power source, the undervoltage relay block, the input of which is connected to the voltage measuring transformers of the main power source, the relay blocks for determining the angle between the voltage vectors of the direct sequence of the main and backup power sources, the inputs of which are connected to the corresponding voltage measuring transformers of the main and redundant power supplies connected in such a way that the output of the unit is minimal voltages, together with three outputs of the blocks for determining the angle between the voltage vectors, are connected to the inputs of the 4OR logic element, the high-speed starting device is equipped with a blocking circuit consisting of a minimum voltage relay block, which is connected to the first input of the 4I logic element through the time delay element, blocks determining the direction of power in the input phases consists of a multiplier, the first input of which is connected to a measuring current transformer and simultaneously the input of the minimum of the current, the delay line connected between the output of the voltage measuring transformer and the second input of the multiplier, the accumulator-accumulator connected by its input to the output of the multiplier, the sign determination unit connected to the output of the accumulator-accumulator, the “2OR” element whose inputs are connected respectively to the output of the determination unit the minimum current and the sign determination unit, while the outputs of the “2OR” elements of each block are combined by the “3OR” element and connected to the fourth input of the “4I” element, while the third input The “4I” switch is connected to the output of the maximum voltage relay unit, the second input of the “4I” element is connected to the output of the “4И” element, while the output of the “4I” logic element is connected to the input of the switch control unit.

The bus section is switched from the main to the backup power source when the power sign changes at least in one phase or the input current of any phase decreases below the set value and the direct sequence voltage of the main power supply bus line decreases below the set value or when the angle between the input sequence voltage vectors increases more than the set value, while the line voltage at the backup input exceeds the set value. Moreover, to reliably determine the direction of power, the phase current values are multiplied by the line voltage values delayed by time T between two other phases of the same input, the obtained value is integrated over an interval equal to the period of the industrial frequency and the sign of the result is determined, while the delay time T is selected taking into account period of industrial frequency and a given angle of maximum sensitivity. In addition, to eliminate false alarms and detect malfunctions in the measuring circuits of voltage transformers, a blocking function is introduced into the trigger algorithm, which is activated if one or more line voltages drop below the specified value at the main input and there are no conditions for the trigger to trip within a specified interval time T. After blocking, the starting device is in the indicated state until the voltage is restored at the main voltage de. The blocking function eliminates the false triggering of the starting device in case of malfunctions in the measuring circuits of voltage transformers, which usually arise due to erroneous actions of the operating personnel. The blocking function can be considered as a function of self-diagnosis, as well as to identify abnormal situations during the operation of the starting device.

The essence of the invention lies in the fact that due to the introduction of the phase power determination unit Px, implemented in a special way, the operation algorithm of the starting device becomes stable in close short circuit modes, when the direct sequence voltage is strongly distorted or disappears altogether. According to the new method, phase current samples I _k and line voltage samples delayed by time T between two other phases of the same input U _km are used to determine the phase power. The general expression for the delay value T expressed in steps of the sampling frequency m has the form:

where M = [2, 3 ... n] is the number of periods

industrial frequency;

F _d is the sampling frequency;

F _c is the frequency of the industrial network;

t _ms is the delay equivalent to the rotation of the power vector

the value of the maximum sensitivity angle ϕ _mch .

The expression for the kth value of the resulting power at the output of the integrator can be written as follows:

where F _d is the sampling frequency;

F _c is the frequency of the industrial network.

Thus, for the instantaneous power values obtained at each step, only the sign is evaluated, the negative values of which the starting device unlocks.

As an example, we consider the case of a short circuit in the supply network, when the line voltage at the output of the measuring transformer is strongly distorted or falls to the level of interference. In this case, the trigger algorithm maintains stability over time T by using phase voltage samples from the nearest history or, in other words, pre-emergency mode. For reliable operation of the starting device, the time T should be 2-3 times longer than the own operating time of the starting device, which in practice does not exceed 20 ms. After the triggering device is triggered, a further change in the voltage at the damaged input is not monitored by the algorithm until the intervention of operational personnel or the expiration of the delay time for returning to normal mode (VNR).

The introduction of the blocking function allows you to identify situations associated with malfunctioning circuits of measuring voltage transformers (VT). The principle of determining the malfunction is based on the fact that when any linear voltage drops below the minimum value and there is no enable signal from the phase power detection units during the time interval T, the starting device is blocked for a while until the voltage reaches its rated value. Note that a similar situation can also occur with close faults on the consumer side, when the power does not change its direction and feeds the fault location. In this mode, the starting device does not work and is blocked after time T, waiting for the selective action of relay protection and automation devices.

It should be noted that the methods of operation of the phase power determination unit and the blocking function are simple to implement and have high speed, since they do not use complex quantities and trigonometric functions in their work.

The essence of the method is presented in the drawing, which shows a functional diagram of a device for quickly turning on the backup power supply of consumers implemented on the basis of a microprocessor device and implementing the specified method.

The device contains a primary 1 and a backup 2 power sources, input switches of the working inputs 3 and 4, a section switch 5, busbars of the substation 6 and 7, a three-phase current transformer 8 at the input of the main power sources, voltage transformers 9, 10 on the buses of the main and backup sources power supply, high-speed starting device (PU), control unit for switches 26. High-speed starting device contains: relay block of minimum voltage 11, delay element 12, relay blocks for determining the angle between direct sequence vectors of the main and backup power supplies 13-15, maximum voltage relay unit 16, 4IL logic element 17, 4I logic element 18, phase power direction determination blocks P1-P3, each of which consists of a delay line 19, the multiplier 20, the accumulator-drive 21, the unit for determining the sign 22, the unit for determining the minimum current 23, the logical element "2OR" 24, the outputs of which are connected by the logical element "3OR" 25. The logical element "4I" combines its inverse output element that time delay 12, the output of the logic element “4OR” 17, the output of the relay block of the maximum voltage 16, the output of the logic element “3OR” 25.

The device is a quick turn-on backup power operates as follows.

In the initial state, when there is no damage at the inputs of the supply network, the input switches BB1, BB2 are turned on, the section switch CB is off. In this mode, the power is directed from the power sources to the substation buses, the voltages at the main and standby inputs are close to their nominal values, the phase difference between them does not exceed the set value, phase currents are higher than the minimum values, while a log is present at the output of the relay block of the minimum voltage. "0", at the output of the relay block of the maximum voltage there is a log. “1”, a log is present at all outputs of the relay sides of determining the angle (13-15). "0", at the output of all phase power determination units (P1-P3) there is a log. "0", while the signal at the output of the logic element 25 is equal to the log. "0", which in turn blocks the operation of the starting device.

In the initial state, when two or three-phase faults occur in the main power supply circuit, the phase currents receive a phase shift relative to their initial position, which is expressed in a change in the current value and the sign of the phase power. When the power sign changes from a positive value to a negative, a log appears at the outputs of elements 22, 24, 25. "1", which will lead to the unlocking of the PU. If in this state the direct sequence voltage decreases at the main input below the minimum value, which corresponds to the log. “1” at the output of block 11 or an excess of the angle between the voltages of the direct sequence of the main and backup inputs is greater than the maximum, which corresponds to the log. “1” at the output of at least one of the blocks 13-15 and the voltage of the direct sequence at the backup input is higher than the specified value, which corresponds to the log. "1" at the output of block 16, then at the outputs of the logic elements 17, 18 will appear the value of the log. "1", which will lead to the operation of the control unit and switching consumers to the backup source by turning off the switch 3 and turning on the section switch 5.

In the initial state, when one or several linear voltages of the main input decrease below the minimum value, a log appears at the output of the minimum voltage relay block. “1” and, if a change in the sign of power is detected in at least one of the blocks P1-P3, an enable signal log appears at the output of the “3OR” logic element. “1”, the starting device is triggered, the switch 3 is turned off, the sectional switch 5 is turned on, while the consumer power is switched to the backup source. In the case when the fact of a power change in the blocks P1-P3 was not detected during the time T, this mode of operation is regarded as a malfunction of the voltage circuits of the PU, while a blocking signal log appears at the output of the time delay element. "0" and the PU is blocked until voltage is restored on the measuring circuits of the main input.

In the initial state, when any of the phase currents falls below a predetermined value, an output log signal appears at the outputs of the corresponding unit for determining the minimum current 23 and then at the outputs of the logic elements 24, 25. “1”, the control panel is unlocked, expecting a decrease in voltage at the main input or an increase in the phase angle between the direct sequence vectors of the main and backup inputs. If any of the two conditions mentioned above occurs, the control unit is triggered and the consumer power switches to the backup source.

The quick-turn-on backup power supply method and the device for its implementation can be used to detect power supply disturbances for consumers with any type of damage in the mains and bus sections to quickly switch to the backup power source. At the same time, the blocking function allows timely detection of malfunctions of the voltage measuring circuits during operation, excluding false triggering of the starting device.

Using the method and device for the fast switching on of the backup power supply increases the reliability of identifying emergency conditions in the power supply circuits of the substation, eliminating false alarms and reducing the time that consumers switch to a backup source.

Claims (2)

1. A method for quickly turning on the backup power supply, which consists in measuring the voltage and current of the direct sequence of buses of the main and backup power sources, the angle between the voltage vectors of the direct sequence of buses of the main and backup power sources, determining the direction of power at the input of the main and backup sources, switching the bus section with main to the backup power source when changing the sign of power at least in one phase, or reducing the input current of any phase below a given value while decreasing the voltage of the direct sequence of buses of the main power supply below a predetermined level, or when the angle between the vectors of voltage of the direct sequence of inputs is greater than the specified value, while the line voltages at the backup input exceed the specified value, characterized in that when decreasing at the main input one or more line voltages below a predetermined value and the absence of conditions for the triggering device to trigger during a given time interval T starting the device is blocked until the voltage is restored at this input, and to determine the direction of power, the phase current values are multiplied by the linear voltage values delayed by time T between two other phases of the same input, the obtained values are integrated, the result sign is determined, and the delay time T is selected from taking into account the period of industrial frequency and a given angle of maximum sensitivity. 2. A device for the fast switching on of the backup power supply, containing input switches of the main and backup power sources, a section switch, voltage measuring transformers on the buses of the main and backup sources, a current transformer at the input of the main power source, a starting device, the outputs of which are connected through the control unit to the input and sectional switches, relay block of maximum voltage, the input of which is connected to the output of the measuring voltage transformer p redundant power supply unit, the undervoltage relay unit, the input of which is connected to the voltage measuring transformers of the main power supply, the relay blocks for determining the angle between the voltage vectors of the direct sequence of the main and backup power supplies, the inputs of which are connected to the corresponding voltage measuring transformers of the main and backup power sources, connected so that the output of the undervoltage block together with the three outputs of the determination blocks the head between voltage vectors is connected to the inputs of the “4OR” logic element, characterized in that the high-speed starting device contains a blocking circuit consisting of a minimum voltage relay block, which is connected through the time delay element to the first input of the “4I” logic element, power direction determination blocks in the input phases, consisting of a multiplier, the first input of which is connected to a measuring current transformer and at the same time the input of the unit for determining the minimum current, delay line, including between the output of the voltage measuring transformer and the second input of the multiplier, the accumulator-accumulator connected by its input to the output of the multiplier, the sign determination unit connected to the output of the accumulator-accumulator, the “2OR” element, the inputs of which are connected respectively to the output of the minimum current determination unit and the unit determine the sign, while the outputs of the “2OR” elements of each block are combined by the “3OR” element and connected to the fourth input of the “4I” element, while the third input of the “4I” element is connected to the output maximum voltage relay unit, the second input of the 4I element is connected to the output of the 4IL element, while the output of the 4I logical element is connected to the input of the circuit breaker control unit.

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