RU2015599C1 - Apparatus for protecting electric network portions from short-circuit currents - Google Patents

Abstract

FIELD: contact-free relay protection apparatuses for electric power plants. SUBSTANCE: apparatus has sensitive 1, time-setting 2 and actuating 3 devices. The apparatus is characterized by the use of threshold element 4, first 5 and second 6 delay elements, first 7 and second 8 AND gates, OR gate 9. The output of the latter is connected to the input of actuating device 1 and inputs are connected to the outputs of time-setting devices 2, first 7 and second 8 AND gates. The first input if first AND gate & is connected to the output of sensitive device 1 and second one is connected to the output of threshold element 4 and input of first delay element 5. The output of first delay elements 5 is connected to the RESET input of threshold element 4. The first input of second AND gate 8 is connected to the output of second delay element 6 the input of which is connected to the output of sensitive device 1 and the second input of second AND gate 8 is connected through communication line 10 (blocking one) to a lower-stage protection device. EFFECT: enhanced reliability. 1 dwg

Description

 The invention relates to electrical engineering, namely to non-contact devices of relay protection of three-phase AC networks and electrical installations against short circuit currents / short circuit / in low-voltage autonomous power systems, for example, ship.

 A device for protecting the maximum alternating current from short-circuit currents used in ship power systems, consisting of an input unit, a time delay unit, an intermediate or executive unit, an output unit and a power supply [1]. The output of the input unit is connected to the input of the time delay unit, the output of which through the intermediate unit is connected to the input of the output unit.

 A significant drawback of the device is the failure to operate when it is connected to an existing short circuit in the protected network due to the lack of current supply.

 A complete device for overcurrent protection of the type KMT3-50 [2] is known, consisting of a reactive, time-setting, actuator and a current power supply.

 When the current in the monitored network is equal to or greater than the current of the protection setting, the reacting body is activated and gives a signal to start the time-setting body, which, after the time determined by the time setting, sends a signal to the executive body.

 The disadvantage of this device is the long response time, determined by the selective setpoint in time when connected to an existing short circuit in the network. In addition, with a large number of selectivity steps, the response time of the protection device located near the generator is unacceptably large.

 There is a problem of increasing the speed of the upper stage protection devices during short circuit in their control zone and when they are switched on to the existing short circuit in protected network sections.

 The purpose of the invention is to increase the speed of protection devices during short circuit in network sections.

 This is achieved by the fact that a threshold organ is introduced into the device, the current response setting of which is less than that of the reacting organ and with the possibility of triggering at the second input from the auxiliary contact of the power switch when it is turned on, the first element is a "Delay" with a circuit "Reset" of the threshold organ associated with the first AND element, the OR element, as well as the second Delay, AND elements associated with the lower stage protection device.

 The specified solution allows to reduce the response time of the protection device of the upper, selective stage, with possible short-circuit in the controlled, “own” zone, as well as when switching on protection devices to the existing short-circuit in the network section, reducing it to its own time of operation of the circuit breaker, which increases the protection efficiency of autonomous power systems and limits the size of possible damage to electrical installations.

 The drawing shows a diagram of a device for protecting sections of the electrical network from short-circuit currents.

 The device comprises a reacting organ 1, a timing arm 2, an actuating organ 3, a threshold organ 4, a first delay element 5, a second delay element 6, a first AND element 7, a second AND element 8, an OR element 9, a communication line 10.

 The protection device contains a reacting body 1, a time-setting body 2 connected to it, an executive body 3, an OR element 9, the output of which is connected to the input of the executive body 3, and the inputs are with the outputs of the time-generating body 2, the first element And 7, the second element And 8, threshold organ 4, the output of which is connected to the second input of the first element And 7 and the input of the first element "Delay" 5, the output of which, in turn, is connected to the input "Reset" of the threshold organ 4, the second element "Delay" 6, the input of which is connected to the exit of the reacting organ 1, and the output is connected to the first input of the second element And 8, the second input of which is output via the communication line 10 to the lower stage protection device.

 The principle of operation of the protection device is as follows.

 When the protection device is switched on to the normal mode of the protected network, the threshold organ 4 is activated, allowing operation of the Delay element 5. / The delay time of the Delay elements, taking into account transient processes and, for reasons of noise immunity of the protection device, is selected within 0.02-0.06 s /. The latter, having counted the delay time, returns the threshold organ 4 to its original state. When this reacting body 1 is in an unused state, at the output of the OR element 9 there is no signal for the actuation of the executive body 3. At the second input of the second element And 8, in the case of a lower stage protection device connected to voltage, there is a logical signal "1" / hereinafter - a signal "1" /.

 When a short circuit occurs from the nominal mode in the control zone of the lower stage protection devices, the reacting organ 1 is activated, as well as the reacting organ of the lower stage protection device. At the second input of the second element And 8 appears the signal "0". By the signal of the reacting organ 1, the time-generating organ 2 begins to form its selective time delay. At the same time, under the conditions of selectivity, the lower stage protection device is activated earlier and turns off the emergency section of the monitored network. The responsive organ 1 returns to its original state, stopping the operation of the timing arm 2.

 In the case of a short circuit from the nominal mode in the controlled section of the network / when the signal "1" / is present at the second input of the second AND element 8, i.e. in the "own" zone, the protection device is activated accelerated in the circuit - element "Delay" 6 - element And 8.

 In the case of a deenergized feeder of the lower stage protection device, as well as during short circuit, breaks in the communication line 10, the proposed protection device will work with its selective time setting determined by the time setting body 2.

 When the protection device is switched on, the reacting organ 1 and threshold organ 4 are triggered on the short circuit existing in the controlled network. A signal “1” appears on both inputs of the And 7 element, a similar signal from the output of the And 7 element goes to the input of the OR element and the protection device works instantly, turning off damaged part of the network.

 The protection device allows simple means to increase the speed during short-circuit in your area, regardless of the value of the selective set point in time, as well as when you turn on the protective device on an existing short-circuit in the network and thereby reduce the size of possible damage to sections of the electrical network and electrical installations in emergency conditions, which increases reliability of the relay protection device as a whole.

Claims (1)

 DEVICE FOR PROTECTING ELECTRIC NETWORK SITES FROM SHORT-CIRCUIT CURRENTS, containing reactive and time-setting organs sequentially connected, an executive body, characterized in that a threshold organ, first and second delay elements, a first and second delay element AND, an first and second AND element, the output of which is connected to the input of the executive body, and the inputs with the outputs of the time-setting body, the first and second elements And, the first input of the first element And is connected to the output of the reacting body, and the second input is connected to the path of the threshold organ and the input of the first DELAY element, and the output of the first DELAY element is connected to the "Reset" input of the threshold organ, the input of which is connected to the input of the reacting organ, the first input of the second element And is connected to the output of the second element "delay, the input of which is connected to the output of the reacting body, and the second input of the second element And displayed through a communication line to the lower level protection device.