SU1686570A2 - Device for current protection of three-phase electric installation with automatic reclosing against interphase short-circuit - Google Patents

Abstract

The invention relates to power engineering, namely, to relay current protection of a three-phase electrical installation. The purpose of the invention is to increase the reliability of operation by eliminating false outages during line phase breaks. For this, three threshold elements, three AND elements, an TIME element and an EXCLUSIVE OR NO element are additionally introduced into the device. 1 il.

Description

The invention relates to power engineering, in particular, to relay current protection of a three-phase electrical installation with automatic reclosing (AR), can be used to protect busbars with branches and is an improvement of the device according to bus no. 1238187.

The purpose of the invention is to increase the reliability of operation by eliminating false disconnections at line phase breaks,

The drawing shows a functional diagram of the device.

The device contains measuring bodies 1-6. starting bodies 7-9, made in the form of overcurrent relay, elements TIME 10-20, elements OR 21-28, elements NOT 29-31, elements AND 32-42, elements MEMORY 43-46, executive body 47.

The device also contains threshold elements 48-50, elements AND 51-53, element OR-NOT 54, element TIME 55, element

EXCLUSIVE OR NOT 56, relay 57-59 position ON and relay 60 position OFF, 61-63 phase switches.

The device works as follows.

The time elements work TIME 10-12

ti t3an + 2 At;

working hours of elements TIME 13 and 14

t2 t3an + At;

working time of the element TIME 20

t3 t38n + 3 A t;

working time of the element TIME 15

t4 Btkl + At2,

working time element TIME 16

fc

O 00 o

ate

3

to

t5 HAPV + 1 on + Ati;

working time of the elements TIME 17-19

te toTun + Ati;

time element TIME 55

t7 t3an + 4 Ati.

where Hzap - self-load line load;

Ati - reserve time, D ti 0,5 s:

At2 - reserve time, Ata 0.1 s;

off time switch off time line;

tAHB time delay AR;

1In - time to turn on the line switch.

In the idle mode of the protected line, the starting and measuring units are not activated.

In the event of a short circuit, the current organs 2 or 1 and the trigger body 7 are triggered. In the future, the operation of the circuit is considered as applied to the current trigger and measuring organs. At the output of element 32, a signal appears that is present there until it completes element 10, the delay time of which, like the delay time of elements 11 and 12, is longer than the delay time of element 13.

Element 13 sends a signal to one of the inputs of element AND 41, on the other input of which the signal is already present (it is fed through the time tz ti after turning on the switch), as a result, the actuator 47 is triggered. When the load current increases from idle to enough actuation of the start-up unit 7 (the setpoint of the actuation of the organ 7 is less than the settings of the actuation of the current organs 1 and 2), the protection actuation setting is switched. Element 10 comes into action and after a time delay sends a signal to the element NOT 29, at the output of which the signal disappears. Subsequently, the operation of the organs 1 and 2, which have a response current that is much smaller than the nominal one, does not result in an output signal of the AND 32 element when the load current increases or a short circuit occurs. The device does not work if one of the line phases break, as the current remained at the same level.

If the load current does not exceed the actuation current of the starting organ 8. then a signal is present at the output of the elements HE 30 and 31. If a short circuit occurs at such a load, current organ 3 or 4 is triggered (the pickup value

each of them exceeds the setpoint of the current organs 1 and 2). At the output of element 14, a signal appears and, through the time delay of the element, the switch is disconnected. If the load current

there is more triggering current of the triggering organ 8, but less than the triggering current of the triggering organ 9, there is no signal at the output of elements 29 and 30, and no signal at the output of element 31. Short circuit

current organs 5 and b are triggered (the setpoints of which are greater than the settings of organs 3 and 4). Both inputs of the And 34 element receive signals and the protection shuts off the switch. When the loaded line is turned on from the control key, current organs (from inrush load currents), for example, 1 and 2, can be triggered, and, therefore, a signal appears at the output of the AND 32 element. However, the switch does not

is turned off, as the element TIME 20 delays the signal to elements 41 and 42 during ta ti and there are no signals at the output of elements AND 38 - 40, since there is no signal from the element MEMORY at the inputs of these elements

43 (AR does not work), and over time, element 10 removes the signal at output 32. By this time, the start of all load motors is completed and the circuit assumes its original position.

If there is a load current in the line, an interruption of one of the phases, for example, A, occurs, the current in the intact phases increases by a factor of VT, but the device does not work, as the threshold element of phase A returns to its original position. At the output of the element AND 51 there is a logical unit that, when it arrives at the first input, OR-NOT 54 will switch it to the zero state and block the elements 32 and 33 for the time t

operation of the element TIME 55. The last stage of protection is not blocked, and the starting body is retracted from the current vt3T | H, where 1M is the rated current. This ensures that the device is operational with a short circuit after the transformer in two phase operation mode.

When the line is turned on for a stable short circuit, the current and starting organs, for example, 1 or 2 and 7, are triggered.

the output of element 32 and the signal appears, as in the previous case. The element TIME 20 delays the supply of the signal to element 41 for a time rz n. After the element TIME 20 has been modified, and the short circuit has not been eliminated, the current organs 1 or 2 remain actuated. The OR 21 element remains triggered and a signal appears at the output of AND 42, since there are signals at its two inputs, 5 and in the inverse there is no signal, the TIME 15 element sends a signal only after time t4. During this time, the executive body 47 has time to turn off the switch.

When the line is disconnected for any reason, the relay 60 is switched off and disconnects and sends signals to the inverted inputs of the AND 35-37 elements, preventing the signal that came from the output of the HE elements 29-31 from storing the switch, if any, from before disconnecting absent. Elements 17-19 provide the necessary delay in the input of this signal until the relay 60 is triggered off.

Then the element TIME 16 begins to work and after the expiration of time 1b (if during this time the line does not turn on from AR), the memory of elements 38-40 is erased.

If the automatic reclosure switches on the line and, until the load is switched off, the line load is such that the triggering organ 7 is triggered and organs 8 and 9 are not triggered, then there is no signal at the output of MEMORY 44, but at the outputs of MEMORY 45 and 46. Before switching off to 30, the first input of element 35 does not receive a signal from element 29, and to similar inputs of elements 36 and 37 it comes from elements 30 and 31, and the signal from the position relay 35 does not go to the inverse input of each of elements 36 and 37 arrives

No signals are received on elements 25 and 26 that erase the memory.

If in the considered case the line turns on from automatic reclosing for a stable short circuit 40, current organs 1-4 are triggered. At the outputs of elements 38 and 40 there are no signals, and a signal appears at the output of element 39, since all its inputs have signals and after time element TIME 14 45 the switch is turned off. In case of successful reclosure, the current organs 1 - 4 may operate from the current of self-starting load of the line. But disconnection of the line does not occur because during the operation time of the VRE-50

ME 14 is self-starting, tokumensha-. The current organs 3 and 4 (possibly 1 and 2) are returned to the initial position, and the erase signal is sent to the MEMORY element 43 through t3. If the line is disconnected from the control key, then the automatic reclosure does not work, there is no signal at the output of MEMORY 43, and after a time ts the memory of elements 44 - 46 is reset through the elements OR 24 - 26. Thus, the device can operate at short-circuit currents much smaller than the rated current of the line, and does not work falsely after the action of AR, switching the switch on the load and when one of the line phases is broken.

Claims (1)

The invention The device for current protection against phase-to-phase short-circuit of a three-phase electrical installation with automatic reclosing (AR) according to the author. St. Nfe 1238187, characterized in that, in order to increase the reliability of operation by eliminating false disconnections at line phase breaks, three threshold elements are additionally introduced in it, the twelfth, thirteenth and fourteenth elements AND, the series-connected element OR-NOT, the eleventh element TIME and element EXCLUSIVE OR NOT. the inputs of the first, second and third threshold elements are connected to the secondary winding of the current transformer of the corresponding phase, their inverse outputs are connected to the first inputs of the twelfth, thirteenth and fourteenth elements, respectively, of the corresponding relay outputs of the corresponding phases, the output of the twelfth , the thirteenth and fourteenth elements And are connected respectively to the first, second and third inputs of the element OR NOT, the output of which is also connected to the second To the entrance of the EXCLUSIVE OR OR NOT element, the output of which is connected to the third inputs of the first and second elements I.