RU1793506C - Device for protection of electric installation - Google Patents

Abstract

SUMMARY OF THE INVENTION: The introduction of three voltage transformers, three line voltage converters, an analysis / asymmetry line voltage unit, a fourth resistor, a fourth comparator and a third time relay can improve the reliability of the device. 2 ill.

Description

The invention relates to electrical engineering, in particular to current relay protection in case of asymmetric damage to a 35/6-11 kV step-down transformer and its load.

A device is known for protecting the electric motor from operating in two phases, comprising, according to the number of phases, the input sensors of the module, the inputs of which are connected to the output circuits of current transformers, and to the outputs of the sensors, where the modules of rectified and smoothed signals are provided, blocks for extracting the maximum and minimum from signals (BVMK, BVMN), a unit for comparing the difference between the modules of these signals (BC (MK-MN), a unit for extracting a signal proportional to the average value of the modules for phase currents (BVSRZ), a unit for generating the sum of this signal with aznostyu modules maximum and minimum of the signals (FRF (SRH + (MK (MH)), said first comparator input connected to the output of the BS unit (MC-MN), a second comparator input connected to the output block

BSM (SRZ + (MK-MN)), the outputs of both comparators are connected to the inputs of the logic element AND, the output of which is connected to the input of a time relay, whose make contact acts to trip.

A disadvantage of the known device is aggravated by the fact that it has separate executing devices that react

one only for the occurrence of nonsymmetry of the second type, when for two phase currents each w modules exceeds the average value of the modules of three phase currents; the other - only on the occurrence of an asymmetry of the first type, when for one phase current the module exceeds the average value of the modules of three phase currents.

A three-phase relay (current or voltage) is known that contains, according to the number of phases, the input sensors of the module, the inputs of which are connected to the output phase circuits of the current transformers or to the output linear circuits of the voltage transformers, and to the outputs of the sensors, where rectified and smoothed modules are provided signal 1

Yu SO

ate about

ON

In this case, a unit for asymmetry analysis is connected, at the output of which the current is proportional to a function that is equal to zero in the presence of a three-phase symmetric mode at the input of the sensors due to the fact that in asymmetric mode the intermediate-in-signal signal is taken with a negative coefficient, at which it balances in symmetric mode taken with a positive coefficient, the largest and smallest modulo signals, and at the output of the asymmetry analysis unit the inputs of two comparators that respond to the input currents of zhnyh directions.

 The disadvantage of this device is that it is not intended to be used for a transformer as an additional protection in case of asymmetric damage. . . . .

The aim of the invention is to increase reliability.

In FIG. 1 shows a network diagram with the installation of protection kits; in FIG. 2 is a functional diagram of a device.

The device for protecting the electrical installation of alternating current contains three phase 1-3 current transformers, the outputs of which are connected to the inputs of converters 2-4 AC to DC, the outputs of which are connected to the phase-unbalance analysis unit 5 of the phase currents, and the output of the latter is connected through a resistor b the first comparator 7, through the second resistor 8, the second comparator 9, through the third resistor 10 - the third comparator 11, between the terminals 12,13 of the operational power supply connected in series are the make contact 14 of the first of the second comparator 7 and the winding of the first time relay 15 and the serially connected make contact 16 of the second comparator 9 and the winding of the second time relay 17 and the additionally connected three voltage transformers 13-20, three voltage converters 21-23, asymmetry analysis unit 24 line voltages, the fourth resistor 25 and the fourth resistor 25 and the fourth comparator 26, connected in series and connected in parallel to the windings of the first time relay 15 making contact 27 of the fourth compar ator 26 and the winding of the Third time relay 28.

In FIG. generator 29, circuit breakers 30-35, current transformers 36 and transformer current protection unit 37, power transformer 38, AC electrical protection unit 39, voltage transformer unit 40-20 are indicated.

The device operates as follows. .-.

In normal operation, at the outputs of current transformers 1-3 and voltage transformers 21-23 there are

signals that do not exceed the trip settings of comparators 7, 9, 11 and 26. If a short circuit occurs on the 35 kV side, the signal from 1-3 current transformers through converters 2-4 and the unit

5 arrives at the inputs of the comparators 7, 9, 11. In this case, the comparator 11 is triggered, but the comparator 9 does not work, the setting of which is different.

When one of the phases breaks in the 35 kV network

the comparator 9 is activated, its contact 27 is closed and the time relay 28 is activated, the shutdown is performed with a predetermined time delay. When a short circuit occurs on 6 kV buses

the comparator 7 is triggered, its make contact 14 is closed, the time relay 15 is triggered, the trip will occur with a given time delay,

In the event of damage on the 6 kV outgoing lines due to phase voltage asymmetry, comparators 7 and 26 operate, close their contacts 14 and 16, time relays 15 and 17 are current-flowing, time delays of relays 15 and 17 have different

time delay 2, 1 s and 0.7 s, respectively. In this case, the low voltage switch is opened.

Claims (1)

The formula of the invention A device for protecting an electrical installation of alternating current, containing three phase current transformers, the outputs of which are connected to the inputs of AC converters to a constant voltage, the outputs of which are connected to the analysis unit of the asymmetry of phase currents, to the output of the latter through the first resistor, the first comparator, through the second resistor - the second comparator, through the Third resistor - the third comparator, in series between the terminals of the operational power supply are connected in series contact of the first comparator and the winding of the first time relay, serially connected the make contact of the second comparator and the winding of the second time relay, characterized in that, in order to increase reliability, three voltage transformers, three line voltage converters, an asymmetry analysis unit are additionally introduced line voltage voltages, a fourth resistor and a fourth comparator, connected in series and connected in parallel with the winding of the first time relay yuschy contact the fourth comparator, and the winding of the third timer. eighteen // ti f -HE Ј 2k 2.-I - / - L