SU898548A1 - Device for protecting generator and transformer united in one system from earthing - Google Patents

Description

(Sh DEVICE FOR PROTECTION OF THE GENERATOR IN THE UNIT WITH THE TRANSFORMER OF THE CLOSE ON THE EARTH

I

The invention relates to relay protection and can be used to protect neutral-compensated generators operating in a block with a transformer.

A device is known comprising a control current source, six current transformers, a voltage transformer, a frequency multiplier, a MSI amplifier and a relay p.

However, this device is very complex.

The closest to the present invention is a device for protecting a generator-transformer from a circuit to earth, containing an actuator made at the zero indicator, the working winding of which through a rectifier sends a signal from the current sensor and the brake winding through a rectifier and filter is connected to voltage measuring transformer {

However, in this device, when the circuit is interrupted by a brake signal, for example, the fuse blown off the measuring voltage transformer or for other reasons, the braking is removed and the protection triggers falsely (existing requirements for relay protection devices do not allow the operation chains); when the reference current source fails, the protection can also falsely operate from natural zero-sequence currents.

15

The aim of the invention is to simplify protection, increase its sensitivity and reliability.

The goal is achieved by what organ

Claims (2)

20 comparisons are made according to a phase-sensitive circuit, one input of which is connected to the control current source, the second input to the current sensor through a filter, and the output to the actuator. The drawing shows the scheme of the device; the device contains a protected generator 1; arc coil 2 control current source 3; current sensor 4; filter 5 tuned to the reference current clock; comparison body 6; Executive body 7. The device operates as follows: The source of the control current 3 is applied to the primary network through an arcing coil 2 with a current of a non-industrial frequency. The current applied through the current sensor and filter 5 is supplied to one of the inputs of comparator 6, to the second input of which the reference signal from the control current source Zo is applied. When the stator winding closes to ground, the base of the applied current changes, due to which:; The output of the reference device receives a signal to the executive body 7 and the last one is triggered. If the frequency of the control current is taken to be, for example, If is the industrial frequency, then the current lo, the current flowing through the sensor and its phase can be expressed next (p | 9 (4 to 9115+ BRx .t arctg where G is the imposed control current reduced to the primary side of the arc-quenching coil;. RU4i3C; R is the contact resistance at the location of the circuit; C is the capacitance of the phase of the generator relative to the ground. Let it be in normal mode R JE, then I ,,., 0п 4 180 Г 3 With metallic closure on the ground at any point R O, then the current value and its phase are equal respectively to 1 IK. On the basis of this analysis, it can be concluded that for the received control current frequency, when the resistance in the circuit from R 00 to R O changes, The current flowing through the current sensor increases by a factor of three, and its phase changes by 180. These signs form the basis of the protection operation. The comparator body, made according to the phase-sensing scheme, compares the phase of the reference signal from the control current source to the phase of the superimposed current; received from the current sensor "In the proposed device, compared with the known circuit of both the reference signal and the signal from the current sensor, as well as when the control current source fails, the protection does not work, which increases the reliability of the protection" In addition , the exclusion of the connection of the protection with the measuring voltage transformer allows to simplify installation. protection, since there is no need to lay connecting wires. The protection is highly sensitive to transient resistance at the location of the circuit, which, when performing the simplest phase-sensitive circuit on transistors, is approximately 10 kΩ. Protection is characterized by the absence of a dead zone, the possibility of detecting a circuit on an unexcited oscillator. Claims An apparatus for protecting a generator in a block with a transformer against a ground fault, containing a source of control current of a non-industrial frequency, connected to the secondary winding of an arc-suppressing coil, current sensor, filter tuned to the frequency of the applied current, comparator and actuator, that, in order to increase reliability, simplify and improve protection parameters, the comparator is made according to a phase-sensitive circuit, one input of which is connected to the control current source, the second input to the current sensor through the filter and the output - to the executive body. Sources of information taken into account in the examination 1, USSR Author's Certificate No. itlOSn, cl. H 02 H 7/06, 197K 2. USSR author's certificate N 365004, cl. H 02 H 7/06, 1973.