SU892572A1 - Device for earthing transformer neutral wire - Google Patents

Description

one

The invention relates to a jc high-voltage electrical network and relates to the earthing of a transformer neutral. tori ..

 AC mains can operate with insulated and deaf-grounded neutrals of transformers.

The disadvantages of the operation mode of networks with insulated transformer neutrals are the somewhat overwhelmed cost of transformers, the possible occurrence of dangerous ferroresonance processes, which can lead to damage to the electrical system. In addition, the isolation level of high voltage networks and equipment should be an order of magnitude higher than in systems with solidly earthed neutrals of transformers.

These | deficiencies disappear when the neutral ground of the transformer is deafened.

However, according to the sensitivity conditions of the relay protection of 110 kV networks and above, it is necessary to allow the neutral to be earthed more than that of one of the transformers. Feeding through a branch from one line

This grounding mode has the disadvantage that when disconnected

a damaged transformer with a grounded neutral; there is a probability of overvoltage on the neutrals of other transformers connected to this

 line, in the event of a closure on it on the ground. ; With an increase in the power of power systems, an increase in the number of transformers with deaf-grounded neutrals leads

 to the growth of short-hardened currents on the ground, and their magnitude may exceed three-phase short-circuit currents, respectively, necessitates amplification, modernization

15 or even replacements of electrical equipment.

A device for earthing a transformer neutral is known, comprising a resistor and a discharge switch tl included in the neutral.

20

The closest in technical essence to the present invention is a device for grounding a transformer neutral in high-voltage AC networks, containing a discharge, the electrodes of which are connected: one to the neutral and the second to the ground; capacitor, surge and resistor 2.

However, the known devices do not allow a complex solution of the problem, reducing the current level of a short

to protect the insulation from impulse and switching overvoltages, to exclude the possibility of occurrence of ferroresonant processes in normal and emergency operation of the power system, respectively, with isolated and deaf-grounded neutrals of transformers.

In particular, the device (2 does not ensure the normal operation of power transformers (autotransformers) in the network during the ice melting, since the flow of direct current in the transformer neutral leads to additional biasing and other junk; n. Phenomena. Connected to the transformer line, for example Reactors are also exposed to the harmful effects of direct current, which can damage them.

The aim of the invention is to increase the efficiency of short-circuit current level coordination on the ground and protection of the insulation against impulse and co-induced IM overvoltages and exclusion of ferro-resonance processes in normal 1 x and emergency modes of the power system, respectively, with insulated and deaf ground neutral mi transformers.

This goal is achieved by the fact that a device for earthing a transformer neutral in high-voltage AC networks contains a discharge, one electrode of which is connected to the neutral, and the second to set / me, the reactor, one output of which is connected to the neutral, and the second to seg / ne, and the resistor, is equipped with a capacitor, one output of which is connected to the neutral, and the second to the second / output of the reactor; The arrester is supplied with a third electrode, connected to the junction point of the capacitor and the reactor, while the resistor is connected in parallel to the reactor.

FIG. 1 and 2 are schematic diagrams of the device.

The device is made in the neutral of the transformer 1 connected in series with the capacitance 2 and the reactor 3, shunted by the discharge voltage 4 with an additional ignition by means of the auxiliary electrode 5, is switched on. between the reactor and tank 2, with active resistance 6 (for example / linear or non-linear) connected in parallel with reactor 3.

Pa figs. 2 shows an embodiment of the grounding device of the neutral booster transformer 1 connected to an autotransformer 7.

Under normal operation of the system, the voltage on the neutral of the Transformer Math 1 is absent, and consequently, on the circuit, capacitance 2 — reactor 2, i.e. neutral will be isolated.

When asymmetric modes occur, a voltage appears on the reactor, and consequently, on the auxiliary electrode 5j, if its value is sufficient to break through the gap of the arrester 4, it triggers and thus the neutral of the transformer is grounded. The ignition voltage of the surge voltage 4 can, for example, be regulated by changing the number of turns of the reactor inductance 3. This is achieved by adjusting the response time of the surge voltage 4, allowing it to be adjusted so that, when a voltage is generated on the inductance of the reactor 3, the neutral of the transformer is earthed asymmetric mode / te or short circuit in the network. Voltage displacement does not occur on the neutrals of the transformers, i.e. the system works as it is

with an earthed neutral in emergency mode.

If, however, some asymmetry is allowed in the system in normal mode, then the glitter can be configured so that, with acceptable asymmetry in the network, it does not work. : When falling onto a transformer you are: low-frequency or pulsed waves; i due to thunderstorm or commutation-g. overvoltages, the active resistance reduces the amplitude of these overvoltages to a safe value and eliminates the occurrence of ferroresonant processes on the transformer neutral in normal and emergency operation modes.

Thus, an automatic change of the operating mode of the transformer neutral is provided, increasing the level coordination efficiency. short zagykani on the ground and zazity isolation from pulsed and commutation overvoltages, and excluding ferroresonance processes in normal and emergency operation of the power system, respectively, with isolated and deaf-grounded neutrals of transformers.

Claims (2)

Invention Formula The device is for earthing the neutral of the transformer in high-voltage networks of alternating current, containing a discharge electrode, one electrode of which is connected to the neutral, and the second to earth, the reactor, one KOTOpt terminal, which is connected to earth, and a resistor, different in that In order to improve the efficiency of the device in emergency modes and eliminate ferroresonant processes in the normal and emergency mode of the power system, it is equipped with a capacitor, one output of which is connected to the neutral of the transformer, and the second to the second output Torah; The arrester is equipped with a third electrode connected to the junction point of the capacitor and the reactor, while the resistor is connected in parallel to the reactor. ; Sources of information taken into account in the examination ; 1.Particle neutral grounding in electrical systems through a resistor. Collection of ed. C.N. Djuvarly. Baku, Elm, 1976, p. 192, fig. 2 2. USSR author's certificate 517103, cl. And 02 H 9/02, 1974.