SU1032486A1 - Process for warming up winding of power three-phase transformer - Google Patents

Abstract

The method of heating the windings of power three-phase transformers, in which current is passed through the windings, characterized in that, in order to reduce power consumption for heating by reducing the heating time, the short-circuit of the three phases of the secondary winding of the heated transformer alternately, at equal intervals of time, the winding of the windings of the three phases of the secondary transformer is applied. The winding is supplied with a three-phase voltage. (L with:

Description

The invention relates to the installation, operation and repair of three-phase power transformers, connected according to a star-star scheme with zero.

There is a known method of heating a power oil transformer by means of a vagreva winding with direct current, which consists in pre-forcing the heating of the transformer windings to an average temperature; the BO-IOS C atures are 2.5-3.5 times more than the nominal current. after which the transformer is heated while maintaining the temperature of the windings at the achieved level I.

Since during heating, direct current flows only through one of the windings and only it is a source of heat, and other windings, magnetic core, oil and tank are subject to heating, the force heating mode is used — 2.5-3 times a current flows through the winding 5 times more than the nominal, which makes it very likely that the excited winding will fail. To supply the excited winding as a heat source, a source of adjustable nonstandard voltages and a rectifier device are required, which significantly increases the cost of heating the aforementioned transistor. In addition, this method is unacceptable for drying transformers, since after drying is finished, the oil becomes non-beneficial for further operation.

Closest to the proposed. is a method of heating or drying a zero sequence. In this method, a single-phase current is passed through all the phases of one of the windings, which heats this winding and induces an induction loss of the magnetic core, and the tank, which causes the magnetic core and the tank 12 to warm up.

This method has a relatively long warm-up or drying time and increased power consumption. To heat or dry, a source of non-standard single-phase voltages is needed that works with a low power factor (cos f also, when warming up "G1I drying power transformers in this way, creates a noticeable symmetry for mains supply.

The purpose of the invention is to reduce energy consumption for heating, reducing the time for heating or drying three-phase power transformers.

The goal is achieved by the method of heating the windings of three-phase power transformers at which current is passed through the windings, each of the three phases of the secondary winding of the heated transformer alternately, at equal intervals of time is short-circuited, and the three-phase voltage is applied to the primary winding.

The drawing shows a diagram explaining the method.

A device for heating a three-phase power transformer consists of a three-phase supply transformer 1, the secondary winding of which is connected to the primary winding of a heated transformer 2 connected in a star-star to zero circuit, switch 3 connected to the secondary winding of the heated transformer.

The method is carried out as follows.

After turning on the network device

and one of the poles of the switch 3 through the windings of the heated transformer 2 currents flow, indicated by the scheme. The diagram also shows the directions of the magnetizing forces.

(NS) rods formed by currents. As can be seen from the diagram, the current in the phase L of the primary winding of the transformer 2 is twice the current in phases B and C. In the secondary winding of the transformer

2 current flows only in the short-circuited phase a. In order to achieve uniform heating of the windings, it is necessary at regular intervals to transfer the short circuit of 1C phases of the secondary winding to

another one. The time after which the circuit is transferred from one phase to another depends on the power of the transformer 3 and is expressed in shares of the constant heating time of the transformer. From the Vidno scheme, what is N.S. rods can be represented by the following formulas:

1 to

21k

, P

FA% -r i V-l iV-TK

one

where W. and W are, respectively, the number of turns in the phases of the primary and secondary windings.

Taking into account that the transformation coefficient is equal to k Wi,

... wj

Equations (1) can be given the following form:

-4K% l a-VK iH i i

From equations (2) it follows that the magnetizing forces of all the rods are equal in magnitude and phase.

According to the proposed method, in phase A, heat is released four times more than in the known method. Moreover, according to the proposed method, heat is released in phase a, in the same way, heat is not released at all in the phases of the secondary winding, because the current in the secondary the winding is not leak - g. Due to the increased heat generation in. The windings located on the rod with a short-circuited phase accelerate the process of drying or heating the transformer and reduce the power consumption. i Instead of a single-phase source of non-standard voltages, a serial power transformer can be used. The overheating of the short-circuited phase and the low voltage winding will not occur, since the current is even

.

less than rated current. The recommended drying current is determined by the following formula:

I - c

(3)

to eo.as

GDG LA Nominal phase current of the dried transformer, A;

5c - rated power of the dried transformer,

kva.

Thus, the proposed method of drying or heating three-phase 15 power transformers in all respects is better known.

b

Claims (1)

METHOD FOR HEATING THE WINDING OF POWER THREE-PHASE TRANSFORMERS, in which current is passed through the windings, characterized in that, in order to reduce the energy consumption for heating by reducing the heating time, each of the three phases of the secondary winding of the heated transformer is short-circuited, at regular intervals, and a three-phase voltage is applied to the primary winding.