SU1599815A1 - Method and apparatus for electrodynamic tests of power transformers - Google Patents

Abstract

The invention relates to instrumentation engineering and can be used for electrodynamic testing of power transformers. The purpose of the invention is to expand the scope of control. The principle of operation of the device lies in the fact that the disconnection of the short circuit phase, through which the transformer under test is connected, occurs at certain points in time calculated by the logic unit, thereby reducing voltage surges. The device contains a powerful three-phase power supply system 1, a three-phase protection switch 2, a test transformer 3 with input 4 and output 5 windings, a three-phase short connector 6 and a capacitor 7 battery, three current transformers 8, 9, 10 and secondary transformers 11 with primary 12 and secondary 13 windings, logic block 14, three transformers 15, 16, 17 voltages. 2 sp.f-ly, 1 ill.

Description

The invention relates to electrical engineering and can be used for electrodynamic testing of high-voltage power transformers (autotransformers) and their full-size models in the conditions of a network stand and with the help of synchronous shock alternators.

The purpose of the invention is to expand the scope by implementing electrodynamic tests of high-power and super-power transformers in three-phase and single-phase modes.

The essence of the invention is that after applying a voltage to a test transformer and applying voltage to it through a capacitor bypass of a short-circuit, it is disconnected at times determined according to the equation

sinto0; + s; - arctg)

rj

- 3in (- arctg Shch.1-)

exp (

"211

9;

(one)

- (Ei) Li :(

4СУс + (co C; ZLj - 1)

0,

de 0;

(I;

SLj and 2vj

/-one , "

shutdown angle of the i-th phase switching angle of the i-th phase of the safety switch;

total inductive and active components of the short-circuit impedance of the power test circuit; i-phase capacitance of a three-phase capacitor bank.

0

five

0

five

0

five

0

five

Equation (I) expresses the condition of the minimum duration of the transitional process of connecting capacitance C by disconnecting the corresponding phase of the short circuit. An additional condition is the selection of those angles 9 ,, at which the current in the transformer under test does not differ from the nearest maximum amplitude value of the test current, more than ± 5%. As shown by calculations performed on the digital computer, in the case of testing a transformer with a power of 400 MVA, the difference in the transient test current does not exceed ± 10% of the normalized test current. This value is acceptable from the point of view of the standard for electrodynamic tests (GOST 20243-74).

The drawing shows a block diagram of a device for implementing the proposed method.

The device contains a powerful three-phase power supply system 1, a three-phase protection switch 2, a test transformer 3, input 4 and output 5 windings of which are connected by a star, and common points are grounded, a three-phase short-circuit b, three-phase capacitor 8.9 and 10 current, three-phase test transformer 1 1, primary 12 and secondary 13 windings of which are connected by a star, and common points are grounded, logic block 14 and three transformers 15, 16 and 17 voltage.

Power System Phase 1 via a three-phase switch. 2 is connected to the input windings 4 of the test transformer 3, whose input windings 5 are connected via three-phase short circuit breaker b and a three-phase capacitor connected in parallel

battery 7 with the primary windings 12 of the three-phase transformer under test 1 1, the output, the windings I 3 of which are short-circuited. The first, second and third inputs of logic unit 14 are connected via voltage transformers 15, 16 and 17, respectively, to each phase of power system 1, the fourth, fifth and sixth inputs of logic unit 14 are connected to current transformers 8, 9, and 10, which are connected respectively to phases between the primary winding 12 of the test transformer 11 and the capacitor battery 7, and the output is connected to the control input of the short circuit 6,

The device works as follows.

The safety switch 2 is turned on, thereby applying voltage to the test transformer 3 and, through the previously switched-on phases, a short-circuit switch 6 to the test transformer. Then, the phases of the shorting switch 6 are turned off at times & different for each phase and defined by the transcendental equation (1).

Dp simplify the process of electrodynamic testing by AB-. Tomatization of the choice of the moment when each phase of the short-circuit switch 6 is turned off in logic block 14, the angle L is determined; switching on the i-th phase of the protection switch 2 by comparing the signals from the current transformers 8, 9 and 10 and the voltage transformers 15, 16 and 17, determines the required shutdown angle of the i-th phase of the short circuit 6 in accordance with the above formula, then forms and a signal is output to the control system of the short circuit 6 with a lead time equal to the time of the actual disconnection of the i-th phase of the short circuit 6.

If the resulting form of the test current curve has more than 10% deviation compared to the normalized test current curve, in order to reduce the transient time in series with the capacitor battery, the power circuit additionally includes an active resistance whose value exceeds the total active component of the short circuit impedance of the power circuit

and allows you to increase the damping factor by the required amount.

The proposed device allows additional testing of those types of transformers that cannot be tested with a prototype device due to the limited test capacity of the test bench.

Claims (2)

1. The method of electrodynamic testing of power transformers, which supply voltage to the measuring transformer, the voltage from which is fed through the short-circuit breaker to the transformer under test, and the subsequent control of the parameters of this transformer, characterized in that , the supply of voltage is conducted through a capacitor, shunt-in. a short-circuit switch, and the shutdown of each phase of the short-circuit switch occurs at times determined according to the equation thirty sin (C00; + o; - arctg Jtl-) - sin (Di; - arctg) X exp COZL .- 0; ; iJSI  y.ciji (p  + (Q CiZL: 1) 0 5 five 0 where 9i 2r off angle of the i-th phase of the short circuit; 0 (; - the turn-on angle of the i-th phase 3 Protect the new switch off j e and J total inductive and active resistances of the short circuit of the power circuit of the i-th phase; WITH; - capacitance of the i-th phase of the capacitor battery; . WITH - the number of turns in the winding. 2. Device for electrodynamic testing of power transformers containing a powerful source of three-phase alternating voltage and connected in series with it a protective switch, a test intermediate transformer, the windings of which are connected in star with the depth 1599815 neutral neutral, short-circuit aza a short-circuit, input a breaker and a three-phase test subject connected to the output of the trans- the transformer, the secondary winding of the co-formator of the current of the transformer under test is shorted, it has a transformer and voltage transformers Now with the aim of expanding the phases of the pit of the source, and the output is with the use of the application area, in the absence of control of the short circuit, an additional three-phase additional three-phase condensation capacitor battery is added, the logic battery is connected in parallel The block for the selection of the disconnection is turned off each time.