Method for regulating the voltage of a transformer

Abstract

The invention relates to a method for regulating the voltage of a transformer (1) having different winding taps (3). The problem addressed by the invention is that of providing a method with which different load flow directions can be regulated with conventional transformers (1) and voltage regulators (7) in order to ensure a safe and reliable supply of voltage. The general inventive concept consists in determining, using a method in which a quadrant system (11) is used, the phase angle of the conduction current (I) and thus the load flow direction, thereby preventing deviation from the voltage range as a result of power input that is too high, by controlling the load tap changer (4).

Claims

1. A method for voltage regulation of a transformer with different winding taps and a voltage regulator, comprising the steps of: initially determining the conduction current present at the transformer and simultaneously ascertaining the instantaneous voltage present at the transformer; using a quadrant system in which a first quadrant and a second quadrant show the phase position of the conduction current from generators to the transformer and a third quadrant and a fourth quadrant show the phase position of the conduction current from the transformer to the consumers; and if the phase position of the conduction current is detected in the third quadrant or in the fourth quadrant of the voltage regulator, raising an instantaneous voltage to a target value range or if the phase position of the conduction current is detected in the first quadrant or in the second quadrant of the voltage regulator, lowering an instantaneous voltage to a target value range.

2. The method for voltage regulation according to claim 1, further comprising the step, when the instantaneous voltage is raised to the target value range, of: switching off windings of the tap winding on the primary side of the transformer.

3. The method for voltage regulating according to claim 1, further comprising the step, when the instantaneous voltage is lowered to the target value range, of switching on windings of the tap winding on the primary side of the transformer.

Description

(1) The method according to the invention shall be explained in more detail in the following by way of an embodiment.

(2) FIG. 1 shows a schematic view of a transformer with necessary means for reliable voltage supply with different load flow directions;

(3) FIG. 2 shows a quadrant system according to the invention;

(4) FIG. 3 shows a diagram in which a voltage plot runs in the target value range; and

(5) FIG. 4 shows a flow chart according to the invention for the method according to the invention.

(6) A transformer 1 with a tap winding 2 and different winding taps 3 is depicted in FIG. 1. This has a primary side P and a secondary side S. The winding taps 3 are switched on or switched off by an on-load tap changer 4. The switching-off and switching-on can, however, be realized by any means such as, for example, load selectors, tap changers, etc. The actuation of the on-load tap changer 4 takes place by way of a motor drive 5. This motor drive 5 is controlled by a control 6 and a voltage regulator 7 integrated therein. The voltage regulator 7 detects, at an input point 8, a conduction current I in a line 9 connecting the transformer 1 with a consumer/generator 10. In that case there can obviously also be a plurality of consumers/generators. In addition, the voltage regulator 7 detects a voltage U present between the transformer 1 and the consumers/generators 10.

(7) The quadrant system 11 depicted in FIG. 2 consists of an X-axis X and a Y-axis Y that delimit a first quadrant 12, a second quadrant 13, a third quadrant 14 and a fourth quadrant 15. The actual part of the conduction current I, which is determined by the load of the consumer/generator and the lines, is recorded on the X-axis. The Y-axis represents the imaginary part of the conduction current I. The angle between the vector, which represents the conduction current I, and the X-axis reflects the phase displacement. If the angle adopts a value between 0 and +180 the conduction current I trails the voltage U, i.e. an inductive generator/consumer is connected. If the angle adopts a value between 0 and 180, the conduction current I leads the voltage U, i.e. a capacitive generator/consumer is connected.

(8) In the prior art it was always assumed that the conduction current I, starting from a consumer directional arrow system, was to be found in the third quadrant 14 or fourth quadrant 15, i.e. different inductive consumers were connected with capacitive or resistive components on the low voltage side.

(9) As can be seen in FIG. 3, a voltage drop can move within a target value range 16, which is bounded by an upper voltage limit value G1 and a lower voltage limit value G2, without intervention by the voltage regulator 7 being required. The voltage continuously drops over the length of a line L to the consumers. If the upper voltage limit value G1 or the lower voltage limit value G2 is exceeded intervention by the voltage regulator 7 is required. Otherwise, the voltage drop can be kept within the upper voltage limit value G1 and the lower voltage limit value G2 by switching-on one or more windings of a tapped winding 4 by the on-load tap changer 2 on the primary side P of the transformer 1. The voltage drop lies within the target value range 16 (voltage band).

(10) Since, now, not only consumers, but also generators can be connected on the secondary side S of the transformer 1 it is necessary to be able to reproduce this. These generators are similarly reproduced by the conduction current I. According to the invention it was recognized for the first time that the generators that are similarly represented by the phase positions of the conduction current I, areby contrast to the consumersreproduced in the first and second quadrants 12, 13. These can similarly comprise inductive or capacitive components.

(11) The regulating method is illustrated in FIG. 4 as a flow chart. An input of the power parameters of the plant is carried out in the first step 20. By plant there is to be understood, in accordance with the invention, the transformer 1, the on-load tap changer 4 and the lines associated therewith. Also belonging thereto are technical characteristic variables of the transformer 1, the on-load tap changer 4 and the line lengths to the consumers/generators. This method step is usually used in all is regulating methods known from the prior art.

(12) In operation, the second step then takes place, namely the measurement 30 and 40 of, respectively, the conduction current I and the voltage U at the transformer 1. These data are ultimately evaluated by the voltage regulator 7 and used for the purpose of carrying out determination 50 of the position of the conduction current I with the associated phase position in the quadrant system explained in FIG. 2.

(13) If the vector of the conduction current I is now in one of the consumer quadrants, thus in the third or fourth quadrant 14 or 15, an increase 60 in the voltage value U.sub.s of the voltage regulator takes place. This has the consequence that windings, which are on the primary voltage side, of the tap winding of the transformer 1 are switched off; the translation ratio between primary windings and secondary windings is lower. A leveling 70 of the voltage drop as a consequence of a high consumption thus takes place.

(14) If the conduction current is in the generator quadrants, thus in the first or second quadrant 12 or 13, a reduction 80 in the target value of the voltage regulator takes place. Windings of the tapped winding are switched on the primary voltage side; the translation ratio between primary windings and secondary windings is higher. As a result, a leveling 90 of the voltage increase as a consequence of a high power feed is produced. The procedure is filed as an algorithm in a fixed value memory in the voltage regulator.

(15) An advantage of this method is the fundamental difference between consumer and generator on the secondary side of a transformer 1. Ascertaining whether power is fed in or consumed on the secondary side prevents, by adaptation of the transforming ratio of the transformer, a voltage excess, i.e. an exceeding of the limit values of the voltage band 16, from being caused by a high feed power.

(16) A further advantage of this method is that no additional apparatus has to be installed in order to detect and appropriately level the changing load flow. It is possible by the method to use the existing components, for example transformer, voltage regulator, etc.

REFERENCE NUMERAL LIST

(17) 1 transformer

(18) 2 tapped winding

(19) 3 winding taps

(20) 4 on-load tap changer

(21) 5 motor drive

(22) 6 control

(23) 7 voltage regulator

(24) 8 input point

(25) 9 line

(26) 10 consumer/generator

(27) 11 quadrant system

(28) 12 first quadrant

(29) 13 second quadrant

(30) 14 third quadrant

(31) 15 fourth quadrant

(32) 16 target value range of the voltage

(33) 20 input of the power parameters

(34) 30 measurement of the conduction current at the transformer

(35) 40 measurement of the voltage at the transformer

(36) 50 determination of the phase position of the flow indicator (conduction current) in the quadrant system

(37) 60 increase in the target value of the voltage regulator

(38) 70 leveling of the voltage drop as a consequence of high consumption

(39) 80 lowering of the voltage value of the voltage regulator

(40) 90 leveling of the excess voltage as a consequence of high feed power

(41) G1 upper voltage limit value

(42) G2 lower voltage limit value

(43) I conduction current

(44) P primary side

(45) S secondary side

(46) U voltage

(47) angle