RU1818657C - Method for protection of phase-regulating transformer - Google Patents

Abstract

The invention relates to electrical engineering, namely to the relay protection of high-voltage phase-shifting transformers. Summary of the invention: in order to increase the sensitivity in the method, a signal is generated proportional to the difference in active powers flowing along the primary and secondary windings of the phase-shifting transformer, and a command is generated to disconnect it from the network, if the received signal exceeds the protection setting. 1 ill.

Description

The invention relates to the field of electrical engineering, in particular to methods for protecting transformer windings from all types of damage.

The aim of the invention is to increase the sensitivity of protection of a phase-shifting transformer .. This allows you to detect and turn off a damaged transformer at an early stage of an accident, which maintains its maintainability and reduces the time and cost of repair.

In order to achieve the goal in a method of protecting a phase-shifting transformer based on measuring currents and voltages of the primary and secondary windings, determining from the measured values of the capacities flowing along the primary and secondary windings, and generating a command to turn off the phase-shifting transformer in case the difference in the indicated powers exceeds the specified set point, the active power component is further determined.

h (tHim -sin cot; Ui (tHJim -sin (ftrt + p); I2 (t) l2m -sin (fwt ± 45; U2 (t) U2m -Sin (Wt ± 4 + 0z) J (2)

where Hm, Uim and l2m, Lkm are the amplitude values of currents and voltages on the primary and secondary windings of the PSF, respectively;

H1 is the angle between the primary and secondary voltages (currents);

p is the angle between the primary current and the primary voltage;

(pi- angle between the secondary current and secondary voltage.

From the measured values by known methods, signals are generated that are proportional to the active power flowing along the primary and secondary windings of the PSF:

, 5xUlm HtnCOS p, 1 .5xU2m -l2mCOS J (3)

O) WITH

with

00

00

about eating VI

Then the difference of active powers is determined

AP Pi-P2 (4) and compare it with the setting, in case of exceeding which they form a signal to disconnect the PSF from the network.

The essence of the method is explained by the following modes of operation of the phase-shifting transformer.

In normal mode, with a good PSF in the entire range of the angle Ч (for example, from -40 to + 60 °). and the secondary voltage module (for example, from 0.9 to 1.2 nominal), the active power flows in the primary and secondary windings are almost equal, since the active losses are small and make up no more than 1% of the total rated power. In this case, the difference between the active powers does not exceed the pickup setting and the signal to switch off the PSF is not generated.

If damage occurs in any of the PT windings, a sharp increase occurs.

active

losses

.

.

mainly due to losses in short-circuited turns that are active. In this case, the power balance in the PSF windings is violated, since the value of the active power of the primary winding increases and the secondary decreases.

If the difference of active powers D P exceeds the protection operation setting, a signal will be generated to disconnect the PSF from the network.

When the PSF is switched to idle, a magnetizing current surge may occur due to saturation of the transformer magnetic circuit. If the PSF is operational in this case, then its input impedance is almost purely inductive (resistance of the magnetizing branch), therefore the value of AR is close to zero.

If in the process of switching on the PSF under voltage a winding short circuit occurs in one of its windings, due to a significant increase in active losses (not less than an order of magnitude) compared to the switching mode of a working PSF, the value of the power unbalance will exceed the setting and a signal will be generated by disconnection of the transformer from the network.

With external damage, the difference in active powers in the primary and secondary windings is determined by the active losses in these windings and depends on the short-circuit current,

For powerful transformers (including PSF), these losses at the maximum external short-circuit current do not exceed unity 5

U 15 20

25

thirty

35 40

45 50

55

Nice percent of full rated power.

In order to prevent the protection from tripping in this mode, it is necessary to select the tripping set Pst APi, where PI is the active power imbalance in the maximum external short-circuit mode.

In case of an external short circuit with the imposition of a coil short circuit in one of the windings of the PSF, the protection will work similarly to the case described above when a short circuit occurs in the load mode.

A block diagram of a device that implements the proposed method is shown in the drawing.

The device comprises a phase-shifting transformer 1, equipped on both sides with current transformers 2, 3 and voltage transformers 4, 5, the outputs of which are connected to the inputs of the corresponding first b and second 7 active power sensors. From the output of sensors b and 7, voltages proportional to the active power released on the primary and secondary windings of the PSF are applied to the corresponding inputs of comparator 8, which is triggered if the difference of the input signals exceeds its setting. This causes the output unit 9 to operate disconnection of switches 10 and 11 of the PSF from the network 12 and 13.

In the normal mode, the values of the active power on the primary and secondary windings are equal and the condition of the triggered comparison unit is not satisfied.

In the event of damage to any of the PSF windings, significant losses of active power occur, as a result of which the balance in the comparator 8 is disturbed, which leads to its operation and the output unit 9.

The proposed method allows to protect the phase-shifting transformer with a sensitivity exceeding the sensitivity of the known shields of a similar purpose and independent of the inrush of the magnetization current, as well as from changes in the angle of rotation WH of the PSF transformation coefficient.

The economic efficiency of the invention lies in the fact that its use will increase the service life of phase-shifting transformers by detecting faults in the windings at the initial stage of their occurrence. This preserves the maintainability of the PSF and significantly reduces the time and cost of their repair.

Claims (1)

SUMMARY OF THE INVENTION A method for protecting a phase-shifting transformer based on measuring currents and voltages of the primary and secondary windings, determining from the measured values of capacities flowing along the primary and secondary windings, and forming a command to turn off the phase-shifting transformer in case the difference in the indicated capacities exceeds a predetermined setting distinguishing - so that, in order to increase the sensitivity of the protection, the active component of the power is determined. Gdh 2 5 I / 3