SU866643A2 - Device for quick-action compensation for earthing capacitive current in ac network - Google Patents

Description

the network 6, the voltage selection unit 7, the additional capacitor 8 and the additional winding 9 of the throttle 1. Capacitors 2 are connected between the zero point of the network and the ground via controlled keys 3. The inputs of the controlled keys 3 are connected to the outputs of the key control unit 4. Block inputs

, 4 key controls are connected individually by a chain with an analog-digital output. Converter 5, which is designed to convert a constant voltage U, received at its input, into a digital binary code, in which at each individual

one of two sigffs is formed

or

cash:

The output of the voltage selection unit 7, through the capacitor 8 is connected to the additional winding 9 of the throttle 1. With the help of the voltage selection unit 7, the additional winding 9 is transferred to the network phase leading ahead of the damaged network phase.

The main choke 1 with capacitors 2 provides compensation for the capacitive component of the earth fault current. In case the network capacity 6 is equal to zero, the input voltage of the analog-digital converter 5 is supplied with a control voltage U of such a magnitude that at its individual outputs a whitefish is formed as a result of all controls

Key 3 will be opened. When the network capacity is switched on, the compensation detuning increases s cfopOHy undercompensation and, for the adjustment, it should decrease the control voltage Oy at the input of the analog-digital converter, which will close individual controlled keys, and, consequently, reduce the detuning compensation . Selectively switching on or off capacitors 2 provides an analog-to-digital converter.

The required accuracy of the compensation adjustment is achieved by selecting the appropriate number of m capacitor 2, the capacity of which is selected from the condition

-Y L, IK

where is the current of the i-ro capacitor; 1 c, - current drossel; i is the serial number of the capacitor.

, when p 7 residual detuning compensation will not exceed

V t-fr 10 O, 7 8%

The compensation of the active component of the earth fault current is as follows: o6Da3ONFi

When one phase is closed on, the ground (for example, phase A) to the additional winding 9 of the throttles 1 through the voltage selection unit 7 and the capacitor 8 is supplied with the leading phase voltage VP, which provides the opposite direction of the input electromotive force relative to the active component of the short circuit current the earth.

The resistance at the terminals of the additional winding of the throttles, introduced from the primary circuit during its resonant tuning with the network capacity, is active and equal to

- - L

cut g- g. g v) uV

where K is the transformation ratio

between the additional and main windings of the throttles;

5- conduction losses in steel throttles;

active resistance hanks drossel;

L inductance winding drossel;

9 conductivity of active losses in network isolation.

To fully compensate for the potential in the damaged phase of the network relative to the earth, i.e. in order to fully compensate the current to the ground, it is necessary that the voltage supplied from the outside to the additional winding of the throttle transforms into a zero-sequence network circuit in magnitude and direction equal to the source emf. The nominal voltage of the additional winding of the choke is equal to 110 V. Since the transformation ratio CT is chosen equal to

Kt 0,5 Kt.-tr,

where Kt.tr - coefficient of transformation. mation between low and

the high voltage of the voltage to achieve full compensation requires that the capacitance value of the additional capacitor through which the phase secondary voltage of the network (220 V) is supplied to the additional winding of the throttle is equal to Y1 Rp.m. -,

... -GGK

e-vi- e-.

"

The magnitude of g, r, and L throttles does not change during operation; active losses in the cable network isolation vary only slightly with time and therefore are also assumed to be different, therefore the value of X will also be constant; It is installed once during adjustment and is not adjustable during operation. .

Claims (1)

Across Kira insulation of the cable network, some adjustment of the input voltage may be required, which is achieved by a conventional rheostat connected in parallel with an additional winding of 110 V drossel. If during the operation of the network, in order to fully compensate for the current of the secondary charge protection system, it is required to increase the previously established resistance value of the rheostat, this means that the resulting resistance of the network insulation decreased as compared with the previous level and the most; Thus, the periodic adjustment of the resistance of the rheostat with the registration of its value allows, along the way, to carry out preventive monitoring of the network isolation level. Such an adjustment may be required no more than once a year, or even less, depending on the rate of aging of the insulation. Ferroresonance phenomena in this device do not occur, since there is no nonlinear inductive resistance. The performance of the compensation setting is ensured by the fact that thyristors are used for the setting of the capacitor at the rate, as well as in the voltage selection block. Thus, the proposed device extends the functionality of the capacitive compensation system of the locking circuit to aeMnsti in which an unrepairable choke is used, and the resonant compensation setting is provided by adjusting the capacitance 1 of the capacitors connected in parallel with this choke. In the proposed scheme, the active component of the ground-to-ground current is also automatically compensated. In the course of the network operation and changing its capacity, it is not necessary to adjust any circuit parameters to achieve this additional compensation. Since the parameters of the compensating throttle remain unchanged. Compensation of the capacitive and active components of the earth fault current reduces the residual current in the tapping point to the level of higher harmonics, which contributes to the self-extinguishing of the electric arc with the electric cable and prevents significant damage to the insulation of the cable from the thermal effect of the arc. As a result, the reliability of power supply to consumers in high-voltage compensated electrical networks and the maintenance of electrical installations are increased. The invention is a device for high-speed compensation of capacitive current closure of the earth in an AC network by author. St. 748621, distinguished by the fact that, in order to extend the functionality by compensating for the active component of the single-phase ground fault current, it is additionally equipped with J clutches connected by the voltage selector, an additional capacitor and an additional winding of chokes, and the input of the selector the voltage is connected to the mains phases. : Sources of information taken into account in the examination 1. Copyright certificate USSR 748621, cl. H 02 H 9/08, 1978. K B t;