SU754562A1 - Overvoltage limiting device - Google Patents

Description

The invention relates to overvoltage ayatite electrical equipment.

A device for limiting overvoltages using nonlinear resistors, some of which are shunted by spark gaps, is known [].

The closest to the present invention is a device for limiting overvoltages, containing series-connected resistors and connected in parallel parts of them, switching elements of the current-voltage characteristics of m.

However, bypassing (ie de-energizing) parts of series-connected resistors with spark gaps or a switching device overloads the remaining current resistors and. and voltage, which reduces the reliability of this device. The throughput capacity of nonlinear resistors depends on the number of current pulses, their duration, and very much power, ’cho (to a power of 3-5) on the amplitude of the acting 2

go current. Extremely high current values in the specified device affect only non-shunt resistors. The development of their bandwidth resource leads to a breakdown (burn-through) of them, and with them a breakdown of shunt resistors, which have exhausted only a small part of their resource. On the other hand, non-shunted resistors and their support insulation must be implemented. on the full voltage of the spark gap, acting on them in relatively rare cases of the operation of the shunt spark gaps. All this reduces the reliability of the specified device.

The aim of the invention is to improve the reliability of protection.

This goal is achieved by the fact that in the device for limiting overvoltage, containing series-connected resistors and switching elements of the current-voltage characteristics, the above-mentioned resistors are combined

W 7,545

in series-connected blocks with an honorable number of resistors each, and each switching element is shunt — every two adjacent block resistors.

FIG. 1 shows an overvoltage limiting device with three resistors in a block; in fig. 2 - a block of 'five resistors.

The device contains resistors 1,

> combined in blocks 2 with an odd number of resistors in the block, and switch elements 3 form in block 2 two 1 parallel branches, each switching element 3 being connected in parallel to two resistors I, to the points of connection between the two resistors 1 are connected to the switching elements 3 of another branch, and the extreme switching element is connected with one of the conclusions to the output of the resistor block. 20

Resistors 1 can be both nonlinear and linear, as switching elements 3, can be used currenting gaps (controlled or non-sharable, as well as high voltage across the arc), switching devices of the switch type or high-voltage etenlnye switched on. blocks.

In the open state of the elements of the exclusion 3, the resistors 1 are switched on, therefore, and the current through them is nonvestable. In case of overvoltages (in the case of unmanaged spark blunts), or before they occur (in other cases, the e-mail is given a signal to turn on the switching elements), the switching elements are closed and the resistors 1 are connected in parallel in the unit. The current through the protective device increases depending on the nonlinear resistor in toeffidienta toskolko times and surge effects _ύ givno limited. After the current passes through zero, the electrical strength of the switching elements is restored in the case of the controlled elements of the re-switching, the switches return to their original open state), and the eesistors will again be switched on sequentially.

If the resistors are non-linear, this device allows to increase the current by tens of times in the mode of limiting overvoltage compared to having a flush before switching. In this case, the current flowing through the resistor is somewhat

2 4

times less than in a device with a shunting part of the resistors, with the same level of overvoltage limiting. The consumption of bandwidth in this mode is ten times and hundreds of times less.

By increasing the number of resistors in the block, the required number of parallel branches is obtained. For example, with five resistors (FIG. 2), five parallel branches are formed after switching.

The advantages of the proposed device are especially important when using it to limit overvoltages in operating lines when the short-circuit is turned off. on the emergency. In this case, it is required to provide small values of resistance (less than 200 Ohm) at low voltages (below phase), therefore, it is advisable to use linear resistors with high heat resistance. The connection of resistors 1 by successive spark gaps (not shown in Figs. 1 and 2), accompanied by their switching from series to parallel-to-series, provides the current necessary for effectively limiting overvoltages. After a current break in the switching elements 3, the resistors 1 are automatically switched in series, and the current through them, in the case of repeated breakdown of successive gaps, decreases in the circuit of FIG. 1 to 9 times, - consequently, the regenerative voltage after repeated extinguishing of the arc at successive intervals will drop to a value that excludes their repeated breakdown. To obtain in a known way a similar (9 times) increase in current in the overvoltage limiting mode, it is necessary to bridge almost 90% of the resistors in parallel spark gaps, while the remaining current flows through the full current, which is 3 times higher than in the proposed device, and energy is 9 times more. In addition, each non-shunted element must be made to a nominal voltage of 3 times more than in the proposed device.

The reduction of the voltage restored on the protective apparatus after the passage of current through zero is accomplished by using spark gaps with high arc voltage. With

five

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Thus, the current from the switching device is displaced into resistors long before it crosses zero, which reduces the speed and amplitude of the recovering voltage already after the first 5 current zero crossing and increases the reliability of the device operation.

Application as switching devices of controlled spark gaps, switching devices of a switch type or controlled high-voltage valve blocks allows switching the current-voltage characteristics of the protective device before the occurrence of switching 15 overvoltages and thereby increasing the reliability of their limitation.

Limiting overvoltages by switching resistors from a series connection to a parallel-sequential connection allows for 3.5, etc. reduce the limiting currents through resistors and thereby reduce the consumption of bandwidth by tens and hundreds of times, and also reduce the voltage across the resistors by 3.5, etc., compared to the voltage across the unshunted

I

2

resistors in the famous. As a result

increases the reliability of the device limiting surge, increases

service life and dimensions of resistors decrease.

Claims (1)

Claim Device for limiting overvoltage, containing series-connected resistors and switching elements of current-voltage characteristics, characterized in that, in order to increase reliability, these resistors are combined into series-connected blocks with an odd number of resistors in each, and each switching element bypasses every two adjacent resistors flea.