SU775815A1 - Device for protecting capacitor battery-higher harmonics filter from stable and alternating short-circuitings - Google Patents

Description

The invention relates to the field; relay protection of capacitor banks is a relay protection device against short circuits of 5 rows of a grounded capacitor battery filter of higher harmonics connected to the network with an ungrounded neutral in parallel with similar 1/1 capacitor batteries with a total power exceeding the power of the protected battery.

Capacitor filter batteries are intended for power converter stations and j DC inserts to filter the higher harmonics generated by the converters and as sources of reactive power.

Known protection capacitor JQ batteries: longitudinal differential protection of consecutive rows of capacitors and longitudinal differential protection of the battery phase.

To perform these protections 25, the installation of additional expensive equipment (voltage transformers), as well as new equipment (a complex signal transmission system for the first protection.) Q

and a special differential relay with a high-harmonic filter - for the second), not yet mastered by industry. This entails the complexity of the implementation of these protections.

These protections are intended for use in capacitor banks connected in a known manner.

An alternating current network operating with an ungrounded neutral is connected in parallel with a 1.2 p battery. When closing the circuit

in phase A of a capacitor bank, for example, the 1st, a zero sequence current appears, which spreads over the phases of the remaining capacitor batteries 2, ... n, (the distribution of the zero sequence current is described under the condition that all batteries have the same power).

If the power of a single capacitor battery is several times less than the total power of the capacitor batteries connected to the buses, then the zero sequence current of the capacitor battery with internal faults is several times higher than the current with external damages.

The nature of the distribution of the zero-sequence currents in the considered capacitor-filter-battery connection circuit when the series is closed allows the application of protection that reacts to the zero-sequence current.

A known zero-sequence current protection is made on a current relay connected to the geometric sum of three-phase current transformer currents (zero-sequence current filter), and reacting with or without time delay for damage accompanied by zero-sequence currents.

Considered damage to capacitor batteries is characterized by the unstable nature of the arc. In addition, there are high harmonic components in the battery currents that enter the relay. This sigicite does not respond to unstable series and it is also not sensitive enough, since it must be chopped up to detun unbalance the higher harmonics from the current.

In order to eliminate the indicated deficiencies in a device for protection against short-circuiting and intermittent short-circuits of a grounded capacitor battery-filter of higher harmonics in a network with grounded neutrons, containing a zero-sequence current filter and a time element connected in series with the time element and the actuator, additionally a high-end filtering filter is introduced, a cycle counter, with the filter of higher hectares {lonic is connected between the filter of zero-sequence currents and and Measuring current body, and the cycle counter is connected in parallel to the time element.

This protection device uses a current relay supplemented by a high harmonic current filter as a measuring unit, which makes it possible to increase the sensitivity of protection without retaining the measuring organ from unbalance currents of higher harmonics, which appears in transients in case of a breakdown of the converter bridges. To tune off transients (charge, discharge) in a capacitor battery when d.e. In the AC network protection is entered into the whole time. The scheme provides for triggering protection when a row is bending, which is of an unstable nature with multiple attenuation and arc recovery. This is ensured by the presence of a cycle counter in the protection circuit.

The number of cycles through which the protection acts on the trip (or signal) is selected on the basis of the detuning from the transients in the capacitor battery at short circuit, in the AC network and unsuccessful reclosure.

The drawing shows a block diagram of the device.

The device contains a current filter of zero sequence 1, high harmonic current filter 2, measuring element 3, time element 4, cycle counter 5 and actuator

When a zero-sequence current appears enough to trigger the measuring body 3, a signal from time 4 arrives from its output. If the series overlap is stable, the time relay is activated and acts on the protection actuator b, through which the trip or signal action is performed . With an unstable overlap of the relay, the cycle counter 5, counting out the corresponding number of restorations and extinctions of the arc, also acts on the protection executive body 6.

The loop counter is reset to zero if the information on it was not completely recorded,

The proposed protection for its implementation does not need a special installation of additional current transformers, but can use current transformers designed for other equipment.

Claims (1)

Invention Formula A device for protection against stable and intermittent short circuits of a row of a high-harmonic capacitor battery filter, operating in parallel with similar capacitors in an ungrounded neutral network, containing a zero-sequence current filter and a series-measuring current element with a time element and an actuating element, characterized in that, in order to improve reliability, sensitivity and selectivity, a higher harmonic retaining filter is added to it and a cycle counter, with a higher harmonic filter being turned on {I & waiting for the zero-sequence current filter and current measuring organ, and the cycle counter is connected in parallel with the time element