SU639045A2 - Null sequence protection relay - Google Patents

Description

The invention relates to electrical engineering, in particular, to devices for relay protection of power transmission lines from a cable to the ground in networks with large earth fault currents, which are subject to greater detuning from the surges of magnetized currents of transformers to detect the sensitivity of protection. In the main invention auth.St. No. 284125 describes a zero-sequence protection relay, which is intended for use in accelerated protection stages. It contains three intermediate saturable current transformers, the primary windings of which are connected to the line currents (line phase currents) of the transformer line currents, and their secondary windings are connected in parallel and connected to the reacting authority 1. The device has a continuous detuning from periodic surges of magnetizing current, having large negative half-waves, with non-full-phase inclusions. However, in the case of two-phase closures behind a transformer connected to the protected line on the connection side of the delta-8 windings, unequal currents flow through the primary and secondary windings of the current transformers. As a result, intermediate saturable current transformers are holed up to varying degrees, and an unbalance current appears in the reacting organ, which reduces the sensitivity of the sewn up. The purpose of the additional invention is to improve the detuning from unbalance currents in asymmetrical modes. The goal is achieved by the fact that in the known zero-sequence protection relay auth. H1284125 the magnetic cores of intermediate fast-acting transformers are made with middle rods, which are wound on a common extra: the primary winding is connected between the common 1 of the current transformers of the linear currents and the primary windings. Due to this solution, for all types of short circuits (including short circuits behind a triangle of a transformer connected to the protected line) that are not connected to earth, the voltage on the secondary windings will be close to zero and the unbalance current will be almost zero. .

Single-phase and two-phase ground loops at the filter output result in a zero-sequence current, which flows around the primary winding covering the middle rods of the current transformer, so the protection in this case is triggered when the set current is exceeded. The detuning from aperiodic and periodic bits in the proposed device is based on the same principle of saturating intermediate on-line current transformers, in connection with which the transformation of periodic constituent bits in primary transformers to the primary ones deteriorates.

The drawing shows a diagram of the relay. The relay contains three linear current transformers 1. The linear currents (phase currents of the electric line) of each current transformer 1 include the primary windings 2 (), / located at the outermost cores of the magnetic cores 3 of the three-core current saturating transformers. The additional primary winding 4 (Vp) encompasses the three gutter bar of the magnets and saturation lines: from current transformers 3. The secondary windings 5 tWg, t located on the outermost cores of the magnetic electrodes 3 are connected in parallel and connected to the pear 6 organ 6. As a responsive An organ, for example, electromagnetic part current relay, windings 2 (Wp.2)), located on the outermost rods, consists of the same number of turns and are connected in series so that (taking into account the polarity of each winding) 2 (Wpj) are closed on the extreme rods of the magnesium pipelines 3 and lead in parts of the secondary windings 5 (Wgi) electromotive SN.PY, which are balanced. For non-earth short circuits, force is impaired. flooding of secondary windings (WB from the flow of short circuit currents in windings 2 (Wpj), is practically zero). Short currents of the first language in windings 2 (Wp 21 saturate the extreme rods of the magnetic circuit of saturable transformers of track 3, as a result detuning from transient and ustamoviviks of unbalance currents, which for No. 5 are located in the secondary windings) located on the saturated extreme

Sergets and do not get into the reacting authority 6,

This takes place at any interphase closures, including two-phase closures behind the delta of a transformer connected to the protected line, when up to 2 items (p2 unequal currents flow.

With single-phase and two-phase short-circuits to earth, the value of the zero sequence current is sufficient to trigger the reacting organ, and the inhibitory effect of the currents in the windings 2 (W-p2) is insufficient to keep the reacting organ 6 in the failed state.

In case of any incomplete-phase and fully-Phase switching-on transformers connected to the protected line, at idle, those magnetic cores of 3 saturable current transformers will be saturated, through the windings 2lWp2) of which there will be aperiodic inrush of magnetizing current. In this case, the resistance of the secondary windings 5 (Ws} / located on the extreme rods of the saturable magnetic cores 3 will decrease and shunt the reacting organ B. As a result, the relay is rebuilt from the magnetizing current surges.

The advantage of the proposed relay over limescale is due to the exception of incorrect operation during phase-to-phase short circuits, in particular two-phase short circuits behind the triangle of a transformer connected to the protected line.

Oormula invention

Relay for ita zero sequence auth.St. 284125, characterized in that, in order to improve the detuning from unbalance currents in asymmetrical modes, the magnetic cores of the intermediate high-speed transformers are made with middle rods, on which the common additional primary winding is wound, is connected between the common points of the linear current transformers and the primary windings.

Sources of information taken into account in the examination;

1. USSR author's certificate 284125, H 01 H 83/16, 02.26.68