RU199969U1 - ZERO-SEQUENCE EARTH FILTER WITH REDUCED POWER CONSUMPTION - Google Patents

Abstract

The field of use relates to electrical engineering, namely to power equipment for the protection of medium voltage electrical networks from the effects of single-phase earth faults. The essence of the utility model: zero sequence grounding filters with reduced power consumption in normal operation of the electrical network. The technical result of the utility model is to reduce the value no-load current of the zero-sequence filter, which is the main mode of operation, in simplifying the implementation of the task, in increasing the energy efficiency of the equipment, its reliability. The specified technical result is achieved by the fact that to reduce the current consumption in the idle mode, the reactive component of the current is compensated by connecting a capacitor or adjustable capacitor device to the line voltage terminals of the secondary winding.

Description

The proposed utility model relates to electrical engineering, namely, to transformer devices designed to isolate the neutral and connect grounding devices to the electrical network in the form of arc suppression reactors (ARCs), high-resistance and low-resistance resistors (RZ).

To connect the DGR and RZ, transformers with a "star-zigzag with zero" primary winding connection are currently used Zo - zero-sequence grounding filters with low resistance to zero-sequence currents, which are installed instead of transformers by connecting the "star-zero-delta" windings Yo / D. Three-phase transformers of this purpose, containing primary and secondary windings, operate for a long time in idle mode [1].

In these transformers and zero sequence filters operating in no-load modes, or close to this mode with a low load factor, the current consumed by them is mainly determined by the magnetizing power, which leads to a low active power factor (cos (φ)). With insignificant load factors of the transformer, which is often the case in compensation systems for capacitive short-circuit currents based on GDR, high-resistance resistive and combined type of neutral grounding of the network, the efficiency of the transformer is also low.

Known devices that increase cos (φ) [2]. They are connected to the secondary windings of transformers and are designed to compensate for the reactive power consumed by the load. Their use is effective at significant loads of transformers and the value of the compensated reactive power, depending on the change in the load factor, is regulated. And in idle mode, transformers consume magnetizing power, while having a very low cosφ. The flow of reactive current additionally causes voltage and power losses in the supply network.

In [3], a prototype of the proposed utility model is presented. In it, the reactive power consumed by the transformer is compensated by connecting a three-phase capacitor device to a part of the primary winding or to the secondary winding of the transformer, connected according to the "star" or "delta" scheme with the total capacitor power equal to the reactive component of the power consumption of the transformer in idle mode.

The purpose of the proposed utility model is to increase the active power factor of grounding filters operating mainly in no-load modes and those close to this mode, to reduce voltage and electricity losses in supply distribution electrical networks, to simplify the technical implementation of the proposal, and to increase equipment reliability.

The purpose of increasing cos (φ), reducing voltage and electricity losses in the supply network is achieved by compensating for reactive power consumption by a grounding filter of the zero sequence by connecting a capacitor with a calculated or experimental power equal to the power of the reactive component of the filter's power consumption to its secondary windings.

The aim of simplifying the technical implementation of reducing losses in the proposed filter is achieved by using a single capacitor or an adjustable capacitor unit instead of using a three-phase capacitor unit in the prototype.

FIG. 1-2 shows the diagrams of connecting capacitors to the secondary windings of the grounding filters (neutralizing transformers) with a diagram of connecting parts of the primary winding with voltagesU _{A 1} ,U _{B 1} ,U _{C 1} ,U _{A 2} ,U _{B 2} ,U _{C 2} , "Star-zigzag with zero" with line voltage connected to the secondary compensation windingU _ac obtained from phase voltagesU _a U _c , capacitorFROM _R or an adjustable condensing unitC1, C2, C3 with switchesS1, S2 andS3 (Fig. 1), as well as the aforementioned filter by connecting parts of the primary winding "star-zigzag" with connecting a three-phase capacitor bankFROM _and , FROM _b , FROM _from with switchS4 to phase-to-phase voltage "and"And"from"(Fig. 2). The connection of the mentioned capacitors, if necessary, can be performed according to other schemes, with the provision of the possibility of full compensation of the reactive component of the current consumption by the filter.

The choice of capacitors is made on the basis of the equality of the reactive powers of the magnetizing transformer and that generated by the capacitors, taking into account their connection scheme on the secondary side of the transformers or connected to the taps of its primary winding.

The use of a useful model of grounding filters with capacitors permanently connected to the secondary winding or adjustable capacitor units provides a high active power factor in no-load and low-load modes, helps to reduce voltage and electricity losses in power supply networks and increase equipment reliability.

LITERATURE:

1. Reactors grounding arc suppression 6-35 kV. General technical requirements. Organization standard of PJSC Rosseti STO 34.01-3.2-008-2017. PJSC "Rosseti", 2017. - 22 p.

2. Minin G.N. Reactive power. - 2nd ed., Rev. - M .: Energoiz, 1978 .-- 88 p.

3. Pat. 149108. Russian Federation, IPC H01F 29/00. Earthing filter with reduced power consumption / Petrov M.I .; applicant and patentee Petrov M.I. - No. 2014134694/07; declared 08/25/2014; publ. 20.12.2014, Bul. No. 35.

Claims (2)

1. The filter grounding the zero sequence of the connection of the windings according to the "star-zigzag with zero" scheme Zo with the secondary winding, characterized in that the adjustable power capacitor is connected to the line voltage terminals of the secondary winding. 2. The earthing filter according to claim 1, characterized in that the capacitors assembled according to the "delta" circuit with a switch are connected to the line voltage terminals of the secondary winding.

Images