SU760295A1 - Device for compensating for single-phase earthing current - Google Patents

Description

The invention relates to the field of compensation of single-phase earth-fault currents in electrical networks.

Known devices compensation capacitances and the active component of the current single-phase earth fault [1]. Their main disadvantage is the complexity of both the devices themselves and ensuring accurate compensation, since regulation must be carried out simultaneously through two channels (reactive and active components). ,

The disadvantages of these devices also include the fact that when a single-phase ground fault occurs, a slow-damping aperiodic component usually occurs through the damage site, due to the effect of the compensating device ¹⁵ , which delays the damping of the grounding arc and increases the touch voltage in transients.

The closest in technical essence _Μ

ti is a device to compensate

active component of single-phase current

earth faults containing three-phase trans2 connected in series

formator, voltage (phase) selection unit and single-phase transformer, the secondary winding of which is connected to the mains neutral [2].

However, this device is not providing a compensation capacitance ₅ fault current? F! Lu and should be used together, e.g., with arc suppression coil.

The purpose of the invention is to improve the reliability of the electrical network and the improvement of electrical safety.

To achieve this goal, a conversion unit with a differentiating element, made, for example, in the form of a series connection of a capacitor and a resistor connected between the auxiliary voltage source and ground, is introduced into the device to compensate for the single-phase earth-fault current, which contains an additional voltage source connected to the network. The device also includes a single-phase matching transformer, the secondary winding of which is connected between the neutral of the network and the ground, the unit for measuring the parameters of the network relative to the ground, and the source of additional voltage contains a three-phase transformer,

3,7602ν

connected to the network, a phase selection unit and a single-phase adjustable transformer, with the primary windings of a single-phase adjustable transformer connected to the zero output respectively and through the phase selector to the phase outputs of the secondary winding of a three-phase transformer, the secondary windings of a single-phase adjustable transformer are connected to ground through the conversion unit and through the primary winding of the single-phase matching transformer, respectively, and the single-phase control input is adjustable a transformer connected to the measuring unit.

The drawing shows the electrical circuit of the device.

A three-phase source 1 having voltage Od and _b and 0 _s feeds the electrical network, the parameters of which relative to the earth can be represented as a set of 2 capacitances and active resistances.

To a three-phase transformer neutral January 20 connected single-phase matching transformer 3, whereby the device for compensation may be performed on voltages below 1000 V. By its primary winding connected in series connected resistor 4, a condenser 5 and single-phase ³ ny adjustable transformer 6. The primary winding of the latter through The phase selection unit 7 is connected to the secondary winding of a three-phase transformer 8 fed from an electrical network. thirty

In the scheme there is a block 9 measuring the parameters of the network relative to the ground, which is connected with the adjusting input of the single-phase transformer 6.

In normal network operation mode, the network parameter measurement unit relative to ground 35, depending on the value of the specified parameters, issues a signal to the adjusting input of a single-phase transformer, the primary winding of which is disconnected in this mode. ₄₀

When a single-phase earth fault occurs, for example, the phase A of the network (link 10), the primary winding of the transformer 3 generates a voltage and ₀ - The phase selection unit 7 selects and connects the phase A of the secondary winding of the transformer 8 to the primary winding

6. As a result, the secondary voltage of the latter transforms the voltage ί ^, which is in-phase with the voltage and ₀ , if we consider them with respect to point 11, and is counter-directed to it, if we consider a closed circuit. Voltage 13 ^. more and about magnitude, so it will determine in a closed circuit the capacitive-active current flowing through the capacitor 5 and the resistor 4. This current, transforming into an electric ¹ 4

chesky network, will be counter-directed and will compensate for the current single-phase short circuit to earth. With correctly selected parameters of the capacitor, resistor and the set voltage value, the current of the main frequency will not flow through the circuit.

The application of the proposed device will provide accurate compensation of the single-phase ground current of the main frequency, which will significantly improve the reliability of the electrical network, improve electrical safety conditions for personnel serving electrical installations, as well as simplify the design and operation of the compensation system as a whole.

Claims (2)

Claim 1. A device for compensating a single-phase earth-fault current, containing an additional voltage source connected to the network, characterized in that, in order to improve the reliability of the network and improve electrical safety conditions, a conversion unit with a differentiating element is inserted into it, for example, as a series connection of a capacitor and a resistor, connected between the source of additional voltage and ground. - 2. Device by π. 1, characterized in that a single-phase matching transformer is introduced into it, the secondary winding of which is connected between the mains neutral and ground, a unit for measuring the network parameters relative to the earth, and an additional voltage source contains a three-phase transformer connected to the mains, a phase selection unit and a single-phase adjustable transformer, moreover, the terminals of the primary winding of a single-phase adjustable transformer are connected respectively to the zero output and through the phase selector to the phase terminals of the secondary winding first transformer secondary winding terminals of single-phase variable transformer connected to ground via the conversion unit and through the primary winding of the matching transformer of single-phase, respectively, and adjusting the input single-phase variable transformer connected to the measuring unit.