SU574810A1 - Eart-current protection arrangement for mains with insulated and compensated neutral phase - Google Patents

Description

consistency, and others to one of the secondary windings of the transformer 4 of the zero sequence, phase chain R-C 5 connected between the input of the main phase-sensitive organ 1 and the output of the secondary winding of the transformer 4 of zero sequence voltage, limiting resistor 6 and switch 7, connected parallel to the phase-turning chain 5, the prohibition scheme 8, whose input is connected to the output of the main phase-sensitive organ 1, the elements of “Restricted to us - the main 9, whose input is connected to the output barring circuit 8, additional 10, the input of which is connected to the output of the additional phase-branching organ 2, the circuit OR 11, whose inputs are connected to the outputs of the elements “Limited memory 9 and 10, and the output to the prohibitory input of the prohibition circuit 8, element Memory 12 whose main input is connected to the output of the ILR1 11 circuit, erasing the input through the NOT 13 circuit is connected to the output of the new phase-sensitive organ 1, and the output to the control input of the key 7, the executive member 14, whose input is connected to the output of the element “Limited memory 9 .

The device works as follows.

In normal mode, the phase-sensitive organs 1 and 2 and the executive board 14 are in the initial state. Key 7 is closed. In the elements of "Limited memory 9,

10 and “Memory 12 no information recorded. The erase sigal is fed to the erase input of the “Memory 12” element.

When a single-phase earth fault occurs at the connection in the first transition period, the zero sequence current through the damaged connection coincides with a zero sequence voltage. As a result, the phase-sensitive organ 1 triggered to coincide is triggered, and its output a signal appears which, having passed the inhibit pattern 8, goes to the “Ogram memory 9” memory where the entire period of the transition process is remembered (several milliseconds) and simultaneously causes actuation of an insulatory body 14.

At the same time, the sigial from the output of the element "Limited memory 9 through the scheme OR

11 arrives at the prohibiting input of the prohibition scheme 8 and the main input of the “We are 12.

In the second half period of the transient, the direction of the zero sequence current is reversed relative to the zero sequence voltage, and short-term operation of the additional phase-branching organ 2 occurs, from which output the signal is fed to the input of the element Limited memory 10, which is stored for the duration of the transition process . From the output of the element "Limited memory 10 signal

through the OR circuit AND is fed to the prohibiting input of the prohibition circuit 8 and the main input of the memory element 12, when activated, the key 7 opens. As a result, the zero-sequence voltage, which enters the inputs of the phase-sensitive organs 1, 2, rotates with respect to the zero-sequence current through an angle of 90 °. This ensures the expansion of the selectivity zone and obtaining the maximum sensitive protection (by compensating for the phase shift) in the steady state single-phase earth fault, in which the current and the zero voltage are shifted by 90 °.

After the transient time and after closing the key 7, the phase-sensitive organs 1, 2 will receive current and voltage of zero sequence, coinciding, as in the transient mode, in phase.

The limited memory 10 is returned to its original state and the prohibitory input of the inhibit circuit 8 is removed. The phase-sensitive organ 1 operates on the current and the zero-order sequence of the steady state.

When an external ground fault occurs, for example, on tires of a protected network or on another front-end, the first half-wolf of the transient current in an intact front-dipyne has a reverse direction in relation to the zero sequence voltage and compared to the current direction in

damaged attachment. As a result, an additional phase-sensitive organ 2 is triggered and, from its output, through the element Limited memory 10 and the algorithm OR 11, a signal is sent to the inhibiting input of the inhibitor circuit, thus preventing false (non-selective) operation of the device during the second half-cycle of the transient process 1 favorable t) 1st phase relations.

The proposed device for protection against ground faults on the ground represents the possibility of simultaneously acting on both transient currents and pa which have been established. In addition, it eliminates the need for barrier filters, delay circuits, etc.

Claims (2)

1.V. L. Andreev, et al. Relein, protection of automation and remote control in power supply systems. M., “Higher School, 1975, p. 182. 2. Authors certificate of the USSR 317139 cl. And 02I 3/38, 1969.