CN202816637U - Voltage transformer - Google Patents

Abstract

The utility model embodiment provides a voltage transformer. The voltage transformer comprises a potential indicator, a main secondary winding and an auxiliary secondary winding, wherein the potential indicator is connected with a primary winding and timely shows running voltage of the primary winding; the main secondary winding is connected with a three-phase voltmeter and guides bus to earth voltage; the auxiliary secondary winding is connected with an over voltage relay and is in an open-delta connection. When single phase grounding of circuits breaks down, over voltage is generated on the auxiliary secondary winding and the over voltage relay sends alarming signals. The voltage transformer solves the problems that power grid dispatchers and transformer substation operators are difficult to find earth fault caused by prior voltage transformers, achieves the purpose of timely finding voltage transformer secondary insulation inspection table neutral conductor open circuit, and simplifies recognition time of the single phase grounding.

Description

Voltage transformer

Technical field

The utility model particularly about power transformation and dispatching and monitoring equipment, is a kind of voltage transformer about power equipment concretely.

Background technology

In small current neutral grounding system, generally adopt the interchange insulating monitor of non-selectivity to come the single phase ground fault of monitoring system.This exchanges insulating monitor and gathers bus-bar potential transformer secondary and auxiliary secondary winding voltage, and wherein voltage transformer master secondary winding connects three-phase voltage meter monitoring Bus Voltage (being phase voltage); Secondary assistant winding is connected into open-delta and is connected with overvoltage relay.During normal operation, because three-phase system is symmetrical, open delta place no-voltage, voltage relay attonity, the alert signal of not transmitting messages.If when line single phase grounding failure occurs, the Earth Phase phase voltage will reduce, all the other phase voltages raise, and residual voltage occurs.The open delta place overvoltage will occur and send the grounding alarm signal.The Earth Phase lower voltage is to zero during metallic earthing, other phase voltages raise for line voltage (namely

Times phase voltage).It more than is the phenomenon that the secondary insulating supervisory device neutral earthing at voltage transformer reflects under normal circumstances.But when the secondary insulating supervisory device neutral line of voltage transformer was in open circuit situation, although the alert signal of transmitting messages, three-phase voltage was constant, and can't judge Earth Phase this moment.

The utility model content

The utility model embodiment provides a kind of voltage transformer, dispatching of power netwoks person and the very difficult problem of seeking earth fault of substation operation personnel that existing voltage transformer causes have been solved, realized instant discovery voltage transformer secondary insulating monitoring table neutral line open circuit, the differentiation time of simplifying simultaneously single-phase earthing.

The purpose of this utility model is, a kind of voltage transformer is provided, and described voltage transformer comprises: potential indicator, be connected with a winding, and show in real time the working voltage on the described winding;

Main secondary winding is connected with three-phase voltage meter, the monitoring Bus Voltage;

Auxiliary secondary winding is connected with overvoltage relay, and described auxiliary secondary winding is open-delta;

When supply lines bus single-phase earthing breaks down, produce overvoltage on the described auxiliary secondary winding, described overvoltage relay sends alarm signal.

The beneficial effects of the utility model are, by installing potential indicator additional in circuit inlet wire side, simultaneously potential indicator is accessed supervisory control system, realized when PT secondary device insulating monitor broken neutral line, can be timely, accurately judge Earth Phase, being beneficial to fault in time gets rid of, improve the dispatching automation level, has higher practical value, dispatching of power netwoks person and the very difficult problem of seeking earth fault of substation operation personnel that existing voltage transformer causes have been solved, realized instant discovery voltage transformer secondary insulating monitoring table neutral line open circuit, the differentiation time of simplifying simultaneously single-phase earthing.

Description of drawings

In order to be illustrated more clearly in the utility model embodiment or technical scheme of the prior art, the below will do to introduce simply to the accompanying drawing of required use in embodiment or the description of the Prior Art, apparently, accompanying drawing in the following describes only is embodiment more of the present utility model, for those of ordinary skills, under the prerequisite of not paying creative work, can also obtain according to these accompanying drawings other accompanying drawing.

Fig. 1 is the schematic diagram of voltage transformer of the prior art;

Fig. 2 is the vectogram of voltage transformer of the prior art when normal;

Vectogram when Fig. 3 is C phase ground connection behind the voltage transformer secondary insulating monitoring table neutral point open circuit of the prior art;

The schematic diagram of a kind of voltage transformer that Fig. 4 provides for the utility model embodiment.

Embodiment

Below in conjunction with the accompanying drawing among the utility model embodiment, the technical scheme among the utility model embodiment is clearly and completely described, obviously, described embodiment only is the utility model part embodiment, rather than whole embodiment.Based on the embodiment in the utility model, those of ordinary skills are not making the every other embodiment that obtains under the creative work prerequisite, all belong to the scope of the utility model protection.

As shown in Figure 1; in the prior art; voltage transformer is connected on the supply lines bus under normal circumstances; winding and the main secondary winding of voltage transformer are connected into star; (winding is working earthing to the direct ground connection of neutral point O; main secondary winding is protection type ground connection), auxiliary secondary winding is connected into the open-delta of residual voltage output.A, b, three voltmeter indications of c are shown the bus phase voltage.When electric power system zone low-pressure side 35kV or 10kV generation C phase single phase ground fault, the original symmetric relation of voltage transformer is destroyed, winding voltage of C phase this moment is zero, A, the voltage of a winding of B rises to line voltage, main secondary winding A then, the voltage of B phase also raises, and the open-delta both end voltage is three times of voltages (100V).If following simultaneously the insulating monitor in the auxiliary winding of voltage transformer secondary (is the CJJ position among Fig. 1, this is the intrinsic coil in the voltage transformer, belongs to traditional wired, does not generally need special explanation) neutral line open circuit, cut-off point is the N point, and this moment, N produced potential difference to C so.Ask each voltmeter numerical value to be with the nodal method of analysis:

The indication of C phase voltage table:

The indication of A phase voltage table:

In like manner, B phase voltage table indication:

$U_b={\stackrel{\·}{U}}_{\mathrm{cb}}-{\stackrel{\·}{U}}_{\mathrm{CN}}=U_{\mathrm{ob}}$

Hence one can see that three-phase voltage meter U _a=U _OaU _b=U _ObU _c=-U _Oc

Fig. 2 is vectogram under normal circumstances, Fig. 3 be the C of system phase ground connection and follow voltage transformer secondary insulating monitoring table neutral point open circuit after vectogram, by Fig. 2 and Fig. 3 as can be known, when system's generation single-phase earthing and follow voltage transformer secondary insulating monitoring table neutral point when open circuit, three-phase is designated as the normal voltage value, do not reflect voltage change after the ground connection, voltmeter reaction absolute value does not have positive and negative.But in secondary open delta coil, occur

Make the action of supervision voltage relay, send the grounding alarm signal.

The schematic diagram of a kind of voltage transformer that Fig. 4 provides for the utility model embodiment, as shown in Figure 4, described voltage transformer comprises: potential indicator, be connected with a winding, show in real time the working voltage on the described winding;

Main secondary winding is connected with three-phase voltage meter, the monitoring Bus Voltage;

Auxiliary secondary winding is connected with overvoltage relay, and described auxiliary secondary winding is open-delta;

When supply lines bus single-phase earthing breaks down, produce overvoltage on the described auxiliary secondary winding, described overvoltage relay sends alarm signal.

Under not open circuit operation mode of secondary insulating supervision table neutral point, the voltage transformer that the utility model embodiment provides is the same with the phenomenon that routine transformer reacts.Under secondary insulating supervision table neutral point open circuit operation mode, for example when A phase ground connection, the magnitude of voltage that the three-phase secondary shows still is phase voltage, i.e. U _a=U _OaU _b=U _ObU _c=-U _Oc, overvoltage relay sends alarm signal.But this moment, A phase potential indicator was zero owing to the voltage that bears falls, and A phase potential indicator namely can comprhensive deterministic system A phase ground connection in conjunction with potential indicator and ground signalling with circuit A phase dead electricity.

In sum, useful achievement of the present utility model is: by installing potential indicator additional in circuit inlet wire side, simultaneously potential indicator is accessed supervisory control system, realized when PT secondary device insulating monitor broken neutral line, can be timely, accurately judge Earth Phase, being beneficial to fault in time gets rid of, improve the dispatching automation level, has higher practical value, dispatching of power netwoks person and the very difficult problem of seeking earth fault of substation operation personnel that existing voltage transformer causes have been solved, realized instant discovery voltage transformer secondary insulating monitoring table neutral line open circuit, the differentiation time of simplifying simultaneously single-phase earthing.

Used specific embodiment in the utility model principle of the present utility model and execution mode are set forth, the explanation of above embodiment just is used for helping to understand method of the present utility model and core concept thereof; Simultaneously, for one of ordinary skill in the art, according to thought of the present utility model, all will change in specific embodiments and applications, in sum, this description should not be construed as restriction of the present utility model.

Claims (1)

1. a voltage transformer is characterized in that, described voltage transformer comprises:

Potential indicator is connected with a winding, shows in real time the working voltage on the described winding;

Main secondary winding is connected with three-phase voltage meter, the monitoring Bus Voltage;

Auxiliary secondary winding is connected with overvoltage relay, and described auxiliary secondary winding is open-delta;

When supply lines bus single-phase earthing breaks down, produce overvoltage on the described auxiliary secondary winding, described overvoltage relay sends alarm signal.

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