CN104833836A - Zero sequence voltage detection method for voltage transformer - Google Patents

Abstract

The invention provides a zero sequence voltage detection method for a voltage transformer. The zero sequence voltage detection method comprises the steps of including three opening triangle windings and measuring windings at the secondary side of a voltage transformer, and adding three-phase AC voltage U square root 3 with equal phase and equal amplitude to the three phase of a measuring winding terminal row (the voltage phase of the three phase is zero); observing the value of an analog zero sequence voltage through a display screen of a protection device, connected to the opening triangle winding; observing the value ULN of the analog zero sequence voltage through an AC voltmeter connected to the opening triangle winding and a neutral point N, if the protection device is of an electromagnetic type; determining whether it is abnormal based on U square root 3 and ULN. The zero sequence voltage detection method for a voltage transformer is advantageous in that the whole process of generating zero sequence voltage can be correctly simulated; whether the loop of each winding is defected or not can be accurately detected without disassembling the secondary terminal line of the voltage transformer; the time for the whole test is very short.

Description

A kind of voltage transformer (VT) zero sequence voltage detection method

Technical field

The invention belongs to relay protection field, is particularly a kind of voltage transformer (VT) zero sequence voltage detection method.

Background technology

In small current neutral grounding system, the effect of voltage transformer (VT) is metering, monitoring and relay protection.Wherein open triangle winding and whether produce the important evidence that residual voltage is a judgement line-to-ground and broken string, play the effect of relay protection.

In traditional relay protection test; disassemble school line to voltage transformer secondary line quite to bother; then just merely a protection fixed value voltage is added to relay coil and make the actuating of relay; even if complete residual voltage (ground protection) test, and correctly do not simulate the overall process of residual voltage generation according to electromagnetic induction principle.Therefore, its shortcoming and defect of this test method is apparent: one is adopt voltage transformer (VT) to disassemble school, secondary line termination line, its clearing time and to recover the end line time longer and easily make mistakes; Two is the setting valves cannot verifying residual voltage; ; Three is can not confirmatory measurement winding and open the mutual no-load voltage ratio relation of triangle winding; Four is the inner connecting ways can not verifying out triangle winding; Five is to verify out whether triangle winding terminal is connected with external protector correctly complete; Six is to verify each winding inside whether defectiveness.

Summary of the invention

Technical matters to be solved by this invention is to provide a kind of voltage transformer (VT) zero sequence voltage detection method, object is exactly correctly can simulate with electromagnetic induction principle the overall process that residual voltage produces, and can disassemble again the loop whether defectiveness that voltage transformer secondary end line just can check each winding complete and accurate

The present invention is achieved in that a kind of voltage transformer (VT) zero sequence voltage detection method, comprises the steps:

(1) comprise three open-triangular winding at the secondary side of voltage transformer (VT) and measure winding, the three-phase of measurement winding terminals row adds the three-phase alternating voltage of same-phase with amplitude simultaneously on three-phase, voltage-phase is all set to zero degree;

(2) numerical value of the display screen observatory control residual voltage of the protective device connected by open-triangular winding; If protective device is electromagnetic type type, then by open-triangular winding with numerical value U neutral point N being connected an A.C. voltmeter observatory control residual voltage _lN;

(3) abnormal judgement, works as U _lN=3U, judges that three open-triangular winding are that head and the tail are connected in series;

Work as U _lN=2U, judges that three open-triangular winding are that series-parallel connection form connects;

Work as U _lN=U, judges that three open-triangular winding are that parallel form connects.

The present invention compared with prior art, beneficial effect is: the present invention's electromagnetic induction principle correctly can simulate the overall process that residual voltage produces, the loop whether defectiveness that voltage transformer secondary end line just can check each winding complete and accurate can be disassembled again, and whole test period is very of short duration, should give popularization.This method is not only simple but also accurately, and has opened up new debugging mentality for reaying protection test personnel.

Accompanying drawing explanation

Fig. 1 is the voltage transformer (VT) schematic diagram that the embodiment of the present invention provides.

Embodiment

In order to make object of the present invention, technical scheme and advantage clearly understand, below in conjunction with embodiment, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, be not intended to limit the present invention.

Embodiment:

See Fig. 1, a kind of voltage transformer (VT) zero sequence voltage detection method, comprises the steps:

(1) at terminal block double measurement winding terminal A630 (640) of voltage transformer (VT), B630 (640), C630 (640) add simultaneously the three-phase alternating voltage of same-phase (namely the measurement winding A phase B phase C phase of secondary side is all set to 0 °) with amplitude such as all add

(2) if protective device is integrated protection type, then the numerical value of analogue zero sequence voltage can be seen by the display screen of protective device; If protective device is electromagnetic type type, then by connecing an A.C. voltmeter see analogue zero sequence voltage U at L600 and n600 two ends _lNnumerical value.

(3) when after the every winding of measurement mutually input voltage, also voltage can be induced at every phase open-triangular winding.Because the voltage ratio that every platform voltage transformer secondary measures winding and open-triangular winding is namely so when every phase input time, every phase again because input three arc in phase and amplitude is equal, so three open-triangular winding total voltage after concatenation should be three voltages in-phase stacking, that is:

$\begin{array}{c}{U}^{\·}\mathrm{LN}=U^{\·}\mathrm{da}+U^{\·}\mathrm{db}+U^{\·}\mathrm{dc}\\ =10+10+10\\ =30\left(V\right).\end{array}$

Like this, correctly whether open-triangular winding be connected to utilize the electromagnetic induction principle of every platform voltage transformer (VT) two Secondary Winding and no-load voltage ratio relation both can verify, can check again the setting valve of residual voltage.

(4) the actual detection of residual voltage setting valve.Known residual voltage setting valve is U _lN, so every winding institute making alive of measuring mutually is and homophase.Such as, known residual voltage setting valve is 25V, and so every winding institute making alive of measuring mutually should be and three voltage-phases are all set to zero degree (homophase).The analogue zero sequence voltage of 25V so just can be produced between L600 and N600.

(5) abnormal judgement.When inputting three with identical amplitude at measurement winding following three kinds of situations may be there are during voltage.

The first.ULN＝30V。Illustrate that three open-triangular winding are that head and the tail are connected in series.

The second.ULN＝20V。Illustrate that three open-triangular winding are that series-parallel connection form connects.

The third.ULN＝10V。Illustrate that three open-triangular winding are that parallel form connects; In addition, if do not do Check up polarity, although be that head and the tail series connection may have the polarity of a phase contrary.

Adopt the new detection practical and technical methods of residual voltage, not only simple but also accurately, and opened up new debugging mentality for reaying protection test personnel.

The foregoing is only preferred embodiment of the present invention, not in order to limit the present invention, all any amendments done within the spirit and principles in the present invention, equivalent replacement and improvement etc., all should be included within protection scope of the present invention.

Claims (1)

1. a voltage transformer (VT) zero sequence voltage detection method, is characterized in that, comprises the steps:

(1) comprise three open-triangular winding at the secondary side of voltage transformer (VT) and measure winding, the three-phase of measurement winding terminals row adds the three-phase alternating voltage U of same-phase with amplitude simultaneously on three-phase, voltage-phase is all set to zero degree;

(2) numerical value of the display screen observatory control residual voltage of the protective device connected by open-triangular winding; If protective device is electromagnetic type type, then by open-triangular winding with numerical value U neutral point N being connected an A.C. voltmeter observatory control residual voltage _lN;

(3) abnormal judgement, works as U _lN=3U, judges that three open-triangular winding are that head and the tail are connected in series;

Work as U _lN=2U, judges that three open-triangular winding are that series-parallel connection form connects;

Work as U _lN=U, judges that three open-triangular winding are that parallel form connects.