CN204536524U - For the current transformer otherness detection system of uneven testing circuit - Google Patents

Abstract

The utility model provides the current transformer otherness detection system for uneven testing circuit, comprising two current transformers with contrasting to be detected, also comprising variable-frequency power sources and oscillograph; The primary conductive bar of two described current transformers is serially connected in the output loop of variable-frequency power sources mutually; Draw two Secondary Winding from every current transformer, wherein the different name end of a Secondary Winding on a current transformer and a Secondary Winding on another current transformer is connected in parallel and exports on an analysis channel of described oscillograph; The Same Name of Ends parallel connection of two Secondary Winding of two current transformer remainders is connected and exports on another analysis channel of described oscillograph.Can by two current transformers to be measured simultaneously access testing system, by regulating variable-frequency power sources size and frequency, detecting the characteristic within the scope of whole frequency and rated current, thus judging the otherness of two current transformers to be measured exactly, the shortening time, save labour.

Description

For the current transformer otherness detection system of uneven testing circuit

Technical field

The utility model relates to the correlative technology field such as electrical equipment malfunction detection, electrical test of electrical field, particularly relates to the current transformer otherness detection system for uneven testing circuit.

Background technology

In electrical equipment, often there is the equipment parallel running of multiple same model, and require that the characteristic of these equipment in parallel is completely the same.

Such as in high-voltage parallel capacitor, the capacitor of same phase can compose in parallel Capacitor banks according to the mode of Fig. 1, and wherein the Capacitor banks of A and B two-arm is in series by the same model capacitor unit of same quantity.Electrical specification when two-arm is normal should be completely the same.But, because capacitor is voltage-sensitive equipment, may occur the phenomenon of certain capacitor unit fault (as puncture short) of a wherein arm in operation, now the electric capacity of two-arm is just inconsistent, the i.e. capacitor unbalance of two-arm, and then cause more serious fault.

Whether normal in order to monitor two-arm electric capacity, the current transformer of a same model of usually respectively connecting at the low pressure end of A arm and B arm, by difference between current (the i.e. poor stream between detection two current transformer in operation ) judge whether the capacitor of two-arm balances, as occurred " difference stream ", then the capacitor unbalance of two-arm is described, has partial capacitor unit to there is fault.

Fig. 2 is Secondary Winding composition " difference stream " circuit of current transformer TA and TB and the schematic diagram of " and stream " circuit.The primary conductive bar thick lines of current transformer TA and TB wherein represent.Current transformer TA has two Secondary Winding 1SA, and (no-load voltage ratio is k _a1) and 2SA (no-load voltage ratio is k _a2); Current transformer TB also has two Secondary Winding 1SB, and (no-load voltage ratio is k _b1) and 2SB (no-load voltage ratio is k _b2).Wherein the different name end of the Secondary Winding 1SA of current transformer TA and the Secondary Winding 1SB of current transformer TB is connected in parallel, and then draws lead-in wire from two terminals in parallel respectively, for measuring " the difference stream " of Secondary Winding 1SA and 1SB: 1S=1SA-1SB.The Same Name of Ends of the Secondary Winding 2SA of current transformer TA and the Secondary Winding 2SB of current transformer TB is connected in parallel, then two lead-in wires are drawn from terminal in parallel, for measuring Secondary Winding 2SA and 2SB " and stream ": 2S=2SA+2SB, the effect of " and stream " is the total current in sensing capacitor group.

Wherein,

Primary side " difference stream " is

$\mathrm{\Δ}\stackrel{\·}{I}={\stackrel{\·}{I}}_A-{\stackrel{\·}{I}}_B---\left(1\right)$

Once " and stream " is

${\stackrel{\·}{I}}_{\mathrm{\Σ}}={\stackrel{\·}{I}}_A+{\stackrel{\·}{I}}_B---\left(2\right)$

Corresponding secondary side " difference stream " is

$\mathrm{\Δ}\stackrel{\·}{i}=\frac{{\stackrel{\·}{I}}_A}{k_{A1}}-\frac{{\stackrel{\·}{I}}_B}{k_{B1}}---\left(3\right)$

Corresponding secondary side " and stream " is

${\stackrel{\·}{i}}_{\mathrm{\Σ}}=\frac{{\stackrel{\·}{I}}_A}{k_{A2}}+\frac{{\stackrel{\·}{I}}_B}{k_{B2}}---\left(4\right)$

As can be seen from formula (1) to (4), accurately detecting another key factor that in Fig. 1 case, whether two-arm capacitor balances is: require that (no-load voltage ratio is k to the current transformer TA of two-arm _a1) (no-load voltage ratio is k with TB _b1) no-load voltage ratio characteristic completely the same.But, even if the equipment of same model, due to the deviation of material and manufacturing process aspect, the no-load voltage ratio characteristic of two current transformers also may be caused not quite identical.Therefore, even if the capacitor complete equipilibrium of primary circuit, namely also may due to the inconsistent (k of the no-load voltage ratio of two current transformers _a1≠ k _b1) cause the difference of secondary current to be not equal to zero thus the judgement that leads to errors.

To sum up, whether the electrical specification detecting two parallel branches balances, and requires that the characteristic detecting two current transformers used is completely the same.When factory carries out unit assembled window, the consistance of carrying out two mutual inductor characteristics is needed to test; When installing at the scene and test, also need to carry out consistency check to the characteristic of two current transformers.But to out-of-balance current testing circuit in prior art, be by only carrying out the no-load voltage ratio of current transformer and the detection of phase place, then according to testing result, the relatively family curve of two current transformers, if both are consistent, then think that the characteristic of two current transformers is coincide, can mounted in pairing mode.But due to by only detecting life period difference, be difficult to ensure that environment temperature, humidity etc. are completely the same.And possess the consistent condition of environmental baseline and can increase plant and equipment input cost undoubtedly, testing result is not very good yet.

Summary of the invention

The purpose of this utility model is to propose a kind of current transformer otherness detection system for uneven testing circuit, to improve the accuracy of the Difference test of two current transformers, saves time, manpower and fund.

In order to solve the problems of the technologies described above, the technical solution of the utility model is as follows:

For the current transformer otherness detection system of uneven testing circuit, comprising two current transformers with contrasting to be detected, also comprising variable-frequency power sources and oscillograph; The primary conductive bar of two described current transformers is serially connected in the output loop of variable-frequency power sources mutually; Two Secondary Winding are drawn from every current transformer, wherein the different name end of a Secondary Winding on a current transformer and a Secondary Winding on another current transformer is connected in parallel, and terminal lead in parallel is exported to a signalling channel of described oscillograph; The Same Name of Ends of two Secondary Winding of two current transformer remainders is connected in parallel, and exports terminal lead in parallel another signalling channel of described oscillograph to.

The output loop of described variable-frequency power sources is also serially connected with primary current probe, the output terminal of this primary current probe is connected on described oscillograph.

The utility model is simple and reasonable for structure, can by two current transformers to be measured simultaneously access testing system, by regulating size and the frequency of variable-frequency power sources, oscillograph is observed and compares the characteristic of two current transformers within the scope of whole frequency and rated current, thus the otherness of two current transformers to be measured can be judged exactly, and shorten detection time, save labour.

Accompanying drawing explanation

Fig. 1 is the parallel branch schematic diagram of two capacitors in prior art;

Fig. 2 is the wiring schematic diagram that the Secondary Winding of two current transformers forms " difference stream ", " and stream ";

Fig. 3 is the schematic diagram of the utility model embodiment 1;

Fig. 4 is the exemplary plot of the utility model embodiment 2;

Description of reference numerals:

1, variable-frequency power sources; 2, protective resistance; 3, primary current probe; 4, oscillograph.

Embodiment

For enabling above-mentioned purpose of the present utility model, feature and advantage become apparent more, are described in further detail the utility model below in conjunction with the drawings and specific embodiments.

Embodiment 1

As shown in Figure 3, for the current transformer otherness detection system of uneven testing circuit, comprising two current transformer TA, TB with contrasting to be detected, also comprising variable-frequency power sources 1 and oscillograph 4; The primary conductive bar Same Name of Ends of current transformer TA, TB is serially connected in the output loop of variable-frequency power sources 1 mutually; Current transformer TA, TB have two Secondary Winding, the Secondary Winding 1SA on current transformer TA is connected with the different name end parallel connection of the Secondary Winding 1SB on current transformer TB, and exports in a signalling channel of described oscillograph 4; Secondary Winding 2SA on current transformer TA is connected with the Same Name of Ends parallel connection of the Secondary Winding 2SB on current transformer TB, and exports in another signalling channel of described oscillograph 4.

Further, the output loop of described variable-frequency power sources 1 is also serially connected with primary current probe 3, the output terminal of this primary current probe 3 is connected to described oscillograph 4; In addition, for preventing short circuit, also on the output loop of variable-frequency power sources 1, protective resistance 2 is serially connected with.

For the current transformer otherness detection system of the present embodiment, can be used for the consistency detection of " difference stream " winding of two current transformers, and the no-load voltage ratio of " and stream " winding detects.It comprises:

(1) variable-frequency power sources 1 of adjustable output size and frequency;

(2) powerful protective resistance 2, works the protective effect preventing variable-frequency power sources 1 output short-circuit;

(3) high-precision oscillograph 4, for accurately detecting current amplitude and phase place;

(4) tested current transformer TA and TB:

Wherein, the Secondary Winding 1SB of the Secondary Winding 1SA summation current transformer TB of tested current transformer TA forms " difference stream " winding of secondary side according to the connected mode (parallel connection of different name end is connected) of Fig. 2; The Secondary Winding 2SB of the Secondary Winding 2SA summation current transformer TB of current transformer TA forms " and stream " winding of secondary side according to the connected mode (Same Name of Ends parallel connection is connected) of Fig. 2; The primary side conducting rod of tested current transformer TA and TB is connected according to polarity Same Name of Ends.

Under this input mode, can guarantee that the primary current of two current transformer TA with TB is identical, by regulating size and the frequency of variable-frequency power sources 1, just can observe " difference stream " and " and stream " with two Current Transformer Secondary side windings in whole ratings range of current in whole frequency range.

Ideally, if the characteristic of two current transformers to be measured is consistent, then the difference stream perseverance observed is zero.Thus, in the process of tests and analysis, at any amplitude or Frequency point, if the poor stream of two tested current transformers is greater than certain error requirements, just can conclude that " difference stream " winding characteristic of these two Current Transformer Secondary sides is inconsistent; Otherwise the difference stream of two current transformers to be measured, in certain error requirements, just can conclude that " difference stream " winding characteristic of these two Current Transformer Secondary sides is consistent.

In addition, in the present embodiment, suppose that the Secondary Winding 2SB of current transformer TA Secondary Winding 2SA summation current transformer TB is completely the same, then can flow through the electric current of two current transformer primary sides to be measured by primary current 3 measurements of popping one's head in, compare the secondary side of this primary side current and current transformer TA, TB " and stream ", the no-load voltage ratio of Secondary Winding 2SA, 2SB can be calculated respectively.

Embodiment 2

The present embodiment is with the difference of embodiment 1: the primary side conducting rod of tested current transformer TA and TB is connected according to polarity different name end, i.e. differential concatenation.Other technical characteristic is identical with embodiment 1.

Because current transformer TA is identical with embodiment 1 with the mode of connection of TB Secondary Winding, now the electric current of the primary conductive bar injected system of two current transformer TA and TB does not change, and the actual electric current sum becoming two winding 1SA and 1SB of output current of original " difference stream " winding of their secondary side, and in fact the output current of original " and stream " winding of secondary side becomes the difference between currents of two winding current 2SA and 2SB.

In Fig. 3 and Fig. 4, the secondary side winding 1SA of current transformer TA marked "-" with on the terminal lead in parallel of the secondary side winding 1SB of current transformer TB, means them and constitutes " difference stream " winding; Similarly, the secondary side winding 2SA of current transformer TA marked " ten " with on the terminal lead in parallel of the secondary side winding 2SB of current transformer TB, means them and constitutes " and stream " winding.

If the difference between currents of two of verification experimental verification secondary side winding 2SA and 2SB meets the requirement of limits of error definite value, namely learn that the Secondary Winding 2SB of current transformer TA Secondary Winding 2SA summation current transformer TB is completely the same.In embodiment 1, if the difference between currents of 1SA and 1SB meets the requirement of limits of error definite value, the present embodiment can be passed through, the electric current flowing through two current transformer primary sides to be measured is measured by primary current probe 3, and 1SA and 1SB " and stream ", relatively the electric current sum of the secondary side of this primary side current and current transformer TA and TB, can calculate the no-load voltage ratio of Secondary Winding 1SA, 1SB respectively.

Below, then with an example be described.

At south electric network Zhaoqing current conversion station, wiring and Fig. 1 of DC filtering high-voltage capacitor are wherein similar.Within 2014, there is the phenomenon of 4 primary current unbalance protection unknown cause action tripping operations.For the inconsistent impact brought of the no-load voltage ratio characteristic getting rid of two current transformers, need the Property comparison carrying out current transformer at the scene.

On-the-spot beam variable-frequency electric potential source frequency range is 20Hz ~ 2000Hz, and rated output voltage can reach 300V, and peak power output can reach 3000VA; The resistance in series of hookup have selected the electric furnace heating wire of 3kW and utilizes this resistance to carry out current limliting, prevents variable-frequency power sources 1 exit short circuit.

Scene utilizes high-precision digital oscillograph 4 to read " the difference stream " of two Secondary Winding and the output reading of " and stream " winding.Wherein according to the wiring system of Fig. 3 by the forward wiring of current transformer primary conductive bar time, measure the current value obtained as follows:

Beam test figure during the series connection of table 1 current transformer primary conductive bar forward

As seen from Table 1, the difference stream of two Current Transformer Secondary sides floats among 5.1mA-7.7mA, and error is very little, can think that " difference flows " winding characteristic of two tested current transformers is consistent.

Again according to the wiring system of Fig. 4 by current transformer primary conductive bar reverse wiring time, measure the current value obtained as follows:

Beam test figure during table 2 current transformer primary conductive bar differential concatenation

In table 2, " difference stream " winding of two tested Current Transformer Secondary sides is actual, and what export is the electric current sum of two windings, and the actual output of " and stream " winding is the difference between currents of two windings.In test figure, the difference stream of " and stream " winding is between 2mA to 3.8mA, and error is very little, can think that " with stream " winding characteristic of two tested current transformers is consistent.

As can be seen here, by the pilot system of Fig. 3 and Fig. 4, the characteristic demonstrating station, Zhaoqing DC filtering high-voltage capacitor unbalanced current protection two current transformers used is completely the same.

The utility model is simple and reasonable for structure, can by two current transformers to be measured simultaneously access testing system, by regulating size and the frequency of variable-frequency power sources 1, oscillograph 4 is observed and compares the characteristic of two current transformers within the scope of whole frequency and rated current, thus the otherness of two current transformers to be measured can be judged exactly, and shorten detection time, save labour.

Above-listed detailed description is illustrating for the utility model possible embodiments, and this embodiment is also not used to limit the scope of the claims of the present utility model, does not allly depart from the equivalence that the utility model does and implements or change, and all should be contained in the scope of the claims of this case.

Claims (2)

1., for the current transformer otherness detection system of uneven testing circuit, comprising two current transformers with contrasting to be detected, it is characterized in that: also comprise variable-frequency power sources and oscillograph; The primary conductive bar of two described current transformers is serially connected in the output loop of variable-frequency power sources mutually; Draw two Secondary Winding from every current transformer, wherein the different name end of a Secondary Winding on a current transformer and a Secondary Winding on another current transformer is connected in parallel and exports on an analysis channel of described oscillograph; The Same Name of Ends parallel connection of two Secondary Winding of two current transformer remainders is connected and exports on another analysis channel of described oscillograph.

2. the current transformer otherness detection system for uneven testing circuit according to claim 1, it is characterized in that: the output loop of described variable-frequency power sources is also serially connected with primary current probe, the output terminal of this primary current probe is connected to described oscillograph.