CN103543361A - Frequency-conversion voltage-regulation on-site no-load test method for large extra-high voltage transformer - Google Patents

Abstract

Provided is a frequency-conversion voltage-regulation on-site no-load test method for a large extra-high voltage transformer. An alternating-current test power source, an intermediate transformer and the tested transformer are connected in sequence, one or more sets of high-voltage filters are connected with a primary portion of the tested transformer in parallel, the high-voltage filters are connected with higher-harmonic RLC in series, a high-voltage high-power variable-frequency power source or the output end of the high-voltage high-power variable-frequency power source is connected with a voltage regulator to serve as the alternating-current test power source, and a no-load test is carried out on the tested transformer through frequency regulation operation on the high-voltage high-power alternating-current test power source to achieve carrying out the no-load test of the large transformer on the premises that the capacity of the no-load test power source is not increased, the quality of a no-load voltage waveform is not degraded, and the capacity of the high-voltage filters which are used for carrying out compensation is not changed. According to the frequency-conversion voltage-regulation on-site no-load test method for the large extra-high voltage transformer, the capacity of the test power source needed by the large extra-high voltage transformer is remarkably reduced on the premise that the boosting process is smoothly accomplished, and therefore an extra-high voltage transformer on-site test technology and device are effectively promoted to achieve integration, miniaturization and site practicability.

Description

The extra-high voltage field for Large Transformer no-load test method of frequency conversion voltage adjusting

Technical field

The present invention relates to a kind of transformer field test method, is a kind of extra-high voltage field for Large Transformer no-load test method of frequency conversion voltage adjusting specifically.

Background technology

Large-scale power transformer is one of equipment most important, the most expensive in power transmission and transformation system, and its reliability is directly connected to power system safety and stability operation.Especially in extra-high voltage alternating current-direct current engineering, high-power transformer is as the core of power transmission and transformation system, and status is particularly important.

Before transformer dispatches from the factory or overhaul puts into operation, need carry out on-the-spot no-load test.No-load test can effectively be checked transformer core and inherent vice, is the important technical of evaluating transformer safety, economy, stable operation.Because extra-high voltage transformer volume weight is huge, be difficult for transportation, for saving transportation cost, field for Large Transformer assembling site test will replace the pattern of assembling finished product transportation in traditional factory gradually.

But Assembling site test is also brought new problem, extra-high voltage transformer capacity is large, and electric pressure is high, site test difficulty.Especially in No-load Test of Transformer, after voltage rising core sataration, no-load current sharply increases, and very easily causes trial voltage to reduce and voltage waveform distortion, is difficult to the test of having boosted.Test unit capacity increases, and can reduce the distortion of voltage waveform; But test unit capacity increases, and volume weight is multiplied, and is difficult to rig-site utilization.

At present, the no-load test of high-power transformer mainly adopts two schemes: synchronous generator unit and pressure regulator.Investment on generating unit is huge, reuses difficulty, is difficult to rig-site utilization.It is larger that pressure regulator is affected by power network fluctuation, generally needs compensation just can complete zero load and boost; Conventional compensatory approach is switching high-voltage capacitance after core sataration, to compensate the perceptual weight sharply increasing in no-load current.For extra-high voltage transformer, in no-load test, switching high-voltage capacitance easily produces transient overvoltage, jeopardizes equipment.For extra-high voltage high-power transformer, these test methods are difficult to solve the contradiction demand between test unit capacity and trial voltage waveform, are all not suitable for extra-high voltage transformer site test.

Therefore, need the practicable extra-high voltage field for Large Transformer test method of research, for completing the especially unloaded pressure build-up test of extra-high voltage transformer site test, provide a kind of new solution route, for the construction mode of extra-high voltage equipment Assembling site test provides technical support.

Summary of the invention

Technical matters to be solved by this invention is to provide a kind of extra-high voltage field for Large Transformer no-load test method of frequency conversion voltage adjusting.

The extra-high voltage field for Large Transformer no-load test method of described frequency conversion voltage adjusting, joint test device and tested transformer successively, described test unit connects intermediate transformer by experiment power supply and forms, it is characterized in that: the hv filtering device of connecting at elementary one or more groups higher hamonic wave RLC that is connected in parallel of tested transformer, and using described hv filtering device in no-load test process all the time and the high pressure compensation mode of unique access, using high-voltage variable frequency power source as AC-testing supply, then by the frequency of high-voltage variable frequency power source and output voltage adjustment operation are carried out to the no-load test to tested transformer, to realize, do not increasing no-load test power supply capacity, not deteriorated no-load voltage waveform quality and in the situation that the hv filtering device capacity not changing for compensating carries out high-power transformer no-load test.

The new edition power industry compulsory standard < < electrical safe working order > > regulation of national grid issue: electric pressure 1000V and above be high voltage electric equipment.

The hv filtering device of described higher hamonic wave RLC series connection and low voltage filter or the on high-tension side capacitance compensation wave filter of low-pressure side are distinct, and capacitance compensation needs switching access stage by stage, can produce the risk of transient overvoltage.

Choosing in the following way of described hv filtering device:

One, utilize circuit simulation analysis tool, according to the excitation curve of tested transformer and test loop structure, set up loop analysis model;

Two, change the capacity of hv filtering device, obtain capacity S and the trial voltage U relation curve of test unit required under the hv filtering device compensating coefficient of different capabilities;

Three, relatively connect required test unit capacity S after the hv filtering device of different capabilities maximum value and the stop value in whole process of the test, choose the hv filtering device of the difference minimum of test unit capacity maximum value and stop value.

The described frequency adjustment to high-voltage variable frequency power source is operating as:

One, between 35Hz～45Hz, choose a Frequency point as the initial frequency f of high-voltage variable frequency power source ₀, the output voltage of rising AC-testing supply, boosts in process, the voltage and current of the tested transformer input end of Real-Time Monitoring, and this electric current is as no-load current to be measured; Meanwhile, also need the output current of monitoring test device.

Two, the output current that monitors test unit is by increasing the boundary becoming while reducing as unsaturation unshakable in one's determination stage and wave filter compensating fundamental wave stage, afterwards whenever the electric current that monitors tested transformer input end is when reducing to become stable increase, a cumulative frequency step Δ f on the basis of the existing frequency of high-voltage variable frequency power source, until frequency becomes work frequency value;

When the voltage that three, monitors tested transformer input end reaches the highest trial voltage, stop frequency conversion voltage adjusting process.

As embodiment, the method of the voltage and current of the output current of Real-Time Monitoring intermediate transformer, tested transformer input end is respectively: intermediate transformer outgoing side be connected in series current transformer, tested transformer input end be connected in parallel voltage transformer (VT), at tested transformer input end, be connected in series current transformer, pass through the output current of monitor signal output intermediate transformer and voltage, the electric current of tested transformer input end of connected voltage transformer (VT) summation current transformer.

As a kind of prioritization scheme, described frequency step Δ f gets 0.5Hz～1Hz.

The parameter of resistance, electric capacity, inductance element in the hv filtering device that definite described higher hamonic wave RLC connects as follows:

One, determine the rated voltage U of described hv filtering device _fNwith harmonic wave electric current I _fN:

Rated voltage is calculated with following formula: U _fN=K * U _m,

U in formula _fNfor the rated voltage of hv filtering device, K is safety coefficient, U _mfor the highest trial voltage, getting safety coefficient K is 1.15;

Harmonic current I _fNfor the corresponding harmonic current components of hv filtering device characteristic frequency λ, described hv filtering device characteristic frequency λ is the odd-multiple of tested transformer rated frequency, and described harmonic current components is the corresponding higher harmonic current of tested transformer;

Two, determine the capacity S of hv filtering device _f, quality factor q:

The capacity S of hv filtering device _fwith following formula, calculate:

S _f=U _m×I _fN，

U wherein _mfor the highest trial voltage, I _fNfor the corresponding harmonic current components of filter characteristic frequency lambda;

The span of described quality factor q is 10≤Q≤50;

Three, with following formula, determine respectively capacitance, inductance value, the resistance value of described hv filtering device: $C=\frac{S_f}{2\mathrm{\&pi;f}{U}_{\mathrm{fN}}^2},$

$L=\frac{1}{4{\mathrm{\&pi;}}^2{\mathrm{\&lambda;}}^{2}C},$

$R=\frac{2\mathrm{\&pi;\&lambda;L}}{Q},$

In formula, C is the capacitance of hv filtering device, and L is the inductance value of hv filtering device, and R is the resistance value of hv filtering device, S _ffor the capacity of hv filtering device, U _fNfor the rated voltage of hv filtering device, f is experiment power supply frequency, and λ is the characteristic frequency of hv filtering device, and Q is the quality factor of hv filtering device.

The highest trial voltage provides according to testing regulations (GB) and transformer rated voltage.

The present invention is in the situation that guaranteeing that the process of boosting completes smoothly, significantly reduce the required experiment power supply capacity of extra-high voltage high-power transformer no-load test, and then effectively promote extra-high voltage transformer site test technology and install to integrated, miniaturization, practical future development.

Accompanying drawing explanation

Fig. 1 is extra-high voltage field for Large Transformer test major loop structure schematic diagram,

Fig. 2 is that test unit capacity S and the trial voltage U of no-load test under wave filter compensating action is related to schematic diagram,

Fig. 3 is that under different capabilities wave filter compensating coefficient, required test unit capacity S and trial voltage U are related to schematic diagram,

Fig. 4 is that trial voltage U and the frequency f of frequency conversion voltage adjusting strategy is related to schematic diagram,

Fig. 5 be test unit capacity S while adopting frequency conversion to boost strategy and frequency f with the variation diagram of trial voltage U,

Fig. 6 be the frequency conversion of practical operation boost test unit capacity S tactful and frequency f with the variation diagram of trial voltage U.

Embodiment

Below in conjunction with accompanying drawing, the present invention is further described: as shown in fig. 1, the extra-high voltage field for Large Transformer no-load test method of described frequency conversion voltage adjusting, joint test device 7 and tested transformer 4 successively, described test unit 7 connects intermediate transformer 2 by experiment power supply 1 and forms, it is characterized in that: the hv filtering device 3 of connecting at elementary one or more groups higher hamonic wave RLC that is connected in parallel of tested transformer 4, and using described hv filtering device 3 in no-load test process all the time and the high pressure compensation mode of unique access, using high-voltage variable frequency power source as AC-testing supply, then by the frequency of high-voltage variable frequency power source and output voltage adjustment operation are carried out to the no-load test to tested transformer, to realize, do not increasing no-load test power supply capacity, not deteriorated no-load voltage waveform quality and in the situation that the hv filtering device capacity not changing for compensating carries out high-power transformer no-load test.

Choosing in the following way of described hv filtering device 3:

One, utilize simulation analysis instrument, as PSCAD, Matlab etc., according to the excitation curve of tested transformer 4 and test loop structure, set up loop analysis model;

Two, change the capacity of hv filtering device, obtain capacity S and the trial voltage U relation curve of the test unit under the hv filtering device compensating coefficient of different capabilities;

Three, relatively to complete no-load test required test unit capacity maximum value and stop value under each hv filtering device condition, choose the hv filtering device of the difference minimum of test unit capacity maximum value and stop value.

The described frequency adjustment to high-voltage variable frequency power source is operating as:

One, between 35Hz～45Hz, choose a Frequency point as the initial frequency f of high-voltage variable frequency power source ₀, the output voltage of rising AC-testing supply 1, boosts in process, the voltage and current of tested transformer 4 input ends of Real-Time Monitoring, and this electric current is as no-load current to be measured; Meanwhile, also need the output current of monitoring test device 7.As embodiment, the method of the voltage and current of the output current of Real-Time Monitoring intermediate transformer 2, tested transformer 4 input ends is respectively: intermediate transformer 2 outgoing sides be connected in series current transformer 5, tested transformer 4 input ends be connected in parallel voltage transformer (VT) 6, at tested transformer 4 input ends, be connected in series current transformer 5, pass through the output current of monitor signal output intermediate transformer 2 and voltage, the electric current of tested transformer 4 input ends of connected voltage transformer (VT) 6 summation current transformers 5.

Two, the output current that monitors test unit is by increasing the boundary becoming while reducing as unsaturation unshakable in one's determination stage and wave filter compensating fundamental wave stage, afterwards whenever the electric current that monitors tested transformer 4 input ends is when reducing to become stable increase, a cumulative frequency step Δ f on the basis of the existing frequency of high-voltage variable frequency power source, until frequency becomes work frequency value; As a kind of prioritization scheme, described initial frequency f ₀selection range be 35Hz～45Hz, frequency step Δ f gets 0.5Hz～1Hz.

When the voltage that three, monitors tested transformer 4 input ends reaches the highest trial voltage, termination test process.

For a plurality of low-voltage variable frequency power unit cascades, form experiment power supply 1, output voltage and the frequency energy independent regulation that realizes direct voltage output.Step-up transformer is high-power transformer, and the high-tension effect that hoists in loop jointly forms the required high voltage of test together with high-power variable-frequency power sources.

Hv filtering device 3 is passive filter, resistance, electric capacity, inductance element, consists of.The major function of wave filter is when core sataration no-load current distorts, and compensates perceptual fundamental current, filtering harmonic current, and then improve trial voltage waveform.

As shown in Figure 2, for the no-load test loop of wave filter compensation, along with the increase of trial voltage U, required test unit capacity S is irregular " wave " deformation, is divided into following three phases:

One: in the unsaturated stage of the lower iron core of voltage, the no-load current of tested transformer is very little, and the overwhelming majority is first-harmonic.Now, wave filter becomes the capacitive load of test loop, and except tested transformer impedance, experiment power supply also needs to bear filter impedance, and it is large that experiment power supply capacity becomes, and S rises and progressively increases with U.

Two: when U further increases, the harmonic component in no-load current increases gradually, now wave filter can compensate first-harmonic and divide most of harmonic wave that pours off, and reduces no-load current, can effectively reduce the capacity of required test unit, so S rises and declines with U.

Three: when U further increases, after iron core supersaturation, no-load current sharply increases, the compensating action of wave filter can not be offset no-load current surge effect, and S is also along with U increases and rising rapidly.

Therefore, in whole process, S can exist two higher point: first stage and subordinate phase point of crossing S ₁, the terminal S of phase III ₂.For completing no-load test, the capacity S of test unit ₁and S ₂in large person.

In wave filter when compensation of different capabilities, with the change curve of voltage as shown in Figure 3, S1, S2 in figure, the filter capacity that S3 is corresponding increase required test unit capacity S successively.Filter capacity is less, and the required test unit capacity of iron core unsaturation section is less, test unit capacity required after core sataration larger (as S1 curve in Fig. 3).Otherwise filter capacity is larger, the required test unit capacity of iron core unsaturation section is larger, test unit capacity required after core sataration less (as S2 curve in Fig. 3).S2 curve is between S1 and S3.

As shown in Figure 3, filter capacity selects to want saturated former and later two stages of balanced core simultaneously, makes two higher point S1 close with S2 size (as shown in S2 curve) in S curve, can reach best test compensation effect.

The in the situation that of same capacity wave filter compensation, change no-load test supply frequency, obtain test unit capacity required under different frequency and also can be represented by Fig. 3, now S1, S2, test frequency f corresponding to S3 difference ₁, f ₂, f ₃, and f ₁< f ₂< f ₃.

For further reducing required test unit capacity, the present invention proposes a kind of frequency conversion voltage adjusting method.The main thought of frequency conversion voltage adjusting is to adopt different frequencies in different voltage sections, and frequency increases (being that f is " notch cuttype " rising with U) with voltage, and the variation relation of frequency and voltage as shown in Figure 4.Specifically in lower frequency f ₁lower beginning pressure regulation.Now, iron core does not have saturated, and wave filter is capacitive, and impedance and frequency are inverse ratio, and compensation effect is better, can reduce required maximum experiment power supply capacity S of this stage.When voltage progressively increases iron core and is tending towards saturated, the frequency that progressively raises, makes curve be transitioned into gently upper frequency f ₂under segment of curve; Further rising frequency is transitioned into f ₃under segment of curve.In whole pressure regulation process, required test unit capacity S and frequency f can be represented by Fig. 5 with the variation relation of trial voltage U.As seen from Figure 5, adopt the method for frequency conversion voltage adjusting to complete under the required test unit volume ratio employing single-frequency of whole process of the test little.

For each concrete tested transformer, the feasible frequency conversion voltage adjusting method of practical operation need be determined three parameters, initial frequency f ₀, frequency change step-length △ f, frequency change point.

Because test final frequency is power frequency 50Hz, so initial frequency f ₀must be less than 50Hz, between general desirable 35Hz～45Hz.

The step-length △ f that frequency change regulates is determined by frequency output characteristics and the required frequency conversion voltage adjusting effect of test of variable-frequency power sources.△ f is excessive, can cause adjusting out of true, and the beneficial effect of test reduces; The too small meeting of △ f brings huge experiment work amount.Therefore,, in conjunction with the technical merit of high-power variable-frequency power sources on market, medium frequency of the present invention changes adjusting step-length △ f and is taken as 0.5Hz～1Hz.

The change point of each in notch cuttype change procedure of frequency f is determined by the intersection point (as the U1 in Fig. 5 and U2) of the curve of test unit capacity S under different frequency and trial voltage U.But in actual tests process, the intersections of complex curve under different frequency is difficult to define by effective detection means or analysis means.Therefore, a kind of exercisable method of reality is to get the trough point (as the U ˊ 1 in Fig. 6 and U ˊ 2) that change point is each curve.In this stage, tested transformer core is soon saturated, and the rising of the capacity of required test unit shows as the rapid rising of no-load current.Therefore, in this step-by-step test process, determine that the concrete method of frequency change point is: under this frequency, while utilizing no-load current that mutual inductor or other measurement means monitor to rise, increase the higher Frequency point of frequency arrival; Continue monitoring no-load current, when no-load current starts upper body again, then increase frequency; Until last frequency reaches 50Hz, complete frequency conversion voltage adjusting process.

In sum, in the situation that tested transformer capacity is large, electric pressure is very high, take the method for " notch cuttype " frequency conversion voltage adjusting can avoid the risk because trial voltage is difficult to go up in the too small situation of test unit finite capacity, impedance loop.In the no-load test of high-power variable-frequency power sources and wave filter compensation, the strategy of employing frequency conversion voltage adjusting can significantly reduce the capacity of experiment power supply, guarantees that the process of boosting completes smoothly.Therefore, the present invention, for the on-the-spot no-load test of extra-high voltage transformer provides a kind of new effective test method, can effectively promote extra-high voltage transformer experimental technique and device to integrated, miniaturization, practical future development.

Claims (6)

1. the extra-high voltage field for Large Transformer no-load test method of a frequency conversion voltage adjusting, joint test device (7) and tested transformer (4) successively, described test unit (7) connects intermediate transformer (2) by experiment power supply (1) and forms, it is characterized in that: the hv filtering device (3) of connecting at elementary one or more groups higher hamonic wave RLC that is connected in parallel of tested transformer (4), and using described hv filtering device (3) in no-load test process all the time and the high pressure compensation mode of unique access, using high-voltage variable frequency power source as AC-testing supply, then by the frequency of high-voltage variable frequency power source and output voltage adjustment operation are carried out to the no-load test to tested transformer, to realize, do not increasing no-load test power supply capacity, not deteriorated no-load voltage waveform quality and in the situation that the hv filtering device capacity not changing for compensating carries out high-power transformer no-load test.

2. the extra-high voltage field for Large Transformer no-load test method of frequency conversion voltage adjusting according to claim 1, is characterized in that: the choosing in the following way of described hv filtering device (3):

One, utilize circuit simulation analysis tool, according to the excitation curve of tested transformer (4) and test loop structure, set up loop analysis model;

Two, change the capacity of hv filtering device, obtain capacity S and the trial voltage U relation curve of test unit (7) required under the hv filtering device compensating coefficient of different capabilities;

Three, relatively connect required test unit (7) capacity S after the hv filtering device of different capabilities maximum value and the stop value in whole process of the test, choose the hv filtering device of the difference minimum of test unit capacity maximum value and stop value.

3. the extra-high voltage field for Large Transformer no-load test method of frequency conversion voltage adjusting according to claim 1, is characterized in that: the described frequency adjustment to high-voltage variable frequency power source is operating as:

One, between 35Hz～45Hz, choose a Frequency point as the initial frequency f of high-voltage variable frequency power source ₀, the output voltage of rising AC-testing supply (1), boosts in process, the voltage and current of the tested transformer of Real-Time Monitoring (4) input end, and this electric current is as no-load current to be measured; Meanwhile, also need the output current of monitoring test device (7).

Two, the output current that monitors test unit is by increasing the boundary becoming while reducing as unsaturation unshakable in one's determination stage and wave filter compensating fundamental wave stage, afterwards whenever the electric current that monitors tested transformer (4) input end is when reducing to become stable increase, a cumulative frequency step Δ f on the basis of the existing frequency of high-voltage variable frequency power source, until frequency becomes work frequency value;

When the voltage that three, monitors tested transformer (4) input end reaches the highest trial voltage, stop frequency conversion voltage adjusting process.

4. the extra-high voltage field for Large Transformer no-load test method of frequency conversion voltage adjusting according to claim 3, it is characterized in that: the output current of Real-Time Monitoring intermediate transformer (2), the method of the voltage and current of tested transformer (4) input end is respectively: at intermediate transformer (2) outgoing side, be connected in series current transformer (5), at tested transformer (4) the input end voltage transformer (VT) (6) that is connected in parallel, at tested transformer (4) input end, be connected in series current transformer (5), pass through the output current of monitor signal output intermediate transformer (2) and the voltage of tested transformer (4) input end of connected voltage transformer (VT) (6) summation current transformer (5), electric current.

5. the extra-high voltage field for Large Transformer no-load test method of frequency conversion voltage adjusting according to claim 3, is characterized in that: described frequency step Δ f gets 0.5Hz～1Hz.

6. the extra-high voltage field for Large Transformer no-load test method of frequency conversion voltage adjusting according to claim 1, is characterized in that: the parameter of determining as follows resistance, electric capacity, inductance element in the hv filtering device of described higher hamonic wave RLC series connection:

One, determine the rated voltage U of described hv filtering device _fNwith harmonic wave electric current I _fN:

Rated voltage is calculated with following formula: U _fN=K * U _m,

U in formula _fNfor the rated voltage of hv filtering device, K is safety coefficient, U _mfor the highest trial voltage, getting safety coefficient K is 1.15;

Harmonic current I _fNfor the corresponding harmonic current components of hv filtering device characteristic frequency λ, described hv filtering device characteristic frequency λ is the odd-multiple of tested transformer rated frequency, and described harmonic current components is the corresponding higher harmonic current of tested transformer;

Two, determine the capacity S of hv filtering device _f, quality factor q:

The capacity S of hv filtering device _fwith following formula, calculate:

S _f=U _m×I _fN，

U wherein _mfor the highest trial voltage, I _fNfor the corresponding harmonic current components of filter characteristic frequency lambda;

The span of described quality factor q is 10≤Q≤50;

Three, with following formula, determine respectively capacitance, inductance value, the electricity of described hv filtering device

Resistance: $C=\frac{S_f}{2\mathrm{\&pi;f}{U}_{\mathrm{fN}}^2},$

$L=\frac{1}{4{\mathrm{\&pi;}}^2{\mathrm{\&lambda;}}^{2}C},$

$R=\frac{2\mathrm{\&pi;\&lambda;L}}{Q},$

In formula, C is the capacitance of hv filtering device, and L is the inductance value of hv filtering device, and R is the resistance value of hv filtering device, S _ffor the capacity of hv filtering device, U _fNfor the rated voltage of hv filtering device, f is experiment power supply frequency, and λ is the characteristic frequency of hv filtering device, and Q is the quality factor of hv filtering device.

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