CN109066587B - Converter power transformer differential protection fault judgment method based on wavelet energy entropy - Google Patents

Converter power transformer differential protection fault judgment method based on wavelet energy entropy Download PDF

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CN109066587B
CN109066587B CN201810861962.4A CN201810861962A CN109066587B CN 109066587 B CN109066587 B CN 109066587B CN 201810861962 A CN201810861962 A CN 201810861962A CN 109066587 B CN109066587 B CN 109066587B
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current
wee
energy
entropy
fault
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CN109066587A (en
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林圣�
邓瑜佳
刘磊
何正友
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Southwest Jiaotong University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/04—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers
    • H02H7/045—Differential protection of transformers

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Emergency Protection Circuit Devices (AREA)

Abstract

The present invention discloses a kind of converter power transformer differential protection fault judgment method based on wavelet energy entropy, becomes a secondary side current fault component wavelet energy entropy in troubles inside the sample space based on the change of current, and the otherness of appearance constructs new criterion using two sides wavelet energy entropy ratio；When troubles inside the sample space, corresponding phase two sides wavelet energy entropy ratio is larger；When the change of current, which becomes, to be operated normally, corresponding phase two sides wavelet energy entropy ratio levels off to 1.Method of the invention is not influenced by excitation surge current, D.C. magnetic biasing and CT saturation, and when troubles inside the sample space betides excitation surge current and DC magnetic bias phenomena, can be guaranteed precision maneuver when the change of current becomes troubles inside the sample space, be substantially increased the reliability of traditional longitudinal difference protection.

Description

Converter power transformer differential protection fault judgment method based on wavelet energy entropy
Technical field
The present invention relates to converter power transformer differential protecting technology field, specially a kind of change of current based on wavelet energy entropy becomes Depressor differential protection fault judgment method.
Background technique
Converter power transformer (hereinafter referred to as change of current change) is one of equipment important in electric system, will once breaking down Cause serious economic loss.Currently, the protection of change of current transformer differential is common protected mode in practical engineering application, protect any Malfunction or tripping will all cause the serious damage of equipment, there is unstable phenomenon in the system of even resulting in.
Compared with traditional transformer, converter power transformer local environment harmonic component ingredient is increasingly complex.Some researches show that, by In the nonlinear characteristic of direct current system, when so that excitation surge current or DC magnetic bias phenomena occurring, second harmonic component institute accounting Example reduces, but amplitude is high, and decaying is slow.Therefore, if the change of current becomes troubles inside the sample space and betides change of current change idle-loaded switching-on or direct current During bias, traditional longitudinal difference protection can be latched for a long time due to harmonic component, and it is badly damaged in turn result in equipment for relay fail.
Summary of the invention
In view of the above-mentioned problems, the purpose of the present invention is to provide accurately move when one kind can guarantee that the change of current becomes troubles inside the sample space Make, improves the converter power transformer differential protection breakdown judge side based on wavelet energy entropy of the reliability of traditional longitudinal difference protection Method.Technical solution is as follows:
A kind of converter power transformer differential protection fault judgment method based on wavelet energy entropy, which is characterized in that including such as Lower step:
Step 1: data acquisition and pretreatment:
Fault wave recording device becomes two sides outlet end from the change of current with sample frequency FsAcquire the signal of secondary side A, B, C three-phase iAk(t)、iBk(t)、iCk(t) it is sent to relay, wherein k=1 indicates that the change of current becomes primary side electrical quantity, and k=2 indicates that the change of current becomes 2 Secondary side electrical quantity；T indicates sampling instant；
Step 2: fault component solves:
Two sides electric current phasor difference is calculated in real time, if two sides electric current phasor difference is greater than 0, is calculated the change of current and is become a secondary side A, B, C three-phase current fault component ifPk:
ifPk=iPk(tf)-iPk(tf-△t)(1)
Wherein P=A, B, C respectively indicate A, B, C three-phase；tfCorresponding fault moment, △ t are the moment in sampling interval；
Step 3: extract small echo high frequency coefficient:
The current failure component is subjected to wavelet transformation, extracts corresponding high frequency coefficient:
dPk(j, i)=< ψj,i|ifPk>=∫ ifPk(t)·ψj,idt(2)
Wherein ψj,iFor morther wavelet；
Step 4: calculate wavelet energy entropy:
According to the small echo high frequency coefficient, high-frequency energy under each scale is calculated:
EPk_j=dPk(j,k)2 (3)
Specific time window self-energy summation is calculated according to formula (3):
According to formula (3) and formula (4), the ratio between each Scale energy and gross energy in specific time window are calculated:
According to formula (5), signal energy entropy is calculated are as follows:
Obtain a secondary side three-phase current fault component Energy-Entropy: WeeA1、WeeA2、WeeB1、WeeB2、WeeC1、WeeC2；
Step 5: carry out protection breakdown judge:
According to a secondary side three-phase current fault component Energy-Entropy WeeA1, WeeA2, WeeB1,WeeB2,WeeC1,WeeC2It calculates One secondary side Energy-Entropy ratio:
Take A, B, the maximum value in C three-phase Energy-Entropy ratio is denoted as Rwee=max (RweeA,RweeB,RweeC), after taking failure Data in 10ms calculate Rwee, it is denoted as max { Rwee}；Criterion are as follows:
Wherein, ε is scheduled Energy-Entropy fractional threshold.
It further, further include becoming secondary side fault component Energy-Entropy ratio in judgement event according to the change of current in the step 5 Hinder position: when troubles inside the sample space occurs, opposite variation, secondary side fault component electric current occur for primary side fault component current direction Direction is constant, and notable difference occurs in two sides fault component Energy-Entropy；External area error, or excitation surge current only occurs, or occur straight When flowing other interference phenomenons such as bias, two sides fault component current direction is remained unchanged, two sides fault component Energy-Entropy approximation phase Deng.
The beneficial effects of the present invention are: the present invention is become in a secondary side current fault component wavelet energy entropy area using the change of current Otherness under outer failure constructs Protection criteria, can guarantee precision maneuver when the change of current becomes troubles inside the sample space, and it is vertical poor to improve tradition The reliability of protection；1) it ensure that system under normal operating conditions, protect not malfunction；2) when system only occur excitation surge current or When there is DC magnetic bias phenomena, not malfunction is protected；3) when troubles inside the sample space, action message is protected；Compared with traditional longitudinal difference protection, Advantage is: 1) troubles inside the sample space betides the change of current and becomes in the case of idle-loaded switching-on, protects action message；2) troubles inside the sample space betides directly When flowing bias phenomenon, action message is protected；3) when current sensor (CT) is saturated, not malfunction is protected.
Detailed description of the invention
Attached drawing 1 is that the present invention is based on the converter power transformer differential protection fault judgment method flow charts of wavelet energy entropy.
Attached drawing 2 is the system model figure that simulation example is used.
When Fig. 3 is troubles inside the sample space A phase, a secondary side three-phase fault component wavelet energy entropy schematic diagram.
A phase fault two sides A phase wavelet energy entropy result schematic diagram when the change of current becomes idle-loaded switching-on in the area Tu4Wei.
A phase fault two sides A phase wavelet energy entropy result schematic diagram when DC magnetic bias phenomena in the area Tu5Wei.
Fig. 6 is two sides A phase wavelet energy entropy schematic diagram when CT is saturated.
Specific embodiment
The present invention is described in further details in the following with reference to the drawings and specific embodiments.Fig. 1 is the present embodiment based on small The converter power transformer differential protection fault judgment method flow chart of wave energy entropy, the specific steps are as follows:
Step 1: data acquisition and pretreatment:
Fault wave recording device becomes two sides outlet end from the change of current with sample frequency FsAcquire the signal of secondary side A, B, C three-phase iAk(t)、iBk(t)、iCk(t) it is sent to relay, wherein k=1 indicates that the change of current becomes primary side electrical quantity, and k=2 indicates that the change of current becomes 2 Secondary side electrical quantity；T indicates sampling instant.
Step 2: fault component solves:
According to gained electrical quantity in step 1, two sides electric current phasor difference is calculated in real time, if two sides electric current phasor difference is greater than 0, then it calculates the change of current and becomes secondary side A, B, C three-phase current fault component ifPk:
ifPk=iPk(tf)-iPk(tf-△t) (9)
Wherein P=A, B, C respectively indicate A, B, C three-phase；tfCorresponding fault moment, △ t are the moment in sampling interval.
Step 3: extract small echo high frequency coefficient:
The current failure component is subjected to wavelet transformation, extracts corresponding high frequency coefficient:
dPk(j, i)=< ψj,i|ifPk>=∫ ifPk(t)·ψj,idt (10)
Wherein ψj,iFor morther wavelet.
Step 4: calculate wavelet energy entropy:
According to the small echo high frequency coefficient, high-frequency energy under each scale is calculated:
EPk_j=dPk(j,k)2 (11)
Specific time window self-energy summation is calculated according to formula (3):
According to formula (3) and formula (4), the ratio between each Scale energy and gross energy in specific time window are calculated:
According to formula (5), signal energy entropy is calculated are as follows:
Obtain a secondary side three-phase current fault component Energy-Entropy: WeeA1、WeeA2、WeeB1、WeeB2、WeeC1、WeeC2。
Step 5: carry out protection breakdown judge:
According to a secondary side three-phase current fault component Energy-Entropy WeeA1, WeeA2, WeeB1,WeeB2,WeeC1,WeeC2It calculates One secondary side Energy-Entropy ratio:
Take A, B, the maximum value in C three-phase Energy-Entropy ratio is denoted as Rwee=max (RweeA,RweeB,RweeC), after taking failure In 10ms
Data calculate Rwee, it is denoted as max { Rwee}；Criterion are as follows:
Wherein, ε is scheduled Energy-Entropy fractional threshold.
Also it can become a secondary side fault component Energy-Entropy ratio in judgement abort situation according to the change of current: when troubles inside the sample space occurs When, opposite variation occurs for primary side fault component current direction, and secondary side fault component current direction is constant, two sides fault component There is notable difference in Energy-Entropy；External area error, or other interference phenomenons such as excitation surge current only occurs, or D.C. magnetic biasing occurs When, two sides fault component current direction remains unchanged, and two sides fault component Energy-Entropy is approximately equal.
Emulation experiment
For the feasibility for verifying the converter power transformer differential protection new criterion based on wavelet energy entropy, it is based on PSCAD/ EMTDC, article have built AC/DC Hybrid Transmission System referring to the actual parameter of the wide ± 800kV extra-high voltage direct-current transmission engineering of cloud Model, as shown in Fig. 2.When normal operation, system rectification side uses constant current control, and includes current limiting low-voltage (voltage Dependent current order limit, VDCOL) link.Exchange side, which uses, determines gamma kick.All controls in model System uses PI controller.
When Fig. 3 is troubles inside the sample space A phase, a secondary side three-phase fault component wavelet energy entropy schematic diagram.It can from figure Out, in area when A phase fault, two sides A phase wavelet energy entropy difference is obvious, and two sides B, C two-phase wavelet energy entropy is approximately equal.Table 1 three-phase wavelet energy entropy ratio when giving internal fault external fault.From table it can also be seen that when internal fault external fault, Protection criteria all may be used By movement.
1 internal fault external fault two sides wavelet energy entropy ratio result of table
Fig. 4 gives A phase fault two sides A phase wavelet energy entropy result schematic diagram when the change of current becomes idle-loaded switching-on in area.This When maximum wavelet entropy ratio be 147.2172, protect accurate and reliable movement.
Fig. 5 gives A phase fault two sides A phase wavelet energy entropy result schematic diagram when DC magnetic bias phenomena in area.At this time Maximum wavelet entropy ratio is 158.8241, protects accurate and reliable movement.
Two sides A phase wavelet energy entropy schematic diagram when Fig. 6 gives CT saturation, it is seen that new criterion is not full by CT The influence of sum.

Claims (2)

1. a kind of converter power transformer differential protection fault judgment method based on wavelet energy entropy, which is characterized in that including as follows Step:
Step 1: data acquisition and pretreatment:
Fault wave recording device becomes two sides outlet end from the change of current with sample frequency FsAcquire the signal i of secondary side A, B, C three-phaseAk (t)、iBk(t)、iCk(t) it is sent to relay, wherein k=1 indicates that the change of current becomes primary side electrical quantity, and k=2 indicates that the change of current becomes 2 times Side electrical quantity；T indicates sampling instant；
Step 2: fault component solves:
In real time calculate two sides electric current phasor difference, if two sides electric current phasor difference be greater than 0, calculate the change of current become a secondary side A, B, C three-phase current fault component ifPk:
ifPk=iPk(tf)-iPk(tf-△t) (1)
Wherein P=A, B, C respectively indicate A, B, C three-phase；tfCorresponding fault moment, △ t are the moment in sampling interval；
Step 3: extract small echo high frequency coefficient:
The current failure component is subjected to wavelet transformation, extracts corresponding high frequency coefficient:
dPk(j, i)=< ψj,i|ifPk>=∫ ifPk(t)·ψj,idt (2)
Wherein ψj,iFor morther wavelet；
Step 4: calculate wavelet energy entropy:
According to the small echo high frequency coefficient, high-frequency energy under each scale is calculated:
EPk_j=dPk(j,k)2 (3)
Specific time window self-energy summation is calculated according to formula (3):
According to formula (3) and formula (4), the ratio between each Scale energy and gross energy in specific time window are calculated:
According to formula (5), fault component Energy-Entropy is calculated are as follows:
Obtain a secondary side three-phase current fault component Energy-Entropy: WeeA1、WeeA2、WeeB1、WeeB2、WeeC1、WeeC2；
Step 5: carry out protection breakdown judge:
According to a secondary side three-phase current fault component Energy-Entropy WeeA1, WeeA2, WeeB1,WeeB2,WeeC1,WeeC2Calculate one or two Secondary side Energy-Entropy ratio:
Take A, B, the maximum value in C three-phase Energy-Entropy ratio is denoted as Rwee=max (RweeA,RweeB,RweeC), it takes after failure in 10ms Data calculate Rwee, it is denoted as max { Rwee}；Criterion are as follows:
Wherein, ε is scheduled Energy-Entropy fractional threshold.
2. the converter power transformer differential protection fault judgment method according to claim 1 based on wavelet energy entropy, special Sign is, further includes becoming a secondary side fault component Energy-Entropy ratio in judgement abort situation according to the change of current in the step 5: when When troubles inside the sample space occurs, opposite variation occurs for primary side fault component current direction, and secondary side fault component current direction is constant, There is notable difference in two sides fault component Energy-Entropy；External area error, or excitation surge current only occurs, or D.C. magnetic biasing occurs etc. it When his interference phenomenon, two sides fault component current direction is remained unchanged, and two sides fault component Energy-Entropy is approximately equal.
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CN110133538B (en) * 2019-05-16 2021-03-12 合肥工业大学 Open-circuit fault diagnosis method and experimental platform for ANPC three-level inverter
CN110350492B (en) * 2019-06-19 2020-08-04 华北电力大学 Direction pilot transient state quantity protection method suitable for UPFC-containing power transmission line
CN110350481B (en) * 2019-07-18 2020-04-28 杭州电力设备制造有限公司 Differential protection method, system, equipment and storage medium of transformer
CN110873832A (en) * 2019-11-17 2020-03-10 云南电网有限责任公司临沧供电局 Power distribution network line selection method and system based on wavelet energy entropy
CN113625105B (en) * 2021-07-26 2022-04-29 西南交通大学 Method for identifying internal and external faults of inverter station area based on wavelet energy ratio

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CN203551679U (en) * 2013-08-30 2014-04-16 国家电网公司 Transformer fault diagnosis system based on wavelet transform
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