CN113013853B - Differential current calculation method considering phase-shifting transformer access to power transmission line - Google Patents

Differential current calculation method considering phase-shifting transformer access to power transmission line Download PDF

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CN113013853B
CN113013853B CN202110234105.3A CN202110234105A CN113013853B CN 113013853 B CN113013853 B CN 113013853B CN 202110234105 A CN202110234105 A CN 202110234105A CN 113013853 B CN113013853 B CN 113013853B
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current
phase
differential
shifting transformer
differential relay
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CN113013853A (en
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杨旗
班国邦
文屹
曾华荣
马晓红
吕黔苏
刘君
何荣卜
许逵
陈沛龙
徐舒蓉
李堃
陈竹
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Guizhou Power Grid Co Ltd
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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
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • H02H7/261—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/006—Calibration or setting of parameters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
    • H02H3/28—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at two spaced portions of a single system, e.g. at opposite ends of one line, at input and output of apparatus

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

Abstract

The invention discloses a differential current calculation method considering that a phase-shifting transformer is connected into a power transmission line. Establishing a corresponding relation of parallel division of the input side current and the output side current; calculating the total current flowing through the differential relay under the condition of normal state or external fault of the protection circuit when the phase-shifting transformer string is connected into the protected circuit; calculating and considering the current value of the differential relay flowing under normal state conditions and the current flowing through the differential relay under the internal fault state of the protection circuit under the influence of the phase shift angle of the output side of the phase shifter; calculating and considering the current value of the differential relay flowing in the fault state under the influence of the phase shifting angle of the output side of the phase shifter; the problems of misoperation of a differential current value under normal conditions and misoperation under fault conditions and the like caused by the fact that the phase-shifting transformer is connected to the power transmission line are solved.

Description

Differential current calculation method considering phase-shifting transformer access to power transmission line
Technical Field
The invention relates to the field of relay protection calculation of power transmission lines, in particular to a differential current calculation method considering that a phase-shifting transformer is connected into a power transmission line.
Background
Because the distribution of the power supply at the transmitting end and the load at the receiving end is often far away, the power supply is often transmitted by adopting the construction of an ultra-high voltage transmission line network. However, the problems of overload, heavy load, unreasonable power flow distribution and the like of the part of the circuits are increasingly outstanding, and the phase-shifting transformer is used as power equipment for adjusting the power flow of the alternating current transmission line, so that the phase-shifting transformer gradually becomes the focus of the power system due to the characteristics of simple structure, convenient operation and the like.
The phase-shifting transformer is used as novel power equipment connected in series into a circuit, on one hand, the functional advantages of the phase-shifting transformer in the aspects of eliminating overload and controlling active power flow of a system are exerted, and on the other hand, the novel technical problems are inevitably brought to system protection: the current phase of the input side and the output side of the phase-shifting transformer will have significant change in the fluctuation process of the tapping switch, so that the longitudinal differential protection (the significant change of differential current) of the circuit has misoperation and even failure. Therefore, research is needed to propose a differential current calculation method considering the access of the phase-shifting transformer to the transmission line.
Disclosure of Invention
The invention aims to solve the problems that: the differential current calculation method considering that the phase-shifting transformer is connected to the power transmission line is provided, so that the problems of misoperation of a differential current value under normal conditions, misoperation under fault conditions and the like caused by the fact that the phase-shifting transformer is connected to the power transmission line are solved.
The invention adopts the following technical scheme:
a differential current calculation method considering that a phase-shifting transformer is connected into a power transmission line comprises the following steps:
step 1, when a phase-shifting transformer is connected in series with a tap switch in a line in n-gear, measuring the current of the input side of the phase-shifting transformer
Figure BDA0002959983800000011
And output side current +.>
Figure BDA0002959983800000012
Step 2, calculating a phase difference alpha between the input side current and the output side current of the phase-shifting transformer: establishing input side current
Figure BDA0002959983800000013
And output side current and divide->
Figure BDA0002959983800000014
Corresponding relation of (3);
step 3, calculating the total current flowing through the differential relay under the condition of normal state or external fault of the protection circuit when the phase-shifting transformer is connected in the protected circuit in series
Figure BDA0002959983800000015
Step 4, calculating the current value of the differential relay flowing through the normal state condition under the condition that the line differential relay is influenced by the phase shift angle of the output side of the phase shifter;
step 5, calculating the current flowing through the differential relay in the fault state of the protection circuit when the phase-shifting transformer is connected into the protected circuit
Figure BDA0002959983800000021
And 6, calculating the current value flowing through the differential relay in the fault state under the condition that the line differential relay is influenced by the phase shift angle of the output side of the phase shifter.
Step 7, for current differential protection, i.e. multiplying the left side of the differential relay by the corresponding phase shift angle coefficient e jα Can avoid the offset current caused by the phase shift angleThe method comprises the steps of carrying out a first treatment on the surface of the At this time, the unbalanced current value caused by incomplete consistency of the current transformers at the two sides is as follows:
Figure BDA0002959983800000022
step 8, differential relay differential current
Figure BDA0002959983800000023
The action current takes the value of +.>
Figure BDA0002959983800000024
The protection of the phase-shifting transformer under the access condition can be realized.
The calculation formula of the phase difference alpha in the step 2 is as follows:
Figure BDA0002959983800000025
input side current
Figure BDA0002959983800000026
And output side current and divide->
Figure BDA0002959983800000027
The corresponding relation of (2) is: />
Figure BDA0002959983800000028
Step 3, the total current flowing through the differential relay under the condition of normal state or external fault of the protection circuit
Figure BDA0002959983800000029
The calculation formula of (2) is as follows:
Figure BDA00029599838000000210
wherein:
Figure BDA00029599838000000211
left side current transformer current in normal or external fault condition +.>
Figure BDA00029599838000000212
Right side current transformer current in normal or external fault condition +.>
Figure BDA00029599838000000213
For the output side current of the phase-shifting transformer under normal or external fault conditions, the differential relay current is passed +.>
Figure BDA00029599838000000214
I.e. the offset current under normal conditions.
In the step 4, the formula for calculating the current value flowing through the differential relay under the condition of normal state under the condition that the differential relay of the circuit is influenced by the phase shift angle of the output side of the phase shifter is as follows:
Figure BDA00029599838000000215
the line differential relay is affected by the phase shift angle of the output side of the phase shifter, and the normal offset current of the line is +.>
Figure BDA00029599838000000216
Thus the current transformer value at the left side of the differential relay is multiplied by the phase shift angle coefficient e jα Obtained.
Step 5, the calculated phase-shifting transformer is connected into the protected circuit, and the current flowing through the differential relay in the internal fault state of the protected circuit
Figure BDA0002959983800000031
The calculation formula of (2) is as follows:
Figure BDA0002959983800000032
wherein:
Figure BDA0002959983800000033
is the left side current transformer current in fault state, < >>
Figure BDA0002959983800000034
Is the right side current transformer current in fault state, < >>
Figure BDA0002959983800000035
The output side current of the phase-shifting transformer in the fault state flows through the differential relay current +.>
Figure BDA0002959983800000036
The current is offset for the fault condition.
In the step 6, the formula for calculating the current value flowing through the differential relay in the fault state under the influence of the phase shift angle of the output side of the phase shifter is as follows:
Figure BDA0002959983800000037
the invention has the beneficial effects that:
the invention provides a theoretical calculation method for the current differential protection of a phase-shifting transformer connected with 110kV and above class lines, and the phase-shifting angle factor e is multiplied by the bus current at the output side of the phase-shifting transformer jα Thereby avoiding misoperation of the differential current relay caused by phase-shifting current and realizing normal protection of the circuit; the problems of misoperation of a differential current value under normal conditions and misoperation under fault conditions and the like caused by the fact that the phase-shifting transformer is connected to the power transmission line are solved.
Drawings
Fig. 1 is a schematic diagram of differential current calculation according to the present invention.
Detailed Description
The invention provides a differential current calculation method considering that a phase-shifting transformer is connected into a power transmission line, which comprises the following specific steps:
1) When the measuring phase-shifting transformer is connected in series with the tapping switch in the line in n-gear, the input side electricity of the measuring phase-shifting transformer is measuredFlow of
Figure BDA0002959983800000038
And output side current +.>
Figure BDA0002959983800000039
2) Calculating a phase difference alpha between an input side current and an output side current of the phase-shifting transformer:
Figure BDA00029599838000000310
input side current +.>
Figure BDA00029599838000000313
And output side current and divide->
Figure BDA00029599838000000311
The corresponding relation of (2) is: />
Figure BDA00029599838000000312
3) Calculating the total current flowing through the differential relay under the condition of normal state or external fault of the protection circuit when the phase-shifting transformer is connected into the protected circuit in series
Figure BDA0002959983800000041
The method comprises the following steps: />
Figure BDA0002959983800000042
In the middle of
Figure BDA0002959983800000043
Left side current transformer current in normal or external fault condition +.>
Figure BDA0002959983800000044
Right side current transformer current in normal or external fault condition +.>
Figure BDA0002959983800000045
Is normal or externalPhase-shifting transformer output side current under fault condition, differential relay current>
Figure BDA0002959983800000046
I.e. the offset current under normal conditions.
4) As can be seen from step 3), the line differential relay is affected by the phase shift angle of the output side of the phase shifter, and the normal offset current of the line appears
Figure BDA0002959983800000047
Thus the current transformer value at the left side of the differential relay is multiplied by the phase shift angle coefficient e jα At this time, the differential relay current is +.>
Figure BDA0002959983800000048
5) Calculating the current flowing through the differential relay in the internal fault state of the protection circuit when the phase-shifting transformer is connected into the protected circuit
Figure BDA0002959983800000049
Is->
Figure BDA00029599838000000410
In->
Figure BDA00029599838000000411
Is the left side current transformer current in fault state, < >>
Figure BDA00029599838000000412
Is the right side current transformer current in fault state, < >>
Figure BDA00029599838000000413
The output side current of the phase-shifting transformer in the fault state flows through the differential relay current +.>
Figure BDA00029599838000000414
The current is offset for the fault condition.
6) From the steps ofStep 5) it can be seen that the line differential relay is affected by the phase shift angle of the output side of the phase shifter, and the offset current occurs under the condition of line fault state
Figure BDA00029599838000000415
It is therefore proposed to multiply the value of the current transformer on the left side of the differential relay by the phase shift angle coefficient e jα At this time, the differential relay current flowing in the fault state is:
Figure BDA00029599838000000416
7) Thus for current differential protection, i.e. multiplying the differential relay left by the corresponding phase shift angle coefficient e jα Offset current due to phase shift angle can be avoided. Unbalanced current caused by incomplete consistency of current transformers at two sides at the moment:
Figure BDA00029599838000000417
8) Differential relay differential current
Figure BDA00029599838000000418
The action current takes the value of +.>
Figure BDA00029599838000000419
The protection of the phase-shifting transformer under the access condition can be realized. />

Claims (4)

1. A differential current calculation method considering that a phase-shifting transformer is connected into a power transmission line comprises the following steps:
step 1, when a phase-shifting transformer is connected in series with a tap switch in a line in n-gear, measuring the current of the input side of the phase-shifting transformer
Figure FDA0004129430820000011
And output side current +.>
Figure FDA0004129430820000012
Step 2, calculating a phase difference alpha between the input side current and the output side current of the phase-shifting transformer: establishing input side current
Figure FDA0004129430820000013
And output side current +.>
Figure FDA0004129430820000014
Corresponding relation of (3);
step 3, calculating the total current flowing through the differential relay under the condition of normal state or external fault of the protection circuit when the phase-shifting transformer is connected in the protected circuit in series
Figure FDA0004129430820000015
Figure FDA0004129430820000016
Wherein:
Figure FDA0004129430820000017
left side current transformer current in normal or external fault condition +.>
Figure FDA0004129430820000018
Right side current transformer current in normal or external fault condition +.>
Figure FDA0004129430820000019
For the output side current of the phase-shifting transformer under normal or external fault conditions, the differential relay current is passed +.>
Figure FDA00041294308200000110
Namely, the offset current under normal conditions;
step 4, calculating the current value of the differential relay flowing through the normal state condition under the condition that the line differential relay is influenced by the phase shift angle of the output side of the phase shifter;
Figure FDA00041294308200000111
the line differential relay is affected by the phase shift angle of the output side of the phase shifter, and the normal offset current of the line is +.>
Figure FDA00041294308200000112
Thus, the value of the current transformer at the left side of the differential relay is multiplied by the phase shift angle coefficient e jα Obtaining;
step 5, calculating the current flowing through the differential relay in the fault state of the protection circuit when the phase-shifting transformer is connected into the protected circuit
Figure FDA00041294308200000113
Figure FDA00041294308200000114
Wherein:
Figure FDA0004129430820000021
is the left side current transformer current in fault state, < >>
Figure FDA0004129430820000022
Is the right side current transformer current in the fault condition,
Figure FDA0004129430820000023
the output side current of the phase-shifting transformer in the fault state flows through the differential relay current +.>
Figure FDA0004129430820000024
Offset current for fault conditions;
step 6, calculating the current value flowing through the differential relay in the fault state under the condition that the line differential relay is influenced by the phase shift angle of the output side of the phase shifter;
the calculation considers that the formula of the current value flowing through the differential relay in the fault state under the influence of the phase shift angle of the output side of the phase shifter is as follows:
Figure FDA0004129430820000025
2. the differential current calculation method considering the phase-shifting transformer to be connected to the transmission line according to claim 1, wherein the method comprises the following steps: it also includes: step 7, for current differential protection, i.e. multiplying the left side of the differential relay by the corresponding phase shift angle coefficient e jα The offset current caused by the phase shift angle can be avoided; at this time, the unbalanced current value caused by incomplete consistency of the current transformers at the two sides is as follows:
Figure FDA0004129430820000026
3. the differential current calculation method considering the phase-shifting transformer to be connected to the transmission line according to claim 1, wherein the method comprises the following steps: it also includes: step 8, differential relay differential current
Figure FDA0004129430820000027
The action current takes the value of +.>
Figure FDA0004129430820000028
The protection of the phase-shifting transformer under the access condition can be realized; />
Figure FDA0004129430820000029
And unbalanced current values caused by incomplete consistency of the current transformers at the two sides are obtained.
4. The differential current calculation method considering the phase-shifting transformer to be connected to the transmission line according to claim 1, wherein the method comprises the following steps: the calculation formula of the phase difference alpha in the step 2 is as follows:
Figure FDA00041294308200000210
input side current
Figure FDA0004129430820000031
And output side current +.>
Figure FDA0004129430820000032
The corresponding relation of (2) is: />
Figure FDA0004129430820000033
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* Cited by examiner, † Cited by third party
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JPH08213247A (en) * 1995-02-06 1996-08-20 Hitachi Ltd Transformer for adjusting phase and method for protecting transformer
CN200976489Y (en) * 2006-11-17 2007-11-14 贵阳铝镁设计研究院 Rectifier transformer transverse bracing differential current protection apparatus
CN202840481U (en) * 2012-11-02 2013-03-27 东方日立(成都)电控设备有限公司 Differential protector of phase-shifting transformer
CN103746338A (en) * 2013-12-11 2014-04-23 西安交通大学 Any phase-shifting angle special transformer differential protection method
CN104065038A (en) * 2013-12-06 2014-09-24 国家电网公司 Differential protection method of large-power rectifier transformer set
CN105186452A (en) * 2015-09-10 2015-12-23 南京国电南自电网自动化有限公司 Implementation method for phase-shifting transformer differential protection
CN107123968A (en) * 2017-04-28 2017-09-01 荣信汇科电气技术有限责任公司 A kind of differential protecting method of any phase shifting angle phase-shifting transformer of Multiple coil
CN206977029U (en) * 2017-04-28 2018-02-06 荣信汇科电气技术有限责任公司 A kind of differential protection of any phase shifting angle phase-shifting transformer of plug-in Multiple coil
CN207010209U (en) * 2017-07-07 2018-02-13 南京南瑞继保电气有限公司 A kind of differential protective system suitable for multiple-limb phase-shifting transformer

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8553379B2 (en) * 2009-09-17 2013-10-08 Schweitzer Engineering Laboratories Inc Transformer differential protection

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH08213247A (en) * 1995-02-06 1996-08-20 Hitachi Ltd Transformer for adjusting phase and method for protecting transformer
CN1137157A (en) * 1995-02-06 1996-12-04 株式会社日立制作所 Phase-shifting transformer and protection system of phase-shifting transformer
CN200976489Y (en) * 2006-11-17 2007-11-14 贵阳铝镁设计研究院 Rectifier transformer transverse bracing differential current protection apparatus
CN202840481U (en) * 2012-11-02 2013-03-27 东方日立(成都)电控设备有限公司 Differential protector of phase-shifting transformer
CN104065038A (en) * 2013-12-06 2014-09-24 国家电网公司 Differential protection method of large-power rectifier transformer set
CN103746338A (en) * 2013-12-11 2014-04-23 西安交通大学 Any phase-shifting angle special transformer differential protection method
CN105186452A (en) * 2015-09-10 2015-12-23 南京国电南自电网自动化有限公司 Implementation method for phase-shifting transformer differential protection
CN107123968A (en) * 2017-04-28 2017-09-01 荣信汇科电气技术有限责任公司 A kind of differential protecting method of any phase shifting angle phase-shifting transformer of Multiple coil
CN206977029U (en) * 2017-04-28 2018-02-06 荣信汇科电气技术有限责任公司 A kind of differential protection of any phase shifting angle phase-shifting transformer of plug-in Multiple coil
CN207010209U (en) * 2017-07-07 2018-02-13 南京南瑞继保电气有限公司 A kind of differential protective system suitable for multiple-limb phase-shifting transformer

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