CN113013853A - Differential current calculation method considering phase-shifting transformer to be connected to power transmission line - Google Patents

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

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CN113013853A
CN113013853A CN202110234105.3A CN202110234105A CN113013853A CN 113013853 A CN113013853 A CN 113013853A CN 202110234105 A CN202110234105 A CN 202110234105A CN 113013853 A CN113013853 A CN 113013853A
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current
phase
differential
calculating
transformer
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CN113013853B (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 calculating method considering that a phase-shifting transformer is connected into a power transmission line. Establishing a parallel corresponding relation of the input side current and the output side current; calculating the total current of the differential relay flowing through the protection circuit under the normal state or external fault condition when the phase-shifting transformer is connected into the protected circuit in series; calculating and considering the current value of the differential relay flowing through the normal state under the influence of the phase angle of the phase shifter output side of the line differential relay and the current flowing through the differential relay under the internal fault state of the protection line; calculating and considering the current value of the differential relay flowing through the fault state under the influence of the phase angle of the output side of the phase shifter of the line differential relay; the problems that the differential current value is mistakenly operated under the normal condition and the fault condition and the like caused by the fact that the phase-shifting transformer is connected into the power transmission line are solved.

Description

Differential current calculation method considering phase-shifting transformer to be connected to power transmission line
Technical Field
The invention relates to the field of power transmission line relay protection calculation, 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 sending end power supply and the receiving end load is often far away, the power supply sending is often constructed by adopting an ultra-high voltage transmission line network. However, the problems of overload, heavy load, unreasonable tidal current distribution and the like of some lines are increasingly prominent, and the phase-shifting transformer as power equipment for regulating the tidal current of the alternating-current power transmission line gradually becomes a key point of attention of a power system due to the characteristics of simple structure, convenience in operation and the like.
As novel power equipment connected in series with an incoming line, the phase-shifting transformer plays the functional advantages of the phase-shifting transformer in the aspects of eliminating overload and controlling the active power flow of a system on one hand, and brings new technical problems to the system protection inevitably on the other hand: the current phases of the input side and the output side of the phase-shifting transformer are obviously changed in the fluctuation process of the tap switch, so that the longitudinal differential protection (the differential current is obviously changed) of the circuit is subjected to misoperation and even failure. Therefore, it is necessary to research and propose a differential current calculation method considering the access of the phase-shifting transformer to the power transmission line.
Disclosure of Invention
The invention aims to solve the problems that: the method for calculating the differential current considering the access of the phase-shifting transformer to the power transmission line is provided, so that the problems of differential current value misoperation under normal conditions, misoperation under fault conditions and the like caused by the access of the phase-shifting transformer to the power transmission line are solved.
The technical scheme adopted by the invention is as follows:
a differential current calculation method considering that a phase-shifting transformer is connected to a power transmission line comprises the following steps:
step 1, measuring the current of the input side of the phase-shifting transformer when the phase-shifting transformer is connected in series with a tap switch in a line at n gear
Figure BDA0002959983800000011
And output side current
Figure BDA0002959983800000012
Step 2, calculating the phase difference alpha between the input side current and the output side current of the phase-shifting transformer: establishing an input side current
Figure BDA0002959983800000013
Is divided into two with output side current
Figure BDA0002959983800000014
The corresponding relationship of (a);
step 3, calculating the total current of the differential relay flowing through the phase-shifting transformer when the phase-shifting transformer is connected into the protected circuit in series and the protected circuit is in a normal state or under the condition of external fault
Figure BDA0002959983800000015
Step 4, calculating and considering the current value of the differential relay flowing through the normal state under the influence of the phase angle of the phase shifter output side of the line differential relay;
step 5, calculating the current flowing through the differential relay under the internal fault state of the protection circuit when the phase-shifting transformer is connected into the protected circuit
Figure BDA0002959983800000021
And 6, calculating and considering the current value of the differential relay flowing under the fault state when the line differential relay is influenced by the phase angle of the phase shifter output side.
Step 7, for current differential protection, namely multiplying the left side of the differential relay by a corresponding phase shift angle coefficient ejαSo as to avoid the offset current caused by the phase shift angle; the unbalanced current value caused by the incomplete consistency of the current transformers on the two sides is as follows:
Figure BDA0002959983800000022
step 8, differential relay differential current
Figure BDA0002959983800000023
The action current takes the value as
Figure BDA0002959983800000024
The protection under the condition of the access of the phase-shifting transformer can be realized.
Step 2, the calculation formula of the phase difference alpha is as follows:
Figure BDA0002959983800000025
input side current
Figure BDA0002959983800000026
Is divided into two with output side current
Figure BDA0002959983800000027
The corresponding relation is as follows:
Figure BDA0002959983800000028
step 3, under the condition of normal state or external fault of the protection circuit, total current flows through the differential relay
Figure BDA0002959983800000029
The calculation formula of (2) is as follows:
Figure BDA00029599838000000210
in the formula:
Figure BDA00029599838000000211
the left side current transformer current is normal or under external fault conditions,
Figure BDA00029599838000000212
the right side current transformer current under normal or external fault conditions,
Figure BDA00029599838000000213
for shifting the output side current of the phase transformer under normal or external fault conditions, a differential relay current is passed
Figure BDA00029599838000000214
I.e. the offset current in the normal case.
Step 4, the formula for calculating the current value of the differential relay flowing through the normal state under the influence of the phase angle of the phase shifter output side under the consideration of the line differential relay is as follows:
Figure BDA00029599838000000215
the line differential relay is influenced by the phase angle of the output side of the phase shifter and has the normal offset current of the line
Figure BDA00029599838000000216
Thus multiplying the current transformer value on the left side of the differential relay by the phase shift angle factor ejαThus obtaining the product.
Step 5, calculating the current flowing through the differential relay under the internal fault state of the protection circuit when the phase-shifting transformer is connected into the protected circuit
Figure BDA0002959983800000031
The calculation formula of (2) is as follows:
Figure BDA0002959983800000032
in the formula:
Figure BDA0002959983800000033
is the current of the left current transformer in a fault state,
Figure BDA0002959983800000034
is the current of the current transformer on the right side in a fault state,
Figure BDA0002959983800000035
the current on the output side of the phase transformer flows through the differential relay in order to shift down the phase transformer in a fault state
Figure BDA0002959983800000036
The current is offset for a fault condition.
Step 6, the formula for calculating the current value of the differential relay flowing under the fault state under the influence of the phase shift angle of the phase shifter output side of the line differential relay 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 the phase-shifting transformer accessed to the line with the voltage of 110kV and above, which multiplies the bus current at the output side of the phase-shifting transformer by the phase-shifting angleFactor ejαFurther, the misoperation of a differential current relay caused by phase-shift current is avoided, and a normal protection circuit is realized; the problems that the differential current value is mistakenly operated under the normal condition and the fault condition and the like caused by the fact that the phase-shifting transformer is connected into 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) measuring the input side current of the phase-shifting transformer when the phase-shifting transformer is serially connected in the n-level of the tap switch in the line
Figure BDA0002959983800000038
And output side current
Figure BDA0002959983800000039
2) Calculating the phase difference alpha between the input side current and the output side current of the phase-shifting transformer:
Figure BDA00029599838000000310
the input side current
Figure BDA00029599838000000313
Is divided into two with output side current
Figure BDA00029599838000000311
The corresponding relation is as follows:
Figure BDA00029599838000000312
3) calculating the total current of the phase-shifting transformer connected to the protected line and flowing through the differential relay under the condition of normal state or external fault of the protected line
Figure BDA0002959983800000041
Comprises the following steps:
Figure BDA0002959983800000042
in the formula
Figure BDA0002959983800000043
The left side current transformer current is normal or under external fault conditions,
Figure BDA0002959983800000044
the right side current transformer current under normal or external fault conditions,
Figure BDA0002959983800000045
for shifting the output side current of the phase transformer under normal or external fault conditions, a differential relay current is passed
Figure BDA0002959983800000046
I.e. the offset current in the normal case.
4) Step 3) shows that the line differential relay is influenced by the phase angle of the output side of the phase shifter and appears in the line normal offset current
Figure BDA0002959983800000047
Thus multiplying the current transformer value on the left side of the differential relay by the phase shift angle factor ejαWhen the current flowing through the differential relay for the normal state condition is
Figure BDA0002959983800000048
5) Calculating the current flowing through the differential relay in the state of internal fault of the protection circuit when the phase-shifting transformer is connected into the protected circuit
Figure BDA0002959983800000049
Is composed of
Figure BDA00029599838000000410
In the formula
Figure BDA00029599838000000411
Is the current of the left current transformer in a fault state,
Figure BDA00029599838000000412
is the current of the current transformer on the right side in a fault state,
Figure BDA00029599838000000413
the current on the output side of the phase transformer flows through the differential relay in order to shift down the phase transformer in a fault state
Figure BDA00029599838000000414
The current is offset for a fault condition.
6) Step 5) shows that the line differential relay is influenced by the phase angle of the output side of the phase shifter and deflects current under the condition of line fault state
Figure BDA00029599838000000415
Thus, it is proposed that the value of the current transformer on the left side of the differential relay is multiplied by the phase shift angle coefficient ejαThe current through the differential relay for the fault condition at this time is:
Figure BDA00029599838000000416
7) for current differential protection, i.e. multiplication by the corresponding phase-shifting factor e on the left side of the differential relayjαThus, the offset current caused by the phase shift angle can be avoided. Unbalanced current caused by incomplete consistency of current transformers on two sides at the moment:
Figure BDA00029599838000000417
8) differential relay differential current
Figure BDA00029599838000000418
The action current takes the value as
Figure BDA00029599838000000419
The protection under the condition of the access of the phase-shifting transformer can be realized.

Claims (8)

1. A differential current calculation method considering that a phase-shifting transformer is connected to a power transmission line comprises the following steps:
step 1, measuring the current of the input side of the phase-shifting transformer when the phase-shifting transformer is connected in series with a tap switch in a line at n gear
Figure FDA0002959983790000014
And output side current
Figure FDA0002959983790000015
Step 2, calculating the phase difference alpha between the input side current and the output side current of the phase-shifting transformer: establishing an input side current
Figure FDA0002959983790000016
Is divided into two with output side current
Figure FDA0002959983790000017
The corresponding relationship of (a);
step 3, calculating the total current of the differential relay flowing through the phase-shifting transformer when the phase-shifting transformer is connected into the protected circuit in series and the protected circuit is in a normal state or under the condition of external fault
Figure FDA0002959983790000018
Step 4, calculating and considering the current value of the differential relay flowing through the normal state under the influence of the phase angle of the phase shifter output side of the line differential relay;
step 5, calculating the current flowing through the differential relay under the internal fault state of the protection circuit when the phase-shifting transformer is connected into the protected circuit
Figure FDA0002959983790000019
And 6, calculating and considering the current value of the differential relay flowing under the fault state when the line differential relay is influenced by the phase angle of the phase shifter output side.
2. The method for calculating the differential current of the phase-shifting transformer connected to the power transmission line according to claim 1, wherein the method comprises the following steps: it still includes: step 7, for current differential protection, namely multiplying the left side of the differential relay by a corresponding phase shift angle coefficient ejαSo as to avoid the offset current caused by the phase shift angle; the unbalanced current value caused by the incomplete consistency of the current transformers on the two sides is as follows:
Figure FDA0002959983790000011
3. the method for calculating the differential current of the phase-shifting transformer connected to the power transmission line according to claim 1, wherein the method comprises the following steps: it still includes: step 8, differential relay differential current
Figure FDA0002959983790000012
The action current takes the value as
Figure FDA0002959983790000013
The protection under the condition of the access of the phase-shifting transformer can be realized.
4. The method for calculating the differential current of the phase-shifting transformer connected to the power transmission line according to claim 1, wherein the method comprises the following steps: step 2, the calculation formula of the phase difference alpha is as follows:
Figure FDA0002959983790000021
input side current
Figure FDA0002959983790000022
Is divided into two with output side current
Figure FDA0002959983790000023
The corresponding relation is as follows:
Figure FDA0002959983790000024
5. the method for calculating the differential current of the phase-shifting transformer connected to the power transmission line according to claim 1, wherein the method comprises the following steps: step 3, under the condition of normal state or external fault of the protection circuit, total current flows through the differential relay
Figure FDA0002959983790000025
The calculation formula of (2) is as follows:
Figure FDA0002959983790000026
in the formula:
Figure FDA0002959983790000027
the left side current transformer current is normal or under external fault conditions,
Figure FDA0002959983790000028
the right side current transformer current under normal or external fault conditions,
Figure FDA0002959983790000029
for shifting the output side current of the phase transformer under normal or external fault conditions, a differential relay current is passed
Figure FDA00029599837900000210
I.e. the offset current in the normal case.
6. The method for calculating the differential current of the phase-shifting transformer connected to the power transmission line according to claim 1, wherein the method comprises the following steps: step 4, calculating and considering that the line differential relay flows through the differential under the influence of the phase shifting angle of the output side of the phase shifter to the normal state conditionThe formula of the current value of the relay is as follows:
Figure FDA00029599837900000211
the line differential relay is influenced by the phase angle of the output side of the phase shifter and has the normal offset current of the line
Figure FDA00029599837900000212
Thus multiplying the current transformer value on the left side of the differential relay by the phase shift angle factor ejαThus obtaining the product.
7. The method for calculating the differential current of the phase-shifting transformer connected to the power transmission line according to claim 1, wherein the method comprises the following steps: step 5, calculating the current flowing through the differential relay under the internal fault state of the protection circuit when the phase-shifting transformer is connected into the protected circuit
Figure FDA00029599837900000213
The calculation formula of (2) is as follows:
Figure FDA00029599837900000214
in the formula:
Figure FDA00029599837900000215
is the current of the left current transformer in a fault state,
Figure FDA00029599837900000216
is the current of the current transformer on the right side in a fault state,
Figure FDA00029599837900000217
the current on the output side of the phase transformer flows through the differential relay in order to shift down the phase transformer in a fault state
Figure FDA0002959983790000031
Offsetting power for fault conditionsAnd (4) streaming.
8. The method for calculating the differential current of the phase-shifting transformer connected to the power transmission line according to claim 1, wherein the method comprises the following steps: step 6, the formula for calculating the current value of the differential relay flowing under the fault state under the influence of the phase shift angle of the phase shifter output side of the line differential relay is as follows:
Figure FDA0002959983790000032
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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
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
US20110063761A1 (en) * 2009-09-17 2011-03-17 Kasztenny Bogdan Z Transformer Differential Protection
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

Patent Citations (11)

* 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
US20110063761A1 (en) * 2009-09-17 2011-03-17 Kasztenny Bogdan Z Transformer Differential Protection
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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