CN116131227A - Construction method and device of high-sensitivity differential protection criterion based on high voltage low cosine value - Google Patents

Construction method and device of high-sensitivity differential protection criterion based on high voltage low cosine value Download PDF

Info

Publication number
CN116131227A
CN116131227A CN202210908992.2A CN202210908992A CN116131227A CN 116131227 A CN116131227 A CN 116131227A CN 202210908992 A CN202210908992 A CN 202210908992A CN 116131227 A CN116131227 A CN 116131227A
Authority
CN
China
Prior art keywords
phase
criterion
differential protection
zero sequence
low
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202210908992.2A
Other languages
Chinese (zh)
Inventor
郭雅蓉
周泽昕
王兴国
王书扬
刘佳琪
程琪
戴飞扬
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
China Electric Power Research Institute Co Ltd CEPRI
Original Assignee
China Electric Power Research Institute Co Ltd CEPRI
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by China Electric Power Research Institute Co Ltd CEPRI filed Critical China Electric Power Research Institute Co Ltd CEPRI
Priority to CN202210908992.2A priority Critical patent/CN116131227A/en
Publication of CN116131227A publication Critical patent/CN116131227A/en
Pending legal-status Critical Current

Links

Images

Landscapes

  • Emergency Protection Circuit Devices (AREA)

Abstract

The invention discloses a construction method and a device of a high-sensitivity differential protection criterion based on a high voltage low cosine value, comprising the following steps: obtaining voltage phasors on two sides of a line; calculating a cosine value by utilizing the voltage phasors and the included angles between the voltage phasors and the differential current phasors; constructing a non-fault phase identification criterion according to the voltage phasors and the cosine values; constructing a low braking phase differential protection criterion according to the differential current amplitude and the low braking phase differential protection fixed value; constructing a zero sequence differential protection criterion according to the zero sequence differential current amplitude and the zero sequence differential protection braking current fixed value; and constructing a high-sensitivity differential protection criterion by the non-fault phase identification criterion, the low-brake phase difference dynamic protection criterion and the zero sequence differential protection criterion. The problem of the differential protection sensitivity of prior art judgement low is solved.

Description

Construction method and device of high-sensitivity differential protection criterion based on high voltage low cosine value
Technical Field
The invention relates to the technical field of automatic relay protection, in particular to a method and a device for constructing a high-sensitivity differential protection criterion based on a high-voltage low-cosine value.
Background
The current differential protection is widely adopted as the main protection for the line protection in the existing alternating current system. The current differential protection is based on kirchhoff current law, differential current is zero when no fault or out-of-zone fault exists, and the differential current is fault current when in-zone fault exists, so that the sensitivity and reliability are good.
Because the differential current is capacitance current when the transmission line is in normal operation due to the influence of the capacitance to the ground, in order to improve the sensitivity of the current differential protection, the capacitance current needs to be compensated, so that the differential current is zero when the line is fault-free, but the accuracy requirement on the line parameters is higher by capacitance current compensation, so that the key problem of restricting the action performance of the current differential protection is still that the fault current is reduced due to high transition resistance and the magnitude of the line capacitance current is difficult to distinguish, the problem appears more obvious in a weak feed system, even incorrect protection action is possibly caused, and the accident range is enlarged.
Disclosure of Invention
In order to solve the above problems, the present invention provides a method for constructing a high-sensitivity differential protection criterion based on a high-voltage low-cosine value, comprising:
obtaining voltage phasors on two sides of a line; calculating a cosine value by utilizing the voltage phasors and the included angles between the voltage phasors and the differential current phasors;
constructing a non-fault phase identification criterion according to the voltage phasors and the cosine values;
constructing a low braking phase differential protection criterion according to the differential current amplitude and the low braking phase differential protection fixed value;
constructing a zero sequence differential protection criterion according to the zero sequence differential current amplitude and the zero sequence differential protection braking current fixed value;
and constructing a high-sensitivity differential protection criterion by the non-fault phase identification criterion, the low-brake phase difference dynamic protection criterion and the zero sequence differential protection criterion.
Further, obtaining a voltage phasor sum at two sides of the line includes:
Figure BDA0003773351960000011
wherein:
Figure BDA0003773351960000012
for line M side->
Figure BDA0003773351960000013
Phasor of phase voltage>
Figure BDA0003773351960000014
For the line N side->
Figure BDA0003773351960000015
The phase voltage phasors are used to determine,
Figure BDA0003773351960000021
further, calculating a cosine value using the voltage phasors and the angles between the voltage phasors and the differential current phasors includes:
Figure BDA0003773351960000022
wherein:
Figure BDA0003773351960000023
for the line differential current phasor,/v>
Figure BDA0003773351960000024
Figure BDA0003773351960000025
For line M side->
Figure BDA0003773351960000026
Phasor of phase current>
Figure BDA0003773351960000027
For the line N side->
Figure BDA0003773351960000028
Phase current phasors.
Further, according to the voltage phasors and the cosine values, a non-fault phase identification criterion is constructed, including:
Figure BDA0003773351960000029
wherein: u (U) e Is the rated voltage of the line.
Further, according to the differential current amplitude and the low braking phase difference dynamic protection fixed value, constructing a low braking phase differential protection criterion, including:
the low braking phase difference protection criterion is as follows:
Figure BDA00037733519600000210
wherein:
Figure BDA00037733519600000211
for differential current amplitude, I setL And a fixed value is protected for low braking phase difference.
Further, constructing a zero sequence differential protection criterion according to the zero sequence differential current amplitude and the zero sequence differential protection braking current fixed value, including:
the zero sequence differential protection criterion is as follows: i Σ0 ＞I set0 ，
Wherein:
Figure BDA00037733519600000212
is the zero sequence differential current amplitude, I set0 And setting the braking current for homodyne protection.
Further, the method further comprises the following steps:
determining whether the circuit fails according to the high-sensitivity differential protection criterion;
when the line is determined to be faulty, the faulty phase is determined to be faulty.
Further, determining whether the line fails according to the high-sensitivity differential protection criterion includes:
and when the low-braking phase difference protection criterion and the zero sequence differential protection criterion are simultaneously met, determining that the line fails.
Further, when determining that the line fails, determining a failed phase that fails includes:
and after the line fails, determining the failed phase according to the identification criterion of the non-failed phase.
The invention also provides a device for constructing the high-sensitivity differential protection criterion based on the high-voltage low-cosine value, which comprises the following components:
the cosine value calculation unit is used for obtaining the voltage phasor sum of two sides of the line; calculating a cosine value by utilizing the voltage phasors and the included angles between the voltage phasors and the differential current phasors;
the identification criterion construction unit is used for constructing an identification criterion of the non-fault phase according to the voltage phasors and the cosine values;
the low braking phase difference dynamic protection criterion construction unit is used for constructing a low braking phase differential protection criterion according to the differential current amplitude and the low braking phase difference dynamic protection fixed value;
the zero sequence differential protection criterion construction unit is used for constructing a zero sequence differential protection criterion according to the zero sequence differential current amplitude and the zero sequence differential protection braking current fixed value;
and the high-sensitivity differential protection criterion construction unit is used for constructing a high-sensitivity differential protection criterion by the identification criterion of the non-fault phase, the low-braking phase difference dynamic protection criterion and the zero sequence differential protection criterion.
The invention provides a high-sensitivity differential protection criterion construction method and device based on a high-voltage low-cosine value, which can reliably identify a non-fault phase when a high-transition resistor is in fault, can still correctly identify faults outside an area without being influenced by a weak feed system, and can still reliably act in the fault and non-full-phase oscillation process during oscillation, thereby considering the sensitivity and reliability of differential protection and improving the safe and stable operation level of the system.
Drawings
FIG. 1 is a flow chart of a method for constructing a high-sensitivity differential protection criterion based on a high-voltage low-cosine value according to an embodiment of the present invention;
FIG. 2 is a logic diagram of a high sensitivity differential protection criterion according to an embodiment of the present invention;
FIG. 3 is a system diagram of a conventional power access scenario in accordance with an embodiment of the present invention;
FIG. 4 is a differential protection action result of the in-zone fault cross-bar hybrid brake according to an embodiment of the present invention;
FIG. 5 is a differential protection action result of the out-of-zone fault cross-bar hybrid brake according to an embodiment of the present invention;
FIG. 6 is a system diagram of a conventional power access scenario in accordance with an embodiment of the present invention;
FIG. 7 is a differential protection action result of an in-zone fault cross-bar hybrid brake according to an embodiment of the present invention;
FIG. 8 is a differential protection operation result of the out-of-zone fault cross-bar hybrid brake according to an embodiment of the present invention
Fig. 9 is a schematic structural diagram of a high-sensitivity differential protection criterion construction device based on a high-voltage low-cosine value according to an embodiment of the present invention.
Detailed Description
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention may be embodied in many other forms than those herein described, and those skilled in the art will readily appreciate that the present invention may be similarly embodied without departing from the spirit or essential characteristics thereof, and therefore the present invention is not limited to the specific embodiments disclosed below.
Fig. 1 is a flow chart of a method for constructing a high-sensitivity differential protection criterion based on a high-voltage low-cosine value according to an embodiment of the present invention, and the method provided by the present invention is described in detail below with reference to fig. 1.
Step S101, obtaining voltage phasors on two sides of a line; and calculating a cosine value by using the voltage phasors and the included angles between the voltage phasors and the differential current phasors.
The voltage phasor sum is calculated using the voltages on both sides of the line,
Figure BDA0003773351960000041
wherein:
Figure BDA0003773351960000042
for line M side->
Figure BDA0003773351960000043
Phasor of phase voltage>
Figure BDA0003773351960000044
For the line N side->
Figure BDA00037733519600000418
Phasor of phase voltage>
Figure BDA0003773351960000046
Calculating cosine value by utilizing the included angle between the voltage phasors and the differential current phasors on two sides of the line,
Figure BDA0003773351960000047
wherein:
Figure BDA0003773351960000048
for the line differential current phasor,/v>
Figure BDA0003773351960000049
Figure BDA00037733519600000410
For line M side->
Figure BDA00037733519600000411
The phase current phasors are used to determine,
Figure BDA00037733519600000412
for the line N side->
Figure BDA00037733519600000413
Phase current phasors.
And step S102, constructing a non-fault phase identification criterion according to the voltage phasors and the cosine values.
In particular to a special-shaped ceramic tile,
Figure BDA00037733519600000414
wherein: u (U) e Is the rated voltage of the line.
And step S103, constructing a low-braking phase difference dynamic protection criterion according to the differential current amplitude and the low-braking phase difference dynamic protection fixed value.
The low braking phase difference protection criterion is as follows:
Figure BDA00037733519600000415
wherein:
Figure BDA00037733519600000416
for differential current amplitude, I setL And a fixed value is protected for low braking phase difference.
And step S104, constructing a zero sequence differential protection criterion according to the zero sequence differential current amplitude and the zero sequence differential protection braking current fixed value.
The zero sequence differential protection criterion is as follows: i Σ0 ＞I set0 ，
Wherein:
Figure BDA00037733519600000417
is the zero sequence differential current amplitude, I set0 And setting the braking current for homodyne protection.
And step 105, constructing a high-sensitivity differential protection criterion by the identification criterion of the non-fault phase, the low-braking phase difference dynamic protection criterion and the zero sequence differential protection criterion.
Determining whether the circuit fails according to the high-sensitivity differential protection criterion, and particularly, when the low-braking phase difference protection criterion is met simultaneously
Figure BDA0003773351960000051
And zero sequence differential protection criterion->
Figure BDA0003773351960000052
When the line is determined to be faulty;
when the line is determined to be faulty, the faulty phase is determined, specifically, according to the identification criterion of the non-faulty phase, the phase satisfies
Figure BDA0003773351960000053
This phase is a non-faulty phase, whereas it is not satisfied that it is ground, and this term is determined as a faulty phase that has failed.
For example, the circuit includes A, B, C three phases, and according to the logic diagram of the high-sensitivity differential protection criterion shown in fig. 2, whether A, B, C three phases are faulty phases is determined, whether the circuit is faulty is first determined, and then the faulty phases are determined, specifically, when the low-braking phase difference protection criterion is satisfied at the same time
Figure BDA0003773351960000054
And zero sequence differential protection criterion->
Figure BDA0003773351960000055
At this time, it is determined that the line has failed, but at this time, it is not possible to determine which one or ones of the three phases A, B, C have failed. Taking phase A as an example, when phase A meets the identification criterion of non-faulty phase +.>
Figure BDA0003773351960000056
Phase a is a non-faulted phase; on the contrary, when phase A does not meet the identification criterion of non-faulty phase +.>
Figure BDA0003773351960000057
Phase a is a failed phase. Similarly, for phase BAnd whether the C phase is a fault phase is judged.
The specific embodiment selects the following scenarios:
(1) Conventional power supply access scene
The conventional power supply is connected to the line, and the power supplies at both sides of the line are conventional power supplies, and the system diagram is shown in fig. 3, so that the situations of single-phase grounding faults and out-of-zone faults in the line area are discussed respectively.
1) Failure in a zone
The AN single phase in the line area is grounded through 800 omega transition resistor, the protection action condition is shown in figure 4, the phase difference motion protection and zero sequence differential motion protection of the A phase low brake enter the action area for 10.83ms, the high voltage low power factor non-fault phase identification criterion is 1.67ms, the locking is released, and the A phase protection reliably acts. The phase difference protection and the zero sequence differential protection of the B phase and the C low brake are not operated, and the high-voltage low-power factor non-fault phase identification criterion is continuously locked, so that the protection is reliable and is not operated.
2) Out-of-zone failure
When the earth fault of the phase A outside the line occurrence area occurs, the protection action condition is shown in fig. 5, the phase difference protection of the phase A low brake and the zero sequence differential protection do not act, the non-fault phase identification criterion of the high voltage low power factor is 5.83ms, the locking is released, and the phase A protection is comprehensively judged to be reliable and not act. The phase difference protection and the zero sequence differential protection of the B phase and the C phase low brake are not operated, and the high-voltage low-power factor non-fault phase identification criterion is continuously locked, so that the B phase and the C phase are reliably and not operated.
(2) Line side switch off scenario
The most serious weak feed system condition is simulated by using a scene of switching off a line side switch, the system diagram is shown in fig. 6, the switching off of an N side breaker is respectively carried out, faults at a fault point F1 in a region and a fault point F2 outside the region are analyzed, and the protection action condition is as follows.
1) Failure in a zone
AN AN single phase in the line area is grounded through 800 omega transition resistor, the protection action condition is shown in figure 7, the phase difference differential protection of the A phase low brake and the zero sequence differential protection enter the action area for 12.5ms, the high voltage low power factor non-fault phase identification criterion is 13.33ms, the locking is released, and the A phase protection reliably acts. The phase difference protection of the B phase and the C low brake does not act, the zero sequence differential protection acts, but the high voltage low power factor non-fault phase identification criterion is continuously locked, and the protection is reliable and does not act.
(2) Out-of-zone failure
When the earth fault of the phase A outside the line occurrence area occurs, the protection action condition is shown in fig. 8, the phase difference protection of the phase A low brake and the zero sequence differential protection do not act, the non-fault phase identification criterion of the high voltage low power factor is 5ms, the locking is released, and the phase A protection is comprehensively judged to be reliable and not act. The phase difference protection and the zero sequence differential protection of the B phase and the C phase low brake are not operated, and the high-voltage low-power factor non-fault phase identification criterion is continuously locked, so that the B phase and the C phase are reliably and not operated.
Based on the same inventive concept, the present invention also provides a construction device 900 of high-sensitivity differential protection criterion based on high voltage low cosine value, as shown in fig. 9, including:
a cosine value calculating unit 910, configured to obtain a voltage phasor sum of two sides of the line; calculating a cosine value by utilizing the voltage phasors and the included angles between the voltage phasors and the differential current phasors;
a non-fault phase establishing identification criterion construction unit 920, configured to construct a non-fault phase identification criterion according to the voltage phasor sum and the cosine value;
a low braking phase difference dynamic protection criterion construction unit 930, configured to construct a low braking phase differential protection criterion according to the differential current amplitude and the low braking phase difference dynamic protection fixed value;
the zero sequence differential protection criterion construction unit 940 is configured to construct a zero sequence differential protection criterion according to the zero sequence differential current amplitude and the zero sequence differential protection braking current fixed value;
the high-sensitivity differential protection criterion construction unit 950 is configured to construct a high-sensitivity differential protection criterion from the identification criterion of the non-fault phase, the low-brake phase difference dynamic protection criterion and the zero-sequence differential protection criterion.
The invention provides a high-sensitivity differential protection criterion construction method and device based on a high-voltage low-cosine value, which can reliably identify a non-fault phase when a high-transition resistor is in fault, can still correctly identify faults outside an area without being influenced by a weak feed system, and can still reliably act in the fault and non-full-phase oscillation process during oscillation, thereby considering the sensitivity and reliability of differential protection and improving the safe and stable operation level of the system.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that modifications and equivalents may be made to the specific embodiments of the present invention without departing from the spirit and scope of the present invention, and all modifications and equivalents are intended to be included in the scope of the claims of the present invention.

Claims (10)

1. The construction method of the high-sensitivity differential protection criterion based on the high-voltage low-cosine value is characterized by comprising the following steps:
obtaining voltage phasors on two sides of a line; calculating a cosine value by utilizing the voltage phasors and the included angles between the voltage phasors and the differential current phasors;
constructing a non-fault phase identification criterion according to the voltage phasors and the cosine values;
constructing a low braking phase differential protection criterion according to the differential current amplitude and the low braking phase differential protection fixed value;
constructing a zero sequence differential protection criterion according to the zero sequence differential current amplitude and the zero sequence differential protection braking current fixed value;
and constructing a high-sensitivity differential protection criterion by the non-fault phase identification criterion, the low-brake phase difference dynamic protection criterion and the zero sequence differential protection criterion.
2. The method of claim 1, wherein obtaining a voltage phasor sum across the line comprises:
Figure FDA0003773351950000011
wherein:
Figure FDA0003773351950000012
for line M side->
Figure FDA0003773351950000013
Phasor of phase voltage>
Figure FDA0003773351950000014
For the line N side->
Figure FDA0003773351950000015
Phasor of phase voltage>
Figure FDA0003773351950000016
3. The method of claim 1, wherein calculating a cosine value using the voltage phasors and the angle with the differential current phasors comprises:
Figure FDA0003773351950000017
wherein:
Figure FDA0003773351950000018
for the line differential current phasor,/v>
Figure FDA0003773351950000019
Figure FDA00037733519500000110
For line M side->
Figure FDA00037733519500000111
Phasor of phase current>
Figure FDA00037733519500000112
For the line N side->
Figure FDA00037733519500000113
Phase current phasors.
4. The method according to claim 1, wherein constructing a non-faulty phase identification criterion from the voltage phasors and cosine values comprises:
Figure FDA00037733519500000114
wherein: u (U) e Is the rated voltage of the line.
5. The method of claim 1, wherein constructing the low brake phase differential protection criterion based on the differential current magnitude and the low brake phase differential protection setpoint comprises:
the low braking phase difference protection criterion is as follows:
Figure FDA00037733519500000115
wherein:
Figure FDA00037733519500000116
for differential current amplitude, I setL And a fixed value is protected for low braking phase difference.
6. The method of claim 1, wherein constructing the zero sequence differential protection criterion based on the zero sequence differential current magnitude and the zero sequence differential protection braking current setpoint comprises:
the zero sequence differential protection criterion is as follows: i Σ0 ＞I set0 ，
Wherein:
Figure FDA0003773351950000021
is the zero sequence differential current amplitude, I set0 And setting the braking current for homodyne protection.
7. The method as recited in claim 1, further comprising:
determining whether the circuit fails according to the high-sensitivity differential protection criterion;
when the line is determined to be faulty, the faulty phase is determined to be faulty.
8. The method of claim 7, wherein determining whether a line is faulty based on the high sensitivity differential protection criteria comprises:
and when the low-braking phase difference protection criterion and the zero sequence differential protection criterion are simultaneously met, determining that the line fails.
9. The method of claim 7, wherein upon determining that the line has failed, determining the failed phase that has failed comprises:
and after the line fails, determining the failed phase according to the identification criterion of the non-failed phase.
10. The device for constructing the high-sensitivity differential protection criterion based on the high-voltage low-cosine value is characterized by comprising the following components:
the cosine value calculation unit is used for obtaining the voltage phasor sum of two sides of the line; calculating a cosine value by utilizing the voltage phasors and the included angles between the voltage phasors and the differential current phasors;
the identification criterion construction unit is used for constructing an identification criterion of the non-fault phase according to the voltage phasors and the cosine values;
the low braking phase difference dynamic protection criterion construction unit is used for constructing a low braking phase differential protection criterion according to the differential current amplitude and the low braking phase difference dynamic protection fixed value;
the zero sequence differential protection criterion construction unit is used for constructing a zero sequence differential protection criterion according to the zero sequence differential current amplitude and the zero sequence differential protection braking current fixed value;
and the high-sensitivity differential protection criterion construction unit is used for constructing a high-sensitivity differential protection criterion by the identification criterion of the non-fault phase, the low-braking phase difference dynamic protection criterion and the zero sequence differential protection criterion.
CN202210908992.2A 2022-07-29 2022-07-29 Construction method and device of high-sensitivity differential protection criterion based on high voltage low cosine value Pending CN116131227A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202210908992.2A CN116131227A (en) 2022-07-29 2022-07-29 Construction method and device of high-sensitivity differential protection criterion based on high voltage low cosine value

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202210908992.2A CN116131227A (en) 2022-07-29 2022-07-29 Construction method and device of high-sensitivity differential protection criterion based on high voltage low cosine value

Publications (1)

Publication Number Publication Date
CN116131227A true CN116131227A (en) 2023-05-16

Family

ID=86305084

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202210908992.2A Pending CN116131227A (en) 2022-07-29 2022-07-29 Construction method and device of high-sensitivity differential protection criterion based on high voltage low cosine value

Country Status (1)

Country Link
CN (1) CN116131227A (en)

Similar Documents

Publication Publication Date Title
EP2331978B1 (en) Method and device for supervising secondary circuit of instrument transformer in power system
US8842401B2 (en) Protection system for an electrical power network
US8866487B2 (en) Directional fault sectionalizing system
US10333291B2 (en) Multiple generator ground fault detection
US20070070565A1 (en) System, apparatus and method for compensating the sensitivity of a sequence element in a line current differential relay in a power system
CN110783946B (en) Method for locating phase faults in a microgrid
CN109212338B (en) Power island detection method and device and computer readable storage medium
CN108919056B (en) Fault phase judging method and device based on group angular difference
CN104577999B (en) Bus bar protecting method and system based on transient zero-sequence current feature
RU2662639C1 (en) Method of the backup power supply fast switching on and device for its implementation
CN111948467B (en) Capacitor bank internal fault detection method and capacitor protection device
KR20170031564A (en) Apparatus and method detecting direction of fault current
CN109301799B (en) Method and system for preventing multiple-circuit longitudinal zero-sequence direction protection maloperation in same tower
KR101989350B1 (en) Appatus for protecting of microgrid using superimposed reactive energy and method thereof
US9164148B2 (en) Systems and methods for detecting over/under excitation faults
CN115336130A (en) Fault detection in power transmission systems
CN110031716B (en) Distributed fault detection method for power distribution system with resonant grounding
CN116131227A (en) Construction method and device of high-sensitivity differential protection criterion based on high voltage low cosine value
CN109613398B (en) Fault direction discrimination method and discrimination element for high-voltage alternating current-direct current hybrid power grid
CN114094553B (en) Fault protection method, device and equipment of power transmission system and power transmission system
CN100362718C (en) Fault-tolerant complex judging self adaption high voltage parallel reactor turn-to-turn protection
US6501631B1 (en) Method and device for power system protection
CN107436392B (en) Cable single-phase earth fault detection method and system
CN117650479A (en) Optimization method and device for preventing single-phase grounding protection during parallel operation of multiple pump sets
US20030107381A1 (en) Method and device for power system protection

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination