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CN-121986426-A - Power system line distance protection based on setpoint voltage calculation

CN121986426ACN 121986426 ACN121986426 ACN 121986426ACN-121986426-A

Abstract

The present disclosure relates to a method for controlling or protecting an electrical transmission line within an electrical system comprising the electrical transmission line, the method comprising obtaining a measurement of at least one first electrical parameter measured at a first location on the electrical transmission line of the electrical system, determining at least one second electrical parameter of a second location on the electrical transmission line of the electrical system in a time domain based on the measurement of the at least one first electrical parameter, determining at least one third electrical parameter of the second location on the electrical transmission line of the electrical system in a frequency domain based on the at least one second electrical parameter, and controlling or protecting the electrical transmission line within the electrical system based on the at least one third electrical parameter.

Inventors

  • WANG JIANPING
  • LI YOUYI
  • Zoran gagic

Assignees

  • 日立能源有限公司

Dates

Publication Date
20260505
Application Date
20241106
Priority Date
20231110

Claims (11)

  1. 1. A method for controlling an electrical system comprising a transmission line, the method comprising: obtaining a measured value of at least one first electrical parameter measured at a first location on the power line of the electrical system; Determining at least one second electrical parameter of a second location on the power line of the electrical system in the time domain based on the measured value of the at least one first electrical parameter; Determining at least one third electrical parameter of the second location on the power line of the electrical system in the frequency domain based on the at least one second electrical parameter, and Controlling or protecting the transmission line of the electrical system based on the at least one third electrical parameter, Wherein determining the at least one second electrical parameter comprises solving at least one time-domain differential equation, and/or determining the at least one third electrical parameter comprises transforming the at least one second electrical parameter in the time domain to the frequency domain, and/or Wherein the transmission line comprises a plurality of phases carried along the transmission line, and Wherein the at least one first electrical parameter is the current and/or the voltage of the respective plurality of phases, the at least one second electrical parameter is the voltage of the respective plurality of phases at the setpoint, and/or the at least one third electrical parameter is the sequence voltage of the respective plurality of sequence voltages at the setpoint.
  2. 2. The method of claim 1, further comprising: Determining that an internal fault has occurred based on the at least one third electrical parameter and at least one preset condition, and The transmission line within the electrical system is controlled or protected further based on the determined occurrence of the internal fault.
  3. 3. The method of any one of claims 1 or 2, further comprising: determining a fault location based on the at least one third electrical parameter and at least one preset condition, and The electrical system is controlled further based on the determined fault location.
  4. 4. A method as claimed in any one of claims 1 to 3, further comprising: Determining at least one of the plurality of phases that is involved in the fault based on the at least one third electrical parameter, and The transmission line of the electrical system is controlled or protected further based on the determined at least one phase related to the fault.
  5. 5. The method of any one of claims 1 to 4, wherein the fault is any one of a phase-to-ground fault, an interphase fault, and an interphase-to-ground fault.
  6. 6. The method according to claim 1 to 5, wherein, The electrical system comprises a transmission line protection system located within the electrical system, wherein the transmission line protection system preferably comprises a relay, in particular a distance relay, and Controlling or protecting the transmission line of the electrical system comprises controlling the transmission line protection system, in particular tripping the transmission line protection system, based on a control signal generated according to the at least one third electrical parameter.
  7. 7. The method of any one of claims 1 to 6, wherein the second location is different from the first location.
  8. 8. The method according to any one of claims 1 to 7, wherein controlling or protecting the transmission line of the electrical system based on the at least one third electrical parameter comprises protecting the electrical system based on the at least one third electrical parameter, preferably comprising issuing a trip command to a corresponding circuit breaker and thereby isolating a respective fault.
  9. 9. An apparatus for controlling or protecting an electrical system including the electrical transmission line, the apparatus comprising a processor configured to: obtaining a measured value of at least one first electrical parameter measured at a first location on the power line of the electrical system; Determining at least one second electrical parameter of a second location on the power line of the electrical system in the time domain based on the measured value of the at least one first electrical parameter; Determining at least one third electrical parameter of the second location on the power line of the electrical system in the frequency domain based on the at least one second electrical parameter, and Controlling or protecting the transmission line of the electrical system based on the at least one third electrical parameter; wherein determining the at least one second electrical parameter in the time domain comprises solving at least one time-domain differential equation, and/or determining the at least one third electrical parameter in the frequency domain comprises transforming the at least one second electrical parameter in the time domain into the frequency domain, and/or Wherein the transmission line comprises a plurality of phases carried along the transmission line, and Wherein the at least one first electrical parameter is the current and/or the voltage of the respective plurality of phases, the at least one second electrical parameter is the voltage of the respective plurality of phases at the setpoint, and/or the at least one third electrical parameter is the sequence voltage of the respective plurality of sequence voltages at the setpoint.
  10. 10. The device of claim 9, wherein the processor is configured to perform the method of any one of claims 1 to 8.
  11. 11. A system for controlling or protecting an electrical system comprising the electrical system, the system comprising the electrical system and the apparatus of claim 9 or 10.

Description

Power system line distance protection based on setpoint voltage calculation Technical Field The present disclosure relates to a method, apparatus and system for controlling and protecting an electrical system including a transmission line. Background In electrical systems comprising transmission lines, it is important to accurately identify the type of fault in order to take further corrective action. Among them, distance protection is widely used for protecting a power transmission line. However, as the use of variable renewable sources increases, conventional approaches encounter challenges in processing measurements due to fault current waveform distortion or higher harmonic components, especially for transmission lines connected to Doubly Fed Induction Generators (DFIGs). The basic principles of distance protection and conventional methods used therewith are briefly discussed below. Traditionally, distance protection has relied on the calculation of the impedance of the line under test, which reflects the positive sequence impedance of the power transmission line under test. The calculation is based on ohm's law as follows: impedance measurements there may be two types of computational loops, 1) phase-to-ground loop based and 2) phase-to-phase loop based measurements. The phase-to-ground loop impedance may be calculated as follows: (1) Wherein, the V PG denotes the phase-to-ground voltage measured at the relay location of the transmission line, I PG represents the phase-to-ground loop current measured at the relay location of the transmission line, such as I A、IB、IC, I 0 denotes the zero sequence current measured from the three phase current, i.e.,, K 0 represents a compensation factor, for example,, Z 0 represents the zero sequence impedance as seen from the relay position to the end of the protected zone, and Z 1 represents the positive sequence impedance seen from the relay position to the end of the protected zone. The inter-phase loop impedance may be calculated as follows. (2) Wherein V Phase,1 and V Phase,2 represent phase-to-ground voltages measured at relay locations of the power transmission line, such as V A and V B、VB and V C, and V C and V A, and wherein I Phase,1 and I Phase,2 represent phase-to-ground voltages measured at relay locations of the power transmission line, such as I A and I B、IB and I C, and I C and I A. As is evident from the above equations, these calculations are based on ohm's law, which requires that the input variables, such as voltage and current, all be within the same frequency domain. For a 50 Hz power system, these measurement inputs should be 50 Hz phasors to justify the above calculations. However, in the case of a line connecting a variable renewable source, the measured voltage and the measured current on the variable renewable source side may not have the same frequency during the failure period, and thus the calculation results of equation (1) and equation (2) may be erroneous. This may lead to erroneous decisions such as distance protection over-or under-tuning. In view of the above, the first method may utilize sequence voltage in combination with phase domain calculations to determine the distance protection setpoint. The basic concept of this method is to calculate the set point sequence voltage, positive sequence voltage at set point V a1,rp, negative sequence voltage at set point V a2,rp, and zero sequence voltage at set point V a0,rp. Then, taking the AG failure at the tuning point as an example, the action amount of equation (3) and the braking amount of equation (4) can be calculated and compared with each other. It is noted that the sequence voltage is a component for analyzing an unbalanced three-phase power system, wherein the sequence voltage facilitates analysis of the three-phase power system by decomposing the system into three sets of symmetric phasors (i.e., a positive sequence voltage phasor set, a negative sequence voltage phasor set, and a zero sequence voltage phasor set). The positive sequence voltage includes balanced three-phase voltage phasors that differ from each other by 120 degrees and rotate counterclockwise (ABC rotation) in the same order as the system. The negative sequence voltage comprises balanced three-phase voltage phasors that rotate counter-clockwise (ACB rotation) in reverse order compared to the system, and wherein the zero sequence voltage comprises three-phase voltage phasors that are in phase with each other. (3) (4) If the motion amount V op is greater than the braking amount V restraint, it can be determined that there is an internal fault in the protection zone, so that a trip signal can be issued. Note that equations (3) and (4) are calculated for asymmetric fault (such as AG fault, ABG fault, ACG fault, AB fault, and AC fault) detection associated with the a-phase. In the case of a phase B related fault or a phase C related fault, the calculations of equations (3) and (4) may be based on the corresponding pha