US-12627135-B2 - Distance protection of a transmission line

US12627135B2US 12627135 B2US12627135 B2US 12627135B2US-12627135-B2

Abstract

The present disclosure relates to a method for distance protection of a transmission line carrying a plurality of phases for a phase-to-phase-to-ground fault comprising a first phase and a second phase of the plurality of phases as faulted phases in the phase-to-phase-to-ground fault, wherein the first phase is different from the second phase, the method comprising: obtaining a first impedance of a first electrical loop formed by a first phase carried on the transmission line and a ground potential based on a zero-sequence current (S 601 ); obtaining a second impedance of a second electrical loop formed by a second phase carried on the transmission line and a ground potential based on the zero-sequence current (S 602 ); computing an apparent impedance of the transmission line and a ground potential based on the transmission line seen at a first terminal based on the first impedance and the second impedance (S 603 ); and performing the distance protection based on the apparent impedance (S 604 ). The present disclosure also relates to a respective device, computer-readable medium, and system.

Inventors

OD NAIDU
Neethu GEORGE
Sinisa ZUBIC
Zoran Gajic

Assignees

HITACHI ENERGY LTD

Dates

Publication Date: 20260512
Application Date: 20221104
Priority Date: 20211223

Claims (20)

1 . A method for distance protection of a transmission line carrying a plurality of phases for a phase-to-phase-to-ground fault comprising a first phase and a second phase of the plurality of phases as faulted phases in the phase-to-phase-to-ground fault, wherein the first phase is different from the second phase, the method comprising: obtaining a first impedance of a first electrical loop formed by the first phase carried on the transmission line and a ground potential based on a zero-sequence current; obtaining a second impedance of a second electrical loop formed by the second phase carried on the transmission line and a ground potential based on the zero-sequence current; computing an apparent impedance of the transmission line seen at a first terminal based on the first impedance and the second impedance; and performing the distance protection based on the apparent impedance.
2 . The method of claim 1 , wherein the apparent impedance of the transmission line comprises the zero-sequence current.
3 . The method of claim 1 , wherein performing the distance protection comprises controlling a distance protection relay.
4 . The method of claim 1 , further comprising identifying a point of a phase-to-phase-to-ground fault based on the computed apparent impedance.
5 . The method of claim 4 , further comprising determining if the identified point of phase-to-phase-to-ground fault lies within the distance between the first terminal and the second terminal.
6 . The method of claim 1 , wherein computing the apparent impedance comprises computing a mean of the first impedance and the second impedance.
7 . The method of claim 1 , wherein obtaining the first impedance and the second impedance is performed by at least one of a relay, a controller, a server, or a cloud.
8 . The method of claim 1 , wherein the transmission line is any one of a parallel line, a coaxial cable, a planar transmission line, or a radial line.
9 . The method of claim 1 , wherein the first terminal is coupled to a first generator and/or is terminating the transmission line.
10 . The method of claim 9 , wherein the transmission line is further terminated by a second terminal and/or a second generator is coupled to the second terminal.
11 . The method of claim 10 , wherein the first terminal is coupled to the first generator and/or the second generator is coupled to the second terminal, and wherein the first generator and/or the second generator comprises and/or is-a synchronous generator or an asynchronous generator.
12 . The method according claim 11 , wherein the first generator and/or the second generator comprises a renewable power plant.
13 . The method according claim 12 , wherein the renewable power plant is an inverter-based resource (IBR).
14 . The method according to claim 1 , wherein computing the apparent impedance of the transmission line relay is performed by at least one of a relay, a controller, a server, or a cloud.
15 . A device for distance protection of a transmission line carrying a plurality of phases for a phase-to-phase-to-ground fault comprising a first phase and a second phase of the plurality of phases as faulted phases in the phase-to-phase-to-ground fault, wherein the first phase is different from the second phase, the device comprising a processor being configured to: obtain a first impedance of a first electrical loop formed by the first phase carried on the transmission line and a ground potential based on a zero-sequence current; obtain a second impedance of a second electrical loop formed by the second phase carried on the transmission line and a ground potential based on the zero-sequence current; compute an apparent impedance of the transmission line seen at a first terminal coupled to a first generator based on the first impedance and the second impedance; and perform the distance protection based on the apparent impedance.
16 . The device according to claim 15 , wherein computing the apparent impedance comprises computing a mean of the first impedance and the second impedance.
17 . A system for distance protection of a transmission line carrying a plurality of phases comprising: a transmission line; and the device according to claim 15 .
18 . The system according to claim 17 , wherein computing the apparent impedance comprises computing a mean of the first impedance and the second impedance.
19 . A non-transitory computer-readable medium having instructions stored thereon for a distance protection of a transmission line carrying a plurality of phases for a phase-to-phase-to-ground fault comprising a first phase and a second phase of the plurality of phases as faulted phases in the phase-to-phase-to-ground fault, wherein the first phase is different from the second phase, wherein the instructions, when executed by a processor, cause the processor to: obtain a first impedance of a first electrical loop formed by the first phase carried on the transmission line and a ground potential based on a zero-sequence current; obtain a second impedance of a second electrical loop formed by the second phase carried on the transmission line and a ground potential based on the zero-sequence current; compute an apparent impedance of the transmission line seen at a first terminal based on the first impedance and the second impedance; and perform the distance protection based on the apparent impedance.
20 . The non-transitory computer-readable medium according to claim 19 , wherein computing the apparent impedance comprises computing a mean of the first impedance and the second impedance.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application is a national stage entry of International Patent Application No. PCT/EP2022/080859, filed on Nov. 4, 2022, which claims priority to Indian patent application Ser. No. 202141050738, filed on Nov. 5, 2021, and European Patent Application No. 21217593.9, filed on Dec. 23, 2021, which are all hereby incorporated herein by reference as if set forth in full. The present disclosure relates to a method, a device, a computer-readable medium, and a system for performing a distance protection of a transmission line connecting generators. An electrical grid comprising generators, in particular distributed generators, connected with transmission lines requires a stringent fault-ride through condition to prevent further propagation of faults through the grid network, thereby ensuring a reliable power supply even in the presence of grid faults. Many systems implement relays along the transmission lines and control, in case of faults detections, the relays to achieve an electrical isolation of the faulted lines. Particularly, a distance protection principle determines the fault location with respect to the location of a relay by calculating the electrical characteristics, in particular an apparent impedance seen from the relay. The relays in the grid are controlled based on the computed fault locations. Traditional synchronous generators exhibit different electrical characteristics in comparison to the distributed energy resources (DERs), particularly asynchronous generators. The frequency of a generated electricity therefrom differs from the operating frequency of the grid, thus must be synchronized through inverters. Hence, such generators are otherwise referred to as inverter-based resources (IBRs), including a photo-voltaic generator and a wind turbine generator. In an existing line protection, in particular distance protection, the fault locations are computed based on the electrical characteristics of synchronous generators, thus results in a significant error when asynchronous generators are considered. The following presents a system comprising two synchronous generators and a system comprising a synchronous generator and an asynchronous generator. Furthermore, the apparent impedance calculation methods and their performances are presented with the accompanying figures. FIG. 1a) and b) illustrate schematics of a two-terminal transmission line system connected to generators. FIG. 1a) illustrates a schematic of two-terminal transmission line system connecting two synchronous generators. The two-terminal transmission line system 100 operating at 220 kV and 50 Hz comprises the first synchronous generator 101 connected to the second synchronous generator 102 with the transmission line 110. The transmission line 110 is terminated by a BUS N (equivalently, terminal N or remote terminal) 111 on one side towards the first synchronous generator 101 and by a BUS M (equivalently, terminal M or local terminal) 112 on the other side towards the second synchronous generator 102. The distance between the terminal N 111 and the terminal M 112 is 100 km in this example. The terminal M 112 comprises a relay, in particular a distance relay to be controlled by a distance protection control method. The voltmeter 122 monitors voltage at the terminal M 112 and feeds the measured values to the intelligent electronic device (IED) 121. The current meter 123 measures the current at the terminal M 112 and feeds the measured values to the IED 121. The IED 121 is configured to perform any required computing for the distance protection method. The fault 131 is located on any point on the transmission line 110 between the distance covered by the terminal M 112 and the terminal N 111. FIG. 1b) illustrates a schematic of a two-terminal transmission line system connecting one synchronous generator and one asynchronous generator through a delta-wye, Δ−Y, transformer and a wye-delta, Y−Δ, transformer. The Δ−Y transformer allows a single-phase load to be distributed among the three phases to neutral and vice-versa for the Y−Δ transformer. The two-terminal transmission line system 150 operating at 220 kV and 50 Hz comprises the first synchronous generator 151 connected to the second asynchronous generator (a plurality of wind turbines) 154 through the Y−Δ transformer 153 and the Δ−Y transformer 152, with transmission line 160. In this example, the rated active power of each wind turbine is 2 MW and 100 wind turbines are considered. The transmission line 160 is terminated by the BUS N (equivalently, terminal N or remote terminal) 161 on one side towards the first synchronous generator 151 and by the BUS M (equivalently, terminal M or local terminal) 162 on the other side towards the second asynchronous generator 162. The distance between the terminal N 251 and the terminal M 152 is exemplarily 100 km. The terminal M 152 comprises a relay, in particular a distance relay to be controlled by th