CN103107524A - Electric transmission line phase fault relay protection method - Google Patents

Abstract

The invention discloses an electric transmission line phase fault relay protection method which serves as a measuring element of measurement impedance of electric transmission line phase fault distance protection. The measurement impedance from a phase fault point to the protection installation portion can be measured accurately in any fault condition, which has no reference to phase fault point voltage, a load current and transition resistance. The method is closed reliably under the condition of heavy loading of an electric transmission line. Requirements of selectivity, reliability, sensitivity and quick-action performance of relay protection can be met through correct movement of the method when a phase high resistance short trouble happens under the condition of heavy loading electricity transmission.

Description

Relay protection method for interphase fault of power transmission line

Technical Field

The invention relates to the technical field of relay protection of power systems, in particular to a relay protection method for interphase fault of a power transmission line.

Background

The power frequency variable distance protection is formed by reflecting the working voltage amplitude abrupt change, and the method has the advantages of small influence of the operation mode of the power system, strong transition resistance and the like. However, the working voltage amplitude break variable adopted by the method only exists at the initial stage of the fault, and cannot be used as backup protection of the ultra/extra-high voltage alternating current transmission line.

The impedance distance protection reflects the length of the fault distance according to the magnitude of the measured impedance to distinguish whether the fault point is located inside or outside the protection zone. The impedance distance protection is slightly influenced by the operation mode and the structure change of the power system, the electrical quantity used for calculating and measuring the impedance is a full fault component, and the method is suitable for protecting the power transmission line in the whole fault process. Therefore, the impedance distance protection can be used for main protection of the high-voltage transmission line and backup protection of the ultra/extra-high voltage alternating-current transmission line.

The traditional interphase impedance distance protection assumes that an interphase fault point voltage is zero, calculates a measured impedance through a ratio of the interphase fault voltage and an interphase fault current, and reflects the distance of a fault point according to the magnitude of the measured impedance to determine whether a tripping signal is sent. In fact, in the power system, the inter-phase fault point voltage is almost impossible to be zero except for artificially constructed metallic inter-phase short-circuit faults. Therefore, the inter-phase fault point voltage may have a serious influence on the inter-phase distance protection operation performance.

In an actual power system, the additional impedance caused by the transition resistance seriously affects the operation performance of the impedance distance protection. If the additional impedance generated by the transition resistor is in resistance-inductance property, the distance protection of the phase impedance is rejected when the phase short circuit fault in the protection area is easily caused; if the additional impedance generated by the transition resistor is in resistance-capacitance, the phase-to-phase impedance distance protection action is easy to exceed when the phase-to-phase short circuit fault occurs outside the protection area. The high/ultra/extra-high voltage alternating current transmission line is also a heavy-load transmission line, the impedance distance protection is mistakenly operated by heavy-load current, and the influence of the heavy-load current on the impedance distance protection action performance cannot be ignored.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a relay protection method for interphase fault of a power transmission line. The method can realize the accurate measurement function of the measured impedance of the interphase short circuit fault distance protection of the power transmission line.

A relay protection method for interphase fault of a power transmission line comprises the following steps:

(1) measuring fault phase-to-phase voltage at transmission line protection installation

Fault inter-phase current

And normal phase negative sequence current

(ii) a Phi of the phase is AB phase, BC phase or CA phase respectively; Ψ corresponds to the C-phase or A-phase or B-phase, respectively.

(2) Measurement for calculating interphase short-circuit fault point to transmission line protection installation positionMagnitude impedance Z_φφ,ce：

Wherein,is fault interphase voltage;is fault phase current;

is normal phase negative sequence current; phi is respectively an AB phase, a BC phase or a CA phase; psi is respectively corresponding to C phase, A phase or B phase; x is the number of_setProtecting the setting range; β = Arg (z)₁)；

；；z₁Is the positive sequence impedance of the transmission line with unit length;

indicating normal phase negative sequence current

The current phasor after 90 degrees of anticlockwise rotation.

(3) Judgment of | Z_φφ,ce-Z_set|≤|Z_φφ,ce+Z_setIf | Z holds_φφ,ce-Z_set|≤|Z_φφ,ce+Z_setIf the l is established, the protection action is tripped; wherein Z is_setTo protect the setting impedance value.

Compared with the prior art, the invention has the following positive results:

the method measures the impedance measured from the interphase short-circuit fault point to the protection installation position of the power transmission line, and is irrelevant to the voltage of the interphase short-circuit fault point, the transition resistance and the load current.

Drawings

Fig. 1 is a schematic diagram of an interphase short-circuit fault of a power transmission line to which the method of the present invention is applied.

FIG. 2 shows that the method of the present invention is applied to the interphase short circuit fault of the transmission line

、

、、

、

And

electrical vector diagram of (2).

Detailed Description

The technical scheme of the invention is further detailed in the following according to the attached drawings of the specification.

In fig. 1, PT is a voltage transformer, and CT is a current transformer. The protection device samples the voltage of a voltage transformer PT and the current waveform of a current transformer CT at the protection installation position of the power transmission line to obtain the voltage and current instantaneous values.

Calculating fault phase-to-phase voltage phasor at protection installation position of power transmission line through Fourier algorithmFault phase current phasor

Normal phase negative sequence current phasor

As input quantities; wherein phi is a fault phase and is respectively an AB phase, a BC phase or a CA phase; Ψ is the normal phase, corresponding to phase C or phase A or phase B, respectively.

Interphase transition resistance R of power transmission line_fShort-circuit fault, phase-to-phase fault point voltage

Fault branch current

Because of the resistive phase-to-phase short-circuit fault, there is a fault branch

Thereby to make

。

The transmission line has a fault of short circuit between phases via transition resistance and a fault branchThereby to make

. Wherein,

、

positive sequence current and negative sequence current flowing through the fault branch circuit respectively;

a fault point-to-ground negative sequence current for the normal phase Ψ;

is composed ofThe current phasor after 90 degrees of anticlockwise rotation.

The normal phase negative sequence current measured at the installation position is protected when the transmission line has the fault of short circuit between phases through transition resistance

Negative sequence current to earth of normal phase fault point

In phase, i.e.

. Thus, obtain. Wherein,

indicating normal phase negative sequence currentThe current phasor after 90 degrees of anticlockwise rotation.

Compute distance protection installation x_setOperating voltage of position

：

Wherein z is₁Is the positive sequence impedance of the transmission line with unit length.

For transmission line to have interphase transition resistance short-circuit fault

、

、

、、

And

the electrical vector relationship of (2) is shown in fig. 2. In FIG. 2, the process is carried out by、

And

in the formed vector triangle, the relation of the formula (2) is obtained according to the corner relation of the triangle.

Wherein: β = Arg (z)₁)；

；

。

And (3) calculating the fault distance from the interphase short-circuit fault point to the power transmission line protection installation position according to the formula (2).

From measured impedance Z_φφ,ce=xz₁Calculating a measured impedance

。

Judgment of | Z_φφ,ce-Z_set|≤|Z_φφ,ce+Z_setIf | is true. If Z_φφ,ce-Z_set|≤|Z_φφ,ce+Z_setIf the l is established, the protection action is tripped; on the contrary, if | Z is satisfied_φφ,ce-Z_set|＞|Z_φφ,ce+Z_setIf, then the latch-up is protected.

As can be seen from the formula (3), the measured impedance of the interphase short-circuit fault distance protection of the method is independent of the interphase fault point voltage, the transition resistance and the load current. Therefore, the method can accurately measure the impedance measured from the interphase fault point to the protective installation position under any fault condition, can reliably lock under the heavy load condition of the power transmission line, and can reliably and correctly act when interphase high-resistance short circuit fault occurs under the heavy load power transmission condition.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.

Claims (1)

1. A relay protection method for interphase fault of a power transmission line is characterized by comprising the following steps: comprises the following steps of (a) carrying out,

(1) measuring fault phase-to-phase voltage at transmission line protection installation

Fault inter-phase current

And normal phase negative sequence current

(ii) a Wherein

Phi is respectively an AB phase, a BC phase or a CA phase; psi is C phase or A phase or B phase,

(2) calculating the measured impedance Z from the interphase short-circuit fault point to the transmission line protection installation_φφ,ce：

Wherein,

is fault interphase voltage;

is fault phase current;

is normal phase negative sequence current; phi is respectively AB phase or BC phase

Or a CA phase; psi is respectively corresponding to C phase, A phase or B phase; x is the number of_setProtecting the setting range; β = Arg (z)₁)；；

；z₁Is the positive sequence impedance of the transmission line with unit length;

indicating normal phase negative sequence current

The current phasor after 90 degrees of anticlockwise rotation,

(3) judgment of | Z_φφ,ce-Z_set|≤|Z_φφ,ce+Z_setIf | Z holds_φφ,ce-Z_set|≤|Z_φφ,ce+Z_setIf the l is established, the protection action is tripped; wherein Z is_setTo protect the setting impedance value.

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