Fault phase selection method of double transmission line protection on the same pole

Abstract

The invention provides a fault phase selection method of double transmission line protection on the same pole, comprising the steps that (1) a low voltage phase component criterion Uphi<Uset selects the fault phase firstly, in the formula, Uphi is any one voltage value of the three phases A, B and C, and the Uset is a set voltage threshold constant value; (2) the criterion FORMULA based on fault component direction distinguishes the fault type, among the formula, Delta Uphi and Delta Iphi are the fault component voltage and current of the fault phase selected by the low voltage phase selection component, and Theta phi is the phase angle difference of them; when step (1) and step (2) are fulfilled at the same time, the fault phase Phi is judged to be an internal fault phase, then the protection is implemented, if only the step (1) is fulfilled, the fault phase Phi is judged to be an external fault, then protection is not actuated.

Description

technical field The invention belongs to the field of electricity, and in particular relates to a fault phase selection method for protection of double-circuit lines paralleled on the same pole. Background technique Due to the advantages of saving outlet corridors, large transmission capacity, less investment, quick results, improved power supply reliability, and simple operation and maintenance, the double-circuit line on the same pole can be well adapted to the modern power system. It is reliable, economical, and has a large transmission capacity. and other requirements, so it has been widely used. However, the types of faults of double-circuit lines paralleled on the same pole are very complicated, with as many as 120 types of faults, including 22 types of single-circuit line faults and 98 types of cross-line faults. For relay protection, when a fault occurs on a double-circuit line, it is crucial to accurately select the fault phase from such complex fault types for the...

AI Technical Summary

Problems solved by technology

However, it is greatly affected by the system operation mode and the transition resistance of the fault point, and the phase selection result is often unsatisfactory.

When it is applied to parallel double-circuit lines on the same pole, the method of simultaneously calculating six impedance measuring elements is used to judge the fault phase. Generally, when a cross-line fault occurs, the correct phase can be selected, but the calculation amount is too large, and it is impossible to judge the outlet span. Line fault type (two-phase or three-phase voltage is zero at this time)

Sequence current phase selection is a phase selection method using the relative phase relationship of the fault current sequence component. It has the advantages of being less affected by the transition resistance of the fault point and not affected by the load current. Therefore, it has been widely used in single-circuit lines and is often used as a protection However, when it is used in parallel double-circuit line systems on the same pole, it has the disadvantage of being unable to distinguish phase-to-phase faults and line-crossing faults in the area, which is mainly manifested in: (1) when both sides of double-circuit lines on the same pole When there is a large difference in the size of the power supply, a single-phase cross-line fault with a non-identical phase occurs near the side of the small power supply, and the current of the non-faulted phase on this side (it is the faulted phase of the same name on the adjacent line) may approach or exceed the current of the faulted phase, resulting in the phase change of the sequence current. Reflects the fault condition, which is worse when the line is short

(2) For the fault situation of a single phase crossing two phases (including the same list phase), the line in the two-phase fault may choose a wrong phase. The reason is that the two-phase fault line in this cross-line fault is incomplete. Short-circuit (or grounding) characteristics, that is, the fault current of the phase with the same name is only about half of that of the other fault phase, so that the phase difference of negative-sequence and zero-sequence current may fall into the wrong fault phase area

It can be seen that the current fault phase selection method of transmission lines has shortcomings such as inaccurate phase selection results (misjudgment will occur in some special cases) and excessive calculation when applied to fault phase selection of double-circuit lines on the same pole. Due to the particularity of the fault types of double-circuit lines on the same pole, the phase selection method widely used on single-circuit lines is currently difficult to meet the phase selection requirements of double-circuit line protection on the same pole

Images