CN105140891A - Adaptive method of busbar differential protection under running and switching - Google Patents

Abstract

A busbar differential protection self-adaptive method under normal operation and switching operation conditions, self-adaptive switching of starting and action elements, self-adaptive adjustment of proportional braking coefficient, specifically as follows: under normal operating conditions, the large difference element is used as the starting The small difference element is used as the action element, and the proportional braking coefficient of the large difference element adopts a smaller value to expand the action area and reduce the braking area; The proportional braking coefficient of the action element and the large difference element adopts a larger value to reduce the action area and expand the braking area. This solution improves the sensitivity of the existing bus differential protection action under normal operating conditions, and improves the reliability of the existing protective bus differential protection action under switching operation conditions.

Description

A self-adaptive method of busbar differential protection in operation and switching

technical field

The invention relates to the field of electric power systems, and more specifically relates to a scheme for adaptive discrimination, sensitive and reliable action of relay protection bus differential protection of electric power system under normal operation and switching operation conditions.

Background technique

Busbar protection plays a very important role in the field of relay protection in power systems. The correct action of busbar protection can ensure the power supply of important loads and greatly reduce user losses.

The existing busbar differential protection adopts a fixed ratio braking curve to distinguish between the action area and the braking area. When there is a current drawn out, if a fault occurs in the busbar area, the sensitivity of the protection action will be reduced; The differential circuit composed of all the branch currents of the bus except the bus coupler/section branch) is used as the starting element to fix the small difference (that is, all the branches connected to a certain bus including the bus coupler/section branch current constitute The differential circuit) is used as the action element, and there will be a higher probability of protection misoperation when the switch is operated.

Contents of the invention

In order to solve the above-mentioned problems existing in the existing bus differential protection, the present invention proposes a solution for adaptive discrimination of bus differential protection under normal operation and switching operation conditions, so as to ensure sensitive and reliable operation of the bus differential protection .

The present invention specifically adopts the following technical solutions.

An adaptive method for bus differential protection in operation and switching, characterized in that: the method adaptively switches the starting and operating elements, and adaptively adjusts the proportional braking coefficient.

An adaptive method for busbar differential protection during operation and switching, characterized in that the method includes the following content:

(1) Under normal operating conditions of the bus:

1.1 The large difference element is used as the starting element, and the small difference element is used as the action element;

1.2 The proportional braking coefficient of the large difference element adopts the first proportional braking coefficient;

(2) Under the condition of busbar switching operation:

2.1 Exit the small difference element, and the large difference element changes from the starting element to the action element;

2.2 The proportional braking coefficient of the large difference element adopts the second proportional braking coefficient;

Wherein, the first proportional braking coefficient is smaller than the second proportional braking coefficient.

The relationship between the second proportional braking coefficient k2 and the first proportional braking coefficient k1 is:

k2≥(1.2～1.5)*k1≥0.3.

The present invention has the following beneficial technical effects:

The sensitivity of the differential protection action of the existing busbar is improved under normal operating conditions, and the reliability of the differential protection action of the existing protective busbar is improved under the switching operation condition.

Description of drawings

Figure 1 is the proportional braking curve of the large difference element under normal operation and switching operation conditions, where k1 is the proportional braking coefficient during normal operation, that is, the first proportional braking coefficient, and k2 is the proportional braking coefficient during switching operation, that is, the second Proportional braking factor.

Detailed ways

The solution of the present invention will be described in further detail below in conjunction with accompanying drawing 1 .

Existing busbar differential protection is based on Kirchhoff's current law. Theoretically, when calculating the differential current or braking current, all current branches flowing into or out of the bus section should be counted only once and should not be counted repeatedly. However, when there is a drain current on this section of the bus, the drain current will make repeated contributions to the braking current, making the differential proportional braking curve closer to the braking zone side. If a fault occurs in the busbar area, it is easier to enter the braking area, and it is difficult to start the large difference, which may cause the differential protection to refuse to operate. The existing busbar differential protection cannot identify whether there is a drain current. Therefore, in order to avoid this problem in the existing busbar differential protection, a solution to adaptively adjust the proportional braking curve is proposed. Under normal operating conditions, regardless of whether there is current drawn from the bus circuit, the proportional braking coefficient of the large difference element adopts a small value to expand the action area and reduce the braking area, so as to improve the sensitivity of the start-up of the large difference element without affecting the operation of the differential protection. correctness.

The existing busbar differential protection fixes the component characteristics of the large difference and the small difference, the large difference is fixed as the starting element, and the small difference is fixed as the action element. In the switching operation condition, the current recognized by the CT of the switching branch caused by the double span of the knife switch is the algebraic sum of the currents flowing into the two sections of the busbar of the double span of the knife switch. The respective currents of the two sections of busbars, when a fault occurs in the busbar area, the calculation of the small difference element between the faulty busbar and the non-faulty busbar is wrong, and the small difference element cannot correctly select the faulty busbar. In order to solve this problem, it is proposed to exit the small difference action element under the switching operation condition, and the characteristics of the large difference element are adaptively adjusted from the starting element to the action element. The braking coefficient adopts a larger value.

The present invention relates to the action discrimination problem of busbar differential protection in power system relay protection, more precisely: under normal operation and switching operation conditions, the proportional braking curve is adaptively adjusted to define different action areas and Braking area: Under normal operation and switching operation conditions, the starting and operating elements are switched adaptively, and the role of large difference and small difference in differential protection is adaptively changed. Attached Figure 1 is the proportional braking coefficient curve of the large difference element of the busbar protection, where k1 is the proportional braking coefficient during normal operation, k2 is the proportional braking coefficient during switching operation, and k2>k1.

This application discloses an adaptive method for bus differential protection in operation and switching, including the following content:

1. Under normal operating conditions of the bus:

1) The large difference is used as the starting element, and the small difference is used as the action element; 2) The proportional braking coefficient k1 of the large difference element adopts a small value to expand the range of the action area and reduce the range of the braking area.

Under normal operating conditions, if a fault occurs in the bus area, the differential current and braking current fall into the action area of the large-difference proportional braking curve, that is, the large-difference element starts, and the differential current and braking current drop point falls into the small The action area of the differential proportional braking curve, that is, the action of the small differential element. Bus differential protection locates the faulty bus according to the small difference in action, only jumps off the branch on the faulty bus, isolates the fault, and ensures the normal operation of the branch on the non-faulty bus.

When there is a drain current in the circuit, it has repeated contributions to the calculation of the braking current in the large difference element, which increases the braking current and enhances the braking characteristics. The large difference is not easy to start, and the differential protection is not easy to operate, so self-adaptation is required Adjustment, expand the operating area of the large difference, improve the sensitivity of the large difference, reduce the influence of the drawn current on the large difference, and start reliably even if there is a large difference of the drawn current. The drained current has nothing to do with the calculation of the differential current and braking current of the small difference element, so the action area and braking area range of the proportional braking curve of the small difference element will not be adjusted.

2. In the working condition of busbar switching operation:

1) Exit the small difference element, and the large difference changes from the starting element to the action element; 2) The proportional braking coefficient of the large difference element adopts a larger value k2 to reduce the range of the action area and expand the range of the braking area.

Only in the switching operation condition, the small difference is caused by the double span of the knife switch, which causes the current of the switching branch to be included in the small difference differential current or the braking current of the corresponding busbar. At this time, if a fault occurs in the busbar , there will be a small difference in the action is not correct. Therefore, under the switching operation condition, withdraw the small difference element to avoid protection malfunction. At this time, the large difference is still valid, the large difference is changed from the starting element to the action element, and the proportional braking coefficient of the large difference element adopts a larger value, the differential current and the braking current fall into the action area of the large difference proportional braking curve, and the bus differential The protection action trips all buses.

According to the fact that the current draw accounts for 50% of the fault in the bus area, the bus differential protection can still operate correctly, and considering the fault outside the area, the bus differential protection can reliably escape the unbalanced current, then k1≥0.3.

Considering that k2 has a certain reliability coefficient, if the reliability coefficient is 1.2 to 1.5, the relationship between the first proportional braking coefficient k1 and the second proportional braking coefficient k2 can be described as:

k2≥(1.2～1.5)*k1≥0.3.

The applicant has made a detailed illustration and description of the embodiments of the present invention in conjunction with the accompanying drawings, but those skilled in the art should understand that the above embodiments are only preferred embodiments of the present invention, and the detailed description is only to help readers better understand The spirit of the present invention does not limit the protection scope of the present invention. On the contrary, any improvement or modification made based on the spirit of the present invention should fall within the protection scope of the present invention.

Claims (3)

1. An adaptive method for bus differential protection in operation and switching, characterized in that: the method adaptively switches the starting and operating elements, and adaptively adjusts the proportional braking coefficient. 2. A busbar differential protection self-adaptive method under operation and switching, is characterized in that, described method comprises the following content: (1) Under normal operating conditions of the bus: 1.1 The large difference element is used as the starting element, and the small difference element is used as the action element; 1.2 The proportional braking coefficient of the large difference element adopts the first proportional braking coefficient; (2) Under the condition of busbar switching operation: 2.1 Exit the small difference element, and the large difference element changes from the starting element to the action element; 2.2 The proportional braking coefficient of the large difference element adopts the second proportional braking coefficient; Wherein, the first proportional braking coefficient is smaller than the second proportional braking coefficient. 3. The adaptive method according to claim 2, characterized in that: The relationship between the second proportional braking coefficient k2 and the first proportional braking coefficient k1 is: k2≥(1.2～1.5)*k1≥0.3.