Abstract: In recent years, the State grid company and the Southern power grid company for the intelligent construction of the distribution network enthusiasm has increased, the investment is in the trillion level, the number of equipment is quite large, which the existing line upgrade will occupy a considerable proportion, so how to achieve the rapid upgrade of the column switch has become a very urgent need. In this paper, a reliable solution is proposed for the rapid transformation of the existing conventional column circuit breaker, which can be used as reference for the design of similar products.

Key words: Long March; Long March Electric; Distribution network; Column switch; Circuit breaker; transform

1. Introduction

Distribution network is an important part of a strong smart grid, is a social public service platform directly connected to the majority of power customers, is a key link to ensure that power is "down, distributed, and used", and is also an important window for power grid enterprises to fulfill their social responsibilities and establish brand image. At present, the State Grid Company and the Southern Power grid company take the construction of a strong smart grid as a major strategic task, and put forward the "unified technical standards, unified design scheme, unified equipment selection" as a means to achieve the "technical standards system, modular design scheme, equipment selection standardization" as the goal of the distribution network standardization construction work. Under the guidance of this idea, the equipment manufacturers have basically formed a set of nearly unified supply schemes, laying a firm foundation for the standardization of the distribution network. In the existing circuit breaker supply scheme, it is generally divided into two versions with inrush current controller version and FTU version, of which the inrush current controller version is generally used in relatively underdeveloped areas, the control logic is relatively simple, and only has the "three-stage protection" function; The FTU version is generally used in economically developed areas, which not only has the "three-stage protection" function, but also has the functions of reclosing, "three-remote", communication, fault recording, etc., which can fully realize distribution automation. With the passage of time, many economically underdeveloped areas need to upgrade the surge current controller version product to the FTU version product, in today's power outage time is strictly controlled, how to achieve the rapid transformation of the switch on the column has become very practical significance.

Aiming at the rapid transformation scheme of the switch with inrush current controller on the distribution network column, the author designs a rapid transformation scheme based on the modular product platform, and gives the concrete realization method, including the structure splitting of the switch on the column, the control logic, the design of the circuit breaker body module and the design of the controller module.

2, the conventional inrush current controller column circuit breaker scheme introduction

The existing column circuit breaker scheme with inrush current controller generally consists of two parts: circuit breaker body and inrush current controller unit. The circuit breaker body includes arc extinguishing unit, shell, operating mechanism, current transformer, etc. The arc extinguishing unit can close, carry and break the current under normal circuit conditions, carry the specified overcurrent within a specified time, and can close and break the current under abnormal circuit conditions (such as short circuit conditions) and provide the necessary insulation capacity. The housing serves as a support component and provides the installation and transmission base for the arc extinguishing unit, operating mechanism, indicating and manual operation modules, etc. The operating mechanism provides the operating power for the arc extinguishing unit to ensure the reliable opening and closing of the arc extinguishing unit. As the current signal conversion unit, the current transformer provides the current signal for the inrush current controller. The overcurrent trip device and the inrush current controller are the control and execution units of the circuit breaker, and are the brains to realize the three-stage current protection. As the execution unit of conventional opening control, the tripping device is connected with other control signals to realize product opening.

Existing on-column circuit breaker solutions with inrush current controllers include two separate control loops: Inrush current control and conventional control, in which the inrush current loop is directly controlled by the inrush current controller, and the inrush current controller and electrical loop are installed inside the shell. When the product needs to be upgraded, it is necessary to disassemble the product shell, dismantle the inrush current controller and electrical loop, and reassemble the 26-core flight plug and electrical loop, which is very difficult and strong. And it could cause the lines to go out for a long time.

3, the rapid upgrade of the column circuit breaker scheme

Compared with the existing circuit breaker with inrush current controller, the on-column circuit breaker suitable for rapid upgrading is optimized in both electrical principle and product structure. In the structure, the inrush current controller is external, and the standardized navigation interface is used to connect. Electrically, the original overcurrent trip device and its electrical circuit are cancelled, and the overcurrent trip device is unified with the tripping device.

After the optimization of the column circuit breaker suitable for rapid upgrading and transformation, the structure is simple and the standardization is higher, which is highly consistent with the "unified technical standards, unified design scheme and unified equipment selection" required by the State Grid Company and the Southern Power Grid Company, and provides strong support for the realization of "systematic technical standards, modular design scheme and standardized equipment selection". The column circuit breaker which is suitable for rapid upgrading is consistent with the existing column circuit breaker equipped with inrush current controller on the arc extinguishing unit; On the shell module, the mounting holes and accessories of the original inrush current controller are removed to simplify the shell structure; In the operation mechanism, cancel the surge release device and related accessories to reduce the cost; The circuit breaker body is modular and standardized, so that the circuit breaker body external interface is consistent inrush current controller is redesigned and optimized, the inrush current controller is modular, the interface is standardized, the electrical interface is strictly implemented in accordance with the general design specifications of the national grid, and the seamless docking of the inrush current controller and FTU is realized.