Modular Current Sensors for Cable Bushing Installation
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Solution Overview
Problem
Existing high-voltage electrical switchgear systems face challenges in installing and replacing zero-sequence current sensors due to space constraints and the need for precise installation, leading to inefficiencies and increased costs, as well as limitations in current sensor performance.
Innovation Solution
A modular current sensing system comprising independent modules for phase and zero-sequence current sensing, where phase current sensors are embedded in insulating material and zero-sequence current sensors are embedded in an inclined ring shape, allowing for separate installation and minimizing space requirements, with modules integrated in shells like epoxy resin for improved precision and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase current sensors are installed covering each phase in the connection point between bushing and connector, then phase current sensing is achieved, but space is occupied leaving no room for zero-sequence current sensor installation
Solution Approach 1:
The patent transitions from a two-dimensional planar arrangement of sensors to a three-dimensional configuration where the zero-sequence current sensor is positioned in the axial direction (along the cable axis) while phase current sensors are mounted radially on the connector. This dimensional change allows all sensors to coexist in the limited connection point space without mutual interference.
Solution Approach 2:
The zero-sequence current sensor is designed with a toroidal shape that can be nested around the cable core, while phase current sensors are mounted on the outer surface of the connector. This nesting arrangement allows the zero-sequence sensor to occupy the central axial space while phase sensors utilize the radial surface area, maximizing space utilization.
2Measurement precision
If zero-sequence current sensor is installed on grid cables covering all phases, then zero-sequence current sensing is achieved, but installation and replacement require connector disassembly causing time loss and supply disruption
Solution Approach 1:
The patent divides the current sensing system into independent modular components: phase current sensors mounted on the connector and zero-sequence current sensor integrated into the cable bushing. This segmentation allows the zero-sequence sensor to be installed independently during cable termination without requiring subsequent disassembly for replacement, reducing maintenance time and supply disruption.
Solution Approach 2:
The zero-sequence current sensor is pre-installed and integrated into the cable bushing structure during the initial cable termination process. This preliminary action ensures the sensor is permanently positioned and secured before the cable is put into service, eliminating the need for future disassembly and reassembly during sensor replacement.
3Area of stationary object
If zero-sequence current sensor is installed in the same point as phase current sensors, then space utilization is improved, but installation errors occur due to lack of field testing opportunities
Solution Approach 1:
Both phase current sensors and the zero-sequence current sensor are pre-installed and factory-tested together as an integrated assembly during cable termination. This preliminary factory testing allows verification of sensor functionality and proper installation before the cable is put into service, ensuring reliability while maintaining compact space utilization.
4Ease of manufacture
If three phase current sensors are mounted on the same plane, then assembly is simplified, but space occupied is large leaving no room for zero-sequence current sensor
Solution Approach 1:
Instead of arranging all four sensors (three phase sensors and one zero-sequence sensor) in the same two-dimensional plane, the patent positions the zero-sequence current sensor in the axial dimension along the cable axis, while phase current sensors are mounted radially on the connector surface. This three-dimensional arrangement maintains assembly simplicity while significantly reducing the projected area occupied by the sensor assembly.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The modular system reduces installation errors and labor time, enhances current sensor precision and measurement range, and allows for easier replacement of individual modules, improving overall performance and reducing space requirements.
Implementation Method 1
current sensing in the cable compartment is carried out by means of inductive toroidal sensors
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The present invention relates to a current sensing modular system, which allows sensing the phase current and the ground-fault or zero-sequence current, having to that end at least a first module (7) comprising at least one phase current sensor (5) embedded therein and a second module (8) comprising a zero-sequence current sensor (6) embedded therein. According to the invention, if both modules (7, 8) are included, the first module (7) is independent of the second module (8), both modules (7, 8) being installed directly in the connection elements, i.e., in the connection point between at least one bushing (2) and at least one connector (4) of at least one grid cable (3).