Current Transformer Voltage Divider Layout for Fewer HV Variants
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The complexity in manufacturing current transformers with voltage indication for medium or high voltage equipment is increased due to numerous variants of capacitance net electrodes required for different voltage levels, leading to increased complexity and costs in production and procurement.
Innovation Solution
A current transformer design where an output conductor is connected to a voltage divider with discrete capacitors, where the primary capacitance is provided within the transformer body and the secondary capacitance is either fully or partly outside, connected in series to adjust the voltage ratio, and a thermal dilatation compensation element is used to stabilize the capacitors against temperature variations, while the output wire is shielded to reduce stray capacitance influences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If brass nets forming capacitive electrodes are used for voltage indication in current transformers, then voltage indication is achieved, but the number of variants increases due to different capacitance requirements for different voltage levels
Solution Approach 1:
The voltage divider is segmented into two separate capacitances: C1 (primary capacitance) integrated within the current transformer body, and C2 (secondary capacitance) located outside the transformer body. This segmentation allows C1 to remain standardized across different voltage levels while C2 is adjusted to meet specific capacitance requirements, thereby reducing the number of variants needed.
Solution Approach 2:
The secondary capacitance C2 is extracted from the current transformer body and placed outside. This extraction allows the primary capacitance C1 to be standardized and integrated once, while the external C2 can be varied independently to satisfy different voltage level requirements without creating new transformer variants.
2Ease of manufacture
If discrete capacitors are used in the voltage divider, then manufacturing is simplified and variants are reduced, but space requirements and assembly complexity must be managed
Solution Approach 1:
The primary capacitance C1 is merged with the current transformer body, utilizing the existing structural space within the transformer. This integration eliminates the need for separate housing for C1 and optimizes space utilization by combining two functions (current transformation and voltage indication) into a single integrated unit.
3Measurement precision
If capacitance values are adjusted for different voltage levels, then voltage indication accuracy is maintained, but manual geometry adjustments and assembly checks are required
Solution Approach 1:
Different capacitance values are achieved through local variation of only the external capacitor C2, while the main transformer body and primary capacitance C1 remain standardized. This localized customization allows automated manufacturing of the standardized transformer body, with only the external C2 requiring adjustment for different voltage levels.
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
This design reduces the number of variants, stabilizes capacitance values, simplifies manufacturing, and reduces space requirements, eliminating the need for manual geometry adjustments and assembly checks, while maintaining high stability and performance of the voltage indication system.
Implementation Method 1
a first discrete capacitor C1, forming a voltage divider with a second capacitor C2
Implementation Method 2
which consists of a first discrete capacitor C1, forming a voltage divider with a second capacitor C2, serially arranged in such a way that the capacitance values of both capacitors C1 and C2 determine a transformation ratio of a voltage divider
Implementation Method 3
a thermal dilatation compensation element is used to stabilize the capacitors against temperature variations
Implementation Method 4
the output wire is shielded to reduce stray capacitance influences
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a Current transformer with an additional voltage indicating functionality or for the use in medium or high voltage equipment, with primary terminals and primary conductors and a secondary circuit, according to the preamble of claim 1. In order to reduce the number of needed parts, and to support standardization, in the manufacture of the current transformer, the invention is, that beside the secondary circuit a shielded output wire (4) is arranged in such, that the output wire (4) is electrically connected to the end of discrete primary capacitor (C1), where capacitor (C1) is connected between the primary conductor (2) and the output wire (4) and defines the capacitance between the primary conductor (2) and the output wire (4), shielding (4') of output wire (4) is connected to a ground terminal (6).