A Smart Way to Diagnose Power Cable

Our precise data analysis technologies and deep understanding of VLF test help an accurate assessment
of a power cable condition for network reliability improvement and O&M cost saving

• VLF* Testing
  (* Very Low Frequency)

  It is the most accurate testing technique of medium voltage power cable. It is applied to measure insulation losses (i.e. insulation dissipation factor or tan-delta) at different VLF test frequencies that are typically in the range of 0.01 to 0.1 Hz. IEEE Std. 400.2 presents the criteria for the test data assessment.
  In addition, KEPCO (Korea Electric Power Corporation) establishes more precise criteria through its practical test data nalysis.
  VLF Pro applies both IEEE 400.2 and KEPCO’s assessment algorithm.

• Tan Delta
  (Loss Angle or Dissipation Factor)

  Tan-Delta measurement constitutes a cable diagnostic technique that assesses the general condition of the cable system insulation, which can be represented by and equivalent circuit that consists of two elements; a residtor and capacitor.
  When voltage is applied to the system, the total current is the result of the contributions from the capacitor current and the resistor current.
  Tan-Delta is defined as the ratio between the two currents.

• Partnership with KEPCO

  KEPCO, as one of the global leading power utilities, has conducted VLF tests for its underground power networks since 2010.
  The unique and accurate algorithm has established through the precise and practical analysis of more than 40,000 test cases.
  Based on the IEEE Std. 400.2, VLF Pro officially utilizes the KEPCO’s condition assessment algorithm.

APPLICATION IN KEPCO

Software Functions

VLF Pro derives three variables (TD, DTD, Skirt) from each test data, and shows thier co-relationships
on 2D/3D schematic graphs after data normalization.
Based on its advanced analysis algorithm, VLF Pro automatically calculate every diagnosis factor considering saved cumulative data
and suggests the factors as references. Moreover, VLF Pro enables users modify the factors according to their practical experiences.

Wizard : Engineering functions for the data customization and setting

• Normalization

  The system creates 3 factors from a TD test and each factor has a different numerical range even though the three factors have critical co-relationships. Therefore a data value normalization is required to intuitively compare the values

  

• Degradation Start Period Setting

  Degradation starting period is used in the system to calculate degradation speed
  and remaining duty period of a cable.

  

• Critical Point Setting

  It is to define Critical Point among Index R values which is the estimated fault occurrence value.
  It shows Cumulative index R density and Cumulative fault Index R density.
  Comparison of the two graph shall be a clear reference to define Critical Point.

  

• Calculation of a proper test length

  Capacitance of a cable and tanδ are inverse relation and the more cable length make the more Capacitance.
  Therefore, tanδ become near zero (≒0) in an infinite length of cable, and change of Resistance and/or change of permittivity in different dielectric caused by cable degradation may not affect to the tanδ value.

  

Strength of VLF Pro

Video

• VLF Pro2.0 Promotion
• VLF Pro3.0 Promotion