Power cable diagnosis tool


Advanced life expectancy assessment of
power cables via VLF test data analysis and
degradation estimation

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.

Business Model

Diagnosis Control Center for overall VLF test process management

Remote supervision of VLF tests: Technical support and safety/accuracy control
Comprehensive underground asset management
Data interface with existing DIS (Distribution Infromation System)

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.

Data Management
Raw data transferring from VLF test devices to the system
Test section management (between power equipment such as RMU, Transformer, cable junction, etc.)
Test / Diagnosis data filtering
Test / Diagnosis data statistics
User management: three authority levels (by functions and jurisdictions)
Diagnosis Result
Diagnosis Result
Degradation speed
Degradation starting period
Fault prediction date
Cable condition according to IEEE 400.2
Diagnosis data comparison with cumulative data on 2D/3D graphs
Cable condition tracking from previous diagnosis results on the same test section
Comprehensive diagnosis report

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

What you can do with VLF Pro :
- easily generate a precise diagnosis report using a VLF test result
- conveniently accumulate the diagnosis data and make various statistics
- Improve the diagnosis accuracy by automatic customization
How it works
VLF Pro derives three variables (TD, DTD, Skirt) from each VLF test result and shows their co-relationship on a 3D schematic graph after data normalization.
Initially, users will use the pre-defined diagnosis factors by the system, but after gathering enough test data, users can customize the diagnosis factors through ‘Wizard Function’. It provides the diagnosis factors as technical references via automatic analysis of the cumulative data based on its advanced algorithms.
User can customize the diagnosis factors according to their critical conditions ans the technical references by the system.
Consequently, the accuracy of VLF Pro can be improved by cumulating more test data and it can be applied to any kind of power cables.

Why VLF test?

  • Although it requires high costs, many power utilities are conducting scheduled replacement of old underground cables to prevent sever electric faults which usually cause a long time of outage and serious damages to the power networks. In this regard, detection of latent faults on underground power cables mitigates the high costs of restoration and the economic losses caused by the faults.
  • As a direct contact test method for a power cable, VLF testing provides the most meaningful test results such as Tan-Delta values. IEEE Std. 400.2 categorizes the values to estimate the cable condition as “No action required”, “Further study required”, and “Action required”. However, the decision has to be more specific because the “action” causes high cost of the cable replacement.
  • We believe that VLF testing provides the most meaningful signals than any other cable testing methods, but intuitive understanding about the signals is difficult. In regard to this matter, VLF Pro provides the most accurate diagnosis results through practical and precise data analysis algorithms that already verified on the KEPCO’s networks with more than 40,000 real VLF test results.
  • For a better cable condition diagnosis, VLF Pro is the most suitable solution.

IoT Smart Lock

IoT Smart Lock security solution for
indoor/outdoor electric equipment/control box


The most secure way to manage important field equipment

Smart Locking control and field test/inspection using Mobile App.
Status monitoring through GIS-based HMI
Bi-directional and dynamic security code control : Hacking free

Server System function (Customizable)

User management: Authorization, Grouping
- Test/inspection data gathering directly from the field using a Smartphone app.
- Field equipment O&M management including test/inspection results
Applied in KEPCO
Switch/TR. enclosure

Convenient communication device

GPRS/3G Modem

Application for SCADA/DMS, AMI, IoT solutions


GPRS/3G Modem

Size : 76.5mm x 54mm x 26mm
  • Detail cut 1

  • Detail cut 2

GPRS/3G Modem Specification

Feature Implementation
Frequency bands UMTS/HSPA+: Five band 800/850/900/1900/2100MHz
GSM/GPRS/EDGE: Quad band 850/900/1800/1900MHz
For further EHS6 Module details see [1]
SIM interface Supported SIM cards: 3.0V, 1.8V
Antenna interface Penta-band GSM/UMTS RF antenna
Extension interface Extension of Concept Board hardware through the Shield Interface
Power supply USB interface and
Supports Li+ battery pack through 2-pin connector on board
Serial interface EHS6 ASC0 via Virtual COM Port (VCP)
Maximum baud rate 921kbps
USB interface Supported
User buttons 4 buttons:
- User button BTN-A
- User button BTN-B
LEDs Current configuration is displayed via on board LEDs.
Configuration Two switch banks allow manual configuration of GPIO signal direction, ATC multiplexing and SPI/ASC sharing configuration. SW controlled configuration via CCU (Configuration Control Unit).

Advanced Metering Infrastructure

AMI Solution

Providing all AMI components: Smart meter, DCU, AMI S/W


AMI Solution

AMI System Component

  • DCU (Data Concentration Unit)
  • Head-end
  • Smart Meter
  • AMI Software

Smart Meter : DLMS/COSEM, DL/T 645-2007

Rating Voltage 230V / 400V
Current 5A(60A) ~ 10A(100A)
Working Temperature -25 ~ 70℃
Accuracy class 0.2 ~ 1.0
Protection Class (IEC60529) IP 54

DCU(Data Concentrator) :Q/GDW 376.1-2013

  • LAN/WAN Comm. Module
  • Meter data gathering : Scheduled, Event, Polling
  • Three Phase Metering

AMI Software

  • Meter data management
  • Metering data comparison
  • Meter/DCU status monitoring
  • Remote control
  • Billing
  • Event logging