VLF Testing

  • VLF, DC and sheath fault testing in one device
  •  Portable thanks to two-part construction
  •  High test capacitance
  •  Integrated discharge system
  •  Reporting

The portable, high-performance and energy-efficient VLF test systems are used for testing cables with 0.1 Hz cosine-rectangular voltage according to IEC/IEEE/CENELEC standards. In accordance with guidelines, the dielectric strength of cables and joints must be checked after installation or repair.

The VLF test systems from SebaKMT have high test-capacities and are still compact, because of the patented voltage wave-shape and the power-recycling during polarity reversal. Aside from cable and sheath testing, the test systems can also be used for the precise pinpointing of sheath faults (in combination with a step-voltage probe).

In total three portable systems are available, each with different voltage levels (28, 40 and 60 kVrms):

  •  VLF CR-28 up to cable series 15 kV
  •  VLF CR-40 up to cable series 23 kV
  •  VLF CR-60 up to cable series 35 kV
  • Very high test power without frequency reduction
  •  Covers cables up to 20 km at maximum voltage
  •  No polarisation effects as with DC
  •  Protocoling
  •  Breakdown detection
  •  Leakage current measurement

Powerful 0.1 Hz VLF test system with energy recovery for testing of cables with Cosine Rectangular Wave voltage according to VDE, IEC and IEEE.

In accordance with most regulations, cables and joints must be tested after installation or repair. The Seba KMT VLF Test System CR 60 kV can be used to test cables with operating voltage levels up to 36 kV. The system consists of a control unit and a HV unit. The high test capacity of 6.5 μF permits the simultaneous testing of all three phases. Positive and negative DC testing of cables and connected switchgear can be carried by DC Mode.

This VLF Test System CR 60 kV can be used both as a stand alone system and as integrated part of a test van system

  • High test capacity of 5 μF
  •  Single-button operation “easyGo”
  •  Continuous duty cycle
  •  Integrated safety system
  •  Suitable for diagnosing 45 kV rated cables

The VLF Sinus 54 kV is the ideal system for all users who want to or must test with a genuine 0.1 Hz sine wave voltage. The VLF testing system can be perfectly integrated in a fault location system or in combination with an OWTS and the optional tanDelta test attachment as part of a diagnostic test van. The system is designed for continuous operation which prevents unnecessary waiting times and increases test efficiency drastically.

Using a USB stick, logs can be conveniently created in.csv format, enabling further data processing, and are also saved in Easyprot format (software supplied) for clear and structured reports. Sheath faults can be precisely pinpointed by using the step voltage method in combination with the optional available step-voltage probe ESG NT.

  •  High test capacity of 5 µF
  •  Suitable for outdoor use (IP 54)
  •  Single-button operation
  •  Integrated safety system
  •  Reporting
  •  Continuous duty cycle

The VLF sine wave 34 kV is a compact, robust and portable VLF sine wave test system for medium voltage cables.

The design, optimized for rapid transportation and quick setup, and the continuous duty cycle are two attributes that qualify the system as an ideal tool for routine cable testing. For both 0.1 Hz sine wave voltage tests and rectangular or DC voltage tests, the VLF sine wave 34 kV fills the highest demands on the test voltage quality and stability. Moreover, the integrated “breakdown detection“ shuts down the test voltage in the event of an excessive charge current and guarantees limited damage to the cable.

Consistent single-button operation combined with a sophisticated operating concept allows a fast and targeted use of the system.

  • 20 kV with 0.1 Hz Cosine Square Wave Voltage

In accordance with most regulations, cables and joints must be tested after installation or repair. For this test the breakdown strength of the cable is tested.

The portable VLF Test System 20 kV can be used to test the cables in conjunction with the according local regulations for operating voltage levels up to 11 kV for new cables and 16 kV for aged cables at 3 碌F cable capacity.

By using the patented 0.1 Hz Cosine Square Wave Voltage PE, XLPE and paper cables are brought to a controlled breakdown very fast without causing additional damage or aging to the cable insulation.

  • Test capacity of up to 10μF – that’s up to 40 km or 25.8 miles of cable at reduced frequency and voltage
  •  Internal tanδ option with automatic results interpretation
  •  One minute burn after fault detection
  •  Automatic frequency adjustment based on cable length
  •  Adjustable DC pulse rates of 1:3 and 1:4
  •  IEEE compliant withstand testing for new installations up to 25 kV
  •  IEEE 400.2 compliant maintenance testing up to 35 kV
  •  IEC 60229 compliant sheath testing up to 20 kV DC

The VLF Sine Wave 45, with optional integrated tanδ, is a compact system for commissioning, testing and condition analysis of medium-voltage cables. This unit performs very low frequency (VLF), DC, and sheath integrity testing as well as sheath fault pinpointing when combined with the optional ESG NT step voltage probe. Ideal for both routine testing and complicated diagnostics, the VLF45 has a multi-purpose design with a continuous duty cycle.

For 0.1 Hz sine wave, rectangular or DC voltage tests, the VLF45 provides enhanced voltage quality and stability. In the event of excessive charge current integrated breakdown detection shuts down the test, ensuring limited damage to the cable. Up to 1000 measurements can be stored in the internal memory and results can be viewed on the unit or downloaded via the USB port to the included Easyprot software for reporting.

An optional internal tanδ is available that automatically evaluates results for PE, XLPE and PILC type cables based on insulation and selected compliance standard. Combined with the optional ESG NT step voltage probe, the VLF45 can pinpoint sheath faults.

  •  Very accurate measurement
  •  Optional leakage current correction
  •  High wireless range
  •  Measurement at high voltage potential

The tan delta test attachment enables a precise determination of the condition of the cable. Integral aging effects, such as the degree of humidity and “water treeing” can be simply recognized and quantified, making the tan delta test attachment the ideal instrument for monitoring the condition of the cable.

The tan delta test attachment can be used as a stand-alone system with the portable VLF sine systems or in combination with the integrated VLF sine test systems in vehicles.

The system achieves very accurate measurements because it measures at the high voltage potential and the measuring head can be placed very close to the test object.

  • Easy to operate
  •  Configurable test sequences
  •  AC, DC and sheath testing in one single system
  •  Reporting via USB or Winkis

The Easytest represents a simplified version of the standard VLF test. It has been designed to verify operational integrity versus operational reliability, which is the objective of a standard VLF test in accordance with the respective standards.

Typically, a simplified test is performed in accordance with company specifications after repairs or after a new cable or circuit has been installed. The purpose of such a test is to verify the integrity of the cable and there accessories before switching the circuit back into operation. The Easytest allows such a test at voltages well above operating voltage in order to provide a safe indication regarding operational integrity.

  • Two proven voltage wave shapes in one device
  •   Standard compliant VLF cable testing with accompanying PD diagnosis
  •   Non-destructive PD diagnosis by means of proven DAC voltage
  •   50 Hz Slope Technology for a direct comparison with the power frequency

Network operators can now get faster and significantly more reliable information about the quality and the condition of their cables. This is made possible thanks to the brand-new 50 Hz Slope Technology. For the first time, it has become possible to immediately locate faults in underground cables during the actual PD measurement.

With the 50 Hz Slope Technology for the first time, a withstand test with VLF cosine-rectangular voltage (VLF CR) and PD diagnosis with damped alternating voltage (DAC) is combined in one unit. This allows an efficient and integrated solution for precise inventory of the network infrastructure. The important fact here

is that the PD measurement data, gained with the VLF CR or with the DAC test voltage, can be compared directly with the 50 / 60 Hz network voltage. This facilitates reliable decision making