• ➤
  
  Accredited tests for the Low and High Voltage Testing Laboratory
  
• ➤
  
  LOVAG Registered Laboratory
  

  International recognition through the Low Voltage Agreement Group.

The pulse generator

• The pulse generator has the following technical characteristics:
• Umax = 4.2 MV, energy E = 336 kJ

Measuring equipment

• Capacitive divider 4.2 MV
• Digital impulse voltage measurement system type TR-AS 100-10/ 4

Technical Features

Cascade rectifier (DC) with the following technical data:

• Nominal voltage 1 MV
• Rated current 30 mA

The measurement system consists of a 1 MV high-voltage resistive divider and a Keithley-type voltmeter.

1. High voltage bridge – Megger type used for on-site tests:

• Voltage: 250 V at 12 kV;
• Capacitance: 1 pF to 1.1 mF;

2. C+tgδ measurement system Tando-Omicron type

• tan δ: 0.1 % rdg. + 1 x 10^-4    5 μA ≤ IIN ≤ 1 A
• Capacitance: 0.1 % rdg. + 0.1 pF 5 μA ≤ IIN ≤ 1 A

Power and Switching Equipment

• High power transformers
• Voltage and current measuring transformers
• Disconnectors and Switches
• Electric cells
• Encapsulated Rods and Reactors

Insulation, Protection and Cables

• Isolated crossings
• Insulating housings, ceramic, glass or composite insulators
• Lightning protection equipment (determination of initial advance time)
• Dielectric tests for medium voltage electrical cables

Objectives and Object of Testing

• Development of protection against lightning strikes;
• Tested object: small wind turbine, scale 1:40, 3 MVA;
• The purpose of this test was to determine the effective protection of the wind turbine against lightning;

Methodology and Scientific Context

• Pulses (SI) with 250/2500 μs were applied;
• The climb and descent method was applied to determine the yield stress of 50%;
• The research was conducted at the request of the Faculty of Electrical Engineering at the University of Belgrade, as part of a doctoral thesis.

Description Methodology

• a continuous bias voltage is applied to the upper metal plane (simulates the cloud) and the lightning impulse wave is adjusted to obtain a contour;
• the maximum value (on lift) of the pulses and the trigger time are recorded for each pulse.
• The early emission lightning rod must be compared to a simple conductive rod.
• The tests are performed under the same conditions and configurations for each rod and lightning rod.

International Partners

The research was conducted for the following foreign partners: FOREND – Turkey; SCHIRTEC – Austria; PITTAS – Greece, QUALITY STRENGTH – Taiwan, ERICO – Netherlands, COSMOS – Russia, Tai Surge – Taiwan, etc.

Partial discharge measurement systems:

1. LDS-6 type instrument

• Pulse processing (wideband): 100-400kHz
• Detectable apparent charge: 0.2pC-100000pC

2. MPD 600 type acquisition units

• For input frequency:
• V input-0Hz – 4.3 kHz
• PD-0Hz – 20MHz input
• Fiber optic cables: 3m, 20m, 100m

Partial discharge measurement in high voltage equipment:

• Power transformers (oil and dry)
• Current and voltage measuring transformers
• Isolated crossings
• Cables
• Capacitors
• Metal oxide arresters

RIV measurement system:

• Measurement impedance
• Electromagnetic interference receiver, type SMV 42

RIV measurement on high voltage equipment:

• Suspension and traction insulator chains
• Overhead line accessories, Support insulators
• Instrument transformers
• Switching equipment

The research was conducted for the following foreign partners:

Necks – Sweden, Gural – Turkey, ABB – Sweden, Efacec – Portugal, Hydro Quebec – Canada, Elimsan – Turkey, COELME – Italy

Laboratory and field research

Measuring exposure of personnel/population to electromagnetic fields

• Electric and magnetic field measurement:
• – Electric and magnetic field: 5 Hz – 32 kHz
• – Electromagnetic field: 80 MHz – 3 GHz

Conducted and radiated disturbance measurement in the civil, automotive and military fields

Frequency range: 10 kHz – 18 GHz

Measurements according to:

• – EN 55011, EN 55014-1, EN 55025, EN 55032
• – Directive 2009/19/EC, ISO 11425
• – MIL-STD461G

Equipment used:

• Electromagnetic interference receiver: ESCI, SMV 42, PMM 9010/30P
• Artificial networks: LT 32/C, NNB 41, AN 2050, LN-KFZ/200, etc.
• Antennas: rod (VAMP 9243), frame (EMCO 6507, EMCO 6509), dipole (VHA 9103, VHA-9105), biconic (EFS 9218, UBAA 9114, VHBC 9133, VHBC 9124, precision PCD 8250), hybrid (logarithmic-periodic + biconic: BTA-M, HL 1000, VULB 9161), horn (DRH-18E), etc.

Frequency range: 10 kHz – 1 GHz

Measurements according to:

• – UNECE Regulation R10
• – EN 55025
• – EN 50121

Equipment used:

• Electromagnetic interference receiver:
  ESCI, SMV 42, PMM 9010/30P
• Antennas:
  – frame (EMCO 6507)
  – hybrid (logarithmic-periodic + biconical BTA-M)

Frequency range: 80 MHz – 1 GHz

Severity level: up to 10 V/m (AM modulation, 1kHz, 80%)

Measurements according to:

• – EN 61000-4-3

Equipment used:

• Signal generator: R&S SML 03 (9 kHz – 3.3 GHz)
• Power amplifier: AR 250W1000A (80 MHz – 1000 MHz, 250 W)
• Transmitting antenna: Log-periodic (AT 1080)
• Field probe: HI-6005
• Software: EMC 32

Research on the mechanical endurance of separators with Um = 550 kV

Behavior of 750 kV support insulators under mechanical bending and breaking loads

Behavior of instrument transformers Um=550 kV under the action of mechanical forces

Horizontal or vertical flame tests

Glow wire tests

Ball pressing tests

Determination of youngness indices and resistance to the formation of conductive paths

Cold, dry heat, humid heat, temperature variations

Salt fog

Ultraviolet radiation

Humid sulfurous atmosphere

Climatic chamber

• Temperature range: -50°C … +90°C
• Relative humidity range: 15% … 95%
• Dimensions: 3m x 3m x 4m

Compression-buckling

Temperature and tensile stress

Evaluation of the structural and electrical integrity of equipment simultaneously subjected to temperature variations and mechanical stresses (traction/compression).