Application Note: HVDC Testing

The DEWESoft instruments are the perfect solution for testing HVDC lines and HVDC converter stations. Both, factory system tests and tests at energised systems, can be done - all according to international standards like IEC 61975.

The converter station test includes inter alia:

• High-Voltage Energising
• Energising of reactive components (AC filters, capacitor banks, reactors)
• Tests at different DC configurations
• Trip test
• Open line test
• Back-to-Back test
• Short-Circuit test

The transmission tests are divided in low-power and high-power transmission tests. Together with the converter stations tests the low-power transmission test should verify that the equipment works properly. The low-power transmission tests includes inter alia:

• Basic operation tests (Steady State, Start-Stop, Current Ramping, etc.)
• Control Mode Testing (Reactive Power control, voltage control, DC power control)
• Different DC configurations
• Switching operations of primary equipment (Transformers, tap changers, AC and DC filters, reactive power compensation)
• Dynamic Performance Testing (Step response, Commutation failure, interactions)
• AC and DC system staged faults (Close 3-phase-earth, busbar 3-phase-earth, DC line fault etc.)
• Loss of telecom, auxiliaries and redundant equipment

The high-power transmission tests are done to verify the steady-state performance parameters of the HVDC system. The tests include inter alia:

• Loading Tests
  • Minimum-, rated- & overload power transfer
  • different AC system conditions and
  • different voltage levels
  • operation with filter banks or reactive power banks unavailable
  • steady-state range of AC power frequency and voltage
  • extremes of ambient
  • bipolar and mono-polar operation with and without earth.
• Reactive Power Control (test have to be done at same operating points like at loading tests)
  • AC / DC filter
  • Shunt reactor
  • DC Smoothing Reactor
• Harmonic Performance and filter rating (test have to be done at same operating points like at loading tests)
  • AC & DC filter check
  • Harmonic Performance
  • Interference with third party electrical system
• Overload / Temperature Raise
• Audible Noise (measurement at different operating points: low-, rated- overload power etc.)
  • Component generated audible noise (transformers, filters, valves etc.)
  • Conductor generated audible noise (Corona effect)
  • Impact generated audible noise (power circuit breakers, disconnect switches)
• EMC tests (Power Line carrier, Telephone Interference factor, etc.)

All in all there are a couple signals which have to be measured, like:

• AC voltages on each phase
• AC currents on each phase
• DC voltages on both poles
• DC currents on each pole and on each DC neutral connection
• AC currents in the valve winding on each phase
• AC currents in filter banks
• Transformer primary currents
• AC busbar voltages
• AC currents on converter feeder
• AC currents in filter banks
• Other signals (Protections, Control signals, firing and extinction angles etc.)

Out of the measured signals a couple of calculations and analysis has to be done, like:

• RMS Voltages and Currents
• Active-, reactive, apparent power, Phase angle, power factor, Impedance
• Harmonic voltages and currents
• Unbalance and symmetrical components
• Inrush-Currents, Resonance
• DC / AC side interactions at switching processes
• Transient Stability at system state change or switching of primary equipment
• Overvoltage, Transient Recording
• And a lot more...

In all of this tests, the HVDC system shall recover in stable operation and all parameters should be within limits out of manufacturer’s specifications and international regulations.

Especially the analysis of the Inrush-Current and the analysis at switching processes (voltage and current) requires high-bandwidth (2 MHz), high-sampling rate (1 MS/s) and high-accurate inputs. All voltages and currents (AC, DC) can be measured synchronously and power analysis for different configurations (AC, DC) can be done. Beside this also the required analysis for audible noise is possible (e.g. Corona effect) – all within just one instrument.

The following picture show some exemplary results out of the different tests.

If you like further information on the DEWESoft Data Acquisition Systems or Software and reside in Australia or New Zealand, please contact Metromatics on +61 7 3868 4255 or sales@metromatics.com.au 

For outside this area, contact Dewesoft directly on +43 31 32 2252 or sales@dewesoft.com