1 / 26

Improved Assessment of Voltage Dips with Common Monitoring Devices

Improved Assessment of Voltage Dips with Common Monitoring Devices. M. Bollen, A. Robert & P. Goossens Session 2 Paper No5. Voltage Dip Representation. Why Voltage Phasors? Limitations of RMS-representation. Dip produced by single phase fault. single phase dip. 2-phase dip. Depth = 36 %.

enid
Télécharger la présentation

Improved Assessment of Voltage Dips with Common Monitoring Devices

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Improved Assessment of Voltage Dips with Common Monitoring Devices M. Bollen, A. Robert & P. Goossens Session 2 Paper No5

  2. Voltage Dip Representation Why Voltage Phasors? Limitations of RMS-representation

  3. Dip produced by single phase fault single phase dip 2-phase dip Depth = 36 % Depth = 16 %

  4. D y Dip produced by single phase fault • MAGNITUDE (PP) • U1 = 94% • U2 = 80% • U3 = 93% primary side trafo secondary side trafo

  5. Why phasors? • indication about origin • fault type and characteristics • dip propagation • through transformers • connection : star or delta • depth: phase-to-ground  phase-to-phase

  6. Improved Dip Characterisation (M. Bollen) Voltage Type: A, B, C, D, E, F & G Characteristic Magnitude V Phase Angle Jump 

  7. 7 Dip Types 4 types of faults • 3-phase faults • 1-phase faults • 2-phase faults • 2-phase-to-ground faults • propagation through transformers • delta or star connection Seven types of voltage dips A B (C, D) C (D) E (F, G)

  8. Dip Type A Origin: balanced three phase fault « A »

  9. Dip type B, C & D « B » origin: single phase faultstar connection « D » « C » 2-phase fault, delta connection origin: 2-phase fault, star connectionor single phase fault, delta connection

  10. Dip Type E, F & G Connection: star Origin: 2-phase to ground « G » « E » « F » Connection: delta Connection: delta Behind Dy or Yd trafo

  11. Fault Type Dip Location I II III 3-phase A A A 3-phase-to-ground A A A I 2-phase-to-ground E F G Yd 2-phase C D C II 1-phase-to-ground B C D Dy III Propagation of voltage dips line & phase voltages are swapped: rms-voltages changes !

  12. V V Characteristic Voltage Characteristic Magnitude V &Phase Angle Jump  • A, C, D, F, G: MIN(3 UPN & 3 UPP) • B, E: first remove U0 = Invariable of connection type (PP  PG) and location (primary  secondary trafo)

  13. Voltage Dip Conversion Algorithms RMS  PHASORS

  14. Why conversion algorithms? Common power quality monitors only measure rms-voltages during dip Voltage phasors interesting / required for analysis / statistics conversion!

  15. Rms  phasors algorithm 2 STEPS: • step 1: determine type of dip • from relation between the three rms-voltages • number of possible dips is limited • step 2: determine dip characteristics & phasors • 3 rms-voltages & dip type  the characteristic voltage V and phase-angle jump  can be estimated

  16. Step 1: determine dip type (1) • A : three-phase drops • C, E and G: two-phase drops • B, D and F: single-phase drops Umin Umax  Voltage Dip Type

  17. Step 1: determine dip type (2) 1 & 3 phase drops 2 & 3 phase drops

  18. Step 2: determine characteristic voltage & phase angle jump 3 rms voltages U1, U2, U3 dip type C characteristic voltage & phase angle jump voltage phasors

  19. RMS  Voltage Phasorsfor PP measurements • no zero-sequence component • 3 phasors makes up closed triangle  phasors can easily be estimated out of 3 rms voltages with trigonometry equations

  20. Conclusions

  21. Evaluation of algorithms • check of twenty voltage dips in Belgium HV-stations • accuracy better than 5% for 95% of dips: acceptable for statistical purposes • fine tuning of algorithms in progress

  22. Monitor spec’s Best solution: recording of rms & phasor evolution during voltage dip Alternative: only rms recordings  to be able to apply conversion algorithms • all three rms-voltages must be recorded during voltage dip • snapshot of three rms-voltages when maximum depth is reached  if necessary: adapt firmware of monitor

  23. Connection of monitor (rms) phase-to-phase measurement (PP) • phasors can be calculated with trigonometry equations (closed triangle) • propagation of voltage dips can be estimated accurately • no indication about the origin phase-to-ground measurement (PN) • often preferable because indication about origin • propagation can be estimated with proposed algorithms

  24. Voltage dip statistics (depth & length) • phase-to-ground  phase-to-phase statistics • not comparable & should never be mixed • always mention which connection is considered in tables or statistics (PG or PP) • avoid phase-to-ground statistics • too pessimistic view • especially in impedance grounded systems • zero-sequence component is removed in Yd and Dy transformers

  25. Voltage dip statistics (depth & length) • phase-to-phase statistics are preferable • can be derived from phase-to-ground measurements with proposed algorithms • alternative: statistics with characteristic magnitude • characteristic magnitude can be estimated with proposed algorithms, • remains invariable during propagation (primary or secondary side trafo) • is independant of connection

  26. Thank You!

More Related