GOOSSENS (BE) Session 2 – Block 3 Barcelona May Improved Assessment of Voltage Dips with Common Monitoring Devices M. Bollen, A. Robert & P. Goossens Session 2 Paper No5

GOOSSENS (BE) Session 2 – Block 3 Barcelona May Voltage Dip Representation Why Voltage Phasors? Limitations of RMS-representation

GOOSSENS (BE) Session 2 – Block 3 Barcelona May Dip produced by single phase fault Depth = 36 %Depth = 16 % single phase dip2-phase dip

GOOSSENS (BE) Session 2 – Block 3 Barcelona May Dip produced by single phase fault Dy primary side trafosecondary side trafo MAGNITUDE (PP) -U1 = 94% -U2 = 80% -U3 = 93%

GOOSSENS (BE) Session 2 – Block 3 Barcelona May Why phasors? indication about origin –fault type and characteristics dip propagation –through transformers –connection : star or delta depth: phase-to-ground  phase-to-phase

GOOSSENS (BE) Session 2 – Block 3 Barcelona May Improved Dip Characterisation (M. Bollen) Voltage Type: A, B, C, D, E, F & G Characteristic Magnitude V Phase Angle Jump 

GOOSSENS (BE) Session 2 – Block 3 Barcelona May 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)

GOOSSENS (BE) Session 2 – Block 3 Barcelona May Dip Type A Origin: balanced three phase fault « A »

GOOSSENS (BE) Session 2 – Block 3 Barcelona May Dip type B, C & D « B » « C » « D » origin: single phase fault star connection origin: 2-phase fault, star connection or single phase fault, delta connection 2-phase fault, delta connection

GOOSSENS (BE) Session 2 – Block 3 Barcelona May Dip Type E, F & G Connection: star Origin: 2-phase to ground Connection: delta Behind Dy or Yd trafo « E »« F » « G »

GOOSSENS (BE) Session 2 – Block 3 Barcelona May Propagation of voltage dips Yd Dy I II III Fault TypeDip Location IIIIII 3-phaseAAA 3-phase-to-groundAAA 2-phase-to-groundEFG 2-phaseCDC 1-phase-to-groundBCD line & phase voltages are swapped: rms-voltages changes !

GOOSSENS (BE) Session 2 – Block 3 Barcelona May V Characteristic Voltage Characteristic Magnitude V & Phase Angle Jump   A, C, D, F, G: MIN(3 U PN & 3 U PP )  B, E: first remove U 0 = Invariable of connection type (PP  PG) and location (primary  secondary trafo) V

GOOSSENS (BE) Session 2 – Block 3 Barcelona May Voltage Dip Conversion Algorithms RMS  PHASORS

GOOSSENS (BE) Session 2 – Block 3 Barcelona May Why conversion algorithms? Common power quality monitors only measure rms-voltages during dip Voltage phasors interesting / required for analysis / statistics conversion!

GOOSSENS (BE) Session 2 – Block 3 Barcelona May 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

GOOSSENS (BE) Session 2 – Block 3 Barcelona May 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

GOOSSENS (BE) Session 2 – Block 3 Barcelona May Step 1: determine dip type (2) 1 & 3 phase drops2 & 3 phase drops

GOOSSENS (BE) Session 2 – Block 3 Barcelona May Step 2: determine characteristic voltage & phase angle jump 3 rms voltages U1, U2, U3 dip type C characteristic voltage & phase angle jump voltage phasors

GOOSSENS (BE) Session 2 – Block 3 Barcelona May RMS  Voltage Phasors for 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

GOOSSENS (BE) Session 2 – Block 3 Barcelona May Conclusions

GOOSSENS (BE) Session 2 – Block 3 Barcelona May 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

GOOSSENS (BE) Session 2 – Block 3 Barcelona May 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

GOOSSENS (BE) Session 2 – Block 3 Barcelona May 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

GOOSSENS (BE) Session 2 – Block 3 Barcelona May 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

GOOSSENS (BE) Session 2 – Block 3 Barcelona May 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

GOOSSENS (BE) Session 2 – Block 3 Barcelona May Thank You!