Presentation on theme: "TRANSFORMER PROTECTOR"— Presentation transcript:
1TRANSFORMER PROTECTOR TRANSFORMER EXPLOSION PREVENTIONResearch and ExperimentsDr. Guillaume PerigaudTPC808 Russell Palmer Rd.Kingwood, TX 77339Office:Fax:
2TWO WAYS OF INVESTIGATION Numerical SimulationsExperimentsMTH model(Magneto Thermo Hydrodynamic )2002 Tests in EDF (Electricité de France)Upgrade to account for pressure wave propagationCompressible Effects(shock waves)HeatTransfers2004 Tests at CEPEL(Centro de Pesquisas de Energia Eletrica)Arc EffectsTwo-PhaseFlowsViscosityGravity
6TRANSFORMER EXPLOSION PREVENTION Pressure Wave/Structure InteractionDepressurisation SetDesigned as TransformerTank Structure Weakest Point in term of Rupture Inertia to Dynamic PressureVery Fast Depressurisation Set Opening (less than 2 ms)TRANSFORMER PROTECTOR OPERATIONTank DepressurisationEnergy Evacuation Duringthe Whole Arcing (more than 100ms)Transformer Tank Saved
7Gas bubbles appear on the arc path (1 to 2.3 m3 i.e. 35 to 80 ft3). GAS GENERATIONVery violent physical phenomena (tank acceleration up to 400g where g=9.81 m/sec² i.e. 30 ft/sec²).Gas bubbles appear on the arc path (1 to 2.3 m3 i.e. 35 to 80 ft3).Gas gets under pressure (from 100 bar/sec to 5,000 bar/sec i.e ,500 Psi/sec to 72,500 Psi/sec)The pressure rise up to 14 bar (200 Psi).Movie :Test Number:3Date:06/04/2002Test Reference:2002Arc Current:2500 AArc Duration:79 msCamera Speed:3000 frames/second
8PRESSURE DYNAMIC BEHAVIOR DURING A LOW IMPEDANCE FAULT The pressure variation is a very transient phenomena that is non-spatially uniform.Pressure waves are acoustic waves, which propagate throughout the tank at finite speed, the speed of sound in the oil (1,200 m/sec i.e ft/s).The tank structure has a large influence on the local pressure.
10 TP OPERATION 1/ Pressure rises 2/ Explosion of the disk, depressurisation, evacuation of the oil-gases mixture3/ Opening of the airisolation shutter4/ Nitrogen injectionN25/ Explosive gases production isstopped
11TP OPERATION Test Movie 20 MVA TRANSFORMER TEST Test Number: 30 Date: 12/07/2004Test Reference:30_T1C_140_83_VACArc Current:14000 AArc Duration:83 msArc Location:Opposite the TP close to the bottomTP Operation:Under VacuumCamera Speed:25 frames/second
12PRESSURE VARIATION DURING THE TP OPERATION Test Number: 32Arc Current: AArc Duration: 83 msArc Location: At the tank cover in the TP vicinity (A)Under atmospheric PressurePressure Gradient3900 bar/sec(56,550 Psi/sec)Pressure peak7.5 bar (109 Psi)
13DEPRESSURISATION KEY OF SUCCESS To create an opening for the pressure to be evacuated before the transformer tank sees the increased static pressure :The tank rupture inertia > 60 milliseconds for pressure peaks up to 14 BAR (200 PSI) and pressure gradients from 100 bar/sec (14,500Psi/sec) to 5,000 bar/sec (75,000 Psi/sec);TP inertia to open < 2 milliseconds.
14TRANSFORMER TANK RESPONSE TO THE PRESSURE RISE Dynamic BehaviorStatic BehaviorVery transient phenomenon, from 25 bar/s, (360 psi) to 5000 bar/sec (72,500 psi/sec)Very slow phenomenon, below bar/sec (360 psi/sec)Pressure spatially non-uniformPressure spatially uniformVery High Local Overpressure for less than 60 milliseconds(>+14 bar, +200 Psi)Low Global Overpressure for more than 200 milliseconds(<+1.2 bar, 17 Psi)Local Mechanical StressesUniform and IsotropicMechanical stressesTank withstands the local high overpressure because of walls’ elasticityTank does not withstand the global low overpressure in spite of the walls’ elasticity
15TRANSFORMER DIMENSIONS ARE MORE IMPORTANT THAN POWER (MVA) CEPEL tests T3 transformer = 8.5m (28 ft)Since the pressure wave propagate at a finite speed, the bigger the transformer, the longer the propagation time to reach the TP.
16Shock Wave Simulation on a Very Large Transformer
17750 MVA SIMULATIONThe transformer dimensions are the parameters that matter the most;The maximum distance between an arc and the TP is about 15 m (49 ft);The extrapolation ratio between the CEPEL 20 MVA and the 750 MVA transformers is only 2, not 35;The arc current is chosen equal to 70 kA during 70 ms.
18750 MVA SIMULATION Magnetic Core Arc Location S6 S7 S8 3.8 m (12.66 ft)Ø 0.3 m (12 in)161718S2S334567891011S1TP9.14 m (30 ft)0.5m (1.66ft)0.5m (1.66ft)Magnetic Core5.2 m (17.33 ft)4.8 m(15.75 ft)Ø 0.05 m (1.97 in)124.2 m (14 ft)2S4S5Arc Location11514131 m(3.33 ft)9.9 m (33 ft)
21750 MVA SIMULATIONThe study of the pressure and velocity maps explains the depressurisation process;The TP activates in 18 milliseconds;The transformer is depressurised in 60 milliseconds;Pressure peaks are located in the transformer body, but in the bushings as well because of geometry influence on the pressure.
23CONCLUSIONThe experimental tests proved that the previous transformer explosion prevention strategy is efficient: the TP prevented the transformer explosion each time during the experiments.The simulations take into account the compressible effects and describe very accurately the pressure wave propagation .The pressure waves propagate at finite speed so that the transformer dimensions are the only parameter that matters in an explosion prevention strategy.The numerical simulations showed that only one Depressurisation Set is sufficient to depressurise a 750 MVA transformer in milliseconds.Despite this result, 2 Depressurisation Sets equip the transformers from 500 MVA.