Motor protection example

Assume you have a motor rated 500 HP, .95 power factor & 90 % efficiency energized from a 4.16 Kv source, using a microprocessor motor protection relay, provide the typical settings.The full load current can be taken from the motor nameplate as well as the service factor. The motor full load current can be calculated from the following: I = 500 (.746)/1.732 (4.16)(.85)(.9) =60 amps

Motor and Line Data FunctionsFunction Description Adjustment / Display Range Setting Increments SettingMotor Nameplate FLA 1 2000A, adjustable between 50-100% of Max Amp Rating.FLA must be programmed Upper limit of range automatically adjusts 1 60for relay to function downward as Service factor is increased.

Motor Nameplate 1.00 - 1.30 SF .05 1

Overload Class During Start NEMA / UL Class 5 20 5 Class 20

Overload Class During Run NEMA / UL Class 5 30 5 Class 10

Overload Reset 0 = Manual,1 = Auto,2 = Disabled Overload 1 1

kV Voltage Input (nominal line, Medium Voltage) .60 15kV .01 4.16

Line Frequency 50 or 60 Hz 60

Acceleration Time 0-300 seconds [0=Disabled] 1 30

Current Imbalance Trip % 0.1 - 30% of FLA [0=Disabled] 1(%) 15

Current Imbalance Trip Delay 1 - 20 seconds 1 (Second) 5

Over Current Trip % 0,.50 300% of FLA [0=Disabled] 1 (%) 200

Over Current Trip Delay 1 - 20 seconds 1 8

Under Current % 0, 10 90% of FLA [0=Disabled] 1 (%) 35

Under Current Trip Delay 1 - 60 seconds 1 15

Stall Detection Trip Level 0.100 600% of FLA [0=Disabled] 5 (%) 600

Stall Detection Trip Delay 1 - 10 seconds 1 4

Peak Current Trip % 0.800 1400% [0=Disabled] 10(%) 1000 (%)

Peak Current Trip Delay 0..01 - .5 seconds .01 .05

Ground Fault Current Trip Value 0.5 90% of CT Value [0=Disabled] 1 (%) 50Ground Fault Current Trip Delay 1 60 seconds 1 5

Voltage Protection SettingsVoltage Imbalance Trip % 0.1 30% [0=Disabled] 1 (%) 20

Voltage Imbalance Trip Delay 1 20 seconds 1 10

Over Voltage Trip % 0.1 10% [0=Disabled] 1 (%) 5

Over Voltage Trip Delay 1 20 seconds 1 10

Under Voltage Trip on Start % 0.1 20% [0=Disabled] 1 (%) 20

UV Trip on Start Delay 1 180 seconds 1 20

Under Voltage Trip on Run % 0.1 20% [0=Disabled] 1 (%) 20

UV Trip Delay during Run 1 20 seconds 1 10

Phase and Frequency Protection SettingsPhase Rotation Trip 0.1 or 2 0=Disabled, 1=ABC, 2=ACB] 1 2

Phase Rotation Trip Delay 1 20 seconds 1 2

Phase Loss Trip and Delay 0.1-20 Seconds [0= Disabled] 1 5

Over Frequency Trip Limit 0.1 10Hz [0=Disabled] 1 1

Over Frequency Trip Delay 1 20 seconds 1 5

Under Frequency Trip Limit 0.1 10Hz [0=Disabled] 1 1

Under Frequency Trip Delay 1 20 seconds 1 5

Motor KW Trip 0-2.0 = Disabled,1 = Over KW Trip,2 = Under KW Trip 1 0

Motor KW Trip Point 20 100% of full load KW (disabled) 1% 20(%)

Motor KW Trip Delay Time 1 999 minutes (disabled) 1 1

Power Factor Trip Range 0.1 3 [0=Disabled, 1=lag, 2=lead, 3= lead/lag] 1 2

Power Factor Trip Point .01 1 .01 .10

Power Factor Trip Delay Time 1 20 seconds 1 10

Power Factor Current Direction 0 - 1, [0=Normal, 1= Reversed] 1 1

Lockout / Inhibit SettingsCoast Down (Back Spin) Lockout Timer 0 = Disabled, or 1 - 60 minutes 1 minute 1

Maximum Starts per Hour 0 = Disabled, or 1 10 starts 1 5

Minimum Time Between Starts Inhibit 0 = Disabled, or 1 - 60 minutes 1 minute 12

Note: NEMA Class trip curves are based on a common tripping point of 600% of motor Full Load Amps (FLA). Curves vary by the amount of time before the unit trips. As an example, a Class 20 curve will trip in 20 seconds at 600% of FLA. Another example, Class 10 will trip in 10 seconds at 600% of FLA.

PT Value:1-200 (: 1) 1:1 = direct voltage input, 2-200: 1 = kV Voltage Input 1 40 (4160/104) V

CT Value: 5-2000 (:5) 5 60

Number of Turns through CT: 1 5 (in 1 increments) 1

Generator protection example

Ratings of generators: Rated output (eg. 1,120 MVA), Maximum output (1230 MVA), Rated rotation speed (300 rpm), Power factor (0.9), Number of poles (2), Terminal voltage (27), Rated Armature current (23949), Maximum Armature current (26302), Short-circuit ratio (> or = 0.5), Hydrogen gas pressure (0.52 Mpa G), Insulation type (F), Temperature rise class (B), Cooling method (Stator: direct water), Efficiency (99 %), Hydrogen consumption (12 m3/day).

Functional Specifications of generator protective relayNOMINAL SYSTEM FREQUENCY SETTING RANGE.............................................50 or 60 HzRATED PRIMARY INPUT CURRENT OF PHASE AND NEUTRAL CTS .........1 - 9999A in 1A stepsRATED PRIMARY SYSTEM PHASE-TO-PHASE VOLTAGE OF PTS......2 655 kV in .0.1 kV stepsRATED PT SECONDARY LINE-TO-LINE VOLTAGE ...............................50 125 V in 1 V stepsLOW SET OVERCURRENT ELEMENTCharacteristic: .......................................................................................Definite time or inversePickup: ...........................................................................................1.0 2.5 pu of rated generator currentTime delay: ...........................................................................................0.05 30.0 seconds (at 5pu Igen)HIGH SET OVERCURRENT ELEMENTCharacteristic: .......................................................................................Definite timePickup: ............................................................................................1.0 9.9pu of rated generator currentTime delay: ...........................................................................................0.05 3.0 seconds (at 5pu Igen)CURRENT UNBALANCE ELEMENTMaximum negative sequence current rating;.................................0.05 0.5pu of rated generator currentTime multiplier of I2 t curve ...................................................................5 80 secondsCooling time to rated.............................................................................10 1800 secondsAlarm level pickup.................................................................................0.03 0.5pu generator currentAlarm level time delay...........................................................................1 100 secondsREVERSE POWER ELEMENT PICKUP ......................................0.02 to 0.2pu rated generator currentTime delay ...........................................................................................1 100 secondsLOSS OF FIELD ELEMENTMho circle size ..........................................................................50 300% of rated generator impedanceMho offset .................................................................................5 50% of rated generator impedanceTime delay ............................................................................................0.2 60 secondsIntegration time .....................................................................................0 10 secondsVOLTAGE ELEMENTSCharacteristic ........................................................................................Over, Under or Over+UnderPick-up level.......................................................................................1 50% change from rated voltageTime delay ............................................................................................0.1 60.0 secondsFREQUENCY ELEMENTSCharacteristic ........................................................................................Over, Under or Over+UnderPick-up level..........................................................................................0.05 9.99Hz from nominalTime delay ............................................................................................0.1 60.0 secondsTHERMAL IMAGE ELEMENTTrip level ...............................................................................................Fixed at 110% ratedThermal time constant of alternator ......................................................1 400 minutesPre-alarm level......................................................................................50 110% of ratedUNDERPOWER ELEMENT PICKUP LEVEL ..........................................................0.05 1.00 of rated power outputTime delay ............................................................................................0.1 60.0 secondsUNDERIMPEDANCE ELEMENTSPickup level...........................................................................................01 1.0 pu rated impedanceTime delay ............................................................................................0.02 9.99 secondsFIRST LEVEL OVEREXCITATION ELEMENTCharacteristic ........................................................................................InversePickup level...........................................................................................1.0 - 2.0 puTime multiplier.......................................................................................0.5 5.0SECOND LEVEL OVEREXCITATION ELEMENTCharacteristic ........................................................................................Definite timePickup level...........................................................................................1.0 - 2.0 puTime multiplier.......................................................................................0.1 60.0 seconds95% STATOR GROUND FAULT ELEMENTSPickup level.....................................................................................5 99% Rated zero sequence voltageTime delay ............................................................................................0.05 99.0 seconds100% STATOR GROUND FAULT ELEMENT3rd Harmonic Pickup level ..............................................................1 30% Rated zero sequence voltageTime delay ............................................................................................0.05 99.0 seconds

Typical Settings IEEE No. Function Typical Settings and Remarks24 Overexcitation PU: 1.1*VNOM/60; TD: 0.3; reset TD: 5 alarm P.U.: 1.18*VNOM/60 alarm delay: 2.5s

25 Synchronism Check Max Slip: 6RPM; Max phase angle error: 10 Max VMAG error: 2.5% VNOM

32 Reverse Power (one stage) PU: turbine 1% of rated; 15 s . PU: Reciprocating engine: 10% of rated; 5 s

32-1 Reverse Power (non-electrical, trip supervision) PU: same as 32; 3 s

40 Loss-of-field (VAR Flow approach) Level 1 PU: 60% VA rating; Delay: 0.2s; Level 2 PU: 100% VA rating: 0.1s

46 Negative Sequence overcurrent I2 PU: 10% Irated; K=10

49 Stator Temperature (RTD) Lower: 95C; upper: 105C

50/87 Differential via flux summation Cts PU:10% INOM or less if 1A relay may be used

50/27 IE Inadvertent Energization Overcurrent with 27, 81 50: 0.5A (10% INOM) 27: 85% Supervision VNOM (81: Similar)

51N Stator Ground Over- current (Low, Med Z Gnd, PU: 10% INOM; curve: EI; TD: 4. Inst: Phase CT Residual) none. Higher PU required to coordinate with load. No higher than 25% INOM.

50/51N Stator Ground Over- current (Low, Med Z Gnd, P.U.: 10% INOM; Curve EI**, TD4; Inst Neutral CT or Flux Summation CT) 100% INOM. Higher PU if required to coordinate with load. No higher than 25% INOM.

51GN, 51N Stator Ground Over- current (High Z Gnd) PU: 10% IFAULT at HV Term.; Curve: VI***; TD:4. 51VC Voltage Controlled overcurrent PU: 50% INOM; Curve: VI***; TD: 4. Control voltage: 80%VNOM.

51VR Voltage Restrained overcurrent PU: 175% INOM; Curve: VI***; TD: 4. Zero Restraint Voltage: 100% VNOM L-L

59N, 27-3N, 59P Ground Overvoltage 59N: 5% VNEU during HV terminal fault; 27-3N: 25% V3rd during normal operation; TD: 10s 59P: 80% VNOM

67IE Directional O/C for Inadvertent Energization PU: 75-100% INOM GEN; Definite Time (0.1- 0.25 sec.) ; Inst: 200% INOM GEN

81 Over/under frequency For Generator protection: 57, 62Hz, 0.5s; For Island detection condition: 59, 61Hz, 0.1s87G Generator Phase Differential Fixed: 0.4A; or Variable: Min P.U.: 0.1 * Tap; Tap: INOM; Slope: 15%

87N Generator Ground Variable: Min P.U.: 0.1 times tap; Slope 15%; Differential Time delay: 0.1s; choose low tap 67N: current polarization; time: 0.25A; Curve: VI***; TD: 2; Instantaneous: disconnect

87UD 13 Unit Differential Min PU: 0.35*Tap; Tap: INOM; Slope 30%

**: EI: extremely inverse. ***: VI: very inverse.

13/11/10