reactor differential protection calculation

SETTING RECOMMENDATION

APPLN/2012

For UPPTCL UNNAO SS

765kV 3*63 MVAR BUS REACTOR PROTECTION

CONFIDENTIAL The information contained in this document is not to be communicated either directly or indirectly to any person not authorised to receive it.

 

SSEETTTTIIN NG G CCAALLCCU ULLAATTIIO ON N FFO ORR  776655kkVV                     33**6633M ON NSS     MVVAARR  BBU USS  RREEAACCTTO ORR  PPRRO OTTEECCTTIIO

Customer :

M/s. L&T

Client

:

UPPTCL

Project

:

765/400kV UNNAO SUB STATION.

Prepared By

Sreenatha Rao R.S.N.V

Date

24/01/2012

Approved By

Arunachalam Ananthkumar

Revision

Rev. 3

Page 1 of 9

3x63 MVAR BUS REACTOR PROTECTION Reactor Differential Protection (87RA) - Main 1 Type of Relay used = P632 Reactor Capacity in MVAR = 189 Voltage level in kV = 765 Phase side - winding a CT Ratio (Phase side) - Pri = 600 CT Ratio (Phase side) - Sec = 1 Neutal side - winding b: CT Ratio (Neutral side) - Pri = 600 CT Ratio (Neutral side) - Sec = 1 = 189 * 10^3/ √3 * 765 Full load Current of the Reactor in Amps = 142.64 = 6 times of rated current (assumed) Charging current of the reactor = 6 * 142.6 Charging current in Pri. in Amps = 855.86 = 856/600 Charging current in Secondary (If) in Amps = 1.43 Supportive Calculations: Amplitude matching factor for winding a and b: Full load current of the reactor in Amps = 142.64 = 142.6/600 Eqv. Secondary current in Amps = 0.24 = 1/0.2 Required ratio compensation = 4.21 Biased Differential Settings: Idiff> = 0.1 Iref m1 = 0.2 m2 = 0.8 IR,m2 = 1.5 Iref Idiff>> = 8 Iref Idiff>>> = 10 Iref Vector Group end a-b = 0 Op. mode rush restraining = Not Phase selective Rush I(2f0)/I(f0) = 20% Over Flux blocking enable = Yes Ov I(5f0)/I(f0) = 20% Zero Seq. Filter end a = No Zero Seq. Filter end b = No Stability Calculations: Max. Fault current in kA = 40 kA = 40kA/(600) Eqv. Secondary current in Amps = 66.67 A 66.67*4.21 = Current in Iref at end a & end b = 280.42 = 280.42-280.42 Differential Current Idiff> in Amps = 0.00 = (280.42+280.42)/2 Restraining Current IR in Amps = 280.42

For M/s. UPPTCL - UNNAO 3x63 MVAR BUS REACTOR SETTINGS REV 3

Page 2 of 9

M/s AREVA T&D INDIA LTD, 19/1 G.S.T ROAD, PALLAVARAM, CHENNAI-600043

The Differential current required for the relay to operate = Idiff> (1-0.5 * m1) + (m2 * Bias current) +(IR,m2 * (m1-m2)) 0.1*((1-0.5)*0.2)+(0.8*280.42)+(1.5*(0.2The differential current required for the relay to = 0.8)) operate in Amps = 223.53 As the restraining current is 280.42A, and the differential current is 0.00A the operating point lies below the characteristic curve. Reactor Differential Protection (87RB) - Main 2 Type of Relay used = P141 Reactor Capacity in MVAR = 189 Rated Voltage in kV = 765 Phase side CT primary in Amps = 600 Phase side CT secondary in Amps = 1 Settings: Type of Impedance = High impedance = 142.64 Reactor full load Current in Amps IFL Rated current at secondary = 0.24 Reactor Charging current in Amps = 855.86 Charging current in Sec in Amps = 1.43 = 40% of full load current Pick up current in Amps I> = 0.40*142.6 = 57.06 = 57.1/600 Equivalent secondary current in Iref = 0.095 Inputs from CT calculation sheet: CT secondary resistance Rct in Ohms = 1.1 Lead length assumed in kM = 0.2 Resistance of 6 Sqmm Cable in Ohms = 3.746 Ohms/KM = 0.2 * 3.746 Lead Resistance RL in Ohms = 0.749 Exc. Current of CT @ Vk in Amps Ie = 0.1 CT Knee point Voltage Vk = 1600 No. of CTs connected for protection = 2 = 0.04 Metrosil current in mA IM Vs Calculation: = If *(RCT + 2RL) Voltage developed across the relay (Vs) in Volt = 1.43*(1.1 + 2 * 0.749) = 3.71 Rstab calculation: = (Vs/Is) Stabilizing Resistor Value Rstab in ohms = (3.71/0.095) = 39.0 The Resistance value to be set is 39 Ohms. Primary Operating current (Iop): = (Vs/Vk)* Ie Exc. Current of CT @ Vs in Amps Ies = (3.71/1600) * 0.1 = 0.0002317 For M/s. UPPTCL - UNNAO 3x63 MVAR BUS REACTOR SETTINGS REV 3

Page 3 of 9

M/s AREVA T&D INDIA LTD, 19/1 G.S.T ROAD, PALLAVARAM, CHENNAI-600043

= CT Ratio ( I> + nIes + Im) Min.primary Operating current in A Iop = 600*(0.095+(2*0.0002317)+0.04*10^-3) = 57.36 Tee Differential Protection (87TEE1) - Main 1 Type of Relay used = P122 Rated Voltage in kV = 765 CT ratio in Primary in Amps = 3000 Rated current(assumed as CT ratio) in Amps = 3000 Settings: Type of Impedance = High impedance Full load Current in Amps = 3000 Rated current at secondary = 1 Maximum fault current in Amps = 40000 Fault current in Sec in Amps = 13.33 = 40% of full load current Pick up current in Amps = 0.40*3000 = 1200 = 1200/600 Equivalent secondary current in Iref = 0.4 Inputs from CT calculation sheet: CT secondary resistance Rct in Ohms = 5.3 Lead length assumed in kM = 0.2 Resistance of 6 Sqmm Cable in Ohms = 3.746 Ohms/KM = 0.2 * 3.746 Lead Resistance RL in Ohms = 0.749 Exc. Current of CT @ Vk in Amps Ie = 0.02 CT Knee point Voltage Vk = 2826 No. of CTs connected for protection = 3 = 1.22 Metrosil current in mA IM Vs Calculation: = If *(RCT + 2RL) Voltage developed across the relay (Vs) in Volt = 13.33*(5.3 + 2 * 0.749) = 90.65 Rstab calculation: = (Vs/Is) Stabilizing Resistor Value Rstab in ohms = (90.65/0.4) = 227 The Resistance value to be set is 227 Ohms. Primary Operating current (Iop): = (Vs/Vk)* Ie Exc. Current of CT @ Vs in Amps Ies = (90.65/2826) * 0.02 = 0.0006415 = CT Ratio ( I> + nIes + Im) Min.primary Operating current in A Iop = 3000*(0.4+(3*0.0006415)+1.22*10^-3) = 1209.43

For M/s. UPPTCL - UNNAO 3x63 MVAR BUS REACTOR SETTINGS REV 3

Page 4 of 9

M/s AREVA T&D INDIA LTD, 19/1 G.S.T ROAD, PALLAVARAM, CHENNAI-600043

Tee Differential Protection (87TEE2) - Main 2 Type of Relay used = P633 Rated Voltage in kV = 765 CT ratio in Primary in Amps = 3000 Rated current(assumed as CT ratio) in Amps = 3000 Supportive Calculations: Amplitude matching factor for winding a,b and c: Full load current in Amps = 3000 = 3000/3000 Eqv. Secondary current in Amps = 1 = 1/1 Required ratio compensation = 1 Biased Differential Settings: Type of Impedance = Low Impedance Iref Idiff> = 0.2 m1 = 0.2 m2 = 0.8 Iref IR,m2 = 1.5 Iref Idiff>> = 10 Iref Idiff>>> = 12 = 0 Vector Group end a-b = 0 Vector Group end a-c Op. mode rush restraining = Without Rush I(2f0)/I(f0) = 20% Over Flux blocking enable = No Ov I(5f0)/I(f0) = 20% Zero Seq. Filter end a = No Zero Seq. Filter end b = No Zero Seq. Filter end c = No Stability Calculations: Max. Fault current in kA = 40 kA = 40kA/(3000) Eqv. Secondary current in Amps = 13.33 A = 13.33*1 Current in Iref at end a & end b = 13.33 = 13.33-13.33 Differential Current Idiff> in Amps = 0.00 = (13.33+13.33)/2 Restraining Current IR in Amps = 13.33 The Differential current required for the relay to operate = Idiff> (1-0.5 * m1) + (m2 * Bias current) +(IR,m2 * (m1-m2)) The differential current required for the relay to = 0.2*((1-0.5)*0.2)+(0.8*13.33)+(1.5*(0.2-0.8)) operate in Amps = 9.95 As the restraining current is 13.33A, and the differential current is 0.00A the operating point lies below the characteristic curve.

For M/s. UPPTCL - UNNAO 3x63 MVAR BUS REACTOR SETTINGS REV 3

Page 5 of 9

M/s AREVA T&D INDIA LTD, 19/1 G.S.T ROAD, PALLAVARAM, CHENNAI-600043

Bus Reactor Backup Protection Backup Overcurrent and Earthfault Protection (50/51N) Relay type = MiCOM P141 CT Ratio - Primary in A = 600 CT Ratio - Secondary in A = 1 Full Load Current in Amps = 142.64 Over current Setting: The Over current setting shall be set for the 105% of reactor current when bus voltage drops to 90%. = 1.05*(MVAR/(√3*(0.9*Rated voltage)) Pick up setting in primary in Amps = 1.05*(189*10^6)/(√3*(0.9*765*10^3)) = 165 Pick up setting in secondary in Amps = 0.28 Delay type = DT Operating time in msec = 500 Earth fault Setting: = 50% of full load current /Reset ratio Pick up setting in Amps = (0.5*142.6)/0.95 = 75.08 Pick up setting in secondary in Amps = 0.13 Delay type = DT Operating time in msec = 1000 Note: In earlier recommendations it was recommended for Sensitive Earth fault type as we were not able to set under Earth fault. Now the wiring to the relay shall be connected to 'Earth fault terminals.

For M/s. UPPTCL - UNNAO 3x63 MVAR BUS REACTOR SETTINGS REV 3

Page 6 of 9

M/s AREVA T&D INDIA LTD, 19/1 G.S.T ROAD, PALLAVARAM, CHENNAI-600043

3 * 63MVAR, 765kV BUS REACTOR OC & EF COORDINATION CURVES

Page 7 of 9

BUS REACTOR OVER CURRENT CURVE 100 100.00

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For M/s. UPPTCL - Unnao SS OC EF Coordination Curves for 1*63MVAR BUS REACTOR Rev 3.

Page 8 of 9

OC

Fault current (A) AREVA T&D INDIA LIMITED, 19/1, G.S.T.ROAD, PALLAVARAM, CHENNAI - 43.

EARTH FAULT CURVE 10

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For M/s. UPPTCL - Unnao SS OC EF Coordination Curves for 1MVA SST Rev 3

Page 9 of 9

EF

Fault current (A) AREVA T&D INDIA LIMITED, 19/1, G.S.T.ROAD, PALLAVARAM, CHENNAI - 43.