This technical report refers to the electrical protections of all 132kV switchgear. These settings may be revaluated during the commissioning, according to actual and measured values. Protection selectivity is partly considered in this report, and could be also revaluated. Names of parameters in this calculation may differ from those in appropriate device.

Technical Data of the Lines

Main Line
Conductor TypeACSR Lynx
Length27.8 km
TypeZM Type Tower
Positive sequence impedance0.1583 + j0.4004 (0.431 ∠68.4°) Ω/ km
Zero sequence impedance0.3246 + j1.228 (1.27 ∠75.2°) Ω/ km
Current capacity (A)487
Next Line
Conductor TypeACSR Lynx
Length36 km
TypeZM Type Tower
Positive sequence impedance0.1583 + j0.4004 (0.431 ∠68.4°) Ω/ km
Zero sequence impedance0.3246 + j1.228 (1.27 ∠75.2°) Ω/ km
Current capacity (A)487
SEL 311 – Line Protection

Protection Settings Calculations for Lines

SEL-311C Distance Protection Settings
Distance Zone
Non-Homogeneous Correction Angle
Load Impedance and Load Encroachment
Power Swing Detection/ Out of Step Detection
Switch on to Fault (SOTF
Fuse failure scheme OR Loss of Potential (LOP)
SEL-351A Back-up Over Current Settings
Back up over current settings

Technical Data of the Power Transformers

Transformers – 1
Type of cooling ONAN / ONAF
Vector Group Dyn11
Rated Voltage HV V 132000
Rated Voltage LV (V) 11500
Full Load current HV ( A) 87.48 / 113.72
Full Load current LV (A) 1004.12 / 1305.35
Rated Power ( MVA) 20 / 26
% impedance at normal tap (12 no.) 10.15% / 13.20 %
Type of tap changer On load
Voltage at maximum tap (V) 145200
Voltage at minimum tap (V) 118800
Transformers – 2
Type of cooling ONAN / ONAF
Vector Group Dyn11
Rated Voltage HV V 132000
Rated Voltage LV (V) 11500
Full Load current HV ( A)43.7 / 56.9
Full Load current LV (A) 502 / 652.7
Rated Power ( MVA) 10 / 13
% impedance at normal tap (12 no.) 10.15% / 13.20 %
Type of tap changer On load
Voltage at maximum tap (V) 145200
Voltage at minimum tap (V) 118800
SEL-787 Transformer Protection Relay

Protection Settings Calculations for Power Transformers

SEL-787 Transformer Differential Protection
Differential Pick-up
Slope-1 Setting
Slope-2 Setting
Differential Unrestrained (U87P (Un-restrained Differential Pick-up) )
2nd HARMONIC
5th HARMONIC

SEL-351A Transformer HV Over Current
Pick-up Setting
51PP (for phase fault element)
51GP (for earth fault element)
Time Multiplier Setting

SEL-551C Feeder Over-Current and Earth Fault

11kV Outgoing Protection Settings

SEL-551C LT Over-Current and Earth Fault
CDG21 LT Neutral Standby AC series Earth Fault

3 Replies to “Relay Settings Calculations”

  1. avatar

    I need transformer differential protection in micom and siemens siprotec relay

  2. avatar

    Please share some relay setting calculations excels ,pdf or doble or RIO test kit calculation files if you have any so that we could purchase it on this website ?

    THANKS …