Relay Settings Calculations

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

Technical Data of the Lines

Main Line
Conductor TypeACSR Lynx
Length27.8 km
TypeZM Type Tower
Positive sequence impedance 0.1583 + 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 impedance 0.1583 + 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 the normal tap (12 no.) 10.15% / 13.20 %
Type of tap changer On load
the voltage at the maximum tap (V) 145200
Voltage at the 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 the normal tap (12 no.) 10.15% / 13.20 %
Type of tap changer On load
The voltage at the maximum tap (V) 145200
Voltage at the 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

11 kV Outgoing Protection Settings

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

126 thoughts on “Relay Settings Calculations”

  1. 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 …

      1. this file is for our users only, you should enroll in any of our training packages like DIGSI 4, DIGSI 5, PCM600, ETAP, ABB PCM 600 ..

  2. I need protection grading, Simulation excel, for 33/11kV voltage level protection . OC (IDMT + HIGH STAGE) AND EF (same as OC) only.. please help.

    1. Protection Engineer

      Details have been sent to your email with subject: Relay Settings Calculations / Helpful Excel Spreadsheets for Protection Engineers

  3. Please share relay calculation excel sheet.
    Relay Settings Calculations / Helpful Excel Spreadsheets for Protection Engineers

    1. Protection Engineer

      This product is free for our customers only, and unfortunately, your email is not on our customer list. You can buy any of our training packs (DIGSI 4, DIGSI 5, IEC 61850, ETAP, PSCAD, …), then you can access our free files.

  4. How i can download this document? I work at power company, my company use some protection relay, SEL, Siemens, Schneider, GE,…I need this document, pls send to my email. Thanks

  5. Sebe Mulumbwa

    Kindly assist with transformer diff, line protection, etc PDF and Excel calculations. I will be grateful.

    1. Protection Engineer

      sent to ur email
      please check your email for the topics of the Helpful Excel Spreadsheets for Protection Engineers

  6. Hello Sir/Madam,

    I need HT Motor Protection Relay setting calculations for Siemens 7SJ61, 7SJ66, and 7SK80

  7. Hello Sir/Madam.

    I need HT Motor Protection Relay Setting Calculations for Siemens 7SJ61, 7SJ66, and 7SK80.

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