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. Names of parameters in this calculation may differ from those in the appropriate device.   

Technical Data of the Lines

Main Line

Conductor Type	ACSR Lynx
Length	27.8 km
Type	ZM Type Tower
Positive sequence impedance	0.1583 + j0.4004 (0.431 ∠68.4°) Ω/ km
Zero sequence impedance	0.3246 + j1.228 (1.27 ∠75.2°) Ω/ km
Current capacity (A)	487

Next Line

Conductor Type	ACSR Lynx
Length	36 km
Type	ZM Type Tower
Positive sequence impedance	0.1583 + j0.4004 (0.431 ∠68.4°) Ω/ km
Zero sequence impedance	0.3246 + j1.228 (1.27 ∠75.2°) Ω/ km
Current capacity (A)	487

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

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

11kV Outgoing Protection Settings

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