Schweitzer Engineering Laboratories SEL-387E - Level 1 Time Delay (24 D1 D); Level 1 Volts;Hertz Element Pickup (24 D1 P); Level 2 Composite Curve Shape (24 CCS); When 24 CCS = DD

Date Code 20080110 Protection Functions 3-65
SEL-387E Instruction Manual
transformer windings are delta connected, the relay cannot measure the phase voltage directly,
but needs to calculate the voltage values. The relay calculates the differences between the
voltages presented to the relay from the wye-wye connected PTs and thus the voltage connected
to the power transformer windings. Set 24WDG = D. Thus, voltage values selection to calculate
the volts/hertz protection and sequence components is based on the 24WDG selection; phase to
phase for 24WDG = D and phase-to-neutral for 24WDG = Y.
Level 1 Volts/Hertz Element Pickup (24D1P)
Range
: 100–200%
Apply the Level 1 element as an overexcitation alarm. The 24D1P setting defines the percent
volts/hertz alarm pickup. The 24D1 Relay Word bit asserts without time delay when the
measured transformer volts/hertz exceeds the 24D1P setting.
Level 1 Time Delay (24D1D)
Range
: 0.04–400.00 s
The 24D1T Relay Word bit asserts 24D1D seconds after 24D1 assertion if the measured
volts/hertz remains above the 24D1P setting.
Level 2 Composite Curve Shape (24CCS)
Range
: OFF, DD, ID, I, U
The 24CCS setting defines the overexcitation tripping element time-delay characteristic or
disables the element when set to OFF.
Set 24CCS = OFF if you do not require Level 2 volts/hertz protection. When 24CCS = OFF, the
other Level 2 settings are hidden and do not need to be entered.
When 24CCS = DD:
The element operates with a dual-level, definite-time characteristic.
Level 2 Pickups (24D2P1 and 24D2P2)
Range : 100–200% (for 24D2P1)
Range : 101–200% (for 24D2P2)
The SEL-387E Relay asserts the 24C2 Relay Word bit without time delay when the transformer
volts/hertz exceeds either the 24D2P1 or 24D2P2 setting.
Level 2 Time-Delays (24D2D1 and 24D2D2)
Range
: 0.04–400.00 s
If the volts/hertz percentage is greater than the 24D2P1 setting, but less than the 24D2P2 setting,
the relay asserts the 24C2T Relay Word bit in 24D2D1 seconds.
When the volts/hertz percentage is greater than the 24D2P2 setting, the relay asserts the 24C2T
Relay Word bit in 24D2D2 seconds. The setting 24D2P1 must be less than the setting for
24D2P2.