GE T60 Instruction Manual page 388

5.6 GROUPED ELEMENTS
The element has a linear reset characteristic. The reset time can be programmed to match the cooling characteristics of the
protected equipment. The element will fully reset from the trip threshold in
may be used as an instantaneous element with no intentional time delay or as a Definite or Inverse timed element.
The characteristics of the inverse curves are shown below.
DEFINITE TIME:
For the definite time curve, T(sec.) = TD multiplier. For example, setting the TD multiplier to 20 results a time delay of 20
seconds to operate when above the Volts/Hz pickup setting. Instantaneous operation can be obtained the same way by
setting the TD multiplier to "0".
INVERSE CURVE A:
The curve for the volts/hertz inverse curve A shape is derived from the formula:
5
where: T = Operating Time
TDM = Time Delay Multiplier (delay in seconds)
V = fundamental RMS value of voltage (pu)
F = frequency of voltage signal (pu)
Pickup = volts-per-hertz pickup setpoint (pu)
The volts/hertz inverse A curves are shown below.
5-252
Figure 5–130: VOLTS PER HERTZ SCHEME LOGIC
TDM
------------------------------------------------ - when
T
=
2
V
  Pickup
--- - ⁄
 
F
Multiples of volts per hertz pickup
Figure 5–131: VOLTS-PER-HERTZ CURVES, INVERSE CURVE A
T60 Transformer Protection System
VOLTS/HZ T-RESET
V
--- - >
Pickup
F
1
–
5 SETTINGS
seconds. The V/Hz element
(EQ 5.45)
Time
delay
setting
830738A1.CDR
GE Multilin