Volts Per Hertz Scheme Logic - GE T60 Instruction Manual

5.6 GROUPED ELEMENTS
5
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 set-
ting the TD multiplier to "0".
INVERSE CURVE A:
The curve for the volts/hertz inverse curve A shape is derived from the formula:
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)
5-266
Figure 5–131: VOLTS PER HERTZ SCHEME LOGIC
------------------------------------------------ - when V TDM
T
=
2
V
  Pickup
--- - 
1
–
 
F
T60 Transformer Protection System
seconds. The V/Hz element
VOLTS/HZ T-RESET

--- - Pickup
F
5 SETTINGS
(EQ 5.45)
GE Multilin