GE T60 Instruction Manual page 87
Transformer protection system
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- Instruction manual (796 pages) ,
- Communications manual (532 pages) ,
- Instruction manual (771 pages)
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CHAPTER 3: INSTALLATION
Figure 3-24: Contact input connected to a contact output with resistor (R2) across the input
Application example
This example is for illustrative purposes only and the calculations present the worst-case scenario. In practice, the value of
debounce time can be lower.
Contact input ON state impedance used in the calculation of the discharge period is based on the following table.
Table 3-4: Discharge period
Battery voltage (V)
Input impedance (kΩ)
130
50
250
97
Debounce time setting = 2 ms
Assume a stray capacitance of 0.1 μF.
Assume an initial voltage across the stray capacitance "Vinitial" = 19 V (Vthreshold - 65 V), where Vthreshold = 84 V. The
initial voltage Vinitial depends on values of impedance of R1 and contact inputs when the contact input is OFF (non-
activated state).
Therefore, discharge time constant (τ) =50 kΩ *0.1 μF = 5 ms.
Discharge period t is calculated from the following equation:
Therefore, in this example the contact inputs operate.
To prevent this operation, the debounce time must be increased to 4 ms (set debounce time as per the following table) or
insert a resistor less than or equal to "R" as calculated later.
Table 3-5: Typical debounce time setting
Stray capacitance (μF)
Battery voltage (V)
0.05
130
0.1
130
0.2
130
0.05
250
T60 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
Vthreshold = (Vbatt - VInitial) *e^ (-t/τ)
84 = -149 *e^ (t/0.005)
T = -0.005 * ln (84/149) = 0.0029 s
Debounce time (ms)
2
4
6
3
WIRING
3
Eq. 3-1
3-27
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