Arcteq Generator Commander, Instruction Manual

Page: 179 / 561

Where:
• I
1
= Calculated positive sequence current of the measured RMS phase currents
• I
2
= Calculated negative sequence current of the measured RMS phase currents
• k
NPS
= Correction factor of the NPS current biasing to the equivalent current calculation
• I
MAX
= Measured maximum of the three TRMS phase currents
The thermal image status (θ
t%
, in percentages of the maximum thermal capacity used) calculation is
based on the sum of the long and short time constant thermal image calculation:
The basic operating principle of the thermal replica is based on the nominal temperature rise, which is
achieved when the protected object is loaded with a nominal load in a nominal ambient temperature.
When the object is loaded with a nominal load for a time equal to its heating constant tau (τ), 63% of
the nominal thermal capacity is used. When the loading continues until five times this given constant,
the used thermal capacity approaches 100 % indefinitely but never exceeds it. With a single time
constant model the cooling of the object follows this same behavior, the reverse of the heating when
the current feeding is completely zero.
Genera Generattor Commander or Commander
Instruction manual
Version: 2.07
© Arcteq Relays Ltd
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