MiCOM P632
Tripping Characteristics
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The maximum phase current IP,max.y of the selected transformer end is used to track a first-order thermal replica according to IEC 255-8. The following parameters will govern the tripping parameters:

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The set thermal time constant (τ) of the protected object THRM1: Tim.const.1,>Ibl PSx

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The tripping threshold Δϑtrip set at THRM1: Rel. O/T trip PSx

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The accumulated thermal load Δϑ0

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The updated measured coolant temperature Θc for the protected object

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The maximum permissible coolant temperature Θc,max set at THRM1: Max.perm.cool.tmpPSx

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The maximum permissible object temperature Θmax set at THRM1: Max.perm.obj.tmp.PSx

The object temperature is calculated from the current IP,max.y and can be displayed at THRM1: Object temperat.,TH1. The coolant temperature is either measured via the PT 100 input or via a 20 mA input, or a default temperature value is used instead. This choice is governed by the setting at THRM1: Select CTA PSx. The coolant temperature is displayed at THRM1: Coolant temp. TH1. The difference between the settings for the maximum permissible temperatures of the protected object and the coolant can be displayed at THRM1: O/T f.Iref persist 1.

The tripping characteristics are then defined by the equation:

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The setting for the operating mode selects an “absolute” or “relative” replica. If the setting is for “Absolute replica”, the P632 will operate with a fixed trip threshold Δtrip of 100 %.

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Fig. 3-133: Tripping characteristic of the thermal overload protection.

Tripping characteristics apply to Δϑ0 = 0 % and identical settings for the maximum permissible coolant and the updated measurement of the object temperature.