06 sep674 ret670 thermal overload protection

8/17/2019 06 SEP674 RET670 Thermal Overload Protection

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1MRG019264

Transformer protection RET670Thermal overload protection

Substation Automation Products


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Chapter 06

© ABB GroupSeptember 10, 2015 | Slide 3

Application thermal overload protection

Temporary overloading necessary in stressedsituations

Not possible to design the system to manageall situations

Temporary overload not harmful

Hard decision for operator to disconnect thetransformer

Consequences of overload

Degrading in the quality of the transformer oil

Forced aging of insulation

Increase risk of internal faults

Hot spots within the transformer

Degrade paper insulation


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Chapter 06


Based on measuring the true RMScurrent

Uses the largest phase current tocalculate the heat content

Two time constants (i.e. ONAN or OFAF)

Possibility to adjust the time constants athigh and/or low currents

Binary inputs to

select time constant

change reference settings

empty heat content

block the function

Thermal overload protection Application


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Chapter 06


SMAI

TR PTTR

49 Ith

SMAI

SMAIΣ

SMAI

TR PTTR

49 Ith

TR PTTR

49 Ith

Thermal overload protection Application

Number of instances: Customized: 0 – 6

Pre-configured:

Included: 1

Optional: < 1


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Chapter 06


The relative final temperature (heatcontent) is expressed as:

The actual temperature (heat content) iscalculated as:

if (heating)

or:

if (cooling)

HEATCON> ALARM1 Alarm> ALARM2 Alarm

> ITrip Trip

I_MEASURE I > ITrip Start

Monitored data

Analog Binary

HEATCON

Operating characteristicsThermal overload protection


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Chapter 06


Present time to operation is calculated as:

The time to lockout release is calculatedas:

TTRIP If Start

Monitored data

Analog Binary

If TTRIP < Warning WARNING

TRESLO If Trip



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Chapter 06


t[min]

Θ[%]

ResetLockoutTemp

Tau 1

Alarm 1 Alarm 2

~ IRef

WARNING

ResLo

~ ITrip

100%

~ IBase 1

Current step

START/RESET

TRIP and

LOCKOUT

TripTemp

Estimated time to trip

Estimated time to reset

TTRIP

TRESLO

Rated power

ThetaInit



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Chapter 06


Final temp >

Trip Temp

Actual Temp >

Alarm X Temp

Calc of final

temp

Calc of heat

content

Actual Temp >

Trip Temp

Actual Temp


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Chapter 06


First instance ofTR PTTR

Thermal overload protection settingsOverview


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Chapter 06


Base current 1

Time constant 1

Rescaling of Tc if I >

Rescaling percentage

Rescaling of Tc if I <


Cooling input low

Thermal overload protection settingsTime constant 1


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Chapter 06


Cooling input high

Base current 2

Time constant 2

Rescaling of tc if I >


Rescaling of tc if I <


Thermal overload protection settingsTime constant 2


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Chapter 06


Trip and supervision

Steady state trip level

Alarm 1 – level warning

Alarm 2 – level warning

Lockout reset level

Warning – time to trip

Thermal overload protection settingsTrip and supervision


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Chapter 06


Test/Functions status/Currentprotection/ThermalOverload2TimeConst (PTTR,49)

TRIP

START

ALARM1

ALARM2

LOCKOUT

WARNING

Monitored dataThermal overload protection


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Chapter 06


Test/Functions status/Currentprotection/ThermalOverload2TimeConst(PTTR,49)

I-MEASURE Measured current (% ofrated current)

HEATCONT – Heat content of thetransformer (%)

TTRIP – Estimated time to trip (min)

TRESLO – Estimated time to reset (min)

TTRIPCAL – Time status to trip

0: Not active

1: Long time

2: Active

TRESCAL – Time status to reset

0, 1 or 2

Monitored dataThermal overload protection

06 sep674 ret670 thermal overload protection

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