06 SEP674 RET670 Thermal Overload Protection

Substation Automation Products

Transformer protection RET670 Thermal overload protection

1MRG019264

Chapter 06

Contents

© ABB Group September 10, 2015 | Slide 2



Application



Operating characteristics



Logical Diagram



Settings



Monitored data

Application thermal overload protection





Temporary overloading necessary in stressed situations 

Not possible to design the system to manage all situations



Temporary overload not harmful



Hard decision for operator to disconnect the transformer

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 

© ABB Group September 10, 2015 | Slide 3

Chapter 06

Degrade paper insulation

Chapter 06

Thermal overload protection Application 

Based on measuring the true RMS current



Uses the largest phase current to calculate the heat content



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



© ABB Group September 10, 2015 | Slide 4

Possibility to adjust the time constants at high and/or low currents

Binary inputs to 

select time constant



change reference settings



empty heat content



block the function

Chapter 06

Thermal overload protection Application 

49

Number of instances: 

Customized: 0 – 6



Pre-configured:

Ith

TR PTTR SMAI

Σ

SMAI SMAI

49

Ith

TR PTTR

SMAI

© ABB Group September 10, 2015 | Slide 5

49

Ith

TR PTTR



Included: 1



Optional: < 1

Chapter 06

Operating characteristics Thermal overload protection 

The relative final temperature (heat content) is expressed as:

Monitored data Analog I_MEASURE



Binary

I > ITrip  Start

The actual temperature (heat content) is calculated as:

HEATCON if 

> ALARM1  Alarm > ALARM2  Alarm > ITrip  Trip

(heating) or:

HEATCON if © ABB Group September 10, 2015 | Slide 6

(cooling)

Chapter 06

Operating characteristics Thermal overload protection



Present time to operation is calculated as:

Monitored data Analog Binary TTRIP

 If Start

If TTRIP < Warning  WARNING 

The time to lockout release is calculated as:

TRESLO

© ABB Group September 10, 2015 | Slide 7

 If Trip

Chapter 06

Operating characteristics Thermal overload protection Estimated time to trip TTRIP Θ[%] Tau 1

~ IBase 1 TripTemp

~ ITrip ~ IRef

Rated power

100 % Alarm 2 Alarm 1 ResLo ResetLockoutTemp

Estimated time to reset TRESLO ThetaInit

t[min ]

Current step START/RESET © ABB Group September 10, 2015 | Slide 8

WARNING

TRIP and LOCKOUT

Chapter 06

Simplified Logical Diagram Thermal overload protection I-MEASURE

I3P

Cooling Enmult Reset

Final temp > Trip Temp

START

Calc of heat content

HEATCONT

Calc of final temp

Management of parameters Actual Temp > Alarm X Temp

ALARM1 ALARM2

Actual Temp > Trip Temp

TRIP

Actual Temp < Trip Temp

LOCKOUT S R TTRIP

Calc time to trip Calc time to reset lockout

© ABB Group September 10, 2015 | Slide 9

WARNING TRESLO

Thermal overload protection settings Overview

Chapter 06

First instance of TR PTTR

© ABB Group September 10, 2015 | Slide 10

Chapter 06

Thermal overload protection settings General General

Operation On/Off Base current Reference current Factor for Ref current

Initial heat content (at start and reset of the function ) Trip pulse length

© ABB Group September 10, 2015 | Slide 11

Chapter 06

Thermal overload protection settings Time constant 1

Cooling input low

Base current 1 Time constant 1 Rescaling of Tc if I > Rescaling percentage Rescaling of Tc if I < Rescaling percentage

© ABB Group September 10, 2015 | Slide 12

Chapter 06

Thermal overload protection settings Time constant 2

Cooling input high

Base current 2 Time constant 2 Rescaling of tc if I > Rescaling percentage Rescaling of tc if I < Rescaling percentage

© ABB Group September 10, 2015 | Slide 13

Chapter 06

Thermal overload protection settings Trip and supervision Trip and supervision

Steady state trip level Alarm 1 – level warning Alarm 2 – level warning Lockout reset level Warning – time to trip

© ABB Group September 10, 2015 | Slide 14

Chapter 06

Monitored data Thermal overload protection 

© ABB Group September 10, 2015 | Slide 15

Test/Functions status/Current protection/ThermalOverload2Time Const (PTTR,49) 

TRIP



START



ALARM1



ALARM2



LOCKOUT



WARNING

Chapter 06

Monitored data Thermal overload protection 

Test/Functions status/Current protection/ThermalOverload2TimeConst (PTTR,49) 

I-MEASURE Measured current (% of rated current)



HEATCONT – Heat content of the transformer (%)



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 

© ABB Group September 10, 2015 | Slide 16

0, 1 or 2

Chapter 06

© ABB SA-TGroup Training September 10, 2015 | Slide 17