07 SEP674 RET670 Overexcitation Protection
Transcript of 07 SEP674 RET670 Overexcitation Protection
-
8/17/2019 07 SEP674 RET670 Overexcitation Protection
1/17
1MRG019263
Transformer protection RET670Overexcitation protection
Substation Automation Products
-
8/17/2019 07 SEP674 RET670 Overexcitation Protection
2/17
Chapter 07
© ABB GroupSeptember 10, 2015 | Slide 2
Contents
Application
Operating characteristics
Logical diagram
Settings
Monitored data
-
8/17/2019 07 SEP674 RET670 Overexcitation Protection
3/17
Chapter 07
© ABB GroupSeptember 10, 2015 | Slide 3
Application overexcitation protection function
The overexcitation is not an internal transformerfault, although it can lead to one
The peak flux density Bmax is directly proportionalto induced voltage E, and inversely proportional to
frequency f, turns n and area AE = 4.44 × f × n ×B max × A
Overexcitation results from excessive voltage orbelow-normal frequency or a combination of thetwo, such that the volts/Hz exceed ratedvalues
Overexcitation of a transformer can occur wheneverthe ratio of the pu voltage to pu frequency (V/Hz)exceeds its rating of 1.05 pu on transformer base atfull load or 1.1 pu at no load
-
8/17/2019 07 SEP674 RET670 Overexcitation Protection
4/17
Chapter 07
© ABB GroupSeptember 10, 2015 | Slide 4
Overexcitation will cause
overheating
increase in magnetizingcurrents
increase in vibration andnoise
IEC 60076-1Continuously 10% above ratedvoltage at no load and ratedfrequency
Overexcitation of power transformers Application
-
8/17/2019 07 SEP674 RET670 Overexcitation Protection
5/17
Chapter 07
© ABB GroupSeptember 10, 2015 | Slide 5
Overexcitation protection function Application
The function is measuring the terminal voltage and current. It uses thefundamental frequency components.
Calculates the relative Volts per Hertz ratio.
Two operate characteristics (IEEE / Taylor made)
Operating range:Uph-ph > 70% of rated value (if below, the algorithm is not calculating theoverexcitation) and
33< f
-
8/17/2019 07 SEP674 RET670 Overexcitation Protection
6/17
Chapter 07
© ABB GroupSeptember 10, 2015 | Slide 6
Overexcitation protection function Application
OEX PVPH
2 4 U/ f>
YY
∇
OEX PVPH
24 U/ f>
SMAI
SMAI
YY
∇
SMAI Σ
SMAI
Number of instances: < 2
Analog measurements must not be taken from awinding where OLTC is located
Measures input voltage
Single phase-to-phase voltage or threephase voltage (positive sequence)
Calculates the induced voltage E if theleakage reactance (and current) is known
otherwise the terminal voltage is used
The current measurement should have the samecomponent selection as voltage (positivesequence or delta current)
OEX PVPH
24 U/f>
YY
∇
SMAI
-
8/17/2019 07 SEP674 RET670 Overexcitation Protection
7/17
Chapter 07
© ABB GroupSeptember 10, 2015 | Slide 7
The relative excitation M (relative V/Hz) isexpressed as:
If M < V/Hz> then the transformer is notoverexcited (< 1.0)
V/Hz>: the maximum continuously allowedno-load voltage at rated frequency, set asa % of UBase/fr (default: 110 %)
The relative overexcitation is thus defined
E max
0 Mmax - V/Hz>
V/Hz>>
V/Hz> E (only if f = fr = const)
tMax
overexcitationunder -excitation
Delay
Overexcitation M-V/Hz>
Excitation MM=V/Hz>
tMin
harmful
Overexcitation protection functionOperating characteristics
-
8/17/2019 07 SEP674 RET670 Overexcitation Protection
8/17
Chapter 07
© ABB GroupSeptember 10, 2015 | Slide 8
0 Mmax - V/Hz>
V/Hz>>
V/Hz> Emax E (only if f = fr = const)
tMax
inverse delay
overexcitationunder -excitation
Delay
Overexcitation M-V/Hz>
Excitation MM=V/Hz>
tMin
Operate characteristic
tMax: Maximum cut-off operate time at lowdegree of overexcitation
tMin: Minimum cut-off operate time at high
degree of overexcitationBeyond M = V/Hz>> the operate timewill always be tMin
Overexcitation protection functionOperating characteristics – IEEE curve
-
8/17/2019 07 SEP674 RET670 Overexcitation Protection
9/17
Chapter 07
© ABB GroupSeptember 10, 2015 | Slide 9
0
V/Hz>
Mmax - E maxcont
V/Hz>>
tMin
tMax
Delay
Overexcitation M-E maxcont
Excitation M
under-excitation overexcitation
The interval between M = V/Hz> andM = V/Hz>> is automatically divided into5 equal subintervals
6 operating time points has to be defined
Straight line between the points tocalculate operating time
tMax: Maximum cut-off operate time
tMin: Minimum cut-off operate time
Beyond M = V/Hz>> the operate timewill always be tMin
Overexcitation protection functionOperating characteristics – Tailor made curve
-
8/17/2019 07 SEP674 RET670 Overexcitation Protection
10/17
Chapter 07
© ABB GroupSeptember 10, 2015 | Slide 10
E max
0 Mmax - V/Hz>
V/Hz>>
V/Hz> E (only if f = fr = const)
tMax
overexcitationunder -excitation
Delay
Overexcitation M-V/Hz>
Excitation MM=V/Hz>
tMin
harmful
Overexcitation causes overheating
An exponential cooling feature isimplemented
i.e. shorter operating time if the transformer
has been exposed for overexcitation beforeand not yet reached normal temperature
tCooling: Time constant (default setting1200 seconds (20 minutes))
AlarmPer cent of operate level (heat content,THERMSTA)
Time delay
Reset input to clear heat content
Cooling and alarmOperating characteristics
-
8/17/2019 07 SEP674 RET670 Overexcitation Protection
11/17
-
8/17/2019 07 SEP674 RET670 Overexcitation Protection
12/17
Chapter 07
© ABB GroupSeptember 10, 2015 | Slide 12
First instance ofOEX PVPH
Advancedsettings
Overexcitation protection function settingsOverview
-
8/17/2019 07 SEP674 RET670 Overexcitation Protection
13/17
Chapter 07
© ABB GroupSeptember 10, 2015 | Slide 13
Leakage reactance of adjacentwinding
Operation On/Off Base values
Alarm in % of operate level
(9000 s ~ 2,5 h)
Voltage and current selection:ph-ph or positive sequence
NB : MeasusedU andMesururedI must be set to thesame value (ILxILy is calculated
internally)
Trip pulse length
Overexcitation protection function settingsGeneral
-
8/17/2019 07 SEP674 RET670 Overexcitation Protection
14/17
Chapter 07
© ABB GroupSeptember 10, 2015 | Slide 14
Characteristic IEEE/Tailor made
Trip delay:
Core cooling time constant
Base values
Operate level:- No load and rated frequency- High level where tMin is used
- Minimum- Maximum
Tailor made curve
IEEE curve
Overexcitation protection function settingsCharacteristic
-
8/17/2019 07 SEP674 RET670 Overexcitation Protection
15/17
Chapter 07
© ABB GroupSeptember 10, 2015 | Slide 15
Test/Functions status/Voltageprotection/overexcitation(PVPH,24)
Trip
Start
Alarm
TMTOTRIP – Calculated time totrip (s)
VPERHZ – V/Hz (pu)
THERMSTA – Thermal status in% of trip level
Monitored data
-
8/17/2019 07 SEP674 RET670 Overexcitation Protection
16/17
Chapter 07
© ABB GroupSeptember 10, 2015 | Slide 16
Monitored data
Time
V/Hz>>
tMax
tMin
THERMSTA=100% and TMTOTRIP=0
THERMSTA 100% (if no trip)
-
8/17/2019 07 SEP674 RET670 Overexcitation Protection
17/17
Chapter 07
© ABB GroupSeptember 10, 2015 | Slide 17© SA-T Training© SA-T TrainingSeptember 10, 2015 | Slide 17