524474424-Tan-Delta-Testing-on-Rotating-Machines.pdf

Tan-Delta-Testing-on-Rotating-Machines

1. Tan Delta
Testing on Rotative Machines
Webinaron TanDelta Testingon RotativeMachines
MSc. Andrej Šepčić
RAM
[email protected]

2. Rotarymachines(generatorsandmotors)areessential
inpowergenerationandmanyindustrialapplications
soweneedtobesuretheyareingoodhealth
Webinaron TanDelta Testingon RotativeMachines

3. 3
CAPACITANCE & Tan delta wetest in orderto…
evalutatethe rotary machine insulationquality,
thatdecreasedue to:
-age
-water content
-humidity
-impurities
-thermaldeterioration
-corona discharges
-air pockets
Itis a comparative test:
-othervoltages(tip-up / tip-down)
-previoustests PhotobyISA Archive–Italy September2015
Webinaron TanDelta Testingon RotativeMachines

4. Tan Delta (DF, PF) and Capacitance(C) is verypopularand widelyaccetabletechnique to assesthe insulationof Rotary Machines
Itis an offline -AC test, whichshows usthe state of insulationaswhenthe generator is working. Itshows usthe presentstate of insulation
Alterative to thiswouldbe an online monitoring system, thatwouldfollow and show the state of insulationin time 24/7
Testisusedtocheck:
•AgingoftheInsulation
•Contaminaionofinsulation
•Mechanicaldeformation
•…
Always the test is donebetween2 differentvoltages(for thiswemodellingthe insulationlike a capacitor)
Webinaron TanDelta Testingon RotativeMachines

5. What is the insulation ?
By the IEEE definition:
Suitable non-conductive material or combination of materials,
which provide electrical insulation
between two parts at different potential levels.
So we have two different voltages, each on one side,
and we have a dielectric in the middle -sounds familiar?
Webinaron TanDelta Testingon RotativeMachines

6. We model the insulation with a capacitor
ThisisaCapacitor
Thesetwoplatescanactuallybe:
1.2phasesofaStatorofMotororGenerator
(forexamplePhAandPhB)
2.TheStatorandthegroundofMotororGenerator
Actually
wheneveryou have two different electrical potentials
–and a dielectric in between –wehave a capacitor–
somethingthat can holdan electrical charge
DielectricisourInsulation!
So from now on
whenwe say dielectric
wemean insulation
Webinaron TanDelta Testingon RotativeMachines

7. What is the formula for capacitance of the capacitor
This is a formula for two paralell platescapacitor
(there are many other types of capacitors butfor the sake of simplicity we’ll use the most simple one)
Here we can see that if after having measured C for the first time (thushaving obtained our referencevalue)
and having measured C again after a while, if there are discrepancies the possible reason for that could be:
1.Permittivitychanged:
meansthatthe dielectric changed its dielectrical properties
àpotential problems with Insulation(contamination, PD)
2.A or d changed:
àproblems with the internal geometry (something phisically moved aka. Mechanical Deformation)
3.Alsotwoor threeparameterscan changeàthenitcouldbe thatinsulationand geometrychanged
C=capacitanceinFarads
ε=permittivityofdielectric(absolute,notrelative)
A=reaofplateowerlapinm²
d=distancebetweenplatesinm
Webinaron TanDelta Testingon RotativeMachines

8. Ideal CapacitorIn a capacitor,
currentand voltage are shifted in phase 90 degrees,
whichis the definition of Ideal capacitor:
–Current is leading –Voltage is lagging
Thatis becausein Ideal capacitor
thereis no «in phase» current(resistive current)
running throughthe insulation.
WHY ? –Becauseitisideal
IfwehaveIdeal, youmust haveguessed
thatthereis alsoa Real Capacitor:
the one wherephaseshift is lessthan90 degrees.
Youwillseelaterthat
Tan Delta is actuallyquantifying
the differencebetweenIdeal and Real Capacitor
AC
We need to keep in mind:
Ideal Capacitorconected
to an AC source
Webinaron TanDelta Testingon RotativeMachines

9. Real Capacitor
Like thereis notideal
man or a woman, or a coach or a collaborator
Weall know thatthereis no suchthingasan «ideal» capacitor
Thatis becauseasmuchasthe insulationtriestherewillalwaysbe
at leastsome finite in phase(resisitivecurrent) running from one
plateto another
Anotherway howto explainthisis to say:
Thereis no materialin the universethathasinfinite resistance.
Sohowshouldweaproachthis:
Real Capacitor connectedto an AC source
Resistanceisverybig (MΩ)
AC
R>>
IR<<
But not0
Webinaron TanDelta Testingon RotativeMachines

10. Ideal (perfect) Insulation (Capacitor)
V (applied)
ITOTAL
IR = 0
I (capacitive)
AC
V
I Total
Capacitance& Tanδ
Webinaron TanDelta Testingon RotativeMachines

11. Real Insulation
V (applied)
IR = 0
I (capacitive)
=
I Total
AC
V
I Total
AC
VIcIR
I Total
IC
V (applied)
ITOTAL
IR
Ideal Insulation (perfect)
Webinaron TanDelta Testingon RotativeMachines

12. IR–Resistive current is the
reason why our insulation heats up, and that
heat deteriorates the electrical insulation
And that it creates
a vicious cycle
(a chain reaction)
that can lead
to dramatic failures
P ="#IR#cos'
In orderto keepGeneratorsrunningsmothly, weneedto the state of insulation
H
E
A
T
Webinaron TanDelta Testingon RotativeMachines

13. So What is Tan Delta?
Tan Delta is
the ratio of in-phase (resistive) current
to the 90 degree (capacitive) current.
Tan Delta is also refeed to
as Dissipation Factor
(Tan Delta = DF)
!"#$=&!
&"
f
!"#$='"
(=1
*(+
Webinaron TanDelta Testingon RotativeMachines

14. f
In addition to Tan Delta (DF) another term is also used:
Power factor (PF) is
the ratio of resistive current to the total current.
for the δvalue up to 10 °,
PF and Tan Delta can be considered the same in value
I TOT = IR+Ic≈Ic( if δis very small)
PF =cosf="!
""#"= #!
$$
Power Factor
One could say:
if 0123and PF are different
thentheinsulationisalreadycompromised
dueto thefactthattheangleistoohigh
45=tan$
1+:"#%$tan$=45
1−45%
AnguloTAN δAngulo90°COS ϕ
00,000000900,000000
0,20,00349189,80,003491
0,50,00872789,50,008727
10,017455890,017452
1,50,02618688,50,026177
20,034921880,034899
30,052408870,052336
40,069927860,069756
50,087489850,087156
Webinaron TanDelta Testingon RotativeMachines

15. What test sets and accessories do we offer for this type of test ?
STS x000 + TD 5000TDX 5000RCTD -Reactor
Webinaron TanDelta Testingon RotativeMachines

16. -Stator
-Rotor
-Windings
To avoidfailurein a rotatingmachine,
thesethreeelementshaveto be checkedperiodically
Elements inside a rotating machine
Webinaron TanDelta Testingon RotativeMachines

17. 18
Electrical construction of stator winding
VOLTAGE
1)Phase–Phase
2)Phase–Ground
3)Turn -Turn
INSULATION
a)Phase(*)
b)Ground (*) àGround wall
c)Turn
NOTE: (*) Testscouldbeperformedwithportableinstruments
Webinaron TanDelta Testingon RotativeMachines

18. Insulationsystem
Electrical model for test purpose:
Two insulation systems:
•Phase to ground insulation
C1, C2, C3
•Phase to phase insulation
C1-2C2-3 C1-3
Each capacitance models the electric
behavior of each phase.
If we cannot open star point,
what we measure is 3 phase to ground measurement
If we can do that, we can also measure phase to phase measurement of insulation
The overall status of the insulation is given by the Tan Delta measurement!
Webinaron TanDelta Testingon RotativeMachines

19. 20
Usualrepresentationof a rotative machine…
R
S
T
M
U
V
Wx
y
z
STAR POINTTERMINALS
STATOR WINDINGS
Webinaron TanDelta Testingon RotativeMachines

20. 21
…. ROTARY MACHINE INSULATION COULD BE SIMULATED
USING EQUIVALENT CAPACITANCES, LIKE ON A 3 WINDING TRANSFORMER
CR capacitancebetweenR terminal and ground
CS capacitancebetweenS terminal and ground
CT capacitancebetweenT terminal and ground
CR CS CT
CRS CST
CRS
The tests usuallyare doneon STATOR windings
according to norms:
IEC 60034-27-3 Dielectric dissipation factor
measurement on stator winding insulation of
rotating electrical machines
IEC60894 Guide for test procedure for
the measurement of loss tangent of coils and bars
for machine windings
and/or IEEE 286-2000 Tip-up Tan Delta Test
Webinaron TanDelta Testingon RotativeMachines
Standards

21. 22
DIELECTRIC LOSS IN INSULATION
Can bedividedin 3 components
Tanδ= Tanδc + Tanδp + TanδPD
Tanδc : Conducting Loss
Tanδp : Polarization Losses
TanδPD : Loss due to Partial Discharge
On rotary machines we often do a tip up test
(also tip down sometimes)
Tip up test:
we increase the voltage on Rotary Machine
progressively (usually 0.2 U/Un)
to see is we have issues in insulation.
It can show us
if there are some Partial Discharges
in the insulation or contamination.
If issues are found,
then we propose executing PD test
to determine better the state of the insulation.
Webinaron TanDelta Testingon RotativeMachines

22. Rotating machines exhibit big capacitance
0.1uF -2uF
E.g.
to test a generator with 1uF at 8kV and 50Hz
is required an Io generatorof2.5 A
This means: 20kVAof output power!
A similar generator is quite big and not easy to transport!
What about big Capacitance
<=IxXc="
&'="
%()'
&=Vx2πCC
4=VxI
Webinaron TanDelta Testingon RotativeMachines

23. The use of resonance phenomenon
is a possible solution to test high capacitive load
By using a parallel inductor (RCTD) a LC resonating load is created.
This permits to minimize the output power required by
TD5000 (max 300 mA)
RCTD5000 is composed by two inductors of 40H
12kV -each inductor can hold up to 1A
It is possible to connect one inductor or more
(4 inductors is the maximum allowed) in parallel
to the capacitive load –maximum 4 ARCTD unit
What about big Capacitance
Webinaron TanDelta Testingon RotativeMachines

24. LC resonating circuit
By connecting a proper numbers of inductors
the maximum impedance
can be set close to the test frequency (50Hz or 60Hz)
This system minimizes the current required by TD5000
and allows test of capacitance up to 3uF
to measure corresponding Tan Delta
(with decreased voltage we can go up to 200 uF)
Impedance
fftest
!=
1
2%&
'
(
)

I_Load
VTD
insulation
N number of inductors connected
L 40H
C capacitive load
Webinaron TanDelta Testingon RotativeMachines

25. Test mode
Two ways to use the device:
•Single Test
•Tip Up/Tip Down Test (Voltage Sweep): perform a series of tests increasing/decreasing the voltage with step of 20% rated voltage
Tip-Up Test according to IEEE 286 :
tip-up = TD Step (n) –TD Step (n+1)
On the Tip-Up test,
TD can vary between 0.5% and 1%
depending on the type of insulation
Webinaron TanDelta Testingon RotativeMachines

26. Measurement Setup … in the reality is veryeasy!
Communication
L1L2L3L4
Webinaron TanDelta Testingon RotativeMachines

27. MeasurementSetup –detailedconnection
Webinaron TanDelta Testingon RotativeMachines

28. Webinaron TanDelta Testingon RotativeMachines

29. 30
HOW TO EXECUTE THE TEST
1)Put togroundthe motor’s tank
2)Disconnectstar connection or star point
(ifpossible, otherwiseperform
onlythe 3phase general test to ground)
3)Connecttest set tothe motor
4)Executerequiredtests
The test can beperformedin foursteps:
NOTE:
with ISA STS5000 family youcouldperformcapacitanceand tan delta
measurementsin one shot only, with fantasticaccuracywhilesavingyoutime
PhotobyISAArchive–Italy September2015
Webinaron TanDelta Testingon RotativeMachines

30. 1)Ground the motor’stank
(the samegrounding shouldbe presentfor test sets and testedrotary machine)
R
S
T
M
U
V
Wx
y
z
HOW TO EXECUTE THE TEST
PhotobyISAArchive–ItalySeptember2015
Webinaron TanDelta Testingon RotativeMachines

31. 2) Ifpossible,
disconnectStar connection or star point,
otherwise perform only the 3phase general test to ground
R
S
T
M
U
V
Wx
y
z
So,
if the disconnection of Star Pointis not possible,
we can only do 1 test
HOW TO EXECUTE THE TEST
Webinaron TanDelta Testingon RotativeMachines

32. 33
3)Connecttest set tothe motor
HOW TO EXECUTE THE TEST
PhotobyISAArchive–ItalySeptember2015
Webinaron TanDelta Testingon RotativeMachines

33. 34
N^CCapacitanceDescriptionSTS 12kV
connectto
STSref.Method
1RbetweenR terminal and groundRCHGSTgA + B
2SbetweenS terminal and groundSCLGSTgA + B
3TbetweenT terminal and groundTCTGSTgA + B
4RSbetweenR and S terminalsRCHLUST A
5STbetweenS and T terminalsSCLTUST B
6TRBetweenT and R terminalsRCHTUST B
7RSTbetweenR, S, T terminals& groundPhasesCgenericGSTgA+B
4) WithSTS family youcouldperformat least7 differenttests,
Executethe followingtests:
HOW TO EXECUTE THE TEST
Webinaron TanDelta Testingon RotativeMachines

34. 35
EXAMPLE OF CONNECTIONS FOR TEST 1, 4, 6
Capacitanceand tandelta between:
-R terminal and Ground (CH –GSTgA+B)
-R & S terminal (CHL –UST A)
-R & T terminal (CHT –UST B) R
S
T
M
U
V
Wx
y
z
HOW TO EXECUTE THE TEST -details
Webinaron TanDelta Testingon RotativeMachines

35. 36
HOW TO EXECUTE THE TEST -details
Webinaron TanDelta Testingon RotativeMachines

36. Capacitanceand tandelta between:
-S terminal and Ground (CL–GSTgA+B)
-S & T terminal (CLT –UST B)
-R & S terminal (CHL –UST A)
37
EXAMPLE OF CONNECTIONS FOR TEST 2, 5, 4
R
S
T
M
U
V
Wx
y
z
HOW TO EXECUTE THE TEST -details
Webinaron TanDelta Testingon RotativeMachines

37. 38
EXAMPLE OF CONNECTIONS FOR TEST 3, 4, 5
R
S
T
M
U
V
Wx
y
z
Capacitanceand tandelta between:
-T terminal and Ground (CT –GSTgA+B)
-T & R terminal (CHT –UST A)
-S & T terminal (CLT –UST B)
HOW TO EXECUTE THE TEST -details
Webinaron TanDelta Testingon RotativeMachines

38. 39
EXAMPLE OF CONNECTIONS FOR TEST 7
NOTE:
The 2 short circuit connection (*) must be performed before starting the test
(*) (*)
Capacitanceand tandelta between:
-R, S, T terminal and Ground
(Cgeneric–GSTgA+B)
R
S
T
M
U
V
Wx
y
z
HOW TO EXECUTE THE TEST -details
Webinaron TanDelta Testingon RotativeMachines

39. 40
TAN DELTA Valuesshouldbeconstantovertime
IfTAN DELTA increase, itis indicationthat
-insulationoverheatingis occurring
-Windingis becomingcontaminated
IfTAN DELTA increased> 1% by initialvalue
àthereis a significantdeteriorationand thereis PD happening inside the insulation.
Thenwepropose doingPD test to makesurethe state of insulation
TAN DELTAInsulationtype
0,5%Modernepoxyresin& polyesterimpregnated
3 –5 %Asphalticmica windings
RESULTS
Webinaron TanDelta Testingon RotativeMachines

40. 41
Capacitanceand tandelta testedsimultaneously
TAN DELTA trend shows the averageconditionof the insulation,
sinceitmeasure the total dielectricloss in a winding
CTANDELTAIndication
DecreaseIncreaseGeneral thermaldeterioration
IncreaseIncreaseWindingcontaminated
or absorbedmoisture, PD present
NOTE: the above“decrease” and “increase” are referredto the references values(manufacturers, etc).
RESULTS valuesover time
Webinaron TanDelta Testingon RotativeMachines

41. Tip DownVoltage
N^[kV]
16
25
34
43
52
61
42
Formotorsover2300 V: Tip-upand tip-downtest
àIndicationofpartialdischargesin statorwinding
àWindinginsulationdeterioration
àQuality controltest: properimpregnationofinsulation
Tip Up Voltage
N^[kV]
11
22
33
44
55
66
RESULTS valuesover time
Webinaron TanDelta Testingon RotativeMachines

42. 43
TIPResult
0,5%New coils, or usedmotorsin goodconditions
1 %Usedmotorsin quitegoodconditions
> 1%Insulationisstartingtobedeteriorated
TIP % Value:
isthe differencesbetweenthe first and the last stepofthe tiptest
RESULTS tip-up / tip down test
Webinaron TanDelta Testingon RotativeMachines

43. Example 1a–6,6 kV Motor testing
Later we realised that
Motor and STS/TD were
not grounded inthe same point
Bad measurement. TotallyunexpectedvaluesofTanDelta andCapacitance
Webinaron TanDelta Testingon RotativeMachines

44. Finallywemanagedto getgood
andsensibleresult
Afterwhichweturnedto
Tip UpandTip Downtest
Example 1b–6,6 kV Motor testing
Webinaron TanDelta Testingon RotativeMachines

45. U [V]I [uA] C [nF]TD %PF %Rp["Ω]Rs[%Ω]ϕQFZ[%Ω]
1011,358,568184,60,2540,2546831,8891786.0489.8692392,62782.392
!"#$= E
FGHI!=90°−89.85447°=0.14553°
$=90°−ϕ
=1
314∙6831,889∙106T184,6∙10−9=0.254%!"#0.14553°= 0.254 %
Let us explain better some of the results we
obtain and use the formulas to see how can
they be used to confirm the tan delta
f
Webinaron TanDelta Testingon RotativeMachines

46. BTW youcanhaveyour./0!result inabsoluteorinpercentages–(0.00254 vs. 0.254 %)
Absolutebecauseand it is a non dimensional number (Amps divided with Amps)
Andfor smallangles(anddo notforgetwetalk aboutvalueslessthanfewdegrees) ./0!is a small number
δ(degrees)tanδinabsolutetanδinpercentages
0.10.001750.175
0.250.004360.436
0.50.008720.872
0.570.009950.995
So wesimplymultiply!"#$in absolute with a 100 and
from then on we express the value in percentagesmostly for practical reasons
!"#$=&!
&"
Why do we present the result in percentages
Webinaron TanDelta Testingon RotativeMachines

47. Tip UpandTip Downtest
isdoneat
20%, 40%, 60%, 80% and100%
NominalVoltage
andthenviceversa
Alsowedidtest withfreq. different
than nominal[57.7 Hz]
Sinceweare talkingabout
testing of Rotary Machine
Tan Delta values can go up to 3% or
even 5% depending on the
insulatingmaterial
Since this was
freshly refurbished motor,
we got good results
Example–6,6 kV Motor testing
Webinaron TanDelta Testingon RotativeMachines

48. 49
Bettermeasurecapacitanceand tandelta in the sametest
FROM THE FIELD…
Performtestsat nominalfrequencies (50 or 60 Hz),
youshouldawareof the inducedcurrents
thatcoulddecreasethe qualityof the measurements,
with impact on the finalresults.
Altanova SUGGEST…
Toperformoneor twotestsat ±2 or 3 Hz ofthe nominalfrequency, so toavoid
the inducedcurrentphenomenaabovementioned
How to execute the test
Webinaron TanDelta Testingon RotativeMachines

49. Example 3–6 kV 6925 kVAGeneratortesting
Tip Up and Tip Down test:0,68%
Usedmotorsin quitegood conditions
Tip Up
Tip Down
NOTE:
Tip up and tip down:
Givesindicationof
Inceptionand Extinction
of PartialDischarges
Webinaron TanDelta Testingon RotativeMachines

50. 1. PD are „micro sparks” that partially bridge the insulation
TD is more like overall statistical value of theinsulation’s conductivity
2. Tan Delta shows us the oveall state of the insulation
while PD is showing us if we have some issueshappening right now –at this moment
3. Seeing if something is happening right now,
we can correlate certain events with the behaviour ofinsulation
(switching or OLTC, overvoltages, near by faults…)
4. Continuous monitoring is the best solution for maintaining properly rotary machines
(it is particularly indicated for the very big generators)
5. TD sees well whole, PD permit you to discriminate by which part they are generated
Whyare TD and PD twosidesof the samestory
Webinaron TanDelta Testingon RotativeMachines

51. Thank you for your valuable attention
we hope you learned something new
J
Webinaron TanDelta Testingon RotativeMachines

52. https://www.altanova-group.com/en/regional-isa-offices/isa-regional-offices
https://www.altanova-group.com/en/local-distributors/local-distributors
MSc. Andrej Šepčić
RAM
[email protected]